Investigations on the EMI of an electric vehicle traction system in dynamic operation

The implementation of high power electric traction systems in vehicles comprehensively affects the electromagnetic compatibility of these vehicles. Especially the operation of power electronic components beneath the conventional 12V electrical system is critical due to the disturbances produced by the electric traction system. These electric drives are normally supplied by a battery with nominal voltages of up to 800V. Due to fast switching processes in the drive inverter broadband EMI occur in the vehicle's High Voltage (HV) wiring system. Thus this system is built up completely isolated from the vehicle body and is thoroughly shielded. For equipotential bonding it is necessary that the shielding is connected highly conductive to the vehicle's chassis. Due to stray capacitances in the traction system components the broadband interferences can couple into other parts of the vehicle's electric system and affect on it. For EMC testing of these traction systems actually no fixed point of operation is defined in the standardization, but normally the drive is tested in a fixed operating point. Due to the fact that an electric vehicle is generally not operated in fixed states especially the EMI in dynamic operation is analyzed in this paper. One main goal is to identify critical modes in dynamic operation with respect to the EMI. For the investigation a Hardware in the Loop (HiL) setup of an electric vehicle traction system with the ability to variably simulate dynamic drive scenarios is used. The occurring EMI are measured using a Time Domain EMI Measurement system in order to analyze the EMI behavior and to indentify critical operating points during the dynamic operation of an electric vehicle.