Enhanced wavelet-based method for modal identification from power system ringdowns

In this paper, a method to the analysis of low-frequency electromechanical oscillations (LFEOs) based on continuous wavelet transform (CWT) is presented. The complex Morlet CWT is employed to decouple power system ringdown signals into single oscillatory modes (OMs) in order to estimate their frequencies, damping ratios, relative amplitudes and phase shifts as well as to detect nonstationarities. End-effects of CWT may cause inaccurate estimation of relative amplitudes and phase shifts. To make up for this drawback, an optimization problem is formulated in a least-square sense. The method is applied to synthetic and simulated ringdown signals and results are contrasted to results from Prony analysis.