This article proposes an active balancer, which features bidirectional charge shuttling and adaptive equalization current control, to fast counterbalance the state of charge (SOC) of cells in a lithium-ion battery (LIB) string. The power circuit consists of certain bidirectional buck-boost converters to transfer energy among the different cells back and forth. Owing to the characterization of the open-circuit voltage (OCV) vs SOC in LIB being relatively smooth near the SOC middle range, the SOC-inspected balance strategy can achieve more precise and efficient equilibrium than the voltage-based control. Accordingly, a compensated OCV-based SOC estimation is put forward to take into account the discrepancy of SOC estimation. Besides, the varied-duty-cycle (VDC) and curve-fitting modulation (CFM) methods are devised herein to tackle the problems of slow equalization rate and low balance efficacy, which arise from the diminution in balancing current as the SOC difference between the cells decreases in the later duration of equalization especially. The proposed strategies have taken the battery nonlinear characteristic and circuit parameter nonideality into account and can adaptively modulate the duty cycle with the SOC difference to keep balancing current constant throughout the balancing cycle. Simulated and experimental results are given to demonstrate the feasibility and effectiveness of the same prototype constructed. Compared with the fixed duty cycle and the VDC methods, the proposed CFM has the best balancing efficiency of 81.4%, and the balance time is shortened by 27.1% and 18.6%, respectively.

中文翻译：

---

一种具有快速双向充电穿梭和自适应均衡电流控制的锂离子电池组主动平衡器

本文提出了一种具有双向电荷穿梭和自适应均衡电流控制功能的主动平衡器，以快速平衡锂离子电池 (LIB) 串中电池的荷电状态 (SOC)。电源电路由一定的双向升降压转换器组成，用于在不同的电池之间来回传输能量。由于 LIB 中开路电压 (OCV) 与 SOC 的特性在 SOC 中间范围附近相对平滑，因此 SOC 检查平衡策略可以实现比基于电压的控制更精确和有效的平衡。因此，考虑到SOC估计的差异，提出了基于补偿的OCV的SOC估计。除了，此处设计了变占空比 (VDC) 和曲线拟合调制 (CFM) 方法来解决均衡速率慢和平衡效率低的问题，这些问题是由于电池之间的 SOC 差异减小而导致平衡电流减小而引起的特别是在均衡的后期。所提出的策略考虑了电池的非线性特性和电路参数的非理想性，可以根据 SOC 差异自适应地调制占空比，以在整个平衡周期内保持平衡电流恒定。仿真和实验结果证明了所构建的相同原型的可行性和有效性。与固定占空比和VDC方法相比，所提出的CFM具有81.4%的最佳平衡效率，平衡时间缩短了27。