Design And Implementation Of Wireless Power Transfer System Based On Active Impedance Matching

Magnetically Coupled Resonant Wireless Power Transfer（MCRWPT）is a way to realize wireless transmission of electric energy by using magnetic field energy as relay energy.Compared with traditional wired power transmission,MCRWPT has the advantages of convenient use and high safety,and has been gradually used in electric vehicles,home appliances,mobile terminals and other fields.However,in practical applications,load changes and input voltage fluctuations will cause problems such as a drop in the transmission efficiency of the WPT system and changes in the output voltage,which cannot meet the requirements of high efficiency and stable voltage for electrical equipment.Therefore,designing a WPT system with high transmission efficiency and stable output voltage has important engineering value.In order to solve the above problems,this thesis uses the method of Buck converter for impedance matching to achieve high transmission efficiency within a certain range of load changes,at the same time,to achieve output voltage stability by controlling the phase shift angle of the inverter,and establishes an experimental prototype of WPT system with rated power of 200 W for verification.The work done in this thesis is as follows:Firstly,the basic working principle of WPT system is introduced.The characteristics of four basic compensation topologies and two common composite compensation topologies are compared and analyzed.LCC-S topology is selected as the compensation topology of the system,and its transmission characteristics are analyzed,and the optimal load conditions for achieving the highest transmission efficiency are derived.Secondly,the impedance matching method is selected,the realization principle of impedance matching using Buck converter is expounded,and the impedance matching range is calculated.Then,a WPT system using a bilateral control scheme is designed;In this scheme,the duty cycle of Buck converter is adjusted to ensure that the equivalent load at the receiving side tracks the optimal load conditions,so as to improve the system efficiency.At the same time,the output voltage of the system is stable by controlling the phase shift angle of the full bridge inverter at the transmitting side.Then,the software and hardware design of the WPT system are carried out.The hardware part includes the parameters calculation and selection of the device of the compensation topology and the Buck converter in the main power circuit,the design of the DSP peripheral circuit,the voltage and current sampling circuit,the drive circuit and the wireless communication circuit in the control circuit.The software part includes the initialization configuration of DSP and the design of program algorithm.Finally,the PSIM software is used to build the system circuit for simulation analysis to preliminarily verify the feasibility of the bilateral control scheme.Then a system prototype is built for experimental analysis.The experimental results show that the WPT system designed in this thesis can maintain high transmission efficiency and achieve output voltage stability under different input voltage and load conditions.