Indirect control in Active Power Filters

This paper presents a three-phase Active Power Filter (APF) to improve power quality in grid based on indirect control strategy. Knowing the fact that the main problems in grid are: the total harmonic distortion (THD), the power factor (PF), and the current unbalance, the indirect control strategy offer a solution to improve the power quality from this point of view. The analyzed control strategy allows the line current at the point of common coupling (PCC) in steady-state to be balanced, in phase with the voltage and sinusoidal even when the load current is unbalanced and non-sinusoidal. The indirect control strategy [1] proposes not to compute the fundamental of the load current but to impose a sinusoidal reference for the grid current. The computational effort is smaller than the classical theory like instantaneous power [2], [9], [10], synchronous frame reference [3], [11] etc. Simulation results show the validity of the innovative control strategy presented in this paper.