使用故障分类新方法的直流微电网保护方案

Protection Scheme for a DC Microgrid Using a New Fault Classification Method

直流微电网发生短路故障时,各故障点的短路电流特征非常接近,目前的保护算法几乎无法识别。为此通过分析一个多母线直流微电网的故障电流,提出了一种安装感性阻抗、并与瞬时故障电流和电流导数相结合的故障分类新方法。安装在直流微电网各条线路中的感性阻抗在故障瞬变状态下会使故障电流及其导数发生很大变化,从而使保护单元能够将故障区分为母线故障、连接支线故障、相邻母线（或支线）故障3种类型。仿真实验证明,基于故障分类新方法的保护能够将直流微电网中的短路故障精确分类,准确隔离故障区域并快速恢复系统,是适用于多母线和直流微电网短路故障的有效保护方案。

When a short-circuit fault happens in a DC microgrid,the characteristic values of every fault are similar to each other,thus current protection arithmetic can not distinguish a fault from others.We analyzed the fault current of a DC microgrid with multiple buses,and proposed a new fault classification method,in which some inductive impedances in the microgrid was installed and the fault current and current derivative were combined.The inductive impedances which were installed in every line of the DC microgrid could make a great variation to the fault current and its derivative under the fault transient condition,thus the protection unit could classify the faults into three types including bus fault,interconnected line fault,and adjacent bus（or line） fault.The simulation testing results prove that the protection based on the new fault classification method can accurately identify each fault type happened in microgrid,exactly isolate the fault area and quickly restore the power system,and it is an effective protection scheme which is suitable to short-circuit faults happened in a DC microgrid with multiple buses and lines.