Research on Fault-Tolerant Control of Cascaded H-Bridge Seven-Level Inverter Based on FPSC

First, an improved fundamental phase-shift compensation (FPSC) method is developed, in order to solve the problem of motor torque fluctuation caused by the unbalanced output current of cascaded H-bridge multilevel inverters (CHB-MLI) in a fault state. The phase and amplitude of the output voltage are compensated at the same time. Hence, the performance of the motor after the fault is consistent with that before the fault. Second, an easy-to-implement three-vector selection method is proposed, aiming at reducing the switching vector selection complexity of CHB-MLI. The voltage vector is standardized. The corresponding synthetic vector is then determined, according to the different positions of the reference voltage vector. Finally, three typical fault states are simulated within Matlab/Simulink to verify the effectiveness of the proposed method.