A novel thyristor-based DC circuit breaker with integrated current limiting reactors

The mechanical DC circuit breaker (MCB) based on pre-charged capacitors is considered one of the most promising circuit breakers in high-voltage DC (HVDC) grids due to its advantages of low cost and low on-state loss. However, the pre-charged capacitors require additional extremely complex pre-charging circuits, which poses a major challenge to the reliable handling of faults. This paper proposes a novel thyristor-based DC circuit breaker with integrated current limiting reactors (TR-CB). The capacitor is pre-charged by the system through current limiting reactor in the initial stage of the mechanical switch (MS) starting to separate with arcing, which eliminates the need for additional pre-charging circuits and reduces the voltage withstand level of the capacitor and ensures fast and reliable breaking of bidirectional fault currents in the system, and the breaking time of bidirectional fault currents is consistent. Based on the detailed analysis of the working principles, a parameter designing scheme is provided in detail. Then, the feasibility and effectiveness of the proposed TR-CB topology have been verified by a four-terminal simulation model and a scaled-down experimental prototype. Finally, a comparative analysis is conducted on the investment costs of TR-CB and four other high-voltage circuit breakers.