Simulation And Design Of Lithium-Ion Battery Equalization Technology

The new energy vehicle is an inevitable choice for energy crisis and environmental degradation in China,which has become a national key development of new strategic industries.Battery technology,motor control,battery management system are three keys of new energy vehicles.Battery technology among them is the foundation.It also plays an important role in the safety performance of the battery pack and has become a key technical problem in the field,which is of great significance.The characteristics of lithium-ion battery material and the production process result in the power battery’s inconsistency,complexity in the actual operating conditions.Accurate estimation of battery charge status,and real-time dynamic lossless energy scheduling between cells,are the most important way to solve the new energy vehicle power battery security’s issues.So,the estimation of battery charge state and balance technology become two core technologies of the battery management system.Development of high performance and cost-effective equalization circuit and for specific applications and optimization of equalization strategy are important research problems in lithium-ion battery equalization technology.In the course of the study,the following four tasks were carried out based the needs and arrangements of the project team:1.The preparation of battery materials,development testing of semi-battery and testing of power battery performance during the process of charging and discharging are carried out.The preparation lithium-ion battery cathode material,semi-battery installation and performance testing of semi-battery during charging and discharging are performed,and the preparation process of lithium-ion battery had been mastered;at the same time high-current charge and discharge cabinet was used for the different specifications of power batteries,such as lithium iron phosphate,lithium manganese,ternary and other batteries for charge and discharge performance testing and battery charge state estimation.2.Balanced circuit simulation and equalization strategy research were carried out.Aiming at the technical problems of battery management in new energy vehicles,by consulting a large number of domestic and foreign literatures and writings,based on the analysis and summarization of the relevant equalization technology,combined with the widely used switching power supply technology,the buck-boost converter and bidirectional flyback DC-DC of the balanced circuit was studied and simulated in detail.The research shows that the equalization circuit based on buck-boost structure has the advantages of easy modularity and parallel processing,and the dynamic equalization can be realized.At the same time,using the LTC3300 chip equalization control scheme,LTspice simulation software is used to simulate the chip,and the equalization parameters are obtained.3.A balanced circuit based on relay network control is designed and studied.In order to realize efficient equalization strategy,an equalization circuit based on relay network control is designed.The circuit can control and realize various equalization in real time by MCU.With high efficiency,safety and other characteristics;The circuit with high efficiency,safety and other characteristics can control and realize various equalization in real time by MCU.4.A charging module used in the balanced control circuit had been designed.Based on the LT3741 chip,a constant voltage constant current power output was developed,which achieved charge balance between batteries or battery packs.According to the experimental results,the circuit has a wide output voltage range,high current equalization,and achieves the output voltage self-tuning function according to the balanced mode.As the battery management system is a composite cross,and the whole system is too large,balanced control circuit and balanced charging module,still need more software level strategy research to develop and verify.By participating in the battery management system research and development projects,involved in the whole process of development in the battery technology and battery management system,a lot of work in the balanced technology had been carried out.There are some deeper level of technical problems and basic issues,which still needs to be solved through working and understanding deeply in future.