Efficient and Grid Friendly DC Charging Station

This thesis outlines an accurate design procedure for the CLLC converter in the DC charging stations, which is suitable for First-Harmonic-Approximation (FHA) assumption. It works closely to the resonant frequency in a narrow switching frequency interval above it in both operating conditions, with ZVS and a reasonable operating voltage range for a DC bus in the DC microgrid. To enable G2V operation, a closed-loop voltage controller and a closed-loop current controller to achieve constant voltage (CV) charging and constant current (CC) are implemented. Instead, the discharging mode (V2G) operates with soft-start under constant voltage (CV) operation, and a voltage closed loop controller is implemented. Both control strategies have been validated through simulations, demonstrating soft switching for both full-bridges. Also, in this thesis, an algorithm that aims to minimize the losses incurred from injecting energy from the fleet of EVs in the charging station into the grid is proposed. The algorithm updates the power to be drawn from each EV based on the arrival state of charge (SOC), recalculating it every time there is an EV arrival or departure from the charging station.