In the provided lifetime model for SDs and Caps, the epistemic uncertainties, such as model constants, must be determined by lifetime tests. The accurate reliability model requires more tests with an acceptable confidence level. Moreover, the aleatory uncertainties, such as temperature, come from manufacturing variations and applied mission profile. These uncertainties must be accurately defined based on the data provided by manufacturers and precise electrothermal mapping of mission profile. After recognizing uncertainties, the density function of stress and resistance can be identified and consequently, the component reliability can be obtained by using (13).The failure probability described by (13) can be obtained by MCS [17], [18]. In practice, for large-scale power electronic-based power systems, MCS is not feasible due to the calculation burden. Hence, a first-order reliability method (FORM) [26] is adopted in order to find the component's failure probability.The component's resistance R in (14) and (15) can generally be represented as