A wind energy conversion system based on full scale VIENNA rectifier and small-scale STATCOM

This paper presents a new configuration for variable speed wind energy conversion system based on squirrel-cage induction generator. A full-scale VIENNA rectifier is utilized to transfer active power and compensate part of reactive current for squirrel-cage induction generator. A small-scale STATCOM is utilized to correct VIENNA rectifier power factor into the extension of -30 degrees to 30 degrees so that VIENNA rectifier can operate well. The proposed configuration is of lower cost compared with traditional SCIG wind energy conversion system with full-scale voltage source converter. In this paper, the proposed configuration is presented and analyzed first. Then rotor flux-oriented control algorithm, VIENNA rectifier modulation principle and STATCOM PQ decoupled control is introduced. Furthermore, operation principle of the whole system and coordinated control strategy of VIENNA rectifier and STATCOM is detailed described. Finally, simulation results are presented which prove the proposed configuration working well in the whole operating range. The current zero-crossing problem of VIENNA rectifier which causes serious harmonics current is also solved through modifying VIENNA rectifier modulation. After the problem solved, simulation results align well with theoretical analysis.