For increasing the complex power grid

low-frequency oscillation research methods based on measurement are more and more attention. Among these methods

the fitting result of prony method is sensitive to noise

and the order of the model is difficult to be selected. The wavelet function is not easy to determine. EMD is a multi-resolution signal-processing method

it can be used non-stationary signals analysis. EMD is more and more used in extraction of the low-frequency oscillation parameters

but it has disadvantages such as model mixing. As more than two individual components in a signal with frequencies within an octave is indecomposable by frequency shift empirical mode decomposition (FS-EMD) method

to improve the frequency resolution and let FS-EMD more general

a refined frequency shift EMD(RFS-EMD) is presented. The proposed method is able to enlarge the component frequency ratios

and to ensure that the frequency does not turn over

so that the complex signal can be decomposed through repeating call this method. In its application to extracting model parameters of low frequency oscillation in 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 analysis results.