Power swing damping control by HVDC power modulation in an ac/dc hybrid transmission system

This paper describes power swing damping control by HVDC power modulation. In a hybrid system (where the ac transmission system and the HVDC system compose a loop transmission system), damping control of power swing by control of HVDC power is called power modulation control. The new HVDC link between the Shokoku and Kansai power systems forms a loop transmission system consisting of the existing ac transmission system and the new HVDC transmission system; therefore, power modulation control can be applied for stabilization of the ac system. This paper deals with a newly developed power modulation control system to damp two power-swing modes occurring in a 60-Hz interconnected system and the neighboring power system to the HVDC converter station. Characteristics of power swings in an ac systems, principles of power swing damping control by power modulation, the control system design method, and the results of verification tests by digital and analog simulators are described. It is shown that the developed power modulation system applied to the HVDC link is effective for damping two power swing modes.     

A Proposal of Identifying Optimized Layout of Devices in Electromagnetic Resonant Coupling Type Wireless Power Transfer System

Recently, a system for wireless power transfer (WPT) using electromagnetic resonant coupling has been evaluated and developed for practical applications such as a wireless charge system for automobiles or electronic devices. However, the efficiency of an electromagnetic resonant coupling type WPT system with LC resonators is greatly affected by the layout of the LC resonators allocated in the system. This means that there is an optimum layout for the LC resonators for transferring wireless power at higher efficiency. This paper presents a new method for identifying the optimum layout for the LC resonators in a WPT system. One of the key ideas is that the problem of finding the optimum layout is replaced by the problem of calculating the equivalent current sources in the LC resonators. The amplitude of the equivalent current sources can be calculated to solve ill‐posed system equations by using inverse analysis. First, the proposed method is described. The system equations to be solved are formulated by means of equivalent circuit techniques. Second, the proposed method is applied to a simplified model to identify the optimum layout for the LC resonators in a WPT system. Then, the results found using the proposed method are verified by comparing the ratio of receiving power with the identified layout and without the LC resonator. Finally, in order to verify the validity of the proposed method, the calculated results are compared with the experiment results using the same model.     

电流型逆变器六相感应电动机驱动系统的分析

本文以十二脉冲电流型逆变器驱动的六相感应电动机拖动系统为研究对象,利用坐标变换,在考虑电流型逆变器换流过程的情况下,推导出该系统的d-q模型,用已建立的d-q方程分析了系统的稳态特性,同时采用小位移原理进一步分析了系统参数以及电机参数对系统稳定性的影响,且编制了计算机程序,为该类系统的优化设计提供了有力的手段。     

Measurement of the damping coefficient of an electric power system by use of a superconducting magnet energy storage system

In this paper, a new application of superconducting magnetic energy storage (SMES) for diagnosis of power systems is proposed. Basic experiments for measurement of damping coefficient of power systems by use of SMES are carried out in an experimental system with a small generator, artificial transmission lines, and a small SMES. The SMES produces small power disturbances in the power system without affecting its operating conditions. The small power oscillations in the power system due to continuous power disturbances generated by SMES are observed. The relations among the damping coefficient, the power disturbances, and the power change of SMES are discussed for a one-machine infinite-bus system. The damping coefficients of the power system are obtained by investigating the oscillations due to the sinusoidal power changes of the SMES. The possibility of estimation of the steady-state power system stability by monitoring the damping coefficients of an operating power system by the use of SMES can be shown experimentally. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 119(3): 40–48, 1997     

An expert system for substation fault diagnosis and alarmprocessing

An expert system for substation fault diagnosis and alarm processing developed by the Electric Power Systems Laboratory of the National Technical University of Athens is presented. It is written in Turbo Prolog and is implemented on a personal computer. The system includes many characteristics of an expert system cell because it can be expanded easily by adding new information to its knowledge base or by changing the existing information. The basic idea behind this system is to provide a nonexpert with the necessary information and interaction in order to make a fault diagnosis through the substation alarms in a very friendly environment. The main task of the system is to replace the troubleshooting manuals of substation equipment and human expertise in substation fault diagnosis and alarm processing with a user-friendly computer environment and to take advantage of the user's accumulated experience to expand and modify the knowledge base of the expert system. The expert system can be connected directly to a PC-SCADA system through a simple software interface written in C for online data acquisition     

高压直流输电与发电机励磁的综合变结构控制

研究了交直流互联系统采用变结构控制策略提高系统的暂态稳定性问题。以一单机无穷大系统为研究对象,并以交直流互联系统的动力学方程、发电机的电磁功率方程和高压直流输电直流功率调制规律方程为基础,建立了发电机励磁与高压直流输电综合控制的非线性数学模型。采用滑膜变结构控制策略设计了发电机励磁和高压直流输电的综合控制器,该控制器采用先设定系统的滑模运动方程,再求取等效系统,最后求取切换面的方法来得到控制规律。在交流输电线路发生故障时,采用常规的控制策略和文章提出的控制策略对系统进行了仿真,仿真结果表明,采用该控制策略能够显著提高输电系统的暂态稳定极限及暂态稳定性。     

Damping improvement by FACTS devices: A comparison between STATCOM and SSSC

Following a disturbance, the machines in a stable power system initially oscillate, and then settle at the stable equilibrium point where the transient energy is zero. This paper uses the rate of dissipation of transient energy as a measure of system damping. The above concept is then applied to determine the additional damping provided by a static synchronous compensator (STATCOM) and a static synchronous series compensator (SSSC). Analytical expressions for additional damping provided by these devices are carefully derived and compared for classical model of a simple power system. The proposed technique of evaluating system damping is then tested on a single-machine system and for some special faults in the 10-machine New England system. The results obtained in both the systems are then systematically described.     

一个计算机控制系统的多道程序应用环境

计算机控制系统要完成Ｉ／Ｏ控制,过程控制和数据通信等多项任务,因此是一个多道程序系统,文章介绍一个基于ＲＳＸ－１１Ｍ操作系统,在ＰＤＰ－１１／７３计算机上执行过程控制任务的实际的多道程序系统的设计方法,该方法即应用了操作系统的固有特性,又结合控制系统应用软件的特点,能够很好地解决多采样周期计算机控制系统应用软件的调度问题,而且还能节省大量内存。     

Harmonic propagation on an electric distribution system: fieldmeasurements compared with computer simulation

Increasing use of power electronic loads on distribution feeders together with greater use of power factor correction capacitors on the distribution system can result in poor operating conditions in the form of high harmonic levels propagating through a distribution system. HARMFLO (Harmonic Power Flow Study Program) was developed by EPRI (Electric Power Research Institute) for use in the analysis of harmonics on a power system. However, for a typical analysis of a distribution system, data for some of the parameters required by HARMFLO are not available. Furthermore, exact load information is usually not available. Harmonic levels determined from field tests on a distribution system are compared to results of HARMFLO simulations to determine if this analysis tool can provide useful results despite the lack of exact information for load modeling and other system parameters     

具有面向服务架构的电力企业资产管理系统模型设计

针对企业资产管理(enterprise asset management,EAM)系统在电力行业中的应用,提出了电力企业EAM系统设计模型,讨论了该模型各层的设计思想和设计要点,并运用面向服务的设计方法对系统进行服务粒度的划分,同时使用Web 服务技术实现与外部系统的接口,最后结合电力行业设备点巡检管理系统的开发实例阐述了EAM应用系统的设计方法。