面向单开关故障的级联H桥多电平逆变器容错策略——实现零基波共模电压

This article proposes an enhanced common-mode voltage (CMV) injection method for fault-tolerant operation of cascaded H-Bridge (CHB) inverters, with the goal of achieving zero fundamental component in the injected CMV in the case of single-switch faults. By eliminating the fundamental component of CMV (FCMV), the suggested method prevents real power return from load to the dc-link of H-bridge cells at low-power factors, which is a critical issue in nonregenerative CHB inverters. The power flow back causes overvoltage in the dc-link capacitors of H-bridge cells in post-fault conditions and ultimately, the converter tripping off. Furthermore, the CMV increases voltage stresses and bearing currents in ac motor loads, and the proposed method reduces the peak-to-peak magnitude of the CMV while providing the maximum possible output voltage. The mentioned features enable safe fault-tolerant operation of the CHB converter across all load power factors, which is not possible with the existing fault-tolerant methods. Simulation results in MATLAB/SIMULINK and experimental validation on a laboratory prototype confirm that the suggested method effectively makes FCMV zero in the case of single-switch faults, offering improved safety and performance in fault-tolerant scenarios.