Spectrum Estimation of Non-Stationary Signals in Power Systems

Time-varying spectra of non-stationary time-series commonly used are spectrograms from the Short-Time Fou- rier Transform (STFT). The most prominent limitation of the Fourier Transform is that of frequency resolution. To over- come the limitation the Wavelet Transform, Wigner-Ville Distribution and the Min-Norm subspace method have been applied for spectrum estimation of non-stationary signals caused by switching on capacitor banks and by a short circuit at the output of a frequency converter. Investigation results confirm the advantages of the advanced methods.