New control algorithms for series and shunt three-phase four-wire active power filters

This paper presents the general equations that relate the new concepts of instantaneous active and reactive power theory and the well known theory of Symmetrical Components, for the case of 3-phase 4-wire systems, where zero sequence components and harmonics may be present in both voltages and currents. Based on these equations, new control algorithms for 3-phase 4-wire shunt and series active filters for unbalanced power systems are proposed and validated through simulations. The control algorithms presented here are very important for active power filter design and also for FACTS technology reactive power compensators