Low Frequency Oscillation Mode Identification Based on NMD Method in a High Hydro-ratio Power Grid
The speed governor problems in a high hydro-ratio power grid will lead to ultra-low frequency oscillations with the frequency below 0.1 Hz,which is mixed with the low frequency oscillation increasing difficulty to identify low frequency oscillation parameters.Therefore,an adaptive time-frequency analysis method-nonlinear mode decomposition(NMD) to identify the parameters of low frequency oscillations is proposed.The method can extract the time-frequency ridge according to the signal structure,obtained the harmonic parameters;identifying true harmonics of the corresponding components,the false mode components are eliminated.And it uses the spectral entropy characteristics of the extracted components to set a stop decomposition criterion,making the decomposed nonlinear mode(NM) components have practical physical significance.The oscillation parameters of each NM component are identified with Hilbert transform(HT).Finally,the method is analyzed and validated by self-synthesized signal simulation,the four-machine two-zone system simulation and the real data collected from the power grid.The effectiveness and feasibility of the proposed method are verified by the results.
High hydro-ratioultra low frequency oscillationtime-frequency analysisnonlinear mode decompositionHilbert transform
万方数据
维普
