HARMONIC CURRENT REDUCTION IN 3-PHASE BRIDGE-RECTIFIER CIRCUITS USINGCONTROLLED CURRENT INJECTION

This paper describes further development of the novel current-injectio n scheme devised by the authors for attenuating line current harmonics in bridge-rectifier circuits, The previous passive filters are replac ed by controlled filters connected between the bridge-rectifier output and the star point of the transformer secondary, These filters are us ed to inject controlled third harmonic currents into the transformer w indings, Variations in bridge working conditions, due to changes in ei ther load or bridge delay angle, lead to corresponding changes in the filter operating conditions if the harmonic attenuation is to remain o ptimal, The control law for the filters has been derived and the effec tiveness of the new method confirmed by both simulation and laboratory tests.