Research On Constant Current Output And Efficiency Optimization Of Wireless Charging System Based On Rectifier Control

Electric vehicle wireless charging technology shall be provided with the advantages of flexible charging and strong environmental adaptability that traditional charging methods do not have which has became one of the current hot research directions.Based on the magnetic coupling resonant wireless power transmission method,this paper aims at electric vehicle constant current charging and system efficiency optimization and conducts research from the topological analysis,control mode and optimization,coil optimization and hardware design.The main contents of this article are as follows:Firstly,the research background and significance of this paper are elaborated,and the classification of Wireless Power Transfer technology and the research status at home and abroad in recent five years are summarized.The principle of magnetic coupling resonant wireless power transfer is introduced in detail,and the characteristics of output current、impedance of primary and secondary sides of four basic resonant topologies and new double-side LCC resonant topologies are analyzed and deduced based on the loose coupling transformer theory which is confirmed through comparison with coupled mode theory.Through analysis,the advantages of double-side LCC resonant topology are confirmed and the detailed characteristics of transmission efficiency and output current are further analyzed.Secondly,the overall structure of the wireless charging system is given and the primary inverter and secondary rectifier of the system are analyzed based on the fundamental harmonic equivalent analysis method.The results indicate that changing the phase shift angle of the rectifier can stabilize the output current and optimize system efficiency at the same time.Based on integral circuit a new PI closed-loop rectifier control scheme is proposed to ameliorate the peak voltage overshoot which the voltage waveform of the traditional synchronous rectification cross zero.The rectifier load conversion function is used to further optimize the control scheme at the same time,which not only meets the output current but also improves the overall efficiency of the system.Finally,the ANSYS Maxwell simulation software is used to simulate and optimize two different planar coils in terms of coil shape,anti-offset ability,and ferromagnetic material influence.According to the optimization results,two coils of different specifications were made.The Altium Designer software is applied to design the control circuit and auxiliary power circuit.Besides the PWM waveform modulation process are explained too.An experimental platform is built to verify the constant current control scheme.The experimental results show that the designed wireless charging system can achieve a constant current output of 3.5A under light load and heavy load conditions.The maximum system efficiency of the prototype reaches 85%.The system can keep the output current and efficiency relatively stable when axial offsetting occured.