级联H桥整流器直流侧电压平衡控制策略

针对电力电子变压器的重要前置组成部分级联H桥整流器的输出电压平衡问题,提出一种基于模拟控制单元和数字控制单元相结合的电压平衡模块化控制策略.所提控制策略由模拟控制单元和数字控制单元构成,模拟控制单元为双闭环控制,外环为比例积分控制,内环为滞环控制,实现所有H桥单元输出总电压的无误差控制及功率因数校正;数字控制单元通过排...     

小容值单相H桥级联型STATCOM纹波电流分析

采用薄膜电容的小容值单相H桥级联型STATCOM具有高可靠性的优点,但容值减小会造成直流侧波动电压随补偿容量增大而变大,而直流侧波动电压对STATCOM电流纹波又具有直接的影响。为明晰容值减小对H桥级联STATCOM纹波电流的影响,文中对单相小容值H桥级联型STATCOM系统电流纹波进行研究。基于单相小容值H桥级联型STATCOM控制系统,采用时序分析的方法建立载波相移脉宽调制的电流纹波表达式,通过数值分析定量研究容值对电流纹波的影响。研究结果表明,电容容值减小不会增大纹波电流。仿真实验验证了理论分析的正确性,为单相小容值H桥级联型STATCOM的设计提供理论参考。     

级联型有源滤波器均压控制方法的研究

研究了级联型H桥有源滤波器（Active Power Filter,APF）的拓扑结构与控制方法;基于级联有源滤波器直流侧电压失衡问题,提出了一种分层控制思想,顶层主要是实现有功指令电流跟踪和相间电压的均衡,底层控制则是实现相内各H桥模块电压的均衡,从而有效的解决了相间电压和相内电压的均衡问题;使用仿真软件PSCAD/ EMTDC初步实现了该控制策略的仿真验证;最后,搭建以DSP+FPGA为控制核心的实验平台并进行试验验证。     

基于DSP组合式变频器的设计

介绍了基于DSP的三相航空变频电源的设计原理和方法。采用电压型PWM整流器、高频链逆变器和周波变流器级联组合,使整机开关最大程度地实现了软开关,可靠解决了周波变流器的换流问题。实验结果表明,该变换器设计合理,具有较高的功率因数和可靠性。     

基于级联H桥整流器的双闭环解耦控制策略研究

针对级联式电力电子变压器模块的功率、电流失调以及工作状态不平衡所造成的控制策略无法设定的问题,本文以单相d-q矢量转换技术为理论基础,引入虚拟相,并引入了双闭环控制理论,建立了电流内环控制器与电流外环控制器,实现了级联H桥整流器各模块共同占空比的控制策略。最后通过仿真实验进行验证。实验结果显示,本文提出方案能够有效减少无功损失,提升电能输送效率,增强系统运行的稳定性。     

基于LPC2214的ZVZCS-PWM全桥变换控制器的研究

针对传统ZVZCS-PWMDC／DC全桥变换器在实现滞后桥臂开关管零电流开关过程中,存在着辅助谐振电路附加损耗较大,软开关实现方式复杂,功率开关管电压应力和电流应力高等缺点,介绍了一种新型次级箝位移相控制的ZVZCSPWMDC／DC全桥变换器。文中分析了该变换器实现软开关的原理,同时设计了变换器数字控制系统,控制器采用LPC2214型ARM芯片,并通过一台实验样机验证了这种软开关变换器相关理论的正确性以及该数字控制系统的可行性。     

新型软件锁相环的三相电压型PWM整流器的控制

在电网电压频率波动或者三相不平衡的情况下,硬件锁相很难检测到基波正序的相位。文中在结合PWM整流器空间矢量解耦控制算法的基础上,将软件锁相环技术应用在PWM整流器控制算法中,并用仿真和实验验证了该方案的可行性。实验结果表明,该算法解决电网电压频率波动及三相不平衡时相位同步等问题,并在工程上具有一定参考价值。     

多谐振软开关全桥Boost变换器

提出一种利用多谐振实现开关管软开关的全桥Boost变换器.其将变压器漏感作为谐振电感,利用电感与电容谐振实现桥臂开关管和箝位开关管的软开关.桥臂开关管工作于零电流开通与零电压关断状态.有源箝位电路既可抑制变换器工作时可能出现的振荡电压,又可将箝位电容吸收的能量返还回主电路,且箝位开关管工作于零电压开通与零电流关断状态.最后利用硬件实验验证了其多谐振软开关特性.     

三相四开关整流器的研制

三相四开关整流器拓扑具有功率器件少、成本低、装置体积小、效率高和开关损耗低等优点,同时又可作为三相六开关整流器故障时的容错拓扑,因此三相四开关整流器受到广泛关注.本文首先介绍了三相四开关整流器的主电路,并且提出一种电流前馈型解耦的电压电流双闭环控制策略.为了抑制直流侧两电容电压不平衡的情况,采用了一种前馈补偿的控制策略...     

电流型零电压开关节能整流器

为解决电流型脉冲宽度调制（Pulse Width Modulation,PWM）整流器在高开关频率下硬切换时的开关损耗问题,提出了一种电流型零电压开关节能整流器,其辅助谐振电路位于直流环节,且与直流母线并联,只有1个辅助开关.在换流过程中,主开关能实现零电压切换,辅助开关能实现零电流切换,而且当整流器采用多电平PWM控制策略时,辅助电路在每个开关周期只需工作1次.分析了谐振换流过程,仿真结果表明特征仿真波形符合理论分析,开关器件切换时处于软开关状态,整流器能平稳运行.该电流型零电压开关节能整流器可以在高开关频率和大功率的应用场合实现高效率运行.     

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.