Fault-Tolerant Strategy with Reduced Transient Torque Pulsations for SiC MOSFET-Based Soft Starter

A fault-tolerant strategy is proposed in this paper for the soft start of an inductor motor using a fully-controlled power semiconductor-based soft starter when it experiences a short-circuit switch fault. The proposed strategy aims to reduce transient torque pulsations, balance and lower inrush current without incurring extra hardware costs, thereby enhancing the reliability and tolerant capability of the soft starter system. Initially, the fault-tolerant soft start modulation in the event of a short-circuit switch fault is presented. Subsequently, a mathematical analysis is introduced to guide the selection of initial firing angles for the healthy phases in the context of a short-circuit switch fault. Additionally, a small-signal model is established, and system stability is verified based on a closed-loop fault-tolerant control system. Finally, simulation and experimental results validate the effectiveness of the proposed fault-tolerant strategy in the fully-controlled power semiconductor-based soft starter system. The balanced inrush current decreases by approximately 13.5%, and the transient torque pulsations decrease by around 16% compared to the soft start method without employing the proposed fault-tolerant strategy.