Electrical architecture for ultrafast charging station

Abstract

EVs will play an important role in transport, climate change and electrification. However, there is a consensus that one of the main obstacles to full market penetration of EVs is the so-called range anxiety (fear of not having enough charge in the vehicle). Electric vehicle charging infrastructures have two opposing approaches to their use. For urban routes, where distances travelled, and EV usage times are low, on-board alternative current (AC) chargers (Level 1 and 2) can meet the charging requirements in most situations. The solution is a gradual increase of the existing electrical infrastructure and charging points, together with the integration of new energy sources to cope with the new loads. On the other hand, on highway routes, EVs require large amount of energy in a short time in order to provide a continuous trip. Nowadays, electric charging stations provide fast charging points for vehicles by connecting external chargers that supply direct current (DC) directly to the battery bank (Level 3) and these can take up to 30 minutes. However, a time of more than 10 minutes is considered to be a very long time in contrast to the time required to fill the tank of internal combustion vehicles. In this context, ultrafast charging is defined with charging time to 10 minutes or less. This report proposes the electrical architecture of an ultrafast charging station for electric vehicles (EVs), which is based on a hybrid energy distribution system made up of an AC bus and two DC buses, each one of different voltage. The proposal is the result of a statistical analysis based on Monte Carlo simulations, which uses real traffic data and stochastic models to estimate the number of vehicles, the energy required and the time to charge each EV that would access the station. Once the architecture is established, the operating modes of the station are defined, where a storage system is contemplated to provide service reliability, and which is sized following load levelling and load shifting strategies with static and proposed dynamic charge counting methods. As a result of the report, an event simulation incorporating the operating modes and a 500 kWh storage system to serve 100 EVs has been performed, in which case 99% service was achieved even under shutoff of the grid.