Medium Voltage Dual Active Bridge Using 3.3 kV SiC MOSFETs for EV Charging Application
DC fast-charging stations are on the rise as the number of electric vehicles (EVs) on the road is increasing significantly. To reduce the charging time and extend the driving range of EVs, the development of high-power, off-board charging stations is necessary. The conventional architecture of a dc fast-charger incorporates either a local or a centralized front-end converter that interfaces the medium voltage (MV) grid via a low voltage (LV) line frequency transformer. However, such architecture is limited due to its large operational and installation costs.
In this work, a different power delivery solution with an iso- lated dual-active bridge (DAB) converter is proposed for a medium- voltage connected EV charging architecture, as shown in Fig. 1. A matrix-type, modular system architecture is used to connect multiple cells in series in order to interface the medium-voltage grid. Each cell consists of a triple-active bridge, allowing multiple ports for a single charging station for more EV charging capability. This struc- ture can eliminate the line frequency service transformers, which are bulky and costly, and thus, reducing the size and installation costs of EV charging stations. Fig. 2 shows a picture of the triple-active bridge prototype with 2.5 kV input and dual 800 V outputs via high- frequency, medium-voltage transformer.