Improved Multi-Stage Decoupling Space Vector Modulation for Asymmetrical Multi-Phase PMSM with Series Winding Connection

This study is devoted to developing a unique series-winding drive (SWD) topology, analyzing and implementing its control schemes for asymmetrical multi-phase permanent magnet synchronous motor (PMSM). Proposed SWDs have higher voltage utilization than ordinary wye or delta connection but vary with the number of inverter legs and connection sequence. Also, they have a simpler topology, fewer inverter legs and power modules than the open-end winding drives. The paper selects the typical asymmetrical six-phase (ASP) PMSM as the target. The complex space vector mapping is screened and simplified by unified hexadecimal coding for both 8-leg and 7-leg drives. Given the multiple subspaces in ASP-PMSM, a multi-stage decoupling space vector modulation (MSD SVM) scheme is proposed and improved for SWDs. It incorporates the processes of vector synthetization, cost function minimization, and zero-sequence compensation. Prototype fabrication and control experiments are carried out. Results show that the proposed MSD SVM is applicable to all connection sequences. It can suppress the harmonic current to a quite low level, in both steady-state and dynamic states. Also, the study discusses the current burden of the inverter and provides suggestions.