A Review of Control Methods for PMSM Torque Ripple Reduction

Torque ripple of PMSMs can be reduced in design, but elaborate designs can be costly to manufacture. If an optimized machine design is obtained, performance can be further improved through control. Torque pulsations, more specifically torque ripple in PMSMs, could be decreased by injecting current harmonics on top of the operating currents. With new semiconductor devices that can handle higher switching frequencies, using a technique that injects higher order harmonics is possible. These injected currents can be calculated based on different methods that look at the different sources of ripple. The purpose of this paper is to identify and describe ways to measure or estimate torque ripple, and review control methods, both old and new, that have been proposed to reduce it. The paper provides information to machine designers to be able to further optimize the performance of an otherwise already optimal machine.