基于电压折射波幅值正负差异的柔性直流电网两段式行波保护

Two-section Traveling Wave Protection for Flexible DC Grid Based on Positive and Negative Difference of Voltage Refractive Wave Amplitude

针对柔性直流电网线路行波保护在长线故障下难以兼顾速动性和耐受过渡电阻能力的问题,提出了一种基于电压折射波幅值正负差异的两段式行波保护方案。首先,通过分析故障行波在线路上的传播过程,推导了各折反射波的表达式,得出了区内外故障下线路端口电压折射波幅值的正负差异特性。然后,基于该特性,提出了两段式行波保护方案,以传统行波保护判据构成保护第Ⅰ段,采用端口电压幅值及回升时间构成行波保护第Ⅱ段。最后,基于PSCAD/EMTDC仿真平台,验证了该保护方案的有效性。

Aiming at the problem that the traveling wave protection of the flexible DC grid line can not take into account the operation speed and the ability to withstand the transition resistance under the long-line fault,a two-section traveling wave protection scheme based on the positive and negative difference of voltage refractive wave amplitude is proposed.First,by analyzing the propagation process of the fault traveling wave on the transmission line,the expressions of each refractive wave are derived,and the positive and negative difference characteristics of the refractive wave amplitude of the line port voltage under the condition of internal and external faults are obtained.Then,based on these characteristics,a two-section traveling wave protection scheme is proposed,in which the first section is composed of traditional traveling wave protection criterion,and the second section is based on the port voltage amplitude and recovery time.Finally,based on the PSCAD/EMTDC simulation platform,the effectiveness of the protection scheme is verified.