断路器操动机构振动信号的分析

以CT1型弹簧操动机构为研究对象,通过实验研究得出利用振动信号来区分不同振动事件的方法,并分析了振动信号出现时间与操动机构机械状态的关系。     

多端口能量互补设备多工况协调控制

多端口能量互补设备在多工况下的稳定运行以及工况间的平滑切换是保证电网平滑运行的重要支撑。针对设备内分布式发电的波动性,基于分层控制策略,文中先提出了一种并离网模式下多工况划分方法,通过本地控制层与中央管理层两层间端口参数和控制指令的协调配合来维持设备在所提多个工况下的功率平衡。其次,又提出了一种改进的并离网平滑切换方法,并在此基础上加入电压监测来避免电压正常波动所引起的工况频繁切换。最后,在MATLAB中搭建3种典型运行场景的仿真模型以验证其可行性。仿真结果表明,直流母线电压在典型场景的工况切换过程中能够迅速恢复到稳定状态,且波动在0.5%以内;同时改进的并离网平滑切换方法能够在30 ms内实现预同步,能够满足稳定、快速的运行要求。     

双馈抽水蓄能机组用中点箝位式三电平变流器损耗与结温分布

针对双馈抽水蓄能机组(DFPSU)运行工况转换频繁,分析不同运行工况下中点箝位式(NPC)三电平变流器功率器件损耗及结温分布。基于DFPSU运行特点,以机侧变流器单相桥臂功率模块为例,研究了不同运行工况下各个功率器件开关动作和电流通路,理论上分析了器件损耗分布不均现象;基于功率器件导通损耗和开关损耗计算模型,建立其热网络等效电路和结温计算模型,考虑DFPSU控制策略,并基于PLECS平台建立了NPC三电平变流器功率器件电热耦合仿真模型;对机组在发电、电动和调相运行工况下的器件损耗和结温分布进行仿真。理论分析与仿真结果表明,不同运行工况下器件损耗不同,变流器中间位置的主开关和箝位二极管的损耗和平均结温最大,且机组在同步转速点附近器件结温波动最大。     

串联混合型有源滤波器的建模及控制策略分析

通过建立通用电路模型,从理论上对目前提出的几种典型的串联混合型有源滤波器的结构和滤波原理进行了研究,对各种控制策略的优缺点和系统的稳定性进行了分析,并在此基础上研究了不同谐波条件下各种控制策略的滤波效果,其结论为串联混合型有源滤波器在不同工况下控制策略的选择提供了参考依据.     

Temperature Effects on a Non-Volatile Memory Device with Ferroelectric Capacitor

The temperature effects on a ferroelectric non-volatile memory latch were measured. The device is based on a design from Radiant Technologies Inc. utilizing a discrete ferroelectric capacitor. The effects measured include functionality, I-V characteristics and retention. The range of temperatures for which the device was tested is –107°F to +302°F. The results are compared with measurements made at room temperature for the device. Retention measurements of the device at elevated temperatures allow predictions of retention performance under normal operating conditions. Potential applications of this device in harsh environments which include aerospace, industrial and automotive are presented.     

A Regional Approach for Computer-Aided Transistor Design

A regional approach to transistor design is presented which makes possible the determination of transistor gain hFE for any transistor (doping profile specified) operating at any given values of emitter current IE and collector-to-emitter voltage VCE. This approach extends the classical diffusion theory of transistors to include conductivity modulation, voltage-controlled base motion, and current-controlled base motion (base widening). Due to the simplicity of this technique, time-sharing computer techniques were used. This allowed for user interaction, making this approach very attractive for education as well as design. The regional approach is a likely candidate for satisfying the needs for the device designer (it contains device performance versus doping profile), the circuit designer (it allows determination of equivalent circuit models from knowledge of the electron and hole densities throughout the device), and the academic world (it is simple and physical). It is anticipated that the regional approach will allow engineers to develop a "feel" for transistor behavior under wide ranges of operating conditions.     

功率变流器的可靠性研究现状及展望

可再生能源并网发电技术的迅速发展,对功率变流装置的可靠性提出了更高要求。工业界的调查表明,可再生能源发电系统的故障很大一部分原因可归咎于变流装置的故障,而功率器件的失效是主要诱因。研究功率器件可靠性是提高变流器可靠性的基础,对延长设备的使用寿命具有重要意义。围绕功率变流器的可靠性问题,从变流器的工作特点出发分析了导致其可靠性不高的主要原因。首先阐述了功率器件在工作中的主要失效机理;为防止损坏设备的故障发生,需要实时监测变流器的健康状态及评估装置的可靠性,文章总结了功率器件的状态监测方法及寿命预测技术;为提高变流器的运行可靠性,提出了变流器状态控制的概念,对各种状态控制方法进行了分类介绍,并分析总结了现有状态监测方法、寿命预测模型及状态控制方法的优缺点,最后根据这些优缺点对功率变流器可靠性研究进行了展望。     

An improved nonlinear thermal model for MV/LV prefabricated oil-immersed power transformer substations

The largest part of the investments of transmission and distribution systems is due to transformers used in changing the voltage level. The operating life of transformers is important due to their considerable economic impact on the power systems. To ensure the economical operation and secured service it is important to have knowledge about the insulation condition, operating life, and loading capacitance of transformer. The most important parameter in transformers life expectancy is the insulation temperature level, which accelerates the rate of aging of the insulation. The modeling of the energy balance and heat transfer of transformer is a major task in transformers thermal modeling. The aim of this paper is to present improved thermal models for transformers loaded at prefabricated MV/LV transformer substations and outdoor situations. The top-oil temperature is studied both for indoor and outdoor transformers and the thermal models proposed for them are compared. Since the thermal transfer is different for indoor and outdoor transformers considering their operating conditions, their thermal models differ from each other. The proposed thermal models are verified by the results obtained from the experiments carried out on typical indoor 30 kV/0.4 kV transformer stations at different operating conditions.     

High-speed non-linear circuit models for p-n junction diodes

Circuit models for both long-base and short-base p-n junction diodes which are valid for non-linear high-speed and high-frequency operations are presented. the diode model consists of a parallel connection of higher-order dynamic elements and includes the conventional diffusion model as a special case. the new dynamic model can be used for simulating arbitrary p-n junction diode circuits under all operating conditions. In particular, it is capable of simulating realistically the diode's reverse transient behaviour and providing an increasingly accurate approximation to the diffusion equation as the order of the model gets higher. the model is also shown to be capable of reproducing the frequency-dependent small-signal characteristics of p-n junction diodes. The model is based mainly upon the device's physical operating principles. Perhaps the most significant implication of the model is the fact that it illustrates the important roles played by higher-order and dynamic elements in highspeed and high-frequency non-linear device modelling.     

汽轮发电机绝缘过热监测装置运行状况及改进意见

分析了目前在我国大容量汽轮发电机上使用的绝缘过热监测装置的运行状况，指出了存在的问题并提出了改进措施，可供设计，制造及电厂运行人员参考。     

电动汽车蓄电池组管理系统及其状态检测

电动汽车蓄电池组的工作状态主要指各电池在工作时的端电压、工作电流和温度这3个参数的变化情况。对电池工作状态的检测通常有集中式检测法和分布式检测法。本文采用”部分”集中、”整体”分布的思路,将电池分成若干分组,每个分组集中检测,各分组分布检测,同时,采用“桥电容”技术解决了蓄电池组单体端电压检测中存在的参考点选择和被测电池与检测设备隔离的问题,形成了一种具有完全隔离功能的集中／分布式检测法。经过试验,该检测法对电压、电流和温度采集功能正常,数据准确、可靠。     

Three-dimensional simulation for negative resistance characteristics of parasitic bipolar transistor in a small-sized mosfet structure

The behaviours of parasitic bipolar transistors are investigated by exploring the physical mechanisms of negative resistance characteristics generated in a small-sized MOSFET structure. Physical experiments and three-dimensional simulations verify the expected negative resistance characteristics. The effects of variations of device parameters such as injected substrate current levels, doping concentrations, channel widths, and physical device sizes are investigated by simulation. According to simulation results, the operation of a parasitic bipolar transistor is initiated by the injected substrate current; this explains the negative resistance characteristics occurring at low operating voltages.     

变压器气体继电器故障分析与改进措施

通过对辽宁省电网近15年来气体继电器非正常动作的统计分析,就气体继电器因使用不当或制造缺陷原因,引起的重瓦斯保护动作,轻瓦斯保护频繁动作等情况进行了分析,并为正确使用变压器瓦斯保护装置提出了改进建议。     

Development of combined low-emissions burner devices for low-power boilers

Low-power water boilers are widely used for autonomous heat supply in various industries. Firetube and water-tube boilers of domestic and foreign manufacturers are widely represented on the Russian market. However, even Russian boilers are supplied with licensed foreign burner devices, which reduce their competitiveness and complicate operating conditions. A task of developing efficient domestic low-emissions burner devices for low-power boilers is quite acute. A characteristic property of ignition and fuel combustion in such boilers is their flowing in constrained conditions due to small dimensions of combustion chambers and flame tubes. These processes differ significantly from those in open combustion chambers of high-duty power boilers, and they have not been sufficiently studied yet. The goals of this paper are studying the processes of ignition and combustion of gaseous and liquid fuels, heat and mass transfer and NO _x emissions in constrained conditions, and the development of a modern combined low-emissions 2.2 MW burner device that provides efficient fuel combustion. A burner device computer model is developed and numerical studies of its operation on different types of fuel in a working load range from 40 to 100% of the nominal are carried out. The main features of ignition and combustion of gaseous and liquid fuels in constrained conditions of the flame tube at nominal and decreased loads are determined, which differ fundamentally from the similar processes in steam boiler furnaces. The influence of the burner devices design and operating conditions on the fuel underburning and NO _x formation is determined. Based on the results of the design studies, a design of the new combined low-emissions burner device is proposed, which has several advantages over the prototype.     

ANALYSIS OF SELF-EXCITED INDUCTION GENERATORS UNDER UNBALANCED CONDITIONS

ABSTRACT

This paper presents general mathematical models for various generator-load configurations that accurately determine the conditions for self-excitation and performance characteristics of an isolated, three-phase, self excited induction generator operating under balanced or unbalanced excitation and/or load conditions. The models are derived using symmetrical components theory along with the generator sequence equivalent circuits. The theoretical predictions obtained from the proposed models have been verified experimentally for several balanced and unbalanced configurations.     

基于多种信号风力发电机在线故障检测装置设计*

风力发电机在线检测系统可以实时了解风力发电机运行工况及时发现故障隐患。针对检测数据种类过少导致风力发电机故障诊断出现误判问题,文中设计了一种多通道数据采集实时在线故障检测装置。以DSP TMS320F28335(简称F28335)作为系统主控芯片采集现场数据,Lab VIEW软件系统和MCGS组态软件进行同步显示。通过模拟实验表明,与传统的风力发电机在线检测装置相比,能更全面的采集多种运行工况下的数据,为故障诊断提供可靠依据。     

A busbar protection technique and its performance during CTsaturation and CT ratio-mismatch

This paper describes a digital technique for protecting busbars. The technique uses positive- and negative-sequence models of the power system in a fault-detection algorithm. While phase voltages and currents are used to detect faults, parameters of the power system are not used. An analysis of the performance of the proposed technique during CT saturation and ratio-mismatch conditions is presented. The performance of the technique was investigated for a variety of operating conditions and for several busbar configurations. Data generated by EMTP simulations of model power systems were used in the investigations. The results indicate that the proposed technique is stable during CT saturation and ratio-mismatch conditions     

直流系统绝缘监测装置的软件设计

直流系统绝缘监测装置对电力系统的安全稳定运行起着十分重要的作用.通过对直流系统绝缘监测原理优缺点的分析,首先提出一种平衡桥电阻法与开关电阻法相结合对母线监测的硬件设计方案,然后针对直流系统绝缘监测装置在工作时需要处理较大数据,采用STM32F103VET6作为主控制器,移植μC/OS-Ⅱ操作系统提高装置的实时响应能力,并详细介绍基于μC/OS-Ⅱ操作系统软件任务的工作流程.通过制作样机进行相关实验,经验证该设计可以切实有效的解决系统处理实时性不高等问题,并在多种接地状态都具有较高的测量精度.     

Modelling of V–Hz and vector controlled ASDs in PSCAD/EMTDC for voltage sag studies

This paper deals with modelling and performance of adjustable speed drives (ASDs) subjected to voltage disturbances in electric supply. The aim of this study was to develop appropriate models of typical ASD and investigate their sensitivity to voltage disturbances under various practical modes of operation and control. Accordingly, scalar controlled open and closed loop volts–hertz (V–Hz) and vector controlled closed loop ASDs are modelled in PSCAD/EMTDC environment, and their performance in the presence of voltage disturbances is investigated under typical operating and loading conditions.     

InGaAsP–InP Avalanche Photodiodes for Single Photon Detection

In this paper, we describe the design, characterization, and modeling of InGaAsP/InP avalanche diodes designed for single photon detection at wavelengths of 1.55 and 1.06 mum. Through experimental and theoretical work, we investigate critical performance parameters of these single photon avalanche diodes (SPADs), including dark count rate (DCR), photon detection efficiency (PDE), and afterpulsing. The models developed for the simulation of device performance provide good agreement with experimental results for all parameters studied. For 1.55-mum SPADs, we report the relationship between DCR and PDE for gated mode operation under a variety of operating conditions. We also describe in detail the dependence of afterpulsing effects on numerous operating conditions, and in particular, we demonstrate and explain a universal functional form that describes the dependence of DCR on hold-off time at any temperature. For 1.06-mum SPADs, we present the experimentally determined relationship between DCR and detection efficiency for free-running operation, as well as simulations complementing the experimental data.