Fault-tolerant control strategy for single-phase open-circuit faults in permanent magnet synchronous machine

Purpose Aiming at the single-phase open-circuit faults occurring in permanent magnet synchronous machine (PMSM) drive systems, this paper aims to propose a single-phase open-circuit fault-tolerant control scheme for PMSM. Design/methodology/approach As the PMSM drive system operates over a long period of time, the inverter or the armature winding is susceptible to open-circuit fault, which affects the reliability of the system. Fault-tolerance control is an important way to improve the system reliability. First, the fourth-leg fault-tolerant converter is designed according to the single-phase open-circuit fault. Then, the virtual α-β coordinate system is constructed by using the nonfault two phases, and the torque vector expression is obtained. The amplitude and phase angle of the current vector are established with the objectives of keeping the torque unchanged and minimizing the copper loss. Furthermore, the reference currents can be obtained through inverse coordinate transformation and the constraint that sum of three-phase currents is zero for current control. Findings Compared with the traditional vector control strategy, the proposed vector control strategy can reduce the copper loss and torque ripple. The effectiveness of the proposed control strategy is verified by simulation and experiments for a PMSM. Originality/value A virtual α-β coordinate system is established by the nonfaulty phases to fully use the torque output capacity. According to the derived torque output expression in polar coordinate system, the copper loss is reduced by controlling the phase of the current vector, and the torque ripple is reduced by regulating the amplitude of the current vector.