多任务机制在继电保护装置中的应用

提出了一种简单实用的基于多任务机制的继电保护装置的单片机系统程序结构。介绍了具体的实现方法 ,并给出了一个在变压器保护装置中的应用实例     

大型热网加热器的改型设计

大型热网加热器主要用于城市集中供热,设备在制造完工后,运至电厂安装。文章介绍某电厂热网加热器失效现象并对原因进行了分析,确定现场改型设计方案．制定了改造工艺,最终,在现场将大型U型管式热网加热器成功改造为固定管板式热网加热器。     

排沙漏斗悬板倾角优化试验研究

通过系列模型试验研究了溢流悬板近心端向下倾斜、向上倾斜和水平布置对排沙漏斗水沙分离性能的影响。结果表明,溢流悬板倾斜与水平布置时排沙漏斗的截除率基本一致。悬板向上和向下倾斜时漏斗室和悬板表面的泥沙淤积量均小于悬板水平布置时的淤积量,倾角越大,淤积量越小。当悬板近心端向上倾斜时,泥沙淤积量的减幅大于悬板向下倾斜工况,排沙耗水率低于向下倾斜和水平布置工况,且向上倾角越大排沙耗水率越低。因此,将悬板近心端向上倾斜一定角度可有效解决悬板表面泥沙淤积问题,而且可减少排沙耗水率和漏斗室内的淤积量,研究成果可为排沙漏斗的悬板优化设计提供依据和指导。     

Alleviation Technique for Thermal Concentration on Specific Switching Devices in Zero‐Speed Driving of PMSM

In this paper, a technique is proposed for alleviating the thermal concentration on specific switching devices by using a zero‐sequence voltage in a three‐level inverter that drives a permanent magnet synchronous motor (PMSM) in a zero‐speed and high‐torque condition. The use of the PMSM in home electronics and industrial products has become widespread, since it can realize miniaturization and a high efficiency drive. However, a large DC current flows when the PMSM is used in a zero‐speed and high‐torque condition, for example, in the hill‐start of electric vehicles, start or stop of elevators, or servo lock of servo pressing machines, and so on. In these cases, the current flows in the specific switching devices and heat generation is locally concentrated. This problem is unavoidable in a conventional two‐level inverter. A technique that can change the current path in a three‐level inverter and control the losses generated in the switching devices is proposed. We evaluated the effects of the proposed technique through a circuit simulation in which the electrical characteristics of a commercially available power device were applied. The proposed technique can reduce the highest loss of the switching devices in the three‐level inverter by about 40% as compared to that in a conventional inverter. Moreover, a method is proposed that suppresses the neutral point potential variation between the power supplies. This method can also reduce the maximum loss of the specific switching devices by about 30%.     

零残流消弧线圈综述

国内实现零残流有2种方法:第一种方法即在谐振接地系统接地相的滞后相接电容或超前相接电感,该方法需在电网一次侧施加能分相操作的开关及相应的电感及电容,同时该方法相当于人为造成了两相经过渡电阻接地的故障;第二种方法即有源注入的方案,该方法选出接地故障的线路,借鉴有源电力滤波的理念来实现零残流.而目前针对谐振接地系统,其选线...     

Teleoperation via computer network

In a teleoperation system, providing force information to a human operator can improve task performance. When a communication block between a master and a slave has a transmission delay, the system is easily destabilized. Anderson and Spong guaranteed passivity in the communication block by using scattering transformation and overcame this instability caused by the time delay. But this method can be applied to the communication block with a constant time delay. In a traditional teleoperation system, its communication block has a constant time delay. But time delay irregularly changes in a computer network because many users share telecommunication lines. This paper shows that the variable time delay destabilizes bilateral master-slave manipulator with scattering transformation and a new compensation method which keeps the time delay constant. This new compensation method has been implemented in a single-axis master-slave manipulator.     

Load following in a deregulated power system with Thyristor Controlled Series Compensator

Load following is considered to be an ancillary service in a deregulated power system. This paper investigates the effect of a Thyristor Controlled Series Compensator (TCSC) for load following in a deregulated two area interconnected thermal system with two GENCOs and two DISCOs in either areas. Optimal gain settings of the integral controllers in the control areas are obtained using Genetic Algorithm by minimizing a quadratic performance index. Simulation studies carried out in MATLAB validates that a Thyristor Controlled Series Compensator in series with tie-line can effectively improve the load following performance of the power system in a deregulated environment.     

Analysis of a zero-power flow phenomenon in an interconnecting power system

Today's power systems are characterized in that more power demand is concentrated in urban areas, increasingly centralized power facilities are becoming larger in size and located in more remote places, and power condensers tend to be upgraded to improve the power factor. These movements each reduce the stability power limit, thereby permitting the effect of a power failure to spread much farther. In such an interconnecting power system, when power is transmitted from a power source (a small system) in a remote place to a large city (a large system) with great power demand, it is expected that a zero-power flow phenomenon will occur where power transmission is impossible when power flow in the interconnecting power system is zero depending on a combination of the size of branch load and its power factor. In future power systems that will extend farther, have a larger capacity, and be more capacitive, such a phenomenon would be more iable to take place. In this paper, a new formula to analyze a zero-power flow phenomenon is derived, and using the formula, areas in which a zero-power flow phenomenon takes place also are discussed. With an experimental system simulating a practical 500-kV power system, the occurrence of a zero-power flow phenomenon could be verified.     

基于网络的继电保护整定计算和短路电流计算程序设计

为适应继电保护信息管理网络化的趋势 ,作者根据多年的继电保护整定和运行经验 ,编制了与继电保护整定和运行有关的一整套程序 ,且边开发边验证该套程序。文章介绍了一种继电保护整定计算和短路电流计算程序设计的新思路 ,它将和 DMIS网相结合 ,各程序之间是有机结合的 ,计算是基于网络的计算模式 ,编制过程中强调优化算法     

一种新型单相不对称五电平逆变器

该文对一种新型单相不对称五电平逆变器进行研究，这种新型逆变器是通过将半桥二极管钳位逆变器和传统两电平半桥逆变器共享同一直流母线而获得的。针对这种新型拓扑结构该文分析了一种方波合成与消谐波三角载波PWM相结合的控制方法，在这种控制方法下，新型逆变器允许开关速度较快的器件和耐压值较高的器件工作在一起。文中将这种逆变器与其它三种单相五电平逆变器进行了比较。最后本文对一个单相五电平不对称逆变器电路进行了实验验证，并给出相关结论。     

带串联补偿故障限流器的仿真和实验

采用短路电流限制器(FCL)快速限制短路电流是提高系统稳定性和断路器开断能力的有效方法之一。文中研究了一种具有串联补偿作用的FCL模型——由补偿电容和旁路电感并联后与限流电感串联而成。正常情况下，由电容和限流电感对线路进行串联补偿；发生故障时，根据短路电流的大小控制门极可关断晶闸管的导通角，改变投入的限流电抗，达到限流目的。用MATLAB对馈线短路的仿真及采用单片机控制方案的单相实验结果表明，该限流器限流效果良好。     

稳定器设计的就地相位补偿法在多机电力系统中的应用

为了演示和验证稳定器设计的就地相位补偿法在多机电力系统中的应用,介绍在多机电力系统中,就地补偿设计稳定器的2个应用实例。第1个实例是在多机电力系统中就地补偿设计电力系统稳定器(power system stabilizer,PSS),阻尼电力系统局部模振荡。第2个实例是就地补偿设计附加在静态同步补偿器(static synchronous compensator,STATCOM)上的稳定器,抑制多机电力系统中的区域模振荡,并给出在一个16机电力系统中的应用计算和仿真结果。     

Estimation of a preference map of new consumers for spatial load forecasting simulation methods using a spatial analysis of points

The paper presents a spatial analysis of points especially suited to estimate a preference map for new consumers, which is then used as an analytical tool in spatial electric load forecasting. This approach is an exploratory spatial data analysis used to discover useful point patterns in the spatial location of distribution transformers to calculate a preference value for each area, rating it with respect to a hypothetical load change that may occur. We consider the locations of distribution transformers occupied land. Random points are generated in the study area where the new loads are expected; these points are referred to as unoccupied land. The method uses a generalized additive model (GAM) to estimate the probability of unoccupied land becoming occupied land. We test the approach with data from a real distribution system in a mid-size city in Brazil; the result is a preference map that shows the areas where new consumers are most likely to be allocated. The main advantage of this method is the ability work with a small-scale resolution, which enables the use of a resolution suitable for spatial load forecasting method chosen. We test the calculated probabilities in a spatial load forecasting simulation, yielding results with lower spatial error when compared with the heuristic technique.     

Efficient and reliable fault analysis methodology for nanomagnetic circuits

The increasing issues in scaled Complementary Metal Oxide Semiconductor (CMOS) circuit fabrication favor the flourishing of emerging technologies. Because of their limited sizes, both CMOS and emerging technologies are particularly sensitive to defects that arise during the fabrication process. Their impact is not easy to analyze in order to take the necessary countermeasures, especially in the case of circuits of realistic complexity based on emerging technologies. In this work, we propose a new methodology supported by an efficient and reliable tool for the identification of the impact of faults in complex circuits implemented using the emerging technology we are focusing on in this case: nanomagnetic logic. The methodology is based on three main steps: (i) we performed exhaustive physical‐level simulations of basic blocks based on a detailed finite‐element tool in order to have a full characterization, to know their properties in presence of defects, and to have a solid reference point for the following steps; (ii) we developed a model (fanomag ) for the basic block behavior suitable for simulations in presence of defects of complex circuits, that is, lighter than a physical level one, but accurate enough to capture the most important features to be inherited at circuit level; (iii) starting from a physical design of complex circuits that we perform using a specific design tool we developed, that is, ToPoliNano , we simulated using fanomag , now embedded in our ToPoliNano tool, the behavior of circuits in presence of multiple sets of fabrication defects using a Monte Carlo approach now included in ToPoliNano as a new feature. In this paper, a specific type of defect is considered as a case study. The framework and methodology are conceived to be easily extended to handle other types of defects and problems due to working conditions that a designer and/or a technologist might want to focus on. The major outcome is then a powerful methodology and tool capable to analyze with a good accuracy nanomagnetic logic complex circuits and architectures both in ideal conditions and in presence of defects with remarkable performance in terms of simulation times. Copyright © 2016 John Wiley & Sons, Ltd.     

雨水口泄流计算对城市洪涝模拟结果影响研究

雨水口可将地表径流输送至排水管网,是城市洪涝治理中的关键因素。为充分掌握雨水口泄流机理,本文总结了泄流试验研究的主要成果,比较了不同泄流计算方法的优缺点及适用范围;通过编译生成SWMM动态链接库文件（DLL）,构建了改进泄流计算的城市雨洪模型;以西安市沣西新城为研究对象,定量分析了不同泄流计算方法对汇水区内雨水口泄流量及洼地积水深度的影响。结果表明：典型汇水区内采用不同泄流计算方法模拟得到的泄流量占降雨总量的38% ~ 48%;泄流公式中流量系数18%的差异会在洼地积水深度结果中放大至55%;研究区各汇水区内因雨水口泄流能力不足而导致的最大洼地积水深度在0.1 ~ 0.6 m之间。研究成果有助于深化对雨水口泄流过程的认识,为城市防洪减灾提供技术支持。     

在输电线和变电站组合联结网络中的非同调现象

非同调现象指的是:一个元件从系统中缺省反而产生一个更可靠的系统状态,或者甚至提供更高的系统可靠性水平。这个现象可能存在于输电系统中,但却没有得到电力工业界的充分认知。文中解释了输电系统可能存在非同调的概念,并提出一个输电线和变电站组合联结网络的实例。在该实例中,一个双回线并行结构通过分支点T接引入变电站,与一个单回线结构通过分段接入变电站相比,不仅多需要一条线路,而且可靠性也差。这与规划工程师通常的直觉判断相反。虽然这是加拿大某电力公司的例子,但却有一定普遍意义,因为许多电力公司大量采用类似的两端向中间负荷供电并通过分支点T接引入变电站的双回线并行结构。如果能够通过定量可靠性评估识别一个实际输电系统的非同调特性,就有可能避免多余的输电元件,从而既能节省投资又能改进系统可靠性。     

An Energy-efficient Switching Scheme with Reduced Switching Transients for a Wind-driven Induction Generator

This article presents a scheme for improving the power output of grid-connected induction generator commonly used in wind energy conversion systems. Generally, the stator of the induction generator is connected in a star with a line voltage of √3 times the rated winding voltage to reduce the line current and, hence, conductor size. To extend the generating operation over a wider speed range, delta-star switchable stator windings are also in vogue. In such cases, the stator is star connected in the lower speed range and switched to a delta connection above a threshold speed. In this study, a new switching scheme is proposed wherein the stator coils are always connected in a star, while the stator is connected to different voltages in low- and high-speed conditions. At low wind speeds, nominal winding voltage is applied to the stator, whereas at higher speeds, the stator applied voltage is √3 times higher than the rated winding voltage. The efficacy of the scheme is demonstrated experimentally with a suitable microcontroller-based switching arrangement. Typical results indicate an increase in output with reduced switching transients. A case study on a 3-Φ, 50-kW induction generator is presented to emphasize the performance improvement with the proposed scheme.     

基于IEC 61850的光伏监控系统设计

为了解决光伏发电系统中设备的互操作问题。设计了基于IEC61850标准的光伏监控系统。应用IEC61850信息建模方法,给出了光伏发电系统的逻辑设备及其包含的主要逻辑节点,并详细阐述其作用。通过光伏单元设备中逻辑节点在一次接线图中的分布展示了基于lEC61850标准的光伏监控系统的功能组成,并进一步给出基于IEC61850标准光伏监控软件的体系结构和功能。文章方案可为开发具有互操作性的光伏监控系统提供参考。     

局部放电脉冲在XLPE电缆交叉互联系统中传播特性探讨

局部放电脉冲在含有交叉互联系统上的传播有其一定的规律。通过在一个真实的交叉互联系统上的试验,在一相上加电压,激发出精确预制在电缆附件中缺陷的局部放电,采用差分法和宽频带脉冲检测器等方法对在系统内设计好各测点的局放脉冲进行检测并对此放电脉冲在不同频带下传播的特性进行分析,得出局放脉冲在交叉互联系统中传播的规律和特点,并提出如何利用这些规律和特点进行电缆局部放电的在线实测。     

水电站引水发电系统小波动Ⅰ区失稳机理研究

本文基于小波动稳定分析理论,建立了水电站引水发电系统数学模型,研究了无调压室及含调压室水电站引水发电系统在调速器参数Ⅰ区失稳现象,理论分析了系统各子环节相频特性对系统稳定性的影响。结果表明：水电站引水发电系统在调速器参数Ⅰ区失稳的根本原因在于压力管道内水流存在惯性,造成压力管道流量变化相较于导叶开度变化存在相位滞后,从而在调节过程中产生调节误差,并逐渐放大。调速器积分调节环节会使得导叶开度变化相对机组转速变化产生相位滞后从而恶化系统稳定性,比例调节增益 会改变调节系统中积分环节以及压力管道惯性环节叠加后总的相位滞后, 较小时系统总相位滞后随 的增大而减小; 较大时系统总的相位滞后随 的增大而增大,当相位滞后超过90°时,将导致闭环系统失稳。