开关磁阻发电机半自励功率变换器的设计分析与验证

开关磁阻发电机的输出功率和发电效率有待提高,而功率变换器作为开关磁阻发电系统中能量转换的通道,对整个发电系统的性能改善有着重要意义,可通过对功率变换器进行设计,达到提高开关磁阻发电机输出功率和发电效率的目的。因此首先提出从励磁电压与发电电压解耦角度出发,提高励磁电压并使发电电压低于励磁电压的半自励功率变换器及其控制策略;然后通过启动运行和稳态运行仿真验证了半自励功率变换器的可行性和预防过度充电能力,通过变速、变负载仿真发现随着转速和负载电阻的提高,半自励功率变换器励磁电压与发电电压也随之提高,能够有效提高开关磁阻发电机的输出功率及发电效率,尤其低速时输出功率及发电效率有明显提高,通过单相故障运行仿真,验证了半自励功率变换器具有较强容错能力;最后实验验证了理论分析和仿真的正确性,以及提出的半自励功率变换器及其控制策略的有效性。     

开关磁阻电机调速系统功率变换器的仿真与研究

给出开关磁阻电机双开关型、公共开关型和星点型三种功率变换器的拓扑结构,分析了功率变换器拓扑结构结构特点及其工作原理。采用Matlab-Simulink软件建立了功率变换器的仿真模型,在不同脉冲信号的触发下进行系统的仿真,给出了开关磁阻电动机起动时的电流和电压曲线,并对仿真结果进行分析和研究,进而阐明了开关磁阻电机功率变换器拓扑结构的发展方向和应用前景。     

开关磁阻风力发电系统非线性仿真研究

根据磁阻发电机的工作原理并结合最大风能捕获原理,搭建了开关磁阻发电机系统的非线性仿真模型。仿真结果验证了SRG非线性模型的正确性,系统输出电压能够快速、平稳建立,恒功率输出控制效果良好。在此基础上运用模糊控制策略设计模糊控制器。优化了电机转速。     

双凸极式变绕组双模起动发电机及其电磁特性

为了拓宽开关磁阻起动发电系统调压范围,简化控制系统,提出一种双凸极式变绕组双模起动发电机;即通过绕组的变换,实现起动状态与发电状态变原理运行,在保证电机具有开关磁阻电机优良起动性能的同时,简化了发电状态的调压控制系统。基于该电机的特殊结构和控制特点,搭建带整流管的不对称功率变换模块和绕组切换模块;运用等效磁路法研究定子极弧系数对励磁绕组自感的影响规律,确定了最优定子极弧系数;应用场路联合仿真对电机起动过程和发电过程进行数值分析。通过实验验证所提出电机及控制方法的可行性和合理性。     

混合动力汽车开关磁阻集成起动/发电系统控制策略的研究

混合动力汽车开关磁阻集成起动/发电系统采用一台开关磁阻电机替代传统的起动机和发电机.运用电压、电流双闭环PID控制策略,进行起动控制、助力控制、发电控制等方面研究,利用此控制策略,系统具有起动、助力、发电功能,能提升车辆的动力性能,延长车载能源的续驶里程,提高燃油的利用率.     

一种新型车用开关磁阻起动/发电一体机系统

介绍了一种新型的汽车用开关磁阻电机起动／发电一体化系统,该系统可取代传统汽车中的分体式起动机和发电机．介绍了开关磁阻电机工作在各种状态的原理,以及相应的控制算法．采用一台1 kW6／4结构开关磁阻电机作为试验样机,以TMs320F240型DSP和EPM7128S型CPLD构成数字控制器,可实现汽车的起动、发电等功能一体化．在控制策略上,起动时以获得足够大的电磁转矩为优化目标,发电时则根据蓄电池的荷电情况自动选择恒流充电、恒压充电和浮充电．对系统进行了计算机仿真和试验研究,结果验证了硬件设计和控制策略的可行性和有效性．     

开关磁阻电动机转矩算法研究

针对开关磁阻电动机在传统控制方式下转矩出现严重波动的问题,提出了控制开关磁阻电动机的直接转矩算法,通过查询开关表选取合适的电压矢量来控制磁链大小和方向,把转矩作为直接控制量。首先,从直接转矩算法理论出发,基于Matlab/Simulink平台分别设计了直接转矩控制和电流斩波控制下的系统仿真模型;其次,在开关磁阻电动机模型和电动机负载一致的情况下,将直接转矩算法仿真结果与电流斩波算法比较;最后,通过硬件实验平台验证直接转矩算法的可行性。该研究表明,直接转矩控制下转矩脉动可以得到良好的抑制,拓宽了开关磁阻电动机的应用领域。     

开关磁阻起动／发电机控制方法研究

根据磁阻效应产生电磁转矩的机理,提出开关磁阻起动／发电机相电流斩波和角度位置控制方法,通过调节相电流斩波限及关断延时、相绕组开通励磁开关断续流相对位置,就可控制起动转矩和发电电压,不同控制参数的数值仿真分析和样机实测表明：对于低速起动状态,相电流斩波限配合固定关断延时可实现有效的恒转矩起努控制;对于高速起动状态,相电流斩波限配合固定关断延时可实现有效的恒转矩起努控制;对于调整起努状态,调节相绕组开通及关断位置角可可实现恒功率起动控制;对于发电状态,依据原动机转速和负载变化的具体情况,同时或单独调节相电流斩波限及相绕组开通、关断的位置角,可有效提高发电机稳态发电品质和动态瞬变特性。     

开关磁阻电动机及功率变换器的研究

本文叙述了开关磁阻电动机各类功率变换器电路的优缺点，提出了克服各类功率变换器缺点的方法，介绍了我们试制的磁阻电机和新功率变换器的设计思想和工作原理。新的功率变换器电路保持了不对称半桥电路的优点，允许开关电压的妆近电动机额定电压，但每相绕组只用一个开关，每个形状与电机的两相绕组连接，也介绍了用磁阻电动机定、转子极数和极弧系数决定的电感重迭系数确定磁阻电动机是否适用于新功率变换器的准则；给出了新的功率     

开关磁阻电动机电流控制方式的研究

开关磁阻电动机（ＳＲＭ）的输出转矩与绕组电流波形有密切的关系，进行开关磁阻电机驱动系统（ＳＲＤ）的电机本体设计及功率变换器、控制器的设计，必须对绕组通电电流进行深入的研究。同时要使整个系统获得预定的转矩－转速特性，必须对电流进行合理的控制，本文在对开关磁阻电机驱动系统的运行特性进行分析的基础上，深入地研究了电机绕组电流控制方法，这无疑对ＳＲＤ系统的设计与控制有较大的意义。     

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.     

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