环形直流微电网故障分析与保护

直流微电网故障的快速检测与切除是提高其运行可靠性的关键。电流差动保护可快速有选择地切除故障，但受短路阻抗影响较大，在高阻抗短路时可能拒动。针对环形直流微电网，文中提出基于母线功率变化率的差动保护，由母线两侧功率变化率作为差动量，在区内故障时，母线功率变化率差动值大于动作值，保护动作切除故障线路。功率变化率差动值与短路电流平方及短路阻抗成正比，相比电流量保护，具有更快的故障识别速度和更高的保护灵敏度。仿真结果验证了所提保护方案具有更好的速动性、灵敏性，提高了环形直流微电网的可靠性和稳定性。

Fault Analysis and Protection of Ring DC Microgrid

The rapid detection and removal of faults are the key to improving the operation reliability of DC microgrids. The current differential protection can remove the fault quickly and selectively. But it is greatly affected by the short-circuit impedance, and it may refuse to operate in the cases of the high impedance short circuit. For ring DC microgrids, a differential protection based on change rates of bus power is proposed. The power change rates of both sides of the bus are taken to formulate the differential value. The differential value of the change rates of bus power is bigger than the operation setting in the case of internal fault, and the protection will operate and remove the fault line. The differential value of the power change rates is proportional to the square of short-circuit current and short-circuit impedance. Compared with protection schemes based on current, it has faster fault identification speed and higher protection sensitivity. The simulation results show that the proposed protection scheme has better operation speed and sensitivity, and improves the reliability and stability of the ring DC microgrid.