Zero-Sequence Current Mitigation in Open-End Winding PMSM Drives: A Comparative Study

Permanent Magnet Synchronous Machine (PMSM) drives are widely adopted with the star-connected winding configuration. Conventional PMSM drives are highly efficient, but this topology falls short on various aspects such as fault-tolerance. In applications that require enhanced fault tolerance capabilities, open-end winding (OEW) configuration is gaining popularity with its improved fault tolerance, multilevel characteristics and extended modulation range while introducing the challenge of zero-sequence current (ZSC) path in a non-isolated topology. This zero-sequence path allows non-idealities, such as dead time and machine harmonics, to further affect the system efficiency and losses. Various strategies have been proposed to mitigate ZSC, including adopting proportional-integral (PI) and proportional-resonant (PR) controllers, dead-time compensation and advanced modulation strategies. Each strategy introduces new aspects to the drive scheme. This study presents a comparative study on ZSC mitigation strategies in OEW-PMSM drives. A detailed experimental validation is conducted to assess their effectiveness in suppressing ZSC. The study provides an analysis of the causes of ZSC, insights into practical implementations and offers a guideline for selecting optimal mitigation strategies in OEW-PMSM applications.