Application of Temperature Prediction Method for DC Bus Film Capacitance in Electric Vehicles

Film capacitor has been widely used by inverter manufacturer for the application of electric vehicle. The internal core temperature is a paramount concern for DC-Link film capacitor package, influencing the package’s thermal, mechanical, and reliability performance. In EV/HEV application, the maximum temperature allowed for internal film should be below 105 ℃, which leaves limited temperature margin especially under high ambient temperature 85 ℃. An accurate temperature prediction is needed to provide guidance in terms of design and operation. However, DC-Link capacitor’s core temperature is strongly related to the load condition. Thus, a complete analysis model employing consolidated thermoelectric method is presented in this paper to predict the transient temperature inside the capacitor. To set up a complete simulation model, thermal model of capacitor with 5-order Foster resistor-capacitor (RC) thermal network is extracted from real experiment results. The film capacitance temperature rise of NEDC & highway driving cycle is calculated by the complete simulation model. This method provides useful guidance on capacitor selection in the stage of main inverter design in EV application.