Design Of Magnetic Resonant Wireless Power Charging Method For Power Battery Of Small Electric Forklift

At present,the method of direct plug-in charging is used to charge the power battery of electric forklift,it has some shortcomings,such as inconvenient operation,charging line easy to wear and so on.Compared to the direct plug-in charging,non-contact wireless charging has many advantages,for instance,convenient to operate,safe and reliable,and without the electrical connection.This paper adopt wireless charging technology of magnetic resonance,a wireless charger for the power battery of electric forklift is designed.Its rated output voltage is 30V and rated output current is 5A.The charging characteristics of the electric forklift and the charging mode of the electric forklift are studied.The charging method of the two-stage constant-current/constant-voltage is selected.To realize the fast charging,the large current charging is carried out at the initial stage;to ensure the battery filled fully,constant voltage charging is carried out at the later stage.Finally,the overall design scheme of magnetic resonant wireless charging system is determined.Based on the theory of resonance,the principle of magnetic resonance wireless charging system is studied.Using the coupled circuit model and mathcad software to analyze the coupling coefficient,load and working frequency for the influence of transmission characteristics.Compared with the advantages and disadvantages of phase shift control and frequency conversion control,the control strategy of frequency conversion control is selected.In addition,the working principle and steady-state characteristics of the resonant conversion circuit are described in detail.The Saber simulation software is used to simulate the output requirements,the working frequency and the main circuit parameters,and provide the guidance for the design of the wireless charging system.The preceding stage of wireless charging system is the power factor corrector,which based on the L6561 chip,and the working principle and main circuit parameters of the PFC converter are analyzed.The basic working principle and circuit parameter selection method of resonant conversion circuit,driving circuit,sampling circuit and protection circuit are introduced in detail.The requirements of resonant capacitor selection and the design of resonant coil are given.STM32 is chosen as the host controller of former-vice edge,through the wireless module NRF24L01 to realize the communication of former-vice edge,and through the LCD module to implement the display and monitoring of the battery state.Applying the PI algorithm to adjust the system working frequency,to achieve the aim of closed-loop control.A prototype system is developed,and experiment is studied on the wireless charging system,and experimental results verify the feasibility of the scheme.