Analysis of real-world power quality disturbances employing time-frequency distribution

The traditional method for the analysis of power quality (PQ) disturbances is fast Fourier transform (FFT) which suffers from spectral leakage phenomenon, and results in erroneous assessment in the presence of nonstationary PQ disturbances. Also, it cannot provide any time information as PQ indices are computed in the frequency domain only. Regarding the limitations of the FFT, in this paper Page time-frequency distribution (TFD) method is utilized for the analysis of three-phase nonstationary, nonsinusoidal, and unbalanced PQ disturbances. Utilizing the Page TFD technique, PQ indices such as effective rms voltage and current, apparent power, active power and power factor are redefined in the time-frequency domain, and the efficacy of the proposed method is evaluated by applying it to a synthetic and two real-world PQ disturbances provided by National Renewable Energy Laboratory (NREL). The analysis results show that the proposed method provides more accurate results than the FFT, and time-varying signature of the real-world PQ disturbances under nonstationary, nonsinusoidal, and unbalanced operating conditions.