A Hybrid Fault-Tolerant Control Strategy for Three-phase Cascaded Multilevel Inverters Based on Half-bridge Recombination Method

This paper proposed a hybrid fault-tolerant control (HFTC) strategy for three-phase cascaded multilevel inverters based on half-bridge recombination method. A new fault-tolerant topology is designed for the common single and double faults in three-phase cascaded H-bridge multilevel inverters (CHB-MLIs), and the fault-tolerant method is based on the combination of hardware and control. The above faults are classified into three categories, for which an HFTC strategy is developed so that the fault-tolerant process can be completed efficiently. The proposed HFTC strategy can realize the fault-tolerant control of single and double faults at any position; output balanced line voltages under all single and double faults, thus improving the utilization rate of DC voltage. And in most fault cases, it can keep the phase voltage level unchanged, thus restoring the performance of the inverter to the normal working state. Finally, the applicability and superiority of the proposed novel topology and HFTC strategy are verified by the simulation with a cascaded seven-level inverter.