Wireless Power Transfer Using Selected Harmonic Resonance Mode

The smaller size of the coils is one of the major concerns in designing the wireless power transfer (WPT) systems. In the optimum design of a WPT system, imposing constraints on the physical dimensions of the coils results in more copper usage for certain efficiency. Increasing the operating switching frequency, however, mitigates the weight and copper usage, but it leads to more switching, skin, and proximity effect losses, which decrease the overall efficiency. In this paper, a novel approach using selected harmonic current of switching frequency has been introduced to design optimum coils. In this method, a high resonant frequency converter excited by a lower switching frequency has been developed. The proposed approach leads to lighter and smaller coils with higher efficiency. The proposed approach was verified using simulation and experimental results for a 3500-W WPT system to transfer power over a distance of 0.15 m at 425-KHz resonant frequency while the switching frequency was only 85 KHz.