A Novel Multiscale Perspective Based Hotspot Temperature Assessment Method for Film Capacitor in DC-Link Applications

DC-Link has been widely used in power electronics applications like photovoltaic systems, electric vehicles, aircraft, and LED drivers. Film capacitors often present a thermal management bottleneck in DC-Link. A significant number of novel film materials have been designed to enhance the high-temperature performance of film capacitors. However, the cost of fabricating these materials into capacitor cores and conducting tests is exceedingly high. Therefore, proposing an efficient modeling method to evaluate the hotspot temperature of film capacitors becomes a burning issue. This article proposes a multi-scale finite element modeling (FEM) method to determine the equivalent characteristics of metallized films composed of various materials, as well as the temperature rise in film capacitor units. Initially, equivalent electromagnetic and thermal micro-scale models of multilayer metallized films are established to analyze the principle of film capacitors and obtain equivalent parameters of metallized polymer film. Subsequently, the temperature rise of the capacitor unit is simulated using the macro-scale model, with validation provided by temperature rise tests and data from product manuals. The proposed approach is straightforward, making it applicable to capacitors with various polymer materials and different shapes, and the error in hotspot temperatures obtained through this method is 2.20%.