Investigation of thermal effects and lifetime estimation of electrolytic double layer capacitors during repeated charge and discharge cycles in dedicated application

Abstract

The article is firstly focused on thermal analysis of electrolytic double layer capacitor (EDLC) operated at repeated cycles of charging and discharging. This process is mostly applied at switched mode power supplies (SMPS), where electrolytic capacitor within given period of operation acts as energy storage element (discharge period). Charging and discharging process of EDLC may cause additional heating, which consequently influences capacitor’s lifetime. This parameter (lifetime) is nowadays very important parameter of EDLC, because operational life of the most of complex power electronic systems is directly influenced by its most critical components, i.e., by electrolytic capacitors. In this paper, the theory necessary for capacitor analysis and analysis of heat transfer is presented. The particular aluminum electrolytic capacitor Nichicon is examined in the paper. The implementation of real model into COMSOL Multiphysics and consequent simulation settings are being described too. Based on the main parameters of target application, the simulation analysis is processed. These results are consequently verified by experimental measurements on a given sample of EDLC. Deviations between measured and simulated data are identified, and optimization steps for better accuracy are also given. Finally, the factors influencing the lifetime of electrolytic capacitors together with calculation of capacitor’s lifetime in power application are described. During lifetime estimation, heat transfer simulation modeling of capacitor is utilized. Presented approach offers acceleration of necessary variables identification, which are hardly to be identified with the use of measurements, e.g., capacitor’s core temperature. Thus, more accurate results regarding lifetime estimation can be achieved.