Prof Sun from Rensselaer Polytechnic Institute (RPI) brought forward a presentation to EE students on Nov 23 this Monday.
According to Prof Sun, recent advances in power electronics had made it possible to develop new power system technologies for a range of applications, such as more-electric aircraft (MEA), electric ships, microgrids, and renewable energy. With hight-frequency switching, power conversion and control devices based on power electronics are more compact, fast-responding and flexible than conventional electromechanical and electromagnetic enegy conversion and control devices. Such fast control, on the other hand, also introduces high-frequency dynamics and creates new instability (including resonance) and control interaction problems that are usually not present in conventional power systems and can not be handled by existing power system theories. His talk presented impedance-based small-signal methods for modeling and analysis of power electronics in power systems. Impedance has been used in stability analysis and control design of dc power electronics in power systems. The principal difficulty in extending the method to ac power systems lies in the fact that an ac system operates along a sinusoidal trajectory and doesn’t have a fixed operation point required for small-signal linearization. Meanwhile, he introduced different methods to overcome this difficulty and compared these with a focus on harmonic linearization and sequence impedance method. The new sequence impedance modles were valid both below and above the synchronous frequency, hence could be used to study instability, resonance and other dynamic problems in the EMT (electrognagnietic transient) frequency range where phasor-based power system stability theory fails, Prof Sun stressed. He finally came to the demonstration of applying the method for PV inverters and wind turbines connected to weak grids as well as offshore wind farms with high-voltage dc transmission. Opportunities to develop advanced control based on the impedance theory were discussed at the end of his talk.
Professor Sun joined the faculty at Rensselaer Polytechnic Institute (RPI) in 2002, where he is currently a Professor in the Department of Electrical, Computer, and Ststems Engineering. He is also the Director of New York State Center for Futre Energy Seystems (CFES). His research interests are in the general area of power electronics and energy conversion, with an emphasis on modeling, control, and different applications including renewable energy, power systems and aerospace.
Professor Sun received his PhD degree from the University of Paderborn in Gernmany. Prior to joining RPI, he spent five years at the Advanced Technology Center of Rockwell Collins working on power electronics for aircraft power systems, and was a Post-Doc Fellow at Georgia Tech from 1996 to 1997. He was th Editor-in-Chief of IEEE Power Electronics Letters from 2008 to January 2014, and is currently th Treasurer of IEEE Power Electronics Soceity (PELS). He is also a member of Administrative Committee of both the IEEE Power Electronics Soceity and the IEEE Systems Council. He received the IEEE PELS Modeling and Control Technical Achievements Award in 2013 for contribution to averaged modeling and ac power electronic system stability. He is a Fellow of IEEE.
