中文摘要：

微电源以微电网形式接入配电网，使其单向潮流、辐射供电方式转变为双向潮流、环网供电方式；并网运行发生接地故障时，因微电源并网逆变器所产生的方向性助增故障电流或外汲故障电流，可能导致传统继电保护装置拒动或误动。针对这一问题，文中提出一种适用于闭式环网的微电网接地保护方案。该方案需将辐射、树干式配电线路改造成闭式环形配电线路，每段线路按需配置第1类保护器和第2类加速保护器。第1类保护器以单端工频正序故障分量相位判定正向故障，2个保护器同时为正向故障时，实现故障区域定位；第2类加速保护器在加速时段内根据对端保护器动作情况，检测故障分量比值，实现故障区域快速隔离。通过理论分析和系统仿真验证了该保护方案的有效性与可行性。

英文摘要：

With micro-sources connected to the distribution network in the form of a microgrid, power supply is changed from unidirectional flow, radial structure into bidirectional flow, ring loop structure. The output short circuit current of the grid inverter will be directionally increasing and decreasing once the single-phase ground-fault occurs in the combined mode. Consequently, protective devices may cause malfunction and maloperation. To solve these problems, a new ground-fault protection scheme for closed-loop microgrid is proposed. In the scheme, the radial or trunk-style feeders are built into closed- loop connection. Where necessary, each section should be composed of protective devices including the first kind of protectors and the second kind of accelerated protectors. The first kind of protectors detect positive direction fault according to the one-end fault component phase angle. If the signs of the two protectors are both positive, the fault area is located. During acceleration, the second kind accelerated protectors detect the fault component criterion, and then rapidly isolates the fault section by use of the operating results of the opposite protector. It is shown that the scheme proposed is valid and feasible by theoretical analysis and simulation test.