Time-varying power quality in unbalanced three-phase systems

This paper investigates the effectiveness of implementing the un-decimated wavelet transform (UWT) in the computation of reactive power in three-phase system subject to time-varying disturbance. The advantages of this decimation-free wavelet transform are highlighted and the formulation of the reactive power in the un-decimated wavelet domain is presented based on two reactive power metering approaches namely; 1) “non-quadrature” and 2) “quadrature” approaches. Various case studies including different loading conditions and/or time-variant/time-invariant disturbances are presented to exemplify the effectiveness of using the un-decimated wavelet in the reactive power measurement in both balanced and unbalanced three-phase systems. The results of the analysis are compared to the reactive power values based on the decimated wavelet transform (DWT) and conclusions are presented.