Identification of Low-Frequency Oscillations in Power Systems Based on Improved HHT

In order to solve mode mixing, an improved HHT (IHHT) is proposed to identify modes of low frequency oscillation (LFO) in power systems. Firstly, by means of Fourier transform the approximate frequency range of every mode is determined; then methods such as masking signals or filters are chosen to separate mixing modes. Finally mode parameters can be calculated by linear least quadratic fitting. Simulated signals are analyzed by conventional HHT and IHHT, results show that IHHT can correctly separate mixing modes and identify modes parameters, results are in advance of traditional algorithms, so the proposed algorithm is suitable to mode identification of LFO.