基于谱线插值FFT谐波电流检测的研究

提出了新型谱线插值FFT的谐波电流检测新方法,用于改善有源电力滤波器(APF)谐波检测的实时性和可靠性。新型谱线插值FFT主要是对检测波进行加余弦偶次幂窗,利用抽取幅值最大的频率附近的3根离散频谱确定谐波谱线的准确位置,可以得到谐波的幅值、相位和频率。基于该算法,通过多项式拟合的方式,提出了谐波修正的实用公式。仿真结果表明,该方法能够很好地抑制频谱泄露和栅栏效应,跟踪基波频率的变动,提高谐波的检测准确度。     

基于EL模型的海洋石油平台三相APF无源性控制

利用有源电力滤波器装置(APF)的非线性特性,提出一种基于欧拉-拉格朗日(EL)模型的三相并联型APF的无源性非线性控制方法.为了确保APF直流侧平均电压稳定在设定值,提高APF的谐波补偿精度,采用基于非线性PI控制的APF直流侧电压外环控制.Matlab仿真实验证明此方法控制的APF具有很好的谐波补偿效果,在负载突变的情况下具有很好的动态响应速度.     

基于加窗插值FFT和APFFT的谐波检测算法

研究加窗插值傅里叶变换(加窗插值FFT)和全相位傅里叶变换(APFFT)在电网谐波分析中的应用.详细分析了频谱泄漏效应对测最精度的影响.通过数值模拟,发现加窗插值FFT对信号的幅值和频率的检测精度很高,但对相位的检测还存在着比较大的误差,而APFFT具有相位不变性的特征,能精确地提取相位信号.将加窗捅值FFT用于幅值、频率的检测,将APFFT用于相位的检测,通过试验仿真运行表明,以上的分析结果,电网谐波的频率、幅度、相位精度都很高,达到了国家标准.     

LCL型APF在含非线性负荷系统中的应用

非线性负荷和电力电子器件的广泛并入，导致电网电压与电流正弦波畸变，电能质量降低。目前国内外比较主流的滤波装置，如PPF（无源电力滤波器）、APF（有源滤波器）、UPQC(统一电能质量调节器)等，由于自身的特点和缺陷，并不能对各种谐波起到很好的抑制效果。故本文提出了一种ILCLI型APF混合滤波器，协调控制以降低电网谐波含量，在降低非线性负荷谐波的同时，还能滤除开关频率附近的谐波。通过MATLAB/SMULNK建立混合滤波器仿真模型，经过FFT（快速傅里叶变换）分析，验证本模型不仅可以能够动态抑制谐波，而且能够很好地滤除开关谐波。     

基于Matlab和Labview的电力系统谐波检测

快速傅里叶变换（FFT）在电力系统谐波检测中被广泛应用。由于电网频率的波动,很难做到严格意义上的同步采样,导致频谱泄漏与栅栏效应现象发生,造成较大的测量误差。本文从传统的FFT检测方法出发,深入研究了加汉宁窗并进行插值运算的高精度算法。仿真时利用Labview所提供的Matlab节点将两款软件进行高效有机结合,以精确检测出各次谐波频率、幅值和相位,为进一步构建基于虚拟仪器的谐波检测系统打下基础。     

基于电网电压定向的光伏并网逆变器系统研究

针对传统的光伏并网系统逆变控制策略存在控制复杂、谐波含量多的问题,提出了一种基于电网电压定向的光伏并网逆变器直接电流控制方法,给出了以TMS320F2812为主控制器的三相光伏并网逆变器系统的硬件及软件设计。该逆变器直接电流控制方法采用过零检测电路测量电网电压的过零点时刻,得出过零点时刻的电网电压的旋转角度,从而得到逆变器输出电压的幅值和相位;采用SVPWM技术控制IPM的开断,使逆变器输出上述幅值和相位的电压,从而实现单位功率因数并网发电功能。实验结果表明,该逆变器直接电流控制方法简单,逆变器输出电流与电网电压基本保持相同的频率和相位,并网发电功率因数接近于1。     

基于Matlab和Labview的电力系统谐波检测

快速傅里叶变换（FFT）在电力系统谐波检测中被广泛应用。由于电网频率的波动,很难做到严格意义上的同步采样,因而导致发生频谱泄漏与栅栏效应现象,造成较大的测量误差。本文从传统的FFT检测方法出发,深入研究了加汉宁窗并进行了插值运算的高精度算法。算例仿真时利用Labview中提供的Matlab节点,将两款软件进行有机结合,充分发挥各自的优点。精确检测出各次谐波频率、幅值和相位,并为进一步构建基于虚拟仪器的谐波检测系统打下基础。     

矿用单相谐波治理系统设计

针对由于低压单相用电设备增多造成电力系统中局部电流波形发生严重畸变的问题,设计了一种在低压系统中使用的单相谐波治理系统。该系统采用瞬时电流检测控制方法检测电流谐波含量,使变流器产生一个与电流谐波幅值相等、相位相反的电流分量,完全抵消系统中的电流谐波。实验结果表明,该系统补偿效果良好,使得谐波畸变率从治理前的76.3%下降到10.4%。     

数字锁相测试用畸变电网信号模拟装置

设计了一种能够为数字锁相技术提供三相畸变电网电压和电流信号的模拟装置。选取TMS320F2812DSP作为控制核心,通过上位机与DSP通信,实时传递信号基波频率、基波和各次谐波的幅值和相位偏移参数,编写信号频率突变、幅值突变、相位偏移定点程序。DSP输出的PWM波形经过二阶有源低通滤波器滤波,获得所需要的模拟三相畸变电网电压和电流信号。ANF锁相实验结果表明装置产生的信号可直接输入到DSP、单片机中,为数字锁相算法提供畸变电网信号。     

光伏并网发电系统锁相环优化仿真研究

在光伏并网发电系统中,针对传统锁相环在电网电压不平衡的情况下存在的锁相精度不高的问题,提出了一种能快速、精确提取电网电压幅值和相位的双同步坐标系解耦锁相环(DDSRF-PLL)。通过采用双同步参考坐标系、标准的三相锁相环、去耦网络以及低通滤波器,有效地分离电压正、负序分量,滤除二次谐波,做到准确检测电网电压相位和幅值的目的,具有较好的动态响应特性。最后对电网电压单相跌落和两相跌落分别进行仿真,采用DSP样板进行验证。仿真结果验证了供电系统的精准性,提高了光伏并网发电系统并网的稳定性、有效性和可靠性。     

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。     

基于QTE的蒙古文显示机制研究与实现

蒙古语言是中国蒙古族使用的通用语言,由于蒙古文区别于其他文字的书写方式和其自身变形机制等特点,在很多通用的文字处理引擎中都不被支持。在嵌入式产品开发与应用领域中Linux加QTE已经成为流行方式。该文给出了一种在QTE环境上实现基于标准Unicode的蒙古文点阵显示和变形算法, 并自定义了支持蒙古文的QTE组件,扩展了QTE功能,为在Linux加QTE方式的嵌入式体系结构中处理蒙古文提供了一种解决方法。