Design Of Equalization Control System For Lithium Battery Pack

With the improvement of people's environmental awareness,Lithium batteries has appeared in all aspects of people's lives quickly for its superior performance,and the requirements of the battery management system are getting higher and higher because of the more and more applications.Due to the limitation of the production process and the influence of the environment,the inconsistency of the cell in the battery pack has become the key factor to limit the application of the Lithium battery.Therefore,the equalization control has become a key and difficult point in the battery management system.This paper has carried on the thorough research to the active balancing system.First of all,this paper analyzes the various equalization methods that have emerged,and designs a hierarchical balanced topology.An improved structure is proposed based on the Buck-Boost circuit for the bottom layer,which increases a balanced bridge arm,and the use of coupling inductance as an energy transfer device greatly reduces the current ripple.While the top layer is based on the flyback transformer structure,so that the energy can be transferred from the cell to the battery pack and can also be transferred from the battery pack to the cell,which improves the efficiency of the balance greatly.This structure increases the number of cells that can be balanced and can be used in high-power battery packs.Secondly,the control strategy is studied,and the relationship between open circuit voltage and SOC is analyzed.We find that open circuit voltage can be obtained quickly by curve fitting,so we can perform equalization control using the open circuit voltage.Then the fuzzy control strategy is analyzed,and the program flow chart is designed.Next we build the simulation model in Simulink environment to verify the correctness of the design.Finally,the experimental platform is built to verify the rationality of the design further,based on the simulation results.The experimental results show that the balanced circuit designed in this paper has a good effect on the balance of the whole Lithium battery pack,which increases the equalizing current and reduces the circuit loss.At last,all cells tend to be consistent and the performance of the battery pack is improved.