The Detection of Voltage Flicker Based on Complex Wavelets

Abstract

The discrete wavelet transform based on the orthogonal wavelet bases has the disadvantage of shift-variant. In this paper, using the compactly supported dyadic orthogonal real-valued wavelet bases to construct the compactly supported dyadic orthogonal linear phase complex wavelet (LCW) bases in terms of alternately lifting scheme. Linear phase complex wavelet can separate the envelope of the flicker signal. The core of the method is a pair of Hilbert transform including the flicker signal in wavelet field is come into being, i.e. a pair of quadrature components with the same amplitude and the same frequency can be used to realize the demodulation of an amplitude modulated voltage flicker signal. Simulation experiments show the method proposed has the characteristic of shift-invariant comparing with the traditional discrete wavelet transform, result of separating envelope of the flicker signal is independent of initial time recording signal.

The Application of Mathematical Morphology Filter in Voltage Flicker Detection

“…The voltage fluctuation and flicker is a steady-state power quality, the research to the voltage fluctuation and flicker is usually based on amplitude modulation wave frequency modulation of the carrier as the model and the research object. For multiple frequency voltage fluctuation and flicker using wavelet transform to analyze it [1][2]. Due to the change of voltage flicker signal frequency is low, producing flicker signals of harmonic component is usually between the power frequency voltage frequency 50 Hz or near the frequency doubling harmonic component, it put forward higher requirements to the flicker signal sampling frequency and the selection of wavelet decomposition scale, otherwise it may cause the modulation frequency mixing phenomenon, especially for containing multiple frequency flicker signal wavelet transform directly.…”