Primary-side efficiency control of wireless power transfer systems based on secondary-side power control with half active rectifier

Applying wireless power transfer (WPT) to transportation applications is one of the best solutions to overcome the drawbacks of electric vehicles (EVs) caused by their energy storage systems. Although dynamic charging of EVs can extend their driving distance, control techniques need to be developed to maintain maximum transmitting efficiency and to ensure a stable supply of energy, because a dynamic WPT system has to deal with parameter variations such as distance change, load change, and so on. Since a control strategy based on signal communication between the primary side and secondary side reduces the reliability of the system, this paper proposes a primary-side efficiency control method based on the change in primary current, resulting from the power control with half active rectifier on the secondary side. The reference value of the primary voltage for maximizing the transmitting efficiency is calculated based on the primary-side information. Simulations and experiments demonstrated that the proposed method could achieve not only maximum transmitting efficiency but also the desired load power.