A frequency and duration approach for generation reliabilityevaluation using the method of stages

A frequency and duration approach for generation reliability evaluation using the method of stages is presented. Two separate expressions are provided, one for the loss of load expectation (LOLE) and the other for the loss of load frequency (LOLF). Explicit relationships for determining the parameters of these expressions from the generation system data are derived. Several studies to illustrate the accuracy and efficiency of the proposed approach are also reported     

An approach to amplifier frequency compensation

In this paper, an approach to the input lag compensation technique is described. The compensating network is explored iteratively, using two programs that take advantage of the graphical user interface (GUI) tools provided by MATLAB and provide a clear insight into the behavior of the network. The first program explores the response of an amplifier with a single pole; the second one corresponds to an amplifier with two poles. The approach is aimed at the undergraduate level. It has been found that it provides a faster and better understanding of the theoretical principles involved than other teaching aids.     

An adaptive neural network approach for the estimation of power system frequency

A new approach to the estimation of power system frequency using an adaptive neural network is presented in this paper. This approach uses a linear adaptive neuron or an adaptive linear combiner called “Adaline” to identify the parameters of a discrete signal model of the power system voltage. Here, the learning parameters are adjusted to force the error between the actual and the computed signal samples to satisfy a stable difference error equation, rather than to minimize an error function. The proposed algorithm shows a high degree of robustness and estimation accuracy over a wide range of frequency changes. The technique is shown to be capable of tracking power system conditions and is immune to the effects of harmonics and random noise.     

一种隐式同步策略及其在电磁暂态并行计算中的应用

以减少并行计算中的同步过程的时间开销为目标,建立了同步并行算法的一般耗时模型,提出了一种适用于并行电磁暂态仿真计算的隐式同步策略。该策略由两部分组成,一是计算流程的优化调整方案,用于提高系统的计算并行度;二是计算量的合理分配方案,以消除协调侧和分区侧的冗余的同步操作。进一步,提出了基于MATE的改进电磁暂态并行算法,能够实现隐式同步的并行计算。仿真算例表明,所提出的改进策略有助于优化系统切分方案,可显著提高并行电磁暂态仿真计算效率,实现较大规模系统的实时仿真。     

An approach to model high‐frequency distortion in negative‐feedback amplifiers

In this paper, we present an analytical approach to study the harmonic distortion in the frequency domain of operational amplifiers (opamps) embedded in a nonlinear feedback network. The analysis is based on a frequency‐domain block scheme that models the opamp with one block and the feedback network with two blocks, but it is demonstrated that only one feedback block needs to be characterized for the two basic inverting and non‐inverting configurations. The obtained closed‐form expressions extend our understanding of nonlinear frequency behaviour in feedback opamp circuits. Indeed, they give the contribution of each network component to the output distortion. As an instructive example, we analysed second‐ and third‐order harmonic distortion of an active‐RC inverting lossy integrator having all the components nonlinear. The accuracy of the proposed method is confirmed by comparison with computer simulations at transistor level. Copyright © 2006 John Wiley & Sons, Ltd.     

AD9850及其在频率测量中的应用

较详细地阐述了AD9850的功能特性、控制方式和基本工作原理,并介绍了其分频特性的电路组成,最后讨论了在AT89C51的控制下实现频率测量的应用以及频率测量系统的硬件和软件设计。     

An application of the Burr function to the description of dielectric relaxation data in frequency domain

The subject of this paper is to show how to adopt the Burr function, which has its analytical representation in time domain only, to fitting experimental absorption and dispersion data.     

An approach for the calculation of magnetic field within square spiral inductors at low frequency

The magnetic field distribution within a square spiral inductor is investigated in this paper by summing closed‐form expressions for the fields from each segment. Plots illustrating the variation of the normally directed B ‐field penetrating the surface of the spiral traces are then developed for a variety of perspectives. The expressions and insight gained represent an essential step in developing a detailed model of effects such as current crowding, which significantly limit the spiral's performance in practical circuits. Copyright © 2002 John Wiley & Sons, Ltd.     

利德华福冲破2500KW/6KV高压变频器外商垄断

北京利德华福电气技术有限公司生产的高压变 频器遍布祖国大江南北,从杭州到新疆,从黑龙江 到海南岛,到处都利德华福高压变频器,经过六年 的艰苦努力,终获丰硕成果,产品获得用户认可。技 术的发展日新月异,一日千里,利德华福没有躺在 过去的成绩上沾沾自喜,仍是每一日都竭尽全力,努 力研究产品,不断改进、完善,源源不断地为用户 提供更多、更好、更加符合用户需求的产品。     

变频器技术及应用

变频器的基本概念： 变频器是一种能够简单、自由地改变交流电机转速的一种控制装置。简单地说变频器是通过改变电机输入电压的频率来改变电机转速的。     

An improved finite frequency approach to robust filter design for LTI systems with polytopic uncertainties

In this paper, the finite frequency robust filtering problem (‐FFRFP), design of a robust filter minimizing the norm from the disturbance input to the estimation error evaluated over a prescribed finite frequency domain, is considered for continuous‐time and discrete‐time linear time‐invariant (LTI) systems with polytopic parameter uncertainties. By means of the generalized Kalman–Yakubovich–Popov (KYP) lemma in combination with a result known as Finsler's lemma, the ‐FFRFP is cast as a linear matrix inequality (LMI) optimization. Examples are given to demonstrate that the proposed condition can achieve improvement over the previous ones in the literature. Copyright © 2012 John Wiley & Sons, Ltd.     

PWM电机变频调速引擎SA866及其应用

具体介绍了三相脉宽调制(ＰＷＭ)引擎ＳＡ８６６的各项功能参数及其脉宽调制原理,给出一种在变频调速应用中的实用方案。     

CDMA移频直放站的规划和应用

本文通过对CDMA移频直放站的分析介绍,讨论了直放站对基站接受灵敏度的影响,并利用上下链路分析提出了移频直放站规划设计的思路和方法.     

工频变化量距测试及应用

对工频变化量距离保护的校验方法进行了研究,《电力系统继电保护规定汇编》中的校验方法将工频变化量距离元件视为一个过电压继电器,而《电力系统继电保护实用技术问答》中的计算公式则是基于传统距离继电器的概念,比较了2种方法的优点及不足。国产继电保护试验仪一般都有针对工频变化量的专用测试菜单,而进口仪器则需预先计算和设置。结合上海电网具有短路容量大、电气距离短的特点,提出了使用进口仪器测试工频变化量距离保护的具体方法。最后,对工频变化量距离保护的开放条件的必要性作了分析。     

An automated system for frequency response analysis with application to an undergraduate laboratory of electrical machines

This paper describes a LabVIEW-based automated system to carry out frequency response tests in electrical machines. The system is being used by undergraduate students in the laboratory of electrical machines, where they can experiment with the application of frequency response analysis and the characterization of mathematical models. An advantage of the system is its friendly user interface to a laboratory experiment. The system avoids the risky utilization of oscilloscopes for data acquisition and shortens the time taken to analyze the measured data. The Automated System for Frequency Analysis (ASFFA) can carry out tests within a bandwidth of 0.001-900 Hz. In addition, the ASFFA can estimate the transfer function parameters based on one- or two-port network theory. Design details of the interface, system structure, frequency response tests, electrical machine modeling, and signal processing are presented. Finally, ASFFA is applied to synchronous, induction, and direct-current machines.     

A new PID load frequency controller design method in frequency domain through direct synthesis approach

In this paper a new PID controller design method based on the direct synthesis (DS) approach of controller design in frequency domain is presented. The parameters of the PID controller are obtained through frequency response matching with the DS controller. The method yields linear algebraic equations, solution of which gives the controller parameters. The design method has been developed for single-area as well as multi-area power systems. Non-linearity like the generation rate constraint (GRC) has been considered. Several examples are taken from the literature to demonstrate the effectiveness of the proposed method in comparison with some prevalent design methods.     

An alternative approach for calculating/measuring fundamental powers based on wavelet packet transform and its frequency sensitivity analysis

Power and harmonic analysis are among the most important topics of power systems. These analyses usually are based on Fourier transform method. In this study, as a novel approximation, the accuracy of proposed method using wavelet packet transform for fundamental active-reactive-apparent powers, displacement power factor are pointed out with computer simulations. Moreover, frequency sensitivity of the wavelet packet based power analysis, any study concerned with it is not found in the literature up to now, is carried out in comparison with the classic Fourier-based analysis. The results show the supremacy of the proposed wavelet packet-based approach over the Fourier-based approach when the frequency variation is concerned.     

光伏发电有功功率预测及其在电网频率控制中的应用

针对光伏发电有功功率预测准确率低的问题,提出了基于马尔科夫修正的小波神经网络光伏发电有功功率预测算法。将历史数据分为晴朗、多云等天气类型,分别进行训练,建立网络模型,再根据预测日天气预报采用不同的网络模型预测。光伏的大规模并网将会对电力系统的有功平衡造成很大的扰动,调度部门借助光伏发电有功功率的准确预测进而对自动发电控制进行超前控制可以有效降低频率的波动,减轻自动发电控制机组的调节压力。实际算例对算法进行了验证,并仿真了有功扰动下的频率恢复特性,表明了基于光伏发电有功功率预测的自动发电控制超前控制方法的有效性。     

逆相序排列降低线路工频电场的计算及应用

以220kV永吉和井永同塔双回架空线路实现逆相序排列为例,探讨逆相序排列降低线下工频电场强度的计算原理和理论计算结果,提出具体的实施方案,分析比对线下工频电场强度的实测结果,验证逆相序排列对降低同塔双回架空线路线下工频电场的效果显著,为解决工频电场强度过大探索既经济又实惠的办法。