A Capacitor-based Active Clamp Type Hybrid DC Circuit Breaker

A hybrid DC circuit breaker has both the static characteristics of the mechanical DC circuit breaker and the dynamic characteristics of the solid-state DC circuit breaker. It has a faster breaking speed and lower on-state loss. It is the preferred technical solution for medium and high-voltage DC transmission and distribution systems. However, the hybrid DC circuit breaker based on module cascade has problems such as high investment cost, high energy absorption of arresters, and lack of ability to distinguish the nature of faults, which limits the engineering application of circuit breakers. Based on the existing structure, this paper proposes a hybrid DC circuit breaker based on capacitor clamping. The pre-charged capacitor is mainly used to clamp the voltage of the converter station side, which avoids the rapid drop of the voltage of the converter station and reduces the peak value of the fault current on the converter station side. In addition, the capacitor voltage can also be used as an auxiliary judgment for line fault and reclosing. The detailed theoretical derivation and analysis of the proposed structure are carried out. The single-ended equivalent and four-terminal DC loop network, is established in PSCAD / EMTDC to verify the proposed structure and compared with the original scheme. The simulation results show that the proposed structure is feasible and has advantages over the original scheme.