三相SVPWM逆变电源输出波形优化控制策略

为了提高三相逆变电源的电压输出波形质量,减少输出电压的谐波分量和总畸变率,提出模糊神经元PID控制策略。以DSP芯片为控制系统核心,对输出电压进行Clarke和Park矢量变换,采用人工神经网络方法与PID控制理论构成神经元PID控制器,对PID控制器参数进行在线调整,将模糊控制理论引入神经元PID控制器形成模糊神经元PID控制策略,并将基于60°坐标系的SVPWM算法用于逆变电源控制系统中,对系统稳态负载、动态负载、不对称负载情况下分别进行仿真实验。仿真结果表明:采用模糊神经元PID控制策略控制下的三相SVPWM逆变电源,在不同负载情况下的输出电压谐波分量小,总畸变率少,达到电压输出波形质量性能要求。     

三相UPS输出电压不平衡控制的研究与实现

三相电压的对称输出是衡量交流电源性能的一个重要指标.为了在不平衡负载和非线性负载等条件下获得高质量的输出电压波形,分析了三相UPS输出电压不平衡的机理,提出了在正/负序同步参考坐标系下,应用基于DSP的重复控制与PI控制的复合控制方案,功率开关管采用空间矢量调制(SVPWM)方式,基本消除了负序电压分量,有效地抑制了零序电压分量和谐波分量.研制了30～500kVA UPS样机,实验结果验证了控制方案的有效性。     

三相四桥臂逆变器的复合控制

随着风能、太阳能等清洁能源在电网中的应用,逆变器不可或缺.电网中的谐波和不平衡负载影响电网的电能质量,因此逆变器的控制策略及控制方法尤为重要.为提高电能质量,以三相四桥臂逆变器为模型,提出了比例积分PI、矢量谐振(vector resonant,VR)控制和重复(repetitive control,RC)控制相结合的复合控制方法.其中比例积分控制器能够抑制直流分量的干扰;矢量谐振控制器能够抑制特定频率且含量较高的谐波;重复控制器抑制多次且含量较低的谐波并减小稳态误差.仿真结果验证了所提控制方法能有效提高逆变器输出电压电流波形质量.     

三相UPS输出电压的一种新型控制方案

为了提高UPS电源输出电压波形质量,建立了带隔离变压器的三相UPS状态空间解耦模型.根据PID控制的快速响应性和重复控制的无静差跟踪特性,提出了一种新型的三相UPS输出电压重复控制与PD复合控制的方案,并对控制系统进行了稳定性分析.改进型重复控制器结构简单,易于实现.试制了30KVA三相UPS样机,主控制器为32位DSP TMS320F2812.实验结果表明了在线性和非线性负载情况下,系统均具有良好的稳态和动态特性,输出电压总谐波畸变(THD)较小.     

三相逆变电源在不平衡负载条件下的控制研究

三相输出电压对称是对三相逆变电源的重要要求之一,在三相逆变电源中,输出电压不对称主要是由于三相负载的不平衡引起的.本文基于对称分量法和叠加原理对三相逆变电源在不平衡负载下产生三相输出电压不对称的机理进行了系统的分析,得到了输出电压正、负、零序分量不同的补偿特性.设计了一个简单可行的同步正负序参考系控制器,有效地补偿了不平衡负载引起的逆变电源输出电压畸变,保证了逆变电源在任意不平衡负载下均能维持三相平衡的输出电压.论文最后通过Matlab仿真结果验证了理论分析和所提出的控制方法的正确性.     

模糊自整定 PI 控制的 EPS 研究与设计

针对应急电源带非线性负载时存在波形畸变和负载切换动态性能差等问题, 通过对系统带有不同负载传 递函数的分析, 提出了模糊自整定 PI 控制与三闭环控制相结合的复合控制策略。 通过系统仿真, 将该复合控 制策略应用于 DSP(Digital Signal Processing)控制的 1 kW 应急电源样机上。 实验结果表明, 该控制策略具有良 好的动态性能和较强的谐波抑制能力。     

有源电力滤波器电流环无静差控制策略研究

本文对传统的电流环复合控制器的检测误差进行了理论分析,指出了检测负载侧电流的局限性,设计了基于传统PI控制和指定谐波指令相结合的电流控制器。该控制器基本上可以做到谐波指令的无静差跟踪,具有良好的补偿性能,克服了传统检测负载侧谐波电流时PI控制器的缺陷,而且具有传统检测负载侧谐波电流的灵活性。即使负载谐波电流高于有源电力滤波器的容量,该控制策略也能够总体上无静差输出,具有一定的理论意义和工程应用价值,理论分析和仿真验证了此种新型控制策略的正确性和有效性。     

采用比例谐振和状态反馈的三相逆变器最优控制

针对常规线性二次型调节器方法设计的三相逆变器控制系统无法实现指令跟踪,而根据线性二次型最优跟踪方法设计的控制系统虽然能实现指令跟踪,却无法消除系统非线性模型带来的稳态误差这个问题,提出了一种比例谐振和状态反馈控制策略.该策略根据内模原理,首先将输出反馈转化为状态反馈,其次将线性二次型最优控制的输出跟踪问题转化为状态调节器问题,从而解决了线性二次型调节器方法解决指令跟踪问题的两个不足,成功对三相逆变器控制参数进行了最优整定,通过仿真和430 kW样机验证了该策略不仅实现了指令跟踪要求,而且消除了稳态误差,控制系统具有良好的稳态和动态性能,输出电压总谐波畸变率小于1％,带30％不平衡负载时电压不平衡度小于1.5％.     

SPWM逆变器复合控制策略研究

为了解决由于直流输入电压波动,带非线性负载和死区效应引起的单相逆变电源输出电压波形畸变率大,品质下降的问题.将迭代学习控制应用到逆变器波形控制中,提出了一种基于迭代学习控制和双闭环PI控制相结合的逆变器新型复合控制策略.运用极点配置对PI控制器参数进行设计.采用双闭环PI控制提高逆变器的动态特性,利用迭代学习控制改善逆变器的稳态精度.最后借助Mat-lab仿真软件进行仿真验证,仿真结果表明,该策略能获得具有良好的动态和稳态特性的波形.     

基于PID和重复控制的三相四桥臂逆变器的研究

在三相四桥臂逆变器被解耦成三个单相逆变器的基础上,提出了一种PID与重复控制相结合的控制策略.首先采用开关周期平均法和旋转坐标变换,建立旋转坐标系下的平均大信号模型,在此模型的基础上设计简单明了的PID控制器.其次对整个系统进行重复控制器的设计,居于外环的重复控制可以减小周期性扰动产生的畸变,提高系统的稳态性能.仿真结果表明,在不平衡负载和非线性负载情况下,逆变器都能够保持完好的电压输出特性和良好的动态特性.     

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.     

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     

An affordable accurate evaluation of the binding conformations predicted by molecular docking studies in bio-system

Franck-Condon factors bridge the gap between theoretical modeling and experimental observations for molecular electronic spectroscopy and electron transfer.Under the displaced harmonic oscillator approximation,multidimensional Franck-Condon factors are decomposed into a product of many one-dimensional(1D)Franck-Condon(FC)factors,and each 1D-FC factor is associated with one Huang-Rhys factor that determines the leading contribution of     

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