Analysis on vibration signal of hydropower unit based on local mean decomposition and Wigner-Ville distribution
1.Engineering Research Center of Renewable Power Generation Technologies, Ministry of Education, Hohai University, Nanjing, Jiang-su 210098, China; 2.College of Energy and Electrical Engineering, Hohai University, Nanjing, Jiangsu 210098, China
Abstract：For a transient signal of a hydropower unit, the existing processing methods for non-stationary signal are unable to get a high time-frequency resolution currently, and the time-frequency characteristics cannot be extracted effectively as well. Therefore, a new method, in which the local mean decomposition(LMD)and Wigner-Ville distribution have been combined together, was proposed to ana-lyze vibration signals of hydropower unit; further it was applied into the analysis on run-out signals in the upper guide bearing of a hydropower unit in its load rejection operation. According to comparison of the time-frequency spectra determined respectively by short-time Fourier transform, wavelet transform and Wigner-Ville distribution, the spectrum given by the present method can capture the instantaneous amplitude and frequency of a transient signal directly. This implies that the proposed method has taken the advantages of both LMD and Wigner-Ville distribution. Meanwhile, the inherent defect, i.e. cross-term interference in Wigner-Ville distribution has been removed. This new method can be used as an effective analysis tool for condition monitoring and fault diagnosis of hydropower units in future.
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