Torque Ripple Suppression for Open-End Multi-Phase 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, postfault 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 nonfundamental 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.