Research On Dual Band Magnetic Coupling Resonance Wireless Power Transmission System

Wireless power transmission technology has received more and more attention because of its advantages of safe operation,convenient and flexible operation,low maintenance cost and good user experience.The use of wireless charging technology to supply power to electric vehicles,robots,drones and other electric equipment has become a popular trend.The magnetic coupling resonance wireless power transmission technology has the advantages of high transmission efficiency in the middle distance range,high power transmission,and becomes a hot direction in the field of wireless power transmission.The multi-load wireless power transmission technology can simultaneously supply power to multiple loads,and has the advantages of high flexibility,wide applicability,space saving,and easy realization of equipment weight reduction.In this paper,a dual band magnetic coupling resonance wireless power transmission system is designed,and an overlapping double circular coil structure is designed to realize the function of simultaneously supplying power to two loads.The main system resonant frequency uses 85kHz to achieve power transmission;the auxiliary system resonant frequency uses 30kHz,which can be used as an auxiliary power supply or signal transmission system.In this paper,the magnetic circuit model of the double circular coil structure is analyzed.And the relationship expression between the magnetic coupling coefficient of the coils and the magnetic resistances is derived,which provides a theoretical basis for the layout and parameters design of the coils.The basic theory of magnetic coupling resonance wireless power transmission system is analyzed.Based on this,the circuit model and mathematical model of the dual-band magnetic coupling resonance wireless power transmission system are established.There are couplings between the coils of the overlapping double circular coils,which produces interference with each other.This paper analyzes the influence of inductances and resonant frequencies on the system,and discusses the method of eliminating the interference by adding filter inductances in the system branch or rationally selecting the resonant frequencies.The influence of coil parameters variation on the magnetic coupling coefficient is analyzed by ANSYS Maxwell simulation software,and appropriate coil parameters are selected based on the analysis.The Simulink software is used to simulate the dual band magnetic coupling resonance wireless power transmission system.The relationship between the harmonic content of each branch of the system and the variation of the inductances and resonant frequencies is analyzed.Increasing the filter inductances or the difference of two resonant frequencies can effectively suppress the interference between the coils due to cross coupling.In order to simplify the system and achieve light weight,this paper uses multi-frequency pulse width modulation technology to enable a single inverter to output high frequency AC voltages of different frequencies.The theory of multi-frequency pulse width modulation technology is analyzed,and the method of obtaining harmonics of specific frequency and amplitude is discussed.Simulink software is used to realize the simultaneous output of voltages of 30kHz and 90kHz by a single inverter.The multi-frequency pulse width modulation technology is applied to the dual band magnetic coupling resonance wireless power transmission system,so that a single full-bridge inverter drives the dual-band coil,realizes the dual load power supply,and the harmonic contents of the system coil currents meet the requirements.In order to further verify the correctness of theoretical analysis and simulation,this paper builds an experimental platform for dual band magnetic coupling resonance wireless power transmission system.The function and construction process of each module of the experimental platform are briefly introduced.Separate charging experiments were performed on the 85kHz and 30kHz systems respectively to obtain the frequency characteristic curves of current,output power and charging efficiency.Finally,the simultaneous operation of the dual band system is carried out.The experimental results show that the mutual interference between the two systems has been eliminated,and the difference of the results are small compared with the single operation.The experiment results verify the correctness and feasibility of theoretical analysis and simulation.