Fault impedance estimation algorithm for digital distance relaying

Fault impedance is one of the major parameters that must be estimated accurately in digital distance relaying application. In this paper, a new algorithm is proposed based on symmetrical components theory. The proposed algorithm has computational advantage over previously suggested symmetrical components based algorithms. A procedure for applying shunt fault conditions to the sequence equations to estimate fault impedance of the protected transmission line is discussed. The Alternative Transient Program (ATP) that is available on personal computers was used in evaluating the proposed algorithm. ATP models a power system and simulates many fault conditions on a selected transmission line. Fault data obtained were used in calculating fault impedance using the proposed algorithm. Fault impedance estimates were inserted in relay characteristics to determine suitability of the proposed algorithm for first zone distance protection. Sample results of these studies which show stable fault distance estimates are presented and discussed in the paper     

Fast and accurate parameter estimation algorithm for digital distance relaying

Response of digital distance relaying depends on the fast and accurate calculation of parameters such as voltage and current phasors and fault impedance. This paper describes a new apparent impedance estimation algorithm that is based on modal components theory. It is shown in the paper that the proposed algorithm has several advantageous features in terms of speed and accuracy over previously suggested symmetrical and modal components based algorithms. The paper discusses a procedure for deriving a fault impedance estimation algorithm that can be used for protecting power transmission lines. The proposed algorithm was evaluated using an alternative transient program (ATP). The program models a power system, simulates many fault conditions on a selected transmission line and generates fault data. The relay software then obtains filtered, scaled and sampled data and calculates fault impedance using the proposed algorithm. The relay characteristic makes trip decisions based on the fault impedance estimates. The paper shows the feasibility of the proposed algorithm for first zone distance protection. Some results of these studies are presented and discussed in the paper.     

基于MRAS的异步电机转子时间常数实时辨识

介绍了一种基于模型参考自适应(MRAS)的感应电机转子时间常数实时辨识方法。根据MRAS系统中参考模型和可调模型的状态误差调节可调模型的参数,在线辨识转子时间常数。理论分析证明该算法具有李雅普诺意义下的全局稳定性。最后对该算法进行了仿真验证。     

基于最短电气距离的运行方式组合方法

根据复杂网络理论,将大型电力系统用带权网络模型来描述,基于此模型下的节点最短电气距离提出了一种运行方式组合方法.该方法利用节点最短电气距离表征节点间电气联系强弱的特点,给出了故障电流计算和分支系数计算的最短电气距离判据,据此找到系统内对故障电流和分支系数影响大于某一阈值的厂站,将其纳入进行方式组合,以达到优化运行方式组合的目的.     

Real-time assessment of a symmetrical component and microcontroller based distance relay

This paper presents the design, implementation and real-time assessment of a microcontroller based digital distance relay that can be used for the protection of power transmission lines. The proposed design is implemented using a general-purpose Intel 8097 microcontroller and custom-made filters, operational amplifiers, sample-and-hold amplifiers, multiplexers, and analog-to-digital converters. The relay software is based on a computationally efficient symmetrical component based fault distance estimation algorithm. Results of the performance assessment studies on this algorithm have shown promising fault distance estimates for first-zone faults on the protected transmission line. Real-time implementation of the symmetrical component based fault distance estimation algorithm is presented and discussed in this paper. Hardware and software tools were used to design and fabricate a microcontroller based distance relay using the above-mentioned algorithm. This paper describes details of the design of the distance relay. A test setup in the laboratory using a transmission line model was used to generate data to assess the real-time response of the designed relay. High-speed relay operation of the order of one cycle is demonstrated in the test results.     

An adaptive distance relay based on transient error estimation of CVT

Simple delay solutions are usually used to prevent transient overreach caused by the transient error of a capacitor voltage transformer (CVT), which is very harmful to the safety and stability of operation of the power system. A proposed real-time CVT transient error estimation approach based on the chosen fundamental wave algorithm and the rated CVT parameters consists of two stages. The first stage obtains the error coefficient. The second stage estimates the measured error of the voltage amplitude according to the secondary side voltage. A novel adaptive distance relay approach is proposed, which can adjust operating thresholds according to the error. The approach hardly affects the performance for lines of normal length and operates rapidly for short lines with close-in faults, which is verified by the simulation studies. The overall performance is improved greatly in comparison with the general approach for distance relays.     

Adaptive relative velocity estimation algorithm for autonomous mobile robots using the measurements on acceleration and relative distance

In this article, an adaptive algorithm is proposed for online velocity estimation of the autonomous mobile robots (AMRs) without positioning data received from a Global Positioning System (GPS) module or other means for odometry. Unlike the popular Kalman and particle filters that use the measurements on vectors of global (or local) position and acceleration of a mobile robot, the proposed adaptive relative velocity estimation (ARVE) algorithm requires the scalar value of measured distance to a beacon agent and also the measurement on acceleration vector, in order to generate an online estimation of the global velocity vector of a mobile robot. Combining the ARVE algorithm with the recently proposed adaptive relative position estimation (ARPE) algorithm provides a solution for online estimation of the translational states of a mobile robot without accessing the GPS data, which makes the package applicable in both indoor and outdoor environments. The stability of the ARVE algorithm is analyzed with LaSalle-Yoshizawa theorem. In addition, two simulation studies are provided to show the application of the proposed estimation package (ARVE+ARPE) for aerial AMRs in two cases corresponding to the stationary and moving beacon agents. In the simulation results, it is shown that the estimation package can be used in conjunction with the recently proposed adaptive model-free control (AMFC) algorithm to achieve desired tracking objective in autonomous movement of a quadrotor, without requiring the information on the internal dynamics of the robot.     

基于频率自适应PLL的传动系统牵引电机转速实时估计

为满足传动系统在牵引电机无速度传感器控制、速度传感器异常诊断与预测等领域对牵引电机转速精确估计的要求,提出了一种基于频率自适应锁相环的转速实时估计方法。首先针对传统锁相环(PLL)算法无法实现频率大范围跟踪问题,提出了一种前馈参考频率自适应调节的二阶广义积分锁相环(RFSOGI-PLL)算法,实现定子电流基波频率的大范围实时跟踪;再利用牵引电机转速与定子电流基波频率以及齿槽谐波关系模型,结合电机结构参数,实现了传动系统牵引电机转速大范围实时估计;最后在某型大功率交流传动系统上对所提算法的有效性进行了验证。仿真与试验结果表明,与传统PLL算法相比,所提的RFSOGI-PLL算法可有效提升算法对跟踪频率变化的适应性,满足牵引电机转速估计在快速性和估计误差等指标方面的要求。     

Real-time estimation of the electric parameters of an inductionmachine using sinusoidal PWM voltage waveforms

This paper studies the parameter estimation of induction machines. The problems associated with the parameter estimation of induction machines are analyzed through sensitivity functions. Then, models and a procedure to estimate a set of four basic parameters (r_s, σl_s, l_s, and τ_r) are proposed. The discrete-time parameter estimation models are written in the δ operator specifically because it provides good numerical properties at high sampling rates, where the discrete-time model approaches its continuous-time equivalent. This feature permits the direct estimation of the continuous-time parameters. The main feature of the proposed procedure is the possibility to estimate the parameters by using sinusoidal signals, and without the measurement of the machine speed. The experimental results obtained with the proposed estimation procedure are presented and demonstrate that it is possible to map the parameters in terms of the operating conditions of the induction machine     

基于多时间尺度状态估计的配电网实时态势预测

为有效提升泛在电力物联网建设过程中的配电网运行安全感知能力,提出了一种基于多时间尺度状态估计的配电网实时态势预测方法,该方法可实现对配电网安全态势的快速、准确预测。首先,基于多元混合量测提出了多时间尺度递归动态状态估计方法,通过状态预测与伪量测递归变换改进了已有的量测线性等效变换方法,缩短了状态更新周期,在递归变换算法中添加了校正算法以消除伪量测波动误差,提高了状态估计算法的计算速度。然后基于状态估计得到历史估计状态,采用分区多元时间序列分析方法建立了实时状态预测模型,实现了配电网的实时安全性态势预测。最后在Matlab仿真平台中基于实际算例对所提方法进行了分析,结果验证了所提配电网实时态势预测方法的准确性和有效性。     

Position adjustment method and distance estimation method of magnetic field supply and detection unit for magnetic hyperthermia

In magnetic hyperthermia, the temperature and localization of a ferromagnetic implant in a tumor region is vital in determining the effectiveness of therapeutic heating. We have developed a noninvasive wireless temperature measurement method by utilizing the magnetic permeability property of a ferromagnetic implant with low Curie temperature (FILCT) that varies with the temperature. In clinical settings, when the FILCT is injected into a tumor region, the position of the FILCT is expected to deviate from the central axis of the heating coil (drive coil). When it deviates, the magnetic flux density applied to the FILCT decreases, thus causing difficulty in detecting the temperature of FILCT via a pickup coil and heating of the FILCT at a constant treatment temperature. Therefore, to adjust the magnetic field supply and detection (MFSD) unit to be directly above the FILCT, we propose a position adjustment method by referring to three voltages induced in three pickup coils symmetrically installed inside the drive coil. By using the average value of the three voltages, we also propose a method to estimate the distance between the MFSD unit and the FILCT, which is required for wireless thermometry and determination of the optimal energy applied. The proposed methods are experimentally examined by a verification system.     

Time domain solution of fault distance estimation and arcing faultsdetection on overhead lines

In this paper a new numerical algorithm for arcing faults detection and fault distance estimation is presented. The solution is given in the time domain. It is based on the line terminal voltages and currents processing. A simple new mathematical model of arc voltage is introduced in the estimation. Thereby, the more accurate approach to fault location is derived, particularly for the close-in faults. The new algorithm can be utilized for blocking the automatic reclosing. The unknown model parameters, including the line resistance and inductance, fault resistance and arc voltage amplitude, are estimated by using the least error squares method. The new algorithm is successfully tested through computer simulation and laboratory tests     

Evaluation of contrast agent dose and diffusion coefficient measurement on vessel size index estimation

Magnetic Resonance Materials in Physics, Biology and Medicine - The goal of this study is to examine the effect of contrast agent (CA) dose and diffusion coefficient on the estimation of vessel...     

集成型车载充电系统并网模式模型预测控制策略

相较于传统车载充电系统,集成型车载充电系统(integrated onboard charger system, IOCS)在成本、功率密度等方面具备显著优势。文中基于六相永磁电驱系统设计了一台IOCS,并研究了模型预测电流控制(model predictive current control, MPCC)算法在该系统并网模式下的应用。首先,分析所提IOCS的电路拓扑并建立数学模型,同时介绍传统MPCC的实施流程。然后,针对传统MPCC计算量大、稳态性能差等不足,提出一种基于占空比优化的MPCC(MPCC based on duty cycle optimization, DCO-MPCC)策略。一方面,减少备选电压矢量数量,降低电流预测环节带来的计算负担;另一方面,提出一种占空比优化技术,改善系统稳态性能。最后,通过实验验证了所提算法的有效性与优越性。实验结果表明,DCO-MPCC策略能够显著提升系统稳态性能并减少算法计算量。充电与车网互动(vehicle to grid, V2G)工况下,网侧电流总谐波畸变(total harmonic distortion, THD)分别降低6....     

能见度仪校准系统的不确定度评定分析

能见度仪校准系统作为能见度校准的标准器,其不确定度直接影响到前向散射式能见度仪的校准结果。介绍了国家级能见度仪校准实验室的能见度仪校准系统的组成和校准方法,分析了校准系统不确定度的主要来源,依据国家计量校准规范JJF 1059.1-2012《测量不确定度评定与表示》,利用能见度测量数据,对校准系统A类和B类不确定度进行了评定分析,并对3台前向散射式能见度仪进行了校准试验。结果显示,整个校准系统在能见度3 000 m以下,扩展不确定度为5.8%,校准后的3台前向散射式能见度仪在100、500、1 000、1 500、2 000、3 000 m六个测试点的相对误差,最大为7.8%,最小为1.8%,满足能见度仪校准和实际观测要求。     

Strengths and limitations of a new phasor estimation technique to reduce CCVT impact in distance protection

This paper evaluates the performance of a new least squares approach that improves the accuracy and speed of convergence of the voltage phasors estimated during CCVT transient conditions. A justification of the validity of the linear mathematical model for the CCVT used is provided together with a short study about the risk of transient ferroresonance. Also, a discussion is presented about operating times of numerical distance relays and the importance of the new phasor estimation considered. The methodology followed to achieve a realistic evaluation in a variety of scenarios is presented. The results show the improvements achievable in most conditions, but also highlight an example scenario where the new method has limitations.     

5 GHz goes the distance for home networkng

Today, there are a number of basic networking technologies that can support data-centric home networking, including 802.11b, HomeRF, and Bluetooth. As with most new markets and technologies, what users want their home network to do is rapidly changing and evolving. Today's early-adopters want more from their home networks than just sharing PC peripherals; they want to be able to send their digital entertainment content (digital pictures, MP3 audio, and DV-based video) throughout their homes. As this "early-adopter market" rapidly changes into a mass market, today's home network must evolve to where it supports not only TCP/IP-based data, but also audio and video data that require QoS. This evolution will require changes in the architecture and implementation of wireless networks. Air5 is a solution for handling the demands of wireless home networking. Based on the lEEE802.11a PHY-layer specification, it includes enhancements for delivering range and throughput levels. Air5 also delivers triple-DES security and guaranteed QoS performance through its TDMA-based synchronous MAC. There are over 40 companies developing 5-GHz based networking technologies today, so this will be a highly competitive technology evolution.     

嵌入式计算机在车载雷达移动式冷源控制中的应用

介绍了嵌入式计算机PC/104在移动式冷源控制中的应用,分析了8259可编程中断控制编程方法以及虚拟仪表技术的算法.     

隧道照明光源的光色及可见度研究

该文阐述了隧道照明光源的光色与小目标可见度之间的关系。在两条实际隧道中对三种光源照明下的小目标可见度进行了实际的测量和计算,并且提出了小目标显色性的视觉实验方法。为研究隧道照明的小目标可见度打开了新的思路。