Design and Simulation of a Bidirectional Flyback-Based Active Balancing Topology for Lithium-Ion Battery Packs

Demands driven by Lithium-Ion Batteries (LIBs) in electric vehicles, renewable energy storage and portable electronics has expanded the requirement of balance strategies to scale high-performance energy storage systems that are both efficient and scalable to address cell-to-cell variations that result in loss of performance and shortened life. This paper demonstrates the topology and simulation of a dual layer hybrid active balanc-ing architecture that combines a Buck-Boost multi-inductor design with a bi-directional flyback topology to allow not only fast adjacent-cell balancing, but also direct cross-cell energy transfer. Working in Discontinuous Conduction Mode (DCM) to avoid inductor saturation and maximize the voltage and energy conversion effi-ciency, the proposed system was simulated and analyzed (under conditions of resting, charging and discharging) in MATLAB/Simulink with a six-cell 3.2 V, 6 Ah lithium-ion pack as an example. To evaluate balancing the performance, three control strategies, namely, voltage-only, State-of-Charge (SOC)-only, and segmented bi-variable, were applied. Simulation findings show that the hybrid topology improved the time taken in balancing by 63.2-64.8 compared with traditional one-inductor designs, and the point is supportable through completion in 303-308 s through all the states of operation. SOC-only control was the most effective and it further reduced balancing time by up to 55.9% as compared to the segmented control. The results demonstrate the promise of the hybrid system to improve energy use and voltage stability and increase overall battery pack efficiency, electric mobility, distributed energy storage and aerospace markets. Currently under development is hardware prototyping, ther-mal-characterization, and scalability testing of large-format battery arrays.