Tutorial


Tutorial 2Recent Advances in Small-Signal Modeling of Power Electronics Systems
Date/Time24th May, 2021 Monday / 09:00 - 12:00 hrs
SpeakerJinjun Liu, Xi’an Jiaotong University

Abstract

Small-signal modeling is very important to the analysis and control design of electric energy systems. As electric energy systems enter into a new era, they have been experiencing many changes towards future, among which turning into more electronic, i.e. integrating more and more electronic power converters, and incorporating more and more distributed generations are the two major ones. The technical challenges to the small-signal modeling of electric energy systems due to these changes will be discussed in this tutorial, from the view point of the need of both theoretical insights and engineering practices Some of the recent advances in the researches of small-signal modelling of power electronics systems will then be illustrated in more details for both single power converters, such as basic DC-DC converters and 3-phase AC-DC converters, as well as distributed power systems, which are composed of a group of power converters connected in either a DC or 3-phase AC bus and interfacing either energy sources or energy users. Whether, how and in what capacity these newly achieved results have responded to the challenges will be elaborated and commented respectively. The specific issues that the speaker believes are still lacking effective engineering solutions and hopefully would attract more attentions will be identified too.

Duration
3 hours

Outline

1 Developing trends and challenges to modeling

2 Recent advances

    ◼ Single converter

      ◊ High-frequency modeling of DC-DC converters under voltage-mode control

      ◊ Complex transfer functions based analyses for 3-phase AC-DC converters

      ◊ Decoupling control for 3-phase AC-DC converters

◼ DC bus DPS

    ◊ Impedance-based stability criteria for two cascaded subsystems

    ◊ A classification of subsystems based on terminal characteristics and a modification of stability criterion for two cascaded subsystems

    ◊ Stability criteria for two parallel subsystems based on the proposed classification

    ◊ Impedance-based stability criteria for multiple subsystems

    ◊ What if interactions also exist through communications like active current sharing

◼ 3-phase AC bus DPS

    ◊ Impedance-based criterion extended to 3-phase AC system

    ◊ Stability analysis of AC parallel system considering interactions through communications

    ◊ Possible simplifications on Generalized Nyquist Criterion

    ◊ Complex transfer functions based stability analysis for two cascaded three-phase symmetric system

    ◊ Stability analysis of droop-controlled parallel inverters

3 Future demands


Biography



Jinjun Liu received a B.S. degree in industrial automation and a Ph.D. degree in electrical engineering from Xi’an Jiaotong University (XJTU), Xi’an, China, in 1992 and 1997, respectively. He then joined the XJTU Electrical Engineering School as a faculty. From late 1999 to early 2002, he was with the Center for Power Electronics Systems, Virginia Polytechnic Institute and State University, USA, as a Visiting Scholar. In late 2002, he was promoted to a Full Professor and then the Head of the Power Electronics and Renewable Energy Center at XJTU, which now comprises 21 faculty members and over 150 graduate students and carries one of the leading power electronics programs in China. From 2005 to early 2010, he served as an Associate Dean of Electrical Engineering School at XJTU, and from 2009 to early 2015, the Dean for Undergraduate Education of XJTU. He is currently a XJTU Distinguished Professor of Power Electronics. He co-authored 3 books (including one textbook), published over 500 technical papers in peer-reviewed journals and conference proceedings, holds over50 invention patents (China/US/Europe), and delivered for many times plenary keynote speeches and tutorials at IEEE conferences or China national conferences in power electronics area. His research interests include modeling, control, and design methods for power converters and electronified power systems, power quality control and utility applications of power electronics, and micro-grids for sustainable energy and distributed generation.

Dr. Liu received for eighttimes governmental awards at national level or provincial/ministerial level for scientific research/teaching achievements. He also received the 2006 Delta Scholar Award, the 2014 Chang Jiang Scholar Award, the 2014 Outstanding Sci-Tech Worker of the Nation Award, the 2016 State Council Special Subsidy Award, the IEEE Transactions on Power Electronics 2016 Prize Paper Award, and the Nomination Award for the Grand Prize of 2020 Bao Steel Outstanding Teacher Award. He served as the IEEE Power Electronics Society Region 10 Liaison and then China Liaison for 10 years, an Associate Editor for the IEEE TRANSACTIONS ON POWER ELECTRONICS for 13 years, 2015-2019 Executive Vice President and 2020-2021 Vice President for membership of IEEE PELS, and was elevated IEEE Fellow in 2018. He was on the Board of China Electrotechnical Society 2012-2020 and was elected the Vice Presidentin 2013 and the Secretary General in 2018 of the CES Power Electronics Society. Since 2013, he has been the Vice President for International Affairs, China Power Supply Society (CPSS) and since 2016, the inaugural Editor-in-Chief of CPSS Transactions on Power Electronics and Applications. Since 2013, he has been serving as the Vice Chair of the Chinese National Steering Committee for College Electric Power Engineering Programs.

Relevant publications

[1] Xiangpeng Cheng, Jinjun Liu and Zeng Liu, "A Generalized Multifrequency Small-Signal Model for High-Bandwidth Buck Converters Under Constant-Frequency Voltage-Mode Control," in IEEE Transactions on Power Electronics, vol. 35, no. 8, pp. 8186-8199, Aug. 2020

[2] S. Zhou, J. Liu, L. Zhou and Y. Zhang, "DQ Current Control of Voltage Source Converters With a Decoupling Method Based on Preprocessed Reference Current Feed-forward," in IEEE Transactions on Power Electronics, vol. 32, no. 11, pp. 8904-8921, Nov. 2017

[3] Fangcheng Liu, Jinjun Liu, Haodong Zhang, “Generalized Stability Criterion for Multi-module Distributed DC System”, Journal of Power Electronics, 2014,14(1): 143-155

[4] F. Liu, J. Liu, H. Zhang, and D. Xue, "Stability Issues of Z+Z Type Cascade System in Hybrid Energy Storage System (HESS)," IEEE Transactions on Power Electronics, vol. 29, no. 11, pp. 5846- 5859, Nov 2014

[5] F. Liu, J. Liu, H. Zhang, D. Xue, and Q. Dou, "Comprehensive study about stability issues of multimodule distributed system," in International Power Electronics Conference, pp. 3604-3610, 2014

[6] Hao Wang, Jinjun Liu, Dan Hou. Derivation method of output impedance of DC-DC converters paralleled system with active current sharing control for system stability analysis. In: Proceeding of 2010 International Power Electronics Conference (IPEC), Sapporo, Japan, 2010: 213–217

[7] Zeng Liu, Jinjun Liu, Xueyu Hou, et al. Output Impedance Modeling and Stability Prediction of Three-Phase Paralleled Inverters with Master-Slave Sharing Scheme Based on Terminal Characteristics of Individual Inverters [J]. IEEE Transactions on Power Electronics, 2016, 31(7): 5306-5320

[8] Zeng Liu, Jinjun Liu, Weihan Bao, Yalin Zhao. Infinity-norm of Impedance Based Stability Criterion for Three-Phase AC Distributed Power Systems with Constant Power Loads . IEEE Transactions on Power Electronics, 2015, 30(6), 3030-3043

[9] T. Liu, Z. Liu, and J. Liu, “Impedance modeling and stability analysis of the cascaded three-phase symmetric systems using complex transfer functions,” IPEC-Niigata 2018-ECCE Asia, Niigata, Japan, pp. 3176-3181, May, 2018

[10] Z. Liu, J. Liu, D. Boroyevich. Small-signal terminal characteristics modeling of three-phase boost rectifier with variable fundamental frequency. In Proceedings of 31st Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2016, Long Beach, USA, March 20-24, 2016: 739-745

[11] S. Wang, Z. Liu, J. Liu, etc., "Small-Signal Modeling and Stability Prediction of Parallel DroopControlled Inverters based on Terminal Characteristics of Individual Inverters," IEEE Trans. Power Electron., vol. 35, no. 1, pp. 1045-1063, Jan. 2020