Design Of A Magnetically Coupled Resonant Wireless Bi-directional Converter In Electric Vehicle

Bidirectional DC-DC converters are widely used in many power applications,such as the electric power grid system(V2G)and so on.At present,the insertion or hardwired charging and discharging methods are susceptible to pollution and humidity,and it is difficult to adapt to the harsh working environment.In addition,frequent plugging can cause wear and tear on equipment,and there are safety hazards such as spark and leakage.In view of the above problems,this paper applies the wireless energy transmission to V2 G technology and designs the magnetic coupling resonant wireless bi-directional vehicle converter,and the former is regulated by the full-bridge converter,and the latter is controlled by the bidirectional buck-boost converter.The frequency mismatch of wireless transmission system is solved by frequency tracking technology.The output of the system is stable through bidirectional buck-boost converter.The thesis mainly completes the following contents:(1)In response to the changes in the wireless resonant capacitance,the problem of the change and drift of the wireless resonant frequency point is caused,and the converter frequency control technology based on frequency tracking is designed.Firstly,by simulating the resonant capacitance of the transmitting and receiving coils in series of different values,the change trend of wireless transmission efficiency,output power and resonant frequency is analyzed.Then,according to the frequency tracking circuit sampling voltage and current phase,determine whether the system works at the resonance point.When the system is out of tune,the frequency and technology are used to adjust the working frequency of the inverter,so that the system always works again in the resonant frequency state.(2)In view of the problem that the wireless transmission system can not be flexible and efficient to charge and discharge the battery,the bidire ctional buck-boost converter is designed.First,the specific parameters of the analog PI controller are calculated by using the small signal model of the bi-directional buck-boost converter.Then,the control strategy of thebidirectional converter is designed according to the charging and discharging characteristics of the battery,and the corresponding software flow chart is drawn.Simulation and experimental results show that the bidirectional buck-boost converter can achieve constant voltage and constant current control,and can maintain output stability when input and load change.The experimental results show that the wireless device can realize the bidirectional flow of energy,while the wireless coil spacing is15 cm,the output voltage of the system is stable at 48 V,and the overall Efficiency is over 90%.In this paper,the efficient transmission and stable output of the wireless bidirectional vehicle converter are realized.Wireless bidirectional vehicle converter are realized.