- 1992 IEEE. In this paper an Active Power Filter is proposed for balancing unbalanced loads. A 3-phase, PWM ac to dc converter topology with inductive energy storage is controlled to continuously inject desired negative sequence currents into the system to achieve balancing of continuously varying unbalanced loads. The principal of operation is as follows: the negative sequence components of the load currents are measured in magnitude and in phase and the PWM-controlled Active Power Filter is controlled to inject currents opposite to these quantities, thereby achieving the balancing function. The operation of the proposed system along with the selection of the Active Power Filter components are discussed in detail. Finally, experimental filter operation is verified for an unbalanced load.