Although the wireless power transfer (WPT) system for electric vehicles (EVs) provides numerous advantages, there is still a low coupling coefficient and the misalignment between the primary coil and the secondary coil needs to be solved. In this paper, the transmission efficiency and transmitted power were calculated based on Series-Series (SS) compensation topology. The coupling coefficient is related to the coil parameters and misalignments. A simulation study was carried out to explore the variation in the coupling coefficient for different coil configurations under different air gaps and coil misalignments. Moreover, the influence of the internal parameters of the square coil on the coupling coefficient was further studied. Finally, this paper discusses the influence of ferrite cores with a square coil on the coupling coefficient. The results of this paper show that designing the optimal internal parameters of the square coil and the ferrite core can increase the coupling coefficient between the coils, which can also provide guidelines for the design and optimization of the magnetic coupling coils for a wireless charging system for electric vehicles.

Recently, wireless power transfer (WPT) systems have been used as battery chargers for electric vehicles. In a WPT system, the design approach and control strategy have a significant impact on the performance of the wireless power transfer systems in electric vehicle powertrains in terms of efficiency, charging power, charging modes, charging time, etc. A characteristic of different topologies appears depending on whether the compensation capacitor is connected in series or parallel with coils. Therefore, it is necessary to select a suitable compensation topology depending on different applications. Thus, this paper proposes a new design methodology and control system for bidirectional 3.7 kW and 7.7 kW WPTs in light-duty electric vehicles (EVs) operating at both 40 kHz and 85 kHz resonance frequencies. In this paper, the series-series (SS) WPT compensation topology is optimally designed and controlled for grid-to-vehicle (G2V) mode using MATLAB/Simulink. A simulation study is performed for a selected WPT design for G2V mode to ensure its functionality and performance at different power levels. Moreover, the magnetic design of the coils and its parameters are verified by using COMSOL. Finally, experimental results are validated for the WPT system.

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