Voltage control strategies of smart transformer considering DC capacitor lifetime

Distribution grids unbalance challenges the DC-link of the Smart Transformer leading to higher ripples and then the lifetime of the DC aluminium electrolytic capacitors (AEC) is reduced. Additionally, dead time and nonlinearity characteristic of IGBT also may introduce ripple current in DC link, potentially decreasing the lifetime of AEC. Based on physical characteristic of AEC, the lifetime estimation of AEC is investigated considering aforementioned impacts. To suppress these impacts, an improved voltage control strategy that can reduce AEC current ripple and then preserve AEC lifetime is proposed. The theoretical analysis has been demonstrated by the simulation results