Research On Equalization Circuit And Energy Loss For Lithium Battery Pack In Electric Vehicle

Equalization is an important technology in the application of electric vehicles. The capacity utilization and cycle life of batteries after grouping is far less than a single cell because of the single inconsistency. The equalization is one of the effective ways to solve the problem and has important practical significance. At present, equalization circuit and control strategy has become a research focus. This thesis will intensive research on it.Firstly, this thesis introduces the performance parameters of the battery and the charge and discharge characteristics under different conditions.Then introduced several kinds of battery model which commonly used and made a deep analysis of the circuit model used in this paper. The cause of inconsistency, the impact of inconsistency and the way to solve this problem was discussed in the thesis.Secondly, A balanced circuit combining the distributed-load balancing and the central-load balancing is designed to improve the balancing speed to a large extent in this thesis,then this thesis made an analysis about advatages and disadvantages of the electric circuit. The balanced process of equalization circuit is described in detail,in addition,two kinds of equalization circuit were made comparison of it to highlight its advantages and practicability.Thirdly, the control mode that made voltage as the judgement stangard was imnproved in this thesis. Then, it made the balance order as the breakthrough point to analyze the energy loss in the process of equilibrium.At last, an equilibrium control strategy based transferring least energy was put forward by depth-first search algorithm.Finally, this thesis validates the balanced circuit and equalization strategy through simulation and experiment, primarily,the article evaluates the system about balancing efficiency and the energy loss.The equalization circuit proved to be correct and can improve the balancing speed to a large extent by experiment. Moreover,the equilibrium strategy proved to reduce the loss of energy and improve energy utilization.