PWM整流型变频调速系统降电容控制策略

为了改善系统的输入功率因数,并有效降低直流母线电容容量,本文对基于三相PWM整流的永磁同步电机变频调速系统展开了深入的研究,论证了PWM整流型变频调速系统降低直流母线电容的可行性,并提出一种基于功率前馈的降电容控制策略。该策略在传统的双闭环控制策略中增加了功率前馈环节以提高降电容后变频调速系统的稳定性。仿真结果表明所提降电容控制策略有效克服了直流母线电容较小情形下,整流侧和逆变侧功率强耦合引起的系统不稳定问题,改善了直流母线电压纹波特性。     

变频器在锅炉给粉系统的应用

文章介绍了传统锅炉给粉调速的缺点，锅炉给粉调速应用变频调速的意义及优势，例举了给粉变频调速系统的构成、设备选型，给粉变频调速系统的控制特点，给粉变频调速系统的上位机组态原则及PLC编程方法。     

电容分选机调速系统设计

变频器是当前应用最为广泛的交流调速装置。介绍了变频调速的基本原理,阐述了变频器如何选用以及使用中的注意事项,给出了分选机变频调速系统的设计方案,详细介绍了以变频器和三相交流感应电机为核心的调速系统的硬件设计及变频器的参数设置,总结了变频调速的优势。     

2012年IGBT继续抢占市场份额

随着现代电力电子技术及计算机控制技术的迅速发展,促进了电气传动的技术革命。交流调速取代直流调速,计算机数字控制取代模拟控制已成为发展趋势。交流电机变频调速是当今节约电能,改善生产工艺流程,提高产品质量,以及改善运行环境的一种主要手段。变频调速以其高效率,高功率因数,以及优异的调速和启制动性能等诸多优点而被国内外公认为最有发展前途的调速方式。以前的高压变频器,由可控硅整流,可控硅逆变等器件构成,缺点很多,谐波大,对电网和电机都有影响。近年来,发展起来的一些新型器件将改变这一现状,如IGBT、IGCT、SGCT等等。由它们构成的高压变频器,性能优异,可以实现PWM逆变,甚至是PWM整流。不仅具有谐波小,     

变频调速技术在风机节能运行中的应用

通过变频调速与挡板节流进行对比,阐述了风机变频调速节能原理及其优点。对某工程空调系统风机采用变频调速技术的节能效果和经济性进行了分析。     

变频调速在恒压供水系统中的应用

随着变频器调速技术及PLC控制技术的发展,变频调速恒压供水系统以其供水压力稳定、安全、可靠、节能而得到广泛应用.讨论了变频调速恒压供水系统的节能原理及系统优点,分析了一种变频调速恒压供水系统的控制过程.     

高压变频器在国电乌斯太热电厂引风机上的应用

本文介绍了风光牌高压变频器在乌斯太热电厂锅炉引风变频系统中的应用情况,阐述了变频调速系统的实现机理、功能及特点,对节能效果进行了分析。从全新的角度,诠释了高压变频调速系统与现场DCS系统的高效对接,增强了锅炉引风系统的自动化性能。     

高压变频调速系统对矿山提升机的改造

本文介绍了国产高压变频调速系统对矿山提升机改造的情况，对原矿山提升机系统及变频电控系统作简要说明，并对高压提升变频调速系统作了论述，运行效果表明改造是成功的。     

上海石化双速电机变频调速技术改造

介绍了应用变频调速技术对进口再割针梳机进行电气传动改造过程，简述了原双速电机调速系统所存在的问题，对原电气传动系统进行技术分析，提出应用变频调速技术设计变频调速系统来改造原双速电机调速系统，并通过实践说明进口设备通过变频技术改造，产生了明显的经济效益。     

变频调速系统设计中的问题分析

文中分析了变频调速系统的效率，阐述了变频器控制方式的合理选用，变频调速系统中变频器的选型及选择原则及系统设计中应注意的问题     

STAP在线阵和面阵中的比较

STAP（时空自适应处理）已被证明是机载雷达在强杂波环境下检测目标的一种有效方法。文中对面阵和线阵作比较,分析了阵元幅相误差对线阵中二维STAP（2D-STAP）性能的影响,对面阵天线采用的三维STAP（3D-STAP）技术,补偿因存在阵元幅相误差而导致各列子阵俯仰方向图的不一致性。对仿真数据处理结果证明三维处理具有更好的性能和很强的误差容错能力。     

龙门刨床直流控制系统振荡及消除

通过对龙门刨床直流控制系统分析,总结了系统振荡的原因,对每个方面存在的具体问题,提出了相应的检修方法和改进措施,以减小系统振荡。全文主要针对直流扩大机-直流发电机-直流电动机系统和晶闸管整流器-直流电动机系统的龙门刨床,对于全数字直制器系统的龙门刨床也提出了应注意的问题。     

双波长医用KTP/YAG固体激光器自控系统的性能分析

阐述了双波长KTP／YAG固体激光器自动控制系统的性能。该系统能自动将光能转换成热能。引入反馈环节后，自控系统不仅提高了不同波长激光输出的稳定度，同时在认定时间内还能分周期进行控制，并且能准确地自动控制输出的激光能量以及激光输出的相关参数。     

变频器在龙门铣床上的应用

介绍龙门铣床的直流调速控制系统的改造方案，根据龙门铣床工作台运动过程及原直流电机的容量来选择交流电机和变频器并对变频器的功能进行设定。     

Trade-off analysis on cost and manufacturing technology of an electronic product: Case study

A trade-off analysis on the cost and system packaging metrics of an electronic product aimed at the commercial/retail industry has been carried out. By comparing the system cost and packaging metrics with those of comparable consumer products, we have determined that there is opportunity for significant cost, size, and weight reduction of the overall electronics packaging system. These include the use of fine pitch IC packages, smaller discrete components, denser PCB wiring technology, double sided IC package surface mount, surface mount connectors, and improved plastics for the product housing. The analysis concluded that PCB area reduction of 40%, using a single PCB instead of three boards, reduction in board cost of over 50% and product weight reduction of over 28% are possible using available technologies.     

Accurate numerical modeling of the TARA reflector system

The radiation pattern of the large parabolic reflectors of the Transportable Atmospheric RAdar system (TARA), developed at Delft University of Technology, has been accurately simulated. The electric field integral equation (EFIE) formulation has been applied to a model of the reflectors including the feed housing and supporting struts, discretised using the method of moments. Because the problem is electrically large (the reflector has a diameter of 33/spl lambda/) and nonsymmetrical, this lead to a badly conditioned linear system of approximately half a million unknowns. In order to solve this system, an iterative solver (generalized minimum residual method) was used, in combination with the multilevel fast multipole method. Because of the bad conditioning, the system could only be solved by using a huge preconditioner. A new block-incomplete LU preconditioner (ILU) algorithm has been employed to allow for efficient out-of-computer core memory preconditioning.     

Investigation of multilayer, periodic, multistrip, and multislot waveguiding structures

For complex planer periodic structures, a system of spectral-domain integral equations is obtained. The unknowns in the equations are the coefficients of 2D Fourier transforms of the current density on strips and the tangential electric fields in slots. The number of dielectric layers, strips, and slots is not bounded. The system is solved by means of the Galerkin method with a basis taking into account the edge singularity. The singular (static) component of the kernel is separated and analytically transformed.     

Energy payback time of grid connected PV systems: Comparison between tracking and fixed systems

A review of existing studies about life cycle assessment (LCA) of PV systems has been carried out. The data from this review have been completed with our own figures in order to calculate the energy payback time (EPBT) of double and horizontal axis tracking and fixed systems. The results of this metric span from 2 to 5 years for the latitude and global irradiation ranges of the geographical area comprised between –10° to 10° of longitude, and 30° to 45° of latitude. With the caution due to the uncertainty of the sources of information, these results mean that a grid connected PV system (GCPVS) is able to produce back the energy required for its existence from 6 to 15 times during a life cycle of 30 years. When comparing tracking and fixed systems, the great importance of the PV generator makes advisable to dedicate more energy to some components of the system in order to increase the productivity and to obtain a higher performance of the component with the highest energy requirement. Both double axis and horizontal axis trackers follow this way, requiring more energy in metallic structure, foundations and wiring, but this higher contribution is widely compensated by the improved productivity of the system. Copyright © 2008 John Wiley & Sons, Ltd.     

某型无人机连续波电磁辐照效应研究

为了研究无人机在战场电磁环境下的安全性及可靠性,对无人机壳体的屏蔽效能进行了仿真计算,并在开阔场环境下建立连续波电磁辐照系统,利用连续波电磁辐照系统对无人机整机和通信链路核心部件收发组合进行辐照效应实验。仿真结果表明,在10MHz ~1GHz 连续波作用下,无人机壳体的屏蔽效能较低,为10dB 左右;实验结果表明,在某些频点或频段,无人机会出现通信链路中断的现象,表现为失锁状态,即无人机不能与地面控制站进行有效的数据传输,且不同的辐射场极化方向导致出现失锁现象的电场阈值不同。分析表明,电磁能量进入无人机机体内部产生干扰的主要耦合途径为无人机天线和无人机壳体的透射。     

变流量节能系统动态监测及实时调节系统设计分析

为提高变流量节能系统自适应性能和实时调节能力,提出基于双启发式动态规划的变流量节能系统动态监测及实时调节系统设计方法,构建变流量节能动态监测及实时调节控制对象模型,以供水流量及一次侧的供水温度、供水流量为初始约束参量设计系统的控制规则。在此基础上,结合双启发式动态规划模式并采用模糊优化分配控制策略,对系统进行调节和控制,通过线性规划学习方法,实现变流量节能动态监测及实时调节。仿真结果表明,采用该方法进行变流量节能系统动态监测及实时调节的自适应性能较好,各时段流量预测误差曲线波动介于-1.5至1.5之间,且热负荷值与预测热负荷之间相对误差最大值为2.5%,误差较低。