配电网静止无功补偿器的解耦控制策略

在配电网中,静止无功补偿器(D-STATCOM)可以起到稳定接入点电压,有效地降低网损率和提高功率因数及防止非线性负荷的作用。但是D-STATCOM在d-q坐标系下是一个非线性、强耦合的系统,需要进行解耦控制,因为对其进行解耦控制可以保证输出电流快速无差地跟踪整定值。研究D-STATCOM的解耦控制策略,通过对其基本结构进行分析,得到了耦合项的模型。采用模糊免疫PI控制和前馈解耦控制相结合的方法将原系统进行线性化的解耦,避免了有功和无功电流的耦合作用。最后运用MATLAB进行仿真。仿真结果表明,所提解耦控制策略性能优良、结构简单、容易实现。     

基于Simulink永磁同步电机伺服系统矢量控制

永磁同步电机（PMSM）伺服系统的速度环和电流环具有非线性耦合特性,需要进行电流解耦控制．因此,根据矢量控制的原理实现了该系统的线性解耦．通过对永磁同步电机数学模型分析,建立基于Simulink伺服系统矢量控制仿真模型．仿真结果表明,建立的系统耦合模型具有良好速度控制特性,并对永磁同步伺服耦合系统设计具有指导价值．     

基于CMAC和PID的非线性耦合系统解耦控制研究

为了实现多变量非线性耦合系统的解耦控制,提出了一种基于CMAC与PID的复杂关联自适应解耦控制策略,并给出了详细算法。该控制策略采用PID控制器和CMAC控制器共同构成一个复合控制器,多个复合控制器通过多输入多输出线性神经网络,实施对复杂非线性耦合对象的控制作用。由于神经网络的自适应特性,可使得耦合系统逼近参考模型,实现解耦控制。仿真结果表明,该控制策略实现了耦合系统的解耦控制,并且具有较强的抗干扰能力和鲁棒性。因此采用此控制策略能够实现多变量非线性耦合系统的解耦控制。     

静止同步补偿器不平衡控制的伴生谐波与对策

采用静止同步补偿器(STATCOM)对配电系统中公共连接点处不平衡电压和电流进行控制是改善电网电能质量的一种有效方法.本研究利用开关函数基频模型,分析了STATCOM在不平衡控制时因交直流侧的调制耦合而导致STATCOM输出电流波形畸变的机理,提出了一种改进的开关函数,切断了STATCOM直流侧与交流侧的耦合通路,消除了不平衡补偿对STATCOM输出补偿电流的影响.以三相负荷不平衡控制为例,搭建了三相不平衡控制系统的仿真模型,验证了理论分析的正确性.     

三相电压型PWM整流器精确线性化和滑模控制研究

建立了同步旋转坐标系下的三相电压型PWM整流器(VSR)的非线性数学模型,针对有功电流和无功电流强耦合的特点,提出一种基于该坐标系下的电压和电流双闭环控制算法,其中电压外环采用滑模控制算法,电流内环采用状态反馈精确线性化控制策略,最后建立了仿真模型并与传统PI控制进行了对比仿真,结果表明,该复合控制方案结合了两者的优点,使VSR既具有变结构控制良好的鲁棒性,又能实现无功电流和有功电流的解耦控制,系统能保证很高的功率因数,输出电压恒定,能适应负载的扰动和非线性变化,具有很好的静动态性能。     

基于电流间接控制的STATCOM设计

给出了一种基于电流间接控制算法的STATCOM设计。叙述了STATCOM的系统结构,对电流间接控制方法进行了算法设计及仿真分析,并对STATCOM控制器的硬件设计及STATCOM系统软件设计进行了说明。     

精馏塔的神经元PID解耦控制研究

本文针对精馏塔这一多变量、非线性耦合对象,提出了一种神经元PID解耦控制方法。该方法在精馏塔精确模型补偿解耦控制基础上,采用神经元PID控制器进行控制。分析了控制器的结构及其学习算法,进行了PID和神经元解耦控制仿真实验,仿真结果表明该方法优于常规PID控制效果。     

三相电压型PWM整流器的反馈线性化和滑模控制

建立了同步旋转坐标系下的三相电压型脉宽调制(PWM)整流器(VSR)的非线性数学模型,针对有功电流和无功电流强耦合的特点,提出一种基于该坐标系的电压和电流双闭环控制算法,其中电压外环采用滑模控制算法,电流内环采用状态反馈精确线性化控制策略,最后建立了仿真模型并与传统PI控制进行了仿真对比.结果表明,该复合控制方案结合了两者的优点,使VSR既具有良好的鲁棒性,又能实现无功电流和有功电流的解耦控制,系统能保证很高的功率因数,输出电压恒定,能适应负载的扰动和非线性变化,具有很好的静动态性能.     

包含静止同步补偿器的电力系统逆系统方法

研究了包含静止同步补偿器(static synchnorous compensator,简称STATCOM)的单机-无穷大电力系统中逆系统方法的应用。首先论述了逆系统方法的基本概念,然后给出了研究对象的数学模型。将同步补偿器作为一无功电流源来处理,发电机采用二阶简化模型,在此情形下,给出了包含STATCOM的单机-无穷大系统的三阶动态模型。此时,STATCOM的等效无功电流成为系统的一个控制变量。利用逆系统算法,逐步给出被控系统的逆系统、反馈控制规律、α-阶积分逆系统、伪线性系统(积分解耦系统)。对所得解耦系统,应用最优控制方法进行综合。仿真结果显示了此方法的有效性。图2,参9。     

主动磁悬浮轴承的解耦控制

运用解耦控制策略对六自由度刚性转子主动磁悬浮轴承（ＡＭＢ）进行控制,应用基于逆系统理论的状态反馈线性化方法,设计出非线性控制器。将ＡＭＢ这一多变量、强耦合及非线性的系统,分解为６个单变量无耦合的线性子系统,并对线性子系统进行了综合。仿真表明,此控制策略实现了各自由度之间的动态解耦,系统的动态性能较传统的ＰＩＤ控制方法有明显的提高。     

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.     

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.     

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     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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