Thyristor Based Low Conduction-Loss DC Circuit Breaker With Bidirectional Breaking and Fault Type Determination Capability

Modular Multilevel Converter High Voltage Direct Current (MMC-HVDC) transmission technology has become the predominant solution in HVDC transmission engineering. To minimize transmission costs, the submodule configurations of MMC-HVDC systems generally lack of DC fault-clearing capability, necessitating coordination with DC circuit breakers (DCCB) for isolating DC-side short-circuit faults. This paper proposes a thyristor based low conduction-loss DC Circuit Breaker with bidirectional breaking and fault type determination capability (TC-HCB) to address the high operational costs caused by excessive conduction losses in existing solutions. The design employs thyristors as load commutation switches, achieving minimal conduction loss under normal operation. A capacitor-based thyristor breaking circuit and corresponding pre-charging circuits are developed to enable the ultra fast disconnector(UFD) to safely open under zero-current conditions without arcing. Key component parameter design criteria are analyzed, and the effectiveness of the proposed TC-HCB is validated through PSCAD/EMTDC platform simulations and low-voltage prototype experiments.