An ultra-fast charging architecture based on modular multilevel converters integrated with energy storage buffers

The paper presents power converter architectures for ultra-fast charging of road electric vehicles with the integration of distributed energy storage systems, which work as energy buffer between the grid and the electric vehicle in recharge. The study is introduced by an overview of the main issues related to the charging infrastructures in terms of electric vehicles charging times and their impact on the main grid. The paper continues with an analysis of ultra-fast charging infrastructures with particular focus on applications based on three-phase low voltage AC grid. Then, the proper design of modular multilevel converter architectures is presented taking into account its integration with energy storage modules of different technology, in order to reduce power requirements from the grid during the ultra-fast recharging phase. Different control strategies was proposed and simulated in terms of power flux control, during the charging and the discharging phase of the energy buffers, and voltage balancing among the different energy storage modules on the grid side.