Zero-Sequence Current Suppression Strategy With Reduced Switching Frequency for Open-End Winding PMSM Drives With Common DC BUS

Zero-sequence current (ZSC) is inevitable in the structure of an open-end winding permanent-magnet synchronous machine (OW-PMSM) system with a common dc bus due to the simultaneous existence of the ZSC loop and the zero-sequence voltage (ZSV) caused by the inverters and third electromotive force. To suppress the ZSC, a novel strategy with a reduced switching frequency is proposed in this paper. The main contribution of the proposed method is that the ZSC is suppressed totally with a reduced switching frequency. The duration time of the active voltage vectors is redistributed to generate the reference voltage in a zero-sequence loop, which leads to the suppression of the ZSC. Different from the conventional method, only the active voltage vectors instead of the zero voltage vectors are employed to suppress the ZSC. Consequently, the switching frequency in the modulation process can be reduced. In addition, the effective modulation range of the ZSV is analyzed, which further reveals the relationship among the effective modulation of the ZSV, the modulation index, and the ratio of the third flux linkage component to the fundamental flux linkage component. Finally, the effectiveness of the proposed method is validated by an OW-PMSM experimental setup with a common dc bus. Moreover, the proposed method is experimentally compared with the existing methods.