High Efficiency operation of Inductive Battery Charging System by the Coordinated Voltage-Frequency Control during Large Variations in Coupling Conditions

This paper presents a coordinated voltage-frequency control method for maintaining high efficiency of inductive battery charging systems during large variations in coupling conditions. The method automatically switches between voltage control and sub-resonant frequency control according to the change of the coupling coefficient and power reference without depending on any estimation of the coupling conditions. Moreover, the coordinated voltage-frequency control allows for designing the system to maintain the low component stress and high efficiency in the whole operating region. A comparison with the pure voltage control and pure frequency control is presented to highlight the advantages of the coordinated voltage-frequency control in terms of maintaining a higher efficiency in a wide range of coupling coefficients. Effectiveness and feasibility of the proposed method are validated by simulation and experimental measurements from a small-scale laboratory prototype.