改进型滑模扰动观测器的感应电机控制系统

针对传统PI调节器在负载剧烈突变时控制性能不佳及使用传统滑模观测器抖振严重的问题,文中以感应电机为研究对象,提出了一种基于滑模观测器和传统PI调节器的扰动实时补偿方案。通过改进型的扰动观测器对系统扰动进行实时观测估算,将估算出的扰动反馈至PI调节器进行前馈补偿,从而有效提高电机控制性能,改善抖振现象。文中搭建了基于MATLAB的仿真平台和TMS320F28335 DSP的实验平台,对所研究的改进滑模观测器扰动前馈补偿方法与常规单PI调节、常规滑模观测器扰动补偿进行了对比分析。该结果验证了所提方案的有效性与可行性,速度超调量优化了0.5%,响应时间为30 ms。     

双馈风力发电系统低电压穿越的建模与控制

为提高双馈感应风力发电机组并网的运行稳定性,研究电网故障下双馈风电机组的运行特性,使发电机在电网故障时仍能保持不间断的运行。本文主要研究了基于Orowbar保护控制的低电压穿越运行的控制策略,通过Orowbar保护电路来限制电压跌落时转子回路的最大电流,并通过仿真分析了电压跌落的程度和旁路电阻的取值对控制的影响。仿真结果验证了在电网电压骤降下Crowbar保护电路的有效性,可实现双馈风力发电机不间断的运行。     

基于滑模控制的异步电机无速度传感器DTC研究

建立了一种滑模速度观测器,用于电机转速的精确观测。该观测器充分利用电机状态方程具有的结构特点,设计出简单有效的速度估算方法,在转子磁链的估算中无须用到转子时间常数和转速等信息,提高了观测器对于参数误差的鲁棒性。将所建立的观测器和空间电压矢量脉宽调制技术(SVPWM)结合对电机进行控制,进一步提高了系统的调速性能。仿真结果验证了基于滑模控制理论的异步电机无速度传感器直接转矩控制系统的可行性以及对参数误差的鲁棒性。     

基于转子电流的双馈风机模糊控制无速度传感器设计

本文针对传统PI控制器调节速度慢的缺点,设计了基于转子电流的双馈风机模糊控制无速度传感器。该设计将参数自整定模糊PI控制技术引入转子速度估测模型中,以提高转子观测器的跟踪效果和动态特性。利用Matlab/Simulink搭建了仿真模型,仿真结果表明:基于转子电流的双馈风机模糊控制无速度传感器能够快速准确地估测转子速度和位置角度,具有良好的动态特性,对电机参数的变化具有一定的抗干扰能力。     

变速恒频无刷双馈风力发电机的仿真研究

在介绍无刷双馈发电机及其变速恒频风力发电系统的基础上,基于无刷双馈电机转子参考轴d-q数学模型,采用恒压频比控制策略,在Matlab/Simulink下完成无刷双馈变速恒频发电控制的开环仿真研究。仿真结果验证了无刷双馈发电机变速恒频控制技术的正确性与有效性。     

变速恒频风力发电用双PWM变换器的协调控制

文章首先分析了双馈风力发电机的原理以及其数学模型,然后分析了变速恒频风力发电技术采用双PWM变换器常规控制策略,在此基础上提出了采用双PWM变换器的协调控制策略。最后利MATLAB/SIMULINK软件对整个风力发电系统进行仿真。结果表明此策略实现了风力发电机的变速恒频运行,另外在定子电流变化的同时,保持了恒定的功率因数,实现了对双馈感应电机的有功功率和无功功率的独立控制。     

双馈风力发电系统低电压穿越的研究

针对双馈型变速恒频风力发电系统的低电压穿越问题,提出一种新颖的转子侧保护电路。在建立电机的稳态和暂态数学模型的基础上,分析了电网电压发生跌落期间以及电压恢复后的双馈感应发电机的动态响应情况。仿真结果表明,在电压跌落时转子侧加入本文设计的Crowbar电路,能够有效抑制直流侧在电压跌落时电容电压的升高,并能减弱转子侧电流...     

基于PSCAD的双馈风力发电机组低电压穿越的研究

针对双馈风力发电机组低电压穿越问题,研究了电网电压严重跌落情况下转子Crowbar电路、转子Crowbar和直流侧卸荷电路组成的组合保护电路的控制策略。基于PSCAD建立了双馈风力发电机组低电压穿越的仿真模型,验证了组合保护电路控制策略能够很好地抑制转子侧电流和直流侧电压的上升,实现低电压穿越。     

基于模型参考自适应系统的感应电机控制

采用模型参考自适应法设计了无速度传感器矢量观测器。现以电压模型为参考模型,电流模型为可调模型,推算出速度信息,计算输出控制信号,实现了对感应电机的精确控制;通过Matlab／Simulink对其进行仿真、验证,结果表明,该系统对定子磁链观测精度高,速度估计准确,改善了电机的控制特性。     

考虑无功支撑的双馈风机高电压穿越控制策略

本文针对目前HVRT控制策略的不足之处,提出了一种基于双馈感应发电机(DFIG)的HVRT控制策略。分析了电压骤升故障下DFIG的暂态过程,为改善故障后转子过电流,提出了转子侧模拟电感控制策略,修正了等效阻抗值的范围,并设计了一种网侧与转子侧协同无功控制方式,满足了电网故障下无功支持的需求。最后将传统控制策略与本文控制策略进行了仿真对比,证明了该控制策略在提高HVRT性能方面的有效性和优越性。     

聚对苯撑苯并双(口恶)唑发光及其器件制备

采用光谱技术,研究了聚对苯撑苯并双(口恶)唑(PBO)溶液的光敏发光特性,并用相对法估算出溶液发光效率在50%范围.结合光谱技术、半导体电学和电化学等研究手段,具体研究了以PBO为发光层的单层电致发光器件,研究结果显示,电致发光与薄膜的光致发光有具有相同的发光中心,峰值位于510 nm左右.同时发现,由于存制备过程中不同处理条件使得不同厚度薄膜残留的掺杂物质浓度不同,从而引起薄膜的导电性的不同.使得器件的阈值场强随PBO厚度的减小而逐渐增加.     

系统级封装新型埋入式电源滤波结构的研究

在高密度小尺寸的系统级封装(SiP)中,对供电系统的完整性要求越来越高,多芯片共用一个电源网路所产生的电压抖动除了会影响到芯片的正常工作,还会通过供电网路干扰到临近电路和其他敏感电路,导致芯片误动作,以及信号完整性和其他电磁干扰问题.这种电压抖动所占频带相当宽,几百MHz到几个GHz的中频电源噪声普通方法很难去除.结合埋入式电容和电源分割方法的特点,提出一种新型高性能埋入式电源低通滤波结构直接替代电源/地平面.研究表明,在0.65～4GHz的频带内隔离深度可达-40～75 dB,电源阻抗均在0.25ohm以下,实现了宽频高隔离度的高性能滤波作用.分别用电磁场和广义传输线两种仿真器模拟,高频等效电路模型分析这种低通滤波器的工作原理以及结构对隔离性能的影响,并进行了实验验证.     

Emerging interconnects: a state-of-the-art review and emerging solutions

Aluminium was a primary material for interconnection in integrated circuits (ICs) since their inception. Later, copper was introduced as interconnect material which has better metallic conductivity and resistance to electromigration. As the aggressive technology scaling continues, the copper resistivity increased because of size effects, which causes increase in delay, power dissipation and electromigration. The need to reduce the resistor-capacitor??????? delay, dynamic power utilisation and the crosstalk commotion is as of now the fundamental main impetus behind the presentation of new materials. The purpose of this paper is to do a survey of interconnect material used in IC from introduction of ICs to till date. This paper studies and reviews new materials available for interconnect application which are optical interconnects, carbon nanotube (CNT), graphene nanoribbons (GNRs) and silicon nanowires which are alternatives to copper. While doing a survey of interconnect material, it is found that multiwalled CNTs, multilayer GNR and mixed CNT bundles are promising candidates and are ultimate choice that can strongly address the problems faced by copper but on integration basis copper would last for coming years.     

Arsenic deposition as a precursor layer on silicon (211) and (311) surfaces

We investigate the properties of arsenic (As) covered Si(211) and Si(311) surfaces by analyzing data from x-ray photoelectron spectroscopy (XPS) and low-energy electron diffraction (LEED) images. We then create a model using total surface energy calculations. It was found that both Si(211) and Si(311) had 0.68±0.08 surface As coverage. Si(211) had 0.28±0.04 Te coverage and Si(311) had 0.24±0.04 Te coverage. The Si(211) surface replaces the terrace and trench Si atoms with As for a lower surface energy, while the Si edge atoms form dimers. The Si(311) surface replaces all terrace atoms and adsorbs an As dimer every other edge site. These configurations imply an improvement in the mean migration path from the bare silicon surface by allowing the impinging atoms for the next epitaxial layer, tellurium (Te), to bind at every other pair of edge atoms, and not the step terrace sites. This would ensure a nonpolar, B-face growth.     

光子晶体微腔发光二极管

光子晶体微腔因其具有增强自发辐射、定向输出和单模工作的能力而受到广泛关注。介绍了光子晶体微腔发光二极管的基本原理、设计、特性、制作及其典型器件。     

Comparative study of maximum power point tracking techniques for hybrid renewable energy system

The power generation demand is increasing day-by-day throughout the world, therefore, the use of hybrid systems becomes a significant solution. The hybrid renewable energy system (HRES) is used for delivering power in various regions in order to overcome intermittence of wind and solar resources. Because of increasing environmental problems, for example, greenhouse gas emission and energy cost have interested novel research into substitute methods in favour of electrical power generation. Maximum Power Point Tracking (MPPT) control method is a vast deal of novel research used for enhancing the efficiency of HRES. The authors have revealed that the hybrid techniques i.e. Global MPPT, fuzzy-neuro systems, Adaptive Neuro-Fuzzy Inference System (ANFIS), Perturbed and Observe (P&O) + Adaptive Neural Network (ANN) etc. can provide best results as compared to other MPPT control methods. This paper offering a state of art review of MPPT control techniques for HRES.     

用于单光子TOF测量的时间-幅度变换器

基于新型共源共栅电流源的积分方法,设计了一种用于单光子飞行时间(TOF)测量的时间-幅度变换器(TAC)。该方法有效简化了TAC电路结构,减小了TAC占用面积,显著提高了TOF的满量程范围(FSR)。采用0.18 μm标准CMOS工艺设计。集成TAC的单光子探测器像素单元的填充因子可达到26.8%。后仿真结果表明,该TAC在120 ns的FSR内具有230 ps的定时分辨率,微分非线性(DNL)低于0.05 LSB,积分非线性(INL)低于1.1 LSB。蒙特卡洛仿真表明,512个TAC像素间的不均匀性低于0.5 %。该TAC非常适用于高密度时间相关的单光子计数(TCSPC)探测器阵列。     

Joint estimation of TOA and DOA in IR-UWB system using a successive propagator method

Impulse radio ultra-wideband (IR-UWB) ranging and positioning require accurate estimation of time-of-arrival (TOA) and direction-of-arrival (DOA). With receiver of two antennas, both of the TOA and DOA parameters can be estimated via two-dimensional (2D) propagator method (PM), in which the 2D spectral peak searching, however, renders much higher computational complexity. This paper proposes a successive PM algorithm for joint TOA and DOA estimation in IR-UWB system to avoid 2D spectral peak searching. The proposed algorithm firstly gets the initial TOA estimates in the two antennas from the propagation matrix, then utilises successively one-dimensional (1D) local searches to achieve the estimation of TOAs in the two antennas, and finally obtains the DOA estimates via the difference in the TOAs between the two antennas. The proposed algorithm, which only requires 1D local searches, can avoid the high computational cost in 2D-PM algorithm. Furthermore, the proposed algorithm can obtain automatically paired parameters and has better joint TOA and DOA estimation performance than conventional PM algorithm, estimation of signal parameters via rotational invariance techniques algorithm and matrix pencil algorithm. Meanwhile, it has very close parameter estimation to that of 2D-PM algorithm. We have also derived the mean square error of TOA and DOA estimation of the proposed algorithm and the Cramer-Rao bound of TOA and DOA estimation in this paper. The simulation results verify the usefulness of the proposed algorithm.     

多孔硅发光机制的分析

从量子力学的基本理论出发讨论了量子限制效应，推导出多孔硅有效禁带宽度增量并用量子限制效应和表面态及其物质在发光中作用的理论解释了ＰＳ光致发光的实验现象。     

一种基于分段CRC的LDPC译码的改进算法

级联多个循环冗余校验(CRC)的LDPC译码算法有效地改善了译码的收敛特性。然而在其译码算法中,当CRC检测的整体漏检概率不够低时,出现误码平台。因此,该文提出了改进算法,通过减少在译码算法中CRC检测的次数,降低整体漏检概率,提高了误码性能。仿真表明改进的算法提高了误码性能,译码复杂度也增加不大。