EMI Reduction at the Source in WBG Inverters: A Comparative Study of Spread-Spectrum Modulation and Auxiliary Switching Leg Techniques

Effective electromagnetic interference (EMI) filters are required by switching converters to comply with conducted emission regulations. However, these filters often pose significant challenges, being expensive, bulky, and heavy. Such an issue is further aggravated with the latest generation of wide band gap (WBG)-based power converters. Reduction of the filter size can be achieved through conducted EMI mitigation techniques that address emissions at the source, particularly at low frequencies. Spread-spectrum modulation (SSM) has gained increasing interest to mitigate EMI, as it does not require any hardware alterations. This article investigates the effectiveness of the SSM in case of WBG traction inverters, where the switching frequency remains in the tens of kilohertz. In addition, the use of an additional switching leg to reduce the EMI was also investigated. A comparative analysis of these two techniques and their effectiveness in the common mode (CM) conducted EMI suppression is carried out. Experimental results are provided demonstrating the feasible CM conducted EMI reduction. It was found that the EMI peak at 160 kHz decreased by 2 dB in the SSM case and by 25 dB in the additional leg case.