Topologies of three-phase rectifier with near sinusoidal input currents — A comparative analysis of power quality indices using FFT and DWT

The traditional method used to detect and localize power quality disturbances by Fast Fourier Transform (FFT) can provide only amplitude - frequency information, but looses time information. In evaluating power supply quality, the FFT-based indices present different limitations. This paper proposes a set of four indices based on Discrete Wavelet Transform (DWT), such as total harmonic distortion, equivalent distortion index, K-factor, and crest factor that can be also applied for non-stationary signals analysis, in unbalanced three-phase systems with non-sinusoidal conditions. In the comparative analysis of Power Quality Indices (PQIs) definitions, these two instruments were used for the three-phase power systems with non-linear loads: three rectifier topologies with near sinusoidal input currents (RNSIC).