Post-fault operation of fault-tolerant inverters for PMSM drives

This paper considers post-fault operation of permanent-magnet synchronous motor drives equipped with a fault-tolerant inverter. In post-fault mode, the faulted phase is isolated and the neutral point is connected either to an additional inverter leg or to the midpoint of the DC bus. Different methods of controlling the neutral point voltage are presented and compared. Furthermore, operation without a position sensor (i.e., sensorless control) is considered and a modification to an estimator previously reported in the literature is proposed in order to take into account the effect of the asymmetry introduced due to the isolation of the faulted phase in post-fault mode. Simulations and experimental results are provided to support the theory and demonstrate the practical impact of the modifications proposed