The Doubly Fed Induction Generator (DFIG) wind energy conversion system (WECS) is widely accepted in today’s wind energy industry. The DFIG is essentially a wound-rotor induction generator, where its rotor circuit is connected to the grid through power converters. With variable speed operation to harvest the maximum power from the wind, the DFIG operates in three different modes: super-synchronous, synchronous, and sub-synchronous modes, and the power flow in the rotor circuit is bidirectional. The DFIG is also required to deliver an adjustable reactive power to the grid. These functions and requirements are all achieved by the rotor-side converter, which makes the control analysis of DFIG wind energy system quite complex.

In this presentation, a simple RL equivalent impedance is proposed to emulate the operation of the rotor-side converter. The RL impedance can be integrated into the conventional steady-state equivalent circuit of the induction machine, based on which a comprehensive analysis of the DFIG WECS can be easily performed under any operating conditions. The principle and procedures for determining the RL equivalent parameters are given, and steady-state analysis of the DFIG wind energy system is provided with numerical examples. In addition, a Stator Voltage Oriented Control (SVOC) for the DFIG WECS is presented, and system dynamic performance is investigated by simulation and experiments.

 

Reference: B. Wu, Y. Lang, N. Zargari and S. Kouro, “Power Conversion and Control of Wind Energy Systems,’ Wiley–IEEE Press, June 2011. 

 

Bin Wu received his Ph.D. degree in electrical and computer engineering from the University of Toronto, Canada, in 1993. After being with Rockwell Automation Canada as a Senior Engineer, he joined Ryerson University, Toronto, Canada, where he is currently a Professor and NSERC/Rockwell Industrial Research Chair in Power Electronics and Electric Drives. Dr. Wu has published more than 250 technical papers, authored two Wiley/IEEE-Press books, and holds more than 20 issued/pending patents in the area of power conversion, advanced controls, adjustable-speed drives and renewable energy systems.

Dr. Wu received the Gold Medal of the Governor General of Canada, the Premier’s Research Excellence Award, Ryerson Distinguished Scholar Award, Ryerson Research Chair Award and the NSERC Synergy Award for Innovation. He is a fellow of Institute of Electrical & Electronics Engineers (IEEE), Engineering Institute of Canada (EIC), and Canadian Academy of Engineering (CAE). Dr. Wu is an Associate Editor of IEEE Transactions on Power Electronics and IEEE Canadian Review.