An Impedance Self-Adjustment Method via Variable Inductors in Integrated LCC–LCC-Based IPT System for Efficiency Improvement Versus Air-Gap Variation

In an inductive power transfer (IPT) system, due to the presence of ferrite cores, changes in the air gap can alter the coil parameters (self-inductances and mutual inductance), leading to system detuning, resulting in efficiency degradation. To address this problem, an impedance self-adjustment method based on an integrated LCC-LCC topology with two variable inductors is proposed for IPT systems to enhance efficiency. Combined with the second-generation non-dominated sorting genetic algorithm (NSGA-II) for system parameter design, the proposed method can mitigate secondary-side detuning and offer variable input impedance to realize wide-range zero-voltage switching of the inverter with phase-shifting (PS) control. The proposed method does not need additional components or complex controls. Experimental results show that with the air gap variation from 30 mm to 60 mm (the self-inductance variation is 17.47%, the mutual inductance variation is 80.91%) and the load variation of 50%, an accurate output is achieved with PS control, and the system efficiency ranges from 92.6% to 94.23%. Compared with the traditional method, the maximum efficiency improvement is up to 16.92%.