Research on multi-path balancing topology based on transformers

doi:10.3969/j.issn.2097-0706.2024.04.009

Abstract

Abstract:

With the upgrade of the voltage level and power level of energy storage systems，the number of cells in a series-connected battery pack increases，making the imbalance between battery packs more complex. Therefore，a transformer-based direct equalization topology for multi-path series-connected battery packs is proposed. The topology，which uses a transformer as the energy transfer carrier，is able to switch between Buck-Boost mode and flyback mode. By controlling a low-conduction bi-directional switching array， the topology structure can achieve equalization between any battery cells. This topology is of multiple equalization modes，flexible equalization paths and fast equalization speed. In order to distribute energy effectively and achieve equalization efficiently，a fuzzy control strategy with State of Charge（SOC）as its equalization index is designed. Finally，a series of simulation experiments are carried out to verify the effectiveness of the proposed topology and its control strategy under different working conditions. The results show that the proposed balancing topology and control strategy have good effects in overcoming the inconsistency between single cells in a battery pack. This study is of great significance for improving the capacity difference between the battery cells， the capacity utilization rate of the energy storage system and the service life of the battery pack.

Key words: active balancing, balancing topology, transformer, fuzzy control, multi-path of energy transmission

CLC Number:

TM912

CHEN Yang, WENG Weijie, HUANG Jiangdong, ZOU Tao, JIANG Wei. Research on multi-path balancing topology based on transformers[J]. Integrated Intelligent Energy, 2024, 46(4): 68-77.

Figures/Tables 18

Fig.1

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Table 1

Fuzzy rule base

$Δ S O C$ $i e q$ $S - O C$	SS	S	M	B	BB
SS	SS	SS	S	M	B
S	SS	S	M	B	BB
M	S	M	B	BB	BB
B	S	M	B	BB	BB
BB	SS	S	M	B	BB

Table 1

Fig.6

Fig.7

Table 2

Table 3

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Table 4

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Fig.11

Fig.12

Table 5

Table 6

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参数	值
电池容量/（A·h）	1.5
电池标定电压/V	3.7
变压器变比	1∶1
励磁电感/μH	150
开关频率/kHz	20
充电电流/A	0.5
放电电流/A	0.5
仿真步长/s	5e^-7

均衡模式	初始值
均衡模式	S_OC1	S_OC2	S_OC3	S_OC4
单体对单体	90.00	88.60	88.61	88.00
单体对单体组	90.00	88.55	88.57	88.59
单体组对单体	90.00	90.02	90.04	86.00
单体组对单体组	90.00	90.02	88.25	88.23

均衡模式	均衡对象	占空比	平均均衡电流/A	均衡时间/s	均衡效率/%
单体对单体	B₁—B₄	0.558 3	0.322	224	90.69
单体对单体组	B₁—B₂B₃B₄	0.785 8	0.677	128	89.52
单体组对单体	B₁B₂B₃—B₄	0.315 4	0.699	319	88.91
单体组对单体组	B₁B₂—B₃B₄	0.596 8	0.829	118	90.47

方法	工作状态	均衡后平均S_OC/%	均衡时间/s
均值差值法	静置	80.11	1 069.22
	充电	90.05	1 102.53
	放电	71.06	1 097.36
模糊控制策略	静置	80.25	509.25
	充电	84.93	525.10
	放电	75.98	451.64

均衡拓扑	电容型	变压器型	传统电感型	单电感型	改进变压器型
开关数量	多	少	较少	多	较多
均衡路径	单体对单体	单体与电池组	灵活多样	灵活多样	灵活多样
控制难度	容易	容易	复杂	复杂	复杂
均衡速度	慢	快	中等	快	快
均衡效率	低	中等	中等	较高	高