柔性直流系统短路故障网络阻抗建模与时频特性诊断方法研究

针对柔性直流系统直流侧短路故障诊断难题,文章从故障网络精确建模和暂态特征信号分析两个方面展开研究,并提出了阻抗网络暂态响应时频特性关联度的故障诊断方法。该方法通过向柔性直流系统线路入口处注入脉冲电压作为激励,实时提取所产生的暂态电流分量,经不同尺度的Mexican Hat变换得到时频能量序列,并构造反映故障网络暂态响应时频能量谱矩阵。同时,建立柔性直流系统精确模型,模拟不同故障点经不同大小电阻的短路故障,构建完整故障样本及其时频特征库,经相似度计算可选出与实测故障特征最相近的样本,确定故障点位置和估计短路电阻大小。最后,对上述原理方法进行算例分析,并与时域方法比较,结果表明文章所述诊断方法及其判据更为准确有效,相关原理正确可行。

Research on short circuit fault diagnosis method of dc line based on time-frequency characteristic correlation degree

Aiming at the problem of DC side short-circuit fault diagnosis of flexible DC system, this paper conducts research from accurate modeling of fault network and analysis of transient characteristic signals, and proposes a fault diagnosis method based on the correlation of time-frequency characteristics of impedance network transient response. The method injects a pulsed voltage into the DC system line entrance as a stimulus, extracts the transient current component generated in real time, and obtains the time-frequency energy sequence through different scales of the Mexican Hat transform. And the energy spectrum matrix which can reflect the time-frequency characteristics of the transient response of the fault network is constructed. At the same time, an accurate model of a flexible DC system is established to simulate short-circuit faults with different resistances at different fault points, and a complete fault sample and its time-frequency characteristic database are constructed. The similarity calculation can select the closest sample to the measured fault characteristics to determine the fault Point location and estimated short-circuit resistance. Finally, an example analysis of the above-mentioned principle and method is performed, and the comparison with the time-domain method shows that the diagnostic method and its criteria described in the article are more accurate and effective, and the relevant principles are correct and feasible.