The input stage, isolation stage and output stage of modular multilevel converter (MMC) based power electronic transformer contain a large number of IGBTs and freewheeling diodes. The circuit topologies and fault characteristics of IGBTs and freewheeling diodes under open-circuit and short-circuit faults are analyzed. According to the characteristics of each stage of power electronic transformer, the corresponding redundancy methods are designed to help the system to achieve fault ride-through. The input stage adopts sub-module spinning reserve redundancy. The dual active bridge of isolation stage is improved to be used for the isolation of the single stage double active bridge by means of parallel half bridge module in the series capacitors, on this basis, spinning reserve redundancy is configured for the isolation stage. The output stage inverter adopts bridge leg redundancy. Finally, the effectiveness of the proposed fault ride-through strategy is verified though simulation.