Zero-Sequence Current Suppression Strategy With Common-Mode Voltage Control for Open-End Winding PMSM Drives With Common DC Bus

Abstract

The zero-sequence loop inherently exists in the structure of the three-phase open-end winding permanent-magnet synchronous machine (OW-PMSM) system with common dc bus, which provides the circulating path for zero-sequence current (ZSC) and consequently causes the torque ripple and extra system loss. Besides, the common-mode voltage (CMV), which can cause many negative effects, such as the bearing current and the failure of motor bearing, is another concern in the driving system. However, the simultaneous suppression of ZSC and the CMV control of the devices is investigated mainly in the application of the induction machine system and the multiphase OW-PMSM system, whereas it is ignored in the application of the three-phase OW-PMSM system, in which the suppression of ZSC is more complex considering the effect of flux linkage harmonic components. On this basis, this article proposes a strategy that can not only suppress the ZSC, but also eliminate the ripple of CMV in the three-phase OW-PMSM system. In the proposed method, the suppression of ZSC is achieved by synchronously adjusting the duration time of each phase within every control cycle based on the reference voltage of zero-sequence control loop, which can simplify the conventional rearrangement-based scheme. Furthermore, the duration time of each phase is distributed into each switch device of the two inverters, with the principle of eliminating the ripple of CMV. Consequently, both the suppression of ZSC and the CMV control can be achieved easily. Furthermore, the influence of dead time on the CMV control is analyzed, indicating that the CMV control is irrelevant with the dead time. Moreover, the effective modulation range of the proposed technique is analyzed. Finally, the experimental validation is conducted on a three-phase OW-PMSM system with common dc bus.