Torque ripple suppression for open-end multiphase PMSMs operating under open-phase faults

Open-phase faults in multiphase PMSMs could occur either through an electrical failure or by selective isolation of one or a higher number of phase windings. In such cases, post-fault currents are injected into the remaining healthy windings to maintain an average torque. However, considerable torque ripple may be present if the post-fault currents are not properly designed. Accordingly, a generic approach is proposed in this paper for designing post-fault currents including non-fundamental harmonics that lead to maximum post-fault average torque with suppressed torque ripple in open-end multiphase PMSMs. The proposed scheme is not restricted by the number of open-phase faults. In the proposed algorithm, the post-fault currents are parameterized, based on which the instantaneous post-fault torque is exhaustively formulated. An optimization algorithm is then used to obtain the optimal parameters of the post-fault currents. Experimental tests on a prototype open-end five-phase PMSM under different fault scenarios are used validate the torque ripple suppression capability of the proposed approach.