Research On State Estimation And Management System Of Ternary Lithium-ion Batteries

In order to cope with climate change and promote the strategy of green development,new energy vehicles represented by electric vehicles have gradually become an important force in the development and transformation of the automobile industry under the support of the positive policies of various countries.To vigorously develop new energy vehicles is also the only way for China to transform from a big country of automobiles to a powerful country of automobiles.Long life,strong security,the high energy density of the ternary lithium-ion power battery is widely used in electric vehicles,in the further study of lithium-ion battery performance,based on research and development of corresponding battery management system,control and management of power battery reasonably and effectively is the key to guaranteeing safe and reliable electric cars.In this paper,the 18650 nickel-cobalt-manganese ternary lithium-ion battery is taken as the research object,its basic characteristics are analyzed,the equivalent circuit battery model is established,and the estimation algorithms of the state of charge and state of health of the lithium-ion battery are studied.By improving the nonlinear Kalman filter algorithm,the high-precision estimation of the state of the lithium-ion battery is obtained.And for 13 series of 48 V light electric vehicle applications related to battery management system hardware and software design and development.Firstly,the characteristics of the capacity,open-circuit voltage,and internal resistance of the nickel-cobalt-manganese ternary lithium-ion battery are studied through experimental tests.On this basis,a high-precision battery model was established and parameters were estimated.Secondly,given the core problem of the battery management system,the algorithm estimation of the state of charge(State of Charge,SOC)was discussed in-depth,and the Square Root Cubature Kalman Filter(SRCKF)was proposed to estimate the SOC.The simulation results showed,with high accuracy and robustness,the estimation error is within 1%,and based on SOC estimation,research on the health status of lithium-ion battery SOH.Then the key technical issues of the battery management system are analyzed,and the solutions to battery pack monitoring,inconsistency,life cycle informatization,and intelligent diagnosis are discussed separately.Finally,for the engineering application of 13 series of 48 V battery packs,a model-based design method is used to develop and design application layer software and hardware.Complete the battery management system’s design plan for collecting battery voltage,temperature,and current.At the same time,use the high-voltage side field effect transistor strategy to control the battery charging and discharging,provide pre-charging safety measures,and design the corresponding power management circuit and secondary protection.The circuit provides a low-power BMS reference design for 48 V light electric vehicles.