Research progress on fre protection technology of LFP lithium-ion battery used in energy storage power station

随着电化学储能市场的蓬勃发展,电化学储能电池本身的安全性越来越受到关注,如何最大程度地降低储能电池组火灾风险是电化学储能大规模应用时亟需解决的问题。本文综述目前国内外针对锂离子电池热失控已有的研究成果,包括磷酸铁锂电池的燃烧特性、火灾危险等级以及在储能电站预警系统中应用的锂离子电池热失控及热扩散参数;梳理不同灭火剂对电池火灾的灭火效率;同时总结电化学储能电站的灭火系统选择,为电网储能工程应用提供参考,有效支持锂离子储能电池的大规模工程需求。     

Dynamic time warping and multidimensional scaling approach based abnormal battery visual recognition for series-connected lithium-ion batteries pack

精确、可靠地识别异常电池是保障电池系统安全、稳定运行的有效手段。但是,从实时测量得到的电流、电压和温度有限外部信息,推断内阻、容量等电池内部信息,并识别异常电池难度很大。本工作针对串联锂离子电池组,基于各单体电压测量数据,提出了一种融合动态时间规整和多维标度策略的异常电池识别方法。通过采用动态时间规整策略,计算动态时间规整距离相似性指标,以消除电池组中荷电状态不一致的影响;进而结合多维标度法提取异常特征参数,实现异常电池可视化识别。通过电池系统仿真实验,验证了所提方法的有效性,为异常电池在线识别提供了一种有效技术。     

Analysis and design of multilayer multiphase interleaved converter for battery pack equalization based on graph theory

Lithium-ion batteries play an important role in large-scale energy storage systems. However, the power inconsistency of the battery packs restricts the developments of modern technologies in energy storage area. The motivation of the present study is to serve the growing needs of the energy balance for lithium-ion battery packs. The present study proposes a flexible multiphase interleaved converter for the energy equalization of a lithium battery pack with series configuration. Moreover, the graph theory is applied to the analysis of equalization circuits. It is intended to establish a unified standard for the comparison. The parameter of average efficiency is considered as an important indicator to evaluate the performance of the equilibrium system. This mentioned method is verified by constructing a lithium-ion battery pack with the equalization circuit. It is observed that the proposed multiphase interleaved converter has flexible characteristics, while it has low energy loss compared with the conventional methods. The proposed method simplifies the complex equalization circuits into graphs and facilitates the comparison of the average efficiency of the system. It is concluded that this method is a feasible and powerful for evaluating the battery equalization circuit. This approach can be applied for solving complex problems in other engineering applications.     

The review of thermal management technology for large-scale lithium-ion battery energy storage system

大容量锂离子电池储能系统对完善传统电网和高效利用新能源都具有非常重要的作用。为了实现大容量锂离子电池储能系统的高倍率化、长寿命化以及高安全性,高性能电池热管理系统的研发刻不容缓。本文总结了温度对锂离子电池性能的影响规律,综述了空冷、液冷、热管冷却、相变冷却这4种典型热管理技术的研究概况,分析了热管理技术在锂离子电池储能系统中的应用与研究状况。随着锂离子电池储能系统工作倍率的提高,产热量随之增大,对热管理系统的要求也越来越高。下一步的研究工作应围绕空冷系统优化、基于新型冷却介质的液冷系统、经济型热管及多目标优化设计这4方面展开。     

Heat dissipation analysis and optimization of the pure electric bus lithium-ion battery pack based on CFD

针对某纯电动客车电池箱散热效果不佳的问题,本文基于CFD技术以该车的电池箱散热系统为研究对象,建立了估算锂离子电池生热速率数学模型,采用三维软件UG建立电池箱的几何模型,并利用软件Star-ccm+对该模型的速度场和温度场进行仿真和分析。通过添加导流板等措施,对电池箱的结构进行了优化改进,并进行了正交仿真实验,确定了电池箱导流散热的最优方案,结果表明,导流板能够降低电池箱内单体电池的最高温度,使电池组温度分布更加均匀。     

A comprehensive review on inconsistency and equalization technology of lithium-ion battery for electric vehicles

The rapid growth of transportation demand has been enlarged strongly which has promoted electric vehicles powered by lithium-ion batteries. However, the inconsistencies within the battery pack will deteriorate over the lifecycle and affect the performance of electric vehicles. Therefore, various thermal management systems and equalization systems have been applied in battery management system to deal with the inconsistencies, extend battery service life, and improve safety performance. This review summarizes the origination of inconsistency within lithium-ion batteries from production to usage process, and then introduces the classification methods and application scenarios of the balance management system in detail. Based on the circuit topology, equalization systems can be classified into passive and active topologies. Active topologies are widely researched due to the advantages of high equalization efficiency and high speed, and the state-of-art innovations are presented and compared from the prospective of circuit, energy flow, efficiency and system complexity. In addition, this review focuses on the mainstream equalization strategies based on the analysis of balancing variables and control algorithms in terms of efficiency, complexity and stability, especially in the areas of variables optimal selection and advanced control algorithms. It is expected that innovations such as cloud control methods and hybrid balancing systems equipped with thermal management will become the future direction of lithium-ion equalization technologies.     

Analysis of safety performance of lithium-ion power battery during life cycle based on non-destructive testing

基于在不同条件下对车用三元锂离子动力电池的充放电循环试验,分析电池寿命衰减程度及其影响因素。利用X-ray无损检测技术,测试以不同倍率大小电流进行充放电循环前后三元锂离子动力电池的内部结构变化,并评价了电池寿命衰减和安全失效程度,为研究电池寿命衰减及安全失效提供了新的方法。在充放电循环周期过程中,随着电池容量的不断衰减,基于无损检测技术可以获得电池内部结构出现越来越明显的缺陷,说明电池的寿命衰减速度越来越大,其安全性也越来越差。以不同倍率大小电流进行充放电循环后,将不同SOH状态下内部结构的断层扫描图像进行对比,发现车用三元锂离子动力电池的内部结构发生了不同程度的变化,说明与循环前相比电池的使用寿命有不同幅度的衰减。     

Effect of the formation temperature on lithium-ion battery performance

为缩短锂电池生产工艺时间、节约成本,高温压力化成受到工艺人员的关注,本文以钴酸锂-石墨体系的软包装锂离子电池为研究对象,研究了高温压力化成工艺中温度对化成效果的影响。在某一压力作用下,采用不同化成温度,分析了不同化成温度对应的实际化成时间、化成电压、电压降以及电池倍率放电与高温处理的性能,结果显示化成温度越高,化成时间越长;在不同的温度下化成,对电池的循环性能及倍率性能影响不同。     

Application of battery energy storage system to load frequency control of an isolated power system

A battery energy storage system (BES) can provide fast active power compensation and hence it also can be used to improve the performance of the load frequency control. In this paper, the study is carried out on a single area model representing the whole power system considering generation rate constraint (GRC). An incremental model of BES is proposed and merged into the load frequency control of the power system. Optimum value of integral gain setting is obtained using integral squared technique (ISE). Dynamic responses of the system are presented with and without considering BES facility. Analysis reveals that BES improves the system performance significantly. Copyright © 1999 John Wiley & Sons, Ltd.     

Patent technology development trend analysis of lithium-ion battery energy storage system

锂离子电池是目前最具发展前景的高效二次电池和发展最快的化学储能电源,已成为各国竞相竞争的技术热点。专利技术能够反映某一技术领域创新发展的现状和历程,已成为开展竞争情报的重要信息源。本文从专利角度出发,通过对锂离子电池储能系统领域专利的分析,发现和了解锂离子储能系统的发展态势,以期为我国政府与企业的战略决策提供参考与借鉴。     

Active cell balancing of lithium-ion battery pack based on average state of charge

Differences in the environment and parameters of lithium-ion battery (LiB) cells may lead the residual capacity between the battery cells to be inconsistent, and the battery cells may be damaged due to overcharging or overdischarging. In this study, an active balancing method for charging and discharging of LiB pack based on average state of charge (SOC) is proposed. Two different active balancing strategies are developed according to the different charging and discharging states of LiB pack. When the LiB pack is charging, charging balance strategy is performed, wherein the battery cells whose SOC is higher than the average SOC of the LiB pack are balanced to increase the charging capacity of the entire LiB pack. When the LiB pack is discharging or static standing, discharging balance strategy is performed, wherein the batter cells whose SOC is lower than the average SOC of the LiB pack are balanced to increase the discharging capacity of the entire LiB pack. The experimental results show that the proposed active balancing method can reduce the inconsistency of residual energy between the battery cells and improve the charging and discharging capacity of the LiB pack.     

Effects of reciprocating liquid flow battery thermal management system on thermal characteristics and uniformity of large lithium-ion battery pack

To investigate the thermal characteristics and uniformity of a lithium-ion battery (LIB) pack, a second-order Thevenin circuit model of single LIB was modeled and validated experimentally. A battery thermal management system (BTMS) with reciprocating liquid flow was established based on the validated equivalent circuit model. The effects of the reciprocation period, battery module coolant flow rate and ambient temperature on the temperature and the temperature imbalance of batteries were studied. The results illustrate that the temperature difference can be effectively reduced by 3°C when the reciprocating period is 590 seconds. The reciprocating coolant flow rate is 11.5% and 33.3% that of the unidirectional flow BTMS for cooling and heating when same thermal effects are to be achieved. Under the same ambient temperature condition, the maximum temperature and average temperature difference can be reduced by 1.67°C and 3.77°C, respectively, at best for the battery module investigated with a reciprocating liquid-flow cooling system. The average temperature difference and heating power consumption could be reduced by 1.2°C and 14 kJ for reciprocating liquid flow heating system with period of 295 seconds when compared with unidirectional flow. As a result, the thermal characteristics and temperature uniformity can be effectively improved, and the parasitic power consumption can be significantly reduced through adoption of a reciprocating liquid flow BTMS.     

Experimental analysis on the degradation behavior of overdischarged lithium-ion battery combined with the effect of high-temperature environment

A set of experiments are performed in the present work to investigate the degradation behavior of lithium-ion battery during overdischarge cycling, as well as the influence of a high-temperature environment on the degradation. Among, different discharge cut-off voltages (1.0, 0.5, and 0.2 V) are included. During the overdischarge process, batteries experience a stage where a violent electro-thermal behavior is exhibited, involving sharp decreases in the voltage and current, and a fierce increase in the surface temperature; moreover, several parameters such as the discharge capacity, energy density, and internal resistances are all increased after overdischarge. Besides, a poor rate capacity and serious capacity degradation can also be seen during the overdischarge cycling, which is further reflected by the evolution of battery surface temperature, charge/discharge voltage, and internal resistances. What is more, it is found that battery electro-thermal parameters, eg, temperature rise, degradation rate, and internal resistances, increase exponentially as overdischarge deepens. Finally, a high-temperature environment is verified to deteriorate the degradation of overdischarged battery.     

Comparative experimental study on combustion characteristics of typical combustible components for lithium-ion battery

In this paper, the cone calorimeter is used to investigate the combustion characteristics of typical combustible components for lithium-ion battery (LIB). The incomplete combustion of solvents, lithium salt, and separator results in the generation of residue. The melting of the separator at the early stage shows a more obvious endothermic reaction than the decomposition of LiPF₆ resulting in smaller peak heat release rate (HRR). The exothermic reaction of separator combustion increases the internal temperature and produces more heat; however, the sustained endothermic reaction of LiPF₆ decomposition leads to the opposite result. Due to the different boiling points, the single solvent has different quasi-steady-state combustion and boiling combustion time nodes. Different sizes of burn pans have little effects on HRR, but it has a significant impact on the mass loss rate (MLR) data. The average MLR ratio of the three solvents is close to that of the burn pan area. These tests could be the reference of more detailed analysis of the combustion mechanism of LIB and practical applications.     

Study on the low-cost flow battery technologies for energy storage

大规模储能技术是实现可再生能源并网和普及应用的核心技术,也是发展能源互联网、分布式发电、电力辅助调频、离网供电、安全备用电源等领域的关键使能技术。液流电池是一类新兴的大规模储能技术,经过近几年的快速发展,已经具备规模应用的竞争力。液流电池具备安全性好、单个循环储能时间长、功率/容量独立设计、储能容量大和寿命长等特点。目前液流电池成本偏高,高成本制约了液流电池储能技术大规模商业化应用。针对这一行业"痛点"问题,本文通过创新型的电池堆结构、新型关键材料和工艺研究,将液流电池堆功率密度提高2~4倍,实现电池堆的小型化,有效提高关键部件利用率,有望将液流电池系统成本降低20%~30%。     

Remaining useful life prediction of lithium-ion battery based on extended Kalman particle filter

Scientific estimation and prediction of the state of health (SOH) of lithium-ion battery, especially the remaining useful life (RUL), has important significance to guarantee the battery safety and reliability in the full life cycle to avoid catastrophic accidents as much as possible. In order to accurately predict the RUL of the lithium-ion battery, this paper firstly analyzes the problems of the standard particle filter (PF). Then, a novel extended Kalman particle filter (EKPF) is proposed, in which the extended Kalman filter (EKF) is used as the sampling density function to optimize PF algorithm. The life cycle tests are designed and carried out to get accurate and reliable data for the RUL prediction. And, the aging properties of lithium-ion battery are analyzed in detail. The RUL prediction is done based on the established capacity degradation model and the proposed EKPF method. Results show that the RUL prediction error of the proposed method is less than 5%, which has higher precision compared with the standard PF method and can be used both offline and online.     

Load‐frequency control of an interconnected hydro‐thermal power system with new area control error considering battery energy storage facility

This paper deals with load‐frequency control of an interconnected hydro‐thermal system considering battery energy storage (BES) system. A new area control error (ACEN) based on tie‐power deviation, frequency deviation, time error and inadvertent interchange (unscheduled energy transfer) is used for the control of the BES system. Time domain simulations are used to study the performance of the power system and the BES system. Results reveal that BES meets sudden requirements of real power load and is very effective in reducing the peak deviations of frequencies, tie‐power, time errors and inadvertent interchange accumulations. Copyright © 2000 John Wiley & Sons, Ltd.     

基于改进粒子群算法的火储联合调频优化储能控制策略研究

为了解决火储联合调频协同控制效果与储能系统成本回收的问题,提出一种改进粒子群算法的储能优化控制策略,通过引入自适应权重调整全局搜索方向,并解决储能电荷状态与出力状态的耦合性问题,建立火储联合调频综合性能指标进行储能控制策略研究。案例仿真结果表明：本文所提算法比传统算法在收敛效果方面具有明显优越性,避免了局部最优解问题;当储能系统电荷状态设置在57.5%和42.5%时,提高了机组调频响应效果,延长了储能设备的使用寿命。     

Equalization of series connected lithium-ion batteries based on back propagation neural network and fuzzy logic control

In this article, a nondissipative equalization scheme is proposed to reduce the inconsistency of series connected lithium-ion batteries. An improved Buck-Boost equalization circuit is designed, in which the series connected batteries can form a circular energy loop, equalization speed is improved, and modularization is facilitated. This article use voltage and state of charge (SOC) together as equalization variables according to the characteristics of open-circuit voltage (OCV)-SOC curve of lithium-ion battery. The second-order RC equivalent circuit model and back propagation neural network are used to estimate the SOC of lithium-ion battery. Fuzzy logic control (FLC) is used to adjust the equalization current dynamically to reduce equalization time and improve efficiency. Simulation results show that the traditional Buck-Boost equalization circuit and the improved Buck-Boost equalization circuit are compared, and the equalization time of the latter is reduced by 34%. Compared with mean-difference algorithm, the equalization time of FLC is decreased by 49% and the energy efficiency is improved by 4.88% under static, charging and discharging conditions. In addition, the proposed equalization scheme reduces the maximum SOC deviation to 0.39%, effectively reducing the inconsistency of batteries.     

State of charge estimation for lithium-ion battery based on an intelligent adaptive unscented Kalman filter

Adaptive unscented Kalman filter (AUKF) has been widely used for state of charge (SOC) estimation of lithium-ion battery. The noise covariance of the conventional AUKF method is updated based on the innovation covariance matrix (ICM), which is estimated using the error innovation sequence (EIS). However, the distribution of EIS changes due to the time-varying noise, load current dynamics and modelling error, which will lead to inaccurate ICM estimation. Therefore, an intelligent adaptive unscented Kalman filter (IAUKF) method is proposed to detect the distribution change of EIS. Then, the ICM is estimated based on the EIS after the distribution change. Results show that the IAUKF method can improve SOC estimation accuracy significantly. Compared with that of the AUKF method, the root mean squared error and the mean absolute error of SOC based on the IAUKF method decrease by 43.70% and 72.37% under random walk discharge condition, respectively. In addition, the computation time of the IAUKF method slightly increases by 6.27% compared with that of AUKF method. Finally, the effect of initial parameters on the SOC estimation accuracy was analysed. The results indicate that proper algorithm tuning, such as initial window length of EIS for ICM update and the threshold value, can further improve the SOC accuracy based on the proposed IAUKF method. The proposed IAUKF method also shows high robustness against initial measurement noise covariance.