Design And Implementation Of Magnetically Coupled Resonant Based Wireless Energy Transmission System For Electric Vehicles

Recently,electric vehicles which use electric wire charging piles to supplement electric vehicles have high requirements for equipment installation sites,weather regimes,and manual wiring,etc.Meanwhile,the manual wiring operation is cumbersome as well as there are some certain safety hazards in it,which limit the promotion of charging piles and electric vehicles.By using non-contact charging operation with simple,safe,and easy,the requirement of wiring plug-in can be omitted.In this dissertation,a wireless energy transmission system based on the magnetically coupled resonant mechanism for electric vehicles was developed.The system has longer transmission distance compared to electromagnetic induced energy transmission,and has greater transmission power than microwave energy transmission.The closed-loop controlling strategy was proposed to realize the non-contact energy supplement of the power batteries.To analyze the magnetically coupled resonant wireless energy transmission mechanism,the resonant circuit and transmission compensation structure were used.Compare the characteristics of RLC series resonant and RLC parallel resonant circuit,and the RLC series resonant structure was chosed.The transmission mechanisms of the SS and the SP compensation structures were also considered and the SS compensation structure was selected to carry out the research finally.Constructing the coupling model of the system,and analyzing the influences of resonant inductance parameters and loading resistance on the system transmission,the overall topology of the system was designed.In addition to the above mentioned,a three-stage power conversion structure converter was introduced into the system.The first-stage is AC/DC process which converts the power-frequency three-phase alternating current into adjustable DC power to make the input power factor of the wireless energy transmission system meet the relevant standards.The second stage is DC/DC process which provides an adjustable in a wide range,low output ripple,and precisely controllable DC power for the rear stage.The third stage is DC/AC process which converts the direct current into a high frequency alternating current of 80 kHz and transmits the alternating current from the primary coil of the resonant network to the secondary coil.The synchronous rectification section converts high frequency alternating current received on the secondary side into the direct current voltage to charge batteries.Considering the shortcomings of the traditional simple compensation capacitors,the resonant transformation topology of magnetically coupled resonant wireless energy transmission system with bilateral CLC compensation was proposed.After theory analysis of the system topology and numerical simulations,the compensation topology designed can realize the voltage regulation at a given frequency and current source output with the coupling and loading conditions having no influence on primary excitation current.As for the primary side,Zero Voltage Switchs(ZVS)was realized by adjusting the secondary side compensation capacitance precisely.Meanwhile,the controlling circuit,driving circuit,primary side controlling algorithm,secondary side controlling program and systematic communication protocol of the system were all designed to realize constant current charging for power batteries and make the system more secure and reliable.In conclusion,a prototype of 6.6KW magnetically coupled resonant electric vehicle wireless energy transmission system was developed.Its various functions and indicators were tested by using 30 series power batteries,rated 12V20 Ah,modeled 6-DZM-20 as the load.The charging experiments were carried out to show the effectiveness of the proposed magnetically coupled resonant theory and the wireless energy transmission system.