An Octal-Switch Redundant Submodule for MMC to Tolerate Open-Circuit Faults

This paper proposes a fault-tolerant control strategy using an octal-switch redundant submodule to address Insulated Gate Bipolar Transistor (IGBT) open-circuit faults in a modular multilevel converter (MMC). Faults are detected using a residual analysis method, followed by prompt compensation for insufficient voltage. An active fault diagnosis method is subsequently applied to accurately identify the faulty switch location, bypass the affected submodule, and engage redundant modules to maintain converter output, thus achieving fault-tolerant operation for open-circuit faults. The proposed fault-tolerant control method quickly detects faults and identifies their types without requiring additional sensors or complex mathematical models, while ensuring stable operation of the MMC under fault conditions. The effectiveness of the proposed fault-tolerant strategy is validated through simulations