Abstract:
The fault of the DC grid to be cleared exists challenges between cost and cutting speed by the half-bridge modular multilevel converter(MMC). The fault is difficult to be cleared without fault current limitation. A novel topology of H-bridge hybrid fault current limiter(FCL) was proposed to suppress DC side fault current. In this topology, the load current flows through the low-loss branch at steady state, and the current flows through the commutation branch after the fault to realize the current limiting process. The commutation branch consists of thyristor, commutation capacitance, current-limiting inductance and four groups of H-bridge diodes. The principle, control method, electrical stress and preferences of the proposed limiter have been studied, and the simulation verification was carried out in single-terminal converter station and four-terminal DC grid. It is shown that the proposed FCL is suitable for HVDC transmission with effective current limiting result and economic efficiency. The simulation results show the correctness of the theoretical analysis and the feasibility of the current limiting scheme.