【摘要】 从信号处理的角度而言,特快速暂态过电压(VFTO)是非平稳信号,传统的Fourier变换不适合用于对其进行频谱分析。为此,结合VFTO波形频带宽、频率成分丰富等特征,寻求了适用于VFTO频谱分析的时频分析方法。对比分析了短时Fourier变换、Wigner-Ville分布、伪Wigner-Ville分布、S变换及广义S变换5种时频分析方法在VFTO合成信号频谱分析时的性能,结果显示广义S变换在高、低频段的时频分辨率能够同时达到较好水平。然后利用广义S变换对VFTO实测波形进行频谱分析,给出了VFTO各频率分量的幅值—时间曲线。曲线显示VFTO各频率持续时间不一,频率越高,其幅值衰减越快、持续时间越短,进一步论证了广义S变换应用于VFTO频谱分析的适用性和可行性。更多还原

【Abstract】 From the perspective of signal processing, very fast transient overvoltage(VFTO) is non-stationary signal, hence traditional Fourier transform is no longer suitable for its spectral analysis. Considering the characteristics of VFTO waveform, including wide frequency band and complex frequency components, we tried to figure out a time-frequency analysis method that is adaptive for the spectral analysis of VFTO. We compared the performance of five time-frequency analysis methods, namely short-time Fourier transform, Wigner-Ville distribution, Pseudo Wigner-Ville distribution, S transform and generalized S transform, in the spectral analysis of VFTO synthetic signals. The results show that generalized S transform has its time-frequency resolution reached higher level than the other methods at both high frequencies and low frequencies. Then we applied generalized S transform to the spectral analysis of measured VFTO waveforms, and obtained amplitude-time curves of each VFTO frequency component. The curves show that the VFTO frequency components have various durations; the higher the frequency is, the faster the amplitude attenuates and the shorter the duration is. This further demonstrated that generalized S transform was applicable and feasible to the spectral analysis of VFTO.更多还原