Multi-port DC circuit breaker-based fault clearing scheme for LCC-VSC hybrid multi-terminal HVDC systems

A hybrid multi-terminal DC system is an effective solution to the problem of large-scale renewable energy transmission and consumption. A fast and effective DC fault clearing scheme is key to ensuring its safe and stable operation. However, the commonly used self-clearing converter-based fault clearing scheme will cause a short-term power failure in a healthy converter station. However, a DC circuit breaker-based fault clearing scheme carries a high implementation cost. This paper proposes a novel diode bridge-type multi-port hybrid DC circuit breaker and designs the fault clearing scheme of a three-terminal hybrid DC system based on the proposed multi-port DC breaker. The proposed fault clearing scheme adopts LCC phase shift control at the rectifier station to clear the fault and restart the converter. Then, the proposed multi-port hybrid DC circuit breaker is installed at the busbar to achieve rapid DC fault clearing and reclosing. The proposed scheme's effectiveness is verified using PSCAD/EMTDC simulation, and compared with the existing schemes. The results show that the proposed scheme can significantly reduce the cost of using DC breakers in hybrid multi-terminal DC systems while ensuring fast and effective fault clearing. © 2021 Power System Protection and Control Press.