短时傅里叶变换和S变换用于检测电压暂降的对比研究

针对电压暂降的特征值检测问题,介绍了短时傅里叶变换(STFT)和S变换两种时频分析法,并对两种方法进行了对比分析。在STFT变换中选取不同窗宽的窗函数对同一电压暂降信号进行时频分解,分析不同窗宽对检测结果的影响。提出用时频等值曲线定位暂降的起、始时刻,用基频幅值曲线检测暂降幅值,用相位跳变曲线判定暂降发生时相位是否跳变。仿真结果表明,在STFT变换中窗口越小,检测结果越准确;与STFT变换相比,S变换的检测结果更准确,并且抗噪声能力强,有助于电能质量的治理。

Comparative study of STFT and S transform on detecting voltage sag

In order to deal with the detection problem of the voltage sag features, this paper introduces two kinds of time-frequency methods, the STFT and S-transform, then the two methods are compared and analyzed. The different widths of the window function in the STFT is selected to decompose the same voltage sag signal in time-frequency. And the effect on the test results of different width is analyzed. This paper proposes to use time-frequency isopleth to position the start and end time of the sag, use the fundamental frequency amplitude curve to detect the sag amplitude, and use the phase hopping curve to determine whether the phase hopping happened when the sag occured. The simulation results show that the smaller the window is in STFT, the more accurate the test results are; compared with STFT transform, S-transform test results are more accurate and has high anti-noise ability, which is helpful to power quality management.