Harmonic mitigation in transformers of a twelve-pules rectifier using active filter

Abstract

In this thesis an active filtering scheme for input current wave shaping of the transformers used in a 12-pulse rectifier system has been proposed, analyzed and compared with passive filtering technique. Both ac and dc filter have been designed and the most appropriate position of the ac filter has been checked and determined in passive filtering scheme. With the active filtering scheme high switching frequency PWM Boost converter has been used at the output of the ac to dc rectifier to shape the input currents by eliminating high frequency harmonic components with small sized filters. The number of Boost stages and its/their position at the output stage have been found out to get a good solution to the problem. With the proposed method the transformers as well as the rectifier draw near sinusoidal currents from the utility. Performance evaluation of the proposed scheme has been carried out and compared with the passive filtering scheme under similar conditions. The outcome is expected to provide a better solution to harmonic mitigation of input current in transformers of a twelve-pulse rectifier.