基于单端暂态电流的MMC-HVDC输电线路保护方案研究

Research on MMC-HVDC Transmission Line Protection Scheme Based on One Terminal Transient Current

高效可靠的直流线路保护是模块化多电平换流器高压直流输电(high voltage direct current transmission based on modular multilevel converter,MMC-HVDC)系统安全经济运行的重要保证。为了快速检测直流输电线路故障并识别故障类型,该文提出一种基于单端暂态电流的MMC-HVDC直流输电线路保护方案。当直流输电线路发生故障时,线路保护安装处电流频率成分丰富,基于经验模态分解的时频局部化特性,利用固有模态能量熵评估电流能量在频域分布的离散度,构建直流侧故障判据,以区分交流侧和直流侧故障。直流线路电流在直流线路双极短路、单极接地和断线故障时分别对应上升、平稳和下降趋势,利用滑动平均滤波提取电流变化趋势,构造了故障类型识别判据。RTDS仿真结果表明,该方案在不同故障位置和过渡电阻下均能够快速可靠地检测直流线路故障并准确识别故障类型。

DC transmission line protection plays an important role in the secure operation of the high voltage direct current trar/smission based on modular multilevel converter （MMC-HVDC）. To quickly detect DC line faults and identify fault types, a protection scheme for MMC-HVDC transmission line based on one terminal transient current was proposed. By using empirical mode decomposition （EMD） technology and intrinsic mode energy entropy, the energy distribution dispersion of transient current in frequency domain was quantified. The intrinsic mode energy entropy was employed as a fault criterion to distinguish DC line faults from AC area fault. The trend of transient current, which can be extracted by using the moving average filter, is obviously different under various DC line fault types. Based on this feature, the DC line fault type was identified. Simulation results in RTDS demonstrate that the proposed scheme is able to detect and classify MMC-HVDC transmission line faults under different fault conditions.