基于电流变化量相似性的海上风电场交流送出线路纵联保护

Pilot protection for an AC transmission line of an offshore wind farm based on similarity of current variation

交流送出线路是海上风电经柔直并网的重要组成部分。该线路故障时,呈现出明显区别同步机电源的故障特征,使得传统纵联保护难以满足可靠性与灵敏性的要求。结合故障后交流送出线路两侧电流变化量的特点,提出一种利用电流变化量相似性的纵联保护原理。以Kendall算法为基础,对交流送出线路内、外部故障时风场侧与柔直侧电流变化量的相关性进行定性分析,提出基于线路两侧电流变化量相关系数的保护判据。利用EMTP-RV仿真软件搭建了海上风电柔直并网系统模型。通过对故障类型、过渡电阻、分布电容、噪声、采样频率、数据窗长以及控制策略的仿真分析,验证了该方法的有效性与可行性。

The AC transmission line is an important part of the grid connection of offshore wind power via MMC-HVDC.When a fault occurs in the line,it presents fault characteristics that significantly differ from the synchronous generator sources,making it difficult for traditional pilot protection to meet the requirements of reliability and sensitivity.Combined with the characteristics of the current variation on both sides of the AC transmission line after a fault,a pilot protection principle based on the similarity of the current variation is proposed.Based on the Kendall algorithm,this paper qualitatively analyzes the correlation between the current variation on the wind farm side and the MMC-HVDC side during internal and external faults in the AC transmission line,and proposes a protection criterion based on the correlation coefficient of the current variation on both sides of the line.A model for MMC-HVDC-connected offshore wind power is built in EMTP-RV software.The validity and feasibility of the new method are verified by simulation analysis of fault type,fault resistance,distributed capacitance,noise,sampling frequency,data window length and control strategy.