Abstract
Lithium-ion batteries play an important role in large-scale energy storage systems. However, the power inconsistency of the battery packs restricts the developments of modern technologies in energy storage area. The motivation of the present study is to serve the growing needs of the energy balance for lithium-ion battery packs. The present study proposes a flexible multiphase interleaved converter for the energy equalization of a lithium battery pack with series configuration. Moreover, the graph theory is applied to the analysis of equalization circuits. It is intended to establish a unified standard for the comparison. The parameter of average efficiency is considered as an important indicator to evaluate the characteristics of the equilibrium system. The proposed method is verified by constructing a lithium-ion battery pack with the equalization circuit. It is observed that the proposed multiphase interleaved converter has flexible characteristics, while it has low energy loss compared with the conventional methods. It is found that the proposed method simplifies the complex equalization circuits into graphs and facilitates the comparison of the average efficiency of the system. It is concluded that this method is a feasible and powerful method for evaluating the battery equalization circuit. This approach can be applied for solving complex problems in other engineering applications.
Highlights
Battery management system is commonly known as battery steward, mainly for intelligent management and maintenance of each battery unit, preventing the battery from overcharging and overdischarging, extending the service life of the battery, and monitoring the state of the battery.erefore, functional safety design of BMS is very important for the safety of the battery energy storage system
Compared with other electrochemical energy storage technologies, lithium-ion batteries have the largest cumulative installed capacity, accounting for 86.3% of electrochemical energy storage globally. erefore, the present study focuses on the energy balance problem of lithium battery stacks, which limits the available capacity and cycle life of packs
Considering the energy flow process, the graph theory is used to simplify the analysis of the circuit and to optimize the path
Summary
Battery management system is commonly known as battery steward, mainly for intelligent management and maintenance of each battery unit, preventing the battery from overcharging and overdischarging, extending the service life of the battery, and monitoring the state of the battery. Erefore, the present study focuses on the energy balance problem of lithium battery stacks, which limits the available capacity and cycle life of packs. Daowd et al [12] showed that passive equalizations dissipate the excess energy of the highest voltage battery cell by discharging the cell through a resistor. Mainstream active equalization circuits can be divided into four types as the following: cell bypass, cell-to-cell, cell-to-pack, and hybrid balancing topology. Cell bypass circuits are divided into the complete shunting [15, 16] and shunt resistor [17, 18] balancing methods, which achieve equalization by continuous switchings between the normal and bypassed operation for overcharged cells.
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