基于电压行波陡度的柔性直流送出线路快速保护方案

柔性直流技术在灵活解决高比例新能源消纳的问题上具有革命性意义。针对传统线路保护已不能可靠适应柔性直流送出系统高比例电力电子设备脆弱性、故障信息提取难等问题，文中提出一种基于电压行波陡度的柔性直流送出线路快速保护方案。通过分析直流线路故障暂态特性，利用限流电抗器两侧故障电压行波陡度与极性的不同，增加了有效暂态信息量提取范围，实现区内外故障识别；利用故障极与健全极的电压行波变化程度存在明显差异，判别故障类型；同时考虑了雷击干扰并利用其初始变化特性提出了快速识别方法。最后通过仿真验证了该保护方案在各种影响因素下的性能，可以快速可靠地识别故障，具有良好的灵敏性和抗干扰能力。

Fast protection scheme for flexible DC transmission line based on voltage traveling wave steepness

Flexible DC technology has revolutionary significance in flexibly solving the problem of high proportion of new energy consumption. Due to the vulnerability of high-ratio power electronic equipment and the difficulty in extracting fault information,traditional line protection schemes can no longer be reliably adapted to the flexible DC transmission system. A rapid protection scheme for flexible DC transmission lines based on voltage traveling wave steepness is proposed in this paper. By analyzing the transient characteristics of DC line faults,and utilizing the differences in the steepness and polarity of fault voltage traveling waves on both sides of the current-limiting reactor, the range of effective transient information extraction is increased,and the fault identification inside or outside the region is realized. The faults are classificated by utilizing the significant difference in the degree of voltage traveling wave variation between the faulty and sound poles. Lightning interference is considered and a rapid identification method is proposed by using its initial change characteristics. Finally,the performance of the protection scheme under various influencing factors is verified by simulation,which can identify faults quickly and reliably and has good sensitivity and anti-interference ability.