分布式电站的3种入网方式比较研究

分布式电站的引入增加了电网的复杂性,对电网的稳定性和抗扰性等性能造成不确定性的影响。本文提出分布式电站的3种入网方式,并对3种入网方式下电网的拓扑特性、同步性能和抗扰性能进行比较研究。入网方式1:令新增加分布式电站直接与电网的负载节点相连(称为SC入网方式);入网方式2:在方式1的基础上,邻近分布式电站之间彼此连接(称为LC入网方式);入网方式3:同样在方式1的基础上,邻近分布式电站之间以概率p相连接(称为PC入网方式)。研究表明:3种入网方式中,LC入网方式电网的同步性能和抗扰性能最好,SC入网方式电网的同步性能和抗扰性能最差,PC入网方式电网的同步性能和抗扰性能位于其他2种方式之间。本文研究可为未来智能电网系统的构建提供理论参考。     

分布式电站入网方式对电网同步的影响

本文研究分布式电站通过接入原电网中负荷节点的方式接入电网。根据负荷节点到原电网中各发电机节点的平均距离情况,提出2种分布式电站入网方式:一种方式是新增分布式电站从离原发电机节点平均距离值最小的负荷开始接入,并按照平均距离值的升序顺序依次接入,简称方式A;另一种方式是新增分布式电站从离原发电机节点平均距离值最大的负荷开始接入,按照平均距离值的降序顺序依次接入,简称方式B。从电网统计特性和同步动力学角度进行比较,发现当分布式电站采用方式B接入电网时,网络节点分布较分散,网络同步能力较好,对离电站较近的负荷节点而言,其上的功率扰动引起的电网失同步波的扩散速度较慢,有利于失同步波的扩散抑制。此研究对分布式电站入网时提高电网可靠性运行提供了参考。     

分布式电站网络结构及并网研究

分布式电站相互连接,形成分布式电站网络,在分布式电站网络中,也有着不同的组成结构,这些结构就是一个小子网,本文称之为分布式电站子网。本文首先提取分布式电站网络中3种基本的组成结构进行研究,分别为线形结构、环形结构和星形结构;然后对比3种不同结构的分布式电站子网接入IEEE30及IEEE57系统下的网络平均距离及同步能力,发现在3种分布式电站子网中,星形分布式电站子网的中心节点接入电网时,网络平均距离最小且同步能力最好;最后将分布式电站连接为类星形的BA分布式电站网络,并接入电网中进行研究。研究发现:第一,随着分布式电站网络规模的扩大,将分布式电站网络接入电网使得网络平均距离增大,并且对电网的同步能力会产生不利的影响;第二,随着BA分布式电站网络与配电网之间的连边数不断增加,使得网络平均距离减小,并且网络临界耦合强度在不断减小,并最终趋向一个稳定值。     

电网发电机功率分配及电网负载不均衡发展研究

本文对电网发电站3种发电机功率分配方案(PE、DC、CC)进行研究。PE分配方式,发电机功率平均分配;DC分配方式,发电机功率按各发电机节点度中心性正比分配;CC分配方式,发电机功率按各发电机节点接近中心性正比分配。本文在IEEE14、IEEE39标准测试网络上进行仿真实验,从电网的同步和稳定性2个方面比较3种方案的优劣。研究结果表明:发电机功率按DC方式分配时,系统同步和稳定性能均最佳;按PE方式分配时,系统同步和稳定性能均最差;按CC方式分配时,系统同步和稳定性能居中。本文还研究了电网负载耗电量不均衡发展对电力系统性能的影响,研究表明:电网中耗电量增长的负载节点越多,耗电量增长越快,电网负载耗电量分布越不均衡,电力系统的同步和稳定性能均下降越快。因此,电网负载耗电量不均衡发展降低电力系统的同步和稳定性能。     

能量均衡的间断连接无线网络数据转发策略

针对间断连接无线网络中节点负载不均衡和能量资源受限的问题,提出了一种能量有效的数据转发策略.该策略根据网络运行的历史相遇信息,充分考虑网络特性,以分布式方式估计节点的活跃度、剩余能量和数据转发率,准确地估计节点效用值,感知网络节点的服务能力,以帕累托最优作为自适应选择最佳下一跳中继节点的理论依据,执行数据转发操作,有效地解决了由于节点自私性所导致的网络性能下降.数值结果表明,与其他能量管理机制相比,所提出的机制能够均衡网络节点负载,有效解决网络"热点"问题,延长网络生存时间,使投递率、时延等系统性能都得到大幅度提升.     

分布式多点采样短期电力负荷预测系统的设计

介绍了一种分布式多点采样短期电力负荷预测系统,包括电网电力线路和通讯信号线路;在通讯信号线路和电网电力线路的上游端设置有一个供电功率控制机构,在电网电力线路的下游端设置有若干个负载供电支线线路,每个负载供电支线线路和电网电力线路的连接处设置有一个分布式负载监测机构,若干个所述分布式负载监测机构均连接所述通讯信号线路的下游端;供电功率控制机构包括数据处理器和时间节点生成器,数据处理器和所述时间节点生成器均连接通讯信号线路的上游端,数据处理器连接时间节点生成器。确保不同位置处的采样数据在时间节点上的一致性,从而保障短期电力负荷预测分析结果的准确性。     

分布式发电系统与感性负载网络混沌同步控制

本文以永磁风力发电机(permanent magnet synchronous generator,PMSG)作为分布式发电系统节点,以永磁同步电动机(permanent magnet synchronous motor, PMSM)作为感性负载网络节点,研究了分布式发电系统与感性负载网络混沌振荡同步控制。首先基于改进函数投影同步方法设计混沌同步控制器,使PMSG和PMSM实现同步,且通过改变某些参数取值,可以调节同步时间;然后运用李雅普诺夫函数理论证明此方案的可行性;最后数值仿真验证了理论分析结果的正确性和有效性。研究结果对保证电力网络的稳定运行具有重要意义。     

直流配电网潮流算法与电压分布研究

为解决间歇分布式能源入网等问题,国内外建设直流电网的呼声高涨。与高压直流电网相比,建设直流配电网的电力电子技术相对成熟,技术经济性好,应时开展直流配电网理论研究具有重要意义。针对直流配电网潮流计算,构建了网状结构直流配电网等值网络和节点功率、节点电压、线路网损模型,提出了直流配电网潮流计算的约束条件、控制策略和稳态功率、电压分布算法。最后,利用IEEE 16节点算例对模型和算法进行了验证,证明了电压分布均衡性对网损的影响较大、网状电网接纳分布式电源的能力较强。     

永磁同步直线电机混沌杂草自抗扰控制研究

针对永磁同步直线电机没有中间传动环节, 任何不确定性扰动都会直接影响控制系统性能的问题, 设计 了一种改进杂草算法优化的 PMLSM(Permanent Magnet Linear Synchronous Motor)二阶自抗扰控制器。 通过采用 混沌反向学习初始化方法和柯西分布的空间分布方式改进杂草算法优化自抗扰控制器参数, 经过优化的自抗 扰控制器的控制其性能有明显提高。 仿真结果表明, 该自抗扰控制器响应速度快, 稳态误差减小 2% 且无超 调, 对负载扰动具有良好的鲁棒性。     

带有邻居度信息的容量负载模型下电网级联故障研究

考虑节点及其邻居节点的度值信息,本文提出了一种全新的节点容量负载模型,并将其应用到美国西部电网等电网级联故障研究中。通过高负载攻击(HL攻击)和低负载攻击(LL攻击)2种方式来攻击电网,仿真实验表明,与传统的基于节点度的容量负载模型相比,改进负载模型的电网具有更好的鲁棒性和抗毁性。通过对受攻击节点的邻居度值和与其本身度值之比的研究,分析了本文所提容量负载模型可以减小网络级联故障规模的原因。     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Design and analysis of generic LBS application developing platform

Location based services is promising due to its novel working style and contents.A software platform is proposed to provide application programs of typical location based services and support new applications developing efficiently. The analysis shows that this scheme is easy implemented, low cost and adapt to all kinds of mobile nework system.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that