Conducted Electromagnetic Interference (EMI) Reduction Techniques in Power Electronic Systems

This dissertation investigates the reduction techniques for conducted electromagnetic interference (EMI) in power electronic systems. The aim of this dissertation is to establish a comprehensive framework for approaches to reduce conducted EMI in power electronic systems. Four essential parts are presented in the dissertation. In the first part, the principle of active EMI filter is thoroughly discussed and a transformer-less feedforward-controlled active filter design is presented. In the second part, a novel switch topology aimed at producing zero common-mode (CM) voltage in voltage source inverter-fed (VSI-fed) motor drives is developed. The proposed switch comes in a compact design and features the merit of plug-and-play. In the third part, an optimized modulation that makes full use of the proposed switch topology in the second part is developed. The optimized modulation has the potential to minimize both the amplitude and frequency of CM voltage in a VSI-fed motor drive. In the fourth and final part, a comprehensive study on conducted EMI suppression in an active front-end (AFE) drive is presented. A practical implementation of random switching frequency for AFE rectifier/converter is developed and tested to demonstrate the effectiveness of random modulation in shaping the conducted EMI spectrum.