Circulating currents and CM EMI reduction for interleaved three-phase VSC

This paper presents a method to reduce the circulating current and common-mode electromagnetic interference (CM EMI) in interleaved three-phase voltage-source converters (VSC). Use of coupled three-phase inductors is shown to generate large CM circulating currents among the parallel modules. To reduce this CM circulating current, a CM chokes is placed at the dc input of each module. A new method to reduce system CM filtering requirements is also presented. The proposed method uses CM capacitors connected between the ac and dc terminals to provide attenuation for conducted CM current emission at both the dc and the ac terminals. The method is particularly attractive for applications where both input and output EMI has to be controlled, and can be applied to individual VSC as well as multiple VSCs operating in parallel.