Extraction of Low Frequency Oscillation Parameters Based on Refined Frequency Shift Empirical Mode Decomposition

For large complex power systems,low-frequency oscillation research methods based on measurements have received much attention.Empirical mode decomposition(EMD) is a multi-resolution signal-processing method,and it can be used for non-stationary signals analysis.Although EMD is frequently used in the extraction of low-frequency oscillation parameters,it has disadvantages of model mixing,etc.As more than two individual components in a signal with frequencies within an octave can be indecomposable by frequency shift EMD(FS-EMD) method,a refined frequency shift EMD(RFS-EMD) is presented to improve the frequency resolution and make FS-EMD more robust.The proposed method is able to enlarge the component frequency ratios,and ensure that the frequency does not turn over,so that the complex signal can be decomposed through repeating this method.In its application for extracting model parameters of low frequency oscillation in a power system,this method proves fairly effective in extracting model parameters in a signal with several frequencies within an octave respectively,such as frequency,amplitude,phase and damping ratio,etc,as shown by numerical simulation and case study results.