基于本地信息的多端柔性直流电网故障定位方法

摘要

故障定位技术是保障多端柔性直流电网安全可靠运行的关键技术.由于直流网络之间的相互连接导致其故障暂态特征十分复杂,故障定位往往要依靠通信手段,同时技术难度也会大幅提升.以基于两电平电压源型变流器的多端柔性直流电网为研究对象,提出一种基于本地信息的多端柔性直流电网的故障定位方法.利用限流电抗器作为直流线路边界,分析了限流电抗器类型的选取及其对断路器开断和保护动作时间的影响,从保护识别的准确性和动作的可靠性角度讨论了限流电抗器的容量和位置配置;对直流行波保护的电压变化率判据进行改进,通过比较限流电抗器两端电压变化率的比值和差值设定故障区间的判别方法及逻辑,利用本地信息确定故障位置;基于MATLAB/Simulink进行了大量仿真测试,验证了所提故障定位方法的可行性和有效性.%Fault location is the key technology to ensure safe and reliable operation of multi-terminal flexible DC grid.The interconnections among DC grids result in complex fault transient characteristics,so fault location usually relies on means of communication,increasing technical difficulties dramatically.Taking the two-level voltage source converter-based multi-terminal flexible DC grid as a research object,a fault location method for multi-terminal flexible DC grid based on local information is proposed.With the current limiting reactors as physical boundaries of DC line,the type selection of current limiting reactors and their effects on the breaking of breakers and operation time of protections are analyzed,and the capacity and location configuration of current limiting reactors are discussed considering the accuracy of protection identification and the reliability of protection operation.The voltage variation rate of DC traveling wave protection is improved and the identifying method and logic of fault section are set by comparing the specific value and difference value of voltage variation rates between two ends of current limiting reactor,determining fault location based on local information.A large amount of simulations carried out in MATLAB/Simulink verify the feasibility and validity of the proposed fault location method.