Battery management, particularly the balancing of state of charge (SOC) among various cells or groups, is crucial for optimal performance. Traditional methods often present challenges in terms of efficiency, cost, and complexity. Li et al. (2023) explored the active equalization of lithium-ion batteries using a reconfigurable topology in their study.
✔️Inner Layer Equalization: Emphasis on Individual Cells:
The inner layer primarily focuses on achieving balance among cells within the same group. Traditional methods usually involve many components, leading to high costs and complex controls. In contrast, the new approach leverages reconfigurable topology to minimize these drawbacks. In essence, cells with higher SOCs discharge first, while those with lower SOCs are initially isolated. Over time, isolated cells are reintegrated, resulting in all cells being connected serially upon completion of the equalization process. The advantage? Fewer components, reduced cost, enhanced efficiency, and simplified control.
For example, in a battery group with four cells, cells with a higher SOC start discharging first. Cell 4, having the lowest SOC, begins isolated. As equalization progresses, it balances out and starts discharging. This process ensures that each cell reaches equilibrium, and by the end, all cells discharge at a unified rate.
✔️Outer Layer Equalization: A Group Perspective:
The outer layer’s primary focus is to equalize among different battery groups, ensuring that all groups are balanced at the same time. The key to this process is the setting of power coefficients. These coefficients dictate the discharge power for each battery group, ensuring that those with a higher initial SOC discharge faster than their counterparts.
For a practical illustration, consider three battery groups with varying initial average SOCs. By strategically setting power coefficients (based on an established formula that relates the differences in SOCs), it's possible to equalize these groups effectively. The final objective is to have all groups discharge at the same power, ensuring system efficiency and longevity.
✔️Simulation Results and Insights:
Real-world simulations by Li et al. affirm the efficacy of this dual-layer approach. Battery groups with higher output power achieve balance faster than those with lower output power. Moreover, when equalization completes, all groups and cells connect to the circuit, optimizing system output.
This technique introduces a better way to address battery equalization challenges. By focusing on both individual cells and group dynamics, it promises enhanced efficiency, reduced costs, and simplified controls. It's an approach well-suited for high-power, large-capacity battery systems that demand robust balancing solutions.
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