Uniform texture in Al-Zn-Mg alloys using a coupled force field of electron wind and external load

Cylindrical Al-Zn-Mg alloys were processed by electroplastic compression with forced air cooling.Compared to a simple compression process,an unequal intensity of {110} <111> was obtained,and other textures were eliminated by electroplastic compression,that is,electroplastic compression can promote a uniform texture.The various textures formed in different regions along the radial direction under a simple compression process were illuminated by analyzing the relationship between the crystal rotation and stress state.Furthermore,the interaction between the electrons and dislocations was studied in electroplastic compression.The electrons enhanced {110} <111> by promoting slipping of the dislocations when the Burgers vectors of the dislocations were parallel to the drift direction of the electrons.However,the electrons also inhibited crystal rotation by pinning the dislocations with the Burgers vectors perpendicular to the drift direction of the electrons.Therefore,textures other than {110} <111>have difficulty forming under electroplastic compression.The effect of the current energy on the texture(enhancement or attenuation) was in accordance with the law of conservation.The results provided reasonable explanations for the test phenomena.

A Review of Power Electronics for Wind Power

The paper reviews the power electronic applications for wind energy systems.Main wind turbine systems with different generators and power electronic converters are described.The electrical topologies of wind farms with power electronic conversion are discussed.Power electronic applications for improving the performance of wind turbines and wind farms in power systems have been illustrated.

Readout electronics of a prototype spectrometer for measuring low-energy ions in solar wind plasma

Readout electronics is developed for a prototype spectrometer for in situ measurement of low-energy ions of30 e V/e–20 ke V/e in the solar wind plasma.A low-noise preamplifier/discriminator(A111F) is employed for each channel to process the signal from micro-channel plate(MCP) detectors.A high-voltage(HV) supply solution based on a HV module and a HV optocoupler is adopted to generate a fast sweeping HV and a fixed HV.Due to limitation of telemetry bandwidth in space communication,an algorithm is implemented in an FPGA(field programmable gate array) to compress the raw data.Test results show that the electronics achieves a 1 MHz event rate and a large input dynamic range of 95 p C.A slew rate of 0.8 V/ls and an integral nonlinearity of 0.7-LSB for the sweeping HV,and a precision of less than 0.8 % for the fixed HV are obtained.A vacuum beam test shows an energy resolution of 12 ± 0.7 % full width at half maximum(FWHM) is achieved,and noise counts are less than10/sec,indicating that the performance meets the physical requirement.

A Power Electronic Conditioner Using Ultracapacitors to Improve Wind Turbine Power Quality

The large variability in wind output power can adversely impact local loads that are sensitive to poor power quality. To mitigate large swings in power, the wind turbine output power can be conditioned by using a small energy buffer. A power conditioner is developed to smooth the wind power output by utilizing the energy of an electrochemical capacitor, or ultracapacitor. The conditioner is based on a single phase voltage source inverter connected between the grid inter-connection point and the ultracapacitor. The VSI shunt inverter injects or absorbs active power from the line to smooth the wind power output by utilizing the short term storage capabilities of the ultracapacitor. The ultracapacitor is connected to the DC link through a bidirectional DC-DC converter. The bidirectional DC-DC converter and VSI are constructed and field tested on a Skystream 3.7 wind turbine installed at the Missouri University of Science & Technology.

电脉冲法消除金属材料残余应力研究进展

【目的】旨在解决残余应力严重影响金属零件的力学性能和使用寿命的问题。【方法】通过对比现有残余应力消除方法的优缺点,从减少位错的角度展现电脉冲法具有的独特优势。【结果】综述了国内外学者在电脉冲法消除残余应力方面的研究现状,揭示了脉冲电流产生的电子风力和热压应力是消除残余应力的决定性因素,阐明了电子风力和热压应力促使位错开通、加速位错湮灭的机理,从而达到消除残余应力的目的。【结论】指出了电脉冲法消除残余应力的不足和改进措施,并指出了电脉冲法消除残余应力的发展趋势,为电脉冲技术的进一步研究和应用提供了理论依据。

跟构网换流器并联的海上DRU低频交流送出方案

基于不可控整流单元(DRU)的风电低频交流送出系统不具备功率返送的能力,需采用构网型换流器实现海上风电场的自组网。同时考虑传统跟网型换流器所具备的快速功率响应能力对海上风力发电带来的正面影响,以六相永磁同步电机构成的风电机组作为研究对象,阐明在风电机组内,采用两种控制策略的换流器并联经DRU低频交流送出系统的拓扑结构和运行特性。分别设计风电机组网侧换流器的构网型控制策略与跟网型控制策略,并在此基础上探讨两组网侧换流器之间的功率不平衡问题,进一步设计环流抑制策略,实现风电功率经DRU送出。通过搭建Simulink仿真模型和RT-LAB半实物仿真系统验证方案的可行性。

一种基于低速风洞大迎角装置的Cam变量赋值法

在风洞试验装置的设计和运行中,多轴同步类运动机构的控制质量直接影响着模型的运动范围、气动特性的准确性。以4 m×3 m风洞大迎角尾撑机构为例,为保证该设备的控制准确度,运动轴之间的耦合关系由“一主一从”发展为“一主多从”和“多主一从”,而传统电子凸轮存在耦合关系单一的问题。针对上述问题,提出一种基于电子凸轮的Cam变量赋值法,将基于多项式计算的轨迹生成方式和动态生成关键点型电子凸轮表相结合,使系统不再局限于单一变量引导的控制模式,极大地减少了电子凸轮之间的切换次数,降低了设备的计算负荷和运行时间,适用于需要执行多轴联动的运动机构。

基于World Wind的三江源水资源电子沙盘研究

三江源地区作为国家自然保护区,其水资源保护至关重要。本研究基于WorldWind三维GIS平台,融合海量遥感数据、数字高程数据以及水利等多源数据,采用组件开发、数据缓存、瓦片金字塔以及三维建模等技术,设计并开发水资源电子沙盘系统。以三江源地区为研究区域进行应用,结果表明:基于WorldWind构建的三江源水资源电子沙盘系统具有较好的实用性、可扩展性以及可视化效果,可为三江源地区水资源高效利用与科学管理提供技术手段支持与决策服务,同时也可为其他水利业务的电子沙盘设计开发提供参考。

电网故障时基于MMC-PET接口风力发电系统的建模与控制

近年来,电力电子变压器(power electronic transformer,PET)作为电网接口的风能转换系统,无需额外的无功补偿器便可有效地抑制由风能暂态特性引起的电压波动,引起了广泛关注。但采用传统的PET结构在电网发生故障时难以控制,当电网处于不平衡时会使得控制难度进一步增加,且难以保证系统的动态性能。因此,为提升系统动态性能,增强系统的故障穿越能力,文中提出一种基于模块化多电平换流器(modular multilevel converter,MMC)型PET的新型风能转换系统的结构与控制策略。首先,文中根据系统故障时的工作状态设计基于无源滑模控制的故障切换控制策略,采用具有斩波保护功能的子模块以及时疏解故障功率;其次,利用软件仿真和半实物仿真实验平台选取典型工况对系统进行详细的模拟研究;最后,将应用文中控制策略的新型风力发电系统与传统的风力发电系统进行对比实验,实验验证了采用文中控制策略的新型系统结构具有无功功率补偿、有效限制故障时子模块电压升高和改善电能质量等优点,且满足故障条件下电网运行的最新要求,具有优秀的故障穿越能力。

构建海上风电项目安全智能管控体系 服务涉海新业态高质量发展

根据辖区海上风电项目涉及的风险,针对保障海上风电项目的安全运行,提升其智能化管理水平,构建高效、安全、智能的海上风电项目管控体系提出建议。

光伏和风电一体化系统中的电源管理与电子电路设计

光伏和风电一体化系统可以提高可再生能源的利用效率,降低能源成本。文章重点探讨了该系统中电源管理与电子电路设计的关键技术。针对最大功率点跟踪(Maximum Power Point Tracking,MPPT)算法,比较了传统方法与基于机器学习的新型算法,并评估了其性能指标。在并网逆变器设计和储能系统集成方面,深入分析主要拓扑结构、关键参数优化以及经济性。通过一个典型工程案例,评估了系统整体性能和经济环境效益。该研究为光伏和风电一体化系统的优化设计提供了重要技术支持。

改进移相控制下PMSG-PET系统回流功率的优化

针对电力电子变压器作为风电系统并网接口系统存在回流功率的问题,通过优化电力电子变压器的控制方法,改进传统的双重移相控制方法,在传统双重移相控制的基础上,改变移相比D1、D2,使二者的组合达到最优,能够降低系统中的回流功率,提高系统效率,在Matlab中对改进控制方法后的系统进行建模与仿真。结果表明,改进前输出功率最小值大约为-5 kW,将改进后的移相控制方法应用到PMSG-PET系统中,改进后输出功率最小值大约为-1.5 kW。该控制方法能够有效降低系统回流功率,证明了改进移相控制方法的有效性。

Study of the Enhancement Events of Relativistic Electron at the Geosynchronous Orbit

The high flux of energetic electron on geostationary orbit can induce many kinds of malfunction of the satellite there, within which the bulk-charging is the most significant that several broadcast satellite failures were confirmed to be due to this effect. The electron flux on geostationary orbit varies in a large range even up to three orders accompanied the passage of interplanetary magnetic cloud and the following geomagnetic disturbances. Upon the investigation of electron flux enhancement events, two types of events were partitioned as recurrent events and random ones. Both of the two kinds of events relate to the interplanetary conditions such as solar wind parameters, IMF etc and their evolution characters as well. As for the recurrent events, we found that, (1) all of the events exhibits periodic recurrence about 27 days, (2) significant increase of electron flux relates to interplanetary index and characters of their distribution, (3) the electron flux also has relation to solar activity index. An artificial neural network was constructed to estimate the flux I day ahead. The random electron flux enhancement events are rare and present different distribution figures to the recurrent ones. The figure of the random events and the conditions of their occurrence is also discussed in this paper.

Input Parameters for Models of Energetic Electrons Fluxes at the Geostationary Orbit

The results of cross-correlation analysis between electrons fluxes (with energies of ＞ 0.6 MeV,＞ 2.0MeV and ＞ 4.0MeV), geomagnetic indices and solar wind parameters are shown in the paper. It is determined that the electron fluxes are controlled not only by the geomagnetic indices, but also by the solar wind parameters, and the solar wind velocity demonstrates the best relation with the electron fluxes.Numerical value of the relation efficiency of external parameters with the highly energetic electrons fluxes shows a periodicity. It is presented here the preliminary results of daily averaged electrons fluxes forecast for a day ahead on the basis of the model of neuron networks.

DC-DC变换器拓扑族归一化分析方法

随着风光储氢等新能源发电与电力电子技术的飞速发展,高变比、宽范围的DC-DC变换器被广泛应用,对电力电子教学中相对应部分带来很高挑战。面对种类繁多的DC-DC变换器,该文以桥式开关单元作为基本“细胞单元”,采用“细胞单元–基础拓扑结构–演化规律”的思路,利用细胞单元搭建输入与输出电压转换的桥梁,提出一种DC-DC变换器拓扑族归一化分析方法。首先提出Buck和Boost 2种桥式开关单元,并对6种非隔离型DC-DC变换器拓扑提出基于细胞单元的统一画法。提出用Buck和Boost两种单元变换去阐述其他变换器拓扑、换流方式以及电压增益的思维范式,此外2种开关单元并联可组成桥式双向单元,进而扩展为双向、交错并联、升/降压DC-DC变换器。对于隔离型DC-DC变换器,从变压器绕组与器件串联桥路的理念出发,提出4种基本开关单元,分别为绕组与(单/双)开关管/二极管串联桥路。据此给出反激、正激的构建过程,进而扩展到推挽、单有源桥式、双有源桥式及N相交错并联式DC-DC变换器。这些变换器升降压增益范围宽,串并联组合灵活,对于多类型DC-DC场合具有重要的应用价值,同时也搭建起工程应用和书本理论知识的回溯映射桥梁。

基于数控技术的棉纺环锭细纱机创新发展

研究棉纺环锭细纱机数控技术的创新应用,对比国内外先进水平环锭细纱机的发展现状及环锭细纱机的数控技术应用,分析了依托数控技术的节能主电机技术、电子牵伸技术、电子卷绕成形技术、集体落纱技术、单锭监测与自动接头机器人技术。总结了数控技术对促进环锭细纱机自动化、柔性化和智能化发展起到的重要作用。认为:高速化、长车化、柔性化、自动接头、纱线质量在线检测等将成为未来环锭细纱机的重点发展方向。

Wind Energy Conversion System from Electrical Perspective—A Survey

This paper focuses on the wind energy conversion system (WECS) with the three main electrical aspects: 1) wind turbine generators (WTGs), 2) power electronics converters (PECs) and 3) grid-connection issues. The current state of wind turbine generators are discussed and compared in some criteria along with the trends in the current WECS market, which are ‘Variable Speed’, ‘Multi-MW’ and ‘Offshore’. In addition, the other crucial component in the WECS, PECs will be discussed with its topologies available in the current WECS market along with their modulation strategies. Moreover, three main issues of the WECS associating with the grid-connection, fault-ride through (FRT) capability, harmonics/interharmonics emission and flicker, which are the power quality issues, will be discussed due to the increasing responsibility of WECS as utility power station. Some key findings from the review such as the attractiveness of BDFRG are presented in the conclusion of this paper.

机翼表面多参量一体化柔性传感器阵列

在飞行器风洞试验过程中,需要对飞行器表面的多项参数进行动态检测。传统监测系统在飞行器表面部署过程中面临着机翼外形结构受到破坏,监测参数单一化以及监测范围不足等一系列问题。对此,设计了一款机翼表面多参量一体化柔性传感器阵列系统,并针对其中流速流向解析问题提出了一种基于二维三次样条插值的流速流向解析方法,该系统能够同时采集风速、风向、温度、压力、应变等参量,并能实时显示相应监测物理量在机翼表面的分布情况。系统在NH-2风洞中进行了变风速、变迎角和变侧滑角试验,试验结果表明,该系统角度辨识分辨率能够达2°,进一步验证了系统设计的可行性和有效性,为分析飞行器表面的气动特性提供了数据支撑。

电力电子技术在风力发电中的应用

阐述电力电子技术的特点,探讨电力电子技术在风力发电中的应用,包括更新提升风电发电稳定性、保障发电的持续性、增强输电能力、降低输电损耗、保障传输安全。

面向系统电压动力学演化过程分析的电力电子并网设备内电势幅值运动机制研究

系统电压和频率演化机制认识一直是开展电力系统稳定、控制和保护等研究的重要基础。针对系统频率演化问题,已有研究以转子运动方程所刻画的内电势频率运动机制为核心形成了频率同步过程的直观认识。而针对系统电压演化问题,由于不明确驱使内电势幅值运动的激励力和支撑内电势幅值运动的物质特性,没有形成与内电势频率运动机制相对应的内电势幅值运动机制认识,更未能结合网络特性开展物理概念明确的电压动力学演化过程研究。随着电力电子设备持续大规模并网,电压问题愈加凸显,亟需更加深入地认识系统电压演化过程。因此,文中首先从设备调节内电势幅值/频率的基本原理出发,明确无功不平衡是驱使内电势幅值运动的主要激励力,并以双馈风机(doubly-fedinduction generator-based wind turbine,DFIG-based WT)为例构建无功/端电压不同控制目标下内电势幅值/频率响应模型。然后,基于三相系统动态过程中无功功率的物理内涵,建立支撑内电势幅值运动的无功不平衡存储特性的直观认识,从而通过类比频率运动机制,指出内电势幅值是反映无功不平衡存储水平的状态。最后,在含DFIG-basedWT单机系统中分析考虑不同控制目标时的电压动力学演化过程,并初步探讨多机系统电压动力学演化过程的研究思路。