Research On Ipt Technology Of Electric Vehicle Based On Secondary Side Switch-controlled Capacitor

With the deepening of the low-carbon and environmental protection concept,the electric vehicle industry has ushered in a new era of rapid development.Inductive Power Transfer(IPT)technology,which is more flexible and intelligent,has undoubtedly attracted more attention than plug-in contact charging which has safety problems and inconvenient operation.Due to the characteristics of the misalignment of magnetic coupling mechanism and the increase of battery load equivalent resistance during charging process,realizing constant current(CC)and constant voltage(CV)outputs within a certain migration range is the focus of the research on wireless power transfer.Therefore,a secondary control method based on the switch-controlled capacitor(SCC)is proposed in this thesis.The proposed scheme gets rid of the dependence of real-time communication.By adjusting the equivalent capacitance of the secondary SCC,the compensation network parameters are changed,so as to realize CC/CV charging control of the electric vehicle IPT system.Firstly,various charging schemes of IPT system are discussed for the misalignment of the magnetic coupling mechanism and load disturbance,and an output control technology with secondary side adjustable compensation network parameters is proposed.The LCC/LCC compensation is selected based on the influence factors of various compensation networks on the output characteristics and anti-migration characteristics of the IPT system.Furthermore,the influence of SCC applied to different positions on the secondary side of LCC/LCC compensation network is analyzed,and the main topology of LCC/LCC compensation IPT system based on SCC variable compensation parameters is designed.Secondly,according to the structure principle and working state of SCC,the relationship between the equivalent capacitance and the switch conduction angle is deduced.And the regulation range of SCC in the charging process is determined.According to the characteristics of SCC drive signal and resonant current in the same frequency and phase,based on the traditional phase-locked loop,digital phase-locked technology is designed to realize the control of SCC.Finally,a 2kW experimental prototype was built,and the CC/CV charging under positive alignment and misalignment of the magnetic coupling mechanism are realized by adjusting the equivalent capacitance of the secondary side SCC.The peak efficiency of CC and CV charging stage is 91.2% and 86.9%,respectively.The experimental results verify the feasibility of the proposed scheme.