Research on Detection Method of Low Frequency Oscillation Signal in Power System

As an adaptive signal processing method, Hilbert-Huang Transform (HHT) has been widely used in power system. However, when adjacent components are relatively close to each other, mode mixing problem can be easily caused in the decomposition process for EMD, so low-frequency oscillating components can't be effectively extracted. An improved EMD algorithm aiming at the analysis of low-frequency oscillations is introduced in this paper. First, by injecting high-frequency harmonic into the original low-frequency oscillation signal, the distribution of extreme value has been changed, and then the signal is decomposed by EMD. The sub-sequences obtained by EMD decomposition are transformed by Hilbert transform to obtain the modal parameters of low-frequency oscillation. The test signals and simulation examples prove that the injection of high-frequency harmonic could effectively solve the mode mixing problem in the EMD decomposition and provide a method for low-frequency oscillation analysis in the power system.