多端柔性直流配电网高频功率相关性纵联保护方法

直流线路保护是保障多端柔性直流配电网系统安全稳定运行的关键，主要技术难点在于故障区段的准确识别和快速隔离。文中分析了故障后直流配电网中暂态高频分量的分布特点，提出一种基于高频功率的直流线路纵联保护方法。利用故障前后高频功率的幅值变化，提出保护快速启动判据。利用不同故障情形下线路两侧高频功率线性关系和相关系数的差异，提出基于线路两侧高频功率相关系数的故障识别和选极判据。基于MATLAB/Simulink建立多端柔性直流配电网模型，仿真结果表明所提保护方法可快速、准确地判断故障线路和故障极，灵敏度与可靠性高，阈值易设定且相邻线路保护无须配合，对双端数据同步要求较低，不受系统运行方式影响和网络拓扑的限制，且具备良好的抗过渡电阻能力。

Pilot Protection Method for Multi-terminal Flexible DC Distribution Network Based on Correlation of High-frequency Power

DC line protection is the key to ensure the safe and stable operation of the multi-terminal flexible DC distribution system. The main technical difficulties include the accurate identification and rapid isolation of the fault section. Distribution characteristics of the transient high-frequency components in DC distribution network after the fault are analyzed, and a pilot protection method for DC lines based on the transient high-frequency power is proposed. Based on the amplitude variation of the high-frequency power before and after the fault, the fast starting criterion for protection is proposed. According to the difference of linear relationship and correlation coefficient of high-frequency power on both sides of the line in different fault conditions, fault identification and pole selection criterion based on correlation coefficient of high-frequency power on both sides of the line is proposed. Based on MATLAB/Simulink, a multi-terminal flexible DC distribution network model is established. The simulation results show that the proposed protection method can quickly and accurately identify the fault line and fault pole with high sensitivity and reliability. Protection threshold is easy to be set and the protection coordination of adjacent lines is not required. Moreover, it has low requirements for data synchronization, and is not affected by system operation mode and network topology with good insusceptibility to fault resistance.