Directional Characteristics of Wireless Power Transfer via Coupled Magnetic Resonance

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.