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。     

基于自抗扰控制的单相光伏并网逆变控制器设计

传统的双环PI控制无法满足LCL并网逆变器电流谐波,输出电压扰动大;线性自抗扰技术可以通过线性扩张状态观测器和线性控制律对总扰动进行实时估计和补偿,大大提高并网逆变控制器的性能.为提高系统输出对电网电压扰动的抑制能力和系统的起动性能,引入电网电压前馈控制策略,提出基于自抗扰控制的电网电压前馈控制策略,采用MATLAB软件进行仿真.仿真结果表明,基于线性自抗扰控制下的单相光伏并网控制系统可实现对入网电流的无静差跟踪,提高了系统抑制电网电压扰动的能力,入网电流的总谐波失真小.     

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。     

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3～4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰～ -7.8‰, PDB) and matrix dolomites (-6.6‰～ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084～0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078～0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.     

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

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.     

海南岛地体及其毗邻陆缘晚中生代—新生代古地磁研究和构造演化

本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。     

《Chinese Science Bulletin》SUBJECT INDEX TO VOLUME 59(2014)

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Achieving Unusual States of Matter Under High Pressure

The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to     

Exciton Seebeck in Molecular Systems

Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with