Coordinated Control of DC Circuit Breakers in Multilink HVDC Grids

High voltage DC grids are developing in more terminals and with larger transmission capacity, thus the requirements for DC circuit breakers (DCCB) will continue to rise. Conventional methods only use the faulty line DCCB to withstand the fault stress, and therefore this paper presents a coordination method of multiple DCCBs to protect the system. As many adjacent DCCBs are tripped to interrupt the fault current, the fault energy is shared, and the requirement for the faulty line DCCB is reduced. Moreover, the adjacent DCCBs are actively controlled to help system recovery. The primary protection, backup protection, and reclosing logic of multiple DCCBs are studied. Simulations confirm that the proposed control reduces the energy dissipation requirement of faulty line DCCB by approximately 30%-42%, the required current rating for IGBTs is reduced, and the system recovery time is also reduced by 20–40 ms.