This paper presents a three-phase four-wire active power filter controlled under an energyapproach. For active power filter implementation, a nonconventional converter topology is presented and analyzed. With this topology, and considering harmonics and imbalances in utility voltage and load current, power requirements on the active power filter are studied. From this study, a controller based on the energy state of the system is designed. In this paper, an analytical study and verification by simulation are conducted.