Design and Development of Wind-Solar Hybrid Power System with Compressed Air Energy Storage for Voltage and Frequency Regulations

The intermittent nature of wind and solar photovoltaic energy systems leads to the fluctuation of power generated due to the fact that the power output is highly dependent upon local weather conditions, which results to the load shading issue that led to the voltage and frequency instability. In additional to that, the high proportions of erratic renewable energy sources can lead to erratic frequency changes which affect the grid stability. In order to reduce this effect, the energy storage system is commonly used in most wind-solar energy systems to balance the voltage and frequency instability during load variations. One of the innovative energy storage systems is the compressed air energy storage system (CAES) for wind and solar hybrid energy system and this technology is the key focus in this research study. The aim of this research was to examine the system configuration of the CAES system through modelling and experimental approach with PID controller design for regulating the voltage and frequency under different load conditions. The essential elements and the entire system have been presented in this work as thorough modelling in the MATLAB/Simulink environment for different load conditions. The developed model was tested through an experimental workbench using the developed prototype of the compressed air storage in the Siemens Lab at DeKUT and explored the consequence of the working parameters on the system proficiency and the model accuracy. The performance of the system for the developed prototype of CAES system was validated using results from an experimental workbench with MATLAB/Simulink R2022b simulation. The modeling and experimental results, shows that the frequency fluctuation and voltage drop of the developed CAES system during load variations was governed by the I/P converter using a PID_Compact controller programed in the TIA Portal V17 software and downloaded into PLC S7 1200. Based on these results, the model can be applied as a basis for the performance assessment of the compressed air energy storage system so as to be included in current technology of wind and solar hybrid energy systems.

Optimal Dispatch for Battery Energy Storage Station in Distribution Network Considering Voltage Distribution Improvement and Peak Load Shifting

Distribution networks are commonly used to demonstrate low-voltage problems.A new method to improve voltage quality is using battery energy storage stations(BESSs),which has a four-quadrant regulating capacity.In this paper,an optimal dispatching model of a distributed BESS considering peak load shifting is proposed to improve the voltage distribution in a distribution network.The objective function is to minimize the power exchange cost between the distribution network and the transmission network and the penalty cost of the voltage deviation.In the process,various constraints are considered,including the node power balance,single/two-way power flow,peak load shifting,line capacity,voltage deviation,photovoltaic station operation,main transformer capacity,and power factor of the distribution network.The big M method is used to linearize the nonlinear variables in the objective function and constraints,and the model is transformed into a mixed-integer linear programming problem,which significantly improves the model accuracy.Simulations are performed using the modified IEEE 33-node system.A typical time period is selected to analyze the node voltage variation,and the results show that the maximum voltage deviation can be reduced from 14.06%to 4.54%.The maximum peak-valley difference of the system can be reduced from 8.83 to 4.23 MW,and the voltage qualification rate can be significantly improved.Moreover,the validity of the proposed model is verified through simulations.

CNT/High Mass Loading MnO2/Graphene-Grafted Carbon Cloth Electrodes for High-Energy Asymmetric Supercapacitors

Flexible supercapacitor electrodes with high mass loading are crucial for obtaining favorable electrochemical performance but still challenging due to sluggish electron and ion transport.Herein,rationally designed CNT/MnO2/graphene-grafted carbon cloth electrodes are prepared by a“graft-deposit-coat”strategy.Due to the large surface area and good conductivity,graphene grafted on carbon cloth offers additional surface areas for the uniform deposition of MnO2(9.1 mg cm?2)and facilitates charge transfer.Meanwhile,the nanostructured MnO2 provides abundant electroactive sites and short ion transport distance,and CNT coated on MnO2 acts as interconnected conductive“highways”to accelerate the electron transport,significantly improving redox reaction kinetics.Benefiting from high mass loading of electroactive materials,favorable conductivity,and a porous structure,the electrode achieves large areal capacitances without compromising rate capability.The assembled asymmetric supercapacitor demonstrates a wide working voltage(2.2 V)and high energy density of 10.18 mWh cm?3.

Modulation Index Effect on the 5-Level SHE-PWM Voltage Source Inverter

Harmonic content of the voltage source inverters is important and must be in the allowed ranges. Different method are proposed to decrease the Total Harmonic Distortion (THD) and caused to be sinusoidal the output voltage of inverters. One of these methods is using multilevel structure. In this structure many important parameters which are effective on voltage source inverter operation that among them we can mention to modulation index (MI). Variation of modulation index can change the THD. One of the harmonic reduction methods is using multilevel structure. In this paper, a sample 5-level SHE-PWM voltage source inverter is presented and all equation and choosing switching angles for elimination desired harmonics from different order. To investigate the effective parameters on the inverter operation, a typical 5-level inverter is simulated in PSPICE software. The simulation has been done for different values of modulation and its effect on the inverter operation is evaluated.

Research on On-Line Coordinated Control Strategy to Improve the Voltage Vulnerability after Disturbance

The on-line coordinated control strategy among multi-voltage controls is important to keep voltage security in post-fault systems. Based on the wide area measuring information, the energy function, which can qualify the impacts of the different control actions on voltage of different nodes, is proposed. And then, considering the impacts of different control actions on the node voltage being treated as a weight matrix, the energy margin is used as the objective function and the reactive power margin is innovatively used as the constraint to regulate the control actions globally according to the weight values. At last, the objective functions are solved to get the optimal global coordinated control strategies. The proposed method is identified in an IEEE-30 Bus system and the simulation results show that it effectively improves the voltage stability.

带有指令滤波的电力弹簧系统反步控制

针对新能源发电系统因间接性和不确定性导致的电压波动问题,文中首次将反步控制策略应用于电力弹簧(electric spring,ES)系统,并提出一种带有指令滤波的ES反步控制策略。根据ES的数学模型利用反步法设计控制器,并加入指令滤波器,以解决ES反步控制中的计算膨胀问题,同时设计误差补偿信号,并利用Lyapunov稳定性理论验证系统稳定性。通过仿真模拟新能源发电系统网侧电压波动时,ES对关键负载(critical load,CL)电压稳定的效果,以及不同系统参数对文中控制策略的敏感性分析。与传统的比例积分(proportional-integral,PI)控制对比,CL电压动态响应速度提高0.07 s,CL电压畸变率降低31%,参数敏感性分析中CL电压最大偏差率为0.318%,能承受的最大电压幅值波动范围提高52.9 V。仿真结果验证了文中所提出的控制策略具有响应速度快、谐波含量低、抗干扰能力强的优势。

单相PET级联整流SVPWM均压边界及拓展方法

电力电子变压器(power electronic transformer,PET)是交直流配电系统互联的重要接口设备,然而后级等效负载不平衡将造成前级整流器各模块的电压偏移。针对单相级联H桥整流器空间矢量调制均压失效问题,推导出基于最优矢量选择均压策略的边界计算方法。根据计算所得的负载不平衡度限制边界与级联模块数、调制度以及功率因数的关系,提出了变调制度和功率因数的控制策略以增加均压能力。该策略通过改变直流电压或降低功率因数来重建更宽的均压工作范围,确保原不平衡度均压极限的系统稳定运行。最后,通过三模块级联整流器的仿真与实验验证了该均压边界的正确性,以及所提均压拓展方法保障极端不平衡负载条件下均压的有效性。

Battery Technologies for Grid-Level Large-Scale Electrical Energy Storage

Grid-level large-scale electrical energy storage(GLEES) is an essential approach for balancing the supply–demand of electricity generation, distribution, and usage. Compared with conventional energy storage methods, battery technologies are desirable energy storage devices for GLEES due to their easy modularization, rapid response, flexible installation, and short construction cycles. In general, battery energy storage technologies are expected to meet the requirements of GLEES such as peak shaving and load leveling, voltage and frequency regulation, and emergency response, which are highlighted in this perspective. Furthermore, several types of battery technologies, including lead–acid, nickel–cadmium, nickel–metal hydride, sodium–sulfur, lithium-ion, and flow batteries, are discussed in detail for the application of GLEES. Moreover, some possible developing directions to facilitate efforts in this area are presented to establish a perspective on battery technology, provide a road map for guiding future studies, and promote the commercial application of batteries for GLEES.

Distributed Air-Conditioning Energy Management System within the Smart Grid Context

-Air-conditioning （AC） systems are the major energy consumption units in residential and commercial buildings. In the context of smart grid, optimizing AC operations leads to substantial saving in energy consumption, reducing the consumer＇s bill and contributing to the environment by minimizing carbon emissions from generating stations. This paper presents a distributed AC energy management system for buildings by using networked master-slaves controller architecture. The proposed system was designed, simulated, and experimentally tested by using real AC units in a students＇ residence hall. Based on the students＇ class schedules, several operational scenarios were implemented and tested. The proposed system implementation leads to a 40% to 60% saving of the consumed energy by the tested units. The same energy management scheme can be applied and implemented in other commercial and residential buildings.

三相电力弹簧的无源控制策略研究

针对太阳能、风能等新能源设备大规模并入电网造成的电能质量下降问题,近年来出现了电力弹簧(ES)的概念。依据推导出的三相电力弹簧(TPES)的数学模型,搭建了对应的系统模型,依据无源控制(PBC)理论,分析了系统的无源性,并分别采用传统PI控制和无源控制验证了三相电力弹簧能够维持关键负载(CL)电压的稳定。通过仿真和实验验证,在有功功率变动工况下,无源控制的超调量远远低于PI控制的13.7%,调节时间0.03 s也低于PI控制的0.07 s,静差率0.0002%也小于PI控制的0.08%,表明无源控制的动态性能和静态性能都更出色。此外,相比于传统的PI控制,无源控制所需参数更少,控制系统结构更加简单。

卸荷及瓦斯作用下煤体冲击倾向性特征试验研究

卸荷损伤作用下含瓦斯煤体冲击倾向性研究对于探明地下深部矿井中煤与瓦斯复合型冲击地压形成机理起着关键作用。为了探究卸荷作用对含瓦斯煤体冲击倾向性的影响,对含瓦斯煤体进行了不同卸荷幅度下变上限循环加卸载。试验结果表明:瓦斯对煤体力学性质具有劣化作用,9 MPa围压下经过1 MPa与2 MPa瓦斯作用后的煤试件抗压强度分别降低了11.2%及18.7%;在卸荷幅度分别为3 MPa与6 MPa作用下,煤试件抗压强度分别降低了12.6%与36.5%,剩余弹性能指数分别降低了10.4%与16.7%;含1 MPa瓦斯煤试件抗压强度分别降低约13.5%与39.8%,剩余弹性能指数分别降低了15.9%与43.6%;含2 MPa瓦斯煤试件抗压强度分别降低约16.7%与47.2%,剩余弹性能指数分别降低了20.3%与48.5%;随着卸荷幅度的增加,煤试件力学性能不断降低,且瓦斯作用会进一步加剧卸荷劣化程度,同时随着瓦斯压力的增加,劣化程度逐步加深;此外,卸压作用能够有效降低煤体冲击倾向性,同时含瓦斯煤体经过卸荷作用后冲击倾向性指标劣化程度高于原始煤试件,且随着瓦斯压力的增加,剩余弹性能指数降低程度越高。

北山花岗岩能量演化规律及破坏倾向指标研究

为深入研究北山高放废物地质处置预选区内花岗岩在不同加卸载路径条件下的能量演化规律,针对北山花岗岩圆形柱试样开展了不同初始围压和不同加卸载条件下的室内三轴试验,对试验数据进行处理对比分析,并建立了一种新型的岩石破坏能量倾向性指标。研究结果表明:岩石临界破坏时的总应变能、弹性应变能和耗散应变能均随着初始围压的增大而增大;岩石损伤破坏过程中的声发射特征参数与耗散能间具有较强的相关性;卸荷条件下岩石破坏模式分为内部损伤破坏和轴向应变破坏;在不同卸荷试验条件下岩石破坏能量倾向性指标均先增加后减小,在相同试验条件下,弹性应变能转化为耗散能效率越高,能量倾向性指标则越小,岩石破坏程度则越高。

阻抗模裕度指标在新能源多馈入系统静态电压稳定评估的适应性分析

集中送出的新能源场站大多位于电网末端,随着其有功出力的增加,易出现静态电压失稳。该文将传统的阻抗模指标的应用对象由负荷推广至新能源场站,丰富了该指标在静态电压稳定评估方面的适用性场景,包括含无功补偿的新能源系统、新能源集群馈入系统、以及新能源多机多馈入系统。具体地,首先,分析新能源单馈入系统的临界静态电压稳定条件,并据此给出用于评估新能源场站静态电压稳定性的阻抗模裕度指标及稳定判据;其次,通过将无功补偿设备并入系统阻抗,分析无功补偿对于指标的影响;再次,证明在新能源的集群馈入系统中,公共耦合点(point of common coupling,PCC)的电压失稳将发生在单个新能源场站之前,并据此确定PCC点作为指标的计算节点;之后,为考虑多机多馈入系统中不同新能源场站间的影响,在指标的计算过程中,保留待评估的关键新能源场站,将其他新能源场站等值为阻抗,并入节点阻抗矩阵中,实现方法在多机多馈入系统中的扩展应用。最后,基于PSD-BPA中建立的单机单馈入系统、多机多馈入系统、以及某省实际大电网算例验证指标的有效性。

基于熵值模糊层次分析法的碳化硅负荷接入位置对电网影响评估

高载能负荷参与需求侧响应已成为促进新能源消纳的重要举措,未来新型电力系统面临新能源占比不断提高及高载能负荷大规模接入的情况。亟需研究高载能负荷大规模接入对电网影响,以合理规划新能源机组与高载能负荷在配电网中的位置与容量。为此,以碳化硅负荷为研究对象,基于Matlab/Simulink仿真平台构建含高比例风电的IEEE33节点系统。基于参数摄动法,从电能质量、技术经济性、安全性3个方面评估风电机组与碳化硅负荷不同接入位置对电网的影响。应用熵值模糊层次分析法对仿真结果进行综合评估;评估结果与理论分析一致,验证了熵值模糊层次分析法的有效性。

灰色马尔科夫链在低压光伏弃电量统计中的应用

低压分布式光伏的弃电量作为区域划分和储能容量配置的重要评判依据,长期以来无法准确计算。从源网荷储系统入手,建立基于灰色马尔科夫链的低压分布式光伏弃电量统计模型,利用“天气+时间”双重场景构建状态转移矩阵,对低压分布式光伏弃电量进行统计。测试结果表明,所提方法可以较为准确地获得低压分布式光伏弃电量数据,并可将最大误差控制在5%以内,具有一定的推广价值。

基于SOC的并联储能系统电流负荷分配方法

提出一种基于SOC的改进电流负荷分配方法,该方法采用均流环、电流环、电压环的三闭环结构,其中,均流控制器的电流基准由理想输出功率和储能单元电池荷电状态(state of charge,SOC)共同决定。搭建了MATLAB/Simulink仿真模型和基于TMS320F28335的并联储能系统半实物仿真平台,对比仿真了不同参数影响下系统的性能。并联储能系统中母线电压能够稳定在理想值,电流负荷能够按SOC合理分配,且各储能单元SOC能够快速收敛到均衡状态,验证了所提改进电流负荷分配方法的可行性和合理性。

城市高压配电网负荷转供辅助决策关键技术与系统

城市电网灵活性不足是造成系统调峰与输电阻塞问题的根本原因,为解决这一问题,提出了一种考虑城市高压配电网负荷转供及储能充放电策略的协同优化策略,并开发了一套可实现高压配电网灵活运行调度的在线辅助决策系统。通过分析城市高压配电网的拓扑特点,在其变电单元简化拓扑建模的基础上,分别以最小化220 kV输电网运行成本和110 kV高压配电网负荷削减成本为上、下层目标,建立时序双层优化模型,通过上下层模型的不断交替迭代,实现对高压配电网拓扑状态及储能运行状态的求解;基于高压配电网标准化站内接线的电气拓扑聚合通用方法,开发了一套可满足高压配电网灵活调度的运行控制与决策支持系统,以实现城市高压配电系统分布式新能源和储能广泛发展的运行方式优化以及调峰与负荷转供策略制定。最后,以某地区电网为例进行方法建模和实用性分析,测试并验证了所提方法的可行性与应用前景。

考虑温湿指数与耦合特征的综合能源负荷短期预测

针对综合能源负荷易受气象因素影响及其异质能量耦合特性所导致的预测建模复杂、准确性不高等问题,提出了一种考虑温湿指数与耦合特征的负荷短期预测模型。首先,在深入挖掘多元负荷耦合特征的基础上,结合温湿指数构造计及多因素影响的输入变量;然后,利用核主成分分析(KPCA)法在确保信息有效的前提下完成对预测输入空间的降维处理,并基于门控循环单元(GRU)神经网络进行预测建模,进一步引入Attention机制实现重要特征的差异化提取;最后,选取某实际系统电、冷负荷数据进行仿真。仿真结果表明,基于KPCA-GRU-Attention模型的电、冷负荷短期预测结果的均方根误差和平均绝对百分误差分别为1025 kW,2.7%和2167 kW,2.9%,准确性得到了显著提升。所提方法能够在考虑多因素影响的基础上有效提高综合能源负荷的短期预测精度,实现了对用能需求的精准感知。

基于动态无功电压灵敏度的有源配电网移动式储能优化调度

随着城市负荷尖峰以及分布式电源渗透率的持续攀升,有源配电网存在负荷峰谷差进一步增大以及电压越限的风险。移动式电池储能系统(MBESS)具备时间-空间灵活性和四象限输出能力,考虑其有功出力参与削峰填谷、无功出力参与电压调节,提出了一种基于电压灵敏度分析的有源配电网MBESS的优化调度方法。首先,针对MBESS出力与接入位置之间的耦合影响,推导定有功功率条件下满足仿射关系的无功电压修正灵敏度;其次,考虑不同网络结构下不同节点电压的调整需求,提出一种动态无功电压修正灵敏度的计算方法,旨在确定MBESS的时序最优接入方案;然后,构建充分考虑运行经济性与可靠性的MBESS双层优化调度模型;最后,以IEEE 33节点配电系统为例,采用增强烟花算法对所提模型进行求解,结果表明所提方法能够在保证MBESS具备较好经济效益的同时,有效减小负荷峰谷差以及提升配电系统的整体电压水平。

多级围压变应力下限循环加卸载煤体冲击倾向性特征研究

围压作用下煤体冲击倾向性研究对于探明地下深部矿井中煤体冲击地压形成机理起着关键作用。为了探究不同围压作用对煤体冲击倾向性的影响,对煤体进行了多级围压下不同应力下限循环加卸载。结果表明:在3、6、9 MPa围压环境下变应力下限循环加卸载作用后煤试件抗压强度分别增加了3.1%、4.7%、6.2%,最后一级循环加卸载过程中轴向应变分别增加了0.61%、0.42%、0.28%,体积应变分别增长了0.32%、0.24%、0.17%,表明煤体受到的围压越大对煤体变形约束越强;随着围压的提高,声发射事件累积数量逐渐降低,峰后声发射累积数量不断降低,累积能量同样逐步降低,表明随着围压的升高,煤试件变得更加致密,破坏形式逐渐由脆性破坏过渡到韧性破坏;经过3、6、9 MPa围压作用,输入能Uinn与弹性应变能Uen不断升高,较之常压条件下煤试件剩余弹性能指数CEF分别提高了21.76%、42.92%、71.69%,说明围压对煤体冲击倾向性具有增强作用,且剩余弹性能指数CEF与围压σ3具有线性函数关系。