High reliability capacitor bank design for modular multilevel converter in MV applications

In this paper, reliability evaluation of the capacitor bank for the Modular Multilevel Converter (MMC) based on two common types of the DC-Link capacitors i.e. Aluminum Electrolytic and Film capacitors is investigated. Because of the high current ratio through the capacitor in the MMC, it is shown that in the Film capacitor because of the low ESR, the power loss and the core temperature rising will be lower than the Aluminum Electrolytic Capacitors. Based on three-sample design using ALE and Film capacitors, the reliability function over time is calculated for each case study. The result shows that the Film capacitor bank design is the high reliability and the long life solution in each design. In order to improve life time and reliability of the Aluminum Electrolytic Capacitor, adding Film Capacitor to ALE capacitor bank is presented in this paper.