基于余弦相似度算法的混合级联直流输电线路保护新方案

A new protection scheme for hybrid cascaded HVDCtransmission lines based on cosine similarity algorithm

为提高混合级联直流输电系统直流输电线路保护的速动性和可靠性,提出一种基于余弦相似度算法的混合级联直流输电线路保护原理。当混合级联直流输电系统线路故障时,电流和电压会发生变化,因此利用输电线路首末单端的电压和电流暂态分量,经过数据标准化处理,通过余弦相似度算法比较电流和电压故障分量差异,完成区内外故障准确识别。采用PSCAD/EMTDC软件搭建特高压混合级联直流输电系统仿真模型,利用Matlab验证保护策略可行性。仿真结果表明:当发生区内外故障时,保护原理均可在3 ms内完成故障识别,保护方案可靠且速动。在区内分别设置不同过渡电阻情况下,仍可准确识别故障,该保护方案具有较强的耐受过渡电阻能力。

In order to improve the speed and reliability of DC transmission line protection in hybrid cascade DC transmission system,a hybrid cascade DC transmission line protection principle based on cosine similarity algorithm was proposed.When the line fault of the hybrid cascade DC transmission system was made,the current and voltage would change,so the voltage and current transient components at the first and last end of the transmission line were used to compare the differences of current and voltage fault components through data standardization and cosine similarity algorithm,so as to complete the accurate identification of faults inside and outside the area.PSCAD/EMTDC software was used to build the simulation model of UHV hybrid cascaded DC transmission system,and the feasibility of the protection strategy was verified by Matlab.The simulation results show that when a fault occurs inside and outside the area,the protection principle can complete the fault identification within 3 ms,and the protection scheme is reliable and fast-moving.When different transition resistors are set in the area,the fault can still be accurately identified,and the protection scheme has a strong ability to withstand the transition resistance.