Analytical Design of an S/SP Compensated IPT System to Minimize Output Voltage Fluctuation Under Predetermined Coupling Coefficient Range

Compensation topology plays a vital role in inductive power transfer (IPT) system since it can improve power transfer capability and efficiency. S/SP (primary series, secondary series-parallel) compensation topology is widely employed in IPT system due to its strong tolerance to misalignment. The three compensation capacitances in S/SP topology should be tuned at the optimal coupling coefficient in order to achieve minimum output voltage fluctuation when the coupling coefficient varies from minimum to maximum. This paper proposes an analytical method to derive the optimal coupling coefficient. Detailed deduction procedure is given. The correctness of the theoretical analysis is validated by both simulation and experiment. The output voltage fluctuation are solely 1.47% and 2.83% in the simulation and experiment respectively when the coupling coefficient increases by 34.55%, from 0.1288 to 0.1733. A 200-watt prototype is fabricated, the end-to-end (from DC input to DC output) efficiency of which is practically measured as 94.1%.