考虑配电网电压调节的分布式电源准入功率极限计算

随着分布式电源的大力发展，其对原有系统产生很大影响。分析了有载调压变压器分接头发生调节振荡的条件。讨论了分散电源的接入对变压器分接头对母线电压灵敏度 aVt 这一重要参数的影响，指出了分散电源的接入有可能使变压器分接头发生调节振荡，进而得出了考虑振荡约束的准入功率极限模型。最后运用112节点系统的算例证明了模型的有效性。     

含分布式电源配电网潮流问题的解决策略

研究了分布式发电系统接入电网的数学模型,对常见的几种分布式电源的节点进行了划分,归结为PQ节点,PV节点和P-Q（V）节点。在此基础上,基于MATLAB的计算功能,利用前推回代潮流算法原理,对有分布式电源接入的配电网系统进行潮流计算,计算过程采用改进的算法,最后对所提出算法的计算速度、收敛性等进行了分析。结果表明,该模型和方法能够快速、方便求解含多分布式电源的配电网潮流。     

计及气候、含风力发电的配电系统可靠性评估研究

分布式电源（distributed generation,DG）的接入使配电系统从辐射型的网络变为遍布中小电源和用户的互联网络,将对传统配电系统产生巨大的影响。而风力发电机（wind turbine generation,WTG）凭借其无污染、建造费用低、发电灵活等优势越来越多地被作为分布式电源接入配电网。但由于其自身功率输出随机性强的特点,对传统的分布式电源接入配电网带来了一定的影响。在充分考虑了气候因素对WTG功率输出和配电网馈线故障率的影响的同时,结合WTG的多状态模型与配电网孤岛运行方式,对含有气候因素并以风力发电机作为分布式电源的配电系统的可靠性评估情况进行了阐述,希望电网规划人员在选择最优方案时能够考虑由上述因素带来的影响。     

考虑相间短路影响的分布式电源准入容量计算

在分布式发电的初期阶段，如何在保持现有保护协调性的前提下接入最大容量的分布式电源是面临的首要问题。针对此问题，建立了乐观和保守估计下的准入容量数学模型，介绍了至少准入容量的计算方法。最后，结合杭州电力局配电网数据，推算了一个配电线路所能接入的分布式电源的准入容量，以证明所述数学模型的有解性、合理性。     

分布式发电对配电网电压分布的影响

靠近负荷中心的分布式发电系统对配电网有着多方面影响。文中研究了分布式电源接入放射状链式配电网络前后负荷节点电压的变化。针对开式配电网，运用潮流程序进行多分布式电源接入后电压分布的计算。提出专门评价节点电压前后变化的指标。结合分布式电源出力变化、接入位置变化以及与线路电压调节配合的试验，全面总结了分布式电源在配电网中接入位置、出力限制等方面的运行规律。研究结果表明只有合理正确运用分布式电源，才能真正发挥电压支撑作用。     

基于降低风力机叶片损伤的风电场优化调度

叶片是风电机组的核心部件之一,占风机总成本的20%,是影响风电机组运行寿命的重要因素。通过对叶片在几种不同载荷工况下叶根材料破坏时循环次数的计算,再结合线性累积损伤理论,得到了不同工况下的叶片损伤量。在同时考虑了风电机组叶片损伤、启停次数以及功率控制要求的条件下,建立了风电场的多目标调度模型;并采用二进制遗传算法(BGA)对该模型予以优化,获得了风电机组启停组合和目标功率值。在此基础上,再结合实际算例来验证该算法,通过合理的机组调度,实现了在保证输出功率控制要求的同时,来优化风电机组的启停、改善风电机组的运行寿命以及减少风电场电力系统的运行成本。     

配网侧接入电源对负荷建模的影响

研究了配网侧接入电源对负荷建模的影响。发现当配网侧电源的发电容量逐渐增大时，原有的感应电动机并联恒阻抗、恒电流、恒功率（ZIP）模型的负荷模型将不再能很好地反映该区域的负荷特性，进而提出了一种新的负荷模型结构———异步发电机并联ZIP模型。通过仿真计算，验证了该新负荷模型的有效性，并进一步统一了上述2种负荷模型，称为异步机并联ZIP负荷模型。     

SKT-1型多微机控制、调节装置

SKT-1型控制、调节装置是一个分布式的多微机系统，能实现对电厂机组启停、开关操作、 机组功率闭环调节的集中控制，具有较高的可靠性和可利用率。 本文介绍了该装置的系统结构、工作原理、软件设计以及调试过渡。     

分布式发电作为备用电源的优化配置

通过计算不同分布式电源配置方案的年发电费用、用户停电损失、环保成本,建立了综合经济性、可靠性、环保性评估的分布式电源优化配置模型。基于电力不足概率对分布式电源配置方案进行可靠性评估,给出不同可靠性目标下的最优配置方案,并对用户不同停电成本对配置方案的影响进行了敏感性分析。同时,将分布式电源对环境的影响也纳入了优化评估中,考虑了SO2 和NOx 等各种污染气体的排放特性,以及不同地区环保成本差异对优化配置结果的影响。算例分析表明,该模型能够全面评估各种分布式电源的性能,并针对不同用户的可靠性和环保要求提出了最优配置方案。     

一种用于分布式发电系统的有功功率补偿模型

针对高穿透率的分布式发电系统将给电网带来的电能质量等一系列问题,提出一种用于并网分布式发电系统的有功功率补偿模型。该模型利用兼具多种储能技术优点的混合储能系统来补偿分布式电源产生的功率波动,具有补偿功率高、储能容量大的性能优势。模型中提出了基于能量预测的动态能量优化算法以提高储能设备的利用效率,利用模糊控制得出储能设备的补偿功率给定值。仿真分析验证了该模型的有效性,在提高补偿性能的同时可观地降低了储能设备的容量需求,从而节约了成本,具有实际应用价值,可用于改进现有储能系统。     

Call for Papers

正As the eldest and most distributed professional journal of water industry,Water Wastewater Engineering(W WE)gained very wide acceptance from the colleagues working in this field in this country since start publication in 1964.Now it is administrated by the Ministry of Construction of the People’s Republic of China and sponsored by the China Civil Engineering Society etc.     

SPATIAL AND TEMPORAL WATER QUALITY VARIABILITY IN AQUATIC HABITATS OF A CULTIVATED FLOODPLAIN

The floodplains of lowland rivers contain diverse aquatic habitats that provide valuable ecosystem services but are perturbed when intensively cultivated. Hydrologic, water chemistry and biological (fish) conditions in five aquatic habitats along the Coldwater River, Mississippi, were measured for more than 4 years: the river, two severed meanders that functioned as backwaters, a managed wetland and an ephemeral channel draining cultivated fields. Off‐channel habitats were connected to downstream regions 0.10% to 32% of the dry season and 24% to 67% of the wet season. The median temperatures for the five monitored sites ranged from 18°C to 23°C, the median total solids concentration for all sites was 135 mg L^?1, the median total phosphorus was 0.29 mg L^?1 and the median total nitrogen was 1.56 mg L^?1. Chemical and physical water quality displayed strong seasonal differences between the wet winter/spring and the dry summer/fall periods so that temporal variation consisted of gradual seasonal trends superimposed on strong diurnal variations. All off‐channel habitats exhibited periods of hypoxia and temperatures >30°C during the dry season. Between‐site gradients of water and habitat quality were strongly coupled to water depth and runoff loading. The rehabilitation of one backwater by increasing water depth and diverting agricultural runoff was associated with improved water quality and fish species richness relative to an adjacent untreated backwater. The diversion of polluted runoff and the use of water control structures to maintain greater water depth were observed to be effective management tools, but the former reduces the water supply to habitats that tend to dry up and the latter reduces connectivity. Published in 2011 by John Wiley & Sons, Ltd.     

Spatio‐temporal variation of gross CO2 and CH4 diffusive emissions from Australian reservoirs and natural aquatic ecosystems,and estimation of net reservoir emissions

Carbon dioxide (CO₂) and methane (CH₄) diffusive emissions were measured during two field surveys in Queensland and Tasmania, Australia, using the floating chamber method. Bubbling and degassing emissions in 2010 were estimated in Koombooloomba Dam reservoir using only inverted funnels and gas concentrations, respectively. A total of 14 reservoirs and 16 rivers and lakes were sampled from 2006 to 2010. Spatial variation was substantial within each water body, as well as between them. The main drivers of diffusive emission variation were physiographic region and climate, with a clear demarcation being observed between diffusive emissions from tropical Queensland and temperate Tasmania, and between the humid West Coast Range (Tasmania) and dry Central Plateau (Tasmania). Higher CO₂ and CH₄ diffusive emissions were observed during the dry season, when long water residence times would promote organic matter degradation. Estimated total gross emissions, including diffusive, bubbling and degassing emissions, for Koombooloomba Dam reservoir were about 1.5 × 10⁶ t CO₂eq km² per year, or 24 × 10⁶ t CO₂eq per year. This corresponds to a plant emission factor of 3.18 kg CO₂eq MWh^?1. Using an estimate of terrestrial emissions derived from literature data for the Tully River catchment area, rough estimated net emissions from the catchment area are about 44 kt CO₂eq per year, or 5.83 kg CO₂eq MWh^?1, which is in the lower range of the studied reservoirs.     

库水波动下库岸边坡地下水浸润线解析解及误差分析

解析法是库岸边坡地下水浸润线计算中便于实际应用的方法,但该方法须基于若干假定并对潜水运动基本方程线性化后才能求解。针对各假定和线性化过程建立不同的地下水渗流数学模型,用解析法和有限元法解答上述数学模型,分析各误差大小及其规律。结果表明：库岸垂直处理带来的误差要小于方程线性化处理和不考虑非饱和渗流带来的误差,而且它们都随渗透系数变大而减小;在三峡库区库水调度情况下,假定库水位等速变化带来的误差对大多岸坡而言可以忽略;计算库岸边坡地下水浸润线时,解析法只适用于水位变化幅度相比含水层厚度较小,且几何边界规则、岩土结构简单、岩土体渗透性较好时的情况。     

Changes in Summer Irrigated Crop Area and Water Use in Southeastern Turkey from 1993 to 2002: Implications for Current and Future Water Resources

Changes in summer irrigated cropland acreage and related water use are estimated from satellite remote sensing and ancillary data in semi-arid Southeastern Turkey where traditionally dry agricultural lands are being rapidly transformed into irrigated fields with the help of water from the Euphrates-Tigris Rivers. An image classification methodology based on thresholding of Landsat NDVI images from the peak summer period reveals that the total area of summer irrigated crops has increased three-fold (from 35,000 ha to over 100,000) in the Harran Plain between 1993 and 2002. Coupled analysis of annual irrigated crop area from remote sensing and potential evapotranspiration based estimates of irrigation water requirements for cotton indicate a corresponding increase in agricultural water use from about 370 million cubic meters to over one billion cubic meters, a volume in accordance with the state estimates. These estimates have important implications for understanding the rapid changes in current agricultural withdrawals in Southeastern Turkey and form a quantitative basis for exploring the changes in future water demands in the region. For example, expansion of irrigated lands have led to a steady decrease in potential evaporation due to increased roughness and decreased humidity deficit in the Harran Plain. Assuming that the changes in future evaporation conditions will be of similar nature, water use for irrigation is expected to decrease over 40 percent in future irrigation sites. Incorporating this decrease in overall planning of the irrigation projects currently under construction should lead to improved management, and by extension, sustainability of water resources in the region.     

Serial discontinuities in a Rocky mountain river. II. Distribution and abundance of trichoptera

River regulation in the headwaters and middle reaches of the Gunnison River, Colorado, significantly altered distributions and abundances of Trichoptera fauna. Twenty-five species were collected from mainstream samples, with the greatest species richness occurring at an unregulated, rhithron segment above the central reach dams. At sites immediately below the three hypolimnial-release dams and a reregulation dam, species richness was reduced 35–90 per cent and abundance > 95 per cent. Net-spinning caddisflies were the dominant trichopterans at unregulated sites; Arctopsyche grandis in the upper reaches (218 organisms, 586 mg dry mass m^?2) and Hydropsyche cockerelli, H. occidentalis and Cheumatopsyche pettiti in the lower river (9041 total organisms, 6621 mg m^?2), downstream from the last dam. The observed distributional pattern of low trichopteran densities in dam tailwaters and high hydropsychid densities at sites 60–80 km below the central reach dams is a classic expression of continuum resets and adjustments in response to stream regulation as predicted by the Serial Discontinuity Concept.     

浅谈优化Vray渲染在制作三维场景的应用研究

用Vray三维渲染引擎来渲染三维场景,其质量和速度是由一些影响因素和参数设置决定的,不同的参数和因素,可以得出不同的三维渲染效果.因此,分析、优化三维渲染质量和速度的影响因素,正确、合理的选择参数对提高Vray最后渲染阶段的质量和速度非常重要.     

固结、渗流和沉积控制方程研究

本文从两相流体动力学的守恒方程出发，考虑固相、液相的相对运动，推导了可以考虑场的不均匀性和流体压缩性的统一形式的控制方程，并对方程所基于的物理概念和相互联系进行了必要的分析。通过对方程适当形式的表达，可导出用于大、小变形固结、渗流和沉积的简化方程，显示了在不同领域的三个理论存在一定的统一性。方程推导过程并未对本构关系加以限制，适用范围较广。依据实际问题的要求，作了不同形式的简化。     

四川省及重庆市中型水电站效益分析

该文分析了四川省及重庆市几座中型水电站的调查材料表明：四川省及重庆市中型水电站不仅在川渝主网和地方电网中起着很大的作用，并具有巨大的社会效益，同时还有综合利用效益，说明修建中型水电站的优越性．     

Site modelling methods for detecting hydrologic alteration of flood frequency and flood duration in the floodplain below the carlyle dam,lower Kaskaskia River,Illinois, USA

Reports concerning the influence of dams on river hydrology vary among researchers, interest groups and government agencies. These often contradicting statements may occur because changes in hydrology caused by dams are distinct for each dam and river watershed. The objective of this research was to use site specific techniques to determine if the 1967 installation of the Carlyle Dam, lower Kaskaskia River, Illinois, altered flood frequency and duration within the forested floodplain located below the dam. Results indicated a decrease in flood duration and frequency, and a decrease in annual flood frequency variation at a site 6.4 km below the dam. Pre‐dam versus post‐dam differences in flood frequency and duration at the site 32.2 km below the dam were related to climate rather than dam effects. Although dam impacts are a concern, this research shows that distance downstream from the dam and downstream tributary and watershed characteristics should be considered before assuming that the dam has changed hydrologic parameters for portions of rivers. This research also indicates that areas of the lower Kaskaskia River may still maintain hydrologic ecological integrity, and could be targeted for restoration and adaptive management purposes. Hydrologic modelling combined with river gage and on‐site well measurement techniques presented in this study could provide detailed flood frequency and duration information for land use, sociological and geomorphological questions in focus areas within river floodplains. Copyright © 2008 John Wiley & Sons, Ltd.