Study on coordination of Coupling mechanical DC circuit breaker and fault current limiter

Aiming at the problems of high amplitude, fast rising speed and difficult fault clearing of DC side fault current in multi-terminal flexible DC transmission system with modular multilevel (MMC-MTDC), a strategy of cooperative coordination of resistive superconducting fault current limiter and coupling mechanical DC circuit breaker to limit fault current and isolate fault lines is proposed. Firstly, the topological structure and working principle of resistive superconducting fault current limiter and coupling mechanical DC circuit breaker are analyzed. Secondly, the principle of superconducting fault current limiter and coupling mechanical DC circuit breaker coordination is analyzed, and on this basis, the coordination timing sequence of superconducting fault current limiter and coupling mechanical DC circuit breaker is proposed. Furthermore, the proposed coordination strategy is verified based on the PSCAD/EMTDC platform. The simulation results show that the coordination timing sequence can isolate faults accurately and quickly, and improve the safety and stability of the MMC-MTDC system.