Guest editorial: Modelling, methodologies and control techniques of DC/AC power conversion topologies for small‐ and large‐scale photovoltaic power systems (2021)

Photovoltaic (PV) power generation has great potential to meet a majority of the global energy demand. The exploitation of solar PV energy is expected to increase further in the near future. To harvest solar energy and to meet the demand, power electronics and PV technologies play a major role. The power converters, especially the DC/AC inverters, are essential components in converting and controlling the PV energy to useful electric energy with high efficiency and reliability. The prior-art topologies and control techniques have found acceptance in various industries. This special issue aims to collect articles discussing high-efficiency DC/AC inverter circuit topologies with high power quality and novel control techniques that are highly flexible and less complex. Development and analysis of new power converter topologies. Highly efficient and reliable grid-tied PV systems. High-performance PV systems with advanced control techniques. This special issue includes a review article on single-stage boost inverter structure by Sriramalakshmi et al. The review paper provides the comprehensive topological analysis of various single-stage boost inverters. Various performance indices like voltage stress, number of passive elements, voltage and efficiency are discussed. A new switched capacitor topology with voltage boosting and reduced component count is presented by Bin Arif et al. The topology has a dual-DC source with three capacitors, and modulation strategy and capacitor voltage balancing are discussed. A maximum of 4.85% of total harmonic distortion (THD) is reported. Deliri-Khatoonabad et al. discuss a diamond-shaped high step-up switched-capacitor inverter circuit with reduced voltage stress on the switch. The proposed topology generates a 17-level stepped waveform with a maximum output voltage gain of eight times higher than the source voltage. The total voltage stress on the switches is reduced, which leads to a reduction in the cost of the system. Access full paper using following link: https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/pel2.12111. Kumari et al. examine the new transformerless inverter topology for grid-tied PV applications. The proposed topology has the common ground that suppresses the leakage current and presents the analysis of common mode behaviour. The detailed loss and temperature analysis are discussed. Access full paper using following link: https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/pel2.12041. Shah and Singh address the harmonic compensation strategy for a 3-φ grid-tied solar energy conversion system with a leakage current attenuation feature. A novel algorithm is introduced to mitigate the harmonics in grid current. Also, the generalized integrator-based approach is introduced to ensure the harmonics suppression, power factor correction and leakage current alleviation. Finally, the grid current complies with IEEE std. 519 and the real-time controller-based results are discussed. A new topology of single-phase transformerless inverters, which can be tied to the local grid as a low-scaled AC module system, is proposed by Barzegarkhoo et al. In order to inject a tightly controlled AC current into the grid, an adaptive hysteresis current controller scheme is discussed. A complete theoretical analysis, comparative study and the relevant experimental results are presented. Jalan et al. introduce a novel active current co-efficient extraction (ACCE)-based control method for a three-phase grid-interfaced voltage source inverter (VSI). The proposed ACCE uses minimal mathematical operators to improve computational effectiveness. The proposed structure effectively confronts the various power quality challenges while injecting the active power into the utility grid, and the results are investigated. The intermittent nature of PV arrays introduces a power unbalance in the circuit. Elsanabary et al. propose an energy balancing strategy for the grid-connected modular multilevel converters (MMC)-based PV system to balance the power in the circuit. The energy balance has been achieved by controlling the internal leg current to inject the 3-φ balanced current to the grid, and low THD is reported. Mishra and Singh discuss the development of an efficient and reliable solar PV-fed water pump with a battery energy storage (BES). New control logic for BES is developed, which supports supply of water in all conditions. The control logic significantly improved the overall response of the system, and the performance of the presented scheme is examined and the results are discussed. Access full paper using following link: https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/pel2.12084. A novel control strategy based on sliding mode control for the single-stage boost inverter is proposed by Mohammad Hassani and Gholizade Narm. The main idea of this work is a combination of current-mode control and a new type of dynamic sliding mode control to improve the system's response in different scenarios. Furthermore, the proposed system has a fast and chattering-free response, provides an appropriate steady-state error, good THD, and its implementation is very simple. The comparison with conventional sliding mode control, simulations and laboratory experiments results report the proposed method's effectiveness. The commercial solar PV plant (SPVP), and its integration into the low voltage network, is presented by Modi and Singh. The SPVP has a multi-functional operational capability. It directly feeds to the loads and the AC network with the power quality requirement as per the IEEE std. 519. The SPVP minimizes the line losses in the AC network by recouping the load reactive power requirement locally. An adaptive filter technique based on the maximum correntropy criterion is used for the power quality improvement (PQI). The hardware prototype mode was developed, and results are validated. Thummalagunta et al. introduce a new hybrid quasi-switched boost multi-level-inverter circuit integrated with a reduced switch. Their paper presents a high gain and single-stage power conversion with low device stress, and the extension of the proposed is also presented. A control scheme is presented to ensure the grid operation, which provides a reliable electrical supply to the critical local loads. The proposed inverter has robustness and flexibility of control, making it more suitable for residential rooftop PV generation. A 500 W laboratory prototype and experimental results are reported. Access full paper using following link: https://ietresearch.onlinelibrary.wiley.com/doi/10.1049/pel2.12079. A sparse quaternion-valued minimization (SQVM) based control technique of a two-stage grid supportive PV power system with power conditioning capabilities is proposed by Kumar et al. A new algorithm is used to mitigate the grid side converter, and it provides the reactive power compensation at the point of common coupling (PCC). Furthermore, the control offers to mitigate the DC offset error, harmonics current and improve the system's frequency response. Overall, the system loss is minimized by the incorporation of DC-link voltage in the control loop. The operation and control of the system topology are validated experimentally under various scenarios, and the results are discussed. Wang et al. investigate the soft switching of the isolated three-port DC/DC converter topology for DC electric spring (DCES) applications. The boundary conditions are examined to evaluate the circuit parameters influence in zero voltage switching zone. The results are reported for both simulation and experimental. All of the papers selected for this special issue show the further development on the performance of the PV system with various topologies and control techniques of DC/AC power conversion techniques. Remarkably, most of the articles have real-world validation and experimental results. However, many challenges are still open in this field that requires future research attention, such as power density, reliability studies and EMI issues. Future work can help unleash the potential of the DC/AC power conversion for PV applications. Professor Dr Saad Mekhilef is a Charted Engineer (CEng) and Fellow of the Institution of Engineering and Technology (IET), and a Senior Member of the Institute of Electrical and Electronics Engineers (IEEE). He is an Associate Editor of various top journals such as IEEE Transactions on Power Electronics and the Journal of Power Electronics. He is a distinguished professor at the School of Science, Computing and Engineering Technologies, Swinburne University of Technology, Australia and honorary professor at the Department of Electrical Engineering, University of Malaya, Malaysia where he is the director of the Power Electronics and Renewable Energy Research Laboratory (PEARL). He has authored and co-authored more than 400 publications in academic journals and proceedings and five books with more than 29,000 citations. He is frequently invited as an honorary keynote speaker at international conferences, congress, meetings, and symposiums. Prof Mekhilef has been listed by Thomson Reuters (Clarivate Analytics) as one of the Highly Cited (Hi.Ci) engineering researchers in the world in 2018, 2019 and 2020. He is actively involved in industrial consultancy for major corporations in power electronics and renewable energy projects. His research interests include power conversion techniques, control of power converters, maximum power point tracking (MPPT), renewable energy, and energy efficiency. Yongheng Yang (SM’17) received the B.Eng. degree in electrical engineering and automation from Northwestern Polytechnical University, China, in 2009 and the Ph.D. degree in energy technology (power electronics and drives) from Aalborg University, Denmark, in 2014. He was a postgraduate student with Southeast University, China, from 2009 to 2011. In 2013, he spent three months as a visiting scholar at Texas A&M University, USA. Since 2014, he has been with the Department of Energy Technology, Aalborg University, where he became a tenured associate professor in 2018. In January 2021, he joined Zhejiang University, China, where he is currently a professor with the Institute of Power Electronics, College of Electrical Engineering. His current research is focused on the grid-integration of photovoltaic systems and control of power converters, in particular, the mechanism and control of grid-forming power converters and systems. Dr Yang was the Chair of the IEEE Denmark Section (2019-2020). He is an Associate Editor for several IEEE Transactions/journals and is a Deputy Editor for IET Renewable Power Generation for Solar Photovoltaic Systems. He was the recipient of the 2018 IET Renewable Power Generation Premium Award and an outstanding reviewer for IEEE Transactions on Power Electronics in 2018. He was the recipient of the 2021 Richard M. Bass Outstanding Young Power Electronics Engineer Award from the IEEE Power Electronics Society. In addition, he has received two IEEE Best Paper Awards. Dr Yang was named on the list of the World's Top 2% Most-cited Scientists (both in a single-year and the entire career) by Standard University in 2020. He is currently the Secretary of the IEEE Power Electronics Society Technical Committee on Sustainable Energy Systems. Yam P Siwakoti received the B.Tech. degree in electrical engineering from the National Institute of Technology, India, in 2005, the M.E. degree in electrical power engineering from the Norwegian University of Science and Technology, Norway, and Kathmandu University, Nepal, in 2010, and the Ph.D. degree in electronic engineering from Macquarie University, Australia, in 2014. He was a postdoctoral fellow at the Department of Energy Technology, Aalborg University, Denmark from 2014–2016 and a visiting scientist at the Fraunhofer Institute for Solar Energy Systems, Germany from 2017–2018. He is also a recipient of the prestigious Green Talent Award from the Federal Ministry of Education and Research, Germany in 2016. Currently he is a senior lecturer in the Faculty of Engineering and Information Technology, University of Technology Sydney, Australia. He serves as an Associate Editor of three major journals of IEEE (IEEE Transactions on Power Electronics, IEEE Transactions on Industrial Electronics and IEEE Journal of Emerging and Selected Topics in Power Electronics) and IET Power Electronics. Chi-Seng Lam (Senior Member, IEEE) received the Ph.D. degree in electrical and electronics engineering from the University of Macau (UM), Macau, China, in 2012. He completed the Clare Hall Study Programme at the University of Cambridge, U.K., in 2019. In 2013, he was a postdoctoral fellow with The Hong Kong Polytechnic University, Hong Kong. He is currently an associate professor with the State Key Laboratory of Analog and Mixed-Signal VLSI and the Institute of Microelectronics, UM, and also with the Department of Electrical and Computer Engineering, Faculty of Science and Technology, UM. He has coauthored or co-edited four books and more than 120 technical journals and conference papers. He holds four U.S. and three Chinese patents. His research interests include power quality compensators, renewable energy generation, power management integrated circuits, and wireless power transfer. He currently serves as an Associate Editor for IEEE Transactions on Industrial Electronics, the IEEE Open Journal of the Industrial Electronics Society and IEEE Access. Jagabar Sathik Mohamed Ali received the BE degree in electronics and communication engineering from Madurai Kamarajar University, India, in 2002, and the ME and PhD degrees from the Faculty of Electrical Engineering, Anna University, India in 2004 and 2016, respectively. He is currently working as an associate professor in the Department of Electrical and Electronics Engineering, SRM Institute of Science and Technology, India and also as a postdoctoral fellow with the Renewable Energy Lab, College of Engineering, Prince Sultan University, Saudi Arabia. He is a consultant for various power electronics companies for the design of power electronics converters. He has authored more than 50 publications in international journals, conference proceedings and two published patents. His current research interests include multilevel inverters, grid-connected inverters, and power electronics converters and their applications to renewable energy systems. He is the recipient of the Research Excellence Award 2017 from Indus Foundation Hyderabad, India and he is also the receipt of a certificate of recognition for publication in the year of 2019 and 2020 under IEEE-Madras Section.