Simultaneous Thermal and State-of-Charge Balancing of Batteries: A Review

Altaf, Faisal; Johannesson, Lars; Egardt, Bo

doi:10.1109/vppc.2014.7007132

Cited by 26 publications

(23 citation statements)

References 28 publications

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“…A similar kind of conceptual study has also been carried out recently by other authors [20]. Thermal and SOC balancing are two tightly coupled and somewhat conflicting objectives, but it is possible to achieve both simultaneously in an average sense [8]. For this, load variations and surplus voltage in the battery pack are required.…”

Section: Introductionmentioning

confidence: 88%

“…Another serious issue is that the cell imbalance and nonuniform ageing are tightly coupled, which may lead to a vicious cycle resulting in the premature end of battery life. In addition to nonuniform ageing, the SOC imbalance also has a detrimental impact on the total usable capacity of the battery, see review papers [7] and [8] for details. Therefore, thermal and SOC imbalance can be considered as an indirect indication of either temporary or permanent health imbalance among cells.…”

Section: Introductionmentioning

confidence: 99%

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Load Management of Modular Battery Using Model Predictive Control: Thermal and State-of-Charge Balancing

Altaf

Egardt

Mårdh

2017

IEEE Trans. Contr. Syst. Technol.

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Thermal and state-of-charge (SOC) imbalance is well known to cause non-uniform ageing in batteries. This paper presents the electro-thermal control of a multi-level converter (MLC) based modular battery to address this issue. The modular battery provides a large redundancy in synthesizing terminal voltage, which gives extra degrees-of-freedom in control on cell level. There are multiple tightly coupled control objectives including the simultaneous thermal and SOC balancing as well as battery terminal voltage control. The main purpose of this paper is to devise an electro-thermal control scheme for cases where full future driving information is not accessible. The control scheme is based on decomposition of controller into two orthogonal components, one for voltage control and the other for balancing control. This problem decomposition enables the application of constrained linear quadratic model predictive control scheme to solve the balancing problem elegantly. The control scheme is thoroughly evaluated through simulations of a four cell modular battery. The results show that a rather short prediction horizon is sufficient to achieve robust control performance.

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Section: Introductionmentioning

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Load Management of Modular Battery Using Model Predictive Control: Thermal and State-of-Charge Balancing

Altaf

Egardt

Mårdh

2017

IEEE Trans. Contr. Syst. Technol.

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“…Researches on battery balancing mainly include balancing methods [4,5,6,7,8], strategies [9,10,11,12] and control algorithms [13,14,15,16]. Related reviews can be found in [17,18,19].…”

Section: Introductionmentioning

confidence: 99%

A highly-integrated and efficient commercial distributed EV battery balancing system

Chen

Jun

Zheng

et al. 2018

IEICE Electron. Express

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This paper focuses on the imbalance problem of serial cells in lithium-ion batteries applied in electric vehicles (EVs). In order to meet more strict requirements of size, efficiency, cost, and reliability in commercial application, a highly-integrated and efficient distributed battery balancing system is developed. In the system, each balancing node (BN) and its controller, a designed specific integrated circuit (IC), are independent, distributed and integrated in an IC-packaged module. Besides, a 50% stateof-charge (SOC)-aligned balancing strategy is proposed and applied. The experiment and commercial application results show the designed balancing system performs excellently in improving battery capacity and extending cycle life.

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“…Another serious issue is that the cell imbalance and nonuniform ageing are tightly coupled, which may lead to a vicious cycle resulting in the premature end of battery life. In addition to nonuniform ageing, the SOC imbalance also has a detrimental impact on the total usable capacity of the battery [5], [6]. It is also worth mentioning that thermal, SOC, and DOD imbalance is inevitable in battery packs of xEVs due to variations in cell parameters and operating conditions, see [7] and [8].…”

mentioning

confidence: 99%

“…A similar kind of conceptual study has also been carried out in [15]. Thermal and SOC balancing are two tightly coupled and somewhat conflicting objectives, but it is possible to achieve both simultaneously in an average sense [6]. For this, load variations and surplus voltage in the battery pack are required.…”

mentioning

confidence: 99%

Comparative Analysis of Unipolar and Bipolar Control of Modular Battery for Thermal and State-of-Charge Balancing

Altaf

Egardt

2017

IEEE Trans. Veh. Technol.

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Thermal and state-of-charge imbalance is a well known issue to cause nonuniform ageing in batteries. The modular battery based on cascaded converters is a potential solution to this problem. This paper presents bipolar control (BPC) of a modular battery and compares it with previously proposed unipolar control (UPC) mode in terms of thermal/SOC balancing performance and energy efficiency. The BPC needs four-quadrant operation of full-bridge converter using bipolar pulse-width modulation (PWM) inside each module, whereas UPC only needs half-bridge converter with unipolar PWM. The BPC, unlike UPC, enables charging of some cells while discharging others. An averaged state-space electro-thermal battery model is derived for a convex formulation of the balancing control problem. The control problem is formulated on a constrained LQ form and solved in a model predictive control framework using one-step ahead prediction. The simulation results show that BPC, without even requiring load current variations, gives better balancing performance than UPC, but at the cost of reduced efficiency. The UPC requires at least current direction reversal for acceptable balancing performance. In short, the UPC is a more cost and energy efficient solution for EV and PHEV applications whereas the BPC can be beneficial in applications involving load cycles with high current pulses of long duration. Index Terms-Modular battery, SOC balancing, thermal balancing, multilevel converters, averaging, model predictive control. I. INTRODUCTION The electrification and hybridization of vehicle powertrain is being vastly adopted by automotive industry to increase fuel efficiency and to meet ever decreasing exhaust emission limits. The Lithium-ion battery is one of the major alternative power sources currently being considered for this purpose. The battery pack of these electrified/hybridized vehicles (xEVs) is one of the most expensive, but a key component in the powertrain. Therefore, the battery lifetime is an important factor for the success of xEVs. The conventional battery system in xEVs consists of long string of series connected modules along with dc/dc converter for dc-link voltage regulation as shown in Fig. 1. Due to the fixed series connection, the same current passes through all the modules. This is a socalled uniform duty operation (UDO) of cells. If modules have nonuniform state-of-health (parametric variations) then they may suffer from unequal stress and energy drain under

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Simultaneous Thermal and State-of-Charge Balancing of Batteries: A Review

Cited by 26 publications

References 28 publications

Load Management of Modular Battery Using Model Predictive Control: Thermal and State-of-Charge Balancing

Load Management of Modular Battery Using Model Predictive Control: Thermal and State-of-Charge Balancing

A highly-integrated and efficient commercial distributed EV battery balancing system

Comparative Analysis of Unipolar and Bipolar Control of Modular Battery for Thermal and State-of-Charge Balancing

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