ExTending the Input Voltage Range of Solar PV Inverters With Supercapacitor Energy Circulation
AUTHORS
Gunawardane, K., Bandara, N., Subasinghage, K. & Kularatna, N.
JOURNAL/CONFERENCE
Electronics (Switzerland) Vol 10, 88, 2021
ACCEPTED/PUBLISHED DATE
January 2021
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/10/1/88
ABSTRACT
Cleaner and greener energy sources have proliferated on a worldwide basis, creating distributed energy systems. Given the unreliable nature of the renewable sources such as solar and wind, they are traditionally based on inverters interfaced with legacy AC grid systems. While efficiency, output waveform quality and other technical specifications of inverters keep improving gradually, only limited attention is given to widening the input range of inverters. This paper presents a new supercapacitor assisted (SCA) technique to widen the input range of an inverter without modifying the inverter itself. Developing a prototype version of a 24 V DC input capable supercapacitor-assisted wide input (SCASWI) inverter using a supercapacitor circulation front end and a commercial 12 V DC line frequency inverter is detailed in the article, explaining how the SCASWI inverter technique doubles the input voltage while maintaining the useful characteristics of the commercial inverter. The new technique has the added advantage of DC-UPS capability based on a long-life supercapacitor module.
Gunawardane, K., Bandara, N., Subasinghage, K. & Kularatna, N.
JOURNAL/CONFERENCE
Electronics (Switzerland) Vol 10, 88, 2021
ACCEPTED/PUBLISHED DATE
January 2021
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/10/1/88
ABSTRACT
Cleaner and greener energy sources have proliferated on a worldwide basis, creating distributed energy systems. Given the unreliable nature of the renewable sources such as solar and wind, they are traditionally based on inverters interfaced with legacy AC grid systems. While efficiency, output waveform quality and other technical specifications of inverters keep improving gradually, only limited attention is given to widening the input range of inverters. This paper presents a new supercapacitor assisted (SCA) technique to widen the input range of an inverter without modifying the inverter itself. Developing a prototype version of a 24 V DC input capable supercapacitor-assisted wide input (SCASWI) inverter using a supercapacitor circulation front end and a commercial 12 V DC line frequency inverter is detailed in the article, explaining how the SCASWI inverter technique doubles the input voltage while maintaining the useful characteristics of the commercial inverter. The new technique has the added advantage of DC-UPS capability based on a long-life supercapacitor module.
Investigation of Progressing Low and Medium Voltage DC Standards to Acquire the Implementation Scenarios for Domestic/Commercial and Industrial Converters and Enabling Technologies
AUTHORS
Charlies Hua, K. Gunawardane and Professor Lie
JOURNAL/CONFERENCE
ACPEE 2021
ACCEPTED/PUBLISHED DATE
April 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9436850
ABSTRACT
"One major challenge in the context of the expanding research and developments of DC power and related technologies is the lack of well-developed and globally accepted standards for DC power distribution and equipment. This review investigates the fast-developing DC standards across the globe in the various stages of DC microgrids as well as their adaptability to New Zealand context to facilitate the future implementation scenarios of power electronic converters and other enabling technologies of Future Architecture of the Power System Network. A comprehensive literature survey is carried out collecting the latest relevant standards and related implementation scenarios for conveyance by DC at low and medium voltages for domestic/commercial and industrial
customers. Also, recommendations for DC standards to follow in New Zealand context for the Future Architecture of the Network are provided in this paper.
Charlies Hua, K. Gunawardane and Professor Lie
JOURNAL/CONFERENCE
ACPEE 2021
ACCEPTED/PUBLISHED DATE
April 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9436850
ABSTRACT
"One major challenge in the context of the expanding research and developments of DC power and related technologies is the lack of well-developed and globally accepted standards for DC power distribution and equipment. This review investigates the fast-developing DC standards across the globe in the various stages of DC microgrids as well as their adaptability to New Zealand context to facilitate the future implementation scenarios of power electronic converters and other enabling technologies of Future Architecture of the Power System Network. A comprehensive literature survey is carried out collecting the latest relevant standards and related implementation scenarios for conveyance by DC at low and medium voltages for domestic/commercial and industrial
customers. Also, recommendations for DC standards to follow in New Zealand context for the Future Architecture of the Network are provided in this paper.
Energy Storage Devices for Renewable Energy Systems
AUTHORS
Nihal Kularatna and Kosala Gunawardane
JOURNAL/CONFERENCE
[Book] Elsevier Academic Press, 2021, 428 pages
ACCEPTED/PUBLISHED DATE
May 2021
PUBLISHED LOCATION
https://www.sciencedirect.com/book/9780128207789/energy-storage-devices-for-renewable-energy-based-systems?via=ihub=
ABSTRACT
Energy Storage Devices for Renewable Energy-Based Systems: Rechargeable Batteries and Supercapacitors, Second Edition is a fully revised edition of this comprehensive overview of the concepts, principles and practical knowledge on energy storage devices. The book gives readers the opportunity to expand their knowledge of innovative supercapacitor applications, comparing them to other commonly used energy storage devices. With new application case studies and definitions, this resource will strengthen your understanding of energy storage from a practical, applications-based point-of-view without requiring detailed examination of underlying electrochemical equations. Users will learn about various design approaches and real-time applications of ESDs.
Electronic engineering experts and system designers will find this book useful to deepen their understanding on the application of electronic storage devices, circuit topologies, and industrial device data sheets to develop new applications. The book is also intended to be used as a textbook for masters and doctoral students who want to enhance their knowledge and understanding the concepts of renewable energy sources and state-of-the-art ESDs.
Nihal Kularatna and Kosala Gunawardane
JOURNAL/CONFERENCE
[Book] Elsevier Academic Press, 2021, 428 pages
ACCEPTED/PUBLISHED DATE
May 2021
PUBLISHED LOCATION
https://www.sciencedirect.com/book/9780128207789/energy-storage-devices-for-renewable-energy-based-systems?via=ihub=
ABSTRACT
Energy Storage Devices for Renewable Energy-Based Systems: Rechargeable Batteries and Supercapacitors, Second Edition is a fully revised edition of this comprehensive overview of the concepts, principles and practical knowledge on energy storage devices. The book gives readers the opportunity to expand their knowledge of innovative supercapacitor applications, comparing them to other commonly used energy storage devices. With new application case studies and definitions, this resource will strengthen your understanding of energy storage from a practical, applications-based point-of-view without requiring detailed examination of underlying electrochemical equations. Users will learn about various design approaches and real-time applications of ESDs.
Electronic engineering experts and system designers will find this book useful to deepen their understanding on the application of electronic storage devices, circuit topologies, and industrial device data sheets to develop new applications. The book is also intended to be used as a textbook for masters and doctoral students who want to enhance their knowledge and understanding the concepts of renewable energy sources and state-of-the-art ESDs.
Development of Supercapacitor Technology and Its Potential Impact on New Power Converter Techniques for Renewable Energy
AUTHORS
Ariyarathna, T., Kularatna, N., Gunawardane, K., Jayananda, D., Steyn-Ross, D.A.
JOURNAL/CONFERENCE
IEEE Journal of Emerging and Selected Topics in Industrial Electronics, Vol. 2, No. 3, July 2021, pp 267-276.
ACCEPTED/PUBLISHED DATE
July 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9362128
ABSTRACT
To overcome short-term input energy fluctuations, and to offer complete 24-h energy solutions based on renewable resources such as solar and wind, energy storage devices are mandatory. A relatively new storage family is the supercapacitor (SC), which were developing rapidly over the last 15 years, and are yet to compete with rechargeable batteries. Today with three different commercially available SC families developing rapidly, with 1-70 000 F per single cell, at least one of them is reaching the specific energy of lead-acid batteries. All new families of SCs have charge/discharge life cycles of several orders larger than rechargeable battery chemistries, and their usage in energy storage systems is rapidly advancing. The SC-assisted converters are a new family of very low-speed converters, where a power electronic building block is combined with an SC bank to achieve high end-to-end efficiency, with the added advantage of dc-uninterruptible power supply (UPS) capability within the converter. This article provides an overview of the new SC-assisted loss management theory applied to SC-assisted converters, with practical examples of implementation useful in renewable energy systems such as SC-assisted low dropout regulator, SC-assisted LED, SC-assisted server rack power architecture, and SC-assisted wide-input inverter. In developing these new converters, useful in renewable energy systems, SCs are considered as a new device family with five to six-order larger capacitance for the same canister size, helping the achievement of the long time constant circuits.
Ariyarathna, T., Kularatna, N., Gunawardane, K., Jayananda, D., Steyn-Ross, D.A.
JOURNAL/CONFERENCE
IEEE Journal of Emerging and Selected Topics in Industrial Electronics, Vol. 2, No. 3, July 2021, pp 267-276.
ACCEPTED/PUBLISHED DATE
July 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9362128
ABSTRACT
To overcome short-term input energy fluctuations, and to offer complete 24-h energy solutions based on renewable resources such as solar and wind, energy storage devices are mandatory. A relatively new storage family is the supercapacitor (SC), which were developing rapidly over the last 15 years, and are yet to compete with rechargeable batteries. Today with three different commercially available SC families developing rapidly, with 1-70 000 F per single cell, at least one of them is reaching the specific energy of lead-acid batteries. All new families of SCs have charge/discharge life cycles of several orders larger than rechargeable battery chemistries, and their usage in energy storage systems is rapidly advancing. The SC-assisted converters are a new family of very low-speed converters, where a power electronic building block is combined with an SC bank to achieve high end-to-end efficiency, with the added advantage of dc-uninterruptible power supply (UPS) capability within the converter. This article provides an overview of the new SC-assisted loss management theory applied to SC-assisted converters, with practical examples of implementation useful in renewable energy systems such as SC-assisted low dropout regulator, SC-assisted LED, SC-assisted server rack power architecture, and SC-assisted wide-input inverter. In developing these new converters, useful in renewable energy systems, SCs are considered as a new device family with five to six-order larger capacitance for the same canister size, helping the achievement of the long time constant circuits.
Supercapacitor-Assisted Techniques and Supercapacitor-Assisted Loss Management Concept: New Design Approaches to Change the Roadmap of Power Conversion Systems
AUTHORS
N. Kularatna, K. Subasinghage, K. Gunawardane, D. Jayananda, T. Ariyarathna
JOURNAL/CONFERENCE
Electronics (Swizerland) July 2021, Vol 10, 17 pages
ACCEPTED/PUBLISHED DATE
July 2021
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/10/14/1697
ABSTRACT
All electrical and electronic devices require access to a suitable energy source. In a portable electronic product, such as a cell phone, an energy storage unit drives a complex array of power conversion stages to generate multiple DC voltage rails required. To optimize the overall end-to-end efficiency, these internal power conversions should waste minimal energy and deliver more to the electronic modules. Capacitors are one of the main component families used in electronics, to store and deliver electric charges. Supercapacitors, so called because they provide over a million-fold increase in capacitance relative to a traditional capacitor of the same volume, are enabling a paradigm shift in the design of power electronic converter circuits. Here we show that supercapacitors could function as a lossless voltage-dropping element in the power conversion stages, thereby significantly increasing the power conversion stage efficiency. This approach has numerous secondary benefits: it improves continuity of the supply, suppresses voltage surges, allows the voltage regulation to be electromagnetically silent, and simplifies the design of voltage regulators. The use of supercapacitors allows the development of a novel loss-circumvention theory with applicability to a wide range of supercapacitor-assisted (SCA) techniques. These include low-dropout regulators, transient surge absorbers, LED lighting for DC microgrids, and rapid energy transfer for water heating.
N. Kularatna, K. Subasinghage, K. Gunawardane, D. Jayananda, T. Ariyarathna
JOURNAL/CONFERENCE
Electronics (Swizerland) July 2021, Vol 10, 17 pages
ACCEPTED/PUBLISHED DATE
July 2021
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/10/14/1697
ABSTRACT
All electrical and electronic devices require access to a suitable energy source. In a portable electronic product, such as a cell phone, an energy storage unit drives a complex array of power conversion stages to generate multiple DC voltage rails required. To optimize the overall end-to-end efficiency, these internal power conversions should waste minimal energy and deliver more to the electronic modules. Capacitors are one of the main component families used in electronics, to store and deliver electric charges. Supercapacitors, so called because they provide over a million-fold increase in capacitance relative to a traditional capacitor of the same volume, are enabling a paradigm shift in the design of power electronic converter circuits. Here we show that supercapacitors could function as a lossless voltage-dropping element in the power conversion stages, thereby significantly increasing the power conversion stage efficiency. This approach has numerous secondary benefits: it improves continuity of the supply, suppresses voltage surges, allows the voltage regulation to be electromagnetically silent, and simplifies the design of voltage regulators. The use of supercapacitors allows the development of a novel loss-circumvention theory with applicability to a wide range of supercapacitor-assisted (SCA) techniques. These include low-dropout regulators, transient surge absorbers, LED lighting for DC microgrids, and rapid energy transfer for water heating.
Scalable SCALDO Design for 48 V Google Server Racks Powered by 380 V DC-microgrids
AUTHORS
T. Ariyarathna, N. Kularatna and D. A. Steyn-Ross
JOURNAL/CONFERENCE
2021 IEEE Fourth International Conference on DC Microgrids (ICDCM), 2021, pp. 1-6
ACCEPTED/PUBLISHED DATE
July 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9504613
ABSTRACT
Supercapacitor assisted low dropout regulator (SCALDO) technique is a relatively new approach to design high-efficiency DC-DC converters, where a supercapacitor acts as a lossless voltage dropper in series with a linear low dropout regulator. This extra low frequency, radio frequency interference-free converter, with efficiencies similar to high-frequency switch-modes, could be extended to different applications, including dual rail power supplies. Leading data centre operators such as Google announced their intention to move toward 48 V server rack architecture to minimise power loss in distribution lines and to improve the overall operating efficiency. This paper shares our success in scaling SCALDO technique to develop power supply suitable for Google server rack powered by 380 V DC-microgrid.
T. Ariyarathna, N. Kularatna and D. A. Steyn-Ross
JOURNAL/CONFERENCE
2021 IEEE Fourth International Conference on DC Microgrids (ICDCM), 2021, pp. 1-6
ACCEPTED/PUBLISHED DATE
July 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9504613
ABSTRACT
Supercapacitor assisted low dropout regulator (SCALDO) technique is a relatively new approach to design high-efficiency DC-DC converters, where a supercapacitor acts as a lossless voltage dropper in series with a linear low dropout regulator. This extra low frequency, radio frequency interference-free converter, with efficiencies similar to high-frequency switch-modes, could be extended to different applications, including dual rail power supplies. Leading data centre operators such as Google announced their intention to move toward 48 V server rack architecture to minimise power loss in distribution lines and to improve the overall operating efficiency. This paper shares our success in scaling SCALDO technique to develop power supply suitable for Google server rack powered by 380 V DC-microgrid.
Architecture of the Future Low-Carbon, Resilient, Electrical Power System
AUTHOR
Radnya Mukhedkar
JOURNAL/CONFERENCE
2021 EAA Conference
ACCEPTED/PUBLISHED DATE
August 2021
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/eea-conference-2021.aspx
Radnya Mukhedkar
JOURNAL/CONFERENCE
2021 EAA Conference
ACCEPTED/PUBLISHED DATE
August 2021
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/eea-conference-2021.aspx
Representative Modelling of Very Long HVDC Cables
AUTHORS
Josh Schipper, Saijie Sim, Quy Dang, Radnya Mukhedkar
JOURNAL/CONFERENCE
IET AC DC Conference
ACCEPTED/PUBLISHED DATE
November 2021
PUBLISHED LOCATION
https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/rpg2.12734
ABSTRACT
A representative frequency dependent model (FDM) of an HVDC cable is important in ensuring HVDC systems are designed harmoniously. A model of the proposed and very long, 4200 km, AAPowerLink cables is implemented in PSCAD/EMTDC. The suitability of approximations required for efficient simulation are evaluated according to the anticipated cable specifications. In practice, a submarine cable of this length has between 40 to 80 field joints (FJ), which can be onerous to individually express and computationally expensive to model. Frequency domain analysis shows a minimum of 8 FJs is sufficient to represent the behaviour of the core voltage. The sensitivity of the FDM to cable parameters and operating conditions is assessed. The FDM is applied to establishing single ended fault location techniques. For a 4200 km cable these techniques can determine fault location to within 200 km (≈5%). Additional methods are explored to refine fault location estimates.
Josh Schipper, Saijie Sim, Quy Dang, Radnya Mukhedkar
JOURNAL/CONFERENCE
IET AC DC Conference
ACCEPTED/PUBLISHED DATE
November 2021
PUBLISHED LOCATION
https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/rpg2.12734
ABSTRACT
A representative frequency dependent model (FDM) of an HVDC cable is important in ensuring HVDC systems are designed harmoniously. A model of the proposed and very long, 4200 km, AAPowerLink cables is implemented in PSCAD/EMTDC. The suitability of approximations required for efficient simulation are evaluated according to the anticipated cable specifications. In practice, a submarine cable of this length has between 40 to 80 field joints (FJ), which can be onerous to individually express and computationally expensive to model. Frequency domain analysis shows a minimum of 8 FJs is sufficient to represent the behaviour of the core voltage. The sensitivity of the FDM to cable parameters and operating conditions is assessed. The FDM is applied to establishing single ended fault location techniques. For a 4200 km cable these techniques can determine fault location to within 200 km (≈5%). Additional methods are explored to refine fault location estimates.
Control Strategies of DC Microgrids Cluster: A Comprehensive Review
AUTHORS
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, Frede Blaabjerg
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
November 2021
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/14/22/7569
ABSTRACT
Multiple microgrids (MGs) close to each other can be interconnected to construct a cluster to enhance reliability and flexibility. This paper presents a comprehensive and comparative review of recent studies on DC MG clusters’ control strategies. Different schemes regarding the two significant control aspects of networked DC MGs, namely DC-link voltage control and power flow control between MGs, are investigated. A discussion about the architecture configuration of DC MG clusters is also provided. All advantages and limitations of various control strategies of recent studies are discussed in this paper. Furthermore, this paper discusses three types of consensus protocol with different time boundaries, including linear, finite, and fixed. Based on the main findings from the reviewed studies, future research recommendations are proposed.
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, Frede Blaabjerg
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
November 2021
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/14/22/7569
ABSTRACT
Multiple microgrids (MGs) close to each other can be interconnected to construct a cluster to enhance reliability and flexibility. This paper presents a comprehensive and comparative review of recent studies on DC MG clusters’ control strategies. Different schemes regarding the two significant control aspects of networked DC MGs, namely DC-link voltage control and power flow control between MGs, are investigated. A discussion about the architecture configuration of DC MG clusters is also provided. All advantages and limitations of various control strategies of recent studies are discussed in this paper. Furthermore, this paper discusses three types of consensus protocol with different time boundaries, including linear, finite, and fixed. Based on the main findings from the reviewed studies, future research recommendations are proposed.
Optimal Power Sharing in DC Microgrid Under Load and Generation Uncertainties Based on GWO Algorithm
AUTHORS
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, and Frede Blaabjerg
JOURNAL/CONFERENCE
IEEE PES ISGT ASIA 2021
ACCEPTED/PUBLISHED DATE
December 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9715662
ABSTRACT
Microgrids (MGs) are drawing growing attention due to their advantages in the distribution. Hierarchical control strategy including local and global layers has been employed in the MG. The local control layers of the DC MG are the focus in this study. These local control layers may face some problems under load disruptions and power generation variations. Therefore, this paper proposes to develop local control layers of the DC MG depending on Grey Wolf Optimizer (GWO) algorithm to overcome such issues. The simulation studies has been carried out and the main results indicate that the proposed control approach applied in the local layers has superior performance in terms of the voltage adjustment besides the power-exchange amongst PV, and battery accompanied by the supercapacitor as compared to that of the existing approaches.
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, and Frede Blaabjerg
JOURNAL/CONFERENCE
IEEE PES ISGT ASIA 2021
ACCEPTED/PUBLISHED DATE
December 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9715662
ABSTRACT
Microgrids (MGs) are drawing growing attention due to their advantages in the distribution. Hierarchical control strategy including local and global layers has been employed in the MG. The local control layers of the DC MG are the focus in this study. These local control layers may face some problems under load disruptions and power generation variations. Therefore, this paper proposes to develop local control layers of the DC MG depending on Grey Wolf Optimizer (GWO) algorithm to overcome such issues. The simulation studies has been carried out and the main results indicate that the proposed control approach applied in the local layers has superior performance in terms of the voltage adjustment besides the power-exchange amongst PV, and battery accompanied by the supercapacitor as compared to that of the existing approaches.
EMI issues in DC-Microgrids due to Power Electronic Converters
AUTHORS
A. R. Krishna, K. Gunawardane
JOURNAL/CONFERENCE
2021 IEEE Region 10 Conference (TENCON)
ACCEPTED/PUBLISHED DATE
December 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9707274
ABSTRACT
Energy experts and planners are focusing on the decarbonization of power systems as a potential solution to challenges currently faced by the grid operators, customers, and regulatory authorities. DC Microgrids are a secure, clean, green, and low carbon-option for applications in many rural and urban locations. Due their resilient, selfreliant, and robust nature, they are preferred against the AC grids. DC grids require fewer power converting stages relative to the AC grids, thereby reducing the AC-DC conversion losses. DC microgrids, unlike the AC microgrids, do not have to synchronize their generators and can provide connection of various types of distributed energy resources such as the PV panels and DC loads through their common DC bus. However, the DC Microgrids are usceptible to the EMI radiation due to the high switching operations of the DC-DC buck converters. This research provides an overview of the MATLAB/Simulink model of the DC microgrid system and presents key results from its simulation study undertaken to estimate the conducted Electromagnetic Interference arising from the interactions between the Buck converters. A standalone Low Voltage (LV) DC Microgrid model was built and simulated with and without the presence of EMI filters. Spectrum analysis was performed on the DCDC buck converter under both conditions which confirmed that the EMI filters are useful in reducing the EMI effects.
A. R. Krishna, K. Gunawardane
JOURNAL/CONFERENCE
2021 IEEE Region 10 Conference (TENCON)
ACCEPTED/PUBLISHED DATE
December 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=9707274
ABSTRACT
Energy experts and planners are focusing on the decarbonization of power systems as a potential solution to challenges currently faced by the grid operators, customers, and regulatory authorities. DC Microgrids are a secure, clean, green, and low carbon-option for applications in many rural and urban locations. Due their resilient, selfreliant, and robust nature, they are preferred against the AC grids. DC grids require fewer power converting stages relative to the AC grids, thereby reducing the AC-DC conversion losses. DC microgrids, unlike the AC microgrids, do not have to synchronize their generators and can provide connection of various types of distributed energy resources such as the PV panels and DC loads through their common DC bus. However, the DC Microgrids are usceptible to the EMI radiation due to the high switching operations of the DC-DC buck converters. This research provides an overview of the MATLAB/Simulink model of the DC microgrid system and presents key results from its simulation study undertaken to estimate the conducted Electromagnetic Interference arising from the interactions between the Buck converters. A standalone Low Voltage (LV) DC Microgrid model was built and simulated with and without the presence of EMI filters. Spectrum analysis was performed on the DCDC buck converter under both conditions which confirmed that the EMI filters are useful in reducing the EMI effects.
Mātauranga Māori in Power Engineering - Achieving sustainability and zero carbon futures with countries' indigenous knowledge in design
AUTHORS
F. MacConnell, R. Duggal, R. Rayudu, and N. -K. C. Nair
JOURNAL/CONFERENCE
2021 IEEE Region 10 Conference (TENCON)
ACCEPTED/PUBLISHED DATE
December 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9707384
ABSTRACT
Matauranga Māori is the knowledge of Māori in New Zealand. It can influence engineering by providing an alternative viewpoint and value system for consideration during initial planning and design such that projects are in line with the local sustainability goals. The goal of this research is to investigate and current and past works on Mātauranga Māori and how it can influence / interface with power engineering project design towards a carbon neutral and sustainable future. Currently there is no clear guidelines and interface, making conflict resolution between power companies and iwi challenging if a situation arises. If Māori ideas of spirituality and environmentalism can be quantified, communication between engineers / academics and iwi can be refined thereby making the design process more environmentally sustainable.
F. MacConnell, R. Duggal, R. Rayudu, and N. -K. C. Nair
JOURNAL/CONFERENCE
2021 IEEE Region 10 Conference (TENCON)
ACCEPTED/PUBLISHED DATE
December 2021
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9707384
ABSTRACT
Matauranga Māori is the knowledge of Māori in New Zealand. It can influence engineering by providing an alternative viewpoint and value system for consideration during initial planning and design such that projects are in line with the local sustainability goals. The goal of this research is to investigate and current and past works on Mātauranga Māori and how it can influence / interface with power engineering project design towards a carbon neutral and sustainable future. Currently there is no clear guidelines and interface, making conflict resolution between power companies and iwi challenging if a situation arises. If Māori ideas of spirituality and environmentalism can be quantified, communication between engineers / academics and iwi can be refined thereby making the design process more environmentally sustainable.
Supercapacitor-Assisted Low-Dropout Regulator Technique for Low Output Ripple DC–DC Conversion
AUTHORS
Subasinghage, K., Gunawardana, K. & Kularatna, N.
JOURNAL/CONFERENCE
IEEE Journal of Emerging and Selected Topics in Industrial Electronics, Vol. 3, No. 4, October 2022, pp 1028-1037.
ACCEPTED/PUBLISHED DATE
February 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9707662
ABSTRACT
Supercapacitor-assisted low dropout (SCALDO) regulator is an emerging technique to design high-efficiency dc–dc converters based on supercapacitor energy recovery method alongside a low dropout regulator. This very low frequency technique, having low electromagnetic compatibility issues, provides highefficiency operation applicable to a wide range of output currents varying from a few 100 mA cases with integrated circuit type LDOs to over 100 A cases in the high current discrete form of LDOs. The SCALDO regulator is not a variation of switched capacitor converters due to several definitive reasons. Based on a 12-5 V implementation, this article demonstrates how a SCALDO regulator keeps a very low voltage ripple at the connected dc load while achieving high end-to-end efficiency
Subasinghage, K., Gunawardana, K. & Kularatna, N.
JOURNAL/CONFERENCE
IEEE Journal of Emerging and Selected Topics in Industrial Electronics, Vol. 3, No. 4, October 2022, pp 1028-1037.
ACCEPTED/PUBLISHED DATE
February 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9707662
ABSTRACT
Supercapacitor-assisted low dropout (SCALDO) regulator is an emerging technique to design high-efficiency dc–dc converters based on supercapacitor energy recovery method alongside a low dropout regulator. This very low frequency technique, having low electromagnetic compatibility issues, provides highefficiency operation applicable to a wide range of output currents varying from a few 100 mA cases with integrated circuit type LDOs to over 100 A cases in the high current discrete form of LDOs. The SCALDO regulator is not a variation of switched capacitor converters due to several definitive reasons. Based on a 12-5 V implementation, this article demonstrates how a SCALDO regulator keeps a very low voltage ripple at the connected dc load while achieving high end-to-end efficiency
Optimal coordinated control strategy of Clustered DC microgrids under load-generation uncertainties based on GWO
AUTHORS
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, Frede Blaabjerg
JOURNAL/CONFERENCE
Electronics Journal
ACCEPTED/PUBLISHED DATE
April 2022
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/11/8/1244
ABSTRACT
The coordination of clustered microgrids (MGs) needs to be achieved in a seamless manner to tackle generation-load mismatch among MGs. A hierarchical control strategy based on PI controllers for local and global layers has been proposed in the literature to coordinate DC MGs in a cluster. However, this control strategy may not be able to resist significant load disturbances and unexpected generated powers due to the sporadic nature of the renewable energy resources. These issues are inevitable because both layers are highly dependent on PI controllers who cannot fully overcome the abovementioned obstacles. Therefore, Grey Wolf Optimizer (GWO) is proposed to enhance the performance of the global layer by optimizing its PI controller parameters. The simulation studies were conducted using the well-established MATLAB Simulink, and the results reveal that the optimized global layer performs better than the conventional ones. It is noticed that not only accurate power-sharing and proper voltage regulation within ±1% along with fewer power losses are achieved by adopting the modified consensus algorithm for the clustered DC MGs, but also the settling time and overshoot/undershoot are reduced even with the enormous load and generation changes which indicates the effectiveness of the proposed method used in the paper.
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, Frede Blaabjerg
JOURNAL/CONFERENCE
Electronics Journal
ACCEPTED/PUBLISHED DATE
April 2022
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/11/8/1244
ABSTRACT
The coordination of clustered microgrids (MGs) needs to be achieved in a seamless manner to tackle generation-load mismatch among MGs. A hierarchical control strategy based on PI controllers for local and global layers has been proposed in the literature to coordinate DC MGs in a cluster. However, this control strategy may not be able to resist significant load disturbances and unexpected generated powers due to the sporadic nature of the renewable energy resources. These issues are inevitable because both layers are highly dependent on PI controllers who cannot fully overcome the abovementioned obstacles. Therefore, Grey Wolf Optimizer (GWO) is proposed to enhance the performance of the global layer by optimizing its PI controller parameters. The simulation studies were conducted using the well-established MATLAB Simulink, and the results reveal that the optimized global layer performs better than the conventional ones. It is noticed that not only accurate power-sharing and proper voltage regulation within ±1% along with fewer power losses are achieved by adopting the modified consensus algorithm for the clustered DC MGs, but also the settling time and overshoot/undershoot are reduced even with the enormous load and generation changes which indicates the effectiveness of the proposed method used in the paper.
Current context and research trends in Linear DC-DC voltage regulators
AUTHORS
Kosala Gunawardane, Nisitha Padmawansa, Nihal Kularatna, Kasun Subasinghage, Tek Tjing Lie
JOURNAL/CONFERENCE
Applied Sciences Journal
ACCEPTED/PUBLISHED DATE
May 2022
PUBLISHED LOCATION
https://www.mdpi.com/2076-3417/12/9/4594
ABSTRACT
With the introduction of switch-mode power supplies (SMPS) in the mid-1970s, the efficiency of DC–DC conversion rose from 60 to 80% and SMPS became a popular power supply solution. However, linear regulators have not become obsolete. The modern power management system in portable devices supports a complex mix of DC–DC converters, combining switch-mode power supplies (SMPS), switched capacitor converters (SCCs), and linear regulators in the form of low-dropout regulators (LDOs). LDOs are used to supply low-voltage DC power rails with very low noise and high current slew rate capability, which are usually fed by the output rail of SMPS. This paper provides a comprehensive review of the evolution of the application scope of linear-type DC–DC converters in the power supply context and the present research trends. First, we review the context of linear DC–DC converters in detail, particularly in portable device power supplies. Then, the details of LDO regulators and their recent industry development and research trends are discussed. Then, the discussion focuses on supercapacitor-assisted low-dropout (SCALDO) regulator design and its scope in the portable device power management together with SCALDO-based dual output and reduced switch designs, and finally, the conclusions follow.
Kosala Gunawardane, Nisitha Padmawansa, Nihal Kularatna, Kasun Subasinghage, Tek Tjing Lie
JOURNAL/CONFERENCE
Applied Sciences Journal
ACCEPTED/PUBLISHED DATE
May 2022
PUBLISHED LOCATION
https://www.mdpi.com/2076-3417/12/9/4594
ABSTRACT
With the introduction of switch-mode power supplies (SMPS) in the mid-1970s, the efficiency of DC–DC conversion rose from 60 to 80% and SMPS became a popular power supply solution. However, linear regulators have not become obsolete. The modern power management system in portable devices supports a complex mix of DC–DC converters, combining switch-mode power supplies (SMPS), switched capacitor converters (SCCs), and linear regulators in the form of low-dropout regulators (LDOs). LDOs are used to supply low-voltage DC power rails with very low noise and high current slew rate capability, which are usually fed by the output rail of SMPS. This paper provides a comprehensive review of the evolution of the application scope of linear-type DC–DC converters in the power supply context and the present research trends. First, we review the context of linear DC–DC converters in detail, particularly in portable device power supplies. Then, the details of LDO regulators and their recent industry development and research trends are discussed. Then, the discussion focuses on supercapacitor-assisted low-dropout (SCALDO) regulator design and its scope in the portable device power management together with SCALDO-based dual output and reduced switch designs, and finally, the conclusions follow.
Optimal Coordinated Control of DC Microgrid Based on Hybrid PSO–GWO Algorithm
AUTHORS
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, Frede Blaabjerg
JOURNAL/CONFERENCE
Electricity Journal
ACCEPTED/PUBLISHED DATE
August 2022
PUBLISHED LOCATION
https://www.mdpi.com/2673-4826/3/3/19
ABSTRACT
Microgrids (MGs) are capable of playing an important role in the future of intelligent energy systems. This can be achieved by allowing the effective and seamless integration of distributed energy resources (DERs) loads, besides energy-storage systems (ESS) in the local area, so they are gaining attraction worldwide. In this regard, a DC MG is an economical, flexible, and dependable solution requiring a trustworthy control structure such as a hierarchical control strategy to be appropriately coordinated and used to electrify remote areas. Two control layers are involved in the hierarchy control strategy, including local- and global-control levels. However, this research focuses mainly on the issues of DC MG’s local control layer under various load interruptions and power-production fluctuations, including inaccurate power-sharing among sources and unregulated DC-bus voltage of the microgrid, along with a high ripple of battery current. Therefore, this work suggests developing local control levels for the DC MG based on the hybrid particle swarm optimization/grey wolf optimizer (HPSO–GWO) algorithm to address these problems. The key results of the simulation studies reveal that the proposed control scheme has achieved significant improvement in terms of voltage adjustment and power distribution between photovoltaic (PV) and battery technologies accompanied by a supercapacitor, in comparison to the existing control scheme. Moreover, the settling time and overshoot/undershoot are minimized despite the tremendous load and generation variations, which proves the proposed method’s efficiency.
Zaid Hamid Abdulabbas Al-Tameemi, Tek Tjing Lie, Gilbert Foo, Frede Blaabjerg
JOURNAL/CONFERENCE
Electricity Journal
ACCEPTED/PUBLISHED DATE
August 2022
PUBLISHED LOCATION
https://www.mdpi.com/2673-4826/3/3/19
ABSTRACT
Microgrids (MGs) are capable of playing an important role in the future of intelligent energy systems. This can be achieved by allowing the effective and seamless integration of distributed energy resources (DERs) loads, besides energy-storage systems (ESS) in the local area, so they are gaining attraction worldwide. In this regard, a DC MG is an economical, flexible, and dependable solution requiring a trustworthy control structure such as a hierarchical control strategy to be appropriately coordinated and used to electrify remote areas. Two control layers are involved in the hierarchy control strategy, including local- and global-control levels. However, this research focuses mainly on the issues of DC MG’s local control layer under various load interruptions and power-production fluctuations, including inaccurate power-sharing among sources and unregulated DC-bus voltage of the microgrid, along with a high ripple of battery current. Therefore, this work suggests developing local control levels for the DC MG based on the hybrid particle swarm optimization/grey wolf optimizer (HPSO–GWO) algorithm to address these problems. The key results of the simulation studies reveal that the proposed control scheme has achieved significant improvement in terms of voltage adjustment and power distribution between photovoltaic (PV) and battery technologies accompanied by a supercapacitor, in comparison to the existing control scheme. Moreover, the settling time and overshoot/undershoot are minimized despite the tremendous load and generation variations, which proves the proposed method’s efficiency.
MULTIPLE INITIAL POINT APPROACH TO SOLVING POWER FLOWS FOR Monte Carlo STUDIES
AUTHORS
Josh Schipper, Sharee McNab, Yuyin Kueh, Radnya Mukhedkar
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
September 2022
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/15/19/7141
ABSTRACT
Power flow solvers typically start from an initial point of power injection. This paper constructs a system of multiple initial points (SMIP) to enable selection of an appropriate initial point, with the objective to achieve a balanced improvement in the solution speed and accuracy, for problems with a large number of power flows. The intent is to recover time cost of forming the SMIP through the improvements to each power flow. The SMIP is tested on a time series based Monte Carlo study of Electric Vehicle (EV) hosting capacity in a low voltage distribution network, which has 5.4 million power flows. SMIP is applied to two power flow solvers: a Taylor series approximation and a Z-bus method. The accuracy of the quadratic Taylor series approximation was improved by a factor of 30 with a 27% increase in the solve time when compared against a single no-load initial point. A Z-bus solver with SMIP, limited to two iterations, gave the best performance for the EV hosting capacity case study
Josh Schipper, Sharee McNab, Yuyin Kueh, Radnya Mukhedkar
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
September 2022
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/15/19/7141
ABSTRACT
Power flow solvers typically start from an initial point of power injection. This paper constructs a system of multiple initial points (SMIP) to enable selection of an appropriate initial point, with the objective to achieve a balanced improvement in the solution speed and accuracy, for problems with a large number of power flows. The intent is to recover time cost of forming the SMIP through the improvements to each power flow. The SMIP is tested on a time series based Monte Carlo study of Electric Vehicle (EV) hosting capacity in a low voltage distribution network, which has 5.4 million power flows. SMIP is applied to two power flow solvers: a Taylor series approximation and a Z-bus method. The accuracy of the quadratic Taylor series approximation was improved by a factor of 30 with a 27% increase in the solve time when compared against a single no-load initial point. A Z-bus solver with SMIP, limited to two iterations, gave the best performance for the EV hosting capacity case study
Modern Supercapacitors Technologies and Their Applicability in Mature Electrical Engineering Applications
AUTHORS
Kasun Subasinghage, Kosala Gunawardane, Nisitha Padmawansa, Nihal Kularatna, Mehdi Moradian
JOURNAL/CONFERENCE
Energies Journal
ACCEPTED/PUBLISHED DATE
October 2022
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/15/20/7752
ABSTRACT
Supercapacitors can store a million times more energy per unit mass or volume compared to electrolytic capacitors. Due to their low internal resistance, they are capable of driving or absorbing pulsative high currents. Over the last quarter, century supercapacitor (SC) manufacturers have developed several families of mass-scale devices with high-power density and a longer cycle life that helped the end-users to improve their energy storage systems and products. Today, there are three common device families, namely, (i) symmetrical double-layer capacitors (EDLCs), (ii) hybrid capacitors with a lithium electrode, and (iii) battery capacitors based on pseudo capacitance concepts. This review paper compares these families and provides an overview of several state-of-the-art applications in electric vehicles (EVs), microgrids, and consumer electronics.
Kasun Subasinghage, Kosala Gunawardane, Nisitha Padmawansa, Nihal Kularatna, Mehdi Moradian
JOURNAL/CONFERENCE
Energies Journal
ACCEPTED/PUBLISHED DATE
October 2022
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/15/20/7752
ABSTRACT
Supercapacitors can store a million times more energy per unit mass or volume compared to electrolytic capacitors. Due to their low internal resistance, they are capable of driving or absorbing pulsative high currents. Over the last quarter, century supercapacitor (SC) manufacturers have developed several families of mass-scale devices with high-power density and a longer cycle life that helped the end-users to improve their energy storage systems and products. Today, there are three common device families, namely, (i) symmetrical double-layer capacitors (EDLCs), (ii) hybrid capacitors with a lithium electrode, and (iii) battery capacitors based on pseudo capacitance concepts. This review paper compares these families and provides an overview of several state-of-the-art applications in electric vehicles (EVs), microgrids, and consumer electronics.
Supercapacitor based approaches for arc energy absorption in direct current circuit breakers
AUTHORS
Dassanayake, C. , Gunathilaka, R., Gurusinghe, N. & Kularatna, N.
JOURNAL/CONFERENCE
IEEE-IECON 2022, October 2022, Brussels
ACCEPTED/PUBLISHED DATE
October 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9968979
ABSTRACT
AC circuit breakers are a mature technology, and are based on an arc chamber coupled with inductive arc absorption circuitry developed using commercial off the shelf components. In developing these, two zero crossings per AC cycle is effectively used, with capacitors, MOVs and other components used at the switch contacts to absorb the inductive energy in the AC circuit loop. Given that a DC circuit loop does not provide current zero crossings, arc extinguishing is not supported. Hence, commercial DC breakers are modified versions of AC breakers, usually the contacts of a 3 phase breaker poles connected in series to share the arc energy, sometimes combined with other transient absorbing components. This paper presents a preliminary results of a new approach for DC circuit breakers based on placing a supercapacitor based energy absorption loop, making use of the high current capability and the significant joule rating of a supercapacitor.
Dassanayake, C. , Gunathilaka, R., Gurusinghe, N. & Kularatna, N.
JOURNAL/CONFERENCE
IEEE-IECON 2022, October 2022, Brussels
ACCEPTED/PUBLISHED DATE
October 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9968979
ABSTRACT
AC circuit breakers are a mature technology, and are based on an arc chamber coupled with inductive arc absorption circuitry developed using commercial off the shelf components. In developing these, two zero crossings per AC cycle is effectively used, with capacitors, MOVs and other components used at the switch contacts to absorb the inductive energy in the AC circuit loop. Given that a DC circuit loop does not provide current zero crossings, arc extinguishing is not supported. Hence, commercial DC breakers are modified versions of AC breakers, usually the contacts of a 3 phase breaker poles connected in series to share the arc energy, sometimes combined with other transient absorbing components. This paper presents a preliminary results of a new approach for DC circuit breakers based on placing a supercapacitor based energy absorption loop, making use of the high current capability and the significant joule rating of a supercapacitor.
DC Suitability of AC Appliances
AUTHORS
Soren Subritzky and Andrew Lapthorn
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990027
ABSTRACT
DC appliances are increasingly becoming commonplace with the advances in switch-mode power supplies and renewable energy systems. Current devices are designed to operate on 230 VAC. However, many of them include an AC/DC stage that incurs unnecessary losses. This paper investigates the power supply stages of several household appliances to determine their suitability to be supplied directly from a DC source. Three main categories of home appliances were analysed: Switch Mode Power Supplies (SMPS), resistive heaters, and lighting equipment. Devices containing SMPS and Variable Speed Drives (VSD) can operate on 325 VDC without any modification as most of their components are already rated for DC. Resistive heaters could work on 230 VDC with minor modifications as their contact switches, and Simmerstats are not rated for breaking mains equivalent DC currents. Appliances containing AC components such as phase control circuits, direct-on-line induction machines and step-up/down transformers would need significant modification to operate on DC as these appliances rely on an AC supply to operate.
Soren Subritzky and Andrew Lapthorn
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990027
ABSTRACT
DC appliances are increasingly becoming commonplace with the advances in switch-mode power supplies and renewable energy systems. Current devices are designed to operate on 230 VAC. However, many of them include an AC/DC stage that incurs unnecessary losses. This paper investigates the power supply stages of several household appliances to determine their suitability to be supplied directly from a DC source. Three main categories of home appliances were analysed: Switch Mode Power Supplies (SMPS), resistive heaters, and lighting equipment. Devices containing SMPS and Variable Speed Drives (VSD) can operate on 325 VDC without any modification as most of their components are already rated for DC. Resistive heaters could work on 230 VDC with minor modifications as their contact switches, and Simmerstats are not rated for breaking mains equivalent DC currents. Appliances containing AC components such as phase control circuits, direct-on-line induction machines and step-up/down transformers would need significant modification to operate on DC as these appliances rely on an AC supply to operate.
Investigation of Geomagnetically Induced Currents (GICs) Susceptibility of Different Three-Phase Power Transformer Cores
AUTHORS
Xin Yi Teh, Yingzhen Xue, Zijian Liang, Joseph Ramirez and Andrew Lapthorn
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID) / November 2022
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990010
ABSTRACT
This paper investigates the susceptibility of different three-phase power transformer cores against Geomagnetically Induced Current (GICs). GIC, which is a quasi-DC current induced in the grid due to extreme space weather, will saturate power transformers due to half-cycle saturation caused by zero sequence fluxes. 15kVA small-scale three-phase three-limb, three-phase five-limb, and three single-phase transformers were designed and built. Then, the transformers were simulated using PSCAD/EMTDC to obtain the current and voltage waveforms under GIC. After that, the transformers underwent normal AC load testing at 25%, 50%, 75% and 100% load. This provides a temperature curve and waveforms comparison with the results under GIC conditions, which is modelled as DC injection on the secondary neutral point of the transformer. Lastly, the DC injection test was conducted. The temperature of the transformers increases during DC injection as the total circulating current in the transformers increases. Even harmonics enhancement and increase in reactive power demand are also observed due to transformers saturation under GIC. The results align with the zero-sequence flux theory and simulation waveforms, which suggest that the three single-phase transformers are the most susceptible to GIC, followed by the three-phase five-limb and the three-phase three-limb transformers.
Xin Yi Teh, Yingzhen Xue, Zijian Liang, Joseph Ramirez and Andrew Lapthorn
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID) / November 2022
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990010
ABSTRACT
This paper investigates the susceptibility of different three-phase power transformer cores against Geomagnetically Induced Current (GICs). GIC, which is a quasi-DC current induced in the grid due to extreme space weather, will saturate power transformers due to half-cycle saturation caused by zero sequence fluxes. 15kVA small-scale three-phase three-limb, three-phase five-limb, and three single-phase transformers were designed and built. Then, the transformers were simulated using PSCAD/EMTDC to obtain the current and voltage waveforms under GIC. After that, the transformers underwent normal AC load testing at 25%, 50%, 75% and 100% load. This provides a temperature curve and waveforms comparison with the results under GIC conditions, which is modelled as DC injection on the secondary neutral point of the transformer. Lastly, the DC injection test was conducted. The temperature of the transformers increases during DC injection as the total circulating current in the transformers increases. Even harmonics enhancement and increase in reactive power demand are also observed due to transformers saturation under GIC. The results align with the zero-sequence flux theory and simulation waveforms, which suggest that the three single-phase transformers are the most susceptible to GIC, followed by the three-phase five-limb and the three-phase three-limb transformers.
Comparison of Low-Voltage AC and DC Distribution Networks for EV Charging
AUTHORS
Wayne Huynh, Tran The Hoang, Abhisek Ukil, and Nirmal Nair
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990014
ABSTRACT
The increasing penetration of electric vehicles (EVs) in current and future transport fleets imposes significant loading on the existing power grids. Moreover, dc is experiencing renewed interest with rapid growth in electronic loads, the move towards renewable energy sources (RES) and distributed generation, and advances in power electronics technology. The next generation ‘Smart Grids’ need to consider these trends. As a component of the smart grids, low voltage dc (LVDC) distribution has been widely proposed to efficiently enable these changes. This work investigates LVDC for EV charging at residential, commercial and public charging station levels. Load profiles for EV charging are developed and used together with a model LVDC system to compare its performance to a conventional ac system.
Wayne Huynh, Tran The Hoang, Abhisek Ukil, and Nirmal Nair
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990014
ABSTRACT
The increasing penetration of electric vehicles (EVs) in current and future transport fleets imposes significant loading on the existing power grids. Moreover, dc is experiencing renewed interest with rapid growth in electronic loads, the move towards renewable energy sources (RES) and distributed generation, and advances in power electronics technology. The next generation ‘Smart Grids’ need to consider these trends. As a component of the smart grids, low voltage dc (LVDC) distribution has been widely proposed to efficiently enable these changes. This work investigates LVDC for EV charging at residential, commercial and public charging station levels. Load profiles for EV charging are developed and used together with a model LVDC system to compare its performance to a conventional ac system.
Multilayer Networks Framework Concept applied to Hybrid MV AC/DC Network Topologies
AUTHORS
André N Cuppen, Tran The Hoang, Nirmal Nair, Abhisek Ukil
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990017
ABSTRACT
The increasing growth of DC grids in medium voltage AC networks and their interconnections is expected to become a challenge in modelling that exceeds the tools available today. As opposed to mature developed three-phase AC network topologies spanning from generation, transmission, to distribution, the integration of DC technologies into existing AC networks will create various configurations of hybrid AC/DC networks that can create difficulty for network modelling and operation. Multilayer networks frameworks are a promising tool to enable scholars and engineers alike to understand and manage the hybrid AC/DC networks of the future. This paper aims at adopting the general concept of multilayer networks for systematically describing various topologies of hybrid AC/DC networks in terms of the formalized dictionary of terminology. We describe hybrid AC/DC networks in terms of the formalized dictionary of terminology. Finally, several examples are given; from the simplest, to the common industry reviewed AC/DC benchmark model. Several examples are given ranging from the simplest, to the common industry reviewed AC/DC benchmark model.
André N Cuppen, Tran The Hoang, Nirmal Nair, Abhisek Ukil
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990017
ABSTRACT
The increasing growth of DC grids in medium voltage AC networks and their interconnections is expected to become a challenge in modelling that exceeds the tools available today. As opposed to mature developed three-phase AC network topologies spanning from generation, transmission, to distribution, the integration of DC technologies into existing AC networks will create various configurations of hybrid AC/DC networks that can create difficulty for network modelling and operation. Multilayer networks frameworks are a promising tool to enable scholars and engineers alike to understand and manage the hybrid AC/DC networks of the future. This paper aims at adopting the general concept of multilayer networks for systematically describing various topologies of hybrid AC/DC networks in terms of the formalized dictionary of terminology. We describe hybrid AC/DC networks in terms of the formalized dictionary of terminology. Finally, several examples are given; from the simplest, to the common industry reviewed AC/DC benchmark model. Several examples are given ranging from the simplest, to the common industry reviewed AC/DC benchmark model.
Tripping Sequence Approach to Reduce Fault Current to be Interrupted in LVDC Microgrids
AUTHORS
Sze Nin Yim, Tran The Hoang, Nirmal Nair, and Abhisek Ukil
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990022
ABSTRACT
With the increasing use of solar energy, DC Microgrid with lower capacities are formed with connection to the traditional main grid. If a short circuit fault occurs in DC microgrids, the contribution of multiple sources including main grid and DC sources might lead to very high fault levels that are difficult to break. While technologies for manufacturing the DC circuit breaker with higher breaking capacity are on-going, another approach by changing tripping sequences in DC protection systems, which could reduce fault currents to be interrupted by a single circuit breaker, was studied in this paper. With the aid of MATLAB/Simulink and OPAL-RT 5700 real time simulation, effectiveness of the proposed approach was evaluated on a Simulink stimulation model of 500 V, 1 MW grid-connected DC Microgrid. The result obtained indicated that the fault current level interrupted by the DC circuit breakers was reduced by up to 63%.
Sze Nin Yim, Tran The Hoang, Nirmal Nair, and Abhisek Ukil
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990022
ABSTRACT
With the increasing use of solar energy, DC Microgrid with lower capacities are formed with connection to the traditional main grid. If a short circuit fault occurs in DC microgrids, the contribution of multiple sources including main grid and DC sources might lead to very high fault levels that are difficult to break. While technologies for manufacturing the DC circuit breaker with higher breaking capacity are on-going, another approach by changing tripping sequences in DC protection systems, which could reduce fault currents to be interrupted by a single circuit breaker, was studied in this paper. With the aid of MATLAB/Simulink and OPAL-RT 5700 real time simulation, effectiveness of the proposed approach was evaluated on a Simulink stimulation model of 500 V, 1 MW grid-connected DC Microgrid. The result obtained indicated that the fault current level interrupted by the DC circuit breakers was reduced by up to 63%.
Enhanced Grid-tie Converter Control Under Unbalanced Conditions with no PLL
AUTHORS
Hailong Wang, Yonghe Liu, Neville Watson
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990009/
ABSTRACT
The ubiquitous Phase-locked loop (PLL) is used to synchronise power converters with the AC system. The limitations of the PLL when the AC system is weak are well known. This paper investigates the modelling and control of Grid-Side Voltage Source Converter (GS-VSC) of a wind-turbine under unbalanced network conditions and connected to a weak system. The proposed control scheme regulates the instantaneous active and reactive power at the PCC. The operation of the GS-VSC under unbalanced voltage condition is analysed and the concept of using different control target is present, which is independent of a PLL. A new current control scheme comprising of a central controller and a compensation controller is proposed. Simulation results using PSCAD/EMTDC are presented to validate the effectiveness of the proposed control scheme and to demonstrate the operation under unbalanced network conditions in a weak grid.
Hailong Wang, Yonghe Liu, Neville Watson
JOURNAL/CONFERENCE
2022 7th IEEE Workshop on the Electronic Grid (eGRID)
ACCEPTED/PUBLISHED DATE
November 2022
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/9990009/
ABSTRACT
The ubiquitous Phase-locked loop (PLL) is used to synchronise power converters with the AC system. The limitations of the PLL when the AC system is weak are well known. This paper investigates the modelling and control of Grid-Side Voltage Source Converter (GS-VSC) of a wind-turbine under unbalanced network conditions and connected to a weak system. The proposed control scheme regulates the instantaneous active and reactive power at the PCC. The operation of the GS-VSC under unbalanced voltage condition is analysed and the concept of using different control target is present, which is independent of a PLL. A new current control scheme comprising of a central controller and a compensation controller is proposed. Simulation results using PSCAD/EMTDC are presented to validate the effectiveness of the proposed control scheme and to demonstrate the operation under unbalanced network conditions in a weak grid.
AC and DC House Wiring Efficiency Estimations Using a Fast Extensive Measurements Approach
AUTHORS
J A Qureshi, T T Lie, K. Gunawardane, N. Kularatna
JOURNAL/CONFERENCE
Modern Sciences Journal Vol. 12(1), 2023 / March 2023
ACCEPTED/PUBLISHED DATE
March 2023
PUBLISHED LOCATION
https://journals.modernsciences.org/index.php/msj/article/view/26
ABSTRACT
DC-based appliances are exponentially increasing in the present market. This scenario opens the opportunity to utilize the DC electricity produced by the PV panels directly without going through the conversion stages. Due to high penetration of DC electricity sources, it is timely to utilize DC electricity directly. Several research works have been reported in the literature to experimentally test and compare AC and DC wiring options. Accurate and precise experimental measurements are vital to establish a sound theoretical basis. However, this is difficult due to cost and time constraints. Therefore, to avoid costly measurements, this paper develops a mathematical model based on measurements on selected AC and DC wiring at four voltage levels (12 V DC, 24 V DC, 48 V DC, and 230 V AC). A digital simulation calibration using DigSilent is conducted to validate the proposed mathematical model. This paper proposed to utilize the simulation calibration approach that is a cost-effective and timesaving option to perform extensive measurements accurately.
J A Qureshi, T T Lie, K. Gunawardane, N. Kularatna
JOURNAL/CONFERENCE
Modern Sciences Journal Vol. 12(1), 2023 / March 2023
ACCEPTED/PUBLISHED DATE
March 2023
PUBLISHED LOCATION
https://journals.modernsciences.org/index.php/msj/article/view/26
ABSTRACT
DC-based appliances are exponentially increasing in the present market. This scenario opens the opportunity to utilize the DC electricity produced by the PV panels directly without going through the conversion stages. Due to high penetration of DC electricity sources, it is timely to utilize DC electricity directly. Several research works have been reported in the literature to experimentally test and compare AC and DC wiring options. Accurate and precise experimental measurements are vital to establish a sound theoretical basis. However, this is difficult due to cost and time constraints. Therefore, to avoid costly measurements, this paper develops a mathematical model based on measurements on selected AC and DC wiring at four voltage levels (12 V DC, 24 V DC, 48 V DC, and 230 V AC). A digital simulation calibration using DigSilent is conducted to validate the proposed mathematical model. This paper proposed to utilize the simulation calibration approach that is a cost-effective and timesaving option to perform extensive measurements accurately.
Supercapacitor assisted extra low frequency power converters and surge protectors: Applying Supercapacitor Assisted Loss Management Concept in practical applications
AUTHORS
Ariyarathna, T, Kularatna, N. & Gunawardane, K.
JOURNAL/CONFERENCE
IEEE- Applied Power Electronics Conference, March 2023, Orlando, USA
ACCEPTED/PUBLISHED DATE
March 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10131267
ABSTRACT
Traditionally, supercapacitors are used as energy storage devices, replacing or hybridizing with batteries. Typical applications include UPS, power quality enhancers, automotive, electric vehicles and portable devices. However, if a super-capacitor is treated as a device with a million times higher capacitance, they can be used in different application domains, such as high-efficiency linear DC-DC converters, surge absorbers, LED lighting systems and inverters with completely new design approaches. These supercapacitor-assisted (SCA) techniques use the two essential properties of an ideal supercapacitor, (i) very long time constant and/or (ii) performances as lossless voltage droppers. This paper presents a summary of Supercapacitor Assisted Loss Management (SCALoM), as the underlying basis for high-efficiency converters and protection systems, such as the SCA low dropout (SCALDO) regulator, SCA surge absorber (SCASA) and others. An important property of SCALDO is high efficiency at a very low frequency with DC-UPS capability. SCASA is a high-performance surge absorber with less component count than traditional protectors and with higher endurance to repeated high surges, adhering to UL 1449 (3rd Edition) test procedure. The paper will also show how SCALoM concept could be generally used in converters useful in renewable energy systems. Index Terms—Efficiency, Google, Magnetics, SCALDO, super-capacitors, 48 V DC rails
Ariyarathna, T, Kularatna, N. & Gunawardane, K.
JOURNAL/CONFERENCE
IEEE- Applied Power Electronics Conference, March 2023, Orlando, USA
ACCEPTED/PUBLISHED DATE
March 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10131267
ABSTRACT
Traditionally, supercapacitors are used as energy storage devices, replacing or hybridizing with batteries. Typical applications include UPS, power quality enhancers, automotive, electric vehicles and portable devices. However, if a super-capacitor is treated as a device with a million times higher capacitance, they can be used in different application domains, such as high-efficiency linear DC-DC converters, surge absorbers, LED lighting systems and inverters with completely new design approaches. These supercapacitor-assisted (SCA) techniques use the two essential properties of an ideal supercapacitor, (i) very long time constant and/or (ii) performances as lossless voltage droppers. This paper presents a summary of Supercapacitor Assisted Loss Management (SCALoM), as the underlying basis for high-efficiency converters and protection systems, such as the SCA low dropout (SCALDO) regulator, SCA surge absorber (SCASA) and others. An important property of SCALDO is high efficiency at a very low frequency with DC-UPS capability. SCASA is a high-performance surge absorber with less component count than traditional protectors and with higher endurance to repeated high surges, adhering to UL 1449 (3rd Edition) test procedure. The paper will also show how SCALoM concept could be generally used in converters useful in renewable energy systems. Index Terms—Efficiency, Google, Magnetics, SCALDO, super-capacitors, 48 V DC rails
Representative modelling of very long HVDC cables
AUTHORS
Josh Schipper, Saijie Sim, Quy Dang, Radnya Mukhedkar
JOURNAL/CONFERENCE
IET Renewable Power Generation / April 2023
ACCEPTED/PUBLISHED DATE
April 2023
PUBLISHED LOCATION
https://ietresearch.onlinelibrary.wiley.com/doi/full/10.1049/rpg2.12734
ABSTRACT
A representative frequency dependent model (FDM) of an HVDC cable is important in ensuring HVDC systems are designed harmoniously. A model of the proposed and very long, 4,200 km, AAPowerLink cables is implemented in PSCAD/EMTDC. The suitability of approximations required for efficient simulation are evaluated according to the anticipated cable specifications. In practice, a submarine cable of this length has between 40 to 80 field joints (FJ), which can be onerous to individually express and computationally expensive to model. Frequency domain analysis shows a minimum of 8 FJs is sufficient to represent the behaviour of the core voltage. The sensitivity of the FDM to cable parameters and operating conditions is assessed. The FDM is applied to establishing single ended fault location techniques. For a 4,200 km cable these techniques can determine fault location to within 200 km (~5%). Additional methods are explored to refine fault location estimates.
Josh Schipper, Saijie Sim, Quy Dang, Radnya Mukhedkar
JOURNAL/CONFERENCE
IET Renewable Power Generation / April 2023
ACCEPTED/PUBLISHED DATE
April 2023
PUBLISHED LOCATION
https://ietresearch.onlinelibrary.wiley.com/doi/full/10.1049/rpg2.12734
ABSTRACT
A representative frequency dependent model (FDM) of an HVDC cable is important in ensuring HVDC systems are designed harmoniously. A model of the proposed and very long, 4,200 km, AAPowerLink cables is implemented in PSCAD/EMTDC. The suitability of approximations required for efficient simulation are evaluated according to the anticipated cable specifications. In practice, a submarine cable of this length has between 40 to 80 field joints (FJ), which can be onerous to individually express and computationally expensive to model. Frequency domain analysis shows a minimum of 8 FJs is sufficient to represent the behaviour of the core voltage. The sensitivity of the FDM to cable parameters and operating conditions is assessed. The FDM is applied to establishing single ended fault location techniques. For a 4,200 km cable these techniques can determine fault location to within 200 km (~5%). Additional methods are explored to refine fault location estimates.
A Lyapunov-Based Nonlinear Direct Power Control for Grid-Side Converters Interfacing Renewable Energy in Weak Grids
AUTHORS
H. Wang, J.D. Watson, N.R. Watson
JOURNAL/CONFERENCE
Electric Power Systems Research / April 2023
ACCEPTED/PUBLISHED DATE
April 2023
PUBLISHED LOCATION
https://www.sciencedirect.com/science/article/pii/S0378779623002973
ABSTRACT
This paper presents a nonlinear direct power control (DPC) strategy for grid-connected voltage source converters based on adopting instantaneous active and reactive power as dynamic variables. A general uniform expression with the instantaneous magnitude and phase for arbitrary three-phase signals has been established in this paper. The proposed model gives instantaneous relationships between the variables and no restrictions are imposed on the voltage or current waveform, i.e. the model is valid in the entire state space. A higher control layer, i.e., the power plant centralized controller, generates the reactive power command to support the point of common coupling voltage. A dynamic current limitation mechanism is included to protect the converter during grid faults. The stability of the control system is analyzed via the Lyapunov theory, and the system states are proven to converge to the desired equilibrium point asymptotically. Simulation results using PSCAD/EMTDC demonstrate that the grid-side converter using the proposed DPC approach has a fast response (less than 40ms) along with very small power variation even with low SCR and is demonstrably superior to the latest DPC scheme in the literature under various grid conditions.
H. Wang, J.D. Watson, N.R. Watson
JOURNAL/CONFERENCE
Electric Power Systems Research / April 2023
ACCEPTED/PUBLISHED DATE
April 2023
PUBLISHED LOCATION
https://www.sciencedirect.com/science/article/pii/S0378779623002973
ABSTRACT
This paper presents a nonlinear direct power control (DPC) strategy for grid-connected voltage source converters based on adopting instantaneous active and reactive power as dynamic variables. A general uniform expression with the instantaneous magnitude and phase for arbitrary three-phase signals has been established in this paper. The proposed model gives instantaneous relationships between the variables and no restrictions are imposed on the voltage or current waveform, i.e. the model is valid in the entire state space. A higher control layer, i.e., the power plant centralized controller, generates the reactive power command to support the point of common coupling voltage. A dynamic current limitation mechanism is included to protect the converter during grid faults. The stability of the control system is analyzed via the Lyapunov theory, and the system states are proven to converge to the desired equilibrium point asymptotically. Simulation results using PSCAD/EMTDC demonstrate that the grid-side converter using the proposed DPC approach has a fast response (less than 40ms) along with very small power variation even with low SCR and is demonstrably superior to the latest DPC scheme in the literature under various grid conditions.
Topology Comparative Assessment for Hybrid Medium-Voltage AC/DC Networks
AUTHORS
Eric Sierra Jimenez, Tran The Hoang, PhD, Andre N. Cuppen, Nirmal Nair, PhD, Abhisek Ukil, PhD
JOURNAL/CONFERENCE
Electric Power Systems Research Journal / May 2023
ACCEPTED/PUBLISHED DATE
May 2023
PUBLISHED LOCATION
https://www.sciencedirect.com/science/article/pii/S0378779623003802
ABSTRACT
Recently, there has been significant growth in integrating renewable energy generation and electric vehicles and deploying new technologies into the electrical networks, leading to new challenges for planning, design, operation, control and protection of the distribution grid. In particular, an increasing amount of large-scale DC load and generation is expected to be connected to the distribution system, especially at the MV level. Thus, adoption of new grid topologies is required and among others, hybrid AC/DC networks have emerged as an attractive pathway to meet new grid operational requirements. This paper evaluates future hybrid AC/DC distribution systems at the MV level, considering potential network topologies and new technologies. Steady-state analysis is performed to compare five topologies of hybrid MV AC/DC networks. Key technologies for such hybrid grids such as voltage source converters and fast charging stations are considered. The results provide quantitative comparisons between topologies regarding large-scale DC load and generation integration capability, contingency operation, sensitivity analysis. Several challenges presented to the protection and fault location that are caused by the adoption of new topologies are also identified. The topologies are compared by network losses, voltage and power factor constraints, analysing the different benefits and drawbacks of the hybrid AC/DC topologies.
Eric Sierra Jimenez, Tran The Hoang, PhD, Andre N. Cuppen, Nirmal Nair, PhD, Abhisek Ukil, PhD
JOURNAL/CONFERENCE
Electric Power Systems Research Journal / May 2023
ACCEPTED/PUBLISHED DATE
May 2023
PUBLISHED LOCATION
https://www.sciencedirect.com/science/article/pii/S0378779623003802
ABSTRACT
Recently, there has been significant growth in integrating renewable energy generation and electric vehicles and deploying new technologies into the electrical networks, leading to new challenges for planning, design, operation, control and protection of the distribution grid. In particular, an increasing amount of large-scale DC load and generation is expected to be connected to the distribution system, especially at the MV level. Thus, adoption of new grid topologies is required and among others, hybrid AC/DC networks have emerged as an attractive pathway to meet new grid operational requirements. This paper evaluates future hybrid AC/DC distribution systems at the MV level, considering potential network topologies and new technologies. Steady-state analysis is performed to compare five topologies of hybrid MV AC/DC networks. Key technologies for such hybrid grids such as voltage source converters and fast charging stations are considered. The results provide quantitative comparisons between topologies regarding large-scale DC load and generation integration capability, contingency operation, sensitivity analysis. Several challenges presented to the protection and fault location that are caused by the adoption of new topologies are also identified. The topologies are compared by network losses, voltage and power factor constraints, analysing the different benefits and drawbacks of the hybrid AC/DC topologies.
Electrical Performance of Current Commercial Supercapacitors and Their Future Applications
AUTHORS
Sirimanne, D.C.U., Kularatna, N., Arawwawala, N.
JOURNAL/CONFERENCE
Electronics 2023, 12, 2465, May 2023
ACCEPTED/PUBLISHED DATE
May 2023
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/12/11/2465
ABSTRACT
From the first patent of supercapacitors, the industry has experienced the commercialization. of supercapacitors happening rapidly after the year 2000. Within the last 5 years, the electronics industry has gained access to at least four different types of commercially available supercapacitor families, namely, electrochemical double layer capacitors (EDLCs), hybrid supercapacitors, battery capacitors and pseudo capacitors. Over the same period after year 2000, there has been huge developments in the electrochemistry of supercapacitors based on new materials such as graphene and mechanisms such as tailoring pore sizes for electrolyte ion exchange to increase volumetric energy density. This paper compares the characteristics of three different types of supercapacitors for large energy applications and how supercapacitors can be useful in future DC-DC converters in renewable and micro-grid applications.
Sirimanne, D.C.U., Kularatna, N., Arawwawala, N.
JOURNAL/CONFERENCE
Electronics 2023, 12, 2465, May 2023
ACCEPTED/PUBLISHED DATE
May 2023
PUBLISHED LOCATION
https://www.mdpi.com/2079-9292/12/11/2465
ABSTRACT
From the first patent of supercapacitors, the industry has experienced the commercialization. of supercapacitors happening rapidly after the year 2000. Within the last 5 years, the electronics industry has gained access to at least four different types of commercially available supercapacitor families, namely, electrochemical double layer capacitors (EDLCs), hybrid supercapacitors, battery capacitors and pseudo capacitors. Over the same period after year 2000, there has been huge developments in the electrochemistry of supercapacitors based on new materials such as graphene and mechanisms such as tailoring pore sizes for electrolyte ion exchange to increase volumetric energy density. This paper compares the characteristics of three different types of supercapacitors for large energy applications and how supercapacitors can be useful in future DC-DC converters in renewable and micro-grid applications.
Green Book on IEC 61850 Principles and Applications to Electric Power Systems.
AUTHORS
Nirmal Nair
JOURNAL/CONFERENCE
Springer Publisher
ACCEPTED/PUBLISHED DATE
May 2023
PUBLISHED LOCATION
https://link.springer.com/book/10.1007/978-3-031-24567-1
ABSTRACT
This publication serves as a valuable resource in the field, highlighting his contributions to the understanding and application of IEC 61850 standards.
Nirmal Nair
JOURNAL/CONFERENCE
Springer Publisher
ACCEPTED/PUBLISHED DATE
May 2023
PUBLISHED LOCATION
https://link.springer.com/book/10.1007/978-3-031-24567-1
ABSTRACT
This publication serves as a valuable resource in the field, highlighting his contributions to the understanding and application of IEC 61850 standards.
Medium Voltage DC Cables: A Look to the Future
AUTHORS
Andrew Lapthorn, Uwe Schichler
JOURNAL/CONFERENCE
Jicable'23 International Conference, Lyon, France
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.jicable23.jicable.org/
ABSTRACT
MVDC power cable applications today are minimal and handled on an “ad-hoc” basis adapting from either MVAC standards and materials, or HVDC standards and materials. MVAC standards do not generally account for aspects unique to DC applications such as interdependency of conductivity with temperature and field strength and the potential risk of space charge accumulation. Whereas the stringent testing requirements for HVDC cables may be too onerous due to the lower field strength leading to a lower impact of conductivity, potentially adding costs. This paper presents an overview of the technical issues related to MVDC cables, a discussion on possible approaches, and some initial results from testing MVAC cables under MVDC conditions at various high-voltage laboratories around the world.
Andrew Lapthorn, Uwe Schichler
JOURNAL/CONFERENCE
Jicable'23 International Conference, Lyon, France
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.jicable23.jicable.org/
ABSTRACT
MVDC power cable applications today are minimal and handled on an “ad-hoc” basis adapting from either MVAC standards and materials, or HVDC standards and materials. MVAC standards do not generally account for aspects unique to DC applications such as interdependency of conductivity with temperature and field strength and the potential risk of space charge accumulation. Whereas the stringent testing requirements for HVDC cables may be too onerous due to the lower field strength leading to a lower impact of conductivity, potentially adding costs. This paper presents an overview of the technical issues related to MVDC cables, a discussion on possible approaches, and some initial results from testing MVAC cables under MVDC conditions at various high-voltage laboratories around the world.
Simulating Solar Storms via Active DC Injection from the HVDC Link
AUTHORS
Andrew Lapthorn, Stewart Hardie, Paul Agger, Soren Subritzky, Mike Dalzell, Mark Clilverd, Ciaran Beggan, Juliane Huebert, Eliot Eaton, and Craig Rodger
JOURNAL/CONFERENCE
EEA2023 Conference, 27 – 29 June 2023, Christchurch
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/conference-2023
ABSTRACT
As part of the MBIE Endeavour programme “Solar Tsunamis: Space-Weather Prediction and Risk Mitigation for New Zealand’s Energy Infrastructure” we are interested in the effects of geomagnetically induced currents (GICs) on New Zealand’s electrical infrastructure. GICs appear as quasi-dc currents on the power system and can lead to problems in the network as a result of transformer saturation such as increased reactive power demand, increased harmonics, and even overloading of the transformers. Studies have shown that, depending on the severity of the solar storm, these effects could potentially be widespread. Different transformer designs behave differently under these quasi-dc conditions, with single-phase designs the worst, and three-limb core designs proving the most resilient. Furthermore, several transformers in New Zealand have neutral earthing resistors (NERs) installed. Therefore, it is difficult to say at what point do GICs start becoming a problem, and how much current is too much current. In January 2023, with the support of Transpower, we were able to utilise New Zealand’s high voltage DC (HVDC) link to inject current directly into the ground at Haywards substation and monitor the effects on several 216MVA 220 kV / 110 kV autotransformers, along with monitoring of associated transmission lines. Over the span of nine days, six injection tests were carried out lasting between one and two hours each time. The peak current injected into the ground was about 621 A. This paper provides an overview of the testing plan, procedure and initial results from the collected data.
Andrew Lapthorn, Stewart Hardie, Paul Agger, Soren Subritzky, Mike Dalzell, Mark Clilverd, Ciaran Beggan, Juliane Huebert, Eliot Eaton, and Craig Rodger
JOURNAL/CONFERENCE
EEA2023 Conference, 27 – 29 June 2023, Christchurch
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/conference-2023
ABSTRACT
As part of the MBIE Endeavour programme “Solar Tsunamis: Space-Weather Prediction and Risk Mitigation for New Zealand’s Energy Infrastructure” we are interested in the effects of geomagnetically induced currents (GICs) on New Zealand’s electrical infrastructure. GICs appear as quasi-dc currents on the power system and can lead to problems in the network as a result of transformer saturation such as increased reactive power demand, increased harmonics, and even overloading of the transformers. Studies have shown that, depending on the severity of the solar storm, these effects could potentially be widespread. Different transformer designs behave differently under these quasi-dc conditions, with single-phase designs the worst, and three-limb core designs proving the most resilient. Furthermore, several transformers in New Zealand have neutral earthing resistors (NERs) installed. Therefore, it is difficult to say at what point do GICs start becoming a problem, and how much current is too much current. In January 2023, with the support of Transpower, we were able to utilise New Zealand’s high voltage DC (HVDC) link to inject current directly into the ground at Haywards substation and monitor the effects on several 216MVA 220 kV / 110 kV autotransformers, along with monitoring of associated transmission lines. Over the span of nine days, six injection tests were carried out lasting between one and two hours each time. The peak current injected into the ground was about 621 A. This paper provides an overview of the testing plan, procedure and initial results from the collected data.
DC Homes Integration to Low-voltage AC Electricity Distribution Networks
AUTHORS
Michael Gibson, Nirmal Nair
JOURNAL/CONFERENCE
EEA 2023 Conference, Christchurch, 27-29 June, 2023
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/conference-2023
ABSTRACT
AC architectures have been the standard for electricity distribution and the dominating features for grid structures worldwide for the past century. This type of distribution is predominantly due to the paradigm regarding the cost and efficiency of power transmission over long distances and ac voltage stepping using transformers. However, in recent times, ac distribution has been challenged by the lack of converter requirements, systems efficiency, and consumer trends in dc appliances, electric vehicles (EV), and photovoltaic systems (PV). The benefits of efficiency that dc distribution systems have to offer align heavily with New Zealand’s commitments in Paris Agreement to reduce its greenhouse emissions by 30% below its 2005 levels by 2030. Due to these aspects, the gross increase in the dc load within homes has made low-voltage dc distribution systems attractive at home. As the usage of dc loads is expected to grow and expand at an exponential rate rapidly, an increase of 50-70% by 2050, the urgency for extensive research in the field of low-voltage dc distribution networks is substantial. This paper explores the development of a low-voltage dc home architecture model to evaluate associated protection requirements that are likely required for its feasibility. This paper shows the modelling behind implementing a low-voltage dc home distribution network that works with the current single-phase ac network. The dc home configuration utilises a 310V and a 48V dc bus. A model in MATLAB/Simulink has been partially successful in replicating a dc home with control topologies and realistic parameters. The parameters can be changed in this model to produce estimates for fault current analysis, which then can be used to develop protection schemes and devices to support the development of dc homes and infrastructure. The model has successfully reduced the use of power converters, which is the primary goal of achieving higher efficiency in the home distribution system. Control strategies and topologies have been added to the model for maximum power point tracking (MPPT) for PV, converter control, and battery storage to further optimise the model. Others can use the MATLAB/Simulink model as a tool for necessary numerical analysis. Despite this model being partially complete, if the proper steps are taken to develop the model further, this highly efficient dc home architecture could become a reality for residential consumers.
Michael Gibson, Nirmal Nair
JOURNAL/CONFERENCE
EEA 2023 Conference, Christchurch, 27-29 June, 2023
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/conference-2023
ABSTRACT
AC architectures have been the standard for electricity distribution and the dominating features for grid structures worldwide for the past century. This type of distribution is predominantly due to the paradigm regarding the cost and efficiency of power transmission over long distances and ac voltage stepping using transformers. However, in recent times, ac distribution has been challenged by the lack of converter requirements, systems efficiency, and consumer trends in dc appliances, electric vehicles (EV), and photovoltaic systems (PV). The benefits of efficiency that dc distribution systems have to offer align heavily with New Zealand’s commitments in Paris Agreement to reduce its greenhouse emissions by 30% below its 2005 levels by 2030. Due to these aspects, the gross increase in the dc load within homes has made low-voltage dc distribution systems attractive at home. As the usage of dc loads is expected to grow and expand at an exponential rate rapidly, an increase of 50-70% by 2050, the urgency for extensive research in the field of low-voltage dc distribution networks is substantial. This paper explores the development of a low-voltage dc home architecture model to evaluate associated protection requirements that are likely required for its feasibility. This paper shows the modelling behind implementing a low-voltage dc home distribution network that works with the current single-phase ac network. The dc home configuration utilises a 310V and a 48V dc bus. A model in MATLAB/Simulink has been partially successful in replicating a dc home with control topologies and realistic parameters. The parameters can be changed in this model to produce estimates for fault current analysis, which then can be used to develop protection schemes and devices to support the development of dc homes and infrastructure. The model has successfully reduced the use of power converters, which is the primary goal of achieving higher efficiency in the home distribution system. Control strategies and topologies have been added to the model for maximum power point tracking (MPPT) for PV, converter control, and battery storage to further optimise the model. Others can use the MATLAB/Simulink model as a tool for necessary numerical analysis. Despite this model being partially complete, if the proper steps are taken to develop the model further, this highly efficient dc home architecture could become a reality for residential consumers.
LV cable renewal forecasting – how near is the wall of wire?
AUTHORS
Andre Cuppen and Michael Gibson
JOURNAL/CONFERENCE
EEA 2023 Conference, Christchurch, 27-29 June, 2023
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/conference-2023
ABSTRACT
Low voltage (LV) cables have been an essential part of our daily lives, providing a reliable and low cost means to supply energy for decades. However, as with any infrastructure, these cables have a limited lifespan. Pro-active renewal will likely become more cost effective and provide better performance than continually repairing reactively. While the exact lifespan of low voltage cables can vary based on several factors, it is important to plan for the replacement of ageing infrastructure to ensure continued safe, affordable and reliable service. LV cable installations ramped up from 10 km/year to 90 km/year between 1960 and 1975. As these oldest cables are almost 60 years old, a renewal wave may be entering our 10-year renewal horizon. Our goal is to forecast the change in LV cable failure rate, and detect defective cable components before they fail. In this way, we can proactively initiate a cable replacement plan several years in advance, prior to experiencing repeated failures. By being proactive we can maintain the delivery of safe, affordable, reliable, and sustainable energy through low voltage cables for years to come. The implementation of a proactive renewal and repair strategy is challenged by, among others, the uncertainty in life expectation of 60, 70, maybe 80 years of cable segments, accessories and connected equipment. Another factor is the uncertainty of benefit of managing the end-of-life (EOL) of an aged generation of LV cable circuits. The implementation of a proactive renewal and repair strategy is challenged by, among others, the uncertainty in life expectation of 60, 70, maybe 80 years of cable segments, accessories and connected equipment. Another factor is the uncertainty of benefit of managing the end-of-life (EOL) of an aged generation of LV cable circuits. This paper will explore the benefits and potential challenges related to implementing proactive renewal of ageing low voltage cables. We will examine the current age of the cable fleet, existing fault rates, and anticipate a significant increase in fault rates in the coming years. We touch on the benefit of managing the end-of-life of an aged generation of LV cable circuits. We also examine the impact of the uncertainty in life expectation on the steady state renewal program we foresee.
Andre Cuppen and Michael Gibson
JOURNAL/CONFERENCE
EEA 2023 Conference, Christchurch, 27-29 June, 2023
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://www.eea.co.nz/Site/news-events/conferences/conference-2023
ABSTRACT
Low voltage (LV) cables have been an essential part of our daily lives, providing a reliable and low cost means to supply energy for decades. However, as with any infrastructure, these cables have a limited lifespan. Pro-active renewal will likely become more cost effective and provide better performance than continually repairing reactively. While the exact lifespan of low voltage cables can vary based on several factors, it is important to plan for the replacement of ageing infrastructure to ensure continued safe, affordable and reliable service. LV cable installations ramped up from 10 km/year to 90 km/year between 1960 and 1975. As these oldest cables are almost 60 years old, a renewal wave may be entering our 10-year renewal horizon. Our goal is to forecast the change in LV cable failure rate, and detect defective cable components before they fail. In this way, we can proactively initiate a cable replacement plan several years in advance, prior to experiencing repeated failures. By being proactive we can maintain the delivery of safe, affordable, reliable, and sustainable energy through low voltage cables for years to come. The implementation of a proactive renewal and repair strategy is challenged by, among others, the uncertainty in life expectation of 60, 70, maybe 80 years of cable segments, accessories and connected equipment. Another factor is the uncertainty of benefit of managing the end-of-life (EOL) of an aged generation of LV cable circuits. The implementation of a proactive renewal and repair strategy is challenged by, among others, the uncertainty in life expectation of 60, 70, maybe 80 years of cable segments, accessories and connected equipment. Another factor is the uncertainty of benefit of managing the end-of-life (EOL) of an aged generation of LV cable circuits. This paper will explore the benefits and potential challenges related to implementing proactive renewal of ageing low voltage cables. We will examine the current age of the cable fleet, existing fault rates, and anticipate a significant increase in fault rates in the coming years. We touch on the benefit of managing the end-of-life of an aged generation of LV cable circuits. We also examine the impact of the uncertainty in life expectation on the steady state renewal program we foresee.
CIGRE TB 896 on Protection for developing network with limited fault current capability of generation
AUTHORS
Nirmal Nair
JOURNAL/CONFERENCE
CIGRE
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://electra.cigre.org/328-june-2023/technical-brochures/protection-for-developing-network-with-limited-fault-current-capability-of-generation.html
ABSTRACT
Power system protection is of great importance to safety and reliability of the power grid. With new generations (such as wind and solar power sources), network structures and load penetrating all over the power system, traditional protection functions are facing challenges. According to the industrial projects, four testing system benchmarks for protection research of the network with high proportion of power electronic devices are provided in this brochure. Start with the control system and get the fault current characteristics, the short-circuit current model of power electronic devices can be established. On this basis, the technical brochure researches the performance of traditional protection in order to determine the protection configuration principles and explore new protection principles. Then, the novel protection principles of renewable energy power plants, AC/DC hybrid system, and DC distribution system are presented. Most of these protection principles are in the theoretical research stage. It is recommended to do more systematic researches for protection of the developing network.
Nirmal Nair
JOURNAL/CONFERENCE
CIGRE
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://electra.cigre.org/328-june-2023/technical-brochures/protection-for-developing-network-with-limited-fault-current-capability-of-generation.html
ABSTRACT
Power system protection is of great importance to safety and reliability of the power grid. With new generations (such as wind and solar power sources), network structures and load penetrating all over the power system, traditional protection functions are facing challenges. According to the industrial projects, four testing system benchmarks for protection research of the network with high proportion of power electronic devices are provided in this brochure. Start with the control system and get the fault current characteristics, the short-circuit current model of power electronic devices can be established. On this basis, the technical brochure researches the performance of traditional protection in order to determine the protection configuration principles and explore new protection principles. Then, the novel protection principles of renewable energy power plants, AC/DC hybrid system, and DC distribution system are presented. Most of these protection principles are in the theoretical research stage. It is recommended to do more systematic researches for protection of the developing network.
Book Reviews in IEEE Electrical Insulation Magazine, JUNE 2023
AUTHORS
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE Electrical Insulation Magazine, May/June Issue 2023, Vol 39, No 3, pp 43-45
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10101726&tag=1
ABSTRACT
Review of two of the latest books related to electrical power systems.
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE Electrical Insulation Magazine, May/June Issue 2023, Vol 39, No 3, pp 43-45
ACCEPTED/PUBLISHED DATE
June 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10101726&tag=1
ABSTRACT
Review of two of the latest books related to electrical power systems.
Plasma absorption techniques in direct current circuit breakers
AUTHORS
Chamara Dassanayake, Nihal Kularatna, Alistair Steyn-Ross, Kosala Gunawardane and Nicoloy Gurusinghe
JOURNAL/CONFERENCE
Proceedings of IEEE- IESES 2023 Conference
ACCEPTED/PUBLISHED DATE
July 2023
ABSTRACT
DC circuit breakers are becoming popular in the industry with the renewable energy demand. Compared to ACcircuit breaking, DC circuit breaking needs an advanced method to immobilize the arc generated during the opening process ofthe circuit breaker. These days, AC circuit breakers are used with simple modifications for DC circuit breaking. Commercial parties simply modify the AC circuit breakers to operate on DC. However, specifically manufactured DC circuit breakers are necessary for the long run as modified versions still have minimum cycle life due to contact point degradation compared to commercially available AC circuit breakers. This paper proposes a new concept for DC circuit breakers where a supercapacitor will be used to absorb the arc energy to extend its cycle life.
Chamara Dassanayake, Nihal Kularatna, Alistair Steyn-Ross, Kosala Gunawardane and Nicoloy Gurusinghe
JOURNAL/CONFERENCE
Proceedings of IEEE- IESES 2023 Conference
ACCEPTED/PUBLISHED DATE
July 2023
ABSTRACT
DC circuit breakers are becoming popular in the industry with the renewable energy demand. Compared to ACcircuit breaking, DC circuit breaking needs an advanced method to immobilize the arc generated during the opening process ofthe circuit breaker. These days, AC circuit breakers are used with simple modifications for DC circuit breaking. Commercial parties simply modify the AC circuit breakers to operate on DC. However, specifically manufactured DC circuit breakers are necessary for the long run as modified versions still have minimum cycle life due to contact point degradation compared to commercially available AC circuit breakers. This paper proposes a new concept for DC circuit breakers where a supercapacitor will be used to absorb the arc energy to extend its cycle life.
ADVANCED APPROACH FOR STABILITY ASSESSMENT OF PHIL SETUPS COUPLED BY CLARKE-PARK TRANSFORM
AUTHORS
Tran The Hoang, Nirmal Nair
JOURNAL/CONFERENCE
IEEE PES General Meeting 2023, Orlando, Florida
ACCEPTED/PUBLISHED DATE
July 2023
ABSTRACT
Power-Hardware-in-the-Loop (PHIL) has been playing an increasingly important role in testing and validating new technologies, especially in smart grids. Two main concerns related to PHIL-based testing are stability and accuracy. Amongst others, time delay compensation and inclusion of feedback low-pass filter (LPF) using Clarke-Park transform (or dq0 transform) seem promising candidates for improving the stability and accuracy of the PHIL setup. However, the method for evaluating these PHIL setups has not been thoroughly developed since only simple Single-Input-Single-Output (SISO) models have been adopted for various stability criteria such as Nyquist or Routh–Hurwitz stability criteria. Therefore, this paper will provide a new and more comprehensive Multi-Input-Multi-Output (MIMO) approach for assessing the stability of the dq0-based PHIL setups. Compared to the conventional SISO approach, the proposed MIMO model can provide a better evaluation, and its effectiveness has been verified through empirical simulations using MATLAB/Simulink.
Tran The Hoang, Nirmal Nair
JOURNAL/CONFERENCE
IEEE PES General Meeting 2023, Orlando, Florida
ACCEPTED/PUBLISHED DATE
July 2023
ABSTRACT
Power-Hardware-in-the-Loop (PHIL) has been playing an increasingly important role in testing and validating new technologies, especially in smart grids. Two main concerns related to PHIL-based testing are stability and accuracy. Amongst others, time delay compensation and inclusion of feedback low-pass filter (LPF) using Clarke-Park transform (or dq0 transform) seem promising candidates for improving the stability and accuracy of the PHIL setup. However, the method for evaluating these PHIL setups has not been thoroughly developed since only simple Single-Input-Single-Output (SISO) models have been adopted for various stability criteria such as Nyquist or Routh–Hurwitz stability criteria. Therefore, this paper will provide a new and more comprehensive Multi-Input-Multi-Output (MIMO) approach for assessing the stability of the dq0-based PHIL setups. Compared to the conventional SISO approach, the proposed MIMO model can provide a better evaluation, and its effectiveness has been verified through empirical simulations using MATLAB/Simulink.
DC Circuit Breaker Evolution, Design, and Analysis
AUTHORS
Medhi Moradian, Tek Tjing Lie, Kosala Gunawardane
JOURNAL/CONFERENCE
Energies 2023 Vol 16, Issue 17
ACCEPTED/PUBLISHED DATE
August 2023
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/16/17/6130
ABSTRACT
While traditional AC mechanical circuit breakers can protect AC circuits, many other DC power distribution technologies, such as DC microgrids (MGs), yield superior disruption performance, e.g., faster and more reliable switching speeds. However, novel DC circuit breaker (DCCB) designs are challenging due to the need to quickly break high currents within milliseconds, caused by the high fault current rise in DC grids compared to AC grids. In DC grids, the circuit breaker must not provide any current crossing and must absorb surges, since the arc is not naturally extinguished by the system. Additionally, the DC breaker must mitigate the magnetic energy stored in the system inductance and withstand residual overvoltages after current interruption. These challenges require a fundamentally different topology for DCCBs, which are typically made using solid-state semiconductor technology, metal oxide varistors (MOVs), and ultra-fast switches. This study aims to provide a comprehensive review of the development, design, and performance of DCCBs and an analysis of internal topology, the energy absorption path, and subcircuits in solid-state (SS)-based DCCBs. The research explores various novel designs that introduce different structures for an energy dissipation solution. The classification of these designs is based on the fundamental principles of surge mitigation and a detailed analysis of the techniques employed in DCCBs. In addition, our framework offers an advantageous reference point for the future evolution of SS circuit breakers in numerous developing power delivery systems.
Medhi Moradian, Tek Tjing Lie, Kosala Gunawardane
JOURNAL/CONFERENCE
Energies 2023 Vol 16, Issue 17
ACCEPTED/PUBLISHED DATE
August 2023
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/16/17/6130
ABSTRACT
While traditional AC mechanical circuit breakers can protect AC circuits, many other DC power distribution technologies, such as DC microgrids (MGs), yield superior disruption performance, e.g., faster and more reliable switching speeds. However, novel DC circuit breaker (DCCB) designs are challenging due to the need to quickly break high currents within milliseconds, caused by the high fault current rise in DC grids compared to AC grids. In DC grids, the circuit breaker must not provide any current crossing and must absorb surges, since the arc is not naturally extinguished by the system. Additionally, the DC breaker must mitigate the magnetic energy stored in the system inductance and withstand residual overvoltages after current interruption. These challenges require a fundamentally different topology for DCCBs, which are typically made using solid-state semiconductor technology, metal oxide varistors (MOVs), and ultra-fast switches. This study aims to provide a comprehensive review of the development, design, and performance of DCCBs and an analysis of internal topology, the energy absorption path, and subcircuits in solid-state (SS)-based DCCBs. The research explores various novel designs that introduce different structures for an energy dissipation solution. The classification of these designs is based on the fundamental principles of surge mitigation and a detailed analysis of the techniques employed in DCCBs. In addition, our framework offers an advantageous reference point for the future evolution of SS circuit breakers in numerous developing power delivery systems.
Book Reviews in IEEE Electrical Insulation Magazine, August 2023
AUTHORS
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE Electrical Insulation Magazine July/Aug edition
ACCEPTED/PUBLISHED DATE
August 2023
PUBLISHED LOCATION
https://ieeexplore-ieee-org.ezproxy.waikato.ac.nz/stamp/stamp.jsp?tp=&arnumber=10151813
ABSTRACT
Nihal Kularatna reviewed three of the latest books related to electrical power systems.
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE Electrical Insulation Magazine July/Aug edition
ACCEPTED/PUBLISHED DATE
August 2023
PUBLISHED LOCATION
https://ieeexplore-ieee-org.ezproxy.waikato.ac.nz/stamp/stamp.jsp?tp=&arnumber=10151813
ABSTRACT
Nihal Kularatna reviewed three of the latest books related to electrical power systems.
FUTURE DIRECTIONS OF COMMERCIALLY AVAILABLE SUPERCAPACITORS COMPARED WITH RECHARGEABLE BATTERIES FOR RENEWABLE ENERGY APPLICATIONS
AUTHORS
Arawwawala, N., Kularatna, N. & Sirimanne, D.C.U.,
JOURNAL/CONFERENCE
IEEE Power Electronics Magazine, Sept 2023 Issue
ACCEPTED/PUBLISHED DATE
September 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=10262070
ABSTRACT
Energy storage devices (ESDs) have become an essential component in renewable energy systems for higher reliability, given the fluctuating nature of renewable energy sources such as solar, wind, and biomass. Thus, various types of ESDs have been invented over the past years, and rechargeable batteries play an increasingly vital role in storing energy in response to the fluctuating nature of the renewable sources and increasing demand for reliable renewable energy sources. ESD options for longer-term and infrequent utilization can be listed primarily as below [1]:
- Rechargeable batteries
- SC banks
- Flywheels
- Thermal energy storage system
- Fuel cells
- Compressed air energy storage system
- Superconductive Magnetic Energy Storage (SMES)
- Pumped hydro-storage
In this review article, mainly the lithium based rechargeable battery technologies and supercapacitors have been investigated and compared.
Arawwawala, N., Kularatna, N. & Sirimanne, D.C.U.,
JOURNAL/CONFERENCE
IEEE Power Electronics Magazine, Sept 2023 Issue
ACCEPTED/PUBLISHED DATE
September 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=10262070
ABSTRACT
Energy storage devices (ESDs) have become an essential component in renewable energy systems for higher reliability, given the fluctuating nature of renewable energy sources such as solar, wind, and biomass. Thus, various types of ESDs have been invented over the past years, and rechargeable batteries play an increasingly vital role in storing energy in response to the fluctuating nature of the renewable sources and increasing demand for reliable renewable energy sources. ESD options for longer-term and infrequent utilization can be listed primarily as below [1]:
- Rechargeable batteries
- SC banks
- Flywheels
- Thermal energy storage system
- Fuel cells
- Compressed air energy storage system
- Superconductive Magnetic Energy Storage (SMES)
- Pumped hydro-storage
In this review article, mainly the lithium based rechargeable battery technologies and supercapacitors have been investigated and compared.
Development of a Directional Element for Solar Inverter-Rich Distribution Networks
AUTHORS
Tran T. Hoang and Nirmal Nair
JOURNAL/CONFERENCE
2023 IEEE PES ISGT Europe Conference
ACCEPTED/PUBLISHED DATE
October 2023
PUBLISHED LOCATION
https://attend.ieee.org/isgt-europe-2023/
ABSTRACT
The high penetration of electronic-coupled distributed energy sources, especially photovoltaic systems into distribution networks have created new challenges for traditional non-directional protection systems. Fault currents can now come from multiple sources, making protection location and direction detection difficult. Although conventional negative-sequence directional elements have been proposed as alternative solutions for detecting unbalanced fault direction, the unusual waveforms of current and voltage contributed by photovoltaic systems can adversely affect their performance. This paper proposes a new directional approach that utilizes prefault voltage and during-fault negative-sequence current component to determine the direction of unbalanced faults in photovoltaic system-dominated distribution networks while considering the dynamic voltage support of photovoltaic systems as imposed by new grid code requirement. The proposed method is validated through numerical analysis and EMT simulations in the software environment PowerFactory/DIgSILENT.
Tran T. Hoang and Nirmal Nair
JOURNAL/CONFERENCE
2023 IEEE PES ISGT Europe Conference
ACCEPTED/PUBLISHED DATE
October 2023
PUBLISHED LOCATION
https://attend.ieee.org/isgt-europe-2023/
ABSTRACT
The high penetration of electronic-coupled distributed energy sources, especially photovoltaic systems into distribution networks have created new challenges for traditional non-directional protection systems. Fault currents can now come from multiple sources, making protection location and direction detection difficult. Although conventional negative-sequence directional elements have been proposed as alternative solutions for detecting unbalanced fault direction, the unusual waveforms of current and voltage contributed by photovoltaic systems can adversely affect their performance. This paper proposes a new directional approach that utilizes prefault voltage and during-fault negative-sequence current component to determine the direction of unbalanced faults in photovoltaic system-dominated distribution networks while considering the dynamic voltage support of photovoltaic systems as imposed by new grid code requirement. The proposed method is validated through numerical analysis and EMT simulations in the software environment PowerFactory/DIgSILENT.
Arc absorption options based on passive compenents in DC circuit breakers
AUTHORS
Chamara Dassanayake, Nihal Kularatna, Alistair Steyn-Ross, Kosala Gunawardane and Nicoloy Gurusinghe
JOURNAL/CONFERENCE
IECON 2023- 49th Annual Conference
ACCEPTED/PUBLISHED DATE
October 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10312678
ABSTRACT
DC circuit breakers have become an essential protection element for DC buses in renewable energy and DC microgrid systems. Given that there are no zero crossings in a DC power supply compared to an AC waveform, arc extinguishing is a difficult process in DC circuit breakers. Solid state switches are proposed in solving this problem, but their cost is generally unaffordable in general applications, except for marine, military and aviation etc. Hence, commercial and mass-produced DC breakers are modified versions of AC breakers. This paper details different passive component options for absorbing the energy in the electric arc/plasma, including the use of supercapacitors.
Chamara Dassanayake, Nihal Kularatna, Alistair Steyn-Ross, Kosala Gunawardane and Nicoloy Gurusinghe
JOURNAL/CONFERENCE
IECON 2023- 49th Annual Conference
ACCEPTED/PUBLISHED DATE
October 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10312678
ABSTRACT
DC circuit breakers have become an essential protection element for DC buses in renewable energy and DC microgrid systems. Given that there are no zero crossings in a DC power supply compared to an AC waveform, arc extinguishing is a difficult process in DC circuit breakers. Solid state switches are proposed in solving this problem, but their cost is generally unaffordable in general applications, except for marine, military and aviation etc. Hence, commercial and mass-produced DC breakers are modified versions of AC breakers. This paper details different passive component options for absorbing the energy in the electric arc/plasma, including the use of supercapacitors.
Supercapacitor based adjustable high power pulse generator for medical research applications
AUTHORS
Soniya Raju, Nihal Kularatna & Marcus Wilson
JOURNAL/CONFERENCE
IECON 2023- 49th Annual Conference
ACCEPTED/PUBLISHED DATE
October 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10311985
ABSTRACT
High power pulse generators with variable parameters are helpful in many applications in the industrial and medical fields. The traditional approach to design these pulse generators is to start with a high voltage DC power supply, energy storage capacitor, and a wave shaping circuit. However, building a high-voltage DC power supply itself is a complex task and it ends up in a complicated circuit with several high-voltage components hence adding to the total cost. This paper presents a unique new approach to designing a supercapacitor-based high-voltage pulse generator with a lower number of components and simple two-winding transformer. First experimental circuit developed based on this new approach is presented here with variable pulse generator capable of several hundred volts peak voltage with loop current capability of several hundred amperes.
Soniya Raju, Nihal Kularatna & Marcus Wilson
JOURNAL/CONFERENCE
IECON 2023- 49th Annual Conference
ACCEPTED/PUBLISHED DATE
October 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10311985
ABSTRACT
High power pulse generators with variable parameters are helpful in many applications in the industrial and medical fields. The traditional approach to design these pulse generators is to start with a high voltage DC power supply, energy storage capacitor, and a wave shaping circuit. However, building a high-voltage DC power supply itself is a complex task and it ends up in a complicated circuit with several high-voltage components hence adding to the total cost. This paper presents a unique new approach to designing a supercapacitor-based high-voltage pulse generator with a lower number of components and simple two-winding transformer. First experimental circuit developed based on this new approach is presented here with variable pulse generator capable of several hundred volts peak voltage with loop current capability of several hundred amperes.
An Overview of the Unique DC Injection Campaign for Replicating GICs on High Voltage Transformers in New Zealand
AUTHORS
Andrew Lapthorn, Stewart Hardie, Paul Agger, Soren Subritzky, Mike Dalzell, Mark Clilverd, Neil Cobbett, Ciaran Beggan, Juliane Huebert, Eliot Eaton, James Brundell and Craig Rodger
JOURNAL/CONFERENCE
European Space Weather Week 2023, 20-24 November, Toulouse, France
ACCEPTED/PUBLISHED DATE
November 2023
PUBLISHED LOCATION
https://esww2023.org/
ABSTRACT
A government-funded research program in New Zealand is currently examining the impact of extreme space weather on the country's energy infrastructure. Specifically, we are interested in understanding how geomagnetically induced currents (GICs) affect high voltage power transformers. GICs manifest as quasi-DC currents within the power system and can create issues in the electrical network due to transformer saturation. These issues include increased reactive power demand, heightened harmonics, and potential transformer overloading. Research indicates that the effects of GICs could be widespread, depending on the severity of solar storms. Different transformer designs exhibit varying behaviours under these quasi-DC conditions. Single-phase designs are the most susceptible to adverse effects, while three-limb core designs have shown greater resilience. Moreover, a number of transformers in New Zealand are equipped with neutral earthing resistors (NERs). Consequently, determining the threshold at which GICs become problematic and identifying an excessive current limit becomes challenging. In January 2023, with the assistance of the National Grid operator Transpower, we leveraged New Zealand's high voltage DC (HVDC) transmission link to directly inject current into the ground at the Haywards substation near Wellington, New Zealand. We closely monitored the impact on two 216 MVA, 220/110 kV autotransformers, and one 80 MVA 11/110 kV autotransformer, as well as the associated transmission lines. This testing involved conducting six injection tests over a nine-day period, each lasting between one and two hours. The maximum current injected into the ground reached approximately 621 A. This paper provides an overview of the testing plan, procedure, and initial findings derived from the collected data.
Andrew Lapthorn, Stewart Hardie, Paul Agger, Soren Subritzky, Mike Dalzell, Mark Clilverd, Neil Cobbett, Ciaran Beggan, Juliane Huebert, Eliot Eaton, James Brundell and Craig Rodger
JOURNAL/CONFERENCE
European Space Weather Week 2023, 20-24 November, Toulouse, France
ACCEPTED/PUBLISHED DATE
November 2023
PUBLISHED LOCATION
https://esww2023.org/
ABSTRACT
A government-funded research program in New Zealand is currently examining the impact of extreme space weather on the country's energy infrastructure. Specifically, we are interested in understanding how geomagnetically induced currents (GICs) affect high voltage power transformers. GICs manifest as quasi-DC currents within the power system and can create issues in the electrical network due to transformer saturation. These issues include increased reactive power demand, heightened harmonics, and potential transformer overloading. Research indicates that the effects of GICs could be widespread, depending on the severity of solar storms. Different transformer designs exhibit varying behaviours under these quasi-DC conditions. Single-phase designs are the most susceptible to adverse effects, while three-limb core designs have shown greater resilience. Moreover, a number of transformers in New Zealand are equipped with neutral earthing resistors (NERs). Consequently, determining the threshold at which GICs become problematic and identifying an excessive current limit becomes challenging. In January 2023, with the assistance of the National Grid operator Transpower, we leveraged New Zealand's high voltage DC (HVDC) transmission link to directly inject current into the ground at the Haywards substation near Wellington, New Zealand. We closely monitored the impact on two 216 MVA, 220/110 kV autotransformers, and one 80 MVA 11/110 kV autotransformer, as well as the associated transmission lines. This testing involved conducting six injection tests over a nine-day period, each lasting between one and two hours. The maximum current injected into the ground reached approximately 621 A. This paper provides an overview of the testing plan, procedure, and initial findings derived from the collected data.
An Improved Control Method for Type-IV Wind Turbine Connected to Weak Grid Systems
AUTHORS
H. Wang, J. D. Watson, N. R. Watson
JOURNAL/CONFERENCE
IEEE PES ISGT ASIA 2023
ACCEPTED/PUBLISHED DATE
November 2023
ABSTRACT
This paper presents an improved control strategy for a type-IV wind turbine using the machine-side converter to control the DC voltage and the grid-side converter operation in the grid-forming (GFM) control mode. When wind power becomes a considerable portion of the power system or even the only energy source, the wind power systems must operate as a voltage source to maintain the terminal voltage magnitude and frequency by adjusting the real and reactive power. The generator output power should track the power to the grid to maintain the DC voltage. This paper proposes the coordinated control of the generator’s output power with a DC-link voltage controller for the generator-side converter. A dynamic model of the grid-side converter operating in GFM control mode has been built, and the voltage and frequency regulation strategy is presented. Simulation results using PSCAD/EMTDC demonstrate the control performances under various grid conditions, i.e., a wide range of short circuit ratio (SCR) and islanding grid conditions.
H. Wang, J. D. Watson, N. R. Watson
JOURNAL/CONFERENCE
IEEE PES ISGT ASIA 2023
ACCEPTED/PUBLISHED DATE
November 2023
ABSTRACT
This paper presents an improved control strategy for a type-IV wind turbine using the machine-side converter to control the DC voltage and the grid-side converter operation in the grid-forming (GFM) control mode. When wind power becomes a considerable portion of the power system or even the only energy source, the wind power systems must operate as a voltage source to maintain the terminal voltage magnitude and frequency by adjusting the real and reactive power. The generator output power should track the power to the grid to maintain the DC voltage. This paper proposes the coordinated control of the generator’s output power with a DC-link voltage controller for the generator-side converter. A dynamic model of the grid-side converter operating in GFM control mode has been built, and the voltage and frequency regulation strategy is presented. Simulation results using PSCAD/EMTDC demonstrate the control performances under various grid conditions, i.e., a wide range of short circuit ratio (SCR) and islanding grid conditions.
Modelling and Control of Dual Active Bridge DC-DC Converters in DC Grids
AUTHORS
Choidorj Adiyabazar, Josh Schipper, Jeremy Watson, Alan Wood
JOURNAL/CONFERENCE
ISGT 2023
ACCEPTED/PUBLISHED DATE
September 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10372767
ABSTRACT
This paper investigates the stability of cascaded Dual Active Bridge (DAB) DC/DC converters operating under a range of conditions. The multi-DAB converter’s reduced-order small signal models are formulated, and outer voltage and inner current loop controls are designed for each DAB converter. The performance of the proposed reduced-order model with the proposed control was validated via PSCAD/EMTDC simulation. These are used to predict the dynamics of the two DAB converters connected through a transmission line for different parameter values. Using sensitivity analysis, the impact of the transmission line inductance on the dynamic performance of the multi-DAB converter is investigated.
Choidorj Adiyabazar, Josh Schipper, Jeremy Watson, Alan Wood
JOURNAL/CONFERENCE
ISGT 2023
ACCEPTED/PUBLISHED DATE
September 2023
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10372767
ABSTRACT
This paper investigates the stability of cascaded Dual Active Bridge (DAB) DC/DC converters operating under a range of conditions. The multi-DAB converter’s reduced-order small signal models are formulated, and outer voltage and inner current loop controls are designed for each DAB converter. The performance of the proposed reduced-order model with the proposed control was validated via PSCAD/EMTDC simulation. These are used to predict the dynamics of the two DAB converters connected through a transmission line for different parameter values. Using sensitivity analysis, the impact of the transmission line inductance on the dynamic performance of the multi-DAB converter is investigated.
A review of low voltage cable diagnostics to support proactive renewal planning
AUTHORS
André Cuppen, Kewen Kueh
JOURNAL/CONFERENCE
Global CIGRE Symposium in Cairns, Australia
ACCEPTED/PUBLISHED DATE
September 2023
ABSTRACT
Low voltage cables have been an essential part of our daily lives, providing a reliable and low cost means to supply energy for decades. However, as with any infrastructure, these cables have a limited lifespan and it is likely to be more cost effective to replace than to continually repair. While the exact lifespan of low voltage cables can vary based on several factors, it is important to plan for the replacement of aging infrastructure to ensure continued safe, affordable and reliable service.
This paper will explore the potential challenges related to the replacement of aging low voltage cables. We will examine factors such as the impact of life expectation of 60 years, 70 years, maybe 80 on renewal and repair strategy & planning, and the possible reduction in cost by managing the end-of-life of an aged generation of LV cable circuits that may be just over the horizon.
Ideally, we would like to be able to predict when and where we might see (symptoms of) increase of future failures occurring so that we can initiate the plan to replace the cables several years before they (repeatedly) fail. This paper briefly reviews the progress in diagnostics and condition assessment of LV cable circuit and enclosures and the role that Smart Meters may play in online monitoring to enable planned replacements of low voltage cable circuits.
By taking a proactive approach to extend our infrastructure management to low voltage cable circuits, we can continue to enjoy safe, affordable, reliable and sustainable energy delivery through low voltage cables for years to come.
The contribution of this paper is a brief review of the work done the development of LV cable diagnostics and its role in Risk-Based Maintenance of these assets. Hopefully this will contribute to the discussion on the future of managing LV cables and gather input from colleagues in the international power industry community
André Cuppen, Kewen Kueh
JOURNAL/CONFERENCE
Global CIGRE Symposium in Cairns, Australia
ACCEPTED/PUBLISHED DATE
September 2023
ABSTRACT
Low voltage cables have been an essential part of our daily lives, providing a reliable and low cost means to supply energy for decades. However, as with any infrastructure, these cables have a limited lifespan and it is likely to be more cost effective to replace than to continually repair. While the exact lifespan of low voltage cables can vary based on several factors, it is important to plan for the replacement of aging infrastructure to ensure continued safe, affordable and reliable service.
This paper will explore the potential challenges related to the replacement of aging low voltage cables. We will examine factors such as the impact of life expectation of 60 years, 70 years, maybe 80 on renewal and repair strategy & planning, and the possible reduction in cost by managing the end-of-life of an aged generation of LV cable circuits that may be just over the horizon.
Ideally, we would like to be able to predict when and where we might see (symptoms of) increase of future failures occurring so that we can initiate the plan to replace the cables several years before they (repeatedly) fail. This paper briefly reviews the progress in diagnostics and condition assessment of LV cable circuit and enclosures and the role that Smart Meters may play in online monitoring to enable planned replacements of low voltage cable circuits.
By taking a proactive approach to extend our infrastructure management to low voltage cable circuits, we can continue to enjoy safe, affordable, reliable and sustainable energy delivery through low voltage cables for years to come.
The contribution of this paper is a brief review of the work done the development of LV cable diagnostics and its role in Risk-Based Maintenance of these assets. Hopefully this will contribute to the discussion on the future of managing LV cables and gather input from colleagues in the international power industry community
Enhanced Coordination in the PV–HESS Microgrids Cluster: Introducing a New Distributed Event Consensus Algorithm
AUTHORS
Z. H. A. Al-Tameemi, T. T. Lie, R. Zamora, F. Blaabjerg
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/17/2/293
ABSTRACT
To ensure reliable power delivery to customers under potential disturbances, the coordination of a microgrid cluster (MGC) is essential. Various control strategies—centralized, decentralized, distributed, and hierarchical—have been explored in the literature to achieve this goal. The hierarchical control method, with three distinct levels, has proven effective in fostering coordination among microgrids (MGs) within the cluster. The third control level, utilizing a time-triggering consensus protocol, relies on a continuous and reliable communication network for data exchange among MGs, leading to resource-intensive operations and potential data congestion. Moreover, uncertainties introduced by renewable energy sources (RESs) can adversely impact cluster performance. In response to these challenges, this paper introduces a new distributed event-triggered consensus algorithm (DETC) to enhance the efficiency in handling the aforementioned issues. The proposed algorithm significantly reduces communication burdens, addressing resource usage concerns. The performance of this approach is evaluated through simulations of a cluster comprising four DC MGs, in each of which were PV and a hybrid Battery-Super capacitor in the MATLAB environment. The key findings indicate that the proposed DETC algorithm achieves commendable results in terms of voltage regulation, precise power sharing among sources, and a reduction in triggering instants. Based on these results, this method can be deemed as a good development in MGC management, providing a more efficient and reliable means of coordination, particularly in scenarios with dynamic loads and renewable energy integration. It is also a viable option for current microgrid systems, due to its ability to decrease communication loads while retaining excellent performance.
Z. H. A. Al-Tameemi, T. T. Lie, R. Zamora, F. Blaabjerg
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/17/2/293
ABSTRACT
To ensure reliable power delivery to customers under potential disturbances, the coordination of a microgrid cluster (MGC) is essential. Various control strategies—centralized, decentralized, distributed, and hierarchical—have been explored in the literature to achieve this goal. The hierarchical control method, with three distinct levels, has proven effective in fostering coordination among microgrids (MGs) within the cluster. The third control level, utilizing a time-triggering consensus protocol, relies on a continuous and reliable communication network for data exchange among MGs, leading to resource-intensive operations and potential data congestion. Moreover, uncertainties introduced by renewable energy sources (RESs) can adversely impact cluster performance. In response to these challenges, this paper introduces a new distributed event-triggered consensus algorithm (DETC) to enhance the efficiency in handling the aforementioned issues. The proposed algorithm significantly reduces communication burdens, addressing resource usage concerns. The performance of this approach is evaluated through simulations of a cluster comprising four DC MGs, in each of which were PV and a hybrid Battery-Super capacitor in the MATLAB environment. The key findings indicate that the proposed DETC algorithm achieves commendable results in terms of voltage regulation, precise power sharing among sources, and a reduction in triggering instants. Based on these results, this method can be deemed as a good development in MGC management, providing a more efficient and reliable means of coordination, particularly in scenarios with dynamic loads and renewable energy integration. It is also a viable option for current microgrid systems, due to its ability to decrease communication loads while retaining excellent performance.
Control Strategies and Stabilization Techniques for DC/DC Converters Application in DC MGs: Challenges, Opportunities, and Prospects—A Review
AUTHORS
Nduwamungu, Aphrodis; Lie, Tek Tjing; Lestas, Ioannis; Nair, Nirmal-Kumar C
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/17/3/669
ABSTRACT
DC microgrids (DC MGs) offer advantages such as efficiency, control, cost, reliability, and size compared to AC MGs. However, they often operate with numerous constant power loads (CPLs), exhibiting a negative incremental impedance characteristic that can lead to instability. This instability weakens stability boundaries and reduces system damping, especially when dealing with pulsed power loads (PPLs) on electric aircraft, ships, and cars. Linear controllers may not ensure stability across various operations, causing voltage dips and potential system instability. To secure DC/DC converter functionality and comply with impedance specifications, it is crucial to consider minor loop gain in control strategies and stabilization techniques. Employing diverse methods to decrease minor loop gain in DC/DC converters is essential. A comprehensive evaluation, including strengths, weaknesses, opportunities, and threats (SWOT) analysis, is conducted to assess control strategies, stabilization techniques, and stability standards for different DC/DC converters, identifying SWOT.
Nduwamungu, Aphrodis; Lie, Tek Tjing; Lestas, Ioannis; Nair, Nirmal-Kumar C
JOURNAL/CONFERENCE
Energies
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://www.mdpi.com/1996-1073/17/3/669
ABSTRACT
DC microgrids (DC MGs) offer advantages such as efficiency, control, cost, reliability, and size compared to AC MGs. However, they often operate with numerous constant power loads (CPLs), exhibiting a negative incremental impedance characteristic that can lead to instability. This instability weakens stability boundaries and reduces system damping, especially when dealing with pulsed power loads (PPLs) on electric aircraft, ships, and cars. Linear controllers may not ensure stability across various operations, causing voltage dips and potential system instability. To secure DC/DC converter functionality and comply with impedance specifications, it is crucial to consider minor loop gain in control strategies and stabilization techniques. Employing diverse methods to decrease minor loop gain in DC/DC converters is essential. A comprehensive evaluation, including strengths, weaknesses, opportunities, and threats (SWOT) analysis, is conducted to assess control strategies, stabilization techniques, and stability standards for different DC/DC converters, identifying SWOT.
Methods for specification of functional requirements of protection, automation, and control
AUTHORS
I.P. SIQUEIRA, Convenor (BR), L. CALMON, Secretary (BR), A. APOSTOLOV (US), B. ANDRÉ (FR), C. RODRIGUEZ (ES), N.K. NAIR (NZ), P. MYRDA (US), P. ZHANG (US), S. HU (CN), S. HUSSEY (IE), S. BLAIR (GB), T. CHARTON (GB), V. LEITLOFF (FR)
JOURNAL/CONFERENCE
CIGRE Technical Brochure 926, 2024: Protection and automation (B5), WG B5.64
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://www.e-cigre.org/publications/detail/926-methods-for-specification-of-functional-requirements-of-protection-automation-and-control.html
ABSTRACT
This brochure presents the main treats of an informal or near-formal definition of a simplified Domain-Specific Language (DSL), informally called PacDSL, intended for the formal specification of functional requirements of Protection, Automation and Control of electrical power systems. The definition covers the basic aspects of the lexicon, syntax, semantics, and pragmatics of a typical DSL for this objective, that is agnostic to technology and proprietary solutions, aiming the needs of utilities, academics, manufacturers, and consultants. The brochure intends to document the need for this formalization, based on a survey among utility stakeholders, and to exemplify some possible constructs and Use Cases for this proposed language. It mainly shows its insertion in the engineering cycle during the requirement specification to be deployed on IEC 61850 and other implementation standards.
I.P. SIQUEIRA, Convenor (BR), L. CALMON, Secretary (BR), A. APOSTOLOV (US), B. ANDRÉ (FR), C. RODRIGUEZ (ES), N.K. NAIR (NZ), P. MYRDA (US), P. ZHANG (US), S. HU (CN), S. HUSSEY (IE), S. BLAIR (GB), T. CHARTON (GB), V. LEITLOFF (FR)
JOURNAL/CONFERENCE
CIGRE Technical Brochure 926, 2024: Protection and automation (B5), WG B5.64
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://www.e-cigre.org/publications/detail/926-methods-for-specification-of-functional-requirements-of-protection-automation-and-control.html
ABSTRACT
This brochure presents the main treats of an informal or near-formal definition of a simplified Domain-Specific Language (DSL), informally called PacDSL, intended for the formal specification of functional requirements of Protection, Automation and Control of electrical power systems. The definition covers the basic aspects of the lexicon, syntax, semantics, and pragmatics of a typical DSL for this objective, that is agnostic to technology and proprietary solutions, aiming the needs of utilities, academics, manufacturers, and consultants. The brochure intends to document the need for this formalization, based on a survey among utility stakeholders, and to exemplify some possible constructs and Use Cases for this proposed language. It mainly shows its insertion in the engineering cycle during the requirement specification to be deployed on IEC 61850 and other implementation standards.
A Novel Approach for Mitigating Mechanical DCCB Switching Effects using Supercapacitor Bypass Technique
AUTHORS
Mehdi Moradian, Tek Tjing Lie and Kosala Gunawardane
JOURNAL/CONFERENCE
2023 IEEE International Conference on Energy Technologies for Future Grids
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10407168
ABSTRACT
This article presents a novel design for mechanical DC circuit breakers (M-DCCB) that aims to address the switching effect associated with the open circuit phenomenon in DCCBs. Previous techniques have focused on the protection of DCCBs, but certain weaknesses in design and performance have been identified. This article aims to contribute by emphasizing the significance of shock absorption through the supercapacitor (SC) bypassing in DCCBs and assessing a novel approach called SC-based Bypass Technique (SCBT). The proposed technique is thoroughly discussed, offering improvements to overcome the limitations of existing model. The objective is to verify the secure and stable operation of the proposed model in effectively mitigating the bypassed switching effects. By incorporating the SC as a shock absorber, the new design aims to enhance the overall performance and reliability of the M-DCCB.
Mehdi Moradian, Tek Tjing Lie and Kosala Gunawardane
JOURNAL/CONFERENCE
2023 IEEE International Conference on Energy Technologies for Future Grids
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10407168
ABSTRACT
This article presents a novel design for mechanical DC circuit breakers (M-DCCB) that aims to address the switching effect associated with the open circuit phenomenon in DCCBs. Previous techniques have focused on the protection of DCCBs, but certain weaknesses in design and performance have been identified. This article aims to contribute by emphasizing the significance of shock absorption through the supercapacitor (SC) bypassing in DCCBs and assessing a novel approach called SC-based Bypass Technique (SCBT). The proposed technique is thoroughly discussed, offering improvements to overcome the limitations of existing model. The objective is to verify the secure and stable operation of the proposed model in effectively mitigating the bypassed switching effects. By incorporating the SC as a shock absorber, the new design aims to enhance the overall performance and reliability of the M-DCCB.
Control of interlinking converters for DC multi-microgrids
AUTHORS
Jeremy Watson
JOURNAL/CONFERENCE
ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433604
ABSTRACT
In this paper, we consider the control design of interlinking converters in DC multi-microgrids. We present a passivity framework and use this to propose a solution where each ILC satisfies an appropriate passivity condition which leads to stability and scalability of the DC multi-microgrids under reasonable assumptions. We illustrate the practicality of our approach with two examples of various DC-DC converters suitable for interlinking conversion.
Jeremy Watson
JOURNAL/CONFERENCE
ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433604
ABSTRACT
In this paper, we consider the control design of interlinking converters in DC multi-microgrids. We present a passivity framework and use this to propose a solution where each ILC satisfies an appropriate passivity condition which leads to stability and scalability of the DC multi-microgrids under reasonable assumptions. We illustrate the practicality of our approach with two examples of various DC-DC converters suitable for interlinking conversion.
Control of interlinking converters for multi-grids
AUTHORS
Jeremy Watson & Ioannis Lestas
JOURNAL/CONFERENCE
IEEE Trans. Power Systems
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10416262
ABSTRACT
This paper considers the control of AC-AC interlinking converters (ILCs) in a multi-grid network. We overview the control schemes in the literature and propose a passivity framework for the stabilization of multi-grid networks, considering both AC grid-following and AC grid-forming behavior for the ILC connections. We then analyze a range of AC/AC interlinking converter control methods derived from the literature and propose suitable controllers for this purpose including both AC grid-forming and grid-following behavior. The controller we propose is partially grid-forming; in particular, it is based on a combination of a grid-following and a grid-forming converter to improve the stability properties of the network. Simulation results and theoretical analysis confirm that the proposed ILC control designs are appropriate for the multi-grid network.
Jeremy Watson & Ioannis Lestas
JOURNAL/CONFERENCE
IEEE Trans. Power Systems
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10416262
ABSTRACT
This paper considers the control of AC-AC interlinking converters (ILCs) in a multi-grid network. We overview the control schemes in the literature and propose a passivity framework for the stabilization of multi-grid networks, considering both AC grid-following and AC grid-forming behavior for the ILC connections. We then analyze a range of AC/AC interlinking converter control methods derived from the literature and propose suitable controllers for this purpose including both AC grid-forming and grid-following behavior. The controller we propose is partially grid-forming; in particular, it is based on a combination of a grid-following and a grid-forming converter to improve the stability properties of the network. Simulation results and theoretical analysis confirm that the proposed ILC control designs are appropriate for the multi-grid network.
Comparison of energy consumption of an inverter-driven refrigerator under DC operation vs AC operation – Preliminary investigation on DC operability of whiteware
AUTHORS
N. P. Gallage, N. Kularatna, A. Steyn-Ross & D Kularatna-Abeywardana
JOURNAL/CONFERENCE
IEEE-ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433587
ABSTRACT
Energy-efficient whiteware will reduce the power consumption of a household. Reducing the number of power converter stages within a whiteware helps to enhance the efficiency of the system. Modern commercially available inverter-driven whiteware such as a refrigerator, operates internally on a DC bus, allowing direct powering from the DC bus of a renewable energy system. However, the use of an energy storage system is mandatory to buffer the fluctuating nature of renewable energy. This paper presents the comparison of power consumption of a household inverter-driven refrigerator operating from the traditional AC supply, versus a DC supply based on the removal of the front-end rectifier. The refrigerator was also tested for its wider DC operating voltage range so that a supercapacitor module could be used to buffer the fluctuating nature of renewable energy.
N. P. Gallage, N. Kularatna, A. Steyn-Ross & D Kularatna-Abeywardana
JOURNAL/CONFERENCE
IEEE-ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433587
ABSTRACT
Energy-efficient whiteware will reduce the power consumption of a household. Reducing the number of power converter stages within a whiteware helps to enhance the efficiency of the system. Modern commercially available inverter-driven whiteware such as a refrigerator, operates internally on a DC bus, allowing direct powering from the DC bus of a renewable energy system. However, the use of an energy storage system is mandatory to buffer the fluctuating nature of renewable energy. This paper presents the comparison of power consumption of a household inverter-driven refrigerator operating from the traditional AC supply, versus a DC supply based on the removal of the front-end rectifier. The refrigerator was also tested for its wider DC operating voltage range so that a supercapacitor module could be used to buffer the fluctuating nature of renewable energy.
Arc characteristics in multiple pole DC circuit breakers
AUTHORS
C. Dassanayake, N. Kularatna, A. Steyn-Ross, N. Gurusinghe & K. Gunawardane
JOURNAL/CONFERENCE
IEEE-ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433616
ABSTRACT
Due to the absence of zero crossings in a DC current compared to an AC current, DC arc extinguishing is difficult in DC circuit breakers (DCCB). To overcome this difficulty of arc extinguishing, DC circuit breakers are frequently designed and built by series connecting multiple poles of a 3 phase AC circuit breaker. During the mechanical contact opening, the fault current of the DC circuit gradually reduces as the arc path resistance increases with time. The arc can be extinguished quickly if the arc path resistance can be increased quickly. By increasing the series connected switches, the arc path resistance can be increased. This paper presents the arc characteristics of a multiple pole DC circuit breaker based on analytical and experimental approaches.
C. Dassanayake, N. Kularatna, A. Steyn-Ross, N. Gurusinghe & K. Gunawardane
JOURNAL/CONFERENCE
IEEE-ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433616
ABSTRACT
Due to the absence of zero crossings in a DC current compared to an AC current, DC arc extinguishing is difficult in DC circuit breakers (DCCB). To overcome this difficulty of arc extinguishing, DC circuit breakers are frequently designed and built by series connecting multiple poles of a 3 phase AC circuit breaker. During the mechanical contact opening, the fault current of the DC circuit gradually reduces as the arc path resistance increases with time. The arc can be extinguished quickly if the arc path resistance can be increased quickly. By increasing the series connected switches, the arc path resistance can be increased. This paper presents the arc characteristics of a multiple pole DC circuit breaker based on analytical and experimental approaches.
Extending Supercapacitor Assisted Loss Management Approach for Efficiency Improvements in Solar Inverters
AUTHORS
C.A. Naligama, N. Kularatna & A. Steyn-Ross
JOURNAL/CONFERENCE
IEEE-ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433603
ABSTRACT
Renewable energy inverters have several loss components, such as static losses and high frequency switching losses in semiconductors; transformer losses such as copper and core components; and input capacitor losses. For a given power output and an input DC voltage, these losses depend on transistor parameters and transformer specifications in addition to the, voltage stress, rms current in each element. This paper discusses an extension of supercapacitor assisted loss management technique (SCALoM) to reduce the typical losses in solar inverters. Proposed SCA(Supercapacitor assisted)-technique reduces the voltage stress and rms current in the internal components of the inverters. An extensive analysis of the impact of the proposed technique on the power loss components of solar inverters has been carried out in this paper. SCA-inverter arrangement makes it possible to operate the inverters with higher valued voltage sources than their input voltage range and the preliminary experimental implementation and validation of the proposed SCA-inverter technique shows significant efficiency improvement.
C.A. Naligama, N. Kularatna & A. Steyn-Ross
JOURNAL/CONFERENCE
IEEE-ICDCM 2023
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10433603
ABSTRACT
Renewable energy inverters have several loss components, such as static losses and high frequency switching losses in semiconductors; transformer losses such as copper and core components; and input capacitor losses. For a given power output and an input DC voltage, these losses depend on transistor parameters and transformer specifications in addition to the, voltage stress, rms current in each element. This paper discusses an extension of supercapacitor assisted loss management technique (SCALoM) to reduce the typical losses in solar inverters. Proposed SCA(Supercapacitor assisted)-technique reduces the voltage stress and rms current in the internal components of the inverters. An extensive analysis of the impact of the proposed technique on the power loss components of solar inverters has been carried out in this paper. SCA-inverter arrangement makes it possible to operate the inverters with higher valued voltage sources than their input voltage range and the preliminary experimental implementation and validation of the proposed SCA-inverter technique shows significant efficiency improvement.
Book Reviews in IEEE Electrical Insulation Magazine, February 2024
AUTHORS
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE- Electrical Insulation magazine, January/February, Vol 40 No 1
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10381672
ABSTRACT
The following three books are reviewed: Power Grid Resilience Against Natural Disasters (Lei, S., et al; 2022), Practical Partial Discharge Measurement on Electrical Equipment (Stone, G.C., et al; 2023) and Partial Discharges (PD): Detection, Identification and Localization (Pattanadech, N., et al; 2023).
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE- Electrical Insulation magazine, January/February, Vol 40 No 1
ACCEPTED/PUBLISHED DATE
January 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10381672
ABSTRACT
The following three books are reviewed: Power Grid Resilience Against Natural Disasters (Lei, S., et al; 2022), Practical Partial Discharge Measurement on Electrical Equipment (Stone, G.C., et al; 2023) and Partial Discharges (PD): Detection, Identification and Localization (Pattanadech, N., et al; 2023).
Book Reviews in IEEE Electrical Insulation Magazine, April 2024
AUTHORS
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE- Electrical Insulation magazine, March/April, Vol 40 No 2
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10444764
ABSTRACT
The invention of the transistor during the late 1940s had a significant effect on the high-technology systems we enjoy today, and the inventors of the transistor (in its first form called the point contact transistor) won the Nobel prize in 1964. John Bardeen and Walter Brattain's early work followed by the contribution of William Schockley to invent the junction transistor affected the early electronic engineering systems, driving them into the miniaturization path of modern integrated circuit technology. Bardeen is recorded in history as the scientist who won the Nobel prize for the same subject (physics) twice. This book provides a highly readable historic account of the development of the transistors over a quarter century leading into the VLSI technology we see in portable products and consumer electronics today.
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE- Electrical Insulation magazine, March/April, Vol 40 No 2
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10444764
ABSTRACT
The invention of the transistor during the late 1940s had a significant effect on the high-technology systems we enjoy today, and the inventors of the transistor (in its first form called the point contact transistor) won the Nobel prize in 1964. John Bardeen and Walter Brattain's early work followed by the contribution of William Schockley to invent the junction transistor affected the early electronic engineering systems, driving them into the miniaturization path of modern integrated circuit technology. Bardeen is recorded in history as the scientist who won the Nobel prize for the same subject (physics) twice. This book provides a highly readable historic account of the development of the transistors over a quarter century leading into the VLSI technology we see in portable products and consumer electronics today.
Book Reviews in IEEE Electrical Insulation Magazine, JUNE 2024
AUTHORS
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE- Electrical Insulation magazine, May/June, Vol 40 No 3
ACCEPTED/PUBLISHED DATE
April 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10508429
ABSTRACT
Review of three of the latest books related to electrical power systems.
Nihal Kularatna
JOURNAL/CONFERENCE
IEEE- Electrical Insulation magazine, May/June, Vol 40 No 3
ACCEPTED/PUBLISHED DATE
April 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10508429
ABSTRACT
Review of three of the latest books related to electrical power systems.
MULTI-PHASE HYBRID AC-DC UNBALANCED POWER-FLOW TOOL: FEATURES, CAPABILITIES AND CASE STUDIES
AUTHORS
V. Bathini, J. Schipper, R. Mukhedkar, N. R. Watson, N. Nair
PUBLISHED LOCATION
FAN Case Study Report
PUBLISHED DATE
May 2024
ABSTRACT
The shift towards modernised power systems, driven by congestion management and energy transition efforts, has increased reliance on power electronic converter-dominated networks, leading to greater complexity. As the push for net-zero and sustainable energy goals grows, future systems are expected to further depend on converters, demanding advanced tools for effective management. In response, the Ministry of Business, Innovation and Employment (MBIE) of New Zealand sponsors the "Future Architecture of Low-Carbon Networks" (FAN) project, with Work Stream One (WS1) focused on developing simulation tools for hybrid AC-DC networks. This report explores the FAN power-flow tool's features and capabilities through two case studies: simulating the North Island power system for renewable energy network development and examining a benchmarking test system by the International Council on Large Electric Systems (CIGRE). These studies illustrate the tool's effectiveness in addressing evolving power system complexities.
V. Bathini, J. Schipper, R. Mukhedkar, N. R. Watson, N. Nair
PUBLISHED LOCATION
FAN Case Study Report
PUBLISHED DATE
May 2024
ABSTRACT
The shift towards modernised power systems, driven by congestion management and energy transition efforts, has increased reliance on power electronic converter-dominated networks, leading to greater complexity. As the push for net-zero and sustainable energy goals grows, future systems are expected to further depend on converters, demanding advanced tools for effective management. In response, the Ministry of Business, Innovation and Employment (MBIE) of New Zealand sponsors the "Future Architecture of Low-Carbon Networks" (FAN) project, with Work Stream One (WS1) focused on developing simulation tools for hybrid AC-DC networks. This report explores the FAN power-flow tool's features and capabilities through two case studies: simulating the North Island power system for renewable energy network development and examining a benchmarking test system by the International Council on Large Electric Systems (CIGRE). These studies illustrate the tool's effectiveness in addressing evolving power system complexities.
Supercapacitor-Buffered DC-Operable Refrigerators for DC Homes
AUTHORS
Gallage, N.P., Sirimanne, D.C.T., Kularatna, N., Steyn Ross, A.D. & Kularatna-Abeywardana, D.,
JOURNAL/CONFERENCE
IEEE APEC 2024
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10509352
ABSTRACT
Efficiency improvements in whiteware will help reduce the overall power consumption of a household. Modern inverter-driven whiteware, such as refrigerators, operates internally on a DC bus, permitting direct powering from the DC bus of a renewable energy system. However, the fluctuating nature of renewable energy DC sources mandates an energy storage system to increase the reliability of DC operations. In this paper, we present the data related to the conversion of a 230 V, 50 Hz AC operable household refrigerator to operate from a solar DC bus, with a supercapacitor bank forming an integral part of a supercapacitor-assisted (SCA) low frequency DC-DC converter. In addition, experimental results of DC camping refrigerator powered from a solar DC bus and the essential details of the new low-frequency SCA converter are also presented.
Gallage, N.P., Sirimanne, D.C.T., Kularatna, N., Steyn Ross, A.D. & Kularatna-Abeywardana, D.,
JOURNAL/CONFERENCE
IEEE APEC 2024
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10509352
ABSTRACT
Efficiency improvements in whiteware will help reduce the overall power consumption of a household. Modern inverter-driven whiteware, such as refrigerators, operates internally on a DC bus, permitting direct powering from the DC bus of a renewable energy system. However, the fluctuating nature of renewable energy DC sources mandates an energy storage system to increase the reliability of DC operations. In this paper, we present the data related to the conversion of a 230 V, 50 Hz AC operable household refrigerator to operate from a solar DC bus, with a supercapacitor bank forming an integral part of a supercapacitor-assisted (SCA) low frequency DC-DC converter. In addition, experimental results of DC camping refrigerator powered from a solar DC bus and the essential details of the new low-frequency SCA converter are also presented.
A Supercapacitor Assisted Technique for Reducing Losses in the Input Loop of an Inverter System for Solar PV Applications
AUTHORS
Naligama, C.A., Kularatna, N. & Steyn-Ross, A.D.,
JOURNAL/CONFERENCE
IEEE APEC 2024
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10509345
ABSTRACT
This paper presents a method of using supercapacitor modules in the input loop, to reduce the input losses of a typical inverter system used in solar applications. It is an extension of the supercapacitor-assisted loss management principle (SCALoM), where supercapacitors act as lossless droppers and energy buffers at the input end with a very low frequency switching scheme with reduced dynamic losses in switches compared to switched capacitor-inverter systems. The technique uses a set of micro-inverters, with the same total power capability as a single inverter, combined with a set of supercapacitor banks switching at a low frequency to reduce the voltage stress and rms current through the H-bridge input stages of the inverters, enhancing the end-to-end efficiency of the overall system. The proposed technique does not require a re-design of the commercially available inverters and adds DC-UPS capability to the system. Preliminary experimental results of the SCA(super capacitor assisted) two-inverter arrangement show stable transient and steady state operations, and the system is up to 2.2% efficient compared to a single central inverter arrangement. With the proposed SCA four-inverter configuration, inverter’s overall power load can be further partitioned, and according to the analytical study further improvements in the overall efficiency can be achieved over the SCA two-inverter arrangement.
Naligama, C.A., Kularatna, N. & Steyn-Ross, A.D.,
JOURNAL/CONFERENCE
IEEE APEC 2024
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10509345
ABSTRACT
This paper presents a method of using supercapacitor modules in the input loop, to reduce the input losses of a typical inverter system used in solar applications. It is an extension of the supercapacitor-assisted loss management principle (SCALoM), where supercapacitors act as lossless droppers and energy buffers at the input end with a very low frequency switching scheme with reduced dynamic losses in switches compared to switched capacitor-inverter systems. The technique uses a set of micro-inverters, with the same total power capability as a single inverter, combined with a set of supercapacitor banks switching at a low frequency to reduce the voltage stress and rms current through the H-bridge input stages of the inverters, enhancing the end-to-end efficiency of the overall system. The proposed technique does not require a re-design of the commercially available inverters and adds DC-UPS capability to the system. Preliminary experimental results of the SCA(super capacitor assisted) two-inverter arrangement show stable transient and steady state operations, and the system is up to 2.2% efficient compared to a single central inverter arrangement. With the proposed SCA four-inverter configuration, inverter’s overall power load can be further partitioned, and according to the analytical study further improvements in the overall efficiency can be achieved over the SCA two-inverter arrangement.
Preliminary Experiments Quantifying the Arcing Process in a DC circuit Breaker Development Project
AUTHORS
Dassanayake, C., Kularatna, N., Steyn-Ross, A.D., Gurusinghe, N & Gunawardane, K.
JOURNAL/CONFERENCE
IEEE APEC 2024
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10509082
ABSTRACT
AC circuit breakers are well-established technology today. However, DC circuit breakers (DCCB) are not easy to design and build since there are no zero crossings in a DC power supply. Mechanical and semiconductor switches are the key elements considered under various circuit topologies to design DCCBs. However, mass-produced commercial DCCBs are designed by modifying AC breakers by connecting multiple poles in series and/or using permanent magnets inside the breaker to lower the cost of DCCBs except for special applications such as in the military industry. Some of the major issues behind the DCCB design are fundamentally explained in this research with simple experimental results based on DC arc characteristics. We intend using these experimental observations in a new design approach for DC circuit breakers using supercapacitor energy absorption.
Dassanayake, C., Kularatna, N., Steyn-Ross, A.D., Gurusinghe, N & Gunawardane, K.
JOURNAL/CONFERENCE
IEEE APEC 2024
ACCEPTED/PUBLISHED DATE
February 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10509082
ABSTRACT
AC circuit breakers are well-established technology today. However, DC circuit breakers (DCCB) are not easy to design and build since there are no zero crossings in a DC power supply. Mechanical and semiconductor switches are the key elements considered under various circuit topologies to design DCCBs. However, mass-produced commercial DCCBs are designed by modifying AC breakers by connecting multiple poles in series and/or using permanent magnets inside the breaker to lower the cost of DCCBs except for special applications such as in the military industry. Some of the major issues behind the DCCB design are fundamentally explained in this research with simple experimental results based on DC arc characteristics. We intend using these experimental observations in a new design approach for DC circuit breakers using supercapacitor energy absorption.
Complex Domain Analysis Based Fault Detection in VSC Interfaced Multi-terminal LVDC System
AUTHORS
D Li, A Ukil, G Li
JOURNAL/CONFERENCE
IEEE Transactions on Industrial Informatics, 2024
ACCEPTED/PUBLISHED DATE
March 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10472725
ABSTRACT
In voltage source converter-based low-voltage dc systems (LVDC), the fault current of the dc-link capacitor is considerably high and destructive to system infrastructure. It is necessary to develop effective fault detection methods with sufficient sensitivity and accuracy. To achieve these targets, a complex domain analysis-based fault detection method is proposed in this article. Specifically, the proposed method first fits the transient current into a linear combination of exponential functions, which is solved in the Z-domain-based on the Padé approximation. Second, exponents of the fitted function are projected into the complex plane. A state circle centered on the origin is defined on the complex plane to detect dc faults according to the position of projection points relative to the state circle. The proposed method can differentiate several typical situations via theoretical analysis, including fault line transients, healthy line transients, and load switching. The performance of proposed method is validated with an experimental multiterminal LVDC system to reveal its effective performance compared with present frequency domain based methods, including the wavelet transform, the short-time Fourier transform, the S transform, and the Hilbert–Huang transform.
D Li, A Ukil, G Li
JOURNAL/CONFERENCE
IEEE Transactions on Industrial Informatics, 2024
ACCEPTED/PUBLISHED DATE
March 2024
PUBLISHED LOCATION
https://ieeexplore.ieee.org/document/10472725
ABSTRACT
In voltage source converter-based low-voltage dc systems (LVDC), the fault current of the dc-link capacitor is considerably high and destructive to system infrastructure. It is necessary to develop effective fault detection methods with sufficient sensitivity and accuracy. To achieve these targets, a complex domain analysis-based fault detection method is proposed in this article. Specifically, the proposed method first fits the transient current into a linear combination of exponential functions, which is solved in the Z-domain-based on the Padé approximation. Second, exponents of the fitted function are projected into the complex plane. A state circle centered on the origin is defined on the complex plane to detect dc faults according to the position of projection points relative to the state circle. The proposed method can differentiate several typical situations via theoretical analysis, including fault line transients, healthy line transients, and load switching. The performance of proposed method is validated with an experimental multiterminal LVDC system to reveal its effective performance compared with present frequency domain based methods, including the wavelet transform, the short-time Fourier transform, the S transform, and the Hilbert–Huang transform.
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