As electric vehicle (EV) use increases, there is an increased need for EV charging stations. Even though many EV drivers charge their cars at home, for longer trips and commercial vehicles home charging doesn’t meet the need. Public and private DC fast charging (DCFC) stations offer a better solution for commercial EVs and on-the-go charging.

There are three levels of EV charging ports. Level 1 ports support single phase 120 V AC, 12-15 A; have a charging load of 1.4 to 1.9 kW; and charge at a rate of 3.5 miles per hour. They are almost entirely used for home charging. They are too slow to be of practical use by larger private or public charging stations. Level 2 ports support single phase 206-240 V AC, 12-80 A; with a charging load of 2.5 to 19.2 kW and a charging time of 12-60 miles per hour. They are also commonly used at home and in some public or private charging stations, e.g., office building parking lots. Both Level 1 and Level 2 charging ports simply transfer AC voltage supplied by the electric utility to the EV. This voltage is converted in the EV to DC voltage, which is the energy stored in the EV car’s batteries.

DCFC stations, the third level, support 3-phase 208 to 480 V AC, greater than 100 Amps, a 50 to 350 kW charging load, and a charging time of greater than 200 miles per hour. DCFC ports perform the conversion of utility AC voltage to DC voltage before transferring the voltage to the EV. In order to do this, they need a bigger, more costly infrastructure than Level 1 or Level 2 charging stations. The equipment needed for Level 3 DCFC charging consists of overcurrent protection/sectionalizers that are connected to the utility wires, a step-down transformer to take the AC power from the utility feed to a lower value (1000 kVA), a load center for AC to DC conversion, and finally wiring to the DCFC charging ports (1500 kW). Sometimes a solar PV array may be used to supply part of the EV charging voltage. In this case, the solar array would be connected to a DC/DC converter and then to the load center. The array might also be connected to onsite energy storage via a DC/DC and ES charge control, to store excess energy generated by the PV system.