基于故障电压反行波拟合残差的柔性直流线路单端行波保护

Non-unit Traveling Wave Protection for Flexible DC Lines Based on Fitting Residual of Fault Voltage Reverse Traveling Wave

为解决柔性直流线路保护在灵敏性和速动性上所面临的问题,该文从故障行波时域波形差异的角度出发,对柔性直流电网线路故障反行波的波形特性进行数学解析,得到区内、外故障下故障电压反行波时域表达式的差异;为提取区内外故障行波波形的特征差异,利用列文伯格–马夸尔特法(Levenberg-Marquardt)以区外故障表达式作为标准波形进行数据拟合,进而提出了一种基于故障电压反行波拟合残差大小的柔性直流线路单端行波保护方案;最后,基于PSCAD/EMTDC的仿真验证,表明该方案能在1ms/20kHz的数据窗内快速正确地识别直流线路所有故障,具有较高的速动性、灵敏性和可靠性,且在噪声干扰以及限流电抗器值较小时都具有较强的鲁棒性。

To solve the problems in the sensitivity and rapidity of the flexible DC lines protection,starting from the perspective of the time domain waveform differences of the fault traveling waves(TW),this paper makes a mathematical analysis of the waveform characteristics of the fault reverse TW after the faults of the flexible DC power grid lines,and obtains the difference between the time domain expressions of the fault voltage reverse TW under the internal and external faults.In order to extract the characteristic difference between the fault TW waveforms inside and outside the area,the Levenberg-Marquardt method is used for data fitting according to the fitting function corresponding to the external faults.Then,a non-unit TW protection for the flexible DC lines based on the fitting residual size of the fault voltage inverse TW is proposed.Finally,the simulation based on the PSCAD/EMTDC shows that the scheme is able to identify all the faults of the DC lines quickly and correctly within the data window of 1 ms/20 k Hz with high rapidity,sensitivity and reliability,and that it has strong robustness against the noise interference and small current limiting reactor value.