I. Introduction
In the railway traction system, due to strict safety requirements, passive components usually require a high lifetime of more than decades [1]. In recent years, studies of the reliability evaluation mainly focus on the analysis of fault data statistics in the railway traction system, including the establishment of databases, the modeling of reliability index, the fuzzy synthetic evaluation, and the analysis of fault tree [2]–[5]. However, because the sample size of the fault data is uncertain, the existing methods have certain randomness and limitation and rarely involve the reliability evaluation of the capacitor in the traction system. In the railway traction drive system, the DC-link capacitor, as the role of realizing energy storage and filtering, is located between the rectifier and the inverter [6]. More importantly, it is highly related to system safety and reliability. Therefore, the reliability evaluation of the DC-link capacitor banks is essential for the operation and maintenance of the railway traction system [7].