A Simple Hardware-Based Fault-Tolerant Method for Cascaded H-Bridge Converters

A new fault-tolerant strategy for cascaded H-bridge (CHB) multilevel converters under single-fault conditions is proposed in this study. This approach is not dependent on the type and location of the fault. It uses an auxiliary H-bridge cell to fix the fault and to restore the prefault operating condition. The auxiliary H-bridge cell uses a dc-link capacitor instead of the dc power source to simplify the cell structure and minimize the necessary components. In addition, the capacitance value into the auxiliary cell is calculated using mathematical equations. The auxiliary cell is inserted to the converter after fault detection and bypassing the faulty switch. Furthermore, due to the flexibility of space vector modulation, it is utilized to regulate the capacitor voltage in the fault condition. Finally, simulation and experimental results are presented for a three-phase seven-level system to validate the claims and confirm new method effectiveness.