Optimization of voltage zero crossing switching strategy for 5L-ANPC inverter considering snubber circuit

The topology of 5L-ANPC (five-level active-neutral-point-clamped) converter has a simple structure, which can be directly supplied by the common direct current bus, and is easy to realize energy feedback. It is very suitable for the 5~10 kV propulsion variable frequency speed regulation in the integrated power system of ship. The topology and basic working principle of 5L-ANPC were briefly introduced. Based on the analysis of four commutation circuits of 5L-ANPC topology and considering the assembly and adaptability of the snubber circuit, a single capacitor integrated snubber circuit was designed. The over-voltage problem of internal switch in 5L-ANPC topology with snubber circuit using traditional voltage zero crossing strategy was analyzed and an improved output voltage zero crossing switching strategy was proposed, which ensure the safety of switching device and avoid the abnormal voltage jump. The effectiveness and correctness of the improved strategy are verified by simulation and experiment.