计及谐波次自然频率和VMD的混合线路故障测距

基于行波自然频率的故障测距方法依赖于对主自然频率的准确提取，然而针对架空线-电缆的混合线路时，由于线路波阻抗差异且行波折返射较多，会产生混叠的自然频率频谱。为此，一方面需要有效消除频谱混叠，另一方面仅依靠单一的主自然频率进行测距，其提取结果不能得到保证。基于此，本文提出了一种考虑谐波次自然频率和使用VMD算法的混合线路测距新方法。该方法首先对行波信号进行EMD分解，利用Hurst指数筛选IMF作为VMD分解的模态参数，准确地分解了行波信号；然后引入MUSIC算法对VMD分解结果进行频谱分析，提取出故障信号主自然频率及其谐波次频率；最后利用其对应关系计算出故障距离。针对混合线路的EMTDC仿真分析，验证了该方法能够有效消除频谱混叠，并且提高了基于行波自然频率测距方法的可靠性。

Considering Harmonic Subharmonic Natural Frequency and VMD Hybrid Line Fault Location

The fault distance measurement method based on traveling wave natural frequency depends on the accurate extraction of the main natural frequency. However, for the overhead line-cable hybrid line, due to the difference of the line wave impedance and the number of traveling wave foldback shots, aliasing spectrum will be generated.For this reason, on the one hand, it is necessary to effectively eliminate spectrum aliasing, and on the other hand, relying only on a single primary natural frequency for ranging, the extraction results cannot be guaranteed. Based on this, this paper proposes a new hybrid ranging method that considers the harmonic natural frequencies and uses the VMD algorithm. The method firstly decomposes the traveling wave signal by EMD, and uses the Hurst exponent to screen the IMF as a modal parameter for VMD decomposition so as to avoid over-decomposition of the signal; then a MUSIC algorithm is introduced to perform spectrum analysis on the VMD decomposition result to extract fault signals. The frequency and its harmonic frequency. Finally, using its corresponding relationship to calculate the fault distance.The EMTDC simulation analysis of the hybrid line verifies that this method can effectively eliminate the spectrum aliasing and improve the reliability of the method based on traveling wave natural frequency ranging.