| Magnetic coupled resonance(MCR)wireless power transfer(WPT)technology is widely used in smart home appliances,electric vehicles,implantable medical devices and other fields due to its high transfer efficiency,long transmission distance and small impact on human body.However,the MCR-WPT system is a multi-parameter coupling system,and the power transfer efficiency is greatly affected by the distance between the transmitting coil and the receiving coil,the change of load impedance,the change of circuit component parameters and other external environmental factors.In this paper,based on the circuit theoretical modeling of MCRWPT series-series topology,the maximum efficiency tracking is taken as the goal,and the effects of resonant frequency,equivalent load impedance and frequency splitting on transfer efficiency are analyzed.This paper has carried out the following research work:(1)Aiming at the problem of frequency detuning,two fuzzy adaptive frequency tracking control methods are proposed.Based on the real-time PI closed-loop system of transmitter inverter,by analyzing the influence of control parameters on system performance,an adaptive control mechanism based on fuzzy rule table and fuzzy inference is established.In order to enhance the adaptability to the changes of system parameters and frequency fluctuations,an adaptive control method based on fuzzy RBF neural network is proposed.The PI parameters are adjusted in real time according to the phase difference and the change rate of phase difference,and the phase difference is always locked at zero to ensure that the system is always in the resonant state.Simulation and experimental results verify the effectiveness of frequency tracking control.(2)Aiming at the problem of load impedance matching in power transmission of the MCRWPT system,a calculation method of equivalent load impedance matching in maximum efficiency tracking using neural network is proposed.Based on the theoretical analysis of the optimal load conditions,firstly,the passive CLCC type impedance matching network is designed,and the matching factor is introduced into the set value of capacitance and inductance to skillfully eliminate the inductive part of rectifier load,so that the equivalent load impedance is always purely resistive.Taking the coupling coefficient and rectifier load value as the inputs of the GA-BP neural network,the capacitance adjustment value of the matching network is deduced in real time,and the programmable capacitance array is used to realize the accurate and wide range matching of the capacitance.Simulation and experiments show that the proposed impedance matching method can eliminate the influence of nonlinear characteristics of rectifier circuit and realize maximum efficiency tracking control in a wide load impedance variation range.(3)According to the requirements of constant voltage power supply for battery load,a new method of real-time estimation of coupling coefficient based on data communication is proposed to realize the maximum efficiency tracking control with constant voltage output.Based on the comprehensive consideration of frequency tracking and impedance matching,the circuit structure of transmitting side in MCR-WPT system is optimized,and the dynamic coupling coefficient with unique solution is deduced by using the circuit parameters detected in real time.The experimental system is built to comprehensively analyze factors related to maximum efficiency tracking,such as the nonlinearity of rectifier circuit,the identification of coupling coefficient,the adaptability of load change and the controllability of output voltage.The experimental results show that the high-efficiency and constant voltage power supply is realized under the change of coupling coefficient and load impedance.(4)Aiming at the transfer efficiency of MCR-WPT system in high frequency band,the transfer efficiency of equivalent resonant circuit and non-equivalent resonant circuit in over coupling region is studied and discussed by combining theoretical analysis and experimental verification.The results show that the transfer efficiency can remain constant in the equivalent resonant circuit even if frequency splitting occurs.The MCR-WPT system with single transmitting and double receiving coil structure is built,and the relationship between the total system power transfer efficiency,the quality factor of coil circuit and the distance between coils is studied,which provides a reference basis for circuit design for improving the power transfer efficiency of the multi-receiving MCR-WPT system. |
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