风力发电机组变桨距控制器的研究

针对风力发电机组在高风速下运行时输出功率不稳定的问题,提出了模糊自适应PID变桨距控制器的设计方案。以机组实际输出功率值与额定功率值的偏差及其偏差的变化率作为控制器的输入变量,确定模糊语言和隶属函数,基于Matlab/Simulink上对整个系统进行仿真。仿真结果表明模糊自适应PID控制器具有很好的控制精度和鲁棒性。     

贯流式机组综合型模糊神经网络智能控制研究

针对贯流式水力机组带孤立负荷时难以稳定的特点，在以串级的三维模糊控制器为基础，引入2个反馈环节作为并联校正，形成综合控制器的同时，以神经网络完成水轮机调节系统调节对象的辨识和控制器参数的在线学习，从而较为圆满地解决了贯流式水力机组带孤立负荷时的稳定控制问题。且控制器设计分块、分步、分层进行，结构清晰，参数设置简单，便于工程应用。     

基于改进BP网络的轴流式水轮机调节特性仿真

为了获得水力机组在小开度、小流量工况点下非线性特性数据,利用改进BP网络与MATLAB神经网络工具箱相结合的方法,将已知的水轮机综合特性曲线数据与边界约束点相结合,经网络自动"学习"训练可获得低效区的流量延拓、力矩延拓仿真曲面。改进BP网络模型可以大大地提高水轮机综合特性曲线数据处理的效率与精度,是研究水轮机控制系统的一种新的非线性建模仿真模型。     

多机系统的非线性自适应分散稳定控制

针对含有未知参数的励磁系统，提出了一种非线性自适应控制设计方法。通过递推方法得到了自适应控制策略，而且在控制策略中包含了对未知参数的动态估计，最后获得了多机系统的非线性自适应分散励磁控制策略的一般表达式。在控制策略中所有的变量都是可量测的，而且控制量只与本机组的状态量有关，与其他机组的状态量和输电网络的参数无关，因此控制策略具有分散性和适应性。在一个6机系统上的仿真结果表明了非线性自适应控制器的有效性。     

基于孤网下水轮机调速器参数自动切换方法的实现

乌鲁瓦提水电厂作为和田地区第一调频厂,由于机组运行组合发生变化,且各台机组参数均不相同,电厂在孤网下运行时可能会处于带基荷运行状态,无法及时对电网频率进行调整,失去调频厂的作用,常规情况下人工根据机组运行情况及时对参数进行调整,可以保证电厂处于调频状态,但该方法工作量大,非常繁琐.文中针对人工修改参数不便的问题提出了一种以可编程逻辑控制器(PLC)为控制核心,在孤网下自动对水轮机调速器参数切换的方法,详细介绍了实现该方法的系统硬件和软件的设计.     

水力发电机组的模糊神经网络参数自整定PID控制及仿真

为适应水电机组的复杂工况和高指标的控制要求,提出了一种水力发电机组的模糊神经网络参数自整定PID控制系统．即利用多层神经网络构建模糊自适应PID控制算法,通过神经网络自学习能力在线提取模糊控制规则。优化控制器隶属度函数,根据不同时刻的误差e和误差变化ec,利用模糊逻辑控制,在线自整定PID参数,进一步完善了PID控制器的性能,提高了系统的控制精度。仿真实验表明：该控制器明显地改善了控制系统的动态性能,能使系统达到满意的控制效果,对进一步应用研究具有参考价值。     

右江水电厂调速器建模试验

水电厂调速器建模试验是系统稳定分析计算的重要依据,同时可以考察机组调速器的性能,优化机组动态协调特性,介绍了对右江水电厂机组进行的静态和动态带荷的相关试验,并对试验结果进行了数据分析,为机组和电网安全稳定运行提供了依据.     

基于SIMULINK的水轮机调节系统非线性仿真模型研究

在实际计算及仿真时,机组数学模型中的非线性因素很难表示,运用SIMULINK建立可进行调保计算的可视化仿真模型可以很难好解决此问题,在建模时,利用水轮机的全特性建立其非线性模型,并考虑了调速器的限幅非线性因素,使计算结果较近似公式计算更精确,且该可视化模型的开放性和可移植性都较好,模型结构也易于修改和重构,可以很好的适应了各电站的调保计算,所以应用该可视化模型进行调保计算简单可行。     

某300 MW机组水轮机调节系统参数实测及建模分析

为提高电力系统稳定分析计算的准确性和电网调度对试验机组生产调度的科学性,对某300 MW混流式水电机组进行水轮机调节系统控制参数测试和建模分析。以试验机组水力机械特性和调速系统实际控制逻辑为依据,兼顾调节控制的死区、限幅、延时、非线性函数等因素导致的非线性特性和仿真计算的方便简约性,在MatLab/Simulink中对水轮机调节系统的电气控制、液压系统和原动机3个环节进行建模;针对原动机环节分别建立了电力系统分析综合程序通用模型和自定义模型;对模型参数进行了现场实测和仿真辨识,并对电力系统分析综合程序通用模型和自定义模型进行比较分析。结果表明自定义模型参数能更好地反映机组设备本身的动态响应特性。该模型的建立为水电机组电力稳定计算分析领域的完善和发展提供了参考。     

HVDC紧急功率支援自适应模糊控制器设计

研究了高压直流输电系统(HVDC)紧急功率支援控制的实现方法，提出了一种基于参数自适应模糊PID控制算法的HVDC紧急功率支援控制器，它可以根据两侧交流系统的运行情况、故障后的状态等信息，即时地决定最佳的支援功率值，并控制直流输电系统按照最佳支援功率值进行定值功率支援。该控制器基于确定模糊模型，构造模糊PID控制器，并引入确定性模糊调整规则对其进行参数自适应调整，整个控制器结构简单、稳定性强且实现容易。文中采用一个两区域系统对该控制器进行了时域仿真计算。仿真结果表明：投入该控制器后，交流系统在各种大干扰下的频率响应均表现出令人满意的特性。     

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。     

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。     

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.     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.