Load symmetrization in supply systems with distorted line voltage

Active power filters can be successfully implemented to reduce fundamental reactive power and harmonic distortion in supply systems. Consecutively, active filters in three-phase systems can eliminate unbalance, caused by mutually noncompensated harmonic currents. Even more, with a proper control algorithm, active filters can improve symmetrical conditions of unbalanced fundamental load currents. This paper introduces a control method for a three-phase parallel active power filter. Simulation results are presented, with a special concern on the filter's synchronization to the line voltage. Additionally, a filter can be applied as a DC source.