Modeling of electric power system in electric vehicles

The market for partly or fully electrified vehicles is expanding fast. The number of sources and loads that are connected to the vehicles traction voltage systems (TVS) increase and thus also the EMC requirements on these sources and loads. These requirements should make sure that neither function nor lifetime of any source or load is severely affected by another. The EMC requirements include both Common Mode (CM) and Differential Mode (DM) voltages and currents created by the modulation of the various power electronic converters involved as well as intentional and parasitic impedances of the TVS and reach up to at least 10 MHz for CM and 100 kHz for DM. This paper presents an initial study on the properties of both the CM and DM currents and voltages of the TVS as a function of the Pulse Width Modulation (PWM) and the selection of Y-capacitances, all with parameters relevant for a large full electric bus. The conclusions point out a recommendation for selection of Y-capacitances of a power electronic converter vs. the known parasitic capacitance to ground of the load, insights in the asymmetry of the CM currents and load interaction in the DM currents of the TVS.