Aggregator-based demand response mechanism for electric vehicles participating in peak regulation in valley time of receiving-end power grid

With the increase in the power receiving proportion and an insufficient peak regulation capacity of the local units, the receiving-end power grid struggles to achieve peak regulation in valley time. To solve this problem while considering the potential of the large-scale charge load of electric vehicles(EVs), an aggregator-based demand response(DR) mechanism for EVs that are participating in the peak regulation in valley time is proposed in this study. In this aggregator-based DR mechanism, the profits for the power grid’s operation and the participation willingness of the EV owners are considered. Based on the characteristics of the EV charging process and the day-ahead unit generation scheduling, a rolling unit commitment model with the DR is established to maximize the social welfare. In addition, to improve the efficiency of the optimization problem solving process and to achieve communication between the independent system operator(ISO) and the aggregators, the clustering algorithm is utilized to extract typical EV charging patterns. Finally, the feasibility and benefits of the aggregator-based DR mechanism for saving the costs and reducing the peak-valley difference of the receiving-end power grid are verified through case studies.

Electric Vehicle Charging Load Optimization Strategy Based on Dynamic Time-of-Use Tariff

Electric vehicle(EV)is an ideal solution to resolve the carbon emission issue and the fossil fuels scarcity problem in the future.However,a large number of EVs will be concentrated on charging during the valley hours leading to new load peaks under the guidance of static time-of-use tariff.Therefore,this paper proposes a dynamic time-of-use tariff mechanism,which redefines the peak and valley time periods according to the predicted loads using the fuzzy C-mean(FCM)clustering algorithm,and then dynamically adjusts the peak and valley tariffs according to the actual load of each time period.Based on the proposed tariff mechanism,an EV charging optimization model with the lowest cost to the users and the lowest variance of the grid-side load as the objective function is established.Then,a weight selection principle with an equal loss rate of the two objectives is proposed to transform the multi-objective optimization problem into a single-objective optimization problem.Finally,the EV charging load optimization model under three tariff strategies is set up and solved with the mathematical solver GROUBI.The results show that the EV charging load optimization strategy based on the dynamic time-of-use tariff can better balance the benefits between charging stations and users under different numbers and proportions of EVs connected to the grid,and can effectively reduce the grid load variance and improve the grid load curve.

Power management in co-phase traction power supply system with super capacitor energy storage for electrified railways

Increasing railway traffic and energy utilization issues prompt electrified railway systems to be more economical,efficient and sustainable.As regenerative braking energy in railway systems has huge potential for optimized utilization,a lot of research has been focusing on how to use the energy efficiently and gain sustainable benefits.The energy storage system is an alternative because it not only deals with regenerative braking energy but also smooths drastic fluctuation of load power profile and optimizes energy management.In this work,we propose a co-phase traction power supply system with super capacitor(CSS_SC)for the purpose of realizing the function of energy management and power quality management in electrified railways.Besides,the coordinated control strategy is presented to match four working modes,including traction,regenerative braking,peak shaving and valley filling.A corresponding simulation model is built in MATLAB/Simulink to verify the feasibility of the proposed system under dynamic working conditions.The results demonstrate that CSS_SC is flexible to deal with four different working conditions and can realize energy saving within the allowable voltage unbalance of 0.008%in simulation in contrast to 1.3%of the standard limit.With such a control strategy,the performance of super capacitor is controlled to comply with efficiency and safety constraints.Finally,a case study demonstrates the improvement in power fluctuation with the valley-to-peak ratio reduced by 20.3%and the daily load factor increased by 17.9%.

Multifunction Battery Energy Storage System for Distribution Networks

Battery Energy Storage System(BESS)is one of the potential solutions to increase energy system flexibility,as BESS is well suited to solve many challenges in transmission and distribution networks.Examples of distribution network’s challenges,which affect network performance,are:(i)Load disconnection or technical constraints violation,which may happen during reconfiguration after fault,(ii)Unpredictable power generation change due to Photovoltaic(PV)penetration,(iii)Undesirable PV reverse power,and(iv)Low Load Factor(LF)which may affect electricity price.In this paper,the BESS is used to support distribution networks in reconfiguration after a fault,increasing Photovoltaic(PV)penetration,cutting peak load,and loading valley filling.The paper presents a methodology for BESS optimal locations and sizing considering technical constraints during reconfiguration after a fault and PV power generation changes.For determining themaximumpower generation change due to PV,actual power registration of connected PV plants in South Cairo Electricity Distribution Company(SCEDC)was considered for a year.In addition,the paper provides a procedure for distribution network operator to employ the proposed BESS to perform multi functions such as:the ability to absorb PV power surplus,cut peak load and fill load valley for improving network’s performances.The methodology is applied to a modified IEEE 37-node and a real network part consisting of 158 nodes in SCEDC zone.The simulation studies are performed using the DIgSILENT PowerFactory software andDPL programming language.The Mixed Integer Linear Programming optimization technique(MILP)in MATLAB is employed to choose the best locations and sizing of BESS.

基于Evans截割模型的镐型截齿峰值截割力的计算

为了能对镐型截齿在平面截割截槽对称条件下的峰值截割力进行较为准确的预测,基于Evans的截割模型,通过分析截割时齿头的锥形表面因岩石的夹制效应而接触应力分布有所不同,理论推导出了一个新的峰值截割力计算公式以及公式应满足的截割边界条件。相比现有其他截割力计算公式,除了考虑截齿半锥角θ、煤岩抗拉强度σt及齿岩之间摩擦因数f等参数的影响,且将煤岩的脆性指数m引入其中,计算结果与试验值更为接近。公式所应满足的截割边界条件,可用截深h和加载位置与相邻自由边界垂直距离s比值的最低限值smin/h表示,且值大小受截齿半锥角θ影响较小,而主要与煤岩脆性指数m有关,当m介于5～15时,smin/h介于2～3,符合既有试验所得结果。所得公式和结论可为进一步分析和推导镐型截齿在实际采掘条件下包含更多参数的峰值截割力提供理论基础和指导。

复式楔形掏槽在大断面隧道掘进中的应用研究

掏槽孔爆破效果对整个断面的爆破质量有着重要影响,为解决大断面隧道掘进困难,炮孔利用率低的问题,采用基于ANSYS/LS-DYNA的流固耦合算法对比研究单楔形掏槽与复式楔形掏槽的内部有效应力与损伤破坏范围,与现场实际爆破效果印证解释了复式楔形掏槽爆破效果优于单楔形掏槽的原因。研究结果表明:单楔形掏槽应力峰值出现在孔底处,随孔底至堵塞段应力峰值缓慢降低,堵塞段到掌子面应力峰值骤降。复式楔形掏槽应力峰值则出现在一级掏槽孔底位置,且其数值大小高于单楔形掏槽应力峰值。选取两种掏槽模型的损伤区域截面发现,两者的破碎面积接近,但单楔形掏槽模型的堵塞段至掌子面区域的岩石未能破碎贯通,复式楔形掏槽模型整个槽腔完全贯通。根据数值模拟结果改进了某公路隧道爆破方案并进行了现场试验,复式楔形掏槽能更好地解决大断面隧道爆破炮孔利用率低以及爆后大块多的问题。研究结果可为相关隧道掏槽孔布设方案提供选择和参考。

基于车网互动的区域电网优化调度研究

电动汽车(Electric Vehicles, EV)充电行为具有随机性的特点,大规模电动汽车接入电网进行无序充电严重影响电力系统的稳定性、安全性。建立了EV充放电行为模型,分析了其调度潜力;并以EV充放电功率等作为决策变量、以充放电电价作为激励参量,建立了一种以区域电网经济性最高、新能源消纳效果最佳、需求侧功率曲线最平缓为目标的优化调度模型。通过NSGA-Ⅱ算法求解调度模型,得到帕累托解集,最后基于AHP决策方法决定最佳调度方案,实现电力系统削峰填谷、新能源消纳,降低大规模EV接入电力系统带来的消极影响。通过蒙特卡洛抽样方法模拟用户侧充电需求,仿真验证结果表明该方法可提高区域电网的经济性,增强新能源消纳能力,平抑负荷,有助于提高区域电网的安全稳定性。

蓄能型空气源吸收式热泵性能分析

提出一种基于空气源吸收式热泵的蓄热系统,构建系统数学模型,通过Matlab软件模拟运行,研究其运行特性并进行性能分析和经济性分析。蓄能型空气源吸收式热泵蓄能供热工况和释能供热工况的能量效率分别为0.58和0.99,系统总的能量效率为1.57,蓄能密度为6.17×10^(5)kJ/m^(3)。蓄能型空气源吸收式热泵在低谷时段进行蓄能,非低谷时段释能,有效降低供暖季运行费用,与传统的城市集中供热方式相比,蓄能型空气源吸收式热泵的投资回收期为3.89年。

基于紧迫性需求的电动汽车协调充电优化策略

电动汽车(electric vehicles,EV)的随机充电会导致峰值负荷突变,进而增加了电网运行波动的风险。为此,提出了一种基于微电网的电动汽车协调充电调度策略,算例表明该策略可以降低负荷的峰值,减弱了随机充电行为对于电网波动的风险。首先,考虑充电紧急性指标(charging urgency index,CUI)来反映不同的充电需求,以及利用蒙特卡洛法模拟电动汽车充电时间行为的随机性,进一步保证电动汽车的协调充电。其次,以整体峰谷负荷差最小为目标,建立协调充电调度的优化模型,考虑了电动汽车慢速和快速充电以及微电网运行各种限制。仿真结果表明,在两种充电模式下,该方法较不协调充电方法在500辆电动汽车的情况下能够将峰值负荷分别降低54.71%、46.38%,能有效地解决电动汽车车主的充电选择模式以及降低微电网运行的风险,为微电网削峰填谷提供策略。

大长径比小深孔高速钻削BTA刀具的参数优化

为通过保证刀杆刚度以实现大长径比小深孔的高速钻削加工,文中建立了错齿内排屑深孔钻(BTA)钻头受力模型,得到钻头所受的各向分力与几何角度的关系。建立三维钻削有限元模型,采用AdvantEdge仿真软件模拟了BTA深孔钻的钻削过程,分析BTA刀具三个刀齿(边齿、中心齿和中间齿)前角、后角和余偏角对切削力和刀具温度峰值的影响,得到高速钻削大长径比小深孔最优的BTA刀具几何参数。结果表明:切削力Fz和刀具温度峰值均随边齿后角的增大而减小,边齿余偏角增大时,切削力Fz先减小后增大,在余偏角为18°时,切削力Fz最小。中心齿后角为13°时,切削力Fz和刀具温度峰值都达到最小值。切削力Fz和刀具温度峰值均随中间齿余偏角的增大而减小。该优化结果为小深孔高速钻削加工中错齿BTA刀具几何角度参数的选择提供参考。

基于用户侧电网负荷调峰的储能电站控制技术及仿真分析

本文主要探究了基于用户侧电网负荷调峰的储能电站控制系统的设计与仿真。该系统可根据用户侧电网负荷的不同,自动调整储能装置的充放电,做到了在用电低谷期快速充电、用电高峰期快速放电;同时,配合新能源发电系统进行充电,在保证电能质量、满足用电需求的前提下,降低了用电成本。从仿真结果来看,储能电站输出电压与输出电流的波形较为稳定,能够满足用户负荷,达到了设计预期。

高强灌浆料加固灌注桩桩头研究

加固的桩头承载能力对静载试验成功与否至关重要,常规做法是采用混凝土进行桩头加固,但周期较长,且有时效果不好。统计表明,用混凝土加固的试验桩桩头,压爆数量占试桩总破坏数量的20%左右,基于此采用了高强灌浆料代替混凝土进行桩头加固。设计了水泥基高强灌浆料的配合比,制作了三组试块,轴心抗压强度试验结果表明,该材料短期强度发挥较快,1、3、7 d的平均抗压强度可以达到35.3、51.5、68.5 MPa。大量现场试验证明该材料加固混凝土试验桩在技术上是可行的,且具有很大的时间优势。针对不同承载力灌注桩,给出了桩头加固形式和龄期的建议。

“双碳”背景下泸州市天然气(页岩气)产业发展机遇

随着我国“双碳”目标的提出,能源转型必将经历一个从“品种更替”到“外部取代”的过渡期。天然气(页岩气)以其低碳、清洁、高效、灵活、易储等特点,在“品种更替”阶段将成为代替存量煤、石油的主要能源,在“外部取代”阶段将成为新能源的“伴侣”,弥补新能源的缺陷。泸州市页岩气资源丰富,未来的利用方向将主要集中在制氢、发电、城市燃气、LNG、化工原料等领域。

Improved Data Processing of Loading Spectrum for Applications of Rainflow Counting Method

The rainflow counting method is a reasonable cyclecounting procedure for fatigue life calculation and simulation testing of structures.It defines cycles as closed stress /strain hysteresis loops.Application of the rainflow counting method requires a data processing of the loading spectrum,which consists of the elimination of non-peak value data points,load time histories adjustment and loop extraction.In the data processing of the loading spectrum,if a stress point is neither the peak nor the valley,it will be identified and eliminated from the loading spectrum.Generally,the loading process is idealized as a single peak-valley straight line.But in actually,there are polylines or nearly straight lines between peaks and valleys which can't be ignored.Therefore,in the process of eliminating such data points,it will produce error in method itself.To reduce the error produced by the traditional method itself,a new method which can well simplify the polylines in data processing of loading spectrum is proposed in this paper.Comparing with the original approximation method,the proposed method has higher precision.

Herrmann 公式在最优滤波器设计中的应用

O.Herrmann 通过分析切比雪夫解析解,推导出估算低通滤波器阶数 N的公式(简称 Herramnn 公式),该公式揭示了截止频率、阶数和峰值误差之间的关系.本文的研究是在 Herrmann 公式的基础上,分析了低通滤波器与高通、带通、带阻滤波器在频带上的关系,利用频带变换的方法,将 Herrmann公式推广到高通及对称带阻滤波器阶数 N 的估算中,并根据最佳逼近原理和Remez 算法,研制出一般选频滤波器等波纹逼近设计的具体算法程序.

Non-Parametric Local Maxima and Minima Finder with Filtering Techniques for Bioprocess

Typically extrema filtration techniques are based on non-parametric properties such as magnitude of prominences and the widths at half prominence, which cannot be used with data that possess a dynamic nature. In this work, an extrema identification that is totally independent of derivative-based approaches and independent of quantitative attributes is introduced. For three consecutive positive terms arranged in a line, the ratio (R) of the sum of the maximum and minimum to the sum of the three terms is always 2/n, where n is the number of terms and 2/3 ≤ R ≤ 1 when n = 3. R > 2/3 implies that one term is away from the other two terms. Applying suitable modifications for the above stated hypothesis, the method was developed and the method is capable of identifying peaks and valleys in any signal. Furthermore, three techniques were developed for filtering non-dominating, sharp, gradual, low and high extrema. Especially, all the developed methods are non-parametric and suitable for analyzing processes that have dynamic nature such as biogas data. The methods were evaluated using automatically collected biogas data. Results showed that the extrema identification method was capable of identifying local extrema with 0% error. Furthermore, the non-parametric filtering techniques were able to distinguish dominating, flat, sharp, high, and low extrema in the biogas data with high robustness.

Study on the Critical Production Calculation Method of the Water-Flooding Reservoir with Gas Cap

The aim of this paper is to solve the problems that the existing method of critical production of gas cap reservoir is only suitable for single-phase flow, and the method of critical production of gas cap reservoir under water-flooding is still blank. In this paper, the relationships between dynamic and static equilibrium, plane radial flow theory, oil-water infiltration method and three-dimensional seepage field decomposition theory, were applied to study a calculation method for critical production of directional wells and horizontal wells. Furthermore, the effects of different factors on critical output were studied, such as horizontal permeability, ratio of horizontal permeability to vertical permeability, length of horizontal section, effective thickness, viscosity of crude oil and water content etc. Results show that the critical production increases with the increment of the horizontal permeability, the ratio of the vertical permeability to the horizontal permeability, the reservoir thickness and the horizontal well length;when the viscosity of crude oil is small, the critical production decreases first and then increases with the increase of water content;when the viscosity of crude oil is high, the critical production increases continuously with the increase of water content. This study could provide theoretical and technical guidance for changing of the working system of oil wells. It can avoid gas channeling and improve the development effect.

基于Levy飞行的HS算法对EV有序充电的优化研究

针对小区内电动汽车(electric vehicle,EV)大规模接入无序充电对配电网产生不利影响的问题,该文提出一种基于Levy飞行的和声搜索(harmony search,HS)算法来优化EV有序充电问题。该算法考虑EV无序充电对线路电压偏差和配电变压器负载率的影响,以EV充电费用最低以及配电变压器负荷峰谷差最小作为优化目标,完成对EV有序充电的调度优化。为验证文中优化算法的有效性,对某小区算例与试点分别进行仿真分析与试验研究。结果表明,文中EV有序充电优化算法策略不仅能减少居民充电电费支出,而且对配电网负荷起到一定的削峰填谷的作用。

供热机组低压缸近零出力低压流场和温度场数值模拟与分析

为研究低压缸切缸运行后,汽轮机鼓风、水蚀等安全问题,为供热汽轮机切缸运行提供理论指导。论文采用SSTκ-ω湍流模型和非平衡相变模型,以某350MW供热汽轮机为研究对象,对次末两级流动进行数值模拟,深入分析切除低压缸后,不同冷却流量下低压末两级蒸汽流动特性、温度变化及蒸汽凝结特性,分析异常工况。计算结果表明:该机组切缸后,流动恶化和鼓风超温等异常工况主要在低压缸进汽流量由60t/h下降至20t/h的过程中。冷却流量下降到60.1t/h时,进汽角增大,蒸汽偏转冲击叶片背部,叶栅通道沿流向压差减小甚至出现逆压区,在末级形成涡流;冷却流量下降到40.3t/h时,末级进入鼓风工况;随着冷却流量进一步下降,在30.4t/h时发生鼓风超温,末级动叶顶蒸汽温度超过100℃。

基于用户响应的分时电价策略研究

针对因不恰当电价政策改变负荷曲线的峰谷特性而引起的用电时段需要频繁重新划分的问题,首先,引入弹性效应权重对需求价格弹性矩阵进行改进,建立了用户响应模型。然后,基于模糊聚类对负荷峰谷时段进行了划分。最后,以负荷峰值和负荷波动系数最小为目标,建立了峰谷分时电价的决策模型,讨论了峰谷倒置对优化结果的影响。结果表明,应用所提模型可使负荷曲线保持原有峰谷特性,同时可使负荷波动有效降低。