Research On High Misalignment Tolerance Static Wireless Charging System Of Electric Car

Nowadays,with the increasing energy and environmental problems,electric vehicles(EV)attract the attention of the entire automotive industry because of its clean energy,environmental compatibility and other advantages.Compared with the traditional electric vehic le wired charging,high degree of freedom,good security,large charging range and other unique advantages of wireless power transfer(WPT)technology determine the wireless charging will become the future direction of electric vehicle charging.However,due to the lack of physical connection,the misalignment between the transmitter and receiver during wireless charging has a serious impact on the energy transfer.For the popularity of wireless charging system,misalignment tolerance will be one of the most important factors to evaluate system performance.Aiming at the misalignment existing between the transmitter and receiver,for the output power stability,this paper focuses on the method s to improve misalignment tolerance of the system.Based on the mutua l inductance coupling model,this paper firstly analyzes the traditional wireless charging system based on "series-series" resonant compensation topology,studies the output characteristics of the system and establishes the qualitative relationship between the coupling coefficient and the misalignment.The shortcomings of the traditional resonant compensation strategy in the adaptability of misalignment are studied.Secondly,the non-resonant compensation strategy is introduced in the primary side and the relationship between the transmission power and the input impedance angle is studied.The trend of the transmission power against coupling coeffic ient is deduced and a multi-level compensation network is designed to make up for the decline of output power caused by the non-resonant compensation strategy according to the curve.In this paper,the Boost converter is chosen as the constant current charge controller at the receiver.Three-dimensional curves of charging current against coupling coefficient and duty cycle are plotted.The PI control algorithm is designed and the working process of the system is simulated by Simulink.It is proved that the multi-level non-resonant compensation strategy can improve the system misalignment tolerance.Thirdly,a new magnetic coupler based on orthogonal double coil is designed.It is proved by ANSYS Maxwell simulation that it improves the misalignment tolerance compared with traditional magnetic couplers in X and Y direction.Finally,based on resonant and non-resonant compensation strategies,wireless charging test systems characterized by working frequency of 85 k Hz,transmission distance of 150 mm and rated transmission power of 500 W are established respectively.According to the result of open loop test,when non-resonant compensation strategy is applied,the system can achieve the constant current control of 4 A for 35 Ω resistance load under the condition of 250 mm misalignment in X or Y direction and better misalignment tolerance of non-resonant compensation strategy is proved.