VSC-HVDC Line Protection Principle Based on the Similarity of the Double-ended Initial Current Traveling Wave Time-frequency Matrices
张韵琦 1王聪博 1余越 1杨国生 1曹虹1
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作者信息
1. 电网安全与节能国家重点实验室(中国电力科学研究院有限公司),北京市 海淀区 100192
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摘要
针对目前柔性直流(voltage source converter-based high voltage DC,VSC-HVDC)电网的线路保护中存在的问题,提出一种基于双端初始电流行波(Initial current traveling wave,ICTW)时频矩阵相似度的柔性直流输电线路保护原理.首先,对柔性直流电网在线路区内外故障下两端保护所在处ICTW的故障特性进行分析,总结出在特定时间窗内,区内故障下两端 ICTW 的频域相似度远高于区外故障.在此基础上,利用 S 变换对双端 ICTW 进行时频分析,建立时频矩阵,并对其做奇异值分解(singular value decomposition,SVD).然后根据特征矩阵构造双端ICTW的相似度计算公式,以该相似度的大小判别线路区内外故障.另外,根据线路两端 ICTW 的高低频能量比识别雷击干扰.最后,各种故障情况下的仿真结果表明,该保护原理不依赖线路边界元件,可以保护不同长度线路的全长,具有更高的耐过渡电阻和抗噪声能力,并且能够满足柔性直流电网主保护的速动性要求.
Abstract
Aiming at the problems currently existing in line protection for voltage source converter-based high voltage DC(VSC-HVDC)grids,a double-ended protection principle based on similarity of time-frequency matrix of initial current traveling wave(ICTW)is proposed.First,the fault characteristics of the ICTWs on both sides of the line in the flexible DC grids under internal and external faults are analyzed.It is concluded that within a specific time window,the frequency-domain similarities of the double-ended ICTWs under internal faults are much higher than those under external faults.Then,the double-ended ICTWs are performed S-transform,and the time-frequency matrices are obtained.Then singular value decomposition(SVD)is performed on the matrices.Afterwards,the similarity calculation formula of the double-ended ICTWs is constructed based on the feature matrices,and the internal and external faults can be identified by the value of the similarity.In addition,lightning interference is identified according to the high and low frequency energy ratio of the ICTWs at both ends of the line.Finally,the simulation results under various fault conditions show that the protection scheme does not rely on line boundary elements;it can protect the full length of lines with different lengths;it has stronger robustness against transition resistance and noise.Besides,it satisfies the quick identification requirements of the main protection for VSC-HVDC grids.
关键词
双端量保护/柔性直流(VSC-HVDC)电网/初始电流行波(ICTW)/时频矩阵/相似度
Key words
double-ended protection/voltage source converter-based high voltage DC(VSC-HVDC)grid/initial current traveling wave(IVTW)/time-frequency matrix/similarity
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