纳秒级高压脉冲电源的研究

设计一种应用于挥发性有机气体脱除的高压窄脉冲电源,利用脉冲变压器组合低压开关和两级磁压缩电路输出纳秒级电压脉冲,利用窄脉冲放电产生等离子体,实现污染废气脱除的节能性与高效性.通过原理分析与理论推导,研究系统参数对电源性能的影响并完成关键参数设计.最后在实验室搭建电源样机,实验表明系统可以产生上升沿为760 ns,幅值为70 kV的电压脉冲,验证了理论分析与设计的正确性.     

双级矩阵变换器混合式换流

针对双级矩阵变换器(TSMC)整流级窄脉冲处四步换流失效和宽脉冲处零电流换流较难追踪覆盖的不足,提出一种混合式换流方案,将脉冲分为宽窄脉冲,宽脉冲下采用四步换流策略,窄脉冲处采用零电流协调换流,零电流换流协调会导致逆变级载波为动态不规则波形,较难实现,提供了一种依据整流级开关占空比调整逆变级信号波的简易实现方法,分析了原理,给出了示意图.搭建了一台样机对上述方案进行了实验验证,结果表明该方案的采用在确保系统具有优良网侧和传动性能的同时,实现了安全可靠换流,从而有效消除了由上述问题导致的过电流/过电压尖峰,提高了系统可靠性,为TSMC进一步工程应用奠定了基础.     

开关串联型高压纳秒级双极性脉冲功率电源研究

与直流高压除尘相比,高压脉冲除尘具有更好的除尘效果且能耗更低.为提高脉冲电源系统效率及功率密度等指标,需输出纳秒级高频高压脉冲.基于固态开关器件串联拓扑,设计了一种高压纳秒级双极性脉冲功率电源.基于脉冲电源拓扑和工作原理,首先详细分析并设计了电源各部分组件参数,然后通过仿真验证了方案的有效性.最后搭建了脉冲功率电源样机进行实验验证,测试结果表明,脉冲电源能够输出幅值0～±4 kV、脉冲上升沿约58 ns、下降沿约175 ns、脉宽10 ns～100 μs可调的高压快速脉冲,验证了理论分析与设计的正确性.     

基于PSM技术高压脉冲电源的模拟实验

PSM控制方法是通过多组PWM脉冲信号按一定的控制时序步进控制众多串联的直流斩波器循环工作,并调制它们的输出电压脉冲宽度来实现总输出电压的调整.基于PSM技术和开关器件的高压脉冲直流电源系统构成简单,操作简洁,能够实现输出高功率,且具有系统输出级储能小,关断时间短,维护方便等特点.本文通过6开关模块PSM电源的仿真和实验,实现了PSM控制模式和高功率的输出,为进一步开发中国环流器2号A装置(HL-2A)60kV/1MW/3s二级加热高压脉冲电源提供了坚实的基础.     

具有在线诊断机制的指令脉冲发生器的设计研究

为解决指令脉冲发生器的精确性与可靠性问题,给出一种具有实时诊断机制的指令脉冲发生器的设计思想与实现方法。结合基于ＰＣ总线的ＣＮＣ系统,介绍了这种指令脉冲发生器的多通道应用实例。     

全固态纳秒脉冲发生器控制系统设计

应用脉冲频率响应法检测电力变压器绕组变形,需要脉冲发生器作为检测系统激励[1-2]。基于FPGA的多参数可调全固态纳秒级脉冲发生器是众多脉冲发生器中较为先进的一种,FPGA控制系统作为此种脉冲发生器的控制核心,具有调控脉冲电压幅值,控制脉冲重复频率与宽度以及系统过流保护等功能。设计合理的控制电路对整个脉冲发生器性能优劣起到至关重要的作用。针对此脉冲发生器的控制电路重点分析了脉冲发生器的脉冲触发控制,电压控制设计以及过流保护控制等三部分功能。最后通过实验结果证明在此控制电路控制下脉冲发生器可调整脉冲参数,系统安全性较高。为进一步利用脉冲频率响应法检测变压器绕组变形奠定了基础。     

新型软开关脉冲MAG焊逆变电源的研究

根据脉冲MAG焊工艺特点,脉冲焊电源必须具有良好的动态特性、较大功率输出以及较高的可靠性.由于零电压软开关电路拓扑结构简单,软开关控制的实现简易可靠,因而特别适合较大功率焊接应用场合.本文通过对传统脉冲逆变焊机优、缺点的分析,并基于对相移式全桥零电压软开关电路基础理论的系统讨论,提出了一种适合脉冲MAG焊工艺的零电压软开关电路拓扑,并对其工作机理进行了系统研究.试验测试证明,所设计的新型软开关脉冲MAG焊逆变电源具有全范围的软开关能力,其开关损耗低、外特性良好,符合焊接工艺的要求.     

CDMA2000 1x基带成形滤波器——一种低复杂度的设计和实现

本文采用查找表法实现了cdma20001x脉冲成形滤波器,相对于传统的滤波器设计方法,本文充分利用了滤波器系数对称的特性,并考虑到4倍过采样是采用内插三个零来完成这一特点,巧妙设计了数据查找存储表,节省了大量硬件资源.整个系统用verilog HDL语言RTL级描述.系统经过了FPGA验证并给出了仿真结果.     

双极性微弧电沉积电源系统研制

为满足微弧氧化和阴极微弧电沉积两种涂层制备工艺的共同需求,设计了一种双极性直流脉冲电源系统,该电源系统由主回路和控制系统组成,主回路采用两级结构,前级为三相全桥整流部分,包括三相全桥晶闸管整流电路及其触发电路,输出连续可调的直流电压;后级为逆变电路,包括全桥逆变电路,驱动电路以及脉冲波形发生器的设计,保证输出频率、占空比可调的双极性脉冲波形;控制系统采用双闭环结构,内环为电压环,外环为电流环,采用PI控制算法,实现恒流、恒压控制.     

基于H桥-MPC电路的高压脉冲发生器设计

针对强电磁脉冲用于工业及生活污水有机物降解研究,设计并研制了采用H桥式逆变电路和磁脉冲压缩(MPC)电路为核心结构的小型高重复频率高压脉冲发生器.该装置输出电压脉冲为双指数电压波,脉宽为纳秒到微秒级别可调,上升前沿时间为纳秒级,脉冲峰值为0～20 kV,脉冲重复频率为0～300 Hz.采用H桥电路结构,初级储能电容可直接连接充电电源,省去缓冲电路.绝缘栅双极型晶体管(IGBT)在零电流和零电压条件下关断,关断损耗非常小.经实验证实电压和电流上升时间及脉冲宽度都为百纳秒级,电压峰值可接近20 kV.所设计电源很好的满足了污水放电有机物质降解的研究及应用,此外还可以推广到其他研究及工业应用领域,如气体放电等离子体研宄等.这里的研究对高压脉冲发生器的设计、研制及应用具有一定的指导意义.     

微波高速开关的开关时间测量方法研究

随着电子技术的迅速发展,开关的带宽越来越宽,开关的速度越来越快,微波高速开关的开关时间可以达到几百皮秒。传统的测量方法无法测量如此高速开关的开关时间,本文提出了一种新方法测量高速微波开关的开关时间,利用带宽为70GHz的取样示波器通过观测开关的包络信号,然后编写相应的测量软件把观测的包络信号进行解调,并自动测量开关时间,从而测量几纳秒甚至皮秒级的开关时间,最后进行了实验验证。     

一种测量纳米材料高频特性的新方法

本文介绍一种使用同轴线制备简易高频测试平台、运用射频设备测量纳米尺度样品高频性能的方法。使用该方法,窄脉冲射频信号在传输线中的延时测量精度达到10皮秒左右,发现了铜芯同轴传输线与多壁碳管同轴传输线的传输特性的区别。这一方法有可能推广到测试其他小尺度样品高频特性的研究中。     

Internet在电力市场中的应用

首先简要论述了在电力市场环境下为确保电力系统的安全、可靠运行而对信息的要求，阐明了信息系统应该具有的特征与功能，指出了Internet是理想的解决办法。之后，介绍了与Internet相关的一些事务，重点放在如何保征Internet的性能和安全性方面。在此基础上，概述了电力市场中Internet的应用现状，介绍了Internet应用的一个重要分支(即Web服务方面)的研究与技术进展情况及其可能对将来Internet在电力市场中的应用所带来的影响。最后，介绍了应用服务提供者模型并展望了其在电力市场中广阔的应用前景。     

计及管道特性的调压室三维流场计算研究

本文对两侧各接有较长管道的调压室系统实现了管道特征线法和调压室三维非定常流动的联合计算,即建立了联合计算模型,其调压室底部与管道连接处通过迭代计算而获得有机衔接。将其结果与建立在一维压力平衡原则基础上的调压室（一维）模型的计算结果进行比较,在一维模型孔口阻尼取值合适时,两者计算结果有很好的一致性。验证了用调压室一维模型来描述调压室的动态特性,有较好的准确度。但混合模型的计算结果能反映调压室孔口等部位的结构形式对流动的影响,从而使结果能更基础地显示调压井真实的动态性能。     

Spot optical measurements on micromachined mirrors for photonic switching

This paper describes and compares three optical methods for performing spot measurements on micromachined mirrors, designed for photonic switching in fiberoptic networks. For static characterization, two spot-position detection systems, one based on a vidicon camera and the other based on a bidimensional silicon position sensitive detector (PSD), are illustrated, tested, and compared. Moreover, the dynamic behavior has been monitored with the PSD-based detection arrangement and with a semiconductor laser feedback interferometer. Advantages and drawbacks of these methods are highlighted. Testing is reported on torsional, silicon micromachined mirrors, with a single degree of freedom. High dc voltage for static measurements, and sinusoidal or white-noise or step excitation for dynamic characterization, have been used for mirror driving.     

Screening attenuation of conducting and ferromagnetic hollow cylinders of finite length

The shielding effectiveness of thin-walled hollow cylinders of finite length in a homogeneous magnetic field with arbitrary direction is determined analytically. Both cylinders with finite conductivity and superconducting as well as ferromagnetic cylinders are examined for this purpose. As a result, the screening attenuation on the axis of a superconducting cylinder in a longitudinal magnetic field turned out to be identical with the screening attenuation on the axis of a ferromagnetic cylinder with a transverse magnetic field. We show how to determine the corresponding values along the cylinder axis on the basis of the shielding in the cylinder center by way of simple approximations. To illustrate the analysis, the lines of magnetic flux for longitudinal field incidence, the equipotential lines for transversal field incidence and the lines of induced eddy currents for the case of a conducting cylinder are shown.     

Featured Article: Use of Microhotplates in the Controlled Growth and Characterization of Metal Oxides for Chemical Sensing

Microhotplates are micromachined platforms with integrated heaters and contact electrodes that can be used as miniature substrates for metal oxide film growth. Fabricated as arrays, they enable efficient combinatorial studies to be performed on a single chip. A variety of growth methods are compatible with their use, including evaporation, sputtering, chemical vapor deposition, and deposition from pastes or sol gels using screen printing, drop deposition, or spin-coating. The microheater on each element may be used to control the temperature during deposition or for a post-annealing step such as sintering, while the film contact electrodes serve as a built-in monitor of the fabrication process. In chemical vapor deposition using arrays, the elements with heaters set above the lowest nucleation temperature for a given precursor are the only ones that will have film deposited on them, resulting in a kind of self-lithography. This review gives examples of different methods of film growth that have been employed on microhotplates with applications for chemical sensing, with an emphasis on the chemical vapor deposition method.     

浸润式与强迫内冷结合的蒸发冷却汽轮发电机定子三维温度场计算

汽轮发电机定子采用浸润式与强迫内冷结合的新型蒸发冷却技术优越于传统的其它冷却方式,可以为电机的运行提供安全、可靠和高效的绝缘及冷却效果,相应地有必要对定子温度场进行准确的计算分析以满足进一步应用的要求。该文以1台应用该冷却系统运行的50MW汽轮发电机的定子为研究对象,首次建立了较完整的定子三维温度场的仿真数学模型,采用数值模拟与试验对比分析的方法,对定子绕组内冷、负荷变化以及冷凝器工况等因素对电机温度场的影响进行了研究,得到了新型蒸发冷却电机定子温度场的分布规律。仿真结果与试验数据吻合较好,为蒸发冷却技术在大型汽轮发电机中的进一步应用提供了理论依据。     

Specifics of heat and mass transfer in spherical dimples under the effect of external factors

The specifics are examined of heat transfer enhancement with spherical dimples under the effect of factors important for practice and characteristic of cooling systems of gas-turbine engines and power units. This experimental investigation deals with the effect of the following factors on the flow in a channel with hemispherical dimples: continuous air swirl in an annulus with dimples on its concave wall, dimples on the convex or concave wall of a curved rectangular channel, imposition of regular velocity fluctuations on the external flow in a straight rectangular channel, and adverse or favorable pressure gradient along the flow direction. The flow is turbulent. Reynolds numbers based on the channel hydraulic diameter are on the order of 10⁴. Results of the investigation of a model of a two-cavity diffuser dimple proposed by the authors are presented. It has been found that results for channels with spherical dimples and for smooth channels differ not only quantitatively but also qualitatively. Thus, if the effect of centrifugal mass forces on convex and concave surfaces with hemispherical dimples and in a smooth channel is almost the same (quantitative and qualitative indicators are identical), the pressure gradient in the flow direction brings about the drastically opposite results. At the same time, the quantitative contribution to a change in heat transfer in hemispherical dimples is different and depends on the impact type. The results are discussed with the use of physical models created on the basis of the results of flow visualization studies and data on the turbulence intensity, pressure coefficient, etc. Results of the investigations suggest that application of spherical dimples under nonstandard conditions requires the calculated heat transfer to be corrected to account for one or another effect.     

Technological Assessment and Forecasting for Electrical Engineering Education: A Proposed Relevance "Tree"

Technological assessment and then an educated forecast of what the future will bring have been used with various degrees of success for research planning by various agencies of the government and industry for a number of years. This paper presents the starting structure for an assessment of electrical engineering education. The structure in the form of a relevance tree is presented with major branches of programs, content, and form. Further breakdowns of the branches with a culmination in very specific elements of electrical engineering education are illustrated with figures and discussed in the text. The paper concludes with a request for assistance on detailed assessments on the very specific elements in the tree.