Influence of capacitor-buffered hybrid DC circuit breaker on bipolar short circuit fault of three-terminal MMC-HVDC transmission system

Abstract

The flexible DC transmission system needs a DC circuit breaker to remove and isolate the bipolar short-circuit fault to prevent the excessive short-circuit current from damaging the DC transmission system. In this paper, a comprehensive model of DC circuit breaker and transmission system is established by using PSCAD based on capacitive buffered hybrid DC circuit breaker. The short-circuit current waveform and DC port voltage waveform of the three-terminal ±350 kV flexible DC transmission system under the condition of double-pole short-circuit fault at the DC side of rectifier station are simulated and calculated. The simulation results show that the maximum current and voltage of the capacitor-buffering hybrid DC circuit breaker model is lower than that of the ideal DC circuit breaker model under the condition of bipolar short-circuit fault at the DC side of the rectifier station. The system fault waveform under different parameters of capacitor-buffered hybrid DC circuit breaker is compared and analyzed through simulation, so as to optimize the parameters of circuit breaker. It can be seen that the actual results more in line with the switching process can be obtained by using the capacitor buffer type hybrid DC circuit breaker.