The redundancy fault-tolerant control strategies for modular solid state transformer with DC bus

Solid state transformer (SST) has recently attracted much attention due to its great potential of being applied in the future smart grid. Modular structure is commonly employed in SST, which makes it possible to enhance the reliability of the system by introducing redundancy fault-tolerant control (RFC). This paper presents a general design of 10kV/1MW SST with 800V DC bus, and the various RFC strategies with novel voltage balancing control (VBC) for high-voltage side of the SST are proposed. The proposed RFC strategies can realize the online bypassing of the fault power module. The performance is evaluated and compared with theoretical analysis and simulation results. The proposed strategies will be applied on the full-scale prototype before long.