光伏场站送出线路采样值差动保护的谐波影响分析及改进  

Influence Analysis and Improvement of Harmonic on Sampled Value Differential Protection for Out⁃going Lines Connected to Photovoltaic Power Plants

作　　者：吕晓 刘益青[1] 郭浩 薛嘉慧 LYU Xiao;LIU Yiqing;GUO Hao;XUE Jiahui(School of Electrical Engineering,University of Jinan,Jinan 250022,China)

机构地区：[1]济南大学自动化与电气工程学院,山东济南250022

出　　处：《山东电力技术》2021年第3期18-26,共9页Shandong Electric Power

基　　金：国家自然科学基金(52077124);山东省重点研发计划(2019GGX103014)。

摘　　要：光伏场站通过逆变器并网,受逆变器控制策略影响,当送出线路故障时光伏场站提供的短路电流中谐波含量明显高于系统侧,其中又以3次谐波含量最高。通过对场站侧短路电流中含有3次谐波、系统侧短路电流不含3次谐波的模型进行定量分析,发现3次谐波对送出线路的采样值差动保护产生了极为不利的影响,导致采样值差动保护的固有模糊区显著增大,从而引起采样值差动保护应用于光伏场站送出线路时性能下降,甚至会出现区外故障误动、区内故障灵敏度下降的严重问题。针对该问题,提出一种改进保护方案,仍以采样值差动判据为主判据,仅在采样值差动判据的模糊区投入基于斯皮尔曼等级相关系数判据作为辅助判据。通过在PSCAD中搭建典型的光伏场站送出线路模型,验证了所提改进保护方案的有效性。Photovoltaic power plants are connected to the grid through inverters.Affected by the inverter control strategy,the harmonic content of short circuit current provided by photovoltaic station is significantly higher than that of grid side when the out⁃going line fails,and the third harmonic content is the highest.Through the quantitative analysis of the model of station side short circuit current containing the third harmonic and grid side short circuit current without the third harmonic,it was found that the third harmonic has a very adverse effect on the sampled value differential protection of the outgoing line,which leads to the significant increase of the inherent fuzzy area of the sampled value differential protection,and thus causes the performance degradation of the sampled value differential protection applied to the outgoing line of photovoltaic station.It may even cause serious problems such as misoperation of external faults and decrease of sensitivity of internal faults.To solve this problem,an improved protection method was proposed,which was still based on the sampling value differential criterion as the main criterion,and the criterion based on Spearman rank correlation coefficient was put into the fuzzy area of the sampling value differential criterion as the auxiliary criterion.A typical out⁃going line model of photovoltaic station is built in PSCAD,verifying the effectiveness of the proposed improved protection method.

关 键 词：光伏场站 送出线路 采样值差动保护 谐波 模糊区 斯皮尔曼等级相关系数 

分 类 号：TM77[电气工程—电力系统及自动化]