Control strategies and reconfiguration of four-leg inverter PMSM drives in case of single-phase open-circuit faults

This paper deals with control strategies and reconfiguration needed to maintain PMSM drives in operation after a fault leading to a single-phase open circuit has occurred. The considered drive is composed of a three-phase star-connected machine and a four-leg voltage-source inverter, the fourth leg being permanently connected to the neutral point of the machine. We investigate different current and voltage control methods: hysteresis control in the abcn natural reference frame and in the dq0 synchronous reference frame and PI control in the dq0 synchronous reference frame. The methods are compared considering as criteria: the ease of implementation and reconfiguration and the performance before and after a fault such as the value of the torque ripple, the behaviour during transients and robustness against parameter variation.