Research On Magnetically Coupled Resonant Wireless Charging Technology Based On Double LCC Compensation

The number of electric vehicles is gradually increasing,and their charging methods are the focus of research on electric vehicles.Nowadays,the charging method of electric vehicles is mainly wired charging which is less flexible and safe.Wired charging devices and wires are susceptible to aging and are prone to electrical sparks when unplugging charger connectors.Magnetically Coupled Resonant Wireless Power Transfer(MCRWPT)technology improves the flexibility and safety of electric vehicle charging by eliminating the need for wire.Lithium batteries are used in the field of electric vehicles because of their high energy density,long life and fast charging.The lithium battery has a constant current and then constant voltage charging characteristic,so the MCR-WPT system needs to have a high efficiency constant current and constant voltage output mode.Firstly,the characteristics of several WPT technologies are compared and then the MCR-WPT approach is chosen to power the electric vehicle,and the output characteristics of the four basic compensation networks and the higher-order double-sided LCC compensation network are analyzed using the two-port network model,and finally the double-sided LCC compensation network is chosen as the compensation mechanism of the MCR-WPT system to improve the power factor and output efficiency of the system.Then a simple system parameter design method is proposed according to the parameters of the loose-coupled transformer and the charging characteristics of the lithium battery,which can realize the constant-current and constant-voltage mode output in the resonant state without changing the hardware parameters of the MCR-WPT system and without increasing the external circuit,and only changing the system operating frequency.Then the simulation results of Maxwell software were then used to select a circular coil with a strip core that has good resistance to offset and to obtain a set of simulation parameters for the coil.According to the simulation parameters of the coil and combined with Simulink simulation software to verify the correctness of the proposed system parameter design method,the system can achieve constant current output at the constant current frequency point and constant voltage output at the constant voltage frequency point in the resonant state,and the control strategy of frequency conversion is selected to realize the switching of the system constant current mode output and constant voltage mode output.Finally,an experimental prototype set of magnetically coupled harmonic radio energy transmission with constant current output of 2A,constant voltage output of 25 V,and maximum output efficiency of 87.5% was built to simulate wireless charging of electric vehicles,and also to verify the correctness of this parametric design approach.When the experimental prototype works at constant current output frequency point and constant voltage output frequency point,the output current of the system inverter circuit lags behind the output voltage by a certain angle,which can realize the zero voltage turnon of the switching tube.