Switch Function Model with the Effects of Commutation Failure for Converter

For converters, commutation failure is one of the mainly problems. An improved model for switch function is proposed in this paper to improve the dynamic phasor model of DC system. The improved model can represent the effect of commutation failure on dynamic phasor model by switch functions. By analyzing the process of valves while commutating, the method to modify the switch functions is proposed. According to the modification, the improved model of switch functions is established by superimposing the three-phase switch function model under normal operation. The improved switch function can represent the effect of commutation failure on the converters. The processes to superimpose the normal switch function represent the physical processes of the converters. Furthermore, it is easy to implement in mathematics. Simulation results show that the proposed model is effect and accurate. By using the proposed switch functions in dynamic phasor model of DC system, the dynamic phasor model of DC system can represent the commutation failure of the converters.