Dual independent control for inductive wireless power transfer

The power transfer and efficiency of a magnetically coupled wireless power transfer system depends mainly on the frequency of operation, the distance between the primary and secondary coils, and the load condition (i.e. battery state-of-charge). Different techniques have been proposed to optimize the efficiency of these WPT systems. Most of the techniques require additional hardware to communicate data between the transmitting and the receiving coils. In this paper, the primary (transmitter) of the proposed system was controlled by tuning a variable capacitor. The tuning was performed for the dynamic changes in the coupling coefficient, which maintains a minimum phase angle between the primary voltage and current. For the receiver (secondary), load regulation was achieved by implementing a dc-dc converter with PWM control. Since both the control strategies are implemented independently, separate communication hardware is not required. The simulation of the proposed scheme was performed using MATLAB/Simulink. The simulated results of the proposed dual control system yielded a power transfer efficiency of ~ 85% in spite of variations in the load and the coupling coefficient.