电网厂站端自动电压控制技术应用研究

自动电压控制(Automatic Voltage Control,以下简称AVC)保证电网节点电压合格率,对电网稳定提供有效支撑。笔者结合厂站端AVC子站控制原理,对厂站端AVC系统控制策略进行了分析,并进行安全约束功能设计,最后提出厂站端AVC动态与联调的调试技术要求,对抽水蓄能电站等电网厂站端AVC安全约束功能设计与AVC调试技术应用具有指导意义。     

大渡河沙湾水电站AVC功能的设计及实现

电压质量是衡量电能质量的主要指标之一,自动电压控制(AVC)是水电站安全运行和经济运行的必要手段。根据四川电网自动电压控制(AVC)系统建设的要求,介绍了大渡河沙湾水电站AVC系统的功能特点、调节模式、控制模式、AVC系统无功分配值计算、无功分配原则及AVC系统安全约束条件以及闭环试验的结果与分析。     

中低压变电站电压无功调节的研究

由于电压在整个电网中的重要性，电压无功控制越来越引起注意。该文分析了电压与无功的 关系后，提出了两种AVC模型——软件AVC和硬件AVC，详细介绍了硬件AVC的硬件原理及软件 框图，并分析了AVC的闭锁条件。     

基于控制模式的地区电网AVC系统设计及应用

介绍了一种新的用于地区电网的自动电压控制（AVC）系统，该系统遵循无功在高电压水平下分层分区平衡原则，通过协调控制，全面实现AVC的各种控制目标。首先提出了区域电压控制、就地电压控制和区域无功控制3种控制模式，分析了各控制模式时间解耦并协调配合的方法；然后介绍了与能量管理系统（EMS）一体化设计的AVC系统的设计与实现。新开发的AVC系统已投入多个地区电网实际运行，结果表明AVC系统对提高电网电压合格率、优化无功、降低网损有明显的效果，并大大减轻了运行人员的劳动强度。     

桂林电网AVC系统应用及其改进措施

基于无功分层分区控制和无功电压区域控制的原则,提出一种地区电网AVC系统设计方法.设计方案完成了主站系统搭建设计和控制策略分析,通过AVC系统安全策略,实现了全网电压合格和无功优化.文章概述了电力系统无功电压控制的问题现状、AVC研究现状及电网动态电压稳定的策略,桂林电网无功平衡和电压控制的研究,以及应用一年来的电网运行情况,分析了存在问题及其相关的解决措施,并提出了下一步桂林电网无功电压调控的目标等.     

电站AVC控制设计与实现

通过分析现阶段电站电压调节的现状,阐述了电站投入自动电压控制(AVC)的必要性,并详细介绍了电站AVC的原理、AVC设计(包括硬件、模式设置、无功分配原则)、实现的功能及非正常工况处理等.     

柘溪电厂AVC策略及实现

水电厂自动电压控制(AVC)的总体目标是根据电网要求,考虑电厂及机组的运行限制条件,使电厂电压稳定安全.文中首先介绍电厂侧AVC系统的一般要求,然后以柘溪电厂为例,具体阐述包括功能约束和保护闭锁的AVC策略,在PQ曲线限制的实现和提高电压调整精度方面进行了重点分析,实验表明考虑无功进相的AVC系统切实可行,调节跟踪精度在0.4 kV以内.     

基于子站级的龙滩水电厂AVC控制策略与安全约束条件构建

主要介绍基于子站级的龙滩水电厂AVC自动电压控制系统的工作模式、控制策略和安全约束条件,通过分析、研讨并总结出一些AVC系统构建经验,以促进大型发电厂电压自动化调节控制技术水平不断提高。     

重庆电网水电厂自动电压控制策略及实现

基于重庆电网电压控制的特殊要求和电厂自动电压控制(AVC)系统的一般配置,针对重庆电网运行方式复杂的特点,给出了变增益的AVC控制策略.具体方法包括防止通信中断的指令编码方式和在电网发生大变动时减小调节增益的方式.实验表明,给出的AVC控制策略切实可行,可从电厂的角度进一步保证电网的电压控制安全.     

紫坪铺水电厂自动电压控制系统

详细介绍了紫坪铺水电厂自动电压控制(AVC)系统的功能、控制原理、保证AVC系统安全稳定运行的措施及AVC投运半年后出现的问题和解决办法。     

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.     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Serial discontinuities in a Rocky mountain river. I. Distribution and abundance of plecoptera

Samples were taken year-round at eleven sites along the altitudinal profile (2900-1400 m a.s.l.) of the Gunnison River, a 329 km tributary of the Colorado River, to document the distribution of the Plecoptera and to evaluate responses to hypolimnial-release dams in the headwaters and middle reaches. Twenty-two species were present, with the greatest species richness occurring in an unregulated segment upstream of the middle reach dams; average nymphal biomass over the study period (175 organisms, 395 mg dry mass m^?2) was also greatest in this segment. Only four species (58 organisms, 48 mg m^?2) were present in the tailwaters of the headwater dam and values were greatly reduced (nine species; 35 organisms, 180 mg m^?2) below the middle reach dams. The stonefly community recovered ca. 80 km downstream from the last dam (15 species; 244 organisms, 250 mg m^?2), apparently in response to natural resetting of environmental conditions corresponding to those above the middle reach dams. At the most downstream site (11) only four species (four organisms, 16 mg m^?2) were present. The observed distributional pattern is a classic serial discontinuity in response to hypolimnial stream regulation in a temperate latitude river.     

Impacts of Microcystis on algal biodiversity and use of new technology to remove Microcystis and dissolved nutrients

Cyanobacteria often dominate eutrophic lakes, outcompeting green algae that are required by fish and zooplankton. This study was undertaken to ascertain the impact of the cyanobacterium, Microcystis, on algal biodiversity. Under laboratory conditions, we found that the presence of Microcystis decreased phyla richness by 58%, phyla evenness by 47%, genera richness by 66% and genera evenness by 51%. Analysis by mixed anova s demonstrated a significant interaction between treatment and time and confirmed a significant reduction in richness and evenness of phyla and genera. We also conducted a phosphate restriction assay on the algae in Mason Lake (Irvine, CA, USA) and found that the threshold needed for algal growth there was 0.02 mg L^?1 PO₄. A pilot study was then conducted to test the effectiveness of the Blue Pro? water treatment facility in removal of this colonial organism from Mason Lake, in addition to removal of dissolved nutrients required for its growth. We measured a 97% reduction in Microcystis cells, a 72% reduction in chlorophyll‐a, and a 96% reduction in phosphate after just one 10 min cycle through the unit. Our study demonstrated that removal of Microcystis colonies may allow green algae to increase in numbers. This may improve algal biodiversity, which will benefit zooplankton and fishes.     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

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。     

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.     

簸箕李引黄灌区水沙分布及优化调度的经验

灌区利用水沙观测所取得的资料和试验数据，运用水沙运动力学理论，总结分析和揭示了灌区水沙分布的规律和特点。在此基础上，结合灌区的实际运行情况，围绕减少骨干渠道的淤积进行探讨、研究，进而，优化水沙调度方案。该方案实施后，骨干渠道减旅伴效果明显，取得了成功的经验。     

小湾水库大坝防渗面板及其裂缝的加固处理

小湾水库大坝防渗面板整体抗渗性能差,且存在多条裂缝,通过对面板钢丝网喷涂丙乳砂浆加固处理及其裂缝修补,大坝渗漏量明显减少,且左岸上灌浆廊道内及大坝下游坝面92～93 m高程下廊道入口处原有小股射流全部消失.