基于单端分支系数的四端柔直环网线路保护方案  

Line Protection Scheme for Four-terminal Flexible Direct Loop Network Based on Single-terminal Branch Coefficient

作　　者：束洪春[1] 任敏 田鑫萃[1] 李涛 SHU Hongchun;REN Min;TIAN Xincui;LI Tao(College of Electric Power Engineering,Kunming University of Science and Technology,Kunming 650504,China)

机构地区：[1]昆明理工大学电力工程学院,昆明650504

出　　处：《高电压技术》2024年第2期683-692,I0014-I0016,共13页High Voltage Engineering

基　　金：国家自然科学基金(52167011,52037003);云南省重大科技专项计划(202002AF080001)。

摘　　要：为提升直流线路保护在柔性直流环网中的速动性与可靠性,提出一种基于单端分支系数的保护方案。分析了不同故障位置下各换流阀提供的故障电流分量,并根据单端换流阀极线电流突变量构造分支系数,结果表明线路保护区内故障下的单端分支系数小于区外故障,利用该特征构造区内、外故障识别元件。在线路高阻接地致使主保护失效时,根据桥臂最大允许电流决定线路纵联后备保护的开放时限,以优化现有主、后备保护方案之间的时序配合方案,保障各种直流线路故障工况下,换流阀不间断运行。保护方案不依赖线路边界元件,算法简单,大量仿真结果表明,该方案有良好的耐受过渡电阻能力,能在换流阀闭锁前实现故障区域可靠识别。According to the requirements of DC line protection in flexible DC power grid in terms of speed and reliability,a protection scheme based on single terminal branching coefficient is proposed.The fault current components provided by each converter valve under different fault positions are analyzed,and the branching coefficient is constructed according to the variation of DC line current of single-ended.The results show that the single-termial branching coefficient under the fault in the line protection area is less than that that outside the area.This feature is used to realize the identification of fault area.When the main protection fails due to the high resistance grounding of the line,a longitudinal backup protec-tion scheme using the maximum allowable current of the bridge arm to determine the opening time of the line protection is proposed,so that the problem of timing coordination between the existing main and backup protection schemes is solved,and the uninterrupted operation of the converter under various DC line fault conditions is realized.The protection scheme does not rely on boundary elements and the algorithm is simple.A large number of simulation results show that the scheme has a good ability to withstand the transition resistance and can reliably identify the fault area before the con-verter locked.

关 键 词：柔性直流电网 分支系数 接地故障 故障电流解析 故障识别 保护时序配合 

分 类 号：TM721.1[电气工程—电力系统及自动化]