Common-mode EMI Noise Modeling and Reduction using Balance Technique for AC-DC-AC Traction Systems with Paralleled Power Modules

This paper proposes a common-mode (CM) noise suppression technique with the Wheatstone bridge balance circuit and a decoupling inductor in AC-DC-AC traction system with paralleled power modules. Since the EMI noise propagation paths in AC-DC-AC traction system with parallel power modules are complicated, a general CM equivalent circuit for above system is established in this paper. The EMI model is verified through experiment and simulation comparisons. Based on the understanding of the propagating mechanism of the CM noise in the whole system, the interactions between the rectifier subsystem and inverter subsystem are analyzed. The CM noise suppression in above system is often achieved by the EMI filters with trial and error method. In order to reduce the passive components' size and improve the noise attenuation capabilities, a Wheatstone balance circuit with a decoupling inductor technique is proposed to reduce the generated CM noise.