柔性直流电网架空线路快速保护方案

基于柔性直流输电的直流电网技术,是大规模清洁能源接入电网的有效手段,直流电网快速线路保护是其面临的重要技术挑战之一。以国内计划建设的张北直流电网工程为背景,提出了一套适用于全网配置直流断路器、采用架空线输电的对称双极直流电网线路快速保护方案。保护仅利用单端信息进行故障判别,且保护数据窗短,满足速动性的要求;保护采用电压梯度快速检测故障,利用限流电抗器对故障电压信号的平滑作用实现故障区间的判别,并根据零模与一模电压传播特性的差异判定故障极,实现保护的选择性与高可靠性。结合直流电网的PSCAD模型,验证了所提出方案在不同故障情况下的保护性能,并分析了保护对运行方式改变的适应性。

Fast Protection Scheme for Overhead Transmission Lines of VSC-based HVDC Grid

The voltage source converter(VSC)-based high voltage direct current(HVDC)grid technology is an effective means for large-scale integration of clean energy. The fast DC line protection technology is one of the main challenges to HVDC grids. Based on the Zhangbei HVDC grid project, this paper proposes a fast protection scheme for overhead transmission lines of bipolar VSC-based HVDC grids equipped with DC circuit breakers. The protection is based on local measurements featuring fast response speed. The voltage gradient is used to detect faults rapidly, and the voltage derivative criterion is adopted to identify the protection zone in which the fault occurs thanks to the smoothing effect of the fault current limiter. And the faulty pole is identified according to the different propagation characteristics between the line mode and zero mode voltage, ensuring the selectivity of the protection as well as high reliability. The Zhangbei HVDC grid model is built in PSCAD/EMTDC and the performance of the proposed protection scheme is verified by simulation results of various fault conditions, as well as different operation modes of the HVDC grids. This work is supported by National Natural Science Foundation of China(No. 51577148)and National Key Research and Development Program of China(No. 2016YFB0900603).