基于HHT变换的微网电压闪变与谐波检测新技术

微网中大规模的分布式电源由于其自身特点及大量电力电子设备的使用,容易引起电网电压波动、电压闪变及谐波等电能质量问题,影响电力用户的供电要求。利用HHT(Hilbert-Huang transform)变换方法对微网中的电压闪变、谐波等电能质量扰动信号进行了EMD分解,得到各IMF分量,通过对IMF分量进行Hilbert谱分析和边际谱分析。仿真结果表明,该方法能快速有效地检测出微网中电压闪变信号的频率和幅值及谐波信号产生及终止的时刻。     

配电网电压暂降检测算法的仿真比较

在分析有效值算法、瞬时dq变换法和αβ变换法3种电压暂降检测算法基本原理的基础上,应用Matlab/Simulink软件仿真平台,建立了配电网电压暂降的检测模型。针对电压暂降时有无相位跳变以及配电网含谐波源等情况,对3种检测算法的检测性能进行了仿真比较。仿真结果表明:3种检测算法都能检测电压暂降后基波有效值的大小。其中,αβ变换法具有检测响应速度快,检测精度高等特点,而瞬时dq变换法则具有更好的配电网谐波抗干扰能力。     

考虑补偿方法的单相DVR检测方法研究与仿真

定量分析计算电网电压暂降时DVR逆变单元与电网的功率交换情况,详细研究逆变单元在各种补偿策略下的输出电压和有功功率与故障前后电网电压、负载电压和参考相量的具体关系,并根据具体关系总结出5种补偿方法,通过Matlab平台对各种补偿方法进行仿真研究,最后根据不同的补偿方式进行单相DVR检测方法研究。     

高压线路防外力破坏激光监测预警系统的研究

针对当前我国高压电力线路防外力破坏面临的严峻形势,设计出一种基于激光监测技术的输电线路防外力破坏监测预警系统,利用激光监测高压线路可能将要发生的外力破坏隐患,提前实现预报警和现场对讲警示阻止外力破坏的发生。该系统能够自动计算外物体接近高压线的位置距离,根据不同电压等级线路设定的安全距离参数来确定其危险程度,实现分档报警。通过实际应用论证了系统的正确性和可行性,对高压线路防外力破坏有着重要的指导意义。     

Cell voltage monitoring All-in-One. A new low cost solution to perform degradation analysis on air-cooled polymer electrolyte fuel cells

In this work, a new low-cost and high-performance system for cells voltage monitoring and degradation studies in air-cooled polymer electrolyte fuel cells has been designed, built and validated in the laboratory under experimental conditions.This system allows monitoring in real time the cells’ voltages, the stack current and temperature in fuel cells made of up to 100 cells. The developed system consists of an acquisition system, which complies with all the recommendations and features necessary to perform degradation tests. It is a scalable configuration with a low number of components and great simplicity. Additionally, the cell voltage monitoring (CVM) system offers high rate of accuracy and high reliability and low cost in comparison with other commercial systems.In the same way, looking for an "All-in-One" solution, the acquisition hardware is accompanied by a software tool based on the "plug and play" philosophy. It allows in a simple way obtaining information from the cells and performing a degradation analysis based on the study of the polarisation curve. The different options and tools included in the CVM system permit, in a very intuitive and graphical way, detecting and quantifying the cell degradation without the need of isolating the stack from the system.Experimental tests carried out on the system validate its performance and show the great applicability of the system in cases where cell faults detection and degradation analysis are required.     

基于S-V特性分析的晶硅光伏组件阴影遮障诊断

针对广泛使用的晶硅光伏组件,通过Simulink建立太阳电池双二极管精确仿真模型,对实际应用中最常见的光伏组件阴影遮挡故障进行多种工况的仿真验证。根据I-V曲线拐点、台阶、曲线下积分面积（S）下降的特征,提出一种基于S-V曲线特性的光伏组件阴影遮挡故障的在线诊断方法。该方法建立S-V曲线,根据S-V曲线分叉点位置可判断光伏组件遮挡情况,通过整体积分面积进而判断遮挡比例。对温度、辐照度进行折算,使该方法在全工况下适用。结合光伏组件功率优化器验证该诊断方法有较高的准确率,并且可准确地判断阴影遮挡面积,具有很高的实际应用价值。     

炼钢电弧炉的运行特性与电压闪变抑制

对炼钢电弧炉电压波动与电压闪变这一主要干扰进行了定性分析,详细地介绍了几种抑制方法,指出SVC是现阶段抑制其不利影响的实际应用最广、最有效和最经济的措施之一。还对配电用静止补偿器与有源滤波器作了概述,以形成一个对电弧炉电压闪变等干扰进行综合补偿的完整概念。     

线路电压互感器引起的母线电压不平衡分析

变电站35 kV配电系统一般为中性点非直接接地系统,运行中存在着电压不平衡问题。从电压互感器产生的电力系统电压不平衡的几种原因出发,结合具体35 kV线路的特点,重点介绍了在现场运行过程中线路电压互感器所引起的母线电压不平衡现象及其原因,并结合实际情况进行了计算分析。最后针对分析结果给出了改进措施。     

一种节电的大功率自动稳压装置

针对电力系统供电电压一般高于负载额定电压的实际情况,采用电磁平衡技术和PLC控制技术,设计了一种降压的自动稳压装置。介绍自动稳压装置的构成和节电原理,通过结构设计和器材选择,使得自动稳压装置的自身损耗极小,具有明显的节电效果。     

Novel dynamic semiempirical proton exchange membrane fuel cell model incorporating component voltages

This paper introduces a novel dynamic semiempirical model for the proton exchange membrane fuel cell (PEMFC). The proposed model not only considers the stack output voltage but also provides valid waveforms of component voltages, such as the no‐load, activation, ohmic, and concentration voltages of the PEMFC stack system. Experiments under no‐load, ramping load, and dynamic load conditions are performed to obtain various voltage components. According to experimental results, model parameters are optimised using the lightning search algorithm by providing valid theoretical ranges of parameters to the lightning search algorithm code. In addition, the correlation between the vapour and water pressures of the PEMFC is obtained to model the component voltages. Finally, all component voltages and the stack output voltage are validated by using the experimental/theoretical waveforms mentioned in previous research. The proposed model is also compared with a recently developed semiempirical model of PEMFC through particle swarm optimisation. The proposed dynamic model may be used in future in‐depth studies on PEMFC behaviour and in dynamic applications for health monitoring and fault diagnosis.     

微电网系统接地方式及安全分析

微电网并网及孤岛模式运行必须满足电力系统安全运行的基本要求,合理的微电网系统接地方式及变压器接地网的设计是微电网安全稳定运行的重要保障,分析了微电网系统接地方式,采用接地分析软件CDEGS计算了微电网联网和孤岛模式运行时,不同位置故障时故障电流的分配情况,设计了微电网变压器的接地网,并仿真计算出接触电压和跨步电压的值,验证了所设计接地网的正确性,保证了微电网的安全运行。     

A semiempirical dynamic model of reversible open circuit voltage drop in a PEM fuel cell

Fuel cell voltage modeling is important for fundamental research. The main focus of previous studies has been the working voltage segment, whereas the accuracy of the open circuit voltage (OCV), especially the dynamic OCV change process, has been ignored. A semiempirical model including the OCV and an electrochemical model has been proposed in this study to clarify the reversible voltage drop process. A mixed cathode potential drop that is assumed as corresponding to a piecewise function relationship with an active surface area is introduced in this study. Fitting results exactly coincide with the original data in 2 modes, namely a quasistatic condition in a bench test and a dynamic condition in a fuel cell city bus. In the dynamic OCV drop process, the voltage drop due to the hydrogen crossover current approximately corresponds to 0.003 V and the mixed cathode potential drop approximately corresponds to 0.02 V.     

一种新型的风电场低电压穿越时撬棒电路设计与阻值选定

针对传统撬棒电路（Crowbar）在风电场低电压穿越时给电网带来无功负担问题,提出了一种新型的Crowbar保护电路,介绍了新型Crowbar的设计与阻值选定,并在PSCAD环境下搭建双馈式感应发电机（DFIG）模型,分析比较了无Crowbar保护电路、带有传统Crowbar保护电路和新型Crowbar保护电路时DFIG在电网电压跌落情况下的动态特性。结果表明,新型的Crowbar在有效保护风电场的同时减少了电网的无功负担,有效地弥补了传统Crowbar带来的电网无功负担。     

考虑暂态电压稳定性的电力系统多目标无功备用优化

鉴于目前电力系统无功备用优化方法较少涉及暂态电压稳定性,提出一种同时提高电力系统静态/暂态电压稳定性的无功备用优化模型,该模型首先基于数据密度提出一种无功电压控制分区方法,分别在静态/暂态电压的薄弱区域内定义静态/暂态无功备用,然后结合所建立的两个目标建立多目标无功备用优化模型,最后提出一种基于多阶段的多目标优化求解方法。通过求解所建模型,获得能够同时提升系统静态/暂态电压稳定性的无功备用配置方案。对IEEE 39节点系统的仿真分析证明了所提方法的有效性。     

GIS配套用电压互感器研究

采用数值模拟的方式对GIS配套用压互感器进行了研究,通过分析得到器身电场最大值为21．649kV／mm,设计裕度为3．42861kWmm,满足设计要求。试验工装电场计算的最大值为21．055kWmm,设计裕度为4．02276kV／mm,满足设计要求。     

青铜峡水电厂110kV系统电压运行分析

通过对１９９８ 年度青铜峡水电厂１１０ ｋＶ 系统电压运行状况的调查分析,归纳出影响系统电压正常运行的原因,并对其影响因素进行了剖析,进而提出了相应的措施。     

Analysis of proton exchange membrane fuel cells voltage drops for different operating parameters

Fuel cells are devices that convert hydrogen into electric power using electrochemical reactions. It is an essential to understand the underlying dynamic behaviour of proton exchange membrane (PEM) fuel cells and optimize their performance. In this paper, the analysis of activation, ohmic and mass transport voltage drop is viewed. Different operating parameters such as the exchange current density, the transfer coefficient, electrolyte thickness, cell useful area and temperature effect on the voltage-current density curve are simulated. The results show that the voltage drops decrease the voltage and efficiency of the cell. Activation voltage drop reduces the voltage of about 0.2 V, ohmic voltage drop up to 0.8 V and mass transport to nearly to 1 V in high current densities. In addition, high pressures of hydrogen, oxygen and water lead to an increasing of the cell output power. Moreover, the temperature affects the performance of the cell that is reduced in low operating temperature conditions.     

恒速风电机组对电网暂态电压稳定性的影响

基于恒速风电机组的结构,给出风电机组各部分的数学模型,利用仿真软件DIgSILENT/PowerFactory建立恒速风电机组的动态模型,并利用该模型在WSCC 3机9节点算例中仿真恒速风电机组并网运行时因风速变化引起的电网电压波动,通过极限切除时间分析恒速风电机组并网对电网暂态电压稳定性的影响,并与接入相同容量的同步机组进行比较。结果表明,恒速风电机组的接入降低了电网的暂态电压稳定性,且接入恒速风电机组装机容量越大,电网的暂态电压稳定性越差。由此提出改善恒速风电机组并网后电网暂态电压稳定性的建议。     

含有动态无功补偿器的供电系统自动电压控制设计

在介绍自动电压控制(AVC)系统设计背景的基础上,叙述了AVC系统的结构与配置、算法与流程、关键技术与应用优势,凸显了数据采集与监控、实时控制与快速补偿、人机联系与优化调节、历史数据管理等多项新技术的整合应用。试运行表明,供电系统AVC采用一级加二级控制方式运行,保证了AVC系统的先进性和补偿功能的稳定可靠;在地区调度和终端,通过数据采集与监控装置对地调进行全面的无功电压快速调节;利用动态无功补偿器的基于直流侧电容电压控制和系统无功电流反馈控制,可以可靠、灵活地提高无功电压的控制能力。     

太阳能发电低电压穿越技术综述

近几年来伴随着光伏设备装机容量的扩大,太阳能发电供电比重越来越大,当电网发生故障或电压暂降时,光伏阵列可能解列给电网带来不稳定,甚至造成电网的全面瘫痪,综述了3种光伏逆变器低电压穿越的解决方案和控制策略,重点分析了基于控制无功电流实现电压支撑的解决方案。