Algorithm for Fault-Tolerant Operation of Cascaded H-Bridge Multilevel Inverter

This paper presents a fault-tolerance switching technique for operation of a three-phase cascaded H-bridge multilevel inverter topology during internal fault. The MLI has many switches involved during power conditioning, which increases the possibility of fault event occurrence. The most common reliability problem in MLIs are short circuit and open-switch fault in H-bridges during the operation. A quick and precise fault detection-isolation strategy improves the system reliability and also avoids the shutdown and mal operation of the load connected. The proposed algorithm uses the root mean square values of the H-bridge voltages as the diagnostic variable at the time of fault. The fault detection algorithm is simple and can detect the fault location accurately. In addition, the proposed algorithm is able to provide rated balanced output voltage during fault without adding any additional components within one cycle. The performance of the proposed algorithm and closed loop voltage control has been verified in MATLAB/Simulink environment for a three-phase seven level cascaded H-bridge multilevel inverter.