A Fault-Tolerant Control Method Based on Switching Sequences Reconstruction for Cascaded Three-Level Rectifiers

The cascaded three-level rectifiers contain a large number of switches, which increases the possibility of fault event occurrence. The subsequent effects of fault not only reflect the influence on the output of AC and DC side, but also leave hidden risks for the stable operation of the system. A fault tolerant method based on modulation reconstruction is proposed when the open circuit fault occurs in neutral-point (NP) switches. In this fault-tolerant method, the rectifiers recover from the fault by reconstructing the switching sequences in the fault interval, and the module with the open circuit fault can still transmit most of the power rating under the condition of unbalanced load. The power quality of the AC side is effectively guaranteed when the fault occurs, and ensures the stable operation of the system in case of load imbalance. Finally, the feasibility and correctness of proposed method is verified by simulation results.