Measurement and mitigation of electromagnetic emissions of propulsion inverters for electric vehicles

A key characteristic of today’s switched mode power converters are their conducted electromagnetic emissions (EMEs). To apply mitigation techniques with minimal weight, volume and costs, a converter’s EME should be identified by simulations and pre-compliance conducted emission measurements as early as possible within a converter's design process. This work investigates methodologies for EME simulations and measurements. A combined simulation of functional circuit behavior and parasitic elements are used to cover all relevant phenomena. A test bench, adapted from CISPR25 Ed.4 regulations, is built for conducted-emission measurements. On the test bench, the induction machine at the AC side of the inverter is replaced by a passive artificial machine load. A common- and differential-mode separator, which includes the VHF broadcast frequency band up to 108MHz, is developed. Investigating four propulsion inverter variants, the impact on the EME of different semiconductor technologies (silicon IGBTs or silicon carbide MOSFETs), converter topologies (two-level or three-level) and DC-link voltages (400V or 800V) is identified. DC filters to mitigate the EME are optimized for each inverter prototype with an automated design tool. To define metrics for the optimization, a detailed cost model for filters in an electric vehicle is developed. A filter demonstrator for the silicon carbide inverter is fabricated by using a flexible, rapid-design approach based on 3D-printed filter brackets, which is evaluated using the aforementioned test bench