Non-faulty phases will change and cause additional interference when the traditional redundant fault-tolerant control method is adopted to adjust the faulty phase. In order to reduce the influence of fault protection on non-fault phases and improve the reliability of the multilevel cascaded STATCOM

an optimized redundant fault-tolerant control algorithm is proposed. Based on the equations of star-connected STATCOM

the quantitative relationship between redundancy fault tolerance and neutral point shift is studied and the influence of neutral point shift is analyzed. Then

the optimization of star-chain STATCOM redundant fault-tolerant control algorithm is proposed based on the closed-loop control method of negative sequence current. Finally

the traditional and proposed optimization algorithms are compared through simulation and experiments. The experimental results show that the optimization algorithm can improve the transient performance in the process of redundancy and fault tolerance. The unbalance of the fault transient current will reduce by 2.4%

while the steady-state unbalance will only increase by 1%. The voltage fluctuation of the non-faulty module will drop by 13%. The proposed algorithm can improve the reliability of STATCOM and is more applicable for high-power industrial field with high reliability requirements.