Research On All-digital Wireless Power Transmission Control System

Wireless Power Transfer Technology(WPT)is a new transmission mode.Compared with the traditional wired transmission mode,it has the advantages of safety and reliability,and is suitable for special occasions such as no access to wires.In its transmission process,high-frequency alternating current generates high-frequency electromagnetic field through the transmitting coil and transmits it to the receiving coil to supply power to the load.The analog control power supply has some disadvantages,such as unstable control signal,component parameter change caused by temperature change,high design cost caused by parameter matching,complex circuit structure and so on.In view of the above reasons,an all-digital Wireless Power Transfer control system based on field programmable gate array(FPGA)was designed in this paper.The two-stage control system was adopted.The former stage used Buck circuit for constant voltage control to adjust the output power.The latter stage used the Digital Phase-Locked Loop to realize the phase and frequency tracking of voltage and current,realized the ZVS soft switch,and improved the transmission power.At the same time,it had a strong anti-disturbance effect on the change of load and resonant frequency caused by the distance,offset and translation between the transmitting coil and the receiving coil,and improved the stability and reliability of the system.The research contents of this paper were as follows: firstly,according to the circuit theory,the mathematical models of the SP and SS topological structures of the two coils of the wireless power transmission system were established.and the relationship between the system resonance frequency and the coil inductance and capacitance was analyzed in detail according to the mathematical model.And SS topological structures was selected to design Wireless Power Transfer System.The scheme design and device selection of the control system were completed according to the system requirements.Considering the power and operating frequency of the system,this project chose MOSFET(IRFP4568)as the power device.Then,The conditions for the Wireless Power transfer system to achieve the optimal transmission efficiency were analyzed,and the scheme of using the Digital Phase-Locked Loop to realize the Frequency Tracking control was determined.The mathematical model of the All-Digital Phase-Locked Loop was established,and the relationship between the modulus K of the loop filter and the phase-locked speed of the Phase-Locked Loop was found through simulation analysis.By adding an adaptive modulus selection module,the speed of phase-locking and the accuracy of phase-locking were improved.Based on Altera’s FPGA EP4CE10F17C8 N,a All-Digital Phase-Locked Loop was achieved.Based on the All-Digital Phase-Locked Loop,this paper designed a phase acquisition module,signal selection module,phase-locked loop PWM module,system protection module,etc.,and completes the closed-loop constant voltage control of the Buck circuit.The simulation was verified by Model Sim software,and conformed to expected design.Finally,the effectiveness of the proposed scheme was verified through experiments,and the main performance indexes of the system were tested.The design of the all-digital Wireless Power Transfer control system was completed.