中点箝位型逆变器控制方法的综合研究

本文深入研究了空间矢量调制模式下的三电平逆变器中点电压波动的机理，建立了平均中点电流数学模型，为中点电压平衡控制提供了理论依据，并提出基于电压中矢量合成的中点电压平衡控制方法，该方法对于系统动态过程中出现的电压不平衡，可以通过调整冗余小矢量的相对作用时间进行补偿，由于电压中矢量的部分作用时间被均分给相应的小矢量，因此其补偿效果明显。实验结果证实了本文研究方法的正确性。     

NPC型三电平逆变器SVPWM算法及中点电压平衡控制的研究

为解决二极管箝位型(NPc)三电平逆变器中点电压平衡问题,文中详细介绍了三电平逆变器空间矢量调制算法的基本原理,从空间矢量控制的角度分析了中点电压波动的基本规律,提出了一种有效抑制中点电压波动的算法。该算法依照中点电荷守恒原理,通过检测输出三相电流和中点电压波动值,推导出用于精确调节中点电压小矢量冗余开关状态的分配因子表达式。仿真结果验证了该方法的可行性和精确性。     

基于TMS320LF2407三电平逆变器SVPWM研究

研究了二极管钳位型三电平逆变器的中点电压平衡控制方法.建立了三电平逆变器的综合数学模型,提出了一种采用最近三矢量法合成参考矢量的空间矢量脉宽调制SVPWM算法,给出了小三角形区域判断规则、合成参考电压矢量的相应输出电压矢量的作用顺序,并推导出各合成电压矢量的作用时间.探讨了影响三电平逆变器中点电压平衡的主要因素,提出了...     

三电平变换器SVPWM算法综述

本文介绍了三电平空间矢量脉宽调制（SVPWM）的基本原理,根据空间矢量调制的规律,重点介绍了五种三电平SVPWM算法,并对它们各自的特点进行了分析,包括古典算法;参考电压分解SVPWM算法;基于线电压坐标系的SVPWM算法;基于60°坐标系的SVPWM算法：基于120°坐标系的SVPWM算法。最后针对上述五种算法,对三电平变换器中点电压的平衡控制进行了研究。     

基于改进SVPWM的三电平NPC逆变器中点电压平衡的研究

三电平NPC逆变器具有直流电压利用率高、开关耐压低、输出电压谐波低等优点而被应用于高压大功率场合。而中点电压平衡问题一直是三电平NPC逆变器研究的关键。文中在传统的空间矢量调制方法的基础上进行改进,不改变原来矢量的模长,对各扇区的不同小三角形内影响中点电位的中、小矢量进行重新分配和虚拟,理论上能完全消除电压矢量对中点电位的影响,该方法的中点电压平衡能力在全调制度范围内控制灵活且有效。通过仿真和实验验证了所提方法的正确性。     

基于矢量合成的三电平PWM整流器脉宽调制技术的研究

介绍了二极管中点箝位型三电平PWM整流器电路的拓扑结构和传统的空间矢量脉宽调制(SVPWM)的基本原理。分析了一种小矢量合成虚拟空间矢量的三电平SVPWM脉宽调制方法,并把它与基于冗余小矢量的中点电位滞环控制策略相结合,从而更好的控制中点电位的波动。为避免参考电压矢量在扇区切换中输出矢量突变,采用了一种首发矢量全部采用正小矢量或负小矢量的空间矢量调制算法。最后把调制策略应用到三电平整流器中进行仿真分析,仿真结果验证了调制策略的正确性和有效性。     

三电平变流器高电压穿越下的中点电压控制研究

针对高电压穿越条件,分析中点钳位型三电平变流器的中点电压数学模型,推导出三相功率与零序电压的传递函数。提出一种新型的注入零序电压控制方案,该方案通过控制中点处的零序总功率为0,来实现中点电压的平衡控制。具体方案是,通过计算中点处的三相功率偏差,经PI调节器输出零序电压调制波,经过3s/2s坐标变换,叠加至三相基波调制波,并采用SVPWM调制算法实现。仿真显示,该方案能够实现中点电压的平衡控制,具有较好的动态响应。     

SVPWM控制三电平逆变器

论述了空间电压矢量调制（SVPWM）控制二极管钳位式三电平逆变器的原理与实现方法。提出了确定参考矢量的三个规则，并推导出工作矢量作用时间、输出顺序及描述了中点电位的控制规则。通过采用Matlab仿真，结果证明SVPWM控制三电平逆变器的可行性。     

三电平变频器中点电位控制策略研究

三电平变频器以其优越的性能,特别是在大功率伺服系统中的应用,以逐渐淘汰两电平变频器。在三电平sVPwM控制中,关键问题之一是直流侧中点电位波动的问题,中点电位的波动直接影响输出波形的质量。文章通过对NPC型三电平sVPWM控制中各矢量作用状态的研究,以逆变器为例,深入分析了直流侧中点电位波动的原因,给出了矢量合成时中点电压平衡区域。通过改进SVPWM算法实现了中点电位的控制,使其更加平稳。     

基于DSP-CPLD的三电平逆变器SVPWM方法研究

三电平中点箝位逆变器在高压大容量变频调速中得到了广泛的研究和应用,文中对二极管箝位型三电平逆变器的控制系统进行研究并介绍采用CPLD与DSP的组合来实现三电平逆变器空间矢量发生的一个方法。这种方法可以控制中点电位平衡,限制输出电压dw／dt。试验结果体现了该方法的可行性。     

Resolution Enhancement Technology:Integrated Process Solutions using OPC

DUV lithography, using the 248 nm wavelength, is a viable manufacturing option for devices with features at 130 nm and less. Given the low kl value of the lithography, integrated process development is a necessary method for achieving acceptable process latitude. The application of assist features for rule based OPC requires the simultaneous optimization of the mask, illumination optics and the resist.Described in this paper are the details involved in optimizing each of these aspects for line and space imaging.A reference pitch is first chosen to determine how the optics will be set. The ideal sigma setting is determined by a simple geometrically derived expression. The inner and outer machine settings are determined, in turn,with the simulation of a figure of merit. The maximum value of the response surface of this FOM occurs at the optimal sigma settings. Experimental confirmation of this is shown in the paper.Assist features are used to modify the aerial image of the more isolated images on the mask. The effect that the diffraction of the scattering bars (SBs) has on the image intensity distribution is explained. Rules for determining the size and placement of SBs are also given.Resist is optimized for use with off-axis illumination and assist features. A general explanation of the material' s effect is discussed along with the affect on the through-pitch bias. The paper culminates with the showing of the lithographic results from the fully optimized system.     

Cost-effective test solutions for smart card and other integrated flash applications

From its emergence in the late 1980s as a lower cost alternative to early EEPROM technologies, flash memory has evolved to higher densities and speedsand rapidly growing acceptance in mobile applications.In the process, flash memory devices have placed increased test requirements on manufacturers. Today, as flash device test grows in importance in China, manufacturers face growing pressure for reduced cost-oftest, increased throughput and greater return on investment for test equipment. At the same time, the move to integrated flash packages for contactless smart card applications adds a significant further challenge to manufacturers seeking rapid, low-cost test.     

Theoretical analysis of the relationship between the Brillouin gain coefficient and the strain in the optical-fiber sensors

The relation between the power of the Brillouin signal and the strain is one of the bases of the distributed fiber sensors of temperature and strain. The coefficient of the Bfillouin gain can be changed by the temperature and the strain that will affect the power of the Brillouin scattering. The relation between the change of the Brillouin gain coefficient and the strain is thought to be linear by many researchers. However, it is not always linear based on the theoretical analysis and numerical simulation. Therefore, errors will be caused if the relation between the change of the Brillouin gain coefficient and the strain is regarded as to be linear approximately for measuring the temperature and the strain. For this reason, the influence of the parameters on the Brillouin gain coefficient is proposed through theoretical analysis and numerical simulation.     

An improved parallel thinning algorithm with two subiterations

The parallel thinning algorithm with two subiterations is improved in this paper. By analyzing the notions of connected components and passes, a conclusion is drawn that the number of passes and the number of eight-connected components are equal. Then the expression of the number of eight-connected components is obtained which replaces the old one in the algorithm. And a reserving condition is proposed by experiments, which alleviates the excess deletion where a diagonal line and a beeline intersect. The experimental results demonstrate that the thinned curve is almost located in the middle of the original curve connectivelv with single pixel width and the processing speed is high.     

Novel fiber-optical interferometer with miniaturized probe for in-hole measurements

Today, micro-system technology and the development of new MEMS （Micro-Electro-Mechanical Systems） are emerging rapidly. In order for this development to become a success in the long run, measurement systems have to ensure product quality. Most often, MEMS have to be tested by means of functionality or destructive tests. One reason for this is that there are no suitable systems or sensing probes available which can be used for the measurement of quasi inaccessible features like small holes or cavities. We present a measurement system that could be used for these kinds of measurements. The system combines a fiber optical, miniaturized sensing probe with low-coherence interferometry, so that absolute distance measurements with nanometer accuracy are possible.     

Development of the readout system for waveguide multilayer optical card

Waveguide multilayer optical card （WMOC） is a novel storage device of three-dimensional optical information. An advanced readout system fitting for the WMOC is introduced in this paper. The hardware mainly consists of the light source for reading, WMOC, motorized stages addressing unit, microscope imaging unit, CCD detecting unit and PC controlling ＆ processing unit. The movement of the precision motorized stage is controlled by the computer through Visual Basic （VB） language in software. A control panel is also designed to get the layer address and the page address through which the position of the motorized stages can be changed. The WMOC readout system is easy to manage and the readout result is directly displayed on computer monitor.     

Study of waveguide coupling efficiency in hybrid silicon lasers

This paper presents a new method to increase the waveguide coupling efficiency in hybrid silicon lasers. We find that the propagation constant of the InGaAsP emitting layer can be equal to that of the Si resonant layer through improving the design size of the InP waveguide. The coupling power achieves 42% of the total power in the hybrid lasers when the thickness of the bonding layer is 100 nm. Our result is very close to 50% of the total power reported by Intel when the thickness of the thin bonding layer is less than 5 nm. Therefore, our invariable coupling power technique is simpler than Intel＇s.     

Collinear phase-matching study of terahertz-wave generation via difference frequency mixed in GaAs and Inp

The collinearly phase-matching condition of terahertz-wave generation via difference frequency mixed in GaAs and InP is theoretically studied. In collinear phase-matching, the optimum phase-matching wave hands of these two crystals are calculated. The optimum phase-matching wave bands in GaAs and lnP are 0.95-1.38μm and 0.7-0.96μm respectively. The influence of the wavelength choice of the pump wave on the coherent length in THz-wave tuning is also discussed. The influence of the temperature alteration on the phase-matching and the temperature tuning properties in GaAs crystal are calculated and analyzed. It can serve for the following experiments as a theoretical evidence and a reference as well.     

Effects of the alloy compositions on the phonon-polaritons in ternary mixed crystals

Composition dependence of bulk and surface phonon-polaritons in ternary mixed crystals are studied in the framework of the modified random-element-isodisplacement model and the Bom-Huang approximation. The numerical results for Several Ⅱ - Ⅵ and Ⅲ- Ⅴ compound systems are performed, and the polariton frequencies as functions of the compositions for ternary mixed crystals AlxGa1-xAs, GaPxAS1-x, ZnSxSe1-x, GaAsxSb1-x, GaxIn1-xP, and ZnxCd1-xS as examples are given and discussed. The results show that the dependence of the energies of two branches of bulk phonon-polaritons which have phonon-like characteristics, and surface phonon-polaritons on the compositions of ternary mixed crystals are nonlinear and different from those of the corresponding binary systems.     

New insert layer structure OLEDs

An insert layer structure organic electroluminescent device（OLED） based on a new luminescent material （Zn（salen）） is fabricated. The configuration of the device is ITO/CuPc/NPD/Zn（salen）/Liq/LiF/A1/CuPc/NPD/Zn（salen）/Liq/LiF/A1. Effective insert electrode layers comprising LiF（1nm）/Al（5 nm） are used as a single semitransparent mirror, and bilayer cathode LiF（1 nm）/A1（100 nm） is used as a reflecting mirror. The two mirrors form a Fabry-Perot microcavity and two emissive units. The maximum brightness and luminous efficiency reach 674 cd/m^2 and 2.652 cd/A, respectively, which are 2.1 and 3.7 times higher than the conventional device, respectively. The superior brightness and luminous efficiency over conventional single-unit devices are attributed to microcavity effect.