基于电压行波极性特征的新能源送出线路保护方案

新能源经交流线路送出时，由于其弱馈性和受控特性，传统的工频量保护难以适用，而行波保护能够在新能源控制系统介入导致故障特性发生较大变化之前完成故障识别，是目前解决新能源送出线路工频量保护问题的有效途径之一。然而现有的单端行波保护方案无法准确识别区内近端故障和区内末端故障，因此文中分析了区内和区外故障情况下行波的折反射过程，并利用电压行波零模分量与线模分量到达保护安装处的时间差对故障位置进行初判；针对基于时间差难以准确识别的区内近端故障和区内末端故障，进一步挖掘电压行波的极性特征，利用首个反极性的电压行波和故障初始电压行波到达保护安装处的时间差与故障位置的关系来识别区内近端故障，利用前2个电压行波的极性关系来识别区内末端故障。仿真结果表明，该方案能够快速识别区内外故障，并且具有较好的耐过渡电阻能力。

Research on renewable energy line protection based on voltage traveling wave polarity

WWhen renewable energy is sent out through AC transmission line, the weak-infeed and controlled characteristics make the traditional power frequency protection methods lose efficacy. On the contrary, the traveling wave pro-tection methods can judge the fault before the control system responds, which are one of the effective ways to solve the problem encountered in renewable power system. However, the existing traveling wave protection schemes are limited by the sampling rate, which makes it difficult to accurately identify the internal near-end fault and the internal remote-end fault. To solve this problem, this paper first analyzes the grid diagram of travel-ing wave in case of internal and external faults. Then, the time difference between zero-mode and line-mode is used to judge the fault location. For the near end fault and remote end fault which are difficult to be accurately identified based on the time difference, this paper proposes to use the first reverse polarity traveling wave to identify the near-end fault, and use the polarity of the first two line-mode traveling waves to identify the remote end fault. Simulation results show that the proposed scheme can quickly identify internal and external faults and has good ability to withstand transient resistance.