基于控保协同的环形直流微网单端测距保护技术  

Single-end Ranging Protection Technology for Ring DC Microgrid Based on Coordinated Control and Protection

作　　者：薛士敏[1] 刘存甲 李蒸 陆俊弛 朱晓帅 XUE Shimin;LIU Cunjia;LI Zheng;LU Junchi;ZHU Xiaoshuai(Key Laboratory of the Ministry of Education on Smart Power Grids(Tianjin University),Tianjin 300072,China;State Grid Dalian Electric Power Supply Company of State Grid Liaoning Electric Power Co.,Ltd.,Dalian 116000,China)

机构地区：[1]智能电网教育部重点实验室(天津大学),天津市300072 [2]国网辽宁省电力有限公司大连供电公司,辽宁省大连市116000

出　　处：《电力系统自动化》2020年第5期122-129,共8页Automation of Electric Power Systems

基　　金：国家自然科学基金资助项目(51577129);天津市自然科学基金资助项目(19JCYBJC21400)。

摘　　要：目前,直流微网的保护方案大都依赖于线路两端直流断路器的快速开断能力与通信设备的可靠性,然而现阶段直流断路器成本高昂,且线路两端通信将会大大增加直流微网的建设运行成本。基于以上背景,文中以四端环形直流微网系统为研究对象,提出了一种基于控保协同的单端测距式保护技术。该方法分为故障控制与保护实施2个阶段。在故障控制阶段,通过改变电压源型换流器(VSC)自身以及外加可控元件的主动控制策略,使直流线路故障电流为零;在保护实施阶段,基于采用主动控制后VSC直流侧输出电压的周期性(20 ms)与电力电子元件的可控性,构建VSC与故障点的唯一回路,然后基于传统RL算法即可实现单端无差故障定位,接下来会出现线路电流持续过零,在此基础上,通过快速隔离开关实现故障隔离。该方法基于控保协同思想,消除了环网系统单端故障测距中对端电流的干扰,且线路两端无需配置直流断路器,仅利用快速隔离开关与故障控制策略进行时序逻辑上的相互配合即可实现故障隔离。最后,在PSCAD/EMTDC仿真平台上搭建四端环形直流微网系统模型,验证了该控制和保护方案的有效性。At present, the protection schemes of DC microgrid mostly depend on the fast breaking ability of DC circuit breakers at both ends of the line and the reliability of communication equipment. However, at this stage, the cost of DC circuit breakers is high, and the communication between the two ends of the line will greatly increase the construction and operation cost of DC microgrid. Based on the above background, this paper proposes a single-end ranging protection technology based on coordinated control and protection for the four-terminal ring DC microgrid. This method can be divided into two stages: fault control and protection implementation. In the stage of fault control, the fault current of DC line is controlled to be zero by changing the active control strategy of voltage source converter(VSC) itself and the external controllable elements. In the stage of protection implementation, based on the periodicity(20 ms) of the output voltage at the DC side of VSC after active control and the controllability of power electronic components, the unique loop between VSC and fault point is constructed. Then the single-end fault location without error can be realized based on the traditional RL algorithm. Differential fault location will lead to continuous zero-crossing of line current. On this basis, fault isolation can be achieved by fast disconnector. Based on the idea of coordinated control and protection, this method eliminates the interference of terminal current in single-end fault ranging of ring network, and there is no need to configure DC circuit breakers at both ends of the line. Fault isolation can be achieved only by using fast disconnector and fault control strategy to cooperate logically in time sequence. Finally, a model of four-terminal ring DC microgrid is built on the PSCAD/EMTDC simulation platform, which verifies the effectiveness of the control and protection scheme.

关 键 词：直流微网 控保协同 单端故障测距 反并联晶闸管组 快速隔离开关 

分 类 号：TM721.1[电气工程—电力系统及自动化]