Modeling And Experimental Study Of Wireless Power Transfer System Via Magnetic Resonant Coupling

Wireless power transfer(WPT)technology is a hot issue in electrical engineering.This technology has wide field of application with good prospects at getting rid of the shackles of wires powered device aiming to improve the mobility flexibility of the device,preventing spark and powering the underpit and underwater device.WPT technology via magnetic resonant coupling(MRC)has the characteristics of high transfer efficiency,high load power,and long distance,which has received wide attention by the scholars at home and abroad in the last few years.Howerever,being an emerging approach,there are more unsolved questions about modeling,power transfer mechanism and experimental researches.This paper aims at establishing model for MRC-WPT system,analyzing the power transfer characteristics for systems with different topologies,transmitting power and signal synchronously,and researching the magnetic field distribution of the system.The main research works are as follows:Coupled mode theory and equivalent circuit model are the main modeling methods of MRC-WPT system,and detailed discussions about the two modeling method are carried out.In this paper,models for MRC-WPT system by coupled mode theory and equivalent circuit theory are buildt respectively.The lossless and loss system are analyzed by coupled mode model,and the necessary conditions of energy exchange and tansfer are obtained.More precisely,energy transfer is realized as the resonators is under strong coupling and resonant frequencies of the resonators are equal.Lumped circuit model of MRC-WPT system is built as supplement of coupled mode model to describe the system by circuit struture.According to the resonant structure of the resonator,this paper establishes four kinds of topology model for MRC-WPT system,and analyzes the caculation method of the system scattering parameter in detail to research power transfer characteistic of different coupling states while the resonator is as series resonance.According to the operating frequency band of the MRC-WPT system,and considering the parasitic parameter,the modeling method of partial element equivalent circuit(PEEC)is proposed.The segment unit of PEEC is one turn of the resonator,and each unit is modeled by its self-inductance and AC resistance.The links between different units are built by the turn-to-turn mutual inductances and parasitic capacitances.The partial inductance,partial capacitance and partial resistance of PEEC network are calculated by numerical integrals and analytical formulas,and PEEC model of MRC-WPT sysem is solved by the modified nodal analysis in frequency domain.This modeling method can predict resonant frequency and power transfer capability for MRC-WPT system.Two types of MRC-WPT resonators are designed in our laboratory and some experimental measurements are implemented,and the relevant parameters of the practical system are also simulated by FEKO.The expermental and simulated results show the effectiveness of PEEC modeling method.Aiming at the different feed modes,this paper analyzes the performances of MRC-WPT system with two-coil structure.As the resonator is fed at center or end,the resonator is as two diffenent resonant strutures,and the corresponding MRC-WPT systems are with different topology structures.The lumped equivalent circuits of the two-coil systems with two feed modes are built to analyze the power transfer capability and system efficiency,and the results show that the two-coil system gets high power transfer capability and efficiency as the resonator is fed at certer.The practical resonator and system were design,and PEEC calculation and experiments are implemented on the practical system.The results verify the correctness of theoretical analysis.In order to implement synchronous transfer of power and data in MRC-WPT system with one set of resonator,a design method of dual-band resonator is proposed.MRC-WPT system constituted by this dual-band resonator can provide two channels with different frequencies for power transfer and signal transmission.Power wave and signal wave are both received at receiving side,so notch circuit is proposed to separate signal wave and power wave and the power transfer is not influenced.Dual-band resonator and dual-band system are designed in this paper,equivalent model of the dual-band system is established to calculate the power transfer characteristic and signal transmission characteristic,and the relevant experiments are implemented meanwhile.The calculated and experimental results show that the dual-band system can receive signal effectively without affecting the power transfer.PEEC model is used to calculate the magnetic field of MRC-WPT system.The current distributions of all units are calculated by PEEC model,so the magnetic field distributions of all units can be calculated,then the magnetic field distributions of MRC-WPT system are obtained by superposition.The magnetic field distributions of MRC-WPT system are analyzed at resonant state and detuning state,and the magnetic field distributions are also simulated by FEKO,which verifies the effectiveness of the calculated method.