Maximum Power Tracking Of Magnetically Coupled Resonant Wireless Power Transmission Systems

Compared with the traditional wired power transmission,the wireless power transmission(WPT)has the advantages of convenience,flexibility and strong environmental adaptability,so it has a good application prospect.In WPT technology,Magnetic-Coupled Resonant Wireless Power Transmission(MCR-WPT)has high transmission power,high efficiency,and suitable for medium and short-distance transmission.Therefore,it has attracted more attention from researchers.The maximum power transfer problem is of great significance for the fast charging of the MCR-WPT under special conditions.Therefore,this paper focuses on the maximum power tracking problem of the MCR-WPT system.For the MCR-WPT system,four common circuit topologies are compared and analyzed from the circuit theory,and the serial-string structure circuit topology is selected for modeling and transmission performance research.The relationship between system frequency,transmission distance and resistive load and system transmission power and efficiency is analyzed by simulation,which provides a theoretical basis for studying the maximum power tracking problem.For the maximum power tracking problem of the MCR-WPT system.Firstly,the method of achieving maximum power tracking based on impedance tuning under distance variation is studied.Through the circuit theory derivation,the input impedance characteristics of the system are studied,and the relationship between the distance of the coupled coil and the compensation capacitance and resonant frequency under the maximum power condition is obtained.And then,the capacitance matrix is used to change the resonant capacitor value,thereby adjusting the resonant frequency of the system to achieve the maximum power tracking of the system.However,this method has the disadvantages of low precision and complicated control.Therefore,a maximum power tracking method based on critical coupling point tracking is proposed.First,the correspondence between the maximum power and the critical coupling point is established by theoretically deriving the power model of the system.Then,the constraint conditions to be met by the critical coupling point are given.Further,the frequency tracking of the phase-locked loop is added to the transmitting end to realize the resonance condition and the cascading DC-DC conversion circuit at the receiving end uses the disturbance observation method to achieve the critical coupling impedance matching.Finally,achieve maximum power tracking of the system.The simulation fully demonstrates the effectiveness and superiority of the proposed method.The hardware and software design of MCR-WPT system is carried out for the maximum power tracking method based on critical coupling point tracking.The feasibility of the proposed method is verified by experiments.