Modeling And Optimization Of Multi-coil Wireless Power Transfer System

Wireless power transfer（WPT）is playing an increasingly important role in consumer electronics,and the research on wireless power transfer system is becoming more and more active.This thesis is subject on modeling and optimization of multi-coil wireless power transfer system,based on the basic circuit theory.With the help of MATLAB and LTspice,focusing on modeling of the high-frequency self inductance,resistance and mutual inductance of cylindrical spiral coil and flat spiral coil,studying on the electrical characteristics of two coil and four coil wireless power transfer system.Using genetic algorithm to optimize two coil and four coil wireless power transfer system’s efficiency.The main research is divided into three parts.The first part is the modeling of cylindrical spiral coil and planar spiral coil.First,the theoretical mathematical model is analyzed for each kind of coil.The proximity effect and mutual inductance calculation in resistance modeling are emphasized.After getting the results of the electrical parameters of a coil,the coil quality factor Q can be obtained,which can help choose proper coil.Secondly,through encapsulate its mathematical model in MATLAB,forming the function script which inputting coil geometric parameters and Outputting its resistance,self-inductance,mutual inductance and other electrical parameters,it is verified and corrected in experiments.The second Part is the modeling of two coil and four coil wireless power transfer system.First of all,two kinds of systems are analyzed theoretically by the basic circuit principals,then MATLAB will call LTspice to run electricity circuit simulation,and finally forming a function script that when you input system geometric parameters,it will output system efficiency,system power and other electrical parameters.With the same parameters,a practical experience is done to make verification.And then the influence of power supply internal resistance,optimal load（load matching）and frequency splitting are analyzed theoretically.For qualitative analysis of the system,the simplified model is used,and the corresponding solution is put forward,and then the verification is carried out.Focusing on the frequency splitting phenomenon,the reason of frequency splitting is given from the angle of energy flow and the corresponding solution is proposed.Through analysis,it is concluded that the four-coil wireless power transfer system has more advantages over two coil wireless power transfer system in some aspect.The third part is first working out the mathematical model which are objective function and constraint conditions of the wireless power transfer system.then using GA algorithm to optimize,finally when you input the range of geometry parameters and the destination electrical parameters of the system which you want,you will get the optimization geometry parameters which can perform perfect consistent with the destination electrical parameters.Two coil and four coil wireless power transmission system are used as example in small and large size.A four coil wireless power transfer system is especially proposed and verified.With a destination and constraint that is 100W output power,40V output voltage,2.5A output current.Combine the above three parts of the content,based on the joint effort of MATLAB and LTspice,in order to form a complete set of integrated design of wireless power transfer system,which is from material to performance that is easy to understand,easy and convenient.