A new power quality disturbance detection method based on the improved LMD

A new signal analysis method of non-linear, non-stationary-local mean decomposition (LMD) was introduced. The advantages and disadvantages of the application of LMD in the disturbance signal detection were analyzed. On this basis, the paper presented an improved local mean decomposition (ILMD) power quality disturbance detection and time-frequency analysis method. The method was composed of two parts: LMD and Hilbert transform. Firstly, to extract the product function (PF) of the signal based on LMD, and to obtain the instantaneous amplitude of the signal from the PF components of the amplitude modulation function. Then, to apply the Hilbert transform to obtain the instantaneous frequency of PF. The improved LMD method could effectively locate the beginning and ending time of the disturbances occurred and overcome the deficiencies of the LMD positioning capability. By using the method, the curves of the instantaneous amplitude had less distortion in wave head and that of the instantaneous frequency had shorter swings, and detection results for magnitude and frequency of disturbance signal had higher accuracy, compared with the HHT method. The simulation and experimental results of the switch voltage analysis of capacitor group from 500 kV transformer substation prove the feasibility and effectiveness of the proposed method. © 2014 Chin. Soc. for Elec. Eng.