A Novel Zero-Sequence Current Elimination PWM Scheme for an Open-Winding PMSM With Common DC Bus

This paper introduces a novel pulsewidth modulation (PWM) scheme for an open-winding permanent magnet synchronous machine (OW-PMSM) driven by dual two-level three-phase inverter with common dc bus, which can effectively deal with the inherent zero-sequence current (ZSC) problem. Based on the conventional symmetrical unipolar double-frequency sinusoidal PWM scheme with an appropriate phase shift, the common mode voltage (CMV) of two inverters remains same and cancel out each other to eliminate the modulated zero-sequence voltage (ZSV) disturbance source. In this case, the double-frequency effect can be retained to reduce the ac side current ripple and suppress both corresponding motor vibration and acoustic noise, which is advantageous to improve the synthetic performance of motor. The dc-bus voltage utilization of the novel PWM scheme is proved to reach the same maximum value comparing to the conventional modulated ZSV elimination scheme. Meanwhile, a zero-sequence controller is designed to suppress ZSC by further adjusting the two CMVs to counteract other zero-sequence disturbance sources. To verify the analysis, the proposed PWM technique associated with the control method is implemented in an OW-PMSM experimental setup to validate the superiority of the proposed method.