Active Equalization Strategy for Lithium-Ion Battery Packs Based on Multilayer Dual Interleaved Inductor Circuits in Electric Vehicles

Abstract

Lithium-ion batteries (LIBs) are widely used in electric vehicles (EVs) due to their superior power performance over other batteries. However, when connected in series, overcharged cells of LIBs face the risk of explosion, and undercharged cells decrease the life cycle of the battery. Eventually, the inconsistency phenomenon between cells resulting from manufacturing tolerance and usage process reduces the overall charging capacity of the battery and increases the risk of explosion after long-time use. Research has focused on synthesizing active material to achieve higher energy density and extended life cycle for LIBs while neglecting a comparative analysis of equalization technology on the performance of battery packs. In this paper, a nondissipative equalization structure is proposed to reconcile the inconsistency of series-connected LIB cells. In this structure, a circuit uses high-level equalization units to enable direct energy transfer between any two individual cells, and dual interleaved inductors in each equalization unit increase the equalization speed of a single cell in one equalization cycle by a factor of two. The circuit is compared with the classical inductor equalization circuit (CIEC), dual interleaved equalization circuit (DIEC), and parallel architecture equalization circuit (PAEC) in the states of standing, charging, and discharging, respectively, to validate the advantages of the proposed scheme. Considering the diversity of imbalance states, the state of charge (SOC) and terminal voltage are both chosen as the equalization criterion. The second-order RC model of the LIB and the adaptive unscented Kalman filter (AUKF) algorithm are employed for SOC estimation. For effective equalization, the adaptive fuzzy neural network (AFNN) is utilized to further reduce energy consumption and equalization time. The experiment results show that the AFNN algorithm reduces the total equalization time by approximately 37.4% and improves equalization efficiency by about 4.89% in contrast with the conventional mean-difference algorithm. Particularly, the experiment results of the equalization circuit verification certify that the proposed equalization structure can greatly accelerate the equalization progress and reduce the equalization loss compared to the other three equalization circuits.

Revolutionizing mobility: a comprehensive review of electric vehicles charging stations in India

“…However, they may explode when overcharged and may have a considerably reduced battery life when undercharged. The resulting inconsistency caused by manufacturing issues and usage causes a reduced overall charging capacity (Balacco et al, 2021;Lei et al, 2022). Regardless of many limitations, there are numerous benefits of EVs over traditional ICE vehicles as depicted in Figure 1.…”

A Battery Cell Equalisation System Based on a Supercapacitors Tank and DC–DC Converters for Automotive Applications

“…The battery cell equalisation techniques have been an object of research in numerous studies in recent years [1][2][3][4][5][6]. The review of the primary equalisation circuits in [1] presents and compares capacitive and inductive energy storage, single and multi-tube flyback, and different DC-DC converter topologies.…”

“…As the study concludes, further improvements to the battery cell equalisation system must be focused on circuit design, giving a reliable system; flexibility improvement, leading to easy expansion on a large scale; and overall efficiency increase. A widely used circuit for equalisation is inductor-based, presented in better detail in [2,3], which usually requires a significant number of inductors and completes the energy transfer between adjacent cells only. A review and comparison study [2] of the inductor-based topologies suggests universal control equalisation algorithms.…”

Investigation of active cell balancing performance for series connected lithium‐ion cells in electric vehicle applications

“…Lei et al. in [25] proposes a non‐dissipative equalization method to balance the cell charging and discharging. An In‐cell thermal monitoring to study the temperature profile is proposed in [26].…”

“…A comprehensive review of the active and passive cell balancing is explained in paper [24]. Lei et al in [25] proposes a non-dissipative equalization method to balance the cell charging and discharging. An In-cell thermal monitoring to study the temperature profile is proposed in [26].…”