独立运行微电网的故障特征分析

Analysis on fault characteristics of independent microgrid

根据某海岛的微电网结构建立了电磁暂态仿真模型,其包含4种微电源:储能、柴油发电机、直驱风机和光伏发电单元。在模型中设置多种故障,分析相应的故障特征及故障对传统继电保护的影响,并得出如下结论:在各微电源故障期间均能提供一定的故障电流,并且其自身保护按低电压穿越要求整定的前提下,馈线上的电流速断保护受各微电源故障电流受限的影响无法使用,而过电流保护受影响很小;电网电压严重跌落时,采用PQ控制的微电源故障电流频率将偏离工频,由此可能导致故障馈线母线侧的过电流保护失效,此时只能依靠纵联保护;在包含PQ控制的微电网中,不应配置基于故障分量的继电保护装置。

A electromagnetic transient simulation model is built according to the microgrid topology of an island,which contains four kinds of microsource：battery storage,diesel generator,direct-driven wind turbine and photovoltaic unit.Different faults are set in the model,and the corresponding fault characteristics,as well as their influences on traditional relay protection,are analyzed.Conclusions：on the condition that all microsources can provide fixed fault current and their own protectors are set based on LVRT（Low Voltage Ride Through） rule,current fast-tripping protection of feeder is invalid because of the limitation of microsources＇ fault currents,but it has slight impact on over-current protection;when grid voltage badly dips,the frequency of fault currents of microsources with PQ control will deviate from 50 Hz,which may cause the failure of over-current protection at faulty feeder side,therefore,pilot protection should be used; the fault-component-based protection should not be configured in the microgrid,which contains PQ control.