Suppression of Zero Sequence Current in a Ninephase Permanent Magnet Synchronous Motor With a Common Dc Bus

The operation of open-winding permanent magnet synchronous motor (OW-PMSM) systems with a common DC bus configuration is inherently affected by zerosequence current (ZSC) circulation. This phenomenon originates from the combined action of two components: the common-mode voltage produced through inverter modulation and the zero-sequence potential generated by permanent magnet flux variations. These elements collectively establish a zero-sequence excitation source that induces parasitic currents within the motor windings, ultimately compromising both operational effectiveness and system reliability in OW-PMSM applications. To solve this problem, this paper put forwards methods to suppress zero-sequence current using both vector control and model predictive control (MPC) while comparing their effectiveness. First, on the basis of vector control, the mathematical model of OW-PMSM and its zero-sequence circuit is established, and a proportional-resonant (PR) controlbased suppression strategy was developed for zero-sequence current mitigation, which controls the zero-sequence component of the output voltage of the inverter through the design of the zero-sequence current closed-loop control system, so as to achieve the purpose of zero-sequence current suppression. Then, a zero-sequence current suppression model is designed based on the model predictive control (MPC) and compared with that of vector control. Subsequently, the proposed zero-sequence current suppression strategy is analyzed for its ability to operate stably under different operating conditions of an open-winding nine-phase PMSM, and finally, the simulation results validated the effectiveness of the proposed strategy.