This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Bi-Directional Equalization System for Li-Ion Battery Pack Based on Fly-back Transformer
Technical Paper
2018-01-0442
ISSN: 0148-7191, e-ISSN: 2688-3627
Annotation ability available
Sector:
Language:
English
Abstract
For balancing Li-ion battery cells connected in series and effectively improving the consistency of the cells, a bi-directional equalization system based on fly-back transformer is proposed. Unlike the passive equalization technology using a resistor or active equalization with expensive DC-DC converter for the balancing among the cells, this equalization circuit consists of the fly-back transformer and RCD circuit, which can easily and cheaply realize the energy transfer between the whole battery module and the cells, and thus achieving bidirectional equalization. In this system, both the primary side and the secondary side of multi-winding transformer are connected to a MOSFET. All MOSFETs are controlled by the PWM signal. The control timing and duty ratio of the PWM control signal are determined through the simulation analysis. Meanwhile, an RCD circuit is applied at the primary side of multi-winding transformer for buffering the peak voltage caused by leakage inductance. In the control process, the equalization strategy is proposed by considering the voltage, SOC and capacity difference simultaneously, and in order to avoid the equalization control logic chaos, only one battery cell is balanced at the same time. The equalization strategy is verified by MATLAB/Simulink and has a satisfactory performance. To verify the effectivity of the proposed circuit, a prototype for six series-connected 18650 NCM lithium battery cells is implemented, and the experimental results show that the equalization system has good circuit performance and the efficiency is more than 80%. This proposed method also has potential to balance the state of health of cells in the long term.
Recommended Content
Authors
Citation
Wang, Y., Wei, X., Fang, Q., and Zheng, B., "Bi-Directional Equalization System for Li-Ion Battery Pack Based on Fly-back Transformer," SAE Technical Paper 2018-01-0442, 2018, https://doi.org/10.4271/2018-01-0442.Also In
References
- Cao J. , Schofield N. , Emadi A. Battery Balancing Methods: A Comprehensive Review Vehicle Power and Propulsion Conference China 3-5 September 2008
- Mohamed , D. , Noshin , O. , Peter , V. , and Joeri , V. A Review of Passive and Active Battery Balancing Based on MATLAB/Simulink International Review of Electrical Engineering 6 7 2974 2989 2011
- Moo , C.S. , Yao , C.H. , and Tsai , I.S. Charge Equalization for Series-Connected Batteries Aerospace & Electronic Systems IEEE Transactions On 39 2 704 710 2003
- Anderson , R. , Zane , R. , Plett , G. , Maksimovic , D. et al. Life Balancing - A Better Way to Balance Large Batteries SAE Technical Paper 2017-01-1210 2017 10.4271/2017-01-1210
- Cui , X. , Shen , W. , Zhang , Y. , Hu , C. et al. Novel Active LiFePO4, Battery Balancing Method Based on Chargeable and Dischargeable Capacity Computers & Chemical Engineering 97 27 35 2017
- Maharjan , L. , Inoue , S. , Akagi , H. , and Asakura , J. State-of-Charge (SOC)-Balancing Control of a Battery Energy Storage System Based on a Cascade PWM Converter IEEE Transactions on Power Electronics 24 6 1628 1636 2009
- Schuster , S.F. , Brand , M.J. , Berg , P. , Gleissenberger , M. et al. Lithium-ion Cell-to-Cell Variation during Battery Electric Vehicle Operation Journal of Power Sources 297 242 251 2015