Fault tolerant direct torque control of three-phase permanent magnet synchronous motors

The model of three-phase permanent magnet synchronous motor (PMSM) with loss of one phase or loss of one transistor is built and its fault tolerant direct torque control (DTC) is investigated. Extra-leg extraswitch inverter is put to use in the post-fault operation. Two different flux estimators are employed in order to calculate stator flux linkage & their corresponding torque and switching table is kept the same as the case of DTC for the healthy motor. The parameters of PI controller and hysteresis controller are determined by differential evolution algorithm. Dynamic responses of both healthy and unhealthy PMSM DTC system adopting aforementioned two flux estimators are given to compare their performance via simulation and some discussion is presented. The simulation results show the proposed fault tolerant DTC yields satisfactory torque and speed control no matter which one of two flux estimators provided in the paper is employed