一种具有非线性动力学模型的智能电网快速分布式控制

将储能技术作为新兴调节功率的手段引入智能电网,为保障电网平稳运行提供新的思路.考虑到电力系统的暂态稳定问题与蜂拥控制问题的相似性,针对电力系统遭遇故障后恢复暂态稳定的控制问题,提出一种新的基于蜂拥算法的非线性分布式控制方案,该方案利用电机动力学方程中非线性项与系统频率之间的关系,引入系统状态反馈项以加快系统恢复暂态稳定性,通过外部储能设备对系统故障实施控制.最后,将该控制器应用在IEEE新英格兰39节点电力系统模型中,仿真结果验证了该控制器具有快速性、可实施性,并进一步验证了所设计的控制器在储能设备低容量条件下的有效性.     

基于滑模控制的含风储多域电力系统负荷频率控制

建立含风储多域互联电力系统负荷频率控制(LFC)模型,同时考虑系统参数不确定性、储能系统和传统机组控制信道延时问题.为提高系统鲁棒性,降低储能系统的容量配置,针对含风储的LFC模型,设计滑模负荷频率控制器,并提出滑模负荷频率控制器和储能协调的控制策略.算例分析表明,所提出的协调控制策略在新能源大规模渗透和系统负荷波动情况下能够有效减小系统频率偏差和区域控制偏差,同时降低储能系统的配置容量,提高电力系统安全稳定运行的经济性.     

基于神经网络的电力系统暂态稳定分布式自适应控制

针对电力系统中普遍存在的系统非线性和参数不确定性等问题,提出一种基于径向基函数神经网络(RBFNN)的分布式自适应控制器,以提高多机电力系统的暂态稳定性.利用基于RBFNN的方法对系统中的未知非线性项和外部扰动进行补偿,设计相应的自适应参数估计方法,逼近未知非线性项的理想权值矩阵.该策略基于多智能体框架,分布式控制器通过通信网络接收测量装置测量的实时数据,并控制储能装置动作,使受到扰动后各发电机能够迅速实现频率同步.利用李雅普诺夫稳定性理论,证明所提出的分布式控制方法的收敛性.最后,通过仿真研究验证所提出的分布式控制方法的有效性.     

基于事件触发的非线性多智能体系统的固定时间分群一致性

结合事件触发控制方法研究非线性多智能体系统的固定时间分群一致性问题.提出一种非线性分布式事件触发分群一致性控制协议,并给出状态信息触发控制器更新的条件.该控制协议不受入度平衡条件限制,且只需自身状态信息与邻居智能体进行通信即可在固定时间内快速实现分群一致性.系统收敛时间与智能体的初始状态无关,可有效降低系统控制器更新频率和系统的资源消耗.结合代数图论、矩阵分析及Lyapunov稳定性理论,证明在所提出协议作用下,多智能体系统在固定时间内能够实现分群一致性,且不存在Zeno行为.最后,通过仿真实例检验了理论结果的可行性.     

隐式改进欧拉法在暂态稳定分析中的应用

电力系统安全运行的关键之一是可靠的暂态稳定分析.在利用牛顿法潮流计算得出系统的初始运行状态后,采用隐式改进欧拉法对系统暂态稳定计算中的发电机模型进行处理,以避免暂态计算中的交接误差,提高计算精度.同时,通过计算得到发电机功角摇摆曲线的分布特性,判断出系统的暂态稳定性.仿真结果表明,该方法能有效地判断出系统的暂态稳定性,在程序设计上也具有较好的可扩展性和灵活性.     

静止无功补偿器的自适应逆推无源反馈控制设计

通过将耗散系统理论和自适应逆推(adaptive backstepping)非线性控制算法相结合, 克服了无源反馈方法只能为输入输出相对阶为1的系统设计控制律的限制, 为带有静止无功补偿器的单机无穷大电力系统设计了鲁棒自适应控制器. 设计中兼顾了系统遭受不确定扰动以及阻尼系数难以精确测量情况下控制器的鲁棒性和自适应能力. 理论分析证明所提算法可保证系统内所有状态变量一致有界且渐近稳定, 系统误差全局渐近稳定. 仿真结果也表明, 所提算法使系统母线电压, 发电机功角以及转子角速度的暂态响应性能优于传统逆推算法, 系统误差迅速收敛至零, 与理论证明结果一致.     

汽轮发电机主汽门开度的非线性最优预测控制

基于非线性最优预测控制理论,提出了一种汽轮发电机主汽门开度非线性预测控制器的设计方法.通过单机无穷大系统的建模分析,导出具有闭型解析解的控制律,避免了在线优化带来的大量计算负担,从而满足实时控制的要求.控制器的输入信号均选为发电机组的当地测量量,便于工程实现.仿真结果表明,该控制器能有效地提高电力系统的暂态稳定及改善其动态品质.     

电力系统暂态稳定性的数值仿真研究

由于系统暂态失稳引发的大停电等事故频繁,所以加强对电力系统暂态稳定分析的研究具有重要意义。数值计算是系统仿真的重要手段,计算结果可以为系统的规划、设计、运行、分析、控制等提供依据。首先介绍了电力系统暂态稳定分析的主要方法,并利用时域法讨论了单机无穷大系统的暂态稳定性。其次,采用龙格库塔方法求解离散发电机转子的运动方程,得到了系统δ-t曲线。最后,运用上述方法计算实际问题,结果表明暂态稳定分析与初始运行方式、故障点位置、故障切除时间、故障后状态有关。因此,在实际生产中应注意结合上述特点减少事故发生。     

计及螺旋桨负载的船舶电力系统协调控制设计

推进负载对船舶电网的暂态稳定性影响是船电系统的主要特征之一.本文基于非线性鲁棒L2干扰抑制控制方法,研究了具有螺旋桨负荷的船舶电力系统中的励磁与调速的协调控制问题,在充分分析了柴油发电机组的非线性数学模型及其螺旋桨负载的相互耦合的非线性动态结构特性的基础上,提出backstepping控制技术与L2干扰抑制相结合的综合协调控制策略来设计控制器.该控制器在保证系统稳定的条件下,有效地抑制干扰对发电机系统电压和频率的影响.仿真表明,在给系统突加螺旋桨负载的情况下,该控制器能有效地抑制负载对系统性能的影响,验证了控制器的有效性.     

基于等速趋近律的滑模负荷频率控制设计

针对单域电力系统,提出了基于等速趋近律的滑模负荷频率控制器设计策略。首先通过矩阵初等变换将原系统转换成标准型,基于标准型设计切换面,利用极点配置选择适当的切换函数,保证系统具有稳定的滑动模态;其次基于等速趋近律设计滑模控制器,使得电力系统状态在有限时间内到达滑模面;最后利用Matlab进行仿真研究,将传统的基于不等式趋近律设计的滑模控制器和提出的基于等速趋近律设计的滑模控制器,分别对理想工作状态下和发电机出力受约束(GRC)情况下的电力系统进行仿真比较,可以看出设计的滑模负荷频率控制器具有较好的频率偏差抑制效果。     

Only connect: teaching, technology and telesis

Abstract This paper describes an approach to the design of interactive multimedia materials being developed in a European Community project. The developmental process is seen as a dialogue between technologists and teachers. This dialogue is often problematic because of the differences in training, experience and culture between them. Conditions needed for fruitful dialogue are described and the generic model for learning design used in the project is explained.     

European Community policy and the market

Abstract This paper starts with some reflections on the policy considerations and priorities which are shaping European Commission (EC) research programmes. Then it attempts to position the current projects which seek to capitalise on information and communications technologies for learning in relation to these priorities and the apparent realities of the marketplace. It concludes that while there are grounds to be optimistic about the contribution EC programmes can make to the efficiency and standard of education and training, they are still too technology driven.     

一种自适应子融合集成多分类器方法

融合集成方法已经广泛应用在模式识别领域,然而一些基分类器实时性能稳定性较差,导致多分类器融合性能差,针对上述问题本文提出了一种新的基于多分类器的子融合集成分类器系统。该方法考虑在度量层融合层次之上通过对各类基多分类器进行动态选择,票数最多的类别作为融合系统中对特征向量识别的类别,构成一种新的自适应子融合集成分类器方法。实验表明,该方法比传统的分类器以及分类融合方法识别准确率明显更高,具有更好的鲁棒性。     

Avoiding semantic and temporal gaps in developing software intensive systems

Development of software intensive systems (systems) in practice involves a series of self-contained phases for the lifecycle of a system. Semantic and temporal gaps, which occur among phases and among developer disciplines within and across phases, hinder the ongoing development of a system because of the interdependencies among phases and among disciplines. Such gaps are magnified among systems that are developed at different times by different development teams, which may limit reuse of artifacts of systems development and interoperability among the systems. This article discusses such gaps and a systems development process for avoiding them.     

Designing economic np control charts: A programmed simulation approach

This paper presents control charts models and the necessary simulation software for the location of economic values of the control parameters. The simulation program is written in FORTRAN, requires only 10K of main storage, and can run on most mini and micro computers. Two models are presented - one describes the process when it is operating at full capacity and the other when the process is operating under capacity. The models allow the product quality to deteriorate to a further level before an existing out-of-control state is detected, and they can also be used in situations where no prior knowledge exists of the out-of-control causes and the resulting proportion defectives.     

The development of robot art

Going through a few examples of robot artists who are recognized worldwide, we try to analyze the deepest meaning of what is called “robot art” and the related art field definition. We also try to highlight its well-marked borders, such as kinetic sculptures, kinetic art, cyber art, and cyberpunk. A brief excursion into the importance of the context, the message, and its semiotics is also provided, case by case, together with a few hints on the history of this discipline in the light of an artistic perspective. Therefore, the aim of this article is to try to summarize the main characteristics that might classify robot art as a unique and innovative discipline, and to track down some of the principles by which a robotic artifact can or cannot be considered an art piece in terms of social, cultural, and strictly artistic interest. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Explanation and prediction: an architecture for default and abductive reasoning

Although there are many arguments that logic is an appropriate tool for artificial intelligence, there has been a perceived problem with the monotonicity of classical logic. This paper elaborates on the idea that reasoning should be viewed as theory formation where logic tells us the consequences of our assumptions. The two activities of predicting what is expected to be true and explaining observations are considered in a simple theory formation framework. Properties of each activity are discussed, along with a number of proposals as to what should be predicted or accepted as reasonable explanations. An architecture is proposed to combine explanation and prediction into one coherent framework. Algorithms used to implement the system as well as examples from a running implementation are given.     

Three Process Perspectives: Organizations, Teams, and People

This paper provides the author's personal views and perspectives on software process improvement. Starting with his first work on technology assessment in IBM over 20 years ago, Watts Humphrey describes the process improvement work he has been directly involved in. This includes the development of the early process assessment methods, the original design of the CMM, and the introduction of the Personal Software Process (PSP)^SM and Team Software Process (TSP){^SM}. In addition to describing the original motivation for this work, the author also reviews many of the problems he and his associates encountered and why they solved them the way they did. He also comments on the outstanding issues and likely directions for future work. Finally, this work has built on the experiences and contributions of many people. Mr. Humphrey only describes work that he was personally involved in and he names many of the key contributors. However, so many people have been involved in this work that a full list of the important participants would be impractical.     

基于复小波噪声方差显著修正的SAR图像去噪

提出了一种基于复小波域统计建模与噪声方差估计显著性修正相结合的合成孔径雷达(Synthetic Aperture Radar,SAR)图像斑点噪声滤波方法。该方法首先通过对数变换将乘性噪声模型转化为加性噪声模型,然后对变换后的图像进行双树复小波变换(Dualtree Complex Wavelet Transform,DCWT),并对复数小波系数的统计分布进行建模。在此先验分布的基础上,通过运用贝叶斯估计方法从含噪系数中恢复原始系数,达到滤除噪声的目的。实验结果表明该方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪效果。     

How do children do mathematics with LOGO?

Abstract  This paper considers some results of a study designed to investigate the kinds of mathematical activity undertaken by children (aged between 8 and 11) as they learned to program in LOGO. A model of learning modes is proposed, which attempts to describe the ways in which children used and acquired understanding of the programming/mathematical concepts involved. The remainder of the paper is concerned with discussing the validity and limitations of the model, and its implications for further research and curriculum development.