汽轮发电机转子的支承动刚度与临界转速问题

在用实测到的支承动刚度计算大型汽轮发电机转子的临界转速中，会出现一些反常现象，进行现场实测时也发现有类似情形，本文分析产生这一现象的根本原因，指出了实测支承动刚度的重要性和必要性。     

考虑量测相关性的容积卡尔曼滤波动态状态估计

针对电力系统动态状态估计中SCADA量测量间存在相关性的实际情况,文中提出了一种考虑量测相关性的容积卡尔曼滤波动态状态估计方法。首先进行了SCADA量测相关性分析,然后基于状态转移方程推导过程噪声协方差矩阵,基于容积变换方法计算考虑SCADA量测相关性的量测误差协方差矩阵,并提出了考虑量测相关性的电力系统动态状态估计流程,每次估计实时修正量测误差协方差矩阵及过程噪声协方差矩阵。IEEE-39节点系统的仿真结果表明,相较于不考虑量测相关性的容积卡尔曼滤波算法,文中方法能够明显提高状态估计结果的精度。     

Optimal meter placement for maintaining observability during singlebranch outages

This paper presents a method for designing measurement systems, that will not only make the systems observable, but also will maintain observability against loss of network branches. A linear programming based solution is proposed for choosing a measurement configuration that will make the system fully observable. Subsequently, a systematic method of appending a minimum number of additional measurements to ensure full observability against branch outages, is described. Contingencies considered in this paper relate to the loss of any single branch. However, the method can be extended to the case of multiple contingencies, provided the cost of adding more meters is financially justifiable. Numerical examples illustrating the proposed method, are given in the paper     

About the significance of PD measurements in liquids

This paper presents investigations concerning the variations and significance of PD measurements in mineral oil, when detectors with different frequency response are used. Typical durations of discharge phenomena in liquids are much longer than in other media, and the measurement technique must be adapted accordingly. However, depending on the application concerned, this is not always possible. In this study, experiments and calculations are carried out to determine typical errors produced when classical RLC measurement impedances with various frequency responses are used to measure PD's in liquids. Experiments are done with corona and creeping discharges in mineral oil, and compared with corona and spark discharges in air. These examples allow us to conclude that when a calibrated high frequency PD measurement system is used, the ratio of measured to actual charge is much lower for discharges in liquids than in gases. If measurements are carried out on a practical device that may include various types of PD sources, the high frequency measurement system will strongly underestimate discharges in liquids compared to other discharge types. This discrepancy versus discharge type increases when the frequency response of the measurement system is increased.     

基于超短期负荷预测和混合量测的线性动态状态估计

目前电力系统量测主要是广域测量系统(wide area measurement system,WAMS)和数据采集与监控系统(supervisory control and data acquisition,SCADA)混合量测并存。利用量测变换技术,将SCADA系统下支路功率量测和节点注入功率量测转换为等效的电流相量量测,并与WAMS量测组成混合量测系统,在此基础上提出了直角坐标系下的线性动态状态估计算法。此外,采用高精度的母线超短期负荷预测并通过潮流计算得到预测值,实现了系统状态的实时跟踪预测。该算法减少了动态状态估计的计算时间,提高了动态状态估计的计算精度。采用IEEE14节点系统对提出的算法进行了验证。     

一种计及衰减直流分量干扰的动态同步相量 测量算法

动态同步相量测量在电力系统动态行为监测中发挥着重要作用.但是当电力系统发生故障时,故障电流中存在的衰减直流分量,会严重影响动态同步相量测量的准确性.对此,提出了一种动态同步相量测量新算法.具体实现上,将衰减直流分量近似表示成一个较低频率的动态余弦分量,再基于频域采样定理,构建含基波分量和动态余弦分量的故障电流信号模型,进而形成了相应的动态同步相量测量新算法.仿真测试结果表明,存在衰减直流分量干扰下,所提出的动态同步相量测量新算法比基于泰勒信号模型的测量算法准确,而且计算量小,适合于在线应用.     

Dynamic thermal rating of power lines – Model and measurements in rainy conditions

The transfer capabilities of overhead power lines are often limited by the critical power line temperature that depends on the magnitude of the transferred current and the ambient conditions, i.e. ambient temperature, wind, precipitation, etc. To utilize existing power lines more effectively and more safely concerning the critical power line temperatures and to enforce safety measures during potentially dangerous events, dynamic assessment of the thermal rating is required. In this paper, a Dynamic Thermal Rating model that covers the most important weather phenomena, with special emphasis on rain, is presented. The model considers a dynamic heat generation due to the Joule losses within the conductor and heat exchange with the surrounding in terms of convection, radiation, evaporation, rain impinging and solar heating. The model is validated by comparison of the skin and core temperature of the power line with measurements under realistic environmental conditions.     

Midterm stability evaluation of wide‐area power system using synchronized phasor measurements

In recent years, the PMU (Phasor Measurement Unit) has received a great deal of attention as a synchronized measurement system of power systems. Synchronized phasor angles obtained by the PMU provide valuable information for evaluating the stability of a bulk power system. The aspect of instability phenomena during midterm tends to be more complicated, and the stability analysis using the synchronized phasor measurements is effective in order to keep a complicated power system stable. This paper proposes a midterm stability evaluation method for the wide‐area power system using synchronized phasor measurements. By clustering the power system to some coherent groups, step‐out is predicted on the basis of an aggregated two‐machine equivalent power system. The midterm stability of a longitudinal power system model of Japan's 60‐Hz systems constructed by a hybrid‐type power system simulator is practically evaluated using the proposed method. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(1): 25–32, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10274     

基于动态分区和多估计准则的电力系统自适应鲁棒状态估计

随着当前智能电网技术的高速发展,电力系统的组成和运行方式愈发复杂,对状态估计的鲁棒性和实时性也产生了更高的需求.为此,提出一种基于动态分区和多估计准则的电力系统自适应鲁棒状态估计.通过模糊c均值聚类筛选出系统中的可疑量测集,进而根据可疑量测的空间分布实现系统动态分区.考虑到不同估计器各自的特点和适应性,针对可疑量测区域和正常量测区域自适应选取不同的估计准则,在保证估计精度的同时兼顾计算效率.为了保证边界节点信息和联络线传输功率的一致性,引入边界协调信息作为等式约束,并基于交替方向乘子法进行求解.通过IEEE标准系统进行测试,结果表明所提方法具有较好的估计精度和鲁棒性,并且其估计效率较加权最小绝对值估计法有明显提升.     

Earth ground resistance testing for low-voltage power systems

A quality connection to earth through the grounding electrode system for a commercial or industrial facility's power system is necessary for: (1) providing a low impedance path for lightning stroke current dissipation, (2) the reduction of “Step” and “Touch” potentials under line-to-earth fault conditions, and (3) the dissipation of electrostatic charges. Previously accepted test methods for resistance measurements of a grounding electrode system may indicate incorrectly that high or low resistance connections have been established. Testing of several grounding electrode systems was conducted by the author. This paper presents results of these tests to illustrate deficiencies in grounding electrode resistance test methods that have been accepted previously. Inaccuracies of various test instrument principles are also discussed. The author found that close attention to the test procedure must be given to ensure that an accurate measurement is achieved. This paper provides recommendations on measurement techniques to minimize errors and ensure valid test results     

Phasor-Based Synchronized Frequency Measurement in Power Systems

Phasor-based frequency measurement techniques have very good steady-state performance, but their dynamic performance is not well documented. This paper analyzes a phasor-based frequency measurement method that considers the effect of dynamic frequency, and proposes a method to improve the dynamic performance of the phasor-based frequency measurements. Simulation results verify the effectiveness of the proposed method. Results of laboratory experiments are presented to show the performance of the proposed method compared to frequency measurements obtained from commercial phasor measurement units (PMUs).     

基于WAMS的电网扰动识别方法

电网规模的不断扩大带来了潜在的安全问题。为保证电网安全可靠运行,运行人员需要及时掌握电网扰动情况,并采取适当的控制措施。近年来,基于全球定位系统（GPS）技术构建的广域测量系统（WAMS）能够实时地将全网同步测量信息传送至调度中心,使全网动态监测成为可能。文中提出了基于WAMS的电网扰动检测和识别方法,以便根据不同的扰动类型快速确定相应的控制措施,抑制其对系统的影响。首先,从理论上对电网中常见扰动（短路、切机和切负荷）的特征进行了分析;在此基础上,应用模式识别的思想,初步探讨了借助于电力系统中同步相量测量单元（PMU）实时量测量所反映的特征进行扰动识别的方法与实现步骤;最后,通过华北电网扰动仿真进一步明确扰动的特征,验证了理论分析的正确性和利用所提出的方法区分电网扰动的有效性。     

适用于保护控制的同步相量测量方法

近年来,电力系统电力电子化特征导致输配电网动态特性耦合紧密,系统性故障频发。同步相量测量单元(PMU)在动态安全控制中作用愈发重要。适用于智能配电网的同步相量测量装置的研究也得到广泛开展。如何在当前复杂电气信号条件下保证相量测量精度的同时,缩短其阶跃条件下的响应时间对保护控制应用至关重要。文中提出一种适用于保护控制的同步相量测量方法。该方法揭示了阶跃信号对相量测量的影响机理,分析了相量模型参数在阶跃信号条件下的行为规律,提出了信号阶跃识别方法。进一步,揭示了阶跃量大小与动态相量模型参数突变量的线性关系,提出了阶跃过程中相量修正方法,减少了相量计算的响应时间。仿真与实际录波数据测试验证了所提方法可有效减少响应时间,为智能配电网保护控制提供快速准确的测量数据。     

A novel measurement method of temperature model for bioreactor

A novel measurement method of temperature model for bioreactor has been proposed. Temperature is the key parameter in monitoring the bioreactor operation. However, the system input signal of bioreactor is delayed, and model parameters are uncertain, so the output of temperature is non-steady-state. Many dynamic measurements are not steady so that it cannot be described by variables constant in time. In this paper, we adopt the monopulse signal as input so that the output of the bioreactor system is steady. This method has a powerful ability to steady the output of the bioreactor. In view of the measurement results, it can be seen that the model dynamic measurement approaches the real process. The analytical expression of the monopulse response for the temperature model of the bioreactor is obtained. The novel measurement approach is simple and can be easily adopted by industry.     

Recent developments in the pressure wave propagation method - [Feature Article]

Performing measurements is an essential part of understanding physical phenomena. Hence, numerous measuring techniques have been developed to study space charge build-up in dielectrics. This macroscopic accumulation of charge modifies the electric field and can lead to aging and premature failure of electrical insulation. On the other hand, charge accumulation is essential to the operation of devices such as electret- or piezoelectric-based sensors. It is therefore essential to study charge build-up in order to design insulating materials in which excessive charge does not accumulate, or electrets in which a sufficiently large amount of charge accumulates to ensure adequate device operation, and the stability of that charge in time is sufficient to ensure an acceptable device life-time. This paper focuses on the measurement method using a pressure wave to perturb the charges. That method is commonly called the pressure-wave-propagation (PWP) method. A pressure wave enters the sample through one of its interfaces. As it travels through the material at the velocity of sound, the charges encountered are mechanically displaced.     

基于相量量测的电力系统线性状态估计

分析了相量量测装置的量测误差情况,指出了相量量测参与状态估计计算的必要性。在完全使用相量量测的情况下,给出了基于直角坐标系的实数形式的电力系统线性量测方程和相应的线性静态状态估计算法。对负荷预报加潮流计算的系统状态预报方法进行改进,通过对误差协方差阵计算公式的推导与简化,提出了新的预报误差协方差阵计算公式,并将其与线性量测方程相结合,提出了基于相量量测的线性动态状态估计算法。最后讨论了线性状态估计算法的使用条件,并采用IEEE30节点系统对提出的算法进行了验证。     

电源控制器频率特性响应测试分析

目前电源控制器(PC U)频率响应分析主要是关注理论分析和数学模型,很少提到需要进行测试来保证系统的稳定性。频率响应特性的测试在现实产品设计、研发过程中的重要性要比理论分析重要很多。特别是对于卫星平台化的控制器控制环路的稳定性测试可以最大程度地降低系统风险。     

WAMS-based detection and early-warning of low-frequency oscillations in large-scale power systems

The phasor measurement units (PMU) and wide-area measurement systems (WAMS) have been widely established in modern power systems to improve the monitoring of the system behavior as well as the system control. In this paper, an integrated scheme for the monitoring and detection of low-frequency oscillations has been developed, based on our extensive experience in using Prony algorithm for oscillation analysis in practical WAMS projects. By analyzing the real-time synchro-phasors, the proposed scheme is competent to identify the characteristics of the low-frequency oscillations in real-time and alert the operators once the oscillation is under-damped or divergent. To ensure accurate monitoring of system dynamics and reliable detection of dangerous oscillations with noise-polluted WAMS measurements, several key signal-processing techniques are implemented, including delicate designing of prefilters, Prony analysis result correction, and comprehensive indices for stability evaluation. In the end, the developed scheme is tested with simulated signals and measurements from practical power systems. Its applications to large-scale power grids for detection and early-warning of low-frequency oscillations are also presented. The results have convincingly demonstrated the validity and practicability of the developed scheme.     

发电机同期系统试验及并网过程分析

详细分析了湖南某电厂(2×600 MW)2号机组同期系统静、动态试验内容及试验数据,着重提出了为保证机组顺利并网所必须进行的静态试验和整组试验的试验方法和技术措施.     

基于80C196的多功能铁轨检测装置的研制

铁路参数测量一般都要涉及到人为、环境、参数分散性等因素。本文研制了一种基于单片机80C196的高精度多功能装置,合理使用了A/D转换器的有限分辨率,保证输出在足够的精度。轨道动态测量系统采用运动测量方式,由电气测量系统与运动部件(机架和轮子)组成并组装成一体。并以手动推行方式控制测量仪的行进速度和运动过程测量工作,手动推行作用点放在整机的重心位置。小车该测量装置具有LCD显示,键盘操作,现场打印,U盘保存,声音报警。在软硬件设计上,考虑了装置运行中不同现场参数的影响分别采取了多重模拟滤波和数字滤波的方法。同时,该系统具有调试方便、使用灵活等特点,已经研发成功并运行良好。