A Temperature Prediction Method for DC-Link Film Capacitor in Electric Vehicle

Abstract

In EV/HEV application, the maximum internal temperature allowed for film capacitor should be less than 105 ℃, which leaves especial limited temperature margin as the capacitor works in high ambient temperature of 85 ℃. However, temperature rising of capacitor is strongly related to the load condition. And it is difficult to define the temperature allowance of capacitor accurately in the early design. For this purpose, a consolidated electrothermal simulation method based Foster thermal network model is presented in this paper to predict the transient temperature inside the capacitor. To set up a complete simulation model, the parameters of five-order Foster resistor-capacitor thermal network model are extracted by the method of capacitor temperature rise experiment. The temperature rising of film capacitor in the conditions of NEDC (New European Driving Cycle) & USA highway driving cycle is calculated by the complete simulation model. Simulation results show that a good correspondence is presented between capacitor temperature rising curve vs ripple current under driving cycle, and the maximum temperature rise can be clearly assessed by this temperature prediction method.

Keywords

• foster resistor-capacitor thermal network model
• temperature prediction
• film capacitor
• electric vehicle