Toward Extreme Fast Charging: Challenges and Opportunities in Directly Connecting to Medium-Voltage Line

In this article, we present the current state-of-the-art fast-charging technologies. We discuss the state-of-the art-fast chargers, their design, and their main characteristics. Additionally, we detail how these chargers can be combined to form fast-charging stations that mimic the functionality of a gasoline refueling station. Various power delivery concepts for these charging stations are described, and we discuss the benefits and shortcomings of the current and proposed approaches. Finally, we present a novel approach in which the charging station directly connects to the medium-voltage (MV) line, thus eliminating a number of power electronics conversion stages and the low-frequency step-down transformer. We outline significant benefits of this technology when considering extreme fast-charging rates, and we identify the key technology gaps in making this technology more widely accepted.