A Design Method for Large-Coupling-Range Series-Series Compensated WPT Systems under Practical Constraints

The series-series (SS) compensation has been widely adopted by inductively-coupled wireless power transfer (WPT) systems. However, the power transfer capability of an SS WPT system depends on the coupling between the windings. When it operates at the resonant frequency, the SS WPT system may fail to output the required power at a strong coupling position. In practical applications, it is expected that the coupling will change in a large range due to air gap changes and misalignments. Usually, the power transfer capability can be improved by shifting the operating frequency to the splitting frequencies in the strong-coupling region. However, a few practical constraints such as input voltage limit, VA rating limit (or input current limit), operating frequency range, expected rated-output-power coupling range, and soft switching condition, will significantly complicate the design processes of such a system with a large coupling range. This paper proposes a two-end verification method for designing large-coupling-range SS WPT systems under the above practical constraints. Simulation and experimental results are provided to verify the design method.