Solid State Transformer Design to Reduce Common Mode Conducted EMI

The CLLC resonant converter using wide bandgap devices has been gaining popularity as an SST, which is widely used in microgrid and transportation electrification applications. However its high switching frequency causes electromagnetic interference (EMI). This paper presents a novel CLLC topology featuring a balanced circuit in the CLLC resonant tank to produce zero common mode voltage, thus reducing the SST conducted EMI. A SiC CLLC SST was built in the laboratory and its conducted EMI measured. The experimental measurements demonstrate that the new CLLC SST achieves 10-20 dB of CM EMI attenuation with respect to the state-of-the-art CLLC SST, where the resonant tank circuit is unbalanced.