Partial Power Processing LLC Converter for Electric Vehicle Charging

With the popularization of electric vehicles, the demand for electric vehicle charging piles is increasing. Currently, AC charging is mainly used in homes or offices, however, its main drawback is the long charging time, which usually takes 4~20 h, which is not conducive to the promotion and development of electric vehicles. In order to solve this problem, a charging pile design scheme based on LLC resonant converter is proposed. The topology adopts a partial power processing structure, which allows the charging pile to transmit most of the power directly to the electric vehicle, while only a small portion of the power is processed by the converter and then transmitted to the electric vehicle. This design effectively reduces the power loss in the intermediate links and improves the charging efficiency. The connection method of partial power processing is analysed and selected, and the parameters of the topology and the control strategy are discussed. Finally, the feasibility of the control strategy is verified by Matlab/Simulink simulation, and the effectiveness of the proposed topology is proved by building an equally scaled-down hardware experimental platform for experiments, which verifies that the converter still outputs stable power when the power passing through the full-bridge LLC resonant converter is only a part of the rated power. The partial power treated LLC and the full power treated LLC are then compared under the same operating conditions, proving that the proposed topology achieves efficiency improvement over the full voltage gain range. The partial power converter handles only 35% power with 0.8% efficiency improvement at full load and 1.5% efficiency improvement at 50% load.