Research On Key Technologies Of Accurate Alignment Of Electric Vehicle Wireless Charging Coils Based On Magnetic Induction

With the rise of the new energy industry,the market share of electric vehicles is gradually expanding.Compared with wired charging technology,wireless charging technology has the advantages of safety,high efficiency,low loss,etc.,so it is more favored by people.When the electric vehicle is wirelessly charged,the alignment of the receiving and transmitting coils of the system directly affects the efficiency of the entire charging system and the transmission power.Therefore,the high-precision alignment technology for wireless charging of electric vehicles is studied for the promotion of electric vehicles and the development of new energy industries,which is of great significance.Based on the principle of magnetic induction,this paper designs a new type of LC sensor coil alignment system to achieve high-precision alignment of the receiving and transmitting coils.In chapter 1,a detailed investigation on the types and development of wireless charging technology and positioning technology at home and abroad is made,including their advantages and disadvantages.In chapter 2,the calculation method of mutual inductance between coils is derived from Biot’s Law firstly,which indicates the relationship between the mutual inductance of coils and the offset distance between coils in detail.and then the equivalent circuit of the new LC sensor coil alignment system is proposed,which can help calculate the circuit parameters,and give the impedance calculation formula at the resonance frequency point as a basis for alignment.Finally,the principles of common positioning technology are properly introduced.In Chapter 3,the structure and equivalent circuit model of the planar spiral coils used in this system are first analysrd,and then the spiral coils of six different sizes are simulated in HFSS which help extracts their equivalent inductances and equivalent resistancse.On this basis,the situation where there is only a single LC sensing coil is simulated,which reveals the law of input impedance change in the frequency domain: the maximum impedance is obtained at the resonance frequency which decreases with the increase of the offset.Then the three-dimensional LC sensor coil alignment system simulation is carried out,and the extremum value can be obtained at three different resonance frequency points which increases with the growth of the resonant frequency point.Finally,a compensation resistor is added to reduce the impedance at the high resonant frequency so that the impedance at the three resonant frequency points are approximately equal when the coil is aligned.Finally,the impedance measurement of the designed three groups of LC sensor coil alignment system is carried out,and a simple host computer program is designed based on Matlab,which is used to display the measurement results on the computer and gives relevant displacement prompts according to the measured impedance value.According to the prompts,the system finally achieves alignment after multiple displacement iterations on the secondary coils.The measured impedance results are slightly higher than the simulation results.After the final alignment,the lateral offsets between the three sets of coils are 1.6mm,4mm and 4.5mm,which indicates that this design realizes the high-precision alignment of the transmitting and receiving coil,and the structure is simple.