Arm Current Overshoot Reduction for Submodule Open-circuit Fault Reconfiguration in Modular Multilevel Converters

Modular multilevel converters (MMC) are popular for high-voltage, high-power electric energy conversion. To improve the reliability of MMCs, fault diagnosis and tolerant control have been studied by many researchers. Fault reconfiguration, one important step of the fault tolerant control, has become a challenge, especially under high-voltage operation. Arm current overshoot occurs during the reconfiguration if the MMC does not provide redundant submodules (SMs). Existing publications focus on the fault detection and localization. This work investigates the reconfiguration and proposes a suppression control strategy for the overcurrent. The strategy does not require redundant SMs. The proposed method is simulated in Matlab/Simulink and validated by experiments based on a three-phase MMC using an RL load.