Hybrid filter operation during nonlinear lead current pulsations

Examines some basic aspects of hybrid filters, operating effectively when current pulsations of a non-linear variable load occur. The operation of two hybrid filter systems, each equipped with an active power filter, corking as: a) a controlled additional current source, b) a controlled additional voltage source, recognized by the authors in previous publications as the most advantageous solution has been examined, For both systems, vectorial equations in alpha,beta co-ordinates, describing their operation, have been presented. On the basis of these equations a common frequency model of three-phase three-wire hybrid filters has been elaborated. This model has been used for the evaluation of the filtration efficiency of line current harmonics, taking into consideration the applied methods and algorithms to separate filtered harmonics, above al at a pulsating load current. Some conclusions from the theoretical analysis have been verified by simulation of a line loaded by converter with an output current pulsating at frequencies 10 and 20Hz.