双极低压直流配电网具备可再生能源集成、供电方式灵活和供电可靠性高等优点，但其短路故障会造成系统严重过流，威胁系统的正常运行。针对单极接地和双极短路故障提出了一种基于双极型隔离式模块化多电平直流变压器的故障综合限流控制策略，通过软、硬件结合的方式有效抑制变压器内部过电流及输出故障电流，从而降低直流断路器的切断时间及容量需求。分析了不同故障下双极低压直流配电网的电流故障分量，提出了基于电流积分平均值的故障识别判据，结合闭锁原件和延时元件构建了双极低压直流配电网保护方案。仿真验证了故障综合限流控制策略及保护方案的正确性和有效性。

Bipolar low-voltage DC distribution networks have the advantages of renewable energy integration, flexible power supply mode and high-power supply reliability, but their short-circuit faults have a serious impact on power supply reliability. In this paper, a fault comprehensive current limiting control strategy based on a bipolar isolated modular multilevel DC transformer is proposed for unipolar grounding and bipolar short-circuit faults in bipolar low-voltage DC distribution networks, which effectively suppresses the internal overcurrent of the transformer and the output fault current by means of combining software and hardware, so as to effectively reduce the cut-off time and the capacity requirement of the DC circuit breaker. The current fault components of bipolar low-voltage DC distribution networks under different faults are analyzed, and a fault identification criterion based on the average value of the current integral is proposed, and a protection scheme for bipolar low-voltage DC distribution networks is constructed by combining with directional elements and time-delay elements. Simulation verifies the correctness and effectiveness of the comprehensive fault current limiting control strategy and protection scheme.