A Novel Lifetime Estimation Method and Structural Optimization Design for Film Capacitors in EVs Considering Material Aging and Power Losses

Film capacitors are widely used in electric vehicles (EVs) controllers to reduce the adverse effects of ripple current on batteries and converters. But the upper limit of the working temperature for film capacitors is relatively low. High ambient temperatures in EVs can lead to premature failure of film capacitors, thereby impacting the reliability of the controllers. Therefore, proposing a corresponding capacitor lifetime prediction method is a burning issue. This paper analyzes the accumulation of damage and degradation processes in film capacitors and proposes a method to predict their lifetime, which accounts for changes in ESR, thermal conductivity, and internal losses. An analysis on a
$440\mu $
F film capacitor bank is performed using this method as an example. In addition, the effectiveness of optimizing the capacitor structure to extend capacitor lifetime is analyzed based on finite element modeling (FEM), and the Monte Carlo method is employed to consider the influence of manufacturing tolerances on the reliability of film capacitors. The analysis results indicate that, compared to the original capacitor, the B10 life of the optimized capacitor can be extended by 54.11%.