Research On Energy Efficiency Improvement Technology Of Wireless Charging For Electric Vehicles

With economic growth and social progress,problems such as environmental pollution and energy depletion have become more and more serious.As an important development project for sustainable development,electric vehicles have increasingly attracted the attention of the country and the general public.Electric vehicles can be charged in two ways: wired charging and wireless charging.Wire charging is easy to generate sparks in the process of charging,and the risk of charging is greatly increased in the harsh conditions of rain and snow.Wireless charging mainly relies on the principle of electromagnetics,which overcomes the shortcomings of wired charging,and will greatly accelerate the promotion of electric vehicles.However,the bottleneck of wireless charging is low charging efficiency and short transmission distance at present.Therefore,it is of great significance to study the efficiency improvement technology of wireless charging for electric vehicles.In order to solve the problem of low efficiency and power in the wireless charging process of electric vehicles,this article first analyzes the compensation network and selects a proper compensation network for the wireless charging system based on the analysis results.Then a mathematical model is established to analyze the power and efficiency curve and influencing parameters of the system,and a control strategy to suppress frequency splitting is given.Finally,a set of resonant wireless charging circuit for electric vehicles is designed.The main research contents are as follows:(1)For the resonant wireless charging system,the working principle and basic circuit composition are introduced.The characteristics of the four resonance compensation networks are studied.By studying their impedance characteristics,power characteristics and efficiency characteristics,it is concluded that the selection of SS type compensation capacitors is relatively simple,and which makes the system more stable,and the output power and transmission efficiency of the SS network are also higher.Based on this,the core electromagnetic coupling structure of the resonant wireless charging system is selected,which lays the design foundation for the system to achieve high efficiency and stable work.(2)The two mainstream analysis models for analyzing wireless charging systems-coupled mode model and mutual inductance model are modeled.The coupled-mode model is used to establish a lossless system,and then the necessary conditions for effective transmission of electric energy are obtained.And then the actual charging system under lossy conditions is considered.The transmission efficiency equations and power equations are obtained.Then the parameters that affect the transmission power and efficiency are found.In order to facilitate the detailed design of the parameters of the resonator circuit,the mutual inductance model of the wireless charging system is established.After that,the system parameters are determined by analyzing and studying the relationship curve of each parameter with the system power and system efficiency.(3)Aiming at the problem of frequency splitting in the resonant wireless charging system of electric vehicles and the problem of reducing power,the mutual inductance model is used to analyze the relationship between input impedance and frequency.Then the key parameters that affect frequency splitting are obtained.A method of using a buck converter to adjust the equivalent resistance is given to suppress frequency splitting,thereby improving the power and efficiency of the system.The effectiveness of this method is verified by MATLAB simulation in the end.(4)Based on the basic principles of the resonant wireless charging system for electric vehicles,the design process of each part of the system is discussed in detail,meanwhile,the device parameters involved in the circuit are calculated and explained.The design scheme is simulated using LT spice software.Ultimately,the correctness of the designed scheme is verified.