With the development and utilization of large-scale wind power and photovoltaic in the world

the penetration of its ratio of power generation continues to increase. Flexible DC grid is an important role to support high penetration of renewable energy accomodation

which has been an important direction of power grid development. High voltage DC circuit breakers

as the key device for DC fault isolation in DC grid have been receiving more and more attention. This paper proposes a novel high voltage DC circuit breaker time-sequence coordination method for DC grid protection. The method could effectively reduce the DC fault current broken by the other DC circuit breakers when one or more DC circuit breakers fail to operate. The method could also reduce the fault isolation time and the energy dissipation in DC circuit breakers. Meanwhile

this paper proposes a fault judgement method for DC circuit breakers coordination

which could accurately determine whether DC circuit breakers fail to operate or not. The simulation results in PSCAD/EMTDC validate the correctness and validity of the proposed method and fault judgment method.