An automatic frequency-tuned wireless charging system is proposed and successfully demonstrated to enhance the power transfer efficiency for different vertical spacings between the charging coils in the presence of proximal metallic objects. The frequency characteristics of wireless power transfer efficiency have been investigated through simulation and experimental measurements. It has been observed that the resonance-based wireless charging system is very sensitive to the imperfect positioning of charging coils and nearby metallic objects. At the operating frequency, the power transfer efficiency of the charging system reduces drastically. However, by allowing the transmitting frequency to adapt to the position of the coils and metallic objects through the automatic frequency-tuned system, the deteriorated power transfer efficiency is further improved.

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The design guidelines have been proposed for achieving efficient wireless Electric Vehicle (EV) charging system under non-ideal practical scenarios. The effects of operating parameters have been investigated by addressing the fundamental hurdle to the widespread usage of magnetic resonance coupling (MRC) based wireless EV charging system. From both experimental and simulated results, it has been perceived that the power transfer efficiency (PTE) depreciates rapidly as the charging condition deviates from the ideal one. It is observed that PTE can be managed to enhance from the deteriorated value to an acceptable level through proper consideration of separation air gap of the charging coils, frequency of operation with acceptable horizontal offsets, suitable coil models, position of metallic object, and coil properties. To maintain the maximum PTE even under non-ideal scenario, an automated frequency tuning method has also been delineated. The corroborated experimental and simulated results can provide a complete strategic plan in the design of an efficient practical wireless power transfer system to be utilized for EV charging system.

In order to power or charge electronic devices wirelessly, a bi-directional wireless power transfer method has been proposed and experimentally investigated. In the proposed design, two receiving coils are used on both sides of a transmitting coil along its central axis to receive the power wirelessly from the generated magnetic fields through strongly coupled magnetic resonance. It has been observed experimentally that the maximum power transfer occurs at the operating resonant frequency for optimum electric load connected across the receiving coils on both side. The optimum wireless power transfer efficiency is 88% for the bi-directional power transfer technique compared 84% in the one side receiver system. By adopting the developed bi-directional power transfer method, two electronic devices can be powered up or charged simultaneously instead of a single device through usual one side receiver system without affecting the optimum power transfer efficiency.

Abstract-A typical magnetic resonance coupling based wireless Electric Vehicle (EV) charging system consists of a transmitting coil at the charging station and a receiving coil in the vehicle. In order to maintain good energy transfer efficiency of the wireless charging system, the effect of the proximal metallic object in the vicinity of the receiving coil has been investigated. Both from the simulation and experimental measurement, it has been observed that the resonance based wireless energy transfer system is very sensitive to the nearby metallic objects, leading to significant deterioration in energy transfer efficiency. This effect on the energy transfer efficiency is also seen to be different for different physical spacing between the transmitting and receiving coils. It is also found that the operating resonant frequency for optimum energy transfer efficiency changes with the metallic object in close proximity to the receiving coil. The simulated results well agree with the experimental results. The analysis will provide future guidelines for designing an efficient resonance coupling based wireless charging system for EVs even in the presence of metallic objects.