Modular Multilevel Converters for Fast Charging Stations of Electric Vehicles: An Overview

This paper reviews the different configurations of Modular Multilevel Converters (MMCs) used in Fast Charging Stations (FCSs) and Extreme Fast Charging Stations (XFCs) of Electric Vehicles (EVs), It enables a solid reference for charging stations operating at the megawatt's level and employing novel topologies to interface with the grid. First, the paper delivers a general overview on FCSs and XFCs along with their requirements and challenges. Then, the paper describes in detail the different configurations of MMC structure and highlights the importance of using MMC in terms of reducing the overall size of the charging station, and in reducing the impact of the massive integration of FCSs and XFCs on the grid. A comparative study is presented to focus on various configurations of MMC-based FCSs and XFCs and compares them in a table in terms of structure components, target objectives within the structure, and outcomes benefits of each type. Common benefit associated with several proposed MMC configurations is interfacing directly with the medium voltage grid, thus the bulky, costly, and heavy line frequency transformer is removed. Additional benefits include limiting the grid-side filter due to the high-quality waveforms of MMC, in addition to the easy integration of renewable energy sources and energy storage systems which helps in managing the impact of the charging station on the grid in terms of power requirement.