Research On Two-way Balance Control Method Of Lithium-ion Battery Pack

The advantages of power batteries are higher charging and discharging times,higher energy density,and no memory effect.As an energy storage device,it can be applied in many fields such as new energy vehicles,spacecraft,and wind power generation.However,the battery pack faces complex and diverse use environments,and they often appear unbalanced situation,which causes irreversible damage to the entire battery pack.In order to solve the above problems,this paper combines the advantages of high-frequency switching of switching converters,and proposes a new and efficient Bidirectional forward and flyback converter battery pack energy balance topology to improve the energy conversion efficiency of batteries.Firstly,the balanced topology of the battery pack is sumarized,focusing on the analysis of two types of energy dissipation equilibrium and non-energy dissipation equilibrium.The article summarizes the advantages and disadvantages of the topology and the scope of application.Aiming at the equalization structure and point-to-point equalization method of traditional coaxial multi-winding,an improved new bidirectional equalization topology is proposed,and the demonstration and principle analysis of the design scheme are performed according to each system module,including the flyback and forward conversion Analysis of the principle of the controller,calculation of the main circuit parameters,analysis of the two-way equalization efficiency and so on.Secondly,a battery equalization control platform for the new topology is built.The system includes a battery voltage and temperature detection module,a control switch module and forward and flyback converter module.Based on the improved new two-way equalization structure,a system control strategy is formulated.In order to monitor the change of the power of the individual cells in the battery pack,LABVIEW is used to set up the monitoring interface of the upper computer.Finally,in order to verify the effectiveness of the proposed circuit,a 12-cell battery 2800-MAh battery string was applied for experimental verification.Computer monitoring(LABVIEW)is adopted to adjust the energy imbalance of the battery pack.The overall equilibration time of the new topology tends to be consistent after 5000 s.In the end,the voltage of all battery cells tends to 3.35 V,and 86.9% energy utilization during cell balancing.The experimental results show that the new battery bidirectional equalization circuit has good equalization performance.The new bidirectional equalization structure adopts the balance idea of combining point-to-point and multi-point.Compared with the traditional equalizer,the proposed equalizer can quickly equalize two high and low power batteries at the same time,which has certain practicality and innovation.