Abstract
The wireless power transfer (WPT) system via coupled magnetic resonance (CMR) is an efficient and practical power transmission technology that can realize medium- and long-distance power transmission. People’s requirements for the flexibility of charging equipment are becoming increasingly prominent. How to get rid of the “flitch plate type” wireless charging method and enhance the anti-offset performance is the main research direction. Directional characteristics of the system can affect the load receive power and system efficiency in practical applications. In this paper, the power and efficiency of the WPT system via CMR were analyzed according to the principle of near-field strong coupling at first. The expression of the mutual inductance between the transmitting and the receiving coils under angular offset was derived from the perspective of the mathematical model, and the influences of angular deviation were analyzed. Second, simulation models were established under different distance between coils, different coil types, and different coil radius ratios in symmetrical and asymmetrical systems. Afterwards, the directional law was obtained, providing reference for the optimal design of coupling coils. Finally, an experimental system was built, and directional characteristic experiments were carried out under different conditions. Experimental results were consistent with simulation results, which verified the theoretical analysis.
Highlights
Wireless power transmission (WPT), which is called contactless power transmission (CPT), is widely used in the fields of electric vehicles, mobile devices, etc., and has research values and practical significance for the development of electromagnetic theory [1,2,3,4,5,6]
Even if the system of wireless power transfer (WPT) with coupled magnetic resonance (CMR) has a certain degree of non-directionality, it can reduce the system’s requirements for directionality to a certain extent, but there is no definite standard for the non-directional range
The WPT system via CMR mainly includes an RF power source, an electromagnetic launch system, an electromagnetic receiving system, and load, as shown in Figure 1, where D is the distance between the center points of transmitting and receiving coils; k is the coupling factor between coils; and θ is the deviation angle of the receiving coil
Summary
Wireless power transmission (WPT), which is called contactless power transmission (CPT), is widely used in the fields of electric vehicles, mobile devices, etc., and has research values and practical significance for the development of electromagnetic theory [1,2,3,4,5,6]. Wireless power transmission technology has changed the situation that the consumer electronics field has always relied on charging wires and plugs. In [18,19], the parameters of coupling coils were optimized to improve the system efficiency These researches were mainly aimed at the transmitting and receiving coils that were parallel to each other, while the directivity of the corresponding coils did not change and the parameters were the same. It is required that the directivity of coupling coils should not change, especially under many practical application scenarios such as household appliances, medical implantation and electric vehicle charging. The article [23] uses Helmholtz coils to design a three-dimensional transmitting mechanism and realizes omnidirectional wireless charging, but the directional attenuation range is not regulated. An experimental platform was built to verify simulation results
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