Modeling Of Switch Function Considering Commutation Failure Effects For Converter

With the rapid development of HVDC technology in China, the power grid of China has been the largest and the highest level of voltage AC/DC hybrid transmission system in the world. So, the interaction between AC and DC systems is more prominent. And the stability of power grid is more complex. The strengthening of the interaction between DC systems has also enhanced the risk of the occurrence of continuous commutation failure. Commutation failure is common in converter. To improve the dynamic phasor model of DC system and represent the effect of commutation failure, an advanced model of switch function for converter is proposed in this paper. According to the various states of the converter valves when the commutation failure occurs, the various states of switch function within the various corresponding time are analyzed in detail. Based on the analysis of switch function and the commutation process of the valves, the regularity of the state of switch function during commutation failure is summarized in this paper. According to the regularity, the advanced model of switch function is established. By superimposing the three-phase switch function model under normal operation, the advanced switch function can be achieved to represent the effect of commutation failure. The physical process of the proposed model is clear and it is easy to express in mathematics and implement. Simulation results show that the proposed model of switch function can represent the effect of the commutation failure on DC system parameters. It can be used to enhance the application of the dynamic phasor model of DC system.