双馈风机控制方式对继电保护动作的影响研究

将双馈风机接入到配电网中,会对配电网的继电保护动作造成一定的影响,特别是双馈风机的控制方式对继电保护的影响是最为严重的。因此,本文将对双馈风机控制方式对继电保护的影响进行分析。本文首先对双馈风机的概况进行综述,其次对数学模型以及控制策略进行阐述,最后对继电保护的影响进行分析,以供参考与借鉴。     

多转子系统轴系标高变化对振动的影响分析

对大型汽轮发电机组轴系标高对振动的影响进行了分析,提出了运行中判断转子对中状态的合理方法。指出标高对振动的影响需要根据故障的性质而定,标高变化对强迫振动的影响较小,对自激振动的影响较大。     

考虑弧垂情况下交流输电线路的地面电场分布

为研究交流输电线路下方的实际地面电场分布,分别分析了导线对地高度对导线电荷量和地面电场的影响。分析结果表明:导线对地高度对电荷量影响不大;在电荷量一定的前提下,导线对地高度对地面电场影响很大。因此,在假设导线对地高度不影响导线电荷的基础上,考虑导线的弧垂形状,以微分矢量叠加的方式求解线路下方的实际地面电场分布并以交流特高压为例进行了计算与验证。分析结果表明:线路下方的高场强范围只在导线档中附近存在,电场强度在远离档中的区域迅速减小,与以对地最小对地高度计算得到的地面电场分布差异很大。研究成果对房屋拆迁的判断有重要的指导意义。     

矿车轮对非正常磨损原因分析及预防措施

轮对是矿车的关键部件．它既是行走机构又是承载机构。但在使用过程中因为轮对质量原因常出现掉道脱轨，甚至翻车。严重影响矿井的生产运输安全。通过对矿车轮对的非正常磨损原因分析，提出几种预防和改进措施，提高矿车轮对的使用年限。保证矿车的安全运行。     

水龙头行业能效对标指标体系构建研究及应用

基于水龙头行业高能耗的现状,从管理节能的角度出发,分析某企业生产工艺中各工段的能耗分布情况。通过提取该企业的关键绩效指标(KPI),开展水龙头行业能效对标方法论的研究。在此基础上,选取标杆企业进行对标实践,根据对标结果实施对标企业的节能改造。节能改造后,能源绩效水平大幅提升。提出本研究确定的对标方法论和指标体系在水龙头行业能效对标中是可行的。     

增加风力机叶片翼型后缘厚度对气动性能的影响

以FFA-W3翼型族为研究对象,对其系列翼型的后缘作了加厚处理。利用XFOIL软件对修改前后的翼型的气动性能进行了计算,利用Viterna-Corrigan失速后模型将气动性能数据的攻角扩展到了90°。对修改前后的翼型的气动性能数据的改变作了对比分析。利用原翼型和修改后翼型的气动性能数据对同一个风力机进行了气动性能计算,并对计算结果作了对比分析。结论认为,对翼型后缘进行适当加厚处理对气动性能影响不大,为满足工艺要求在叶片的生产中对翼型后缘作加厚处理是可行的。     

煤种对沸腾床锅炉设计的影响

煤种对沸腾床设计的影响,主要是:对床的截面积的影响、对床的阻力的影响、对床温的影响和对床中浸没受热面的影响。煤种对锅炉整体热力系统的影响,主要     

对标管理在企业节能降耗上的应用

温家宝总理在国务院节能减排工作会议上关于开展对标活动的要求的讲话,引起了广大节能工作者的关注。什么是对标管理？对标管理在节能降耗工作中能发挥多大作用？企业如何开展节能对标活动？在开展对标管理时应注意什么问题？很多节能工作者希望就这些问题有所了解。本文尝试通过对节能对标管理基本概念、组织方法、工作流程等作简单介绍,为企业开展节能对标管理提供参考。     

对标管理在企业节能降耗上的应用

温家宝总理在国务院节能减排工作会议上关于开展对标活动的要求的讲话,引起了广大节能工作者的关注。什么是对标管理?对标管理在节能降耗工作中能发挥多大作用?企业如何开展节能对标活动?在开展对标管理时应注意什么问题?很多节能工作者希望就这些问题有所了解。本文尝试通过对节能对标管理基本概念、组织方法、工作流程等作简单介绍,为企业开展节能对标管理提供参考。     

高原地区柴油机进气系统改造与性能分析

通过对Ｓ１９５柴油机进气管内压力波形的测试,分析了进气管长度对充气性能的影响。论证了不同海拔下最佳进气管长度相等的规律,确定了适宜各种工况的进气管长度。在对最佳进气管转速适应性试验和滤清器对进气管惯性效应影响分析的基础上,肯定了进气管改造对改善高原地区柴油机工作性能的积极意义。     

Applying the kriging method to predicting irradiance variability at a potential PV power plant

One-second irradiance data from forty-five sensors spaced over a one-mile square section of land were analyzed to characterize the short-term (1-s to 1-min) variability of the solar resource in Northern Arizona. The geostatistical interpolation model known as kriging was applied to our data set to better understand the method's strengths and weaknesses in accurately predicting the variations in the irradiance over this relatively small section of land. Of particular interest was to investigate the ability of the kriging method to show the variation in solar irradiance over the section of land as compared to that measured by the sensors. When using data from all the sensors as input to the prediction method, kriging performed very well compared to the sensors. However, because it is unlikely to have a large number of sensors to characterize the variability at a prospective solar site, it was also of interest to investigate how many sensors are required as input to the kriging technique in order to generate a reliable prediction. Solar data from four characteristic periods (related to the four seasons) were analyzed, and different sensor configurations, consisting of subsets of the actual sensor array, were employed using the method to demonstrate the number of sensors required to correctly characterize the short-term irradiance variability at the site. Using four measurement stations as input to the kriging method was shown to reasonably represent the variability in the 1-s to 1-min timescales.     

Preliminary identification of potential markets for off-grid electrification: tool development and a case study of Ghana

With more than one billion people lacking access to electricity in the world, ensuring universal access to electricity by 2030 remains a major challenge which cannot be left to the government initiatives alone. Access to local information and identification of potential areas for investment can be a challenge for investors. This paper provides a tool for preliminary assessment of potential markets for off-grid electrification in developing countries and applies this to Ghana to demonstrate its applicability. A multi-criteria approach is used to rank the districts according to the overall potential and the best markets and least favourable areas for investment are identified. The tool offers flexibility to include new inputs to the analysis and the factor weights can be adjusted as appropriate. The case study shows that the tool can effectively identify potential areas from a list of candidates and offers support to analysts.     

三次谐波电流闭锁式变压器过激磁保护分析

就过激磁的原理、危害及电压互感器二次回路电压异常升高的原因分析,找到了过激磁保护误动的原因。根据变压器过激磁时三次谐波电流的特点,将差动电流中三次谐波电流加入到过激磁保护逻辑程序中,起到谐波电流监测,闭锁过激磁保护的作用。为验证三次谐波电流闭锁式过激磁保护原理,采用专业的电磁暂态仿真软件PSCAD构建变压器过激磁模型,该模型具有较高的仿真精度。再利用MATLAB软件对仿真数据进行了处理分析,并与实测数据进行比较,保证了保护原理的正确性。     

防锈工作三要素

在现代化机械加工行业中,防锈工作日趋重要。提高防锈工作效率,主要应该从根据产品的性能选择正确的防锈材料、安排完整正确的防锈工艺、严格防锈管理三方面入手。正确选择金属加工中所需清洗剂、防锈剂,并使防锈工艺规范化、完整化,保证防锈材料能够充分发挥其性能。同时要有专业的防锈科技人员指导,各级人员严格遵守防锈管理规范,从而使防锈工作发挥其最大功用。     

Impact of regulatory rules on economic performance of PV power plants

The rapid growth of Renewable Energy Sources (RES) power plants connected to the grid has introduced new problems related to the safe and reliable operation of the electricity network from transmission to distribution sectors. New regulatory rules can promote RES producers to make a commitment on the energy amount that is likely to be supplied to the network. The present paper concerns the analysis of the energy production of a PV power plant from the economic point of view, with reference to the presence of regulatory rules. Costs of penalty and value of energy are compared, in order to evaluate the economic efficiency of the plant. Use of auxiliary energy storage devices is investigated, with the aim to determine the relevant dimensions that increase the economic efficiency of the PV plant. A software instrument that implements these algorithms is described and applied to a case study.     

我们共同的目标：应对气候变化

叙述了美国政府将要采取以可靠的科学作为行动依据、建立清洁能源经济推动技术进步、在美国国内采取必要的行动、建立更强大的全球合作关系、推动发展中国家合作伙伴的参与以及帮助最贫困、最易受到影响的发展中国家适应气候变化、努力向前推进世界能源体系转型等措施,实现应对全球气候变化的共同目标,介绍了美国在建设碳循环监测网络、开展极度冰川调查、开发利用风能和农村能源、提高燃油效率限制汽车尾气排放、实施隔热防寒援助项目、逐步取消对化石燃料的补贴、研制碳排放量追踪工具、推进减少氢氟碳化物、开发新型监测与观察手段、组织沿海气候变化课程的情况。     

An optimization method to find the thermodynamic limit on enhancement of solar thermal decomposition of methane

An optimization approach to enhancing the solar thermal decomposition of methane (TDM) reaction process based on the fluid flow pattern reconstruction is proposed. The sum of entropy generations due to TDM reaction and heat convection in the process is shown to tend to its maximum when the performance of the reaction is enhanced, and thus, is used as the criterial to optimize the velocity field of the fluid. This optimization problem is solved by the calculus of variations method. The obtained flow pattern is shown to be able to give the conditions to achieve the optimally enhanced TDM process. As the sum of the entropy generations tends to its extremum, the solution found by the optimization can be known as the thermodynamic limit for the TDM process enhancement. The obtained flow pattern can then be used to inspire the design of internal structures of the solar TDM reactor.     

Analysis of mechanism of Nafion® conductivity change due to hot pressing treatment

In previous work, the authors observed that multiple hot-pressing cycles of Nafion 212 prior to Proton Exchange Membrane Fuel Cell (PEMFC) operation was found to result in significant performance gains. In order to further explore this effect, Nafion 212 samples were subjected to various thermal treatments and then to various analytical techniques in order to probe whether changes to the membrane contributed to these performance gains in a substantial way. Electrochemical Impedance Spectroscopy (EIS) measurement sought to validate that the treatment caused a proton conductivity change. Thermogravimetric Analysis (TGA) and Fourier Transform Infrared Spectroscopy (FTIR) measurements were implemented to determine whether chemical changes in the membrane occurred. Results suggest that the hot pressing treatment causes a significant effect in the electrical properties of Nafion 212, however the physical change that occurs in the polymer is not chemical in nature. Further analysis attempts to support the idea that the change in proton conductivity is due to water channel reconfiguration in the membrane, activated by elevated temperature and compressive stress at the glass transition temperature of the Nafion 212.     

The effect of magnetic and optic field in water electrolysis

Hydrogen production via water electrolysis was studied under the effect of magnetic and optical field. A diode solid state laser at blue, green and red were utilized as optical field source. Magnetic bar was employed as external magnetic field. The green laser has shown a greatest effect in hydrogen production due to its non-absorbance properties in the water. Thus its intensity of electrical field is high enough to dissociation of hydronium and hydroxide ions during orientation toward polarization of water. The potential to break the autoprotolysis and generate the auto-ionization is the mechanism of optical field to reveal the hydrogen production in water electrolysis. The magnetic field effect is more dominant to enhance the hydrogen production. The diamagnetic property of water has repelled the present of magnetic in water. Consequently the water splitting occurs due to the repulsive force induced by the external magnetic field. The magnetic distributed more homogenous in the water to involve more density of water molecule. As a result hydrogen production due to magnetic field is higher in comparison to optical field. However the combination both fields have generated superior effect whereby the hydrogen yields nine times higher in comparison to conventional water electrolysis.     

发动机试验室技术发展及建设思路

为了实现汽车行业规划发展目标,加大发动机研发投入是自主品牌研发的重点。开发大量发动机机型需要与之配套的发动机试验手段,来试验、验证所设计的技术指标,如何建设符合工艺使用要求的现代化发动机试验室,是各汽车公司需要解决的新课题,本文着重介绍了新技术阶段发动机试验室技术的发展及建设思路。