Modeling and Control Of Two Stages On-Board Charger For Electric Vehicle Applications

The on-board Charger (OBC) is a great addition for modern electric vehicles to set them free of the regular charging stations. Therefore, the OBC must be designed for high efficiency, low-cost, high-power density, and low weight to be suitable for electric vehicle applications. First, this paper investigates the OBC topologies and their steady state operation. Then, it introduces the modeling and control design of the OBC. The OBC topology consists of two stages: a power factor correction stage (PFC) and an isolated DC-DC converter (LLC) stage. This paper introduces the modeling and the control scheme of the PFC stage. Then, the system identification is used to obtain the LLC transfer function which is required for the controller’s design. In addition, two control strategies are studied for the OBC. The first strategy is a constant DC-link voltage (VDC) during the charging cycle. The second strategy is a variable VDC with the battery voltage variation during the charging cycle. Finally, a simulation study of the comparison in terms of efficiency has been made between the two strategies. The simulation results show a considerable improvement in the efficiency of the variable VDC control method compared to the constant VDC control method.