Enhancement of instantaneous power theory under unbalanced grid voltages condition using positive sinusoidal signal regulator

Many control strategies based on instantaneous power theory are presented to control active filters but instantaneous power theory based active filters can not compensate current harmonics properly under unbalanced grid voltages. In this paper, in order to use this theory under unbalanced voltages condition, a new control strategy based on positive sinusoidal signal regulator (PSSR) is proposed that leads to proper compensation under unbalanced grid voltages. First instantaneous power theory (p-q theory) and the reason of its improper operation under unbalanced voltages are discussed. Then the proposed control strategy is given with mathematical analysis. Finally, the simulation results, which carried out via PSCAD/EMTDC software, are given for balanced and unbalanced grid voltages conditions.