贵阳南部电网“7·7”事故的仿真反演和分析

针对2006年7月7日贵阳南部电网事故,根据实际系统,用NETOMAC程序建立了原动机、调速器和汽轮发电机过速保护的详细模型,采用实际系统能提供的参数,缺省参数则通过参照典型数据和现场试验获得。在此基础上,对故障进行了仿真反演和研究,仿真结果较为成功地模拟出了整个故障过程。并就此进行了进一步的研究性仿真,发现并论证了孤网故障高频的主要原因是对机组一次调频速率不合理的限速设置,提出了抑制高频稳定系统的措施。文中研究说明了目前电网存在频率稳定的安全隐患,大电网孤网高频稳定问题亟待深入研究。     

Water absorption in a glass-mica-epoxy composite [II: field distribution and diagnostic in a stator bar geometry]

In this paper, the water concentration profile within the insulation of a stator bar in the presence of a water leak is calculated by resolving the Fick?s equation. The temperature strongly activates diffusion processes, but the shapes of concentration profiles remain similar. From the measured dielectric properties versus water content, an electrical model is developed in order to calculate the field and potential distribution within the insulation. The field is reduced in wet zones due to the high local permittivity and conductivity compared to dry zones. This effect is favorable since the breakdown field is lowered in wet zones. On the other hand, the field in dry zones is reinforced, but the value attained remains lower than the short-term breakdown strength. This explains why stator bars in the presence of waters leaks may survive for long times, in spite of high local water concentrations in excess of 1%. The high sensitivity of dielectric properties at low frequency to the presence of water suggests non-destructive methods to detect wet bars in a real power generator.     

The Case for Project-Oriented Courses with "Educationally Useful" Student Design Projects

In looking for "real life" undergraduate student design projects engineering educators may overlook projects which have a "real life" educational purpose within the University. Such "educationally useful" projects can provide the stimulus for very motivating student design experiences. In this paper the concept of "educationally useful" student design projects is formulated and three examples are included to illustrate this concept. The goal of this paper is to illustrate through these examples how the academic environment can provide the stimulus for excellent "real life" student design projects. The advantages of these projects to the student and to the educational process are described.     

Task learning of a task robot in real space by using a learning system in virtual space

Reinforced learning by which a robot acquires control rules by trial and error has attracted considerable attention. However, it is quite difficult for robots to acquire control rules by reinforcement learning in the real space because many learning trials are needed to arrive at the control rules; the robot itself may lose control, or there may be safety problems with the control objects. In this paper we propose a method in which a robot in the real space learns a virtual task, after which the task is transferred from the virtual to the real space. The robot eventually acquires the task in a real environment. We show that a real robot can acquire a task in a virtual space with an input device, using the example of an inverted pendulum. Next, we verify that the acquired task in the virtual space can be applied to a real‐world task. We emphasize the utilization of the virtual space to effectively obtain the real‐world task. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 172(1): 38–47, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20968     

Robust and simple adaptive control system design

Recently, the simple adaptive control (SAC) method has attracted considerable interest because of the simple structure of its adaptive controller. The method can only be applied to plants with so-called almost strictly positive real (ASPR) characteristics. Unfortunately, most real plants do not satisfy this condition. Furthermore, real plants contain disturbances such as uncertain elements. This paper deals with such problems and proves that the implementation of a parallel feedforward compensator makes it possible to apply the SAC method to non-ASPR SISO plants with plant uncertainties. Furthermore, a robust SAC algorithm in the presence of a class of external disturbances is also considered. The effectiveness of the parallel feedforward compensator and robust adaptive controller designed in this way is examined through several numerical simulations.     

Genetic Programming for the Automatic Design of Controllers for a Surface Ship

In this paper, the implementation of genetic programming (GP) to design a controller structure is assessed. GP is used to evolve control strategies that, given the current and desired state of the propulsion and heading dynamics of a supply ship as inputs, generate the commanded forces required to maneuver the ship. The controllers created using GP are evaluated through computer simulations and real maneuverability tests in a laboratory water basin facility. The robustness of each controller is analyzed through the simulation of environmental disturbances. In addition, GP runs in the presence of disturbances are carried out so that the different controllers obtained can be compared. The particular vessel used in this paper is a scale model of a supply ship called CyberShip II. The results obtained illustrate the benefits of using GP for the automatic design of propulsion and navigation controllers for surface ships.     

南方电网交直流混合系统线损的实用计算方法

降低线损是提高电网运行经济性的重要措施。以南方电网西电东送系统为研究背景,根据IEC 61803标准,并结合实际工作经验,对西电东送交直流混合系统的线损计算进行研究,剖析了送电量、电网结构、送电构成以及设备维护水平等几大影响西电东送系统线损的关键性因素,对提高我国西电东送系统的运行经济性具有较好启发作用。     

Alarm processing in electrical power systems through a neuro-fuzzy approach

This work presents a methodology that combines the use of artificial neural networks and fuzzy logic for alarm processing and identification of faulted components in electrical power systems. Fuzzy relations are established and form a database employed to train artificial neural networks. The artificial neural networks inputs are alarm patterns, while each output neuron is responsible for estimating the degree of membership of a specific system component into the class of faulted components. The proposed method allows good interpretation of the results, even in the presence of difficult corrupted alarm patterns. Tests are performed with a test system and with part of a real Brazilian system.     

试论“光文化”建设与国际化大都市精神文明发展的关系

城市经济建设的发展是大城市发展的基础,但是光有钱、有现代化的城市经济建设成果,而没有具有特色的城市光文化建设的持续发展成果,并不能使城市精神文明上升到新水平,从而不能使该城市在全球化发展环境中以其独具的文明特色鲜活地凸现、成为真正的国际化大都市。从根本意义上来说,高楼大厦、四通八达繁荣的道路、商业、通讯设施等基础建设只要有经济实力就可达到,而有深度、有特色的社会上层建设领域的文明建设却不是只扔钱就可企望的!包含功能与景观照明所体现的城市光文化是国际化大都市精神文明社会上层建筑发展的重要体现。如何更深入理解城市光文化、如何实现并通过城市光文化建设与时俱进的发展不断提高城市的国际化大都市精神文明发展水平,是值得我们深入、持续探讨与身体力行的重要问题。     

The measurement of power system frequency using a microprocessor

This paper proposes a simple algorithm for the real time measurement of power system frequency. Using simple microprocessor hardware results of acceptable accuracy can be obtained in the presence of substantial DC and harmonic components.     

Extension of a driving-point and a transfer function to a positive real two-port matrix

A solution is presented to the problem, which arises in two-port modelling, of determining a second driving-point function from a given driving-point function and a transfer function. the given functions must have a common denominator and satisfy the necessary positive real (PR) matrix conditions: the driving-point function must be PR and on the imaginary axis the real part of the transfer function must be zero whenever the real part of the driving-point function is zero. By using a partial fraction expansion and determining a required first-order polynomial, a unique second (minimum) driving-point function is obtained. Examples to illustrate the method are worked out.     

电力系统基波交流采样频率修正的“三点”算法

为减少电力系统中频率变化导致数据采集和测量的误差,一般采样同时要不断修正采样频率。在常用的硬、软件频率测量或跟踪方法中,从软件方面提出了电力系统基波交流采样频率修正的“三点”算法。在对该算法进行了数学推导、静态仿真、优缺点分析并介绍了奇异点和随机数据的舍弃后给出了工程中应用实例。分析表明,该算法可提高电力系统基波电压和电流的测量精度,配合滤波器使用,能够满足实时性高的要求。     

Comparison of magnetic flux density meter responses over a databaseof residential measurements

Fourteen possible types of magnetic flux density meters based on the Faraday induction principle have been mathematically simulated. The different readings obtained from each type when the magnetic flux density is more complex than the ideal case of a single frequency (60 Hz) with linear polarization are shown. Using a real database of residential flux densities from 17 homes, it is shown that the presence of harmonics and elliptical polarization can result in significant deviations in readings between meter types. The highest variations from the total RMS (root mean square) flux density are found with broadband meters that have derivative responses or corrected peak detectors     

Dielectric properties and spatial distribution of polarization inpolyethylene aged under ac voltage in a humid atmosphere

This paper reports the results of an investigation of the dielectric properties, growth of water tree density and spatial distribution of polarization in samples of non-stabilized LDPE. Samples were initially sand-blasted to accelerate initiation of water trees, and subsequently aged in salt solution for approximately three weeks under two regimes of temperature (room temperature and 65°C). Aging both with and without the presence of electric field stress was studied. The capacitance and dielectric loss of each sample were measured using a HV capacitance bridge, and compared to theoretical models over the frequency range 10^-5 to 10⁴ Hz. The results indicate a real movement of charges/ions in the polymer bulk which causes a deterioration of the electrical insulation properties even in the absence of AC fields. The presence of a field further degrades the insulator. Samples were studied using the LIMM (laser-intensity-modulation method) to determine the distribution of polarization, assuming mean polarization is zero and space charge is absent. In the absence of the external field there is a presence of ionic charges of opposite polarity, which increases with increasing aging time and is highest at room temperature. The length of the twenty longest vented water trees was measured after various aging times, and it was found that trees grown at room temperature are longer than those grown at 65°C. Also, the tree density was higher in specimens tested at room temperature     

Robustness of cellular neural networks in image deblurring and texture segmentation

Template parameters of cellular neural networks (CNNs) should be robust enough to random variability of VLSI tolerances and noise. Using the CNN for image processing, one of the main problems is the robustness of a given task in a real VLSI chip. It will be shown that very different tasks such as 2D or 3D deconvolution and texture segmentation can be solved in a real VLSI CNN environment without significant loss of efficiency and accuracy under low precision (about 6–8 bits) and random variability of the VLSI parameters. The CNN turns out to be very robust against template noise, image noise, imperfect estimation of templates and parameter accuracy. The parameters of a template are tuned using genetic learning. These optimized parameters depend on the precision of the architecture. It was found that about 6–8 bits of precision is enough for a complicated multilayer deconvolution, while only 4 bits of precision is enough for difficult texture segmentation in the presence of noise and parameter variances. The tolerance sensitivity of template parameters is considered for VLSI implementation. Theory and examples are demonstrated by many results using real-life microscopic images and natural textures.     

Optimal energy exchange of an industrial cogeneration in a day-ahead electricity market

This paper addresses an optimal strategy for the daily energy exchange of a 22-MW combined-cycle cogeneration plant of an industrial factory operating in a liberalized electricity market. The optimization problem is formulated as a Mixed-Integer Linear Programming Problem (MILP) that maximizes the profit from energy exchange of the cogeneration, and is subject to the technical constraints and the industrial demand profile. The integer variables are associated with export or import of electricity whereas the real variables relate to the power output of gas and steam turbines, and to the electricity purchased from or sold to the market. The proposal is applied to a real cogeneration plant in Spain where the detailed cost function of the process is obtained. The problem is solved using a large-scale commercial package and the results are discussed and compared with different predefined scheduling strategies.     

Parallel feedforward and simplified adaptive control

Simple adaptive control systems were recently shown to be globally stable and to maintain robustness in the presence of disturbances if the controlled plant is ‘almost strictly positive real’, namely, if there exists a positive definite static output feedback (unknown and not needed for implementation) such that the resulting closed-loop transfer function is strictly positive real. This paper is an attempt to show in an intuitive way how to use parallel feedforward and the stabilizability properties of systems in order to satisfy the ‘almost positivity’ condition. The feedforward configuration may be stationary, if some prior knowledge is given, or adaptive, in general. This way, simple adaptive controllers can be implemented in a large number of complex control systems, without requiring the order of the plant or the pole excess as prior knowledge     

"圆心拟合法"测量短路故障情况下的动态频率

探讨短路情况下动态频率测量的一种新方法,提出的采用"圆心拟合法"对经过低通滤波的故障信号进行拟合处理,可以快速有效地从短路电流中分离出周期分量和非周期分量,进而精确计算出动态频率.该算法在对称或不对称短路故障情况下均适用,且启动时仅需三个连续的采样数据,具有时延小、精度高、稳定性好的优点.     

Discrete‐time simplified adaptive control of a dc motor based on asymptotic output tracker theory

Simplified adaptive control (SAC) has simple structure and is readily implemented in real systems, but few real applications have as yet been reported. A discrete‐time algorithm for SAC has recently been proposed by one of the authors. Although it solves the problem of unavoidable time delay arising in the discretization of the continuous‐time algorithm, the algorithm generally produces a bounded output error between the controlled plant and the reference model due to a feedforward gain added in parallel to the controlled plant so as to satisfy the positive real (ASPR) property with almost complete rigor. This paper treats the applicability of the SAC algorithm to a real system, that is, the position control of a dc motor with variable load. The algorithm used here is modified, and the feedforward compensator is inserted in parallel not only to the controlled plant, but also to the reference model. The algorithm guarantees that the output error vanishes asymptotically. The control performance is examined by both simulation and testing of an actual system and is compared with that of a conventional PID control. These results illustrate satisfactory control performance and verify the applicability of the modified algorithm. © 2001 Scripta Technica, Electr Eng Jpn, 135(1): 33–42, 2001     

Chaos in a series circuit with a nonlinear capacitor and a nonlinear inductor

This paper proposes a nonlinear circuit that generates chaotic oscillations. The proposed nonlinear circuit includes a nonlinear capacitor and a nonlinear inductor by using Generalized Impedance Converters. Both computational experiments and experiments on real circuits show that the region for chaotic oscillation is very wide, demonstrating that the proposed circuit is effective as a chaos generator. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 150(2): 35–42, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10361