电力系统低频振荡的原因及抑制方法分析

随着电力系统低频振荡对系统稳定性危害的逐渐显现,对系统低频振荡的分析越来越受到关注,本文分析了系统低频振荡产生的原因,比较了常见的抑制低频振荡的措施,对比了优缺点,对柔性交流输电系统(FACTS)技术在抑制低频振荡中的应用进行展望。     

电力系统低频振荡在线监测研究

随着我国经济的发展,电能消耗量不断增加,交直流电力输送距离加大,电力系统稳定性问题变得更为复杂,导致电网低频振荡问题频发,成为制约电网传输能力和威胁电网安全的关键问题。文中以南通供电公司供电系统为依据,基于小波分析和Prony算法对电力系统低频振荡时的功率和电压信号进行分析,结合两者在电力系统低频振荡适用性,设计了低频振荡在线监测装置软硬件,为发电机运行可视化界面显示提供准确的显示信息,指导工作人员实时调控发电机的运行状态。实践证明在线监测装置实用性较强,可以有效解决分析电力系统低频振荡的难题,为电力系统在线监测低频振荡模式提供可靠的理论及实际工程依据。     

超导磁储能及其应用（上）

超导磁储能系统（SMES）是超导电力技术的一个重要组成部分,SMES不仅可用于调节电力系统的峰谷,而且可用于降低甚至消除电网的低频功率振荡从而改善电网的电压和频率特性,同时还可用于无功功率和功率因数的调节以改善电力系统的稳定性,预期在UPS储能电源系统中发挥作用。文中介绍了超导电性,SMES的工作原理和特点、就用（重点介绍SMES-UPS）和发展前景。     

超导磁储能及其应用（下）

超导磁储能系统（SMES）是超导电力技术的一个重要组成部分,SMES不仅可用于调节电力系统的峰谷,而且可用于降低甚至消除电网的低频功率振荡从而改善电网的电压和频率特性,同时还可用于无功功率和功率因数的调节以改善电力系统的稳定性,预期在UPS储能电源系统中发挥作用。文中介绍了超导电性、SMES的七作原理和特点、应用（重点介绍SMES-UPS）和发展前景。     

李雅普诺夫稳定在电力系统静态稳定中的应用

电力系统静态稳定是指电力系统受到小干扰后,不发生自发振荡或非周期性失步,自动恢复至初始的运行状态的能力。静态稳定主要涉及功角稳定与电压稳定。研究电力系统在小干扰后的暂态过程及其稳定性,可通过李雅普诺夫稳定性来描述。本文根据李雅普诺夫稳定的计算,提出了增强系统稳定性的方法。     

大型海上风电场一体化电力系统暂态稳定性研究

控制风电场一体化电力系统的暂态稳定性,可以提高海洋风电场的工作效率,降低运营成本,提高发电产能,因此迫切需要研究大型海上风电场一体化电力系统暂态稳定性。分析电力系统机械转矩特性以及稳态电路电流负荷特性,明确影响电力系统暂态不稳定的因素。建立暂态稳定性标准,使用等面积定则对电力系统暂态稳定性进行分析,并针对不稳定现象提出控制方案。实验结果表明,短路故障会造成功率波动,由功率波动引起频率振荡,使系统无法稳定运行,通过安装频率稳定设备能够很好地提高大型海上风电场一体化电力系统暂态稳定性。     

能量和功率在分析跨区域模态中的现象时的应用

这篇论文提出了一种基于能量的小信号方法,用以分析区域间的低频振荡。在对电力系统线性模型中能量关系分析的基础上,一个全面的分析系统振荡的方法框架被建立起来。这种方法可以使我们深入的了解区域间现象的性质,也可以和现代技术结合起来进行复杂电力系统的频谱分析。     

基于改进自适应协同控制方法的电力系统混沌控制

针对4阶混沌电力系统,该文提出一种具有快速收敛特性的自适应协同控制方案。首先基于Lyapunov稳定性定理和全局快速收敛理论,设计了一种具有快速收敛特性的协同控制器,该控制器可使宏变量快速到达不变流形并可以得到平滑无抖振的控制输入,实现宏变量的精确收敛。然后将所设计的控制器应用于4阶电力系统的混沌控制中。由于电力系统中的能量过剩会引起混沌振荡,在控制回路中引入储能装置,通过控制储能装置吸收电力系统中多余的有功功率来抑制其混沌振荡。在此基础上通过设计自适应律,消除了控制器设计过程中出现的复杂项,增加了控制器的实用性。最后通过数值仿真,验证了该控制方案的有效性与优越性。     

基于积分二次约束改进算法的时延电网控制策略研究

电力系统中信号传输的时间滞后通常会导致通信时延,影响电网的调控系统控制效率,从而造成电网运行稳定性降低。针对电力系统的通信时延问题,文中提出一种基于积分二次约束改进算法的时延电网控制策略。首先在考虑通信时延的基础上搭建电网微分方程模型,然后在算法中对电网的输入与输出设置约束条件,再结合耗散理论对积分二次约束算法进行改进。在此基础上设计时延反馈控制器,来提升电力系统稳定性,判定依据的保守性。最后,在电力系统安全分析软件中对算法进行仿真验证。仿真结果表明,所提出的基于积分二次约束改进算法的时延电网控制策略能够有效抑制振荡,同时减少通信时延对电网运行稳定性的影响。     

浅谈GIS在电力系统中的应用

随着用电规模及用电负荷的不断扩大和增长,电力系统运行控制日益复杂,地理信息系统技术应用于电力系统可以提高电力设备的安全性,提高电力系统运行的稳定性。首先,介绍了地理信息系统,然后阐述了地理信息系统技术在电力系统中诸多方面的应用,最后分析了地理信息系统在电力系统应用中面临的挑战。     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Nanoimprint Lithography -A Next Generation High Volume Lithography Technique

IntroductionNanoimprint Lithography is a well-acknowl-edged low cost, high resolution, large area pattern-ing process. It includes the most promising methods,high-pressure hot embossing lithography (HEL) [2],UV-cured imprinting (UV-NIL) [3] and micro contactprinting (m-CP, MCP) [4]. Curing of the imprintedstructures is either done by subsequent UV-lightexposure in the case of UV-NIL or by cooling downbelow the glass transition temperature of the ther-moplastic material in case of HEL…     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

Influence of PVK ： NPB hole transporting layer on the characteristics of organic light-emitting devices

A doping system consisting of NPB and PVK is employed as a composite hole transporting layer （CHTL）. By adjusting the component ratio of the doping system, a series of devices with different concentration proportion of PVK ： NPB are constracted. The result shows that doping concentration of NPB enhances the competence of hole transporting ability, and modifies the recombination region of charge as well as affects the surface morphology of doped film. Optimum device with a maximum brightness of 7852 cd/m^2 and a power efficiency of 1.75 lm/W has been obtained by choosing a concentration proportion of PVK ： NPB at 1：3.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.     

Analysis of error performance on Turbo coded FDPIM

Due to variable symbol length of digital pulse interval modulation（DPIM）, it is difficult to analyze the error performances of Turbo coded DPIM. To solve this problem, a fixed-length digital pulse interval modulation（FDPIM） method is provided. The FDPIM modulation structure is introduced. The packet error rates of uncoded FDPIM are analyzed and compared with that of DPIM. Bit error rates of Turbo coded FDPIM are simulated based on three kinds of analytical models under weak turbulence channel. The results show that packet error rate of uncoded FDPIM is inferior to that of uncoded DPIM. However, FDPIM is easy to be implemented and easy to be combined, with Turbo code for soft-decision because of its fixed length. Besides, the introduction of Turbo code in this modulation can decrease the average power about 10 dBm, which means that it can improve the error performance of the system effectively.     

A method for calculating the center position of collimated light

It is a key problem to accurately calculate beam spots＇ center of measuring the warp by using a collimated laser. A new method, named double geometrical center method （DGCM）, is put forward for the first time. In this method, a plane wave perpendicularly irradiates an aperture stop, and a charge couple device （CCD） is employed to receive the diffraction-beam spots, then the geometrical centers of the fast and the second diffraction-beam spots are calculated respectively, and their mean value is regarded as the center of datum beam. In face of such adverse instances as laser intension distributing defectively, part of the image being saturated, this method can still work well. What＇s more, this method can detect whether an unacceptable error exits in the courses of image receiving, processing and calculating. The experimental results indicate the precision of this method is high.     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.