Two basic ways to realise DC circuit breakers

As a key element of the DC grid, the technology of DC circuit breakers (DCCBs) still have difficulty to be widely used due to its large cost and volume. This paper studies the basic principle and its realisation methods for DCCBs. First, two basic ways of breaking the fault current are discussed, including the way by inserting a metal oxide varistor (MOV) to force the fault current to zero and the way by inserting capacitor to change the nature of the fault current. Second, a new approach to realise the DCCB has been proposed based on the inserting capacitor way. According to this new approach, three topologies of DCCB are proposed, including the single-branch DCCB with inserted capacitor (SB-DCCB-C), the double-branch DCCB with inserted capacitor (DB-DCCB-C) and the triple-branch DCCB with inserted capacitor (TB-DCCB-C). All these three DCCBs are proved to be able to deal with DC faults effectively according to the simulation results in PSCAD/EMTDC. Finally, the economy of four circuit breaker structures are compared