Bifurcation analysis for an SMIB power system with series capacitor compensation associated with sub-synchronous resonance

In this paper,an introduction to the bifurcation theory and its applicability to the study of sub-synchronous resonance (SSR) phenomenon in power system are presented. The continuation and bifurcation analysis software AUTO97 is adopted to investigate SSR for a single-machine-infinite-bus power system with series capacitor compensation. The investigation results show that SSR is the result of unstable limit cycle after bifurcation. When the system exhibits SSR, some complex periodical orbit bifurcations, such as torus bifurcation and periodical fold bifurcation, may happen with the variation of limit cycle. Furthermore, the initial operation condition may greatly influence the ultimate state of the system. The time-domain simulation is carried out to verify the effectiveness of the results obtained from the bifurcation analysis.     

Adaptive RTRL based neurocontroller for damping subsynchronous oscillations using TCSC

Modern interconnected electrical power systems are complex and require perfect planning, design and operation. Hence the recent trends towards restructuring and deregulation of electric power supply has put great emphasis on the system operation and control. Flexible AC transmission system (FACTS) devices such as thyristor controlled series capacitor (TCSC) are capable of controlling power flow, improving transient stability and mitigating subsynchronous resonance (SSR). In this paper an adaptive neurocontroller is designed for controlling the firing angle of TCSC to damp subsynchronous oscillations. This control scheme is suitable for non-linear system control, where the exact linearised mathematical model of the system is not required. The proposed controller design is based on real time recurrent learning (RTRL) algorithm in which the neural network (NN) is trained in real time. This control scheme requires two sets of neural networks. The first set is a recurrent neural network (RNN) which is a fully connected dynamic neural network with all the system outputs fed back to the input through a delay. This neural network acts as a neuroidentifier to provide a dynamic model of the system to evaluate and update the weights connected to the neurons. The second set of neural network is the neurocontroller which is used to generate the required control signals to the thyristors in TCSC. This is a single layer neural network. Performance of the system with proposed neurocontroller is compared with two linearised controllers, a conventional controller and with a discrete linear quadratic Gaussian (DLQG) compensator which is an optimal controller. The linear controllers are designed based on a linearised model of the IEEE first benchmark system for SSR studies in which a modular high bandwidth (six-samples per cycle) linear time-invariant discrete model of TCSC is interfaced with the rest of the system. In the proposed controller, since the response time is highly dependent on the number of states of the system, it is often desirable to approximate the system by its reduced model. By using standard Hankels norm approximation technique, the system order is reduced from 27 to 11th order by retaining the dominant dynamic characteristics of the system. To validate the proposed controller, computer simulation using MATLAB is performed and the simulation studies show that this controller can provide simultaneous damping of swing mode as well as torsional mode oscillations, which is difficult with a conventional controller. Moreover the fast response of the system can be used for real-time applications. The performance of the controller is tested for different operating conditions.     

一种新型的三相异步电动机保护电路设计介绍

文章介绍了三相异步电动机电源的相序接反,断相,三相电压不平衡的故障监测保护电路的电路结构及工作原理。     

网络流量监测服务器系统的研究

在电信企业的大型网络体系中,对网络数据流量的监测和控制已经为人们所关注。结合Flow Accounting Server(FAS)和Cabletron Traffic Accounting(CTA)管理系统,通过对LFAP协议的分析和研究,提出了对网络的流量和策略进行控制的方法,从而解决了大量的网络流 量监测任务。     

SSR荧光标记技术分析东四省典型绿豆品种的遗传多样性

东北是我国绿豆主产区之一,品种资源相对丰富。分析不同绿豆品种间遗传背景差异,明确其群体遗传结构,有助于提高品种资源在育种中的利用效率。本研究利用8对SSR引物对东四省40份绿豆品种进行荧光标记毛细管检测分析,共检测出43个等位变异,平均为5.4个,多态信息含量(PIC)变幅介于0.40~0.75之间,平均为0.55。比较分析发现,平均等位变异数目的分布为:黑龙江省(3.63)=辽宁省(3.63)>内蒙古自治区(3.50)>吉林省(2.88);多态信息含量(PIC)的分布为:黑龙江省(0.530)>辽宁省(0.527)>内蒙古自治区(0.469)>吉林省(0.382),即黑龙江省遗传变异水平最高,吉林省最低。聚类分析表明,黑龙江和辽宁的绿豆种质为组群Ⅰ,内蒙古和吉林为组群Ⅱ。本研究初步明确了东北各省(区)绿豆品种的遗传多样性水平,为资源的再收集及育种利用提供了参考,并为绿豆资源的深入利用奠定了基础。      

TCSC次同步频率阻抗特性及其抑制SSR的参数设计

正确分析TCSC次同步频率阻抗特性是研究TCSC抑制次同步谐振（SSR）能力以及进行TCSC参数设计的重要基础。基于对TCSC次同步频率阻抗模型的研究,绘制了三维频率阻抗图,分析了TCSC次同步频率阻抗特性,特别提出了次同步谐振导通角的概念。基于内蒙古上都电厂串补输电线路模型,在满足工频基波阻抗调节特性的前提下,根据次同步频率阻抗特性研究了考虑TCSC自然抑制SSR时其主电路参数的设计原则。通过对上述系统各模态频率阻抗特性的综合分析,讨论了TCSC控制参数的选择方法。仿真结果证实了次同步频率阻抗特性分析结果的正确性。     

基于SSR标记的花生品种遗传多样性分析

从212对SSR标记引物中筛选出48对引物,对63份花生品种进行遗传多样性分析,共得到251个等位变异,变异范围为2~13个,平均每个标记位点有5.23个变异;48个SSR标记的多态性信息含量为0.252~0.873,平均为0.647;63份材料的遗传多样性指数为0.508~2.243,平均值为1.272;品种间的遗传相似系数在0.657~0.960之间,不同类型的花生品种间的遗传相似性较小,不同来源花生品种间的亲缘关系也较远;聚类分析结果表明,63个花生品种在遗传相似系数为0.74处分为4大类,聚类分析结果与传统的花生分类结果吻合。     

SSR标记辅助回交转育大豆7S球蛋白α-亚基致敏蛋白缺失新品系

为快速培育7S球蛋白致敏蛋白α-亚基缺失的优质大豆新品系,以（α＇＋α）-亚基双缺失型材料日B为供体亲本,东农47为受体亲本,以杂交一回交转育方法为基础,结合SSR标记辅助遗传背景选择与主要农艺性状鉴定及品质分析,在BC2F4选育到7S球蛋白α-亚基缺失新品系Cb80。Cb80综合农艺性状优良,遗传背景回复率大于90％,其蛋白质及氨基酸总量为44．1％、41．95％,分别比轮回亲本东农47提高3．5和3．76个百分点。     

苦荞遗传多样性分析与核心种质筛选--测试文章

利用SSR分子标记技术,对来自西藏、陕西、四川、贵州等4省区的210份苦荞品种进行遗传多样性研究。结果表明,所选用的50对SSR引物中,有16对引物多态性良好,共扩增出178个条带,其中多态性条带达118个,占总数的66.3%;210份苦荞种质的遗传变幅为0.62～0.98,平均值为0.80,在遗传相似系数为0.88处可划分为5大类。聚类结果显示,来自同一地区的苦荞品种显示出聚为一类的趋势,表明苦荞的遗传信息受地理分布的影响较大;第V类所聚的41份分别来自西藏（27份）、陕西（8份）和贵州（6份）的品种表现出较为丰富的遗传多样性,与其他种质相比,这41份材料不仅遗传差异较大,而且遗传来源广泛,可作为苦荞核心种质筛选的基础。     

大型汽轮机发电机的次同步振荡仿真

在阐明电力系统次同步振荡基本原理的基础上,建立了考虑主磁路饱和的同步发电机模型。通过saber进行时域仿真,对单机一无穷大系统在三相短路时的工况计算分析,并由此得到一些具有价值的结论。