A Fast Thermal Network Model for Film Capacitors in Power Electronic Applications Facilitating the Lifespan Assessment

Film capacitors play a critical role in filtering ripple current and stabilizing DC-link voltage in power electronic applications. As the degradation behavior of metallized film capacitors is highly temperature-dependent, accurate estimation of hotspot temperature is critical. However, conventional estimation methods such as finite element analysis (FEA) and simplified lumped thermal network (LTN) models have limitations in computational efficiency and accuracy, respectively. In this paper, traditional thermal modeling approaches are first reviewed in terms of their accuracy and computational efficiency, with temperature rise experiments conducted on a customized capacitor to support this analysis. Second, variable-order Foster thermal network models are adopted to achieve accurate and efficient estimation of the capacitor’s hotspot temperature during operation. Lastly, the impact of temperature estimation errors on the prediction of capacitor lifespan is investigated. The finding can provide insights into the thermal behavior of film capacitors in power electronic systems and offer guidance for their predictive maintenance.