Modeling of the electrical parameters of a wire-cylinderelectrostatic precipitator under pulse energization

Modeling of the electrical parameters of an electrostatic precipitator (ESP) with dust loading under pulse energization is difficult, and little progress has been made in the past. A method for modeling a wire-cylinder ESP under pulse energization based on the characteristics of Trichel pulses, and a means of dealing with the particle charging under such conditions are presented. The quantitative studies of the interactions between ion space charge and particle charging and their influence on the electric potential and field distributions have been numerically obtained under nanosecond pulse energization. The results show that the time-averaged current increased with applied peak voltage, pulsewidth, and pulse frequency and decreased with increased dust loading as expected. The space-charge density distribution was significantly influenced by the dust loading under pulse energization conditions. The proposed model is valid as long as the width of the applied voltage is less than 1 μs     

Polyethylene under electrical stress

Fifty years ago, the concept of an intrinsic electric strength for insulating solids was fashionable. It was supported by the sophisticated theoretical models of von Hippel, Frohlich and others for the interaction of electrons with crystal lattices in an electric field. The models came to be applied, rather implausibly perhaps, to polymers such as semi-crystalline polyethylene (PE). In that climate, the work of van Roggen on the high-field conductivity of single lamellar crystals of PE was notable. Since then, the picture of the insulating properties of PE has had to be painted with an increasingly complex palette in which the electrical elements have had to be supplemented by mechanical, chemical, and optical ones. The present review of the conducting properties of the polymer considers these other features, but concludes that the fundamental characteristics of the lamellar PE crystal are still the determining factors.     

碾压混凝土单轴动态力学性能研究

考虑到地震作用下大体积碾压混凝土结构响应的特点,对两种级配的碾压混凝土进行了单向应力状态下的动态拉、压试验,系统研究了应变速率对碾压混凝土单轴强度及变形特性的影响,分析了在不同应变速率下强度、峰值应变、极限应变以及弹性模量等特性的变化规律及其发生机理。结合碾压混凝土动态强度增量、弹性模量、峰值应变等与应变率之间的拟合公式,给出了描述碾压混凝土在不同应变速率下应力-应变全曲线的表达式,并对碾压混凝土的动态破坏过程进行了探讨,为开展碾压混凝土高坝的动力反应分析打下了基础。     

Analysis of nano-scale MOSFET including uniaxial and biaxial strain

In this paper, we focus on uniaxial and biaxial strain technologies, and we also investigate an optimum combination of strain method and channel direction. We linked the first principles band calculation program to the FUJITSU ensemble full band Monte Carlo simulator FALCON directly, which enables to incorporate arbitrary Si band structures such as uniaxial and biaxial strained-Si into device characteristics analysis. We show that the combination of biaxial tensile strain and <100> current for NMOS, and compressive uniaxial strain and <110> channel for PMOS are optimum methods for current enhancement. However, considering technological difficulties and process cost, it is one of the candidate methods to use the combination of uniaxial tensile strain and <100> channel direction for NMOS and that of uniaxial compressive strain and <110> channel direction for PMOS.     

发电系统可靠性随可靠性参数和电气参数变化规律建模

为了快速求取负荷或元件可靠性参数变化后系统的可靠性指标,深入分析了发电系统可靠性指标随负荷变化的曲线,选取合适的函数对可靠性指标和负荷进行坐标变换,使变换后的变量之间近似满足二次函数关系,对经坐标变换后的自变量和因变量建立一元二次回归模型,然后再进行坐标的逆变换,从而得到发电系统可靠性指标关于系统负荷的回归方程.对算例结果进行显著性检验,结果表明各可靠性指标回归方程的F检验值均大于F0.01,说明回归方程具有高度显著性.此外,还建立了发电系统可靠性指标随机组可靠性参数变化的多元非线性回归模型.这2个模型不仅揭示了发电系统可靠性指标与负荷和机组可靠性参数之间的变化规律,还可以用来估计参数变化后系统的可靠性以及预测系统未来某时刻的可靠性.     

Degradation of insulating materials under electrical stress

An avalanche of physical and physicochemical phenomena, often self-sustained, leads to the end of life of an insulating material. The collapse of the insulating role of a material is mostly due to the electrical field stress. The path leading from the catastrophic situation, the breakdown, back to its origin is followed in the present paper. A defect, pre-existing or created by the in-service stresses, gives rise to an ionization process in a volume bounded by insulating walls. With time the process does not remain identical due to both changes in the material and gas evolution, which makes it difficult to interpret the detected electrical signal. The end of life will occur through microcracks in which new discharges are initiated, activating the propagation of these structural failures. This change of structure of the insulating material when due to the existence of water molecules will lead to the same kind of final degradation. The polymeric insulating materials could contain additives but they lead only to a partial healing. From polymers of low complexity such as the PE used in cables, assuming that there is no pre-existing defect, one endeavors to understand how a microstructure reacts with a local field or accumulated charges. The present paper summarizes the thoughts of the author pertaining to the problems of aging and dielectric breakdown in organic insulating materials, processes often given a concrete form through experiments.     

Physical modeling of hole mobility in silicon inversion layers under uniaxial stress

A physical model for hole mobility under either biaxial or uniaxial stress has been developed. The six-band k ? p theory is used to obtain the bandstructure through stress-dependent Hamiltonian. The hole mobility in the silicon inversion layer is studied in details using Monte Carlo method. A numerically robust method has been applied to achieve self-consistent solution of Poisson’s and Schrödinger equations.     

基于Matlab的功率MOSFET建模

针对Matlab/PSB中MOSFET的理想开关模型的不足,提出了一种以功率MOSFET输出特性曲线为核心建立其特性模型的方法。该模型不但能精确模拟稳态的各种特性,也能够描述开关瞬态的过程。将模型应用于固态开关的仿真中,仿真结果与实验波形证明了该模型的正确性与准确性。     

碳化硅MOSFET的变温度参数建模

为在全温度范围内准确反映碳化硅(silicon carbide,SiC)MOSFET的工作特性,提出一种基于Pspice仿真软件的SiC MOSFET变温度参数模型。该模型中引入温控电压源和温控电流源以补偿SiC MOSFET静态特性随温度的变化,同时着重考虑了SiC MOSFET的低温特性和驱动电路负压的影响。详细阐述建模原理,分析各个关键参数对SiCMOSFET静态特性及动态特性的影响,给出建模原理。搭建基于Buck变换器的SiC MOSFET测试实验样机,在不同电压点、电流点及温度点(25-125℃)下进行实验测试,并将测试结果与基于变温度参数Pspice模型的仿真波形和损耗估算结果进行比较。比较结果高度吻合,功率损耗误差在10%以内,验证了提出的变温度参数模型的准确性和有效性,为实际应用中采用SiC MOSFET器件进行系统分析和效率评估提供了重要的依据。     

固体氧化物燃料电池电堆电特性的建模

为了满足固体氧化物燃料电池(solid oxide fuel cell,SOFC)系统快速跟踪外部负载变化的要求,需要对SOFC电堆的输出功率进行合理的控制,因此建立一个面向控制的精确SOFC电堆数学模型来表征SOFC电堆的电特性就显得十分必要。通过对SOFC实验数据的分析发现SOFC电堆中单片电池存在电耦合现象,基于这种现象建立了一种SOFC电堆电特性的电耦合模型,然后设计出一种改进的遗传算法对其进行参数辨识,实验结果显示这种数学模型有较高辨识的精度,证明了该种模型的合理性,为SOFC电堆输出功率的精准调节奠定了良好的基础。     

考虑变温度影响的SiC MOSFET建模与分析

为了准确反映SiC MOSFET在不同温度下的电气特性,对影响SiC MOSFET电气特性的关键参数进行了分析,提出了一种SiC MOSFET等效电路模型。首先,根据SiC MOSFET阈值电压和跨导随温度变化的规律,采用函数拟合的温控电源模型对SiC MOSFET的阈值电压和漏极电流进行补偿;其次,考虑寄生电容与极间电压的关系,采用电容子电路和可变电容模型对SiC MOSFET的寄生电容进行等效模拟,根据SiC MOSFET体二极管对其静、动态特性的影响,利用独立二极管模型描述体二极管特性,进而建立SiC MOSFET的等效电路模型。最后,在不同温度条件下,对该模型进行了仿真并与实验测试结果进行了对比。结果表明所建模型较为准确地描述SiC MOSFET在较宽温度范围内的静、动态特性,验证了模型的有效性。     

Compact Modeling of MOSFET Wearout Mechanisms for Circuit-Reliability Simulation

The integration density of state-of-the-art electronic systems is limited by the reliability of the manufactured integrated circuits at a desired circuit density. Design rules, operating voltages, frequencies, and temperatures are precisely chosen to ensure correct product functional operation over its intended lifetime. Thus, in order to obtain the overall performance and functionality bounded by various design and manufacturing constraints, the integrated circuit reliability must be modeled and analyzed at the very beginning of design stages. This paper reviews some of the most important intrinsic wearout mechanisms of MOSFETs (including hot-carrier injection, time-dependent dielectric breakdown, and negative bias temperature instability) and introduces new accelerated-lifetime and SPICE compact models of these wearout mechanisms. Based on these circuit-aging models, a new SPICE reliability simulation approach is proposed and demonstrated with a simplified SRAM design on a commercial 90-nm technology to help designers understand device-failure behaviors, predict circuit reliability, and improve product robustness.     

新型电刺激仪中反馈功能的实现

主要完成了治疗脑卒中偏瘫患者的反馈式电刺激仪中的肌电反馈系统的设计,创新性地实现生物反馈与功能性电刺激相结合,避免常规电刺激的被动性和盲目性。设计了肌电信号的采集与预处理模块,并采用了有效值检测方案,提取肌电信号的特征量,将其作为反馈量与预设值进行比较,由微处理器控制刺激脉冲的输出,从而实现智能式电刺激治疗。由实验可知,设计方案正确可行,实现了反馈刺激功能。     

基于PSpice的SiC MOSFET的关键参数建模

分析研究了SiC金属氧化物半导体场效晶体管(MOSFET)各参数与其动、静态特性的内在关系,提出了一种基于PSpice的SiC MOSFET建模新方法。通过引入电压控制电压源对栅极阈值电压进行补偿修正,采用两种不同的结电容模型描述各端电压不同而带来的结电容的变化,并同时增加了MOSFET的漏源电阻、栅极电阻随温度变化的变温度子模型。新模型可全面准确反映SiC MOSFET的动、静态特性,为SiC MOSFET的开关过程分析、损耗计算及主电路设计提供了重要依据。     

Virtual reality applied to a full simulator of electrical sub-stations

This paper presents an application designed to train electrical sub-station operators by means of a virtual reality environment.     

计及温度影响的SiC MOSFET芯片热网络建模

针对雪崩工况下碳化硅(SiC)金属-氧化物-半导体场效应晶体管(MOSFET)芯片温升大影响材料热参数变化,往往导致温度计算不准确的问题,提出计及材料热参数温度依赖性的芯片瞬态热网络模型.首先,分析SiC MOSFET芯片材料的温度依赖性,采用多项式拟合获取热参数随温度变化规律;其次,利用扫描电子显微镜获取SiC MO...     

碳化硅MOSFET电热耦合模型及分析

为在Matlab/Simulink环境下准确预测碳化硅Si C(silicon carbide)功率器件在实际工况下的结温变化,针对Si C MOSFET器件提出了一种基于时变温度反馈的电热耦合模型建模方法。该方法能更好地反映Si C MOSFET在导通和开关过程中的性能特点,模型从器件物理分析和工作机理出发,将功率损耗和热网络模块引入建模,实时反馈器件结温和更新温度相关参数。采用CREE C2M0160120D Si C MOSFET器件进行测试,根据制造商数据手册和测试实验中提取,仿真结果证实了该建模方法的正确性,为器件的寿命预测和可靠性评估提供了研究基础。     

Space charge in XLPE power cable under dc electrical stress andheat treatment

It is well known that the existence and accumulation of space charge in insulation can be harmful to polymer power cable. Although there is much research done on space charge distribution in various samples, there are still some important problems left unsolved, such as the mechanism of formation and elimination of space charge in dielectrics. Because of its superiority, the pulsed electro-acoustic (PEA) measurement method is used widely in the measurement of space charge in various geometries of samples such as the multiple layer plate and cylindrical cables. The space charge in crosslinked polyethylene (XLPE) power cable under dc voltage and heat treatment is investigated by the PEA method in this paper. After heat treatment, the space charge, which previously formed in cable insulation under the applied voltage, disappears. If electrical stress is applied to the insulation again, space charge will appear once more. However, after the cable is heated and degassed in vacuum for a long time, no matter how long the dc voltage is applied to the cable, no more space charge will be formed in the cable. The mechanism of formation and elimination of space charge under the effect of electrical and thermal stress is discussed