Research On State Of Charge Estimation Tactics Of Battery Management System

Owing to global energy shortages and environmental issues have become prominent increasingly, the electric vehicle with many advantages of zero emissions, good environmental performance and diversification of the power energy has attached great importance by each country, and it has been become the new focus of the future vehicle. Currently, there are many problems about the development of the electric vehicle, battery and its energy management system as the key technologies have been the focus of the research, the accurate estimation of state of charge (SOC) of the battery is essential for battery energy management system to normal operation in the electric vehicle. The main content of the subject is to research the strategy of SOC estimation around the nickel-hydrogen battery.First of all, the research background and source of the subject are introduced, the research current situation of SOC estimation is analysed, and the importance and reality significance of the subject are to explain. Then the work principles of the nickel-hydrogen battery is introduced, the various definitions of SOC are discussed. The all kinds of factors influencing of SOC are analysed and various different the strategies of SOC are compared. On the basis of these, the subject about the ideas and strategies of the nickel-hydrogen battery SOC estimation are presented, there are static SOC estimation and dynamic SOC estimation theory respectively.Secondly, the characteristic of the nickel-hydrogen battery and static SOC estimation theory are analysed. Through a series of charge-discharge experiments under different conditions, we can obtain the influencing relationship between the open circuit voltage, charge-discharge rate, temperature and SOC estimation. Based on this principle, static SOC-open circuit voltage estimation strategy, static SOC-charge and discharge rate estimation strategy, and static SOC-temperature estimation strategy are established respectively, these estimation strategies provide the basis for establishing dynamic SOC estimation strategy.Finally, dynamic SOC estimation theory are analysed in detail, it is based on the battery model, and the estimation results of SOC are influenced the accuracy of battery model directly. Therefore, the establishment of dynamic model of the nickel-hydrogen battery is based on models which are used in the study currently, and the methods to obtain the parameters of the battery model are discussed. According to the nonlinear filtering theory and based on the dynamic model of the battery, a state space model of the battery is proposed. SOC is estimated by dynamic SOC estimation strategy based on state space model. The results of simulation and experiments are given, they indicate that dynamic SOC estimation strategy proposed in the subject keeps better excellent accuracy, and the capacity of resisting disturbance and robustness of dynamic SOC estimation strategy are verified. They are simulated the dynamic characteristics of the nickel-hydrogen battery very well.The subject about SOC estimation strategy has got some achievements in theory and practice. It provides references for the further research on SOC estimation strategy of the nickel-hydrogen battery.