分布式电源接入电网安全问题分析

随着分布式电源应用趋势越来越显著,不过在接入电网的时候却存在一定的安全问题.首先从接口方式和工作模式对分布式电源进行研究,方便分类研究不一样的影响结果,然后研究分布式电源接入电网的方法,创建配电网特殊模型,用来作为分布式电源接入安全性分析的标准;最后通过接入后模型的科学研究,计算分布式电源接入电网对稳态特性和电能保护、质量等方面带来的安全性问题,从而为配电网规划技术标准的改正提供科学依据.     

分布式电源对配电网继电保护影响的分析

研究了分布式电源接入放射状配电网对配电网继电保护的影响．利用MATLAB／simulink建立了配电网和分布式电源模型,并对配电网进行速断电流保护整定计算,针对分布式电源的容量和接入位置等因素,探讨了分布式电源对配电网短路电流分布和速断电流保护的影响．结果表明：分布式电源的容量越大对继电保护的影响就越大,保护可能失去选择性,分布式电源在保护上游产生助增作用使得保护范围增大,在保护下游产生分流作用使得保护范围减小,原有的保护有必要加装方向元件．     

含分布式电源配电网规划

分布式电源大量接入使配电网的规划、保护等面临新的挑战。首先介绍了分布式电源接入对配电网负荷预测、运行特性及投资收益等影响;其次对含分布式电源配电网规划进行分类,详细阐述了布点规划、扩容规划的内容及特点;接着对含分布式电源配电网规划建模方法进行描述;最后对含分布式电源配电网规划重要意义进行总结。     

分布式电源接入对配电网影响的层次综合评估方法

以风力发电机和风力发电配电系统作为主要的研究对象,以改进的IEEE-RBTS Bus6系统主馈线F4为例,对分布式电源接入对配电网影响的各项评估指标进行仿真,运用层次分析法,通过对各项评估指标模糊化处理和计算,得到不同方案的综合评估得分.评估结果表明,分布式电源接入对配电网的影响各项评估指标具有改善作用.     

含分布式电源的配电网自动化故障处理方案

分布式电源是一种具备数千瓦至五十兆瓦,能够与电力系统环境相融合的一种独立电源,更为简洁的说法是不直接与集中输电系统进行相连,电压等级在35 k V以下的电源,具有经济环保性等特点。当在配电网中接入分布式电源之后,对没有方向的电流保护有着很重要的影响,使得辐射型的网络结构产生了很大的改观。分布式电源是智能配电网技术应用的体现,是与传统配电网主要的明显区别。现如今配电网中分布式电源的连接成为可能,对DG接入方式,分析分布式电源的接入对配电网自动化故障的影响,提出保护方案是配电网自动化的研究内容之一。     

基于越限风险评估的分布式光伏电源接入配电网适应性研究

为合理评价现状配电网对规划分布式光伏电源的适应性,针对分布式光伏电源接入配电网引起的电压和潮流越限问题,讨论了典型接入配电网拓扑和接线模式,并在MATLAB/Simulink环境下建立了含分布式光伏电源模型的IEEE34标准节点配电网络系统.考虑到分布式光伏电源的随机出力扰动和负荷波动给配电网运行带来的风险,建立节点电压越限和支路潮流越限风险评估指标模型,分析了相同节点对不同容量电源的接纳能力,重点讨论了分布式光伏电源接入配电网准入容量.以配电网典型实际参数为例进行仿真实验,仿真结果验证了应用风险评估指标模型评估分布式电源接入配电网适应性的合理性.     

浅谈分布式电源接入对输配电网运行管理的影响

通过探讨分布式电源对配电网的影响,分析了大量分布式电源接入配电网对配电网运行管理造成的影响。指出在当前积极推进分布式电源接入电网大环境下,如何有效解决当前的配电网运行管理工作。     

基于孤岛运行状态概率方法的配电网可靠性评估

提出基于孤岛运行状态概率分布的计及分布式电源(DGs)配电网可靠性评估方法.通过研究分布式电源和主网系统构成的联合配电系统的运行方式,依据分布式电源的运行特点,以风机的理想运行平均风速所对应的出力为半径确定孤岛区域,形成合理的孤岛供电区域.基于孤岛4种运行状态,提出基于孤岛运行状态概率的具体算法,形成联合供配电网可靠性评估方法.以IEEE BUS6-F4馈线为例,实现接入DGs的配电系统可靠性计算.在DGs的渗透率比较低的情况下,检验了DGs对提高配电网可靠性的影响,计算结果更加合理可靠.所提方法模型简单,适应于多个分布式电源的配电网可靠性分析.     

一种基于人工神经网络算法的分布式电源快速配置方法

为减弱分布式电源接入后对配电网的电源质量、电压分布和稳定性造成的影响,提出了一种基于人工神经网络算法的分布式电源快速配置方法.首先,提出了反映配电网节点电压稳定性的量化指标,优先选择电压薄弱处作为分布式电源接入的位置.然后,建立基于人工神经网络的训练数据集,评价期望电压节点的分布式电源的合理容量.最后,在MATLAB中运行前馈人工神经网络算法,并通过52节点配电网测试验证该方法的可行性和有效性.结果表明,通过最优配置分布式电源位置和容量,电压稳定性得到了有效改善,网络损耗明显降低,节点的电压分布值提高至0.90 p.u.以上.     

配电网中分布式电源最优布置

基于放射状链式配电网连续解析模型和离散模型,研究了多台分布式电源装置接入系统对沿线电压和有功网损的影响.讨论了分布式电源装置安装在配电网中的优化方法以及分布式电源装置对配网电压分布的影响和其安装位置的限制.改进的最优布置算法克服了一般方法不能有效解决分布式电源装置的安装位置,以及因电压分布的要求对分布式电源安装位置产生的限制等缺点.算例表明,本文方法所求出的分布式电源最优接入位置,在满足系统电压分布情况下可有效改善有功网损.     

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.     

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.     

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.     

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.     

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.     

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.     

橡胶颗粒沥青混合料低温抗裂性试验研究

以AC-13级配为基础,将橡胶颗粒代替部分集料掺入混合料中,以低温弯曲试验为评价方法对不同橡胶颗粒掺量下沥青混合料的低温抗裂性进行研究,并引入应变能密度值对混合料的低温抗裂性进行综合评价.试验结果表明:橡胶颗粒沥青混合料试件的破坏微应变均超过2 300,满足冬寒区的技术指标;无论是否掺加橡胶颗粒,随着温度的下降,沥青混合料破坏时的最大弯拉强度增大,弯拉应变降低,劲度模量增大;弯曲应变能密度在胶粒掺量为1%左右时具有较大的弯曲应变能密度值,此时橡胶颗粒沥青混合料具有较好的低温抗裂性.     

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。     

Quantitative trait loci （QTLs） for quality traits related to protein and starch in wheat

Quality traits in wheat （Triticum aestirum L.） were studied by quantitative trait locus （QTL） analysis in a recombinant inbred line （RIL） population, a set of 131 lines derived from Chuan 35050 × Shannong 483 cross （ChSh）. Grains from RILs were assayed for 21 quality traits related to protein and starch. A total of 35 putative QTLs for 19 traits with a single QTL explaining 7.99-40.52% of phenotypic variations were detected on 10 chromosomes, 1D, 2A, 2D, 3B, 3D, 5A, 6A, 6B, 6D, and 7B. The additive effects of 30 QTLs were positive, contributed by Chuan 35050, the remaining 5 QTLs were negative with the additive effect contributed by Shannong 483. For protein traits, 15 QTLs were obtained and most of them were located on chromosomes 1 D, 3B and 6D, while 20 QTLs for starch traits were detected and most of them were located on chromosomes 3D, 6B and 7B. Only 7 QTLs for protein and starch traits were co-located in three regions on chromosomes 1D, 2A and 2D. These protein and starch trait QTLs showed a distinct distribution pattern in certain regions and chromosomes. Twenty-two QTLs were clustered in 6 regions of 5 chromosomes. Two QTL clusters for protein traits were located on chromosomes 1D and 3B, respectively, three clusters for starch traits on chromosomes 3D, 6B and 7B, and one cluster including protein and starch traits on chromosome 1D.     

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.