Development of a passive impedance network for modeling electric vehicle traction batteries for EMI measurements

Abstract

Due to the powertrain electrification in electric- and hybrid vehicles enormous challenges arise considering the electromagnetic compatibility (EMC) of the vehicles. The power electronic components used produce high broadband interferences possibly affecting vehicle components located in the 12V system. In order to meet these challenges the traction system is built up thoroughly shielded and isolated from the vehicle body. Considering the field of standardization all actual vehicle standards are revised in order to integrate these new powertrain components. On component level the actual version of CISPR 25 includes an annex where the powertrain components, new measurement setups and revised limits are addressed. For nearly all setups described, a DC power supply is needed to supply the DUT inside the shielded chamber. As every component like e.g. drive inverter, on-board charger or electric air conditioning systems are supplied by the traction battery in the vehicle, this source in needed for the test setup. Beside the power supply an essential feature of the source should be its impedance compared to the impedance of the real traction battery, in order to produce realistic results. As using the real traction battery for the tests is not practicable because of the limited capacity a grid feed power source has to be used. In this work a passive impedance network, modelling the impedance of traction batteries is developed. Therefore, in a first step the impedance of a 360V hybrid battery pack is measured. Based on these measurements an equivalent circuit representing the battery impedance with its characteristic values and resonances is presented. Using this equivalent circuit the passive impedance network is designed for EMI testing of the HV traction system components. In the last step, this passive network is verified using traction system components integrated in a Hardware in the Loop setup on an electric vehicle traction system.