Research on Overvoltage Distribution of HVDC Converter Valve and Influence of Parasitic Capacitance in special environment

HVDC transmission technology has great advantages in long-distance, large-capacity and cross-region power transmission. Thyristor converter valve is the core equipment of HVDC transmission technology, and its reliability directly affects the reliability of the whole HVDC transmission system. During the operation of HVDC transmission system, it will face the special operating environment, including high altitude nuclear electromagnetic pulse (HEMP), lightning wave, operating wave, and steep wave. The wideband model of the converter valve of ±500kV GaoZhao HVDC transmission project was built in this paper, and the overvoltage distribution on thyristors and saturable reactors under 4 special environments were simulated based on this wideband model. Finally, the influence of the parasitic capacitance parameters on overvoltage distribution was studied. The results show that the overvoltage distribution inside the converter valve tower is related to the characteristic parameters of the special environment, and different types of parasitic capacitance parameters have different effects on overvoltage amplitude. It has certain reference value for studying the reliability of the converter valve system under special circumstance.