Research On Constant Current And Constant Voltage Control Of Mobile Wireless Charging System For Electric Vehicles

Electric vehicle wireless charging is a safe,reliable and convenient new contactless charging technology.The mobile wireless charging technology allows electric vehicles to "charge while running" while driving on the charging track,replenishing power in real time,effectively alleviating the mileage anxiety of electric vehicle users.How to quickly supplement the state of charge of vehicle power battery in a short time on a limited length of charging road without reducing its service life is an urgent problem for researchers to solve.Inductive coupled power transmission(ICPT)technology has the advantages of high short-range transmission efficiency and is suitable for high-power transmission of electric energy.It provides technical support for mobile wireless charging of electric vehicles.Mobile wireless charging needs to use high current to charge the vehicle power battery at the initial stage of charging.In order to prolong the service life of the power battery,it is necessary to switch to the constant voltage charging mode when charging to the set voltage threshold.In the moving process of electric vehicle,the change of the coupling area of the transceiver coil will lead to the fluctuation of mutual inductance parameters.At the same time,the change of the equivalent resistance of the power battery in the charging process will also affect the stability of the output current and voltage of the mobile wireless charging system.Therefore,the research on electric vehicle mobile wireless charging(EV-MWC)system based on ICPT technology and with constant current and constant voltage output characteristics has important theoretical significance and practical value for alleviating the "mileage anxiety" of electric vehicle users and prolonging the service life of electric vehicle power battery.Taking the constant current and constant voltage charging of electric vehicle on-board power battery as the application background and EV-MWC system based on ICPT technology as the research object,this paper mainly studies the constant current output control,constant voltage output control and constant current and constant voltage switching control of EV-MWC system.Firstly,the research status of EV power battery charging technology and EV-MWC system in modeling and control methods at home and abroad is described.Secondly,the overall structure and working principle of EV-MWC system based on ICPT are introduced.Through the comparative analysis of the circuit characteristics of basic compensation structure and typical high-order compensation structure,the resonant compensation structures used for constant current output control,constant voltage output control and constant current and constant voltage self switching control of EV-MWC system are determined.Considering that the mutual inductance fluctuation of the coupling mechanism between the primary side and the secondary side and the load disturbance of the power battery will affect the constant current output of the EV-MWC system in the process of mobile wireless charging of electric vehicles.Firstly,based on the mutual inductance coupling theory,the Euler Lagrange(EL)model is obtained on the basis of establishing the dynamic model of EV-MWC system and the large signal model in d-q coordinate system.Then the passive controller(PBC)based on El model is designed from the perspective of energy to analyze the passive stability of the system.Finally,it is compared with the traditional dq-PI control in the effect of constant current output control and verified by simulation.Aiming at the influence of mutual inductance fluctuation of primary and secondary coupling mechanism and load disturbance of power battery on output voltage stability in constant voltage charging stage during mobile charging of electric vehicle.Firstly,the relationship between input and output voltage of EV-MWC system based on LCC-S compensation topology is analyzed,the equivalent circuit of the system is obtained,and its dynamic mathematical model is established,which effectively reduces the complexity of subsequent controller design.Then,based on the state space model of the equivalent circuit,the sliding mode voltage output controller is designed to achieve the purpose of constant voltage output in the moving process.Finally,it is compared with the traditional PI control in the effect of constant voltage output control,and verified by simulation.Aiming at the problem of EVMWC system how to realize smooth and fast switching from constant current mode to constant voltage mode without causing jump of charging voltage and charging current,the constant current and constant voltage switching control strategy is designed by using secondary compensation topology switching based on switch and primary PI closed-loop control,and the simulation model of wireless charging self switching system is built,It is verified that the topology switching based on LCC-LCC/S has the jump of charging voltage and charging current at the switching time.Finally,the simulation model of the control method designed in this section is built to verify the feasibility of the control method designed in this section,and compared with the open-loop control.The constant current output control model and constant voltage output control model of EV-MWC system based on ICPT are built in MATLAB/Simulink platform,and compared with the traditional PI controller in controlling the constant current output and constant voltage output of the system respectively.The simulation results show that the designed PBC controller and SMC controller have stronger robustness in the case of external disturbances,and have the advantages of fast response and small overshoot compared with PI controller.The constant current and constant voltage switching controller can suppress the jump of voltage and current at the switching time,and realize the smooth transition of constant current to constant voltage charging mode.