Dual-Layer Inductor Active Equalization Control for Series-Connected Lithium-Ion Batteries Based on SOC Estimation
Round 1
Reviewer 1 Report
The authors mainly discuss about active balancing control scheme for the double-layer inductance of the series battery pack based on the state of charge prediction. The authors claim that the control scheme can provide insights on solving the long time and slow balancing speed of double-layer inductors. The 188 NCR18650B cell is measured with the ITS5300 battery testing system. SOC is selected as the equilibrium evaluation index and combined PF algorithm. A relatively small error of 4% is verified by urban dynamometer driving schedule (UDDS) conditions. This equalization control is proposed to reduce the equalization time of 15.6%. Overall, I recommend this manuscript to be published as it is.
Author Response
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Reviewer 2 Report
The manuscript is well motivated, explained and implemented using MATLAB/Simulink.I have only minor questions: 1) line 77: Ref [26] considers similar equalization method which could be applied ... when the number of batteries is even. However, it seems that the method considerd in this manuscript also implements only even numbers of cells. (Figs 1-4, 9, 11-13). Please, explain/discuss. 2) There is no explanation on how the key parameters of the balancing circuitry L11(1H) and R11(10 kOhm) were derived. Are these parameters optimal, or further enhancements could be expected, for example L11=3H, R11=5 kOhm? Please, explain. 3) The label Inductance module in Figure 9 is partially covered by the label D12. Please, fix.
Author Response
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Reviewer 3 Report
The authors proposed a double-layer inductance active equalization scheme to improve the battery equalization performance. The proposed method looks reasonable and the experimental results demonstrates good performance of the proposed method. However, there exist the following several problems in the paper, which reduces the paper quality.
- The paper motivation in the introduction part is not strong. The authors list existing battery equalization methods and their disadvantages, which are good. However, the authors did not compare their proposed method and existing works to show the advantages of the proposed method clearly. Besides, the authors mentioned that “In Ref. [26] the battery equalization and coupled inductance were combined to effectively reduce energy loss, but this equalization method was only applicable when the number of batteries was even”. Is the number of batteries in a battery pack is often even in practice? Is the requirement on the number of batteries important for electric vehicle battery packs? If not, Ref.[26] will be a good choice for battery equalization. The authors need to explain this clearly.
- In section 2.3, the authors proposed to apply PF to estimate single battery SOC. However, there already exist many PF-based SOC estimation methods. This part should not be the main contribution of this paper and the authors need to make this clear. Please see the following PF-based estimation methods:
[1] Xia, Bizhong, et al. "A comparative study of three improved algorithms based on particle filter algorithms in soc estimation of lithium ion batteries." Energies 10.8 (2017): 1149.
[2] Tulsyan, Aditya, et al. "State-of-charge estimation in lithium-ion batteries: A particle filter approach." Journal of Power Sources 331 (2016): 208-223.
[3] Wang, Yujie, Chenbin Zhang, and Zonghai Chen. "A method for state-of-charge estimation of LiFePO4 batteries at dynamic currents and temperatures using particle filter." Journal of power sources 279 (2015): 306-311.
- The proposed active balancing control strategy controls the opening and closing of the MOSFET based on battery SOC values. Therefore, SOC estimation accuracy highly affects the method’s balancing performance. However, battery working conditions like dynamic battery temperatures and aging propagation highly affect SOC estimation results and it is difficult for the PF method to estimate SOC accurately under such situations, which makes their method less convincing.
Author Response
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Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
Thanks for the authors' response and they have solved the first two comments well. However, they did not solve the third comment well! The authors may add some experimental results to show how the proposed method's performance changes for situations with different SOC estimation error levels.
Author Response
Dear Editors and Reviewer,
We would like to give great thanks to you and the anonymous reviewers for the valuable suggestions. We have provided a response to the reviewer's comments, please see the attachment.
Author Response File: Author Response.pdf
Round 3
Reviewer 3 Report
The authors have solved my comments well and I do not have other comments.
