In wireless power transfer system, impedance matching circuits are usually used to match the impedance between actual load and the optimal load, to achieve the maximum transfer efficiency(coil to coil efficiency). It is easily to design impedance matching circuit parameters for linear load. However, the load is always the rectifier one in many applications. The equivalent impedance of rectifier load is complex impedance, which is affected not only by itself, but also by pre-stage circuit, such as impedance matching circuit parameters. It is hard to calculate the equivalent impedance of rectifier load directly to design the impedance matching circuit parameters. This paper investigates the LCC impedance matching design method for secondary side under rectifier load. Firstly, the transfer efficiency characteristic under rectifier load is studied, and the equivalent impedance is analyzed according to transfer efficiency. Then the impedance calculation method of secondary side under rectifier load is derived via formula derivation and Fourier series theory, and the LCC circuit parameters design method is proposed. Lastly, a wireless charging system for electric vehicle is established to verify the method that can transfer 3.3 kW power over 20 cm distance with 92.7% system efficiency(end to end efficiency).

The selection of an appropriate modulation scheme plays a vital role to assure the performance of multilevel inverters. Space vector pulse width modulation(SVPWM) is more efficient among all other pulse width modulation(PWM) techniques due to its key characteristics like better DC voltage utilization, switching losses reduction and easiness in digital implementation. The conventional SVPWM scheme presents some computational complexities due to redundant switching states and large number of space vectors. This paper summarizes five different SVPWM techniques for multilevel inverters which are α-β frame, g-h frame, K-L frame, α'-β' frame and SVPWM based on imaginary coordinate system. g-h frame and K-L frame are based on 60° and 120° coordinates system respectively. To compare the result of these SVPWM schemes, the complex calculations of conventional SVP-WM are converted into simplified line voltages form. The comparison results validate all the SVPWM techniques, but the SVPWM based on imaginary coordinate is found more simple in duty ratio calculations, easier to understand and provides a better control for zero-sequence component for any level of inverter.

Full power scale back-to-back power converter PMSG wind turbine system, with direct-drive configuration, is an attractive solution, particularly for off-shore wind energy applications. For such systems,(nonlinear) direct control, which requires neither a modulation process nor cascaded linear controllers, but will operate the system at very high control dynamics, is a very promising control class. In this work, we reviewed and experimentally assessed the classical(C-), the duty-optimal(DO-), the ripple-reduced(RR-) and the multi-vector direct model predictive torque control(MV-DMPTC) solutions to deal with the generator side control of grid-tied full power scale back-to-back power converter PMSG wind turbine systems. Their theoretical background, realizations and control performances are presented and discussed. The realizations and experimental assessments of all the discussed control approaches are carried out with a fully FPGA based real-time controller, at a lab-constructed test-bench. The resource usage and implementation complexity are provided. Comprehensive evaluation results are given at the end.

The physical integration of power electronics and electric machines to form integrated motor drives(IMDs) elim-inates the need for special enclosures and connecting cables in order to achieve mass, volume, and cost savings. The objective of this paper is to examine the future of integrated motor drive tech-nology by first reviewing the history of IMD products from the 1960s to today, highlighting both the reasons for their success as well the significant technical obstacles that they had to overcome. Special attention is directed to the application of IMD technology to electric vehicle traction motor drives during the past 15 years. A long-term vision for IMDs is presented that calls for embedding the drive electronics directly inside the machine enclosure. In keeping with this vision, wide-bandgap(WBG) power semiconduc-tor switches(SiC and GaN) offer exciting prospects for shrinking the size of power converters and simplifying their cooling require-ments. New concepts for applying this WBG technology to IMDs are introduced, including revived interest in PWM current-source inverters. In the concluding section, a variety of other promising technologies are introduced that will be critical to realizing the full potential of integrated motor drives.

Switching-mode AC/DC converters are widely used in modern power supplies for computers, data centers and tele-communication equipment. Achieving Power Factor Correction (PFC) and high efficiency are the two most important require-ments. In many cases, high power density is also of tremendous interest. Both power efficiency and power density are greatly influenced by the power devices, the topology and the control used. Compared with conventional Si power MOSFET and Si su-per-junction MOSFET, the newly introduced 600 V GaN devices not only eliminate the reverser recovery, but also have much lower switching and driving losses. These excellent properties enable the emergence of the totem-pole bridgeless AC/DC converter as the next generation preferred solution for PFC instead of the state-of-the art Si-based boost PFC. In this paper, the key technologies and designs for both hard-switching and soft-switching GaN totem-pole PFC are reviewed and the key performance metrics are compared. A soft switching, 3.2 kW totem-pole PFC prototype with 99% efficiency and 130 W/inch3 power density has been achieved in the author’s group as a proof of the concept. Based on the power density comparison, the high frequency soft-switching GaN totem-pole PFC is the preferred choice to achieve both high efficiency and high power density at the same time.

Silicon-Carbide(SiC) devices with superior performance over traditional silicon power devices have become the prime candidates for future high-performance power electronics energy conversion. Traditional device packaging becomes a limiting factor in fully realizing the benefits offered by SiC power devices, and thus, improved and advanced packaging structures are required to bridge the gap between SiC devices and their applications. This paper provides a review of the state-of-art advanced module packaging technologies for SiC devices with the focuses on module layout, packaging material system, and module integration trend, and links these packaging advancements to their impacts on the SiC device performances. Through this review, the paper discusses main challenges and potential solutions for SiC modules, which is critical for future SiC applications.

The emergence of wide bandgap power semiconductor devices has opened the possibilities of improved electrical performance and power density. Advanced research into wide band-gap power electronics also includes advances in integrated circuit design, semiconductor device modeling, 3D electronic packaging, and computer-aided design of wide bandgap based electronics. These emerging trends are described along with some early results indicating the additional improvements possible in power density. Operation at extreme temperatures also becomes more feasible.

WITH this editorial, we sincerely welcome our readers to the brand-new publication — CPSS Transactions on Power Electronics and Applications(CPSS TPEA). It is sponsored and published by China Power Supply Society (CPSS) and technically co-sponsored by IEEE Power Electronics Society(IEEE PELS). CPSS was founded in 1983 and has been the only top-level national academic society in China that solely focuses on the power supply/power electronics area. In the past 30-plus years CPSS has dedicated to provide to its members, researchers, and industry engineers nationwide with high quality services including conferences, technical training, and various publications, and this in deed has helped the society build up its membership rapidly, which now totals up to more than 4000 individual members plus 500 enterprise members. The fast growth of membership in turn compels CPSS to always work out better services for its members, one of which being the open-up of this periodical — a new journal in English language as a publication platform for international academic exchanging. This of course needs to be done through international cooperation, and that’s why IEEE PELS is tightly involved, being the premier international academic organization in power electronics area and one of the fastest growing technical societies of the Institute of Electrical and Electronics Engineers(IEEE). To fulfill the publishing need of the fast-developing power electronics technology worldwide is a more important purpose of launching this new journal. So far there are only 3 or 4 existing journals which are concentrated on power electronics field and have global reputation. For quite a few years people in the international power electronics community have had the feeling that, the existing journals have not even come close to meeting the huge demand of global academic and technology exchanges. E.g., the two existing IEEE power electronics journals, i.e. IEEE Transactions on Power Electronics(IEEE TPEL) and IEEE Journal of Emerging and Selected Topics in Power Electronics(IEEE JESTPE), now publish about 1000 papers a year, which is under a very low paper acceptance rate of around 25%, but still have a back-log of about one year for the newly accepted papers to finally appear in printed form to the public. The addition of this new dedicated journal would be an ideal improvement to fulfill such a tremendous need. The booming of publishing need really is an indicator of how fast power electronics has been developing in recent years. Innovations have been continuously coming up from component(both active device and passive device), module, circuit, converter, to system level, covering different technical aspects as topology or structure conceiving, modeling and analysis, control and design, and measurement and testing. New issues and corresponding solutions have been continuously presenting as the applications of power electronics prevail horizontally in almost every area and corner of human society, from industry, residence and commerce, to transportations, and penetrate vertically through every stage of electric energy flow from generation, transmission and distribution, to utilization, in either a public power grid or a stand-alone power system. I personally believe that we are entering a world with “more electronic” power systems. The prediction around 30 years ago, that power electronics one day will become one of the major poles supporting the human society, is coming into reality. And I also believe, that power electronics is going to last for long time as an important topic since it is one of the keys to answer a basic question for human society, which is how human can harness energy more effectively and in a manner friendlier to both the user and the environment. Therefore, I assume that there is probably no better fitting as for CPSS TPEA to publish its first few issues under a special topic about the developing trends of power electronics. We have invited a group of leading experts in different areas of power electronics to write survey/review papers or special papers with review/overview nature to some extent. To publish in a timely and regular style, we organize this inaugural Special Issue into different parts. Part 1, 2 and 3 were published in the December issue last year, the March issue and the June issue this year respectively, Part 4 appears in this September issue, and the last part is scheduled for the December issue. In Part 4 we are honored to have 6 invited papers. The first three all address topics tightly related to wide-bandgap devices, from design and packaging to applications. The next two follow up with the state-of-the-arts in the motor drives area, and the last one deals with modulation techniques for multi-level inverters. We begin with a paper on the silicon carbide power electronics design. It is authored by Dr. Alan Mantooth and his research group from the University of Arkansas. It describes recent advances of the research on the SiC-device-based power electronics, covering different aspects like integrated circuit design, semiconductor device modeling, 3D electronic packaging, and computer-aided design. These emerging trends really are leading to additional improvements in power density and more feasible operation at extreme temperatures. The second paper provides a review on the SiC power module packaging. It is written by Dr. Yong Kang and his research group from Huazhong University of Science and Technology. It presents a broad overview of the advanced module packaging techniques for SiC devices from module layout, packaging material system, up to module integration trend. The main challenges and potential solutions for the packaging of SiC modules are discussed. The third paper is about the application of GaN devices to the totem-pole bridgeless AC-DC converter beating the traditional Si-based boost PFC. It is written by Dr. Alex Q. Huang and his research group, who recently moved to the University of Texas at Austin. It reviews the key technologies and designs for both hard-switching and soft-switching GaN totem-pole PFC indicating that the high frequency soft-switching solution is more preferable to achieve both high efficiency and high power density. The fourth paper is written by Dr. Thomas M. Jahns and his research group from the University of Wisconsin-Madison, regarding the physical integration of power electronics and electric machines. The paper examines the future of integrated motor drive(IMD) technology by first reviewing the history of IMD products from the 1960s to today. A long-term vision for IMDs is then presented in detail, showing that wide-bandgap power semiconductor devices and a variety of other promising technologies are critical to realizing the full potential of IMDs. The fifth paper is written by Dr. Ralph Kennel and his research group from the Technical University of Munich, discussing advanced control strategies for direct-drive PMSG wind turbine systems. It reviews and evaluates four control solutions in terms of their theoretical backgrounds, implementation approaches and control performances. The realizations and experimental assessments are also carried out with comprehensive evaluation results included in the end. Last but not least, the sixth paper is written by Dr. Yong-dong Li and his research group from the Tsinghua University in Beijing. The paper summarizes and compares five different space-vector Pulse Width Modulation(SVPWM) techniques for multilevel inverters. It turns out that the technique which the authors call SVPWM based on imaginary coordinate is the simplest in implementation and provides a better control on zero-sequence component than the other four. I’d like to thank the authors of all these 6 invited papers. It’s their high-quality contributions that finally leads to the launching of this new journal. I’d like to thank Dehong Xu, President of CPSS, who in 2015 initiated the idea of publishing the new journal and since then has been persistently supporting my work as the founding Editor-in-Chief. I’d also like to thank Jiaxin Han, Secretary General of CPSS, Jan A. Ferreira, President of IEEE PELS, 2015-2016, Don F. D. Tan, President of IEEE PELS, 2013-2014, and Frede Blaabjerg, IEEE PELS Vice President for Products, 2015-2018, who form the CPSS and IEEE PELS Joint Advisory Committee for our new journal with Dehong Xu and myself. Other IEEE officers and leading staffs like Dushan Borovjevich, PELS President, 2011-2012, Alan Mantooth, PELS President, 2017-2018, Mike Kelly, PELS Executive Director, and Frank Zhao, Director of China Operations, IEEE Beijing Office, just to name a few, also provided continuous support and constructive advices. My earnest thanks also go to the CPSS Editorial Office led by Lei Zhang, Deputy Secretary General of CPSS, for their wonderful editing work. It would not have been possible to create a new journal in such a short time without their efforts. I’d like to finally thank all the members of the Executive Council of CPSS and particularly the leaders of Chinese power electronics industry. They always firmly stand behind CPSS TPEA and ready to help whenever needed.