基于FPGA的电力系统时钟同步技术设计

根据电力系统地理分布地域广以及对时钟同步要求精度高的原则,提出了一种GPS授时模块和IEEE1588协议相结合的时钟同步方案,该方案按地理因素将整个电力网络划分为若干个子网络,各个网络之间利用GPS接收模块实现时钟的同步,子网络内部采用IEEEl588协议实现时钟的同步,从而实现整电力网络的时钟同步;然后在FPGA平台上对精确时钟模块、GPS信息接收及处理模块、IEEE1588协议的部分实现模块进行实现;最后通过系统误差验证表明本文所提出的方案切实可行。     

数字化变电站中合并单元的研究现状

介绍了数字变电站合并单元使用中的关键技术。首先对比分析了GPS,SNTP,IEEE1588时间同步方法的特点,对目前实际采用的电子式互感器与合并单元之间的数字接口方案进行归纳总结,然后分别进行了基于IEC 61850-9-1和IEC 61850-9-2的合并单元的功能模块分析,最后综述了合并单元的性能测试方案。     

数字化变电站合并单元同步问题的研究

根据同步的协议不同,分别比较多MU同步方式PPS、NTP和IEEE1588等的精度和工程实现难易程度．最后提出各种同步方式各有利弊．在实际工程中,需要综合考虑对同步性能的要求、工程开支,以及变电站系统构架等选择合适的同步方式．     

VLAN中IEEE1588协议精度的提高

IEEE1588精密时间协议(PrecisionTimeProtocol,PTP)是专门为测量和控制领域制定的一个时间同步协议。研究了在支持VLAN的二层交换机中如何充分利用VLANTag字段来提高PTP数据包在二层交换机当中的转发优先级,从而减小了PTP数据包在网络传输中引起的抖动和误差,实现了纳秒级的精度。     

基于IEEE1588协议的精确时钟同步算法改进

本文详细分析了IEEE1588时钟同步的基本原理,并在此基础上给出一种改进的时间同步方法。该改进的时钟同步算法针对网络传输路径的不对称性引入加权因子,用一定时间窗内的主从时钟偏差样本的算术平均值而不是直接利用主从时钟偏差来调整从时钟,并根据算法的状态改变时间窗N的大小,同时利用方差阈值滤波的方法过滤跳变过大时钟偏差测量值,保证同步算法的稳定性。最后给出Alcatel-Lucent TSS5R系统在实验室的时间性能实验结果。实验结果表明TSS5R时钟同步具有稳定的性能,同步精度达到亚微秒级,可满足PTN产品高精度时钟同步的要求。     

信息台

2007年版《中国科技期刊引证报告》(核心版)公布本刊两项重要计量指标指标在85种同类学科期刊中排名在1723种核心期刊中排名影响因子2.026 2 12总被引频次1366 3 177·信息台·▲NI推出业界首款PXI Express系统定时控制器2007年11月———美国国家仪器有限公司(National Instruments,简称NI)宣布推出全新NI定时工具,包括:业内首款PXI Express定时与同步控制器,以及能够在GPS、IRIG(Inter-Range InstrumentationGroup)和IEEE 1588上同步PXI系统的PXI模块。有了这些全新工具,工程师们可获得PXI系统中更优质的同步和时间码功能…     

面向虚拟仿真环境的BH RTI性能测试研究

BH RTI是北京航空航天大学自主研发的分布交互仿真运行平台,该平台支持HLA 1.3和IEEE1516标准,是支持分布式交互仿真应用程序开发和应用程序高效运行的软件系统平台。在基于RTI的分布式仿真应用程序开发中,时间同步、网络延迟、吞吐量是RTI性能测试的主要指标,对BH RTI上述三个性能指标的测试方法进行了研究,设计了测试方案,通过编写相应的测试应用程序对BH RTI的时间同步、网络延迟、吞吐量等性能进行了测试。     

火电厂控制系统采用物理分散技术方案的分析

文章介绍了火电厂控制系统采用物理分散技术方案的概念,讨论了几个具体解决办法：远程I／O技术方案、现场总线技术方案、分散布置的电子设备间技术方案,并提出了现阶段火电厂控制系统实现物理分散技术方案的实施建议：（1）设置适度合理的分散电子设备间;（2）大胆积极地应用成熟可靠的远程I／O技术与产品;（3）在同一个工程中采用统一标准的现场总线技术与产品．     

飞行器控制系统数据综合关键技术研究

控制系统数据综合是导弹等飞行器实现低成本和小型化的有效途径.文中提出基于双处理器结构的飞行控制系统任务计算机系统结构,并对数据综合过程中的时间同步、时间管理等关键技术问题,采取初始同步和周期同步相结合的方式,对任务运行同步误差进行了修正,在时间同步的基础上,将控制链条按照资源占用情况进行分解,并对各功能模块进行统筹、分时调度,实现了双机并行处理.     

PTN技术发展趋势和组网应用

对分组传送网(PTN) MPIS-TP,技术的发展情况进行了介绍,包括MPIS-TP的标准化惰况,PIN设备发展和测试情况,对1588v2和同步以太网的支持,对LTE承载方式的探讨,以及应用方式的考虑等.     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

Western and Eastern culture differences in commercial field

The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity.     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

风的曲线

Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose.