Parallel Operation of Full Power Converters in Permanent-Magnet Direct-Drive Wind Power Generation System

Parallel operation is an effective way to improve the capacity of full power converter in permanent-magnet direct-drive wind power generation system. But it causes the zero-sequence circulating-current (ZSCC), which brings current discrepancy, current waveform distortion, power losses, and electromagnetic interference (EMI), etc. The paper proposes a new topology of full power converters which are composed of n full power converters. The n converters have the same structures and are in parallel with each other. Besides, the average models of the system are analyzed and the fundamental mechanism of ZSCC generation is given. Based on the above analysis, the control strategy of the system is designed. The simulation and experiment results of two parallel full power converters show the feasibility of the proposed theory and control scheme.