Uncertainty analysis of capacitor reliability prediction due to uneven thermal loading in photovoltaic applications

Because of the high cost of failure, the reliability performance of capacitors is becoming a more and more stringent factor in many energy conversion applications. Since temperature is one of the main stressors that leads to the wear-out of capacitors, it is important to understand the uncertainties introduced by the capacitor thermal modelling within its reliability prediction process. Thus, in this paper, the uncertainties introduced by uneven thermal loading, and their impact on the reliability of a photovoltaic application DC-bank are investigated. Based on a generic model-based reliability assessment procedure, a reliability evaluation tool is initially developed and used in order to quantitatively analyze the impact of these uncertainties. The lifetime evaluation of the individual capacitors/DC-bank is estimated and afterwards benchmarked under even/uneven thermal loading conditions. The outcomes of the uncertainty analysis indicate that the uneven thermal distribution among DC-link capacitors can have a significant impact on both component and system-level reliability performance.