Failure Protection Method for 500kV Hybrid DC Circuit Breaker

Direct current circuit breaker (DCCB) is a key device for fast fault clearing in modular multilevel converter (MMC)-based DC grids, but its complex structure and numerous components may lead to internal component failures. The topology and operating principles of the hybrid DC circuit breaker are analyzed to reveal the external characteristics of breaker under different component failures. A hybrid DCCB failure protection method including DCCB failure protection algorithm and DCCB failure protection criterion is proposed, and the operation status of DCCB is classified as normal operation, partial failure and complete failure according to the number of failure sub-modules. The failure protection method is validated by PSCAD/EMTDC simulation, and the results show that the method has excellent effectiveness and accuracy.