A Fault Compensation Scheme for Cascaded H-Bridge Inverter With Reduced Common Mode Voltage

In this article, a common mode voltage (CMV) injection method is proposed to tolerate cell failure for cascaded H-bridge (CHB) inverters. The main purpose of CMV injection is to balance the unequal line-to-line voltages of the inverter without overmodulation when the faulty cells are bypassed. As any injected CMV can interfere with load and inverter proper operation, the proposed fault-tolerant method aims to reduce the peak value and the fundamental harmonic of the injected CMV to minimize its impact on the load and inverter functionality. Also, the proposed method provides features such as simplicity, maximum possible line-to-line voltage, fast real-time calculations, and supporting all faulty cases. The proposed method is evaluated by simulation and experimental results obtained from an 11-level CHB converter.