The Maximum Efficiency Tracking Of Wireless Power Transfer System

Magnetically-Coupled Resonant(MCR)Wireless Power Transfer(WPT)has high potential application value because of its advantages of transmitting large amounts of energy over medium and long distances.Efficiency is always a key issue in wireless energy transmission systems.Therefore,this paper focuses on the research of maximum efficiency tracking for MCR-WPT systems.According to the four basic topologies of WPT system,the steady-state efficiency model is established by circuit theory,and the efficiency model is simulated and analyzed.The characteristics of four topologies and the relationship between efficiency and various factors are obtained,which is the maximum efficiency.The tracking and selection of experimental design options provide a theoretical basis.For the MCR-WPT system with S-S structure,the research is carried out about three maximum efficiency tracking methods.For the resonant frequency tracking method,firstly,the efficiency model of the system is analyzed deeply,and the "resonance" is the necessary condition for the system to achieve maximum efficiency;furthermore,the resonant frequency tracking scheme based on PLL is given,and the feasibility of realizing the maximum efficiency tracking is verified by simulation.For the impedance matching method,and it is concluded that the state,the transmitting and receiving circuits are both in resonance in same frequency at the same time,is only a necessary condition to achieve maximum efficiency.Furthermore,it is analyzed and proved that,under the resonate state above,there exists an optimal load which can make the transmission efficiency reach the maximum possible,when the coil mutual inductance(coil distance)is given.Then the DC-DC impedance conversion circuit is introduced to make the system obtain the equivalent optimal load under any actual load.The disturbance observation method is used to achieve the optimal equivalent load matching and maximum efficiency tracking.Furthermore,the maximum efficiency tracking scheme based on optimal impedance matching with phase-locked loop resonant frequency tracking is proposed and designed.For the transmitter minimum power tracking method,keeping the output voltage or power of the load side unchanged,the maximum efficiency is achieved by controlling the output power of the transmitter to track its minimum power;furthermore,the mathematical model of the output DC-DC converter is established by the state space averaging method and the algorithm of the voltage stabilization controller is designed.The disturbance observer method is used to design the input minimum power point tracking algorithm.The hardware design of a MCR-WPT system is carried out,and the impedance matching method is selected for the maximum efficiency tracking software design.The experiment for maximum efficiency tracking is realized.