Research On Equalization Control Of Lithium Battery In Electric Vehicle

Because of its clean and environmental protection, the development of electric vehicles has become the first choice for electric vehicles. Due to the inconsistency problems of using lithium battery groups, will cause the decline of lithium battery life, so it is necessary to use battery equalization to effectively control the lithium battery, in order to eliminate the adverse effects caused by inconsistent.In this thesis, we focus on three aspects: the design of balanced circuit structure, the prediction and estimation of lithium battery SOC and the control strategy. This paper proposes a LC circuit as the core of the battery equalization scheme, and the circuit parameters are designed. The scheme is to balance the inductor current balancing current for oblique wave current can be adjusted continuously, only control the duty cycle to control the ramp current size, can effectively realize the transfer of energy.SOC as variables, but also can provide a balanced range reference information for the estimation of electric vehicles, lithium battery SOC,based on Kalman filter, and combined with the current time integral method and combined method of open circuit voltage method to estimate the open circuit voltage method can eliminate the current integral error on time. Kalman filtering of the batteries of the complex system has good adaptability, improve the precision of estimation. The first pair of control method of equalization in balance control, the relationship between range and threshold of each single battery SOC lithium battery in the group as an equilibrium criterion of matching equilibrium, duty ratio and equilibrium time determines the equilibrium current and the transfer of power, in order to improve the system stability, fuzzy control strategy adjust the balance of the duty ratio and equilibrium time, improve the efficiency of equalization.Equalization and equalization scheme to validate the proposed control strategy, this paper built the hardware and software of the system,the equilibrium experiments were performed respectively in charge and discharge, the experimental results show that the proposed balanced control system can effectively eliminate lithium battery inconsistency,reach to balance.