Low Conduction-Loss DC Circuit Breaker with Bidirectional Break Capability

The Modular Multilevel Converter-based High Voltage Direct Current (MMC-HVDC) transmission system has become the most commonly used transmission technology in DC transmission projects. In order to save transmission and distribution costs, it often employs a half-bridge submodule combined with a DC circuit breaker for isolating DC-side short-circuit faults. The DC circuit breaker is crucial equipment for DC fault isolation. During a short-circuit fault on the DC side, the current can quickly exceed several times its rated value within milliseconds. Hybrid DC circuit breakers efficiently and safely interrupt DC power. However, traditional hybrid DC circuit breakers, which use IGBTs as forced commutation switches, incur high costs and suffer from kilowatt-level power losses. Therefore, this paper proposes a low conduction loss DC circuit breaker topology with bidirectional interruption capability. It utilizes thyristors and diode bridges as forced commutation switches and designs thyristor turn-off circuits and capacitor pre-charging strategies. The proposed topology offers advantages of high interruption efficiency, low conduction losses, and low cost. Simulation verification using the PSCAD/EMTDC platform confirms the effectiveness of the proposed topology.