A Two-Layer Fuzzy Control Strategy for the Participation of Energy Storage Battery Systems in Grid Frequency Regulation

To address the frequency fluctuation problem caused by the power dynamic imbalance between the power system and the loadwhen a large number of newenergy sources are connected to the grid,a two-layer fuzzy control strategy is proposed for the participation of the energy storage battery system in FM.Firstly,considering the coordination of FM units responding to automatic power generation control commands,a comprehensive allocation strategy of two signals under automatic power generation control commands is proposed to give full play to the advantages of two FM signals while enabling better coordination of two FM units responding to FM commands;secondly,based on the grid FM demand and battery FM capability,a double-layer fuzzy control strategy is proposed for FM units responding to automatic power generation control commands in a coordinated manner under dual-signal allocation mode to precisely allocate the power output depth of FM units,which can control the fluctuation of frequency deviation within a smaller range at a faster speed while maintaining the battery charge state;finally,the proposed Finally,the proposed control strategy is simulated and verified inMatlab/Simulink.The results show that the proposed control strategy can control the frequency deviation within a smaller range in a shorter time,better stabilize the fluctuation of the battery charge level,and improve the utilization of the FM unit.

Research on Optimal Configuration of Energy Storage in Wind-Solar Microgrid Considering Real-Time Electricity Price

Capacity allocation and energy management strategies for energy storage are critical to the safety and economical operation of microgrids.In this paper,an improved energymanagement strategy based on real-time electricity price combined with state of charge is proposed to optimize the economic operation of wind and solar microgrids,and the optimal allocation of energy storage capacity is carried out by using this strategy.Firstly,the structure and model of microgrid are analyzed,and the outputmodel of wind power,photovoltaic and energy storage is established.Then,considering the interactive power cost between the microgrid and the main grid and the charge-discharge penalty cost of energy storage,an optimization objective function is established,and an improved energy management strategy is proposed on this basis.Finally,a physicalmodel is built inMATLAB/Simulink for simulation verification,and the energy management strategy is compared and analyzed on sunny and rainy days.The initial configuration cost function of energy storage is added to optimize the allocation of energy storage capacity.The simulation results show that the improved energy management strategy can make the battery charge-discharge response to real-time electricity price and state of charge better than the traditional strategy on sunny or rainy days,reduce the interactive power cost between the microgrid system and the power grid.After analyzing the change of energy storage power with cost,we obtain the best energy storage capacity and energy storage power.

A novel coordinated control strategy considering power smoothing for a hybrid photovoltaic/battery energy storage system

This work presents a novel coordinated control strategy of a hybrid photovoltaic/battery energy storage(PV/BES) system. Different controller operation modes are simulated considering normal, high fluctuation and emergency conditions. When the system is grid-connected, BES regulates the fluctuated power output which ensures smooth net injected power from the PV/BES system. In islanded operation, BES system is transferred to single master operation during which the frequency and voltage of the islanded microgrid are regulated at the desired level. PSCAD/EMTDC simulation validates the proposed method and obtained favorable results on power set-point tracking strategies with very small deviations of net output power compared to the power set-point. The state-of-charge regulation scheme also very effective with SOC has been regulated between 32% and 79% range.

Empowering the Future: Exploring the Construction and Characteristics of Lithium-Ion Batteries

Lithium element has attracted remarkable attraction for energy storage devices, over the past 30 years. Lithium is a light element and exhibits the low atomic number 3, just after hydrogen and helium in the periodic table. The lithium atom has a strong tendency to release one electron and constitute a positive charge, as Li . Initially, lithium metal was employed as a negative electrode, which released electrons. However, it was observed that its structure changed after the repetition of charge-discharge cycles. To remedy this, the cathode mainly consisted of layer metal oxide and olive, e.g., cobalt oxide, LiFePO4, etc., along with some contents of lithium, while the anode was assembled by graphite and silicon, etc. Moreover, the electrolyte was prepared using the lithium salt in a suitable solvent to attain a greater concentration of lithium ions. Owing to the lithium ions’ role, the battery’s name was mentioned as a lithium-ion battery. Herein, the presented work describes the working and operational mechanism of the lithium-ion battery. Further, the lithium-ion batteries’ general view and future prospects have also been elaborated.

Energy Storage System with Ultracapacitors for Thermal Underwater Glider

A power system with proton exchange membrane fuel cells (PEMFC) was designed for thermal underwater glider.Heat generated by PEMFC is used as the propulsion power of the glider,and the electricity is used in the control and sensor system.An electric energy storage system (ESS) is required which possesses high power density with good cycle life.Ultracapacitors which exhibit high power density and cycle life are considered as energy storage devices.Simulations based on a specific voyage condition indicate that ESS with ultracapacitors has positive effects on reducing the output power demand of PEMFC and lightening the power system.Experimental results show that the state of charge (SOC) is related to the capacitance and resistance in ultracapacitor ESS.

Forecast of natural gas supply and demand in China under the background of “Dual Carbon Targets”

As a kind of clean energy which creates little carbon dioxide, natural gas will play a key role in the process of achieving “Peak Carbon Dioxide Emission” and “Carbon Neutrality”. The Long-range Energy Alternatives Planning System(LEAP) model was improved by using new parameters including comprehensive energy efficiency and terminal effective energy consumption. The Back Propagation(BP) Neural Network–LEAP model was proposed to predict key data such as total primary energy consumption, energy mix, carbon emissions from energy consumption, and natural gas consumption in China. Moreover, natural gas production in China was forecasted by the production composition method. Finally, based on the forecast results of natural gas supply and demand, suggestions were put forward on the development of China’s natural gas industry under the background of “Dual Carbon Targets”. The research results indicate that under the background of carbon peak and carbon neutrality, China’s primary energy consumption will peak(59.4×10^(8)tce) around 2035, carbon emissions from energy consumption will peak(103.4×10^(8)t) by 2025, and natural gas consumption will peak(6100×10^(8)m^(3)) around 2040, of which the largest increase will be contributed by the power sector and industrial sector. China’s peak natural gas production is about(2800–3400)×10^(8)m^(3), including(2100–2300)×10^(8)m^(3)conventional gas(including tight gas),(600–1050)×10^(8)m^(3)shale gas, and(150–220)×10^(8)m^(3)coalbed methane. Under the background of carbon peak and carbon neutrality, the natural gas consumption and production of China will further increase, showing a great potential of the natural gas industry.

Organic fast ion-conductor with ordered Li-ion conductive nano-pathways and high ionic conductivity for electrochemical energy storage

Solid electrolyte(SE)is the most crucial factor to fabricate safe and high-performance all-solid-state lithium-ion batteries.However,the most commonly reported SE,including solid polymer electrolyte(SPE)and inorganic oxides and sulfides,suffer problems of low ionic conductivity at room temperature for SPE and large interfacial impedance with electrodes for inorganic electrolytes.Here we for the first time demonstrate a novel ionic plastic crystal lithium salt solid electrolyte(OLiSSE)fast ion-conductor dilithium(1,3-diethyl-4,5-dicarboxylate)imidazole bromide with ordered Li-ion conductive nanopathways and an exceptional ionic conductivity of 4.4×10^(−3)Scm^(−1)at 30℃.The prepared OLiSSE exhibits apparent characters of typical ionic plastic crystals in the temperature range of−20 to 70℃,and shows remarkable thermal stability and electrochemical stability below 150℃ and 4.7 V,respectively.No lithium dendrite or short circuit behavior is detected for the Li|OLiSSE|Li cell after the galvanostatic charge-discharge test for 500 h.The fabricated Li|OLiSSE|LiFePO_(4) all-solid-state cell without using any separator and liquid plasticizer directly delivers an initial discharge capacity of 151.4 mAh g^(−1) at the discharge rate of 0.1 C,and shows excellent charge-discharge cycle stability,implying large potential application in the next generation of safe and flexible all-solid-state lithium batteries.

Reduced Switching-Frequency State of Charge Balancing Strategy for Battery Integrated Modular Multilevel Converter

A modular multilevel converter(MMC)integrated with split battery cells(BIMMCs)is proposed for the battery management system(BMS)and motor drive system.In order to reduce the switching losses,the state of charge(SOC)balancing strategy with a reduced switching-frequency(RSF)is proposed in this paper.The proposed RSF algorithm not only reduces the switching losses,but also features good balancing performance both in the unbalanced and balanced initial states.The results are verified by extensive simulations in MATLAB/Simulink surroundings.

Provision of Ramp-rate Limitation as Ancillary Service from Distribution to Transmission System:Definitions and Methodologies for Control and Sizing of Central Battery Energy Storage System

The variability of the output power of distributed renewable energy sources(DRESs)that originate from the fastchanging climatic conditions can negatively affect the grid stability.Therefore,grid operators have incorporated ramp-rate limitations(RRLs)for the injected DRES power in the grid codes.As the DRES penetration levels increase,the mitigation of high-power ramps is no longer considered as a system support function but rather an ancillary service(AS).Energy storage systems(ESSs)coordinated by RR control algorithms are often applied to mitigate these power fluctuations.However,no unified definition of active power ramps,which is essential to treat the RRL as AS,currently exists.This paper assesses the various definitions for ramp-rate RR and proposes RRL method control for a central battery ESS(BESS)in distribution systems(DSs).The ultimate objective is to restrain high-power ramps at the distribution transformer level so that RRL can be traded as AS to the upstream transmission system(TS).The proposed control is based on the direct control of theΔP/Δt,which means that the control parameters are directly correlated with the RR requirements included in the grid codes.In addition,a novel method for restoring the state of charge(So C)within a specific range following a high ramp-up/down event is proposed.Finally,a parametric method for estimating the sizing of central BESSs(BESS sizing for short)is developed.The BESS sizing is determined by considering the RR requirements,the DRES units,and the load mix of the examined DS.The BESS sizing is directly related to the constant RR achieved using the proposed control.Finally,the proposed methodologies are validated through simulations in MATLAB/Simulink and laboratory tests in a commercially available BESS.

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is termed a multi-domain(or multi-physics)system.The present paper concerns the use of linear graphs(LGs)to generate a minimal model for a multi-physics system.A state-space model has to be a minimal realization.Specifically,the number of state variables in the model should be the minimum number that can completely represent the dynamic state of the system.This choice is not straightforward.Initially,state variables are assigned to all the energy-storage elements of the system.However,some of the energy storage elements may not be independent,and then some of the chosen state variables will be redundant.An approach is presented in the paper,with illustrative examples in the mixed fluid-mechanical domains,to illustrate a way to recognize dependent energy storage elements and thereby obtain a minimal state-space model.System analysis in the frequency domain is known to be more convenient than in the time domain,mainly because the relevant operations are algebraic rather than differential.For achieving this objective,the state space model has to be converted into a transfer function.The direct way is to first convert the state-space model into the input-output differential equation,and then substitute the time derivative by the Laplace variable.This approach is shown in the paper.The same result can be obtained through the transfer function linear graph(TF LG)of the system.In a multi-physics system,first the physical domains have to be converted into an equivalent single domain(preferably,the output domain of the system),when using the method of TFLG.This procedure is illustrated as well,in the present paper.

基于MMC的分布式储能系统及其快速SOC均衡控制策略

提高基于模块化多电平换流器(modular multilevel converter,MMC)的分布式储能系统(distributed energy storage systems,DESS)的能量利用率,解决储能子模块(energy sub-module,ESM)荷电状态(state of charge,SOC)均衡问题至关重要。针对现有的SOC均衡控制策略的不足,提出内外分层的快速SOC均衡控制策略。外层针对桥臂间或相间的SOC差异,通过改进MMC模型预测控制(model predictive predictive control,MPC),配合自适应均衡系数,快速调整功率差额。内层引入自适应虚拟电阻法,根据ESM的SOC情况确定主导ESM,自适应调节各单元的虚拟电阻,产生相应的电压梯度,结合MMC排序算法使ESM按照各自SOC进行功率分配,从而实现ESM的SOC快速均衡,提高DESS能量利用率。通过在Matlab/Simulink构建仿真模型,证明了所提控制策略的有效性和可行性。

考虑储能约束的神经网络VSG参数自适应控制策略

虚拟同步发电机(Virtual Synchronous Generator, VSG)控制策略常用于处理高比例新能源并网导致系统惯量、阻尼缺失的问题,储能单元的配置制约着VSG惯量阻尼的设定。首先,建立考虑储能荷电状态(State of Charge, SOC)约束的VSG小信号模型,计算多约束条件下惯量阻尼取值范围。然后,借助径向基函数(Radial Basis Function, RBF)神经网络算法处理连续非线性函数的优点,提出一种计及储能约束的RBF神经网络VSG惯量阻尼自适应控制策略。该策略取频率偏差量和频率变化率为输入,输出为VSG转动惯量,根据二阶系统最优阻尼比确定阻尼系数取值。最后通过Matlab/Simulink仿真验证,结果表明所提计及多约束的VSG自适应控制策略能够快速响应系统频率变化,优化系统动态调节能力;减小直流母线电压跌落,增强系统鲁棒性。

锂离子电池储能电站的热失控状态检测与安全防控技术研究进展

锂离子电池具有能量密度大、使用寿命长、工作温度范围宽、自放电小等优点,是中国电化学储能电站的主流电池技术。然而,在加热、过充等恶劣工况下,锂离子电池易发生热失控引发火灾甚至爆炸,因此其安全问题已逐渐成为锂离子电池储能电站建设及大规模应用的首要问题。该文系统分析了锂离子储能电池热失控的诱因、电池内部反应过程及外部特征参量的变化规律,重点总结了当前主要的电池热失控状态检测技术、智能诊断算法及储能电站安全防控技术,最后对储能电站热失控状态检测及安全防控技术进行了总结和展望。

基于新能源-负荷相似性的源荷储协调调峰优化调度

合理利用可调节负荷的响应特性来实现源荷储的协调调度,可有效缓解新能源、负荷的不确定性所带来的调峰压力。基于新能源-负荷(NER-L)相似性,建立可调节负荷响应目标。基于相关系数,建立能准确刻画负荷对新能源出力跟踪匹配程度的NER-L相似性指标,并将指标引入所建源荷储协调调峰的双阶段优化调度模型。第一阶段模型以NER-L相关系数最大为目标,确定可调节负荷在各时段的响应功率并获得最优电网负荷;第二阶段模型以弃风弃光量最小、调峰运行成本最低为目标,优化火电机组及储能出力。以IEEE 30节点系统为例,对NER-L相似性、净负荷峰谷差、系统调峰运行经济性及新能源弃电功率进行计算分析,结果验证了所提模型的有效性。

考虑SOC的混合储能功率分配与自适应虚拟惯性控制

电力电子化的直流配电网存在低惯性问题,不利于系统稳定运行。混合储能设备可向电网提供虚拟惯性,但不同类型的储能之间存在功率协调问题,并且储能的荷电状态(state of charge, SOC)对虚拟惯性的调节也有约束作用。针对上述问题,提出了一种自适应时间常数的分频控制策略,时间常数根据混合储能系统(hybridenergy storage system, HESS)的SOC而动态调整以改变功率分配。首先,通过分析储能SOC与虚拟惯性的关系,并考虑储能充放电极限问题,研究兼顾SOC、电压变化率以及电压幅值的自适应虚拟惯性控制策略,提高系统惯性。然后,建立控制系统的小信号模型,分析虚拟惯性系数对系统的影响。最后,基于Matlab/Simulink搭建直流配电网仿真模型,验证了所提控制策略能合理分配HESS功率,提高超级电容器利用率,改善直流电压与功率稳定性。

基于混合储能荷电状态的光伏直流微网系统能量分配策略

针对混合储能系统在平抑光伏波动以及负荷投切时荷电状态(SOC)易越限问题,提出一种基于混合储能SOC的多模式协调控制策略。在传统低通滤波功率分配的基础上,提出一种基于超级电容荷电状态的动态功率修正策略,使超级电容出力后SOC向安全状态恢复;同时,为避免蓄电池频繁切换充放电状态,在其响应环节加入优化后的延时控制。此外,根据光伏出力情况、混合储能SOC,设计出满足直流微网系统动态平衡的六种运行模式,实时调节各储能单元出力情况。在MATLAB/Simulink中搭建了光伏直流微网混合储能系统仿真模型,仿真结果表明所提策略在各工况下均能稳定运行,有效延长了储能介质使用寿命。

考虑荷电状态一致性的分布式储能电站一次调频控制策略

随着可再生能源比例增加,电网新建储能电站成为提升系统频率稳定性的重要手段。针对电网中分布式储能电站(distributedenergystoragestations,DESS)参与一次调频面临的荷电状态均衡问题,提出了一种考虑荷电状态(state of charge,SOC)一致性的DESS协同控制策略。首先,构建了含分布式储能电站的区域电网调频模型,分析了传统调频控制方法的特点,并讨论了储能在高渗透率新能源电网中的调频及一致性控制需求;其次,分析了电网调频需求与DESS的SOC一致性调整需求之间的耦合关系,设计了基于一致性原理的SOC分布式控制策略,进而构建了兼顾两种需求的DESS一次调频协同控制方法,详细分析了关键控制参数的设计原则与取值方法。最后,搭建典型区域电网模型,结合不同频率波动工况进行了仿真验证,结果表明:所提控制策略可以有效改善电网频率质量,在不增加系统调频负担的前提下实现多个储能电站的SOC一致性调节,减小了DESS集群的SOC越限风险,增强了其聚合控制效果。

New electrochemical energy storage systems based on metallic lithium anode the research status,problems and challenges of lithium-sulfur,lithium-oxygen and all solid state batteries

Li-ion batteries have played a key role in the portable electronics and electrification of transport in modern society. Nevertheless,the limited highest energy density of Li-ion batteries is not sufficient for the long-term needs of society. Since lithium is the lightest metal among all metallic elements and possesses the lowest redox potential of.3.04 V vs. standard hydrogen electrode, it delivers the highest theoretical specific capacity of 3860 mA h g^(-1) and a high working voltage of full batteries which causes a great interest in electrochemical energy storage systems. Lithium-sulfur, lithium-oxygen and corresponding all solid state batteries based on metal lithium anode have received widely attention owing to their high energy densities. However, the problems in the cathode,electrolyte and anode of these three systems restrict their practical application. In this review, the research status and problems of these three energy storage systems are summarized and the challenges and future perspectives are also outlined.

基于改进概率神经网络的储能电池荷电状态估计

锂离子电池荷电状态(SOC)估计技术是储能电站电池管理系统重要组成部分。为了实现对SOC的准确估算,提出一种改进概率神经网络(MPNN)用于储能电池荷电状态估计。相较于传统神经网络,结合概率函数和补偿机制的MPNN,不仅可避免陷入局部最优,而且具有更优秀的拟合能力,可进一步提高SOC估计精度。仿真实验表明,所提MPNN方法的SOC估计值平均绝对误差和均方误差均低于1%,获得了满意的性能。

基于模块化级联拓扑的高压直流直挂储能装置

为了提升柔性直流输电的有功功率调节能力及惯量支持能力,研究了基于模块化级联拓扑的高压直流直挂储能技术,探索了高压直流直挂储能的工程化实施方案、控制系统架构及控制策略,提出了基于子模块电池荷电状态排序的改进型最近电平逼近调制策略,用于解决电池荷电状态及子模块开关频率整体均衡的问题。给出了高压直流直挂储能关键参数的计算方法。研制了基于磷酸铁锂电池的高压直流直挂储能模块及控制系统样机,搭建了含高压直流直挂储能的柔性直流输电系统的电磁暂态仿真模型和基于串联变流器的试验平台,通过系统仿真及样机试验验证所提高压直流直挂储能方案的可行性。