2014). Electric vehicle wireless charging technology: a state-of-the-art review of magnetic coupling systems. Wireless Power Transfer, 1, pp 87-96

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Abstract:The efficiency of wireless power transfer is sensitive to the horizontal and vertical distances between the transmitter and receiver coils due to the magnetic coupling change. To address the output voltage variation and efficiency drop caused by misalignment, a uniform voltage gain frequency control is implemented to improve the power delivery and efficiency of wireless power transfer under misalignment. The frequency is tuned according to the amplitude and phase-frequency characteristics of coupling variations in order to maintain a uniform output voltage in the receiver coil. Experimental comparison of three control methods, including fixed frequency control, resonant frequency control, and the proposed uniform gain control was conducted and demonstrated that the uniform voltage gain control is the most robust method for managing misalignment in wireless charging applications.

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Wireless power transfer is a promising method to address the concerns over charging an electric vehicle. Since wireless charging stations operate without large cables or above-ground stations, they can be conveniently installed in public locations without the risk of vandalism or weather-inflicted damage, improving the lifespan of the electric vehicle charging station. In order for wireless charging stations to become widespread, possible health effects regarding exposure to the strong electromagnetic fields present during wireless power transfer must be investigated. This work examines, first, the potential human safety hazards, second, the electronic device interference, and, third, the thermal heating effects of wireless charging systems. A 3.3 kW wireless power transfer prototype was built in order to examine these effects. Changes in the wireless power transfer efficiency due to the coil misalignment were also investigated using an automated three-axis platform. Design considerations for electric vehicle wireless charging systems and safety recommendations are presented.