Fault tolerant control of MMC with redundant submodules based on carrier phase shift modulation

Modular multilevel converter (MMC) is regarded as one of the most promising topologies for the high-voltage high-power applications. However, reliability is one of the most important challenges for MMC which is composed of a large number of power electronics sub-modules (SMs). In order to increase the system reliability, redundant SMs are often utilized. A strategy is proposed in this paper to implement the control of MMC with redundant SMs based on the carrier phase shift modulation. A rotating sliding choice box is adopted to select the working SMs and phase displacements in operation, which enables the equal burden of each SM. The failed SMs will be deleted from the selecting options, which guarantees the fault tolerant control. Simulations and experiments based on a 5-kW downscaled MMC hardware have verified the strategy.