基于暂态电流比值的多端柔性直流电网保护  

Novel Protection Based on Transient Current Ratio for MTDC Grid

作　　者：刘佳硕 李永丽[1] 陈晓龙[1] 刘宁宁[1] 周宁[1] LIU Jiashuo;LI Yongli;CHEN Xiaolong;LIU Ningning;ZHOU Ning(Key Laboratory of Smart Grid(Tianjin University),Ministry of Education,Nankai District,Tianjin 300072,China)

机构地区：[1]智能电网教育部重点实验室(天津大学),天津市南开区300072

出　　处：《电网技术》2023年第4期1439-1449,共11页Power System Technology

基　　金：国家自然科学基金委员会-国家电网公司智能电网联合基金资助项目(U2066210)。

摘　　要：多端柔性直流电网(multi terminal DC,MTDC)要求直流线路发生故障后在几毫秒内隔离故障线路,如何实现故障线路快速可靠识别是MTDC直流线路保护的难点之一。该文利用区内外故障时保护安装处暂态电流与本侧模块化多电平换流器(modular multilevel converter,MMC)故障电流的比值差异,提出了一种基于暂态电流比值的直流线路保护方案。该方法通过测量线路双端电气量来判断故障位置,可以保护线路全长。最后,在PSCAD/EMTDC仿真平台搭建了四端柔性直流电网模型,通过仿真验证所提保护方案的可行性与优越性。As the short-circuit current output from the new energy power supply at the time of a fault presents the characteristics of frequency shifting,high percentage of the harmonic content,restricted amplitudes,unequal positive and negative sequence impedances,etc.,resulting in the risks of the fault location failures based on the power frequency.Therefore,a fault location method for double-circuit transmission lines of a wind farm is proposed.The transmission line equation is discretized which is expressed in the form of partial differential equations by using the finite-difference time-domain.Then,the transmission line equation is solved by using the modified variational iterative method to obtain the function of line length,using the phase voltage and the phase current at the both ends of the line as the boundary conditions.Last,the fault location is achieved by constructing the fault location function.Through the analysis on the PSCAD/EMTDC and the hardware-in-the-loop test experimental platform,the proposed algorithm is verified to be able to accurately notarize the fault locations.

关 键 词：多端柔性直流电网 故障识别 纵联保护 线路保护 

分 类 号：TM721[电气工程—电力系统及自动化]