A Wavelet Transform Method for Characterization of Voltage Variations

Short duration voltage variation is one of the most commonly encountered power quality disturbances. The severity is generally determined by the remaining voltage RMS magnitude and the duration of the disturbance. These are generally determined through the RMS measurement method, which at times faces difficulties especially with variations of very short duration. This paper proposes an alternative technique to effectively characterize voltage variations of all durations. It uses wavelet analysis to zoom into a high frequency band for the time information, and the fundamental frequency band for the magnitude change. It is shown to be effective even for very short interruption, which is difficult to determine using the RMS method. Compared to other wavelet methods, its low computational requirement makes it suitable for real-time application. Dynamic simulations were used to demonstrate the capability of this method.