Abstract Aiming at the problems currently existing in transmission line protection for modular multilevel converter (MMC) based high voltage direct current (HVDC) grids, this paper proposes an improved single-ended fault detection scheme for MMC-HVDC transmission lines. The proposed scheme is based on the frequency-domain attenuation rate of the initial voltage traveling wave (IVTW). Firstly, the values of the IVTWs generated by the internal and external faults are calculated respectively based on the equivalent model of the four-terminal MMC-HVDC grid. Due to the boundary effect of DC inductors installed on both ends of DC lines, the attenuation rates of IVTWs with the increase of the frequency under internal and external faults have different characteristics. The detail coefficients of the IVTW in different frequency bands are extracted by stationary wavelet transform at different scales, and the amplitudes of the IVTW in different frequency bands are quantified by wavelet transform modulus maximums (WTMMs) at corresponding scales. A criterion for identifying internal and external faults is constructed based on the square of the frequency-domain equivalent attenuation rate of the IVTW. Lastly, simulation results under diverse fault conditions verify the effectiveness of the proposed fault detection scheme.

中文翻译：

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一种改进的基于单端频域的MMC-HVDC输电线路故障检测方案

摘要 针对目前基于模块化多电平换流器（MMC）的高压直流（HVDC）电网输电线路保护存在的问题，提出了一种改进的MMC-HVDC输电线路单端故障检测方案。所提出的方案基于初始电压行波（IVTW）的频域衰减率。首先，基于四端MMC-HVDC电网的等效模型，分别计算了内部和外部故障产生的IVTW值。由于安装在直流线路两端的直流电感器的边界效应，内部和外部故障下IVTW的衰减率随着频率的增加具有不同的特性。通过不同尺度的平稳小波变换提取不同频段IVTW的细节系数，并通过相应尺度的小波变换模最大值(WTMMs)量化不同频段IVTW的幅度。基于IVTW的频域等效衰减率的平方，构建了用于识别内部和外部故障的判据。最后，不同故障条件下的仿真结果验证了所提出的故障检测方案的有效性。基于IVTW的频域等效衰减率的平方，构建了用于识别内部和外部故障的判据。最后，不同故障条件下的仿真结果验证了所提出的故障检测方案的有效性。基于IVTW的频域等效衰减率的平方，构建了用于识别内部和外部故障的判据。最后，不同故障条件下的仿真结果验证了所提出的故障检测方案的有效性。