同步发电机整流系统的建模

为分析同步发电机整流系统的运行稳定性,给出了系统简化模型。为考虑换相重叠,超瞬变电感从电机中分离出来,带整流负载的三相同步发电机数学模型只计及转子回路磁链的直流分量。忽略了交流侧和直流侧的谐波,整流器的数学模型利用开关函数。对三相同步发电机整流带反电动势负载系统的数学模型进行线性化,从而导出了发电机在直流侧的等效阻抗、系统等效阻抗和系统特征方程,利用它们可分析系统的稳定性。     

同步发电机整流系统的稳定性分析

同步发电机整流带反电动势负载时,当系统参数不匹配,在一定工况下,可能出现低频振荡。为了消除低频振荡,基于系统的特征方程、利用R ou th判据推导出小扰动稳定判据,对特征根和系统的等效阻抗进行了计算和分析。系统出现低频振荡是由于系统负的等效阻抗导致自激和Hop f分叉。当系统的总阻抗为零,且有一对共轭的特征虚根时,低频振荡出现。仿真证实了理论分析。给出在转子的交轴上增设一短路绕组和增大交轴阻尼绕组的时间常数等几种解决低频振荡的措施。     

发电机数学模型的选择对扭振计算的影响

给出了ｄ，ｑ，０坐标系统下１ｄ－１ｑ和１ｄ－２ｑ发电机阻尼绕且数学模型参数计算方法，运用有限元法全面系统地计算了模型中的参数，建立了完整的机电联合仿真模型，开发了相应的扭振计算程序，并在研制的试验台上对其进行了实验验证，运用仿真程序就发电机数学模型的模型的选择对轴系扭振响应计算的影响进行了研究，提出了适于扭振计算的发电机数学模型。     

带整流负载三相同步发电机的状态方程和数值仿真

根据同步发电机的基本方程，建立了带整流负载三相同步发电机的数学模型，并计及电枢绕组电阻和整流器正向压降及电阻、电感负载的情况．导出了各种整流状况下的状态方程，提出了合适的算法，可对整流过程直观地分析．数值仿真与实验结果吻合良好．     

交直流混合供电同步发电机稳态性能的仿真

为了考虑磁路饱和和整流绕组因整流元件的开关引起的电流变化对交流绕组电压波形畸变率和直流电压的影响 ,将电机的多回路理论与有限元方法结合建立了交直流混合供电同步发电机的数学模型 ,利用关联变换建立绕组、整流桥与负载间的联接。对发电机不同负载时的稳态性能进行了仿真 ,该法考虑了由于凸极效应、磁路饱和、绕组布置以及定转子齿槽的影响产生的空间谐波磁场的作用。计算结果与实验结果进行了比较证明了数学模型的正确性     

六相30°相带绕组的同步发电机

本文论述六相30°相带绕组同步发电机的基本原理和特点,研究包含高众谐波的定子电流产生的磁势谐波的特征和规律,并分析了在超巨型汽轮发电机和带整流负载的同步发电机上采用六相30°相带绕组的一系列优点。文中介绍了在50千伏安试验电机上进行试验的部分结果,并提出应用这种电机必须研究的课题。     

分数槽永磁同步电动机稳态参数的计算

针对具有场域结构对称，场分布不对称特征的工程类问题，提出新型有限元降价技术，该技术可将Ｎ阶有限元方法降价为２个具有相同刚度矩阵的０．５Ｎ阶有限元方程大大节省了计算机内丰空间和ＣＰＵ时间，为了提高计算的准确性，采用负载法计算稳态参数，该方法不仅考虑了实际工上磁性材料的饱和情况同时也考虑了ｄ，ｑ轴之间磁场的相互作用，文章还处理非线性收敛问题以及嵌套迭代收敛问题，收敛速度明显提高，最后给出了应用实例及计     

汽轮发电机稳态负序工况仿真模型及其对负序损耗计算结果的影响

稳态负序能力是大型汽轮发电机安全可靠运行的重要技术指标之一,而稳态负序损耗的准确计算是确定稳态负序能力的关键和基础。介绍了模拟发电机稳态负序运行工况的传统模型,针对其不足提出了一种新的不对称负载模型,并对2种模型所反映的物理机理和优缺点进行了对比分析。在此基础上,以一台1 550 MW的大型4极核能汽轮发电机为例,采用场路耦合的二维非线性时步有限元方法,结合2种仿真模型对其稳态负序损耗分别进行了计算,并对计算结果进行了详细分析。结果表明:相对于传统的负序模型,笔者提出的不对称负载模型充分考虑了磁饱和与转子附加损耗的影响,计算出的稳态负序损耗更接近实际情况,为准确考核大型汽轮发电机的稳态负序能力奠定了基础。     

Semihex~(TM)单相感应电动机阻容制动的仿真研究

根据SemihexTM接线方式和三相感应发电机的稳态等效电路,利用对称分量法导出SemihexTM联接单相感应电动机最小激磁电压下的阻容元件参数计算式,用最优化算法进行计算;建立了SemihexTM单相感应电动机在α-β坐标系下的瞬态数学模型,编制计算机仿真程序,通过实例对电动机带通风机负载时的阻容制动瞬态过程进行仿真计算.仿真结果表明:SemihexTM单相感应电动机的阻容制动适合于各类性质的负载,特别适合于具有摩擦阻尼性负载和轻恒转矩负载机械的制动停车.     

带脉冲负载电池储能系统的源载耦合建模

针对带脉冲负载的电池储能系统（battery energy storage system with pulsed load，BESS-PL）源载耦合和脉冲特性建模问题，采用状态空间法和信号平均法分别构建了BESS-PL源载耦合精确模型和平均模型，基于此提出了一种准精确建模方法，对高频分量合理简化，保留了BESS-PL特有的脉冲特性，从而构建BESS-PL源载耦合准精确模型。通过稳定性理论分析和仿真，对比3种BESS-PL源载耦合数学模型的特点和不同适用情况。其中，基于平均模型推导BESS-PL系统的稳态传递函数，利用波特图分析讨论脉冲占空比和DC/DC变换器开关占空比对稳定性的影响规律；结合3种模型仿真，分析了BESS-PL系统关键参量和源载功率的关联规律、脉动特性及占空比对稳定性的影响规律。3种建模方法可灵活用于BESS-PL系统源载耦合特性和脉冲特性的暂稳态分析。     

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