Identifying Trends Between Source Unbalance and Harmonic Emissions of an AC-DC Rectifier

The constantly evolving state of the power grid calls for some power quality-related measures to be reevaluated. Current measures in place to ensure acceptable levels of power quality only consider disturbances, such as harmonics and source unbalance, individually without taking into account their effects on one another. The work in this paper is dedicated to finding trends and correlations between source unbalance and harmonic emissions of an AC-DC rectifier by using a set of simulations. Rectifiers with two different load conditions are supplied by sources with up to 5% unbalance. The sources had their magnitudes and phase angles adjusted at random for 500 simulations per load condition. THD as well as all harmonics up to the 20th for each phase from each simulation were recorded and evaluated. Equations defining the upper and lower limits of THD and each odd harmonic as a function of source unbalance were developed. Equations like these can begin to be considered in power quality standardization related to harmonics and source unbalance.