Classification of short-duration voltage variations using wavelet decomposition based entropy criteria

Voltage sag, swell, and interruption are the variations in supply voltage existing for a short duration. There is a necessity for an accurate analysis of voltage signals as the magnitude of supply voltage should be within an acceptance range. Wavelet transform, a signal processing technique, can be used to extract information about the disturbances in voltage signals. Short-duration voltage variations are decomposed using multiresolution analysis. The original voltage signals are decomposed into approximation and detail components at various levels by using discrete wavelet transform. Decomposition is carried up to seven levels and Daubechies 4 (db4) is used as prototype function. Different entropy criteria are applied for the coefficients of obtained approximation and detail components. The different entropy criteria include Shannon, log energy and norm entropies. One-dimensional wavelet decomposition analysis is carried out in MATLAB using the command line functions to present classification of short-duration voltage variations in a distribution system using entropy criteria.