Harmonic analysis of power quality indices based on DWT using three-phase modern converters

The common method used for power quality disturbances detection, represented by the Fast Fourier Transform (FFT) can provide amplitude-frequency information but looses time information. A more efficient tool is considered Discrete Wavelet Transform (DWT) that can be also applied to unbalanced three-phase systems with nonlinear loads, in non-sinusoidal conditions. It also analyses the signal in a time-frequency domain by dividing the frequency spectrum into straps or levels, using windows of variable duration, dependent on the frequency band. In the harmonic analysis of Power Quality Indices (PQIs) three rectifier topologies with near sinusoidal input currents (RNSIC) were used. This rectifier is a classic type of a three-phase bridge rectifier with parallel diode capacitors and serial inductors attached.