In near‐field energy transmission, wireless power transfer based on magnetic coupling resonance is preferred. For efficient power transfer, the quality factor of magnetic coupling resonance wireless power transfer (MCR‐WPT) system should be kept at a high value, which makes the system sensitive to frequency detuning. Different from conventional approaches dealing with the problem in linear MCR‐WPT system, this paper proposes a novel MCR‐WPT system, which is based on Van der Pol nonlinear resonant circuit to address the problem of frequency detuning. A nonlinear resistor is introduced, and the nonlinear Van der Pol MCR‐WPT system is established. Based on the mathematical model and the theoretical analysis, it is found that the frequency band is broadened. To validate the performance of the proposed system, extensive simulation and experimental work are conducted. Unlike the traditional linear system, which only peaks at the resonant frequency, the results show that the output of the proposed system is still high within a certain frequency band when the operating frequency deviates from the original resonant frequency. The impact of frequency detuning caused by variation of capacitance is also studied. It can be concluded that the proposed MCR‐WPT system is effective in coping with the frequency detuning.
Summary
In this paper, an efficient wireless power transmission (WPT) system that incorporates a new negative permeability metamaterial is presented. The operating principle of the metamaterial with negative permeability is first analyzed. To improve transmission efficiency of the WPT system at the operating frequency of 13.56 MHz, a new metamaterial with three open rings is designed. By respectively placing a single metamaterial slab and double metamaterial slabs at different positions between transmitting coil and receiving coil, the performance of the proposed WPT system is evaluated by simulation work. The corresponding magnetic field distribution is also analyzed. Besides, comparison is made with the conventional WPT system without metamaterial. It is found that transmission efficiency of the proposed WPT system is obviously improved when incorporating the metamaterial since the designed metamaterial effectively focuses magnetic field towards the receiving coil. Comparing with the conventional system, the results also show that the proposed WPT system is more robust to lateral and angular misalignment of the receiving coil. With the designed metamaterial, it is found that the proposed system with double metamaterial slabs performs better than that with a single metamaterial slab.
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