Design of a Level-3 DC Fast Charging Station for EVs Using a Dual Active Bridge DC-DC Converter

This research paper discusses a bidirectional DC-DC fast charger (or level-3 charging system) to obtain a high-power level. However, two types of EV charging systems are available, i.e., an on-board charging system and an off-board charging system. For dc fast charging, it is essential to use the off-board charger to reduce the volume and weight of EVs significantly. This charger charges the EV battery using a Dual Active Bridge (DAB) topology for the DC-DC converter, which is better for bidirectional power flow, power density, and efficiency and has less passive component count than resonant circuits using inductors and capacitors. Furthermore, zero-voltage switching (ZVS) from light to medium load is challenging using Single-Phase Shift (SPS) control. This improves system reliability and efficiency by decreasing switch-bridge crosstalk caused by hard switching-ON. Optimizing phase shift reduces switch voltage stress. Double Phase Shift (DPS) and Triple Phase Shift (TPS) control may work but have disadvantages, like larger switching-OFF currents. Moreover, SPS is discussed with CCCV charging. The design for DAB includes two different voltage and current control loops using PI controllers to control the power flow between the two H-bridges of the DAB converter to charge the battery. All the results are presented, obtained from simulations done on MATLAB.