A power converter for an electrostatic precipitator using SiC MOSFETs

In this paper, the authors describe the design of an 80kW power converter for an electrostatic precipitator using SiC MOSFETs. The structure of the converter is based on the series parallel resonant topology, PRC-LCC, with a capacitor as output filter. This topology can cope adequately with the parasitic elements of the step-up transformer involved in the application. The SiC switches present lower switching, EON and EOFF, and conduction, RDS against VCE, losses than Si based IGBTs. Therefore, it is possible to operate the converter at higher switching frequencies, and/or support hard switching techniques. The control has been set to maintain the resonant current in phase with the inverter voltage, as a strategy to minimize the resonant current itself and the reactive energy circulating in the resonant tank. This operation mode imposes hard switching in one of the inverter legs, but minimizes switching current maintaining losses under control. The experimental setup delivers 80 kW with an estimated efficiency of 98%. The paper also analyzes theoretically the large and small signal models of the converter. The analysis is supported with a complete set of experimental waveforms and Bode diagrams.