Improved Control Strategy for Fault-Tolerant Flux-Switching Permanent-Magnet Machine Under Short-Circuit Condition

Fault-tolerant flux-switching permanent magnet (FTFSPM) machines are suitable for high-reliability applications owing to their good fault-tolerant capability and relatively high torque density. Under a short-circuit fault, the torque ripple caused by the short-circuit current of the FTFSPM machine affects the steady-state performance of the system; in addition, the traditional proportional-integral (PI) controller of the speed loop can hardly guarantee the optimal dynamic performance of the speed. In this study, to solve these two problems, an improved control strategy that can offer two improvements for the FTFSPM machine under the short-circuit condition is investigated. As the first improvement, on the basis of analysis of the torque ripple caused by the short-circuit current, the feed-forward control is employed to reduce the torque ripple. As the second improvement, on the basis of analysis of the influence of the speed loop PI parameters on the system dynamic performance, a torque integral balance-control method is proposed. This algorithm can make the speed and the electromagnetic torque converge simultaneously after only one adjustment of the speed. Thus, the best possible dynamic response for the speed can be achieved. Experimental results verify the correctness and effectiveness of the improved control strategy.