Research on Switch Fault-tolerant Strategy for Ninephase Rectification System Based on Super Sector Reconstruction

In recent years, multiphase rectifier development has advanced, offering enhanced reliability and control flexibility. However, traditional SVPWM (Space Vector Pulse Width Modulation) can’t be used to compenstae the faulty vector in multiphase generators. To mitigate this, this paper introduces an asymmetric nine-phase rectifier model. It employs phase-shifting control to partition the nine-phase 20° shifted rectifier module into three mutually three-phase modules, enabling smooth dual closed-loop operation and minimizing harmonic content. Additionally, for addressing switching device failures, the paper proposes an SVPWM fault-tolerant strategy. In the event of a single-module switching device failure, a standard SVPWM fault-tolerant strategy is employed. In cases of multiple module switching device failures, vector sector reconstruction expands the 18 sectors of the nine-phase SVPWM vector to 18+2N sectors, optimizing vectors and introducing transitional sectors to mitigate fault impacts. Experimental validation includes a 5V/500A low-voltage high-current output platform under normal conditions, assessing Total Harmonic Distortions (THDs), output DC voltage ripple, input current distortion, and trajectory circles under single-module single-switch and cross-module multi-switch fault scenarios. Results confirm the effectiveness and reliability of the proposed strategy in asymmetric nine-phase rectifier systems with switching device open-circuit faults.