Torque Ripple Suppression Method With Reduced Switching Frequency for Open-Winding PMSM Drives With Common DC Bus

Torque ripple caused by zero-sequence current (ZSC) and relatively high switching frequency severely worsens the operating performance of an open-winding permanent-magnet synchronous machine (OW-PMSM) system with common dc bus. In this paper, a novel q-axis current injection method based on the angle-shift-based voltage distribution is proposed for the OW-PMSM system with common dc bus. With the proposed method, torque ripple caused by ZSC can be counteracted by the torque component generated by the injected q-axis current. Meanwhile, the corresponding modulation range is analyzed to investigate the availability of the proposed method. Moreover, in order to reduce the switching frequency, zero vector (111) is no longer necessary to compensate the zero-sequence component and conventional space vector pulsewidth modulation (PWM) with zero vectors (000) and (111) can be simplified. The switching actions in one PWM period can be reduced from 12 to 8. The comparison of losses shows that this strategy can effectively improve the efficiency under both heavy load and high switching frequencies. Finally, the effectiveness of the proposed method is validated through an OW-PMSM experiment with common dc bus.