Harmonic mitigation in transformers of twelve-pulse rectifier using active filter

Researchers proposed several techniques to reduce the harmonics present in the input current of 12-pulse rectifier. But the transformers used in the rectifier contain more low order harmonics in their input currents. In this paper a novel active filtering method for input current wave shaping of the transformers used in a 12-pulse rectifier is proposed. With the proposed method both the rectifier and transformers are shown to draw near sinusoidal input currents from the utility. This active filtering technique uses high switching frequency PWM Boost converter that shapes the input currents by eliminating high frequency harmonic components with the aid of small size LC filters. The size of the LC filters is reduced to a considerable extent with the proposed technique. Detailed design and simulation results are presented to show the effectiveness of the proposed method.