Effect of Switching on Metal-Organic Interface Adhesion Relevant to Organic Electronic Devices

Considerable efforts are currently being devoted to investigation of metal-organic, organic-organic and organic-inorganic interfaces relevant to organic electronic devices such as organic light emitting diode (OLEDs), organic photovoltaic solar cells, organic field effect transistors (OFETs), organic spintronic devices and organic-based Write Once Read Many times (WORM) memory devices on both rigid and flexible substrates in laboratories around the world. The multilayer structure of these devices makes interfaces between dissimilar materials in contact and plays a prominent role in charge transport and injection efficiency which inevitably affect device performance. This paper presents results of an initial study on how switching between voltage thresholds and chemical surface treatment affects adhesion properties of a metal-organic (Au-PEDOT:PSS) contact interface in a WORM device. Contact and Tapping-mode Atomic Force Microscopy (AFM) gave surface topography, phase imaging and interface adhesion properties in addition to SEM/EDX imaging which showed that surface treatment, switching and surface roughness all appeared to be key factors in increasing interface adhesion with implications for increased device performance.

Simulation of Low-Voltage Arc Plasma During Contact Opening Progress

This paper focuses on the simulation of the low-voltage arc with an opening contact. A controllable experiment setup with a rotating contact is designed to investigate the arc behaviour. Supported by the experiment, the phenomena of arc elongation and commutation in the case of rotating contact are simulated with the dynamic grid technique introduced. Under the given condition of the external magnetic field and the contact rotating velocity, the stagnation and rapid jump of two arc roots are observed by the calculated and experimental arc root displacement. The voltage of arc column can be divided into four phases and its sharp rising progress comes from the increase of the displacement difference between two arc roots in x direction.

Power Semiconductor Devices-an Enabling Technology for Future High Efficient and High Power Density Power Conversion Systems

Power semiconductor devices are the key technology driver for all power electronic system engineering.The main development trend for power devices is going towards higher power handling capability at even smaller Sivolume, faster switching performance,advanced ruggedness and reliability at elevated operating temperature and extended SOA diagrams.To cover all applications in the various fields of industry,consumer,computing and automotive the device optimization is different for low voltage power MOSFET,for high voltage MOSFET,for plasma modulated devices and components based on wide bandgap(WB) material.In the paper,the main development trends will be described and discussed.

Measurement Process of MOSFET Device Parameters with VEE Pro Software for DP4T RF Switch

To design a Double-Pole Four-Throw (DP4T) RF switch, measurement of device parameters is required. In this DP4T RF switch CMOS is a unit cell, so with a thin oxide layer of thickness 628 ? which is measured optically. Some of the material parameters were found by the curve drawn between Capacitance versus Voltage (C-V) and Capacitance versus Frequency (C-F) with the application of Visual Engineering Environment Programming (VEE Pro). To perform the measurement processing at a distance, from the hazardous room, we use VEE Pro software. In this research, to acquire a fine result for RF MOSFET, we vary the voltage with minor increments and perform the measurements by vary the applying voltage from +5 V to –5 V and then back to +5 V again and then save this result in a data sheet with respect to temperature, voltage and frequency using this program. We have investigated the characteristics of RF MOSFET, which will be used for the wireless telecommunication systems.

基于改进Kruskal-Wallis检验的低压开关电器状态表征参数选择

由于状态数据的多属性、高维度和大数据量,以及特征参数难以满足正态性和方差齐性检验的事实,低压开关电器的状态表征参数难于选择。针对该问题,基于非参数单体多状态样本的分组状态间秩差异性,以及特征参数Kruskal-Wallis(KW)检验统计量的计算规则和变化趋势,研究论证了单体样本特征参数表征显著性鉴别机理。同时,基于状态序列斜率变化增量和子序列变异增量,提出样本状态时序分类算法,并将该算法与参数鉴别机理相结合,形成单体多状态样本改进KW检验理论。最后,基于改进理论提出低压开关电器状态表征参数选择新方法。以交流接触器为例进行验证,结果表明该文方法适用于具有非线性、非平稳、动态随机分布等特点的低压开关电器状态表征参数选择。实例证明,基于该方法获得状态表征曲线的拟合优度可达0.91,状态划分显著性P值可达8.42848×10–266,表征与分类精度较参数选择前及同类方法提升明显,为下一步研究低压开关电器状态的精确划分与识别奠定了理论基础。

基于Switch-Capacitor网络实现分时供电的多输入升压变换器

在新能源联合发电系统中,多输入直流变换器可分时或同时向负载提供能量,具有简化系统结构、降低系统成本等优点。然而,现有的多输入直流变换器不能很好地满足新能源发电领域对高升压比、低纹波、低开关应力等技术参数的要求。因此,本文基于Switch-Capacitor网络串联放电、并联充电和多个网络累加升压的工作特性,推导出一种新型多输入升压变换器。本文以三输入升压变换器为例,详细分析了其在连续工作模式下的工作原理和工作性能,进行了仿真分析,并搭建了实验模型,仿真分析与实验研究的结果表明:①升压能力强,其升压比与Switch-Capacitor网络组中的网络个数有关;②开关器件的电压应力、输入电流纹波和输出电压纹波小;③所有开关管由同一控制信号隔离驱动,控制电路简单;④实现分时供电,元器件利用率高;⑤推演出对应的同时供电多输入升压变换器。

高压大功率开关器件电磁特性的解析模型

准确获得高压大功率开关器件的电磁特性对器件所在系统的电磁干扰预测十分重要。聚焦用于高压大功率开关器件电磁特性分析的开关波形等效方法,针对当前等效波形过于理想而无法体现器件开关瞬态中复杂频谱分量的问题,提出考虑器件开关过程电磁特性的解析模型。从解析模型的时域解析式出发,基于傅里叶变换理论,推导了解析模型的频域解析式,分析频谱包络特征参数,得到了解析模型的频谱特征。利用Si IGBT和SiC MOSFET器件实测的开关波形,验证了理论分析的正确性。

基于开通集射极电压下降平台的功率器件结温监测方法

准确的结温监测对功率器件可靠性评估和健康管理至关重要,因此在牵引变流器中广受欢迎。然而,传统的结温监测方法易受到负载电流变化的影响,导致监测精度不高,难以达到牵引变流器的可靠性需求。对此,该文提出一种基于开通集射极电压下降平台的功率器件结温监测方法,首先,基于功率器件的等效电路模型,对功率器件开通瞬态进行详细分析。在此基础上,对器件结温与开通集射极电压下降平台的关系进行探究,并提出一种基于杂散电感两端最大电压的开通集射极电压下降平台定位方法。进一步地,利用双脉冲实验对所研究结温监测方法的适用性进行分析验证;最后,搭建单相脉冲整流器实验平台,对所研究结温监测方法的可行性进行实验验证,该方法能够有效降低负载电流变化的影响且具有较高的灵敏度。

牵引级联变流器低次谐波分析与抑制策略优化

以级联H桥变流器为前级拓扑的电力电子变压器是未来列车牵引的重要发展方向,降低牵引级联变流器的低次谐波对提高电力电子变压器的控制性能具有重要意义。然而,引起级联H桥变流器低次谐波的影响因素与常规四象限变流器存在差异,其机理分析和抑制策略尚未得到深入研究。对此,文章详细探究了电力牵引网侧级联H桥变流器低次电流谐波产生机理,揭示了除直流电压波动、器件死区和管压降外,其低次谐波还与H桥级联的模块数及拓扑结构有关。在此基础上,设计一种兼顾直流电压波动和电路拓扑特性的低次谐波抑制算法。同时,结合功率器件的死区效应与管压降影响,提出级联H桥变流器低次电流谐波综合抑制策略。最后,搭建小功率试验平台进行测试,试验结果验证了理论分析的正确性和优化抑制方案的有效性。

低压开关柜中温升监测装置的应用分析

旨在研究低压开关柜的温升监测装置设计与应用,考虑到开关柜结构复杂、部件温度过高可能导致过热故障的问题。通过研究发现,温升在线监测装置能够有效感知开关柜内零部件温度变化,为控制温度提供有力支持。设计包括远红外测温技术、数据采集模块、上位机软件以及报警系统的综合应用,以全面监测开关柜区域。通过大数据和计算机技术分析温度变化数据,预防过热故障的发生,提高设备可靠性,延长寿命,对电力系统的稳定运行具有积极意义。

基于GaN的恒流型无线电能传输电路设计

为提升无线电能传输(WPT)系统的效率,利用氮化镓(GaN)器件比传统硅(Si)器件开关损耗低的优势,提出了基于GaN器件的LCL-LCC型感应耦合式电能传输(ICPT)系统与负载无关的恒流输出电路设计方法。首先对LCL-LCC补偿电路建立互感模型,推导出系统零相位角(ZPA)运行和与负载无关的恒流输出条件,提出了优化初级补偿电感的参数配置方法及设计流程。通过微调副边补偿电容值,逆变桥能实现零电压开关(ZVS)。最后,搭建实验平台验证理论电路设计的可行性。实验结果表明,对于不同负载,基于GaN器件的系统效率明显高于Si器件。

Evaluation of 1.2 kV SiC MOSFETs in Multilevel Cascaded H-bridge Three-phase Inverter for Medium-voltage Grid Applications

A study is conducted to evaluate 1.2 kV silicon-carbide(SiC)MOSFETs in a cascaded H-bridge(CHB)three-phase inverter for medium-voltage applications.The main purpose of this topology is to remove the need for a bulky 60 Hz transformer normally used to step up the output signal of a voltage source inverter to a medium-voltage level.Using SiC devices(1.2-6.5 kV SiC MOSFETs)which have a high breakdown voltage,enables the system to meet and withstand the medium-voltage stress using only a minimal number of cascaded modules.The SiC-based power electronics when used in the presented topology considerably reduce the complexity usually encountered when Si devices are used to meet the medium-voltage level and power scalability.Simulation and preliminary experimental results on a low-voltage prototype verifies the nine-level CHB topology presented in this study.

面向暂态电压主动支撑的多功能并网变流器多模式柔性切换策略

基于并网变流器的电能质量治理装置在谐波电流治理、无功补偿等方面的性能优越,且设备可靠性高,但在解决暂态电压波动问题方面的能力有待进一步提升。基于此,提出一种面向电压主动支撑的多功能并网变流器(MF-GCC)及其多模式柔性切换策略。电网电压正常时,MF-GCC工作于并联补偿模式,实现网侧单位功率因数运行。在电网电压波动时,MF-GCC工作于串联补偿模式,实现电压补偿功能,维持敏感负载侧电压恒定。此外,对MF-GCC的并联与串联补偿模式切换过程进行详细分析,设置了有源功率器件的最优切换时序。仿真与实验结果验证了所提拓扑与控制策略的有效性和可行性。

纺织设备控制装置弱电故障维修实践

探讨纺织设备控制装置弱电故障适宜的维修方式。根据纺织企业设备现状,将纺织设备控制装置分为调速类控制装置、可编程控制器、开关电源、集成电路板4种,概括了每种控制装置的故障特点,并通过№21C型络筒机、K44型细纱机等几个典型的维修实例进行了说明,对比了自主维修和托外维修的成本。认为:企业通过自主维修,可以获得明显的经济效益。

改进型准有源栅极控制电路研究与设计

高压大功率变换器中如何降低半导体开关器件的电压应力是关键技术问题,而开关器件直接串联是重要的解决方案之一。在开关器件直接串联的高压电路中,开关器件的动、静态均压特性是关键指标。准有源栅极控制QAGC(quasi-active gate control)电路是具有代表性的串联均压拓扑,其特点是通过一个外部驱动源实现串联器件的动态、静态电压应力均衡,与此同时,可用于多个开关器件直接串联控制。研究表明,当QAGC驱动串联器件多于2个时,均压网络为上层器件提供的驱动电荷不足,降低串联器件的均压效果,严重时可能导致上层器件无法开通。针对这一问题研究了一种改进型QAGC电路,该电路将QAGC与一个辅助直流源相结合,辅助直流源在上层器件开通时刻提供额外驱动电荷,可保证器件的动、静态均压特性。分析了改进型QAGC的工作原理及设计方法,采用LTspice进行仿真并搭建实验平台进行验证,仿真和实验结果验证了电路拓扑的正确性。

Modular Multilevel Converter with Thyristor DC-link Switch for Full-torque Variable-speed Drives

The modular multilevel converter(MMC)is a promising topology for medium-voltage drive applications due to its high-quality output waveforms,low device switching frequency and voltage rating.However,the large cell capacitor voltage ripple is a severe challenge faced by MMC at low motor speeds.Recently,a hybrid MMC(HMMC)topology is proven to be a competitive solution because of its lower cell capacitor voltage ripple and not demonstrating a common-mode voltage(CMV)problem compared with other methods.However,the DC-link switch with IGBT limits HMMC from being applied in highvoltage applications.This paper uses a thyristor instead of IGBT as the DC-link switch.To ensure the thyristor can be softly turned on and safely turned off,a new control scheme is proposed.When using this proposed scheme,HMMC can also tolerate the failure of the thyristor being turned-off without shutting down the system,effectively improving its reliability.The cell capacitor voltage ripple analysis is presented considering the effects of the thyristor switching process.In addition,a decoupled energy balancing control is utilized to suppress the fluctuation of the DC current.Experimental results obtained from a 380 V/7.5 kW downscaled prototype validate the effectiveness of starting up a motor from the standby mode to rated speed applying full-torque.

基于变压器有载调压开关的电动吊检装置分析及设计

针对变电站有载开关吊检检修现场作业的实际需求,设计了一种变压器有载调压开关的电动吊检装置。阐述了该装置的基本结构和工作原理,设计并实现了检修作业所需的基本功能,介绍了具体设计内容和技术特征。实践证明,该装置具有组装便利、操作灵活等特点,可提高检修人员工作效率,解决室内环境作业存在的问题。

单相控制型软开关逆变器的最小复位电流控制

基于电感电流临界导通模式(critical conduction mode,CRM)的控制型软开关技术可实现开关管零电压开通(zero voltage switching,ZVS),但传统恒定电流复位方法的反向电流大,开关管通态损耗高。文中以单相三电平中点箝位型(three-level neutral point clamped,3L-NPC)逆变器为研究对象,提出一种具有最小电感复位电流的控制方法。首先,分析开关管ZVS的实现条件,建立谐振等效电路分析模型,推导出电感复位电流理论最小值,在保证整个工频周期内开关管ZVS的同时,降低复位电流导致的开关管通态损耗。然后,建立逆变器损耗分析模型,将文中方法与传统恒定电流复位方法进行损耗计算与对比。最后,搭建一台1 kW的单相3L-NPC逆变器样机进行实验,结果表明文中方法相比于传统恒定电流复位方法,降低了损耗,最高变换效率提升约0.5个百分点。

基于网络技术的变电站电压无功自动控制系统

由于变电站的实际运行受多种因素的共同影响,导致电压无功控制尺度较难确定,影响最终的控制效果。为此,设计基于网络技术的变电站电压无功自动控制系统。考虑到网络技术中的实现对系统运行逻辑以及功能的构建,将具有快速数据传输效率的DSTREAM-HT仿真器作为系统的硬件,利用DSTREAM-HT仿真器追踪获取调压装置和投切电容器组的具体运行数据,并采用网络技术中的数值分析手段计算单位电压无功控制量作用强度,以DSTREAM-HT仿真器追踪到的变电站实际运行数据为基础,结合作用强度实现对变电站电压无功自动控制。测试结果表明,设计系统控制下,变电站二次侧无功电压始终稳定在5.50 kV以内,具有较高的稳定性和较好的控制效果。

探卡对功率器件导通压降测试的影响

功率半导体器件是各类电力电子装置的重要组成部分,对系统的效率、可靠性、功率密度等性能起着决定性作用。导通电阻作为器件最重要的参数之一,直接影响到该器件的使用。探卡是用于测试封装前芯片的一种精密的接触工装,探卡上探针的针尖分布和扎针位置对导通电阻测试有一定的影响,芯片面积和测试电流越大,对探卡测试的影响越大。基于以上分析,建立了探卡测试导通电阻模型。通过验证发现,在相同的探卡探针分布下,模型的精度大于96%;在不同的探卡探针分布下,模型的精度大于87%。