LIU Jinjun received his B.S. and Ph.D. degrees in Electrical Engineering from Xi’an Jiaotong University (XJTU), China in 1992 and 1997 respectively. He then joined the XJTU Electrical Engineering School as a faculty. In 1997 and 1999 respectively he participated in technology and professional training programs at Advanced Technology Laboratories Inc. and at Milwaukee School of Engineering in USA. From 1999 until early 2002, he was with the Center for Power Electronics Systems at 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 10 faculty members and 150 graduate students and is one of the leading power electronics programs in China. He served as an Associate Dean of Electrical Engineering School at XJTU from 2005 to early 2010. He also has served as the Dean for Undergraduate Education at XJTU since 4 years ago.

   Dr. LIU coauthored 3 books, published over 100 technical papers, holds 13 patents, and received several governmental awards at national level or provincial level for scientific or career achievements and the 2006 Delta Scholar Award. His research interests are power quality control, sustainable energy, distributed generation, and utility applications of power electronics, and modeling and control of power electronic circuits and power supply systems.

   Dr. Liu has served as the IEEE PELS Region 10 Liaison for 6 years, and an Associate Editor for the IEEE Transactions on Power Electronics for 6 years. He has been actively involved in the organizing of major IEEE power electronics conferences especially ECCE Asia, as a technical/organizing co-chair or vice chair. He is now chairing the Asian Power Electronics Conferences Coordinating Committee. He is on Board of China Electrotechnical Society and serving as a Vice President of the CES Power Electronics Society. He is also on the Executive Board and serving as a Deputy Secretary-General for the China Power Supply Society.

    A look into the future trends of electric power grids shows that more and more electric power systems with multiple electronic converters will be appearing either in stand-alone mode or grid-connected mode. This eventually will lead to the stability issue for such kind of power systems, which is caused by the dynamic interactions possibly at frequency higher than the line frequency and is quite different from stability issue with conventional electric power grids. To deal with this issue, a review of existing analytical approaches is presented, including conventional power system approach and some power electronics approaches proposed recently. It turns out that the impedance-based approach might be an appropriate analytical approach for such stability issue. A review of existing work of impedance-based approach is then delivered, and the focus is then put on the more recent development along that approach. Specific topics that need further research efforts are also identified.