OPC现场总线安全代理研究

设计了一种OPC现场总线安全代理方式,采用基于USBkey密钥存储及数字签名载体的X.509身份认证体系及3向鉴别认证方式,会话数据加密采用AES算法及密码分组链接CBC工作方式,保证了身份认证及数据传输的安全.采用客户端数据包截获的方式保证了OPC代理对原有用户程序的透明.     

通信加密与数字认证在企业信息系统的应用

分析了电力企业一体化信息系统通信与身份认证的安全需求,并提出了解决方法,阐述了在已建成的＂数字证书体系＂和＂Novell目录系统＂基础上,集成基于安全信息层的安全传输协议和基于数字证书X.509标准的双因子数字认证技术,实现了信息系统通信加密与增强认证。实践证明,该方案提高了三级及以上级别信息系统的安全性,并为建设支撑坚强智能电网的信息网络安全接入奠定了基础。     

Interactive online undergraduate laboratories using J-DSP

An interactive Web-based simulation tool called Java-DSP (J-DSP) for use in digital signal processing (DSP)-related electrical engineering courses is described. J-DSP is an object-oriented simulation environment that enables students and distance learners to perform online signal processing simulations, visualize Web-based interactive demos, and perform computer laboratories from remote locations. J-DSP is accompanied by a series of hands-on laboratory exercises that complement classroom and textbook content. The laboratories cover several fundamental concepts, including z transforms, digital filter design, spectral analysis, multirate signal processing, and statistical signal processing. Online assessment instruments for the evaluation of the J-DSP software and the associated laboratory exercises have been developed. Pre/postassessment data have been collected and analyzed for each laboratory in an effort to assess the impact of the tool on student learning.     

8通道数字信号时序分析实验装置设计

为了丰富数字逻辑设计实验教学内容,拓展数字电路实验测试设备功能,基于FPGA设计8通道数字信号时序分析装置。该装置自带8路标准测试信号,通过2个按键实现8位触发字的设置,当8路输入信号符合触发条件时,使能片上RAM存储模块实现对8路数字信号的存储。存储器满时使能DA转换,通过生成两路模拟信号送入数字示波器X、Y通道,利用示波器的X-Y显示模式实现8路数字逻辑信号的显示;具备手动光标测试功能,能够通过LED显示光标所对应的8路逻辑信号。该装置解决了数字电路实验过程中依靠示波器无法同时观测多路逻辑信号的问题,同时能够作为一个工程实践案例引导学生基于FPGA进行数字系统设计。     

Teaching digital design to computing science students in a single academic term

How should digital design be taught to computing science students in a single one-semester course? This work advocates the use of state-of-the-art design tools and programmable devices and presents a series of laboratory exercises to help students learn digital logic. Each exercise introduces new concepts and produces the complete design of a stand-alone apparatus that is fun and interesting to use. These exercises lead to the most challenging capstone designs for a single-semester course of which the authors are aware. Fast progress is made possible by providing students with predesigned input/output modules. Student feedback demonstrates that the students approve of this methodology. An extensive set of slides, supporting teaching material, and laboratory exercises are freely available for downloading.     

Design and Implementation of a Class of Robust H ∞ Control for Stability Enhancement in Power Systems

The paper presents a method of designing a class of robust H X generator excitation controller in a power system. The proposed controller is utilized to damp inter-area oscillations and enhance power system stability. The robust controller design procedure for a linear composite system is presented in terms of positive definite solutions to modified algebraic inequalities. The resulting controller guarantees closed-loop stability and an H X -norm bound on disturbance attenuation. The effectiveness of the H X controller is demonstrated through digital simulation studies on a two-machine system. The digital simulation studies are conducted using a PSCAD/EMTDC software package. The simulation results show that the controller contributes significantly to the damping of inter-area oscillations and the enhancement of power system stability during disturbances.     

Educational use of EMTP MODELS for the study of a distance relayingalgorithm for protecting transmission lines

This paper presents the implementation of a distance relaying algorithm using EMTP MODELS, in which we have simplified the procedures of system modeling and distance relaying system by using a single structure of MODELS. The technique presented is based on integrating the modeling of the power system and the protective system in one program module. The purpose of this paper is to provide systematic relaying concepts by modeling a digital relaying system using MODELS functions within EMTP in a closed-loop manner, principally to facilitate and enhance an understanding of the basic concepts of distance relaying of final year undergraduate students/postgraduate students/young engineers who are new to the subject of power system protective relaying. Various elements of digital distance relaying are organized to generate a systematic approach to modeling the actual hardware of digital relaying systems. Case studies relating to the most commonly encountered single phase-to-ground fault and phase-to-phase fault are presented and various fault distances and fault inception angles are considered     

一种专用公开密钥基础框架的研究与应用

本文提出了一种专用公开密钥基础框架(PPKI),用于解决大中型企业自建网络(Intranet)与Internet之间的身份认证、通信加密和权限管理等问题。通过研究和开发PPKI的资源管理、证书管理和通讯加密等组成模块。在企业Intranet中部署PPKI,由Internet网络中的客户端IE浏览器向PPKI服务器申请X.509数字证书,并登录网络服务器访问不同权限的资源。从而验证了PPKI的可行性。     

数字化变电站系统可靠性评估与分析

为实现对结构较为复杂的数字化变电站系统进行全面、细致的可靠性评估,首先构建了基于并行冗余协议的数字化变电站整体结构模型。然后将一种新的可靠性评估方法———成功流法,引入数字化变电站的可靠性分析中,以数字化变电站结构模型为基础,建立用于可靠性评估的成功流模型,并根据该模型进行推导,得出变电站的全局可靠性参数。最后利用灵敏度分析方法,分析了不同元件的可靠性变化对整个系统成功概率的影响。     

Theory, simulation, experimentation: an integrated approach toteaching digital control systems

This paper discusses the approach adopted by the authors for teaching an undergraduate course (lecture and laboratory) in digital controls. Theoretical material is developed in the lecture concerning the application of direct digital control (DDC) to an analog bench-scale system consisting of a DC motor and tachometer. A simulation of the closed-loop control system with embedded digital controller is developed and run by the students using the TUTSIM dynamic simulation language. Finally, students perform a laboratory experiment in which they write a program to control the actual system using a personal computer and inexpensive interface card. The combination of hands-on experience and computer simulation with the more traditional, theoretical lecture material provides a well-rounded learning experience that better prepares the students to implement digital control systems in the real world     

数字化变电站继电保护方案定量评估系统研究

针对目前尚无定量评价与选择数字化变电站继电保护系统的设计方案的问题,提出开发数字化变电站继电保护方案的定量评估软件,阐述了该软件实现可靠性评估、经济性评估以及综合评估的技术路线,给出其实现的流程图,讨论了各功能模块的内容和实现方法。研究表明该软件的实现能有效保证数字化变电站继电保护系统设计方案的科学选择。     

数字电位器的特殊应用及防抖动方法

本文以典型的按键控制式数字电位器X9514为例，介绍了数字电位器的基本结构、工作原理及特殊应用，并提出了按钮控制式数字电位器的防抖动和重复动作问题的两种解决方法。     

A Digital Computer Engineering Laboratory

The course and laboratory discussed in this paper offer students an opportunity to gain realistic experience in the engineering of digital computers. The laboratory provides a sufficient number of logic elements to allow students to construct general purpose digital computers of modest design; only a few assemblies of fixed design are provided. The course progresses from work with basic combinational and sequential circuits through the design and testing of digital subsystems, to a project in which groups of students are challenged to specify, design, test, program, and demonstrate their digital computer. Two years of experience indicate that students are willing to enthusiastically expend a great deal of effort to meet this challenge.     

A systematic approach to the implementation of final year projectin an electrical engineering undergraduate course

This paper describes a computerized management system for the processing of a final year project in an electrical engineering undergraduate course including a structured project allocation to students, a comprehensive assessment procedure, an automated processing of marks, and a management supporting system. An optical reader is used to scan the project selection made by all the students, and the allocation algorithm allocates as many projects as possible in meeting the students' preferences. A new attempt using a grading category index for each assessment criterion is implemented and the assessment of the student's performance is evaluated through five main components with 31 assessment criteria. The marks for each student are scanned by an optical reader and calculated by a weighted linear conversion of all the grading category indexes. The assessment system is more valid as it has many specific criteria and is more reliable as the process is consistent. The management supporting tools and experiences in handling very large groups of students especially in the maintenance of a uniform marking standard to all the students are highlighted. It is hoped that some of our approaches can be selectively adopted for undergraduate course work on continuous assessment even for a smaller student population     

Virtual work bench for electronic instrumentation teaching

This article describes the design and implementation of a virtual laboratory, computer-generated for the theoretical and practical teaching of electronic instrumentation. The virtual laboratory is implemented in a windows framework for which the teacher or student requires no prior knowledge to manage the program. The Virtual Instrumentation Workbench for Instrumentation allows visualization of the time and frequency effects produced in analog to digital conversion and in digital signal processing as well as visualizing the effects of 16 different teaching topics. It incorporates ten different waveforms, eight windows algorithms, five digital filters, and five discrete/fast Fourier transforms (DFT/FFT). The use of the virtual laboratory has allowed more than 500 students to understand the functioning of the new devices that are flooding the instrumentation market. Although it has been developed as an aid for electronic instrumentation teaching, it can also be used for the teaching of digital signal treatment     

Least-square-error estimate of individual contribution in groupproject

In a group project, some students may work hard but the others may not participate at all. If we give the same mark to all the students in a group, it would be unfair to the hardworking ones. Therefore, it is important to assess the contribution made by each student. In this paper, we propose an assessment method to estimate the contribution made of every student in a group project. This assessment method can supplement the customary assessment methods adopted by the lecturer. Using this method, every student is required to estimate and state the percentage contribution made by everyone in the group, and the lecturer determines the least-square-error estimates of their respective contribution. We enhance this assessment method to tackle the following two problems: (1) the honest students will try to give the correct estimates but they may give biased estimates on their own contribution and (2) the dishonest students may intentionally give incorrect estimates     

基于PIC单片机的A/D变换器的设计与实现

本文介绍了用PIC16C5X单片机实现A/D转换的技术和方法,详细讨论了测量原理、参数选择、分辨率分析和误差分析,并给出了应用实例和软件流程、程序清单.     

实时励磁仿真系统接口装置中控制角测量模板的设计

介绍了高精度函数发生器MAX038和数字电位器X9241M基本使用方法，详细描述了如何使用它们提高控制角测量精度以及通过软件设定系统量程，并结合作的体会指出了设计中应注意的问题。     

变电站远程视频监控系统的实现

介绍了一种变电站远程视频监控系统的实现方案。详细探讨了视频监控系统的配置,传输系统的选择和视频远程传输的两大关键技术,通过对两种组网方式的理论分析和搭建其实验视频监控系统,分析了各自的优缺点并确定了视频监控系统的组网方式。介绍了系统软件的功能,采用C Build工具,运用动态链接库DLL和ActiveX控件对系统软件进行了设计。结合实际工程对远程视频监控系统存在的一些问题进行了分析,为变电站视频监控系统的实现提供了一种可靠的方案。     

Enhancing state-space control teaching with a computer-basedassignment

This paper describes an assignment study that is undertaken at Heriot-Watt University by students who have elected to study the digital/state-space control module as part of their Masters program in Digital Systems Engineering. The assignment is based around the inverted pendulum system and uses the computer package MATLAB/SIMLINK. The assignment allows exploration of topics that are difficult through conventional tutorial examples and is structured in a manner that enhances the traditional classroom teaching approach. The topics covered are pole-placement design and both deterministic and stochastic state estimation. The given design performance specifications result in nonunique state-feedback and observer gain matrices. This has the dual advantages of reflecting a common practical control situation and also helps eliminate the potential for plagiarism among the students