Power quality monitoring and evaluation in power systems under non‐stationary conditions using wavelet packet transform

The purpose of this paper is twofold: (i) to propose a methodology to accurately evaluate power quality indices, and (ii) to highlight the importance of power quality monitoring services at different voltage levels of three‐phase power systems. The proposed methodology is based on wavelet packet transform (WPT) and is able to perform power quality analysis in three‐phase power systems operating under stationary and non‐stationary conditions, in the presence of both harmonics and unbalance. Several test cases are examined: synthetic voltage and current waveforms including noise, simulated test systems, a modified IEEE 13‐bus test feeder, as well as experimental tests. The obtained results in all cases demonstrate the accuracy and the effectiveness of the proposed WPT method and its superiority over fast Fourier transform to accurately evaluate power quality indices in case of non‐stationary disturbances.