Research On Wireless Charging Technology Of Electric Vehicle Based On Secondary Variable Inductor

With the development of wireless power transfer(WPT)technology,its application to the field of electric vehicle charging is of great significance for the promotion and intelligent development of electric vehicles.However,due to the structural characteristics of WPT system and the needs of power battery charging mode,realizing constant current and constant voltage output with misalignment tolerance has always been the research hotspot of the electric vehicle WPT system.The traditional frequency modulation and phase-shifting control methods need complex control strategies and the requirements of wireless communication between the primary and secondary sides,while multistage DC-DC conversion will increase the volume and cost of the system.Based on this,a WPT system different from the above traditional control methods is studied.Firstly,after analyzing the research status of improving misalignment tolerance and realizing constant current and constant voltage output at home and abroad,the variable inductor is introduced into the secondary side of double-sided LCC compensation network and LCC-S compensation network,and the secondary side variable inductor control technology is proposed.Compared with the traditional control methods,this technology avoids the requirements of wireless communication between the primary and secondary sides and cascaded DC-DC converter,and only needs to change the variable inductor to realize the constant current and constant voltage output with misalignment tolerance,which improve the reliability of the system and reduce the volume and cost.Based on the fundamental harmonic approximation method and the mutual inductance coupling model,the expression of the variable inductor in the two compensation networks is deduced,and the variation range of the variable inductor in the two compensation networks is compared and analyzed.Based on this,the optimal compensation topology is determined,and its input impedance characteristics are studied.Secondly,aiming at the principle of the variable inductor,the magnetization curve and magnetic circuit model are adopted to analyze the principle of the variable inductor in detail by image and formula.The correctness of the two analysis methods is verified by measuring the manufactured variable inductor.Finally,the loosely coupled transformer is designed and manufactured.On this basis,the main circuit and control circuit of the WPT system are designed,and a 3k W experimental platform is built to complete the constant current and constant voltage output experiment.The relevant experimental results show that the constant current and constant voltage output characteristic with misalignment tolerance can be realized by controlling the secondary variable inductor,which verifies the effectiveness of the proposed secondary variable inductor control method.According to the experimental results,the variation curve of the variable inductor is drawn,which is basically consistent with the theoretical analysis.In the whole working process,the system can realize the zero voltage switching of the primary inverter,which ensures that the system has high transmission efficiency in the process of the energy transmission.