变速恒频双馈风力发电系统空载并网积分变结构控制

围绕变速恒频双馈风力发电系统空载并网问题,将滑模变结构控制与矢量控制相结合,提出了一种基于指数趋近率的积分变结构控制策略,并分别对理想情况、电机参数摄动情况和电网电压波动情况下的双馈风力发电系统空载并网过程进行仿真分析．结果表明：在本控制策略下,双馈风力发电系统空载并网动态响应良好,稳态误差近似为零,过渡平稳,并网后无需更改控制器参数即可顺利进入最大风能追踪阶段;与传统PI控制相比,本控制策略能够有效抑制参数摄动及外部扰动对双馈风力发电系统的影响,具有较强的全局鲁棒性．     

开关磁阻电机新型控制策略的研究

研究了以滑模变结构控制策略为基础的新型开关磁阻电机控制系统,该控制系统结合应用滑模与PI两种控制方式,削弱了滑模变结构控制存在的抖振现象,改善了整体性能。仿真分析结果表明,综合控制系统兼有滑模控制良好的动态性能和PI调节器稳定性好的优点。     

浅析变速恒频无刷双馈电机风力发电控制策略

本文在介绍无刷双馈电机控制系统存在问题的基础上,对无刷双馈电机电动运行的控制策略,并简要介绍几种标量控制、直接转矩控制和转子磁场定向控制,对于变速恒频无刷双馈电机风力发电控制设计具有重要意义。     

面向最大风能捕获的双馈电机新型非线性积分滑模控制

为解决风力双馈电机在低风速及风速波动较大情况下转速暂态性能差、风能捕获效率低等问题,提出了一种面向双馈电机最大风能捕获的新型非线性积分滑模(NNISM)控制策略。设计了一种具有自饱和特性的新型非线性积分滑模控制器,其控制方法具有参数可调节、利用非线性势能函数规避积分超饱和效应等特点,以使整体系统具有更小的抖振;结合风力机风能利用系数和最大叶尖速比运算出风力双馈电机处于最佳叶尖速比下的最佳转速并输入至系统中,以使系统达到最大风能利用状态;构建了一套面向双馈电机最大风能捕获的新型非线性积分滑模控制系统,在组合风速变动情况下对NNISM控制器进行参数设定,以使系统于低速状态或风速波动较大情况下具有较好的动态性能。仿真结果表明,该新型非线性积分滑模最大风能捕获控制策略的控制性能不会在低速状态或风速波动较大情况时下降,具有转速超调量小、跟随速度快、鲁棒性能强等优点,可以完成最大风能捕获的控制目标,具有广泛的应用前景。     

无刷双馈电机风力发电控制系统与仿真研究

从无刷双馈电机(BDFM)转子速d—q模型出发,推导出BDFM的有功和无功功率数学模型,并设计了初步的变速恒频无刷双馈电机风力发电系统功率控制策略．计算机仿真结果表明,BDFM通过定子功率绕组发电,定子控制绕组通过变频器从电网吸收或向电网反馈电能．系统响应快,稳定性好．该研究表明变速恒频无刷双馈电机风力发电的设想在技术上是可行的．     

滑模变结构控制Buck变换器的控制

随着可再生资源的日益普及工业快速发展,Buck变换器的应用越来越普遍。相比于PI控制的Buck变换器,可以通过使用滑模变结构来控制,这样可以达到稳态精度更高,动态响应更快速以及更强的鲁棒性等优点。本文深入研究Buck变换器滑模变结构控制系统,分析参数选择依据,设计控制电路并给出仿真结果验证所提方法的可行性。     

基于SMC的大型光电跟踪平台直流调速系统算法

为克服大型光电跟踪平台直流调速系统的非线性因素影响,利用变结构控制响应速度快,针对系统的参数变化和外部扰动不灵敏的特点,设计了滑模变结构控制器。通过Simulink 仿真并与PID(Proportional_Integral_Differential)控制方法相比较得出,采用SMC(Sliding Mode Control)设计系统稳态跟踪的误差减小到PID控制系统的1/3,调节时间缩短为原来的1/7,由超调3％变为无超调,由对参数摄动和外部扰动敏感变为不敏感。从而证明了在大型光电跟踪平台直流调速系统中,滑模变结构控制能显著减小系统反应时间和稳态跟踪误差,对参数摄动和外部扰动具有良好的鲁棒性。     

BoostPFC变换器的离散滑模控制

针对单相AC／DC Boost变换器,提出基于离散滑模变结构电流内环控制与数字PI调节器电压外环控制相结合的综合控制系统。其中离散滑模控制器采用在滑模面设计中对系统施加期望动态响应的方法来得到控制器的主要参数。另外,数字控制可以使开关切换采用固定的开关频率,消除了传统滑模控制因切换频率不固定带来缺陷：仿真实验结果表明,这种控制系统设计兼有滑模控制动态性能、鲁棒性好与PI调节器稳定性好的优点。     

变速恒频双馈风力发电系统的励磁电源

给出了变速恒频双馈风力发电系统中交流励磁电源的控制方案.在基于电网电压定向的基础上,分别对转子侧变换器和网侧变换器进行了研究.分析了双馈电机数学模型,并对空载并网控制策略进行了设计,实现了系统在变风速条件下无冲击电流并网.采用直接电流控制对网侧变换器进行控制,并实现了能量双向流动,功率因数可调,使双馈风力发电系统能运行在次同步和超同步两种状态下.实验结果证实了理论分析的正确性和控制策略的有效性.     

三相电压型PWM整流器滑模变结构直接功率控制

摘 要：本文提出了一种基于滑模变结构控制理论的三相PWM整流器直接功率控制方案,它利用滑模变结构控制系统的鲁棒性和动态性能较好、参数整定简单的优点,解决了传统上基于PI算法的直接功率控制系统抗扰性能差、对PI控制参数较敏感、网侧电流总谐波含量（THD）较大的缺点;在MATLAB/SIMULINK环境中建立仿真模型,对滑模控制和PI控制两种方案进行仿真比较,结果表明滑模控制方案明显优于PI控制方案.     

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.     

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。     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

《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