Voltage sag source identification method based on Hilbert-Huang transformation and wavelet packet energy spectra

Abstract

The invention discloses a voltage sag source identification method based on Hilbert-Huang transformation and wavelet packet energy spectra, and belongs to the field of electric energy quality analysis of electric power system. The method includes the steps: firstly, performing EMD (empirical mode decomposition) for a three-phase voltage signal to obtain IMF (intrinsic mode function) components; secondly, performing n-layer wavelet packet decomposition for the IMF components to obtain energy spectra of frequency bands; thirdly, setting a larger wavelet packet coefficient of low-frequency band energy into zero, and reconstructing wavelet packet coefficients corresponding to other frequency bands to obtain an IMF without low-frequency illusive components; finally, performing Hilbert transformation on the IMF without the illusive components to obtain an HH (Hilbert-Huang) spectrogram, and identifying voltage sag sources according to catastrophe points, amplitudes, harmonic waves and frequencies of the HH spectrogram. Different characteristics of different voltage sag sources can be identified from the HH spectrogram only by taking the amplitudes, the catastrophe points and the harmonic waves as characteristics, the voltage sag sources are differentiated, so that times of non-identification and mistaken identification are effectively decreased, and identification efficiency is improved.

Description

technical field [0001] The invention relates to a voltage sag source identification method based on Hilbert-Huang transformation and wavelet packet energy spectrum, which belongs to the field of power system power quality analysis. Background technique [0002] Voltage sag refers to an event in which the root mean square value of the power frequency voltage at a certain point suddenly drops in a short period of time, and its typical duration is 0.5~30 cycles. The International Electrotechnical Commission (IEC) defines it as falling to 90%~ of the rated value 1%, which is defined by the Institute of Electrical and Electronics Engineers (IEEE) as falling to 90% to 10% of the rated value. The rapid development of economy and technology has made complex electronic equipment widely used in power consumption departments, and many equipment are sensitive to short-term voltage changes. For example: short-term voltage sags will cause tripping of speed control equipment (amplitude dr...

AI Technical Summary

Problems solved by technology

[0007] The technical problem to be solved by the present invention is to overcome the problem that the voltage sag waveform cannot be identified by observation, and provides a voltage sag source identification method based on Hilbert-Huang transform and wavelet packet energy spectrum

Images