氢燃料汽车双向DC-DC变换器改进模型预测控制

双向交错并联DC-DC(BDC)变换器是氢燃料电池汽车实现供电可靠性和能量回收的重要设备,采用传统控制方法时BDC变换器面临着响应速度慢、稳定性不高、输出电流纹波大等问题,针对上述问题,本文采用一种带约束条件改进模型预测电流控制方法.该策略针对BDC变换器两种不同工作模式分别建立其数学模型,基于矢量工作原理搭建BDC变换器不同工作模式改进电流预测模型;然后针对模型预测控制过程开关抖动频繁的问题,对成本函数进行优化设计,约束条件中加入控制变量增量;为解决输出电流纹波问题,改进模型预测控制策略通过在线计算开关占空比,得出矢量作用时间,设计成本函数实现控制目标;实验和仿真对比结果显示传统电流控制方法响应时间和电流纹波分别为0.1 s和5 A,改进MPC模型预测控制响应时间和电流纹波分别为0.02 s和1.5 A,实验和仿真对比结果表明带约束条件模型预测电流控制具有更好的动态响应和稳定性能,验证该算法的有效性.     

电能表费控体系及远程费控技术分析

随着我国经济社会的发展和进步,电力资源已经成为发展建设必不可少的一部分。但在电力服务的过程中,不乏出现电费回收率较低、电费回款周期较长、电力工作者工作强度较大,甚至出现坏账等情况,严重影响电力企业的经营和发展。对此,电力系统开始应用远程费控技术,通过智能电能表、采集终端等计量设备,实现信息存储、实时监控、余额告警等功能。本文对电能表费控体系及远程费控技术进行探究分析,对技术构成等进行深入了解,提升远程费控技术应用的有效性。     

基于大数据高维分析理论的用户用电模式分析

电力用户在整个电力系统中的地位和作用越来越重要,为帮助指导电力企业的经营,实现电力用户用电的高效管理、指导精细化需求侧管控工作,对用户用电模式进行分析。针对智能电表获取的用户用电信息,采用高维随机矩阵理论建立用户用电模式随机非参数模型,利用特征值密度函数和核密度函数具体分析用户用电量数据与不同用电模式及用户节能潜力的关联关系;并以某市实际电力用户用电数据为例,分析了用电行为习惯、节能用电态度等。结果表明,各模式用户当用电弹性指数较大及用电刚性需求指数较小时用户节电潜力较大,研究结果为用户用电模式的分析提供了新方法。     

我国与国际能源署用电量指标对比分析

为准确开展我国与世界主要国家用电量及其行业构成的国际比较,从行业用电构成方面为我国产业结构调整提供国际经验借鉴,本文对我国国家统计局与国际能源署用电量统计口径、内涵和终端用电分类进行了对比分析。结果表明,双方在用电量指标的分类和内涵上均有所区别,国家统计局用电量口径大于国际能源署,工业用电比重偏大;2000年到2012年间,国家统计局统计的我国用电量和人均用电量数据约是国际能源署相应数据的1.06~1.07倍,国家统计局统计的2012年我国终端工业用电比重与国际能源署口径相比高3.4个百分点,而居民、商业服务业用电比重相比则分别低1.8和2.3个百分点。建议在开展中外用电量的国际比较时,准确区分中外用电量的统计口径,正确应用统计数据。     

基于ARIMA模型对汽车工厂用电量分析与预测

研究了利用时间序列基本分析方法-ARIMA模型分析法,对汽车工厂每月用电量进行数据分析、处理、拟合、检验及预测。以2015年1月至2018年9月用电计量数据作为分析样本,使用Eviews 10软件对该时间序列进行回归建模。通过对比不同模型,最终选择ARIMA(1, 1, 1)(1, 1, 1)12模型;通过用电量预测方程,预测2018年10、11月的用电量分别为19 816 784、21 868 199 kW·h,与实际值进行对比验证,预测误差分别为3.82%和2.94%,结果显示该拟合模型对汽车工厂每月用电量具有良好的预测效果,满足直购电申报量的误差在5%以内的要求。     

基于ARMA-SVM组合模型的售电用户用电量预测方法

影响用户用电量的因素较多,根据其分别受线性和非线性因素影响的特点,该文提出1种基于自回归移动平均模型和支持向量机模型的组合预测方法,构建组合模型后,分别与仅采用自回归移动平均模型和支持向量机模型的预测结果进行对比分析.对比结果表明,组合模型的平均绝对百分误差指标相比单一模型明显降低,可以有效提高用电量预测的精度.     

供电公司直供契约机制设计

通过对供电公司与大用户之间供电契约机制的研究．建立了供电公司与大用户在垄断和竞争市场结构下的供电契约设计模型：在获取的工业大用户消费偏好的信息不完全的情况下．同时考虑到外部竞争的影响．供电公司为了索取不同类型消费者的剩余以及保证其与自身签约．必须针对不同类型消费者来设计不同的售电契约。对大用户直供契约机制作了一些尝试性的研究。     

基于K-L信息量法的安徽省工业用电量预测

针对区域工业用电量与经济指标的相关性,运用K-L信息量法,在月度尺度上筛选出能够指示区域工业用电量变化趋势的经济先行指标,并获得各先行指标的先行期数。以经济先行指标为自变量、区域工业用电量为被因变量建立多元回归模型,根据AIC准则和BIC准则选取最佳拟合方程,得到工业用电量预测模型。运用模型预测安徽省2014年5月-12月的月用电量,结果显示预测精度较高,预测方法可以用于工业用电量预测。     

高新产业用户负荷接入关键要素辨识与预测

鉴于各产业用电要求存在差异,为全面响应用户侧的需求,电网在规划过程中需要根据该地区可能落址的用户及其供电需求进行合理规划。对大用户落户影响因素进行研究并构建大用户落户情况的短期预测,综合电网因素和非电网因素构建大用户落户影响因素体系,依据相关历史数据对不同产业类型的用户建立多元线性回归模型并进行可行性检验,应用SPSS软件分析多元线性回归模型得到回归预测方程,回归系数的正负判断所选取的影响因素对大用户的落户是否会产生积极影响;同时根据所确定的产业落户回归预测方程对短期内地区大用户落户情况进行预测,通过预测模型的精度对比,结果表明,电力公司可以根据模型分析结果研究产业落户的变化情况并进行短期预测,从而对城市电网规划进行合理的调整。     

功率前馈的T型三相三电平光伏并网逆变器快速有限集模型预测控制

为加快T型三电平光伏并网系统的动态响应速度,同时避免传统有限集模型预测控制中预测模型和代价函数在线计算量大的不足,在αβ静止坐标系下提出一种功率前馈的快速矢量选择有限集模型预测并网控制方法。该方法在传统电压外环中引入光伏阵列输出功率前馈作为电流内环的参考值;并结合空间矢量脉宽调制(space vector pulse width modulation,SVPWM)思想,只允许接近逆变器输出参考电压矢量的开关状态参与在线计算与评估。通过Matlab搭建系统仿真模型,与未采用功率前馈及传统有限集模型预测进行对比分析。仿真结果表明:采用功率前馈的快速有限集模型预测控制策略在跟踪参考电流、平衡中点电位方面具有良好的静、动态性能。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Contents in Volume 23,2014

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Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.