锂离子电池组充放电均衡器及均衡策略

The Equalizer of Charging and Discharging and the Balancing Strategies for Lithium-Ion Battery Pack

提出了一种基于Buck斩波电路和Boost-Buck斩波电路的锂离子电池组充放电均衡器。根据电池组的两种工作状态,采取两种不同的均衡策略:电池组处于充电状态时,电池组中荷电状态最高的强单体电池被均衡放电,强单体电池的充电电流减小,而同组中的其他单体电池不受影响;电池组处于放电或静置状态时,电池组中最弱的单体电池被均衡充电,而同组中的其他单体电池不受影响。均衡器具有均衡电路控制简单、易实现,被均衡的单体电池任意可选、均衡能量可双向传输、均衡电流易控等优点。详细阐述了两种均衡控制策略的工作原理,并采用此均衡器对串联的四个磷酸铁锂电池进行了充放电均衡实验,实验结果证明了此均衡器不仅改善了单体电池间不均衡程度,同时提高了电池组的充电容量和放电容量。

The charging and discharging equalizer based on the buck and boost-buck chopper circuits for lithium-ion battery pack is suggested in this paper. Two different balancing strategies are used respectively according to the different battery states. The strongest battery cell with the highest state of charge(SOC) is discharged by the equalizer in the battery charging state, its charging current is lower and the rest cells of the same pack are not affected. The weakest battery cell is charged by the equalizer in the battery discharging or static state, and the rest cells are not affected. The advantages of the equalizer are as follows: 1. it is simple to control the balancing circuit and easy to be realized; 2. the balanced battery cell is selectable and the balancing energy is bidirectional; 3. the balancing current is controllable. The working principle of the two balancing strategies has been described in this paper.The balancing experiment has been completed to four serially connected Li Fe PO4 battery cells, and the experimental results confirm that the unbalanced degree of the four battery cells has been improved,moreover the charging and discharging capacity of the battery pack have been increased.