电动汽车充电机高压直流接触器及其控制电路性能测试分析

在电动汽车直流充电机中需要多个750V/20A电源模块并联输出供电动汽车充电,而电源模块与充电枪之间需要通过直流接触器控制电路的通断.直流接触器的性能直接影响电动汽车能否安全、可靠地充电.分析了直流接触器及其控制电路的工作原理,介绍了750V/200A直流接触器的电气性能的测试方法.根据测试的逻辑波形分析了双枪直流充电机直流接触器的功耗(节能性),通过对功耗的计算,为直流接触器控制线圈的供电电源选型提供了参考依据.为了验证直流接触器满载运行的电气寿命,防止直流接触器在电动汽车满载充电时发生炸裂,进行了直流接触器的满载运行切断实验并对其逻辑波形进行了分析.测试结果表明,该型直流接触器性能合格,其控制电路符合要求.     

一种自均流多模组大功率电源并联技术

针对大功率直流电源模块并联运行时的均流问题,阐述了一种应用于大功率直流电源模块并联系统的数字化控制均流技术,给出了并联系统的结构.通过分析并联系统的环流、功率调节特性等,提出了一种每一个子模块都独立采用双闭环反馈控制的技术.通过仿真与实验,该自均流并联系统可构成恒压电源及恒流电源,输出电压、电流误差分别小于0.83%和0.53%,模块之间电流不均衡度小于3.78%,稳定性好、瞬态响应快.     

由光伏直接供电的电动汽车无线充电系统控制策略

为提升光伏发电的就地消纳能力,弥补电动汽车有线充电存在的弊端,通过提出一种含电动汽车无线充电的直流微网拓扑结构,研究了由光伏直接向电动汽车供电的控制方法。该拓扑以光伏发电系统为基础,新增了以蓄电池、超级电容器组成的混合储能模块,光伏系统在为充电站自身负荷供电的同时,向电动汽车供电,对系统中各部分进行优化并提出相应控制策略。Simulink仿真与实验结果表明:混合储能模块可有效平抑光伏输出功率的波动;磁耦合谐振式无线电能传输方式可提高电动汽车充电效果;在保证电动汽车稳定充电的基础上促进了光伏消纳。验证了所提拓扑的可行性与控制策略的有效性。     

数字化交错并联BOOST PFC在车载充电机中的研究

为了减少电动汽车充电时对电网的谐波污染,必须对充电设备进行功率因数较正。针对3k W的电动汽车车载充电机,前级PFC电路采用了交错并联Boost PFC拓扑和数字平均电流法的双闭环控制设计方案。着重分析了主电路拓扑结构、器件设计以及数字化的控制策略。最后,通过MATLAB仿真与3.2k W样机验证,数字控制的交错并联Boost PFC电路实现功率因数为1,输出电压纹波与输入电流纹波均低于5%,满足车载充电的同时减少电网的谐波污染。     

复合电源系统电动汽车性能敏感度研究

为研究锂电池与超级电容复合电源系统配置和电动汽车性能的关系,提出了单因素变化敏感度分析方法.建立了基于功率跟随式能量控制策略的锂电池与超级电容复合电源系统仿真模型,研究复合电源系统配置变化对电动汽车性能的影响.仿真结果表明:锂电池串联数量对电动汽车性能影响很小,敏感度在-0.041~0.099之间;超级电容串、并联数量对电动汽车最高车速影响较大,敏感度在0.180~0.277之间;超级电容串联数量对电动汽车加速性能影响最大,敏感度在-0.862~-0.650之间;超级电容并联数量对加速性能影响较大,敏感度在-0.289~-0.154之间;复合电源系统配置对能耗影响很小,敏感度在-0.041~0.057之间.实验测试结果验证了结论的有效性,可为改善电动汽车性能提供设计依据.     

一种城市电动公交客车制动能量回馈方法

为提高汽车能源利用率,提出一种电回馈制动与机械摩擦制动相结合的城市电动公交客车制动能量回馈方法.采用可控制实现串并联实时切换的超级电容器模块作为电源,当电动公交客车驱动运行时,控制超级电容器模块串联放电提供能量;而当电动公交客车制动运行时,控制超级电容器模块并联充电回馈能量.在制动初始阶段,采用电回馈制动,电动机发电运行并提供恒制动扭矩,当电动机转速减至不能提供恒制动扭矩时,由机械制动提供制动力直至制动过程结束.仿真和试验结果证明:提出的制动能量回馈方法可实现低速制动能量回馈,具有较高的制动能量回馈效率.     

车用内置式永磁同步电机损耗最小控制研究

降低内置式永磁同步电机的损耗,提高系统的效率,对于提高电动汽车的一次充电续驶里程具有重要意义。文中研究了计及铁损的内置式永磁同步电机损耗最小控制策略,与id=0及最大转矩比电流控制策略相比,电驱动系统效率有所提高,系统仿真和实验验证了所研控制策略的有效性,该控制策略在新能源电动汽车上有较好的应用价值。     

以MMC接口互联的交直流混合微电网协同预充电控制

研究了交直流混合型微电网中MMC的启动预充电控制策略,讨论了联网以及孤岛运行模式下子模块电容电压的建立过程.联网运行模式下采用交流子网充电;孤岛运行模式下,根据黑启动电源的分布情况以及储能单元的荷电状态来选择预充电方式.通过MATLAB/Simulink仿真对不同运行工况的预充电策略加以验证,结果表明该预充电控制策略保证了系统不同运行方式下电容电压的稳定,实时性较好,充电速度较快.     

大功率白光LED高效均流并联供电系统

为解决可见光通信系统中的白光LED(Light Emitting Devices)光源高效稳定的直流偏置电源问题, 设计并研制了一种Buck型双DC/DC(Direst Cunent)并联供电系统。该系统采用ARM7(LPC2148)作为主控制器, 利用电压反馈调整两个DC/DC 模块的PWM(Pulse Width Modulation)驱动信号的占空比实现稳压, 利用两个PMOS (P-channel Metal-Oxide-Semiconductor)电子开关分别控制两个DC/DC支路实现均流。实验结果表明, 电源实际输出电压与设定值的误差小于2%, 两个支路电流的偏差小于1%, 电源供电效率可达75%~80%。在电源开启和关断瞬间的瞬时测试结果显示, 驱动电压无尖峰现象, 电压从0上升至1.6 V的时间约为20 s, 关电降至0 的时间约为65 s。两个DC/DC模块交替工作, 延长了供电系统的使用寿命。该供电系统在LED照明和可见光通信设备中具有良好的应用前景, 为设计多DC/DC模块的高效均流并联供电系统提供了解决方案。     

智能电网环境下多电动汽车协同充电优化调度算法

大量电动汽车通过居民侧家庭能源管理系统接入电网充电时,若各用户独自对充电过程进行优化,会使充电负荷集中在低电价时段,形成巨大的负荷峰值,造成变压器和线路严重超载,威胁电力系统的稳定运行。引入了一种智能电网环境下电动汽车协同充电模式,建立了最小化用户用电费用的最优充电模型,提出了一种多电动汽车协同充电优化调度算法。该算法能有效避免用户独自优化调度时出现的弊端,同时显著降低用户的充电费用。通过仿真实验验证了算法的有效性。     

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.     

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