Research On Battery Equalization System Based On Magnetic Coupling Resonant Wireless Power Transfer Technology

As an emerging technology for electric power transmission,wireless power transfer has received widespread attention because it can solve the problems of aging circuit terminal and poor safety of wired transmission.There are many researchers and scholars at home and abroad have conducted in-depth research on wireless power transfer technology and active equalization system of lithium battery pack,respectively.However,these technologies are not mature enough and most of them remain in the laboratory research stage.Besides,there are few people applying the wireless power transfer technology in lithium battery active equalization system.Considering the structural characteristics of the lithium battery pack,this thesis mainly studies two aspects of the magnetic coupling resonant wireless power transfer system,namely the compensation structure of the magnetic coupler and the bidirectional power transfer.The specific contents are as follows:Firstly,the six basic compensation structures of the magnetic coupling resonant wireless power transfer are modeled in circuit.Then the output characteristics are analyzed to obtain the advantages and limitations of each compensation structure.The output characteristics of one LCC compensation structure are very suitable for the charging and discharging of low power batteries.However,considering the application scenarios,the existing compensation structures cannot meet the design requirements.Therefore,a new LCC-S-S-LCC compensation structure is proposed on the basis of LCC compensation structure in this thesis,which can not only retain the transmission characteristics of double LCC compensation structure,but also meet the structural requirements.Secondly,the mutual inductance equivalent model is established for the new LCC-S-SLCC compensation structure proposed in this thesis to obtained the relationship between various parameters of the system at resonance.Then,the transmission characteristics are analyzed to facilitate the device selection in design.The phase-shifting control is used to realize the bidirectional power transmission,and the Pspice simulation model and Ansys Maxwell coil model are built to verify the proposed theory.Besides,the influence of crosscoupling effect on the transmission power of the system and the influence of voltage gain on transmission efficiency are analyzed.At the same time,the MATLAB/ Simulink simulation model of lithium battery pack active balance is built to verify that the topology can quickly balance the voltage between the two batteries.Finally,a bidirectional power transfer platform on the same side is built to verify the correctness and feasibility of theoretical analysis.The distance between the relay coils plate and the energy transfer coils plate is fixed to measure the actual values of the actual selfinductance,mutual inductance and cross-coupling mutual inductance so as to determine the parameters of other devices in the compensation network.Then,the drive circuit as well as the voltage and current sampling circuit are designed with STM32F103C8T6 chip used in the controller.Through the experimental verification,the magnetic coupled resonant wireless power transmission system with the new LCC-S-S-LCC compensation structure not only can realize the power transfer of the energy transfer coil in the same plane,but also can realize the direction control of power transmission through the phase shift control.Moreover,the transmission efficiency of the system has been verified to reach as high as 81.5 %.