一种混合递推的DFT相量测量算法

电力系统的稳定、安全、经济的运行需要快速准确地采集实时的电压和电流的有效值(幅值)与相位.然而,电网的频率是波动的,使采样很难做到对被测信号进行整周期截断,FFT算法的栅栏效应和泄漏现象,将导致明显的测量误差.提出一种混合递推的DFT相量测量算法.首先,利用频谱修正法获得精确的电网频率,然后采用相量校正算法纠正误差.通过滑动数据窗的递推算法提高了计算效率和时间响应,仿真证实了所提算法是有效和可行的.     

一种混合递推的DFT相量测量算法

电力系统的稳定、安全、经济的运行需要快速准确地采集实时的电压和电流的有效值（幅值）与相位。然而,电网的频率是波动的,使采样很难做到对被测信号进行整周期截断,FFT算法的栅栏效应和泄漏现象,将导致明显的测量误差。提出一种混合递推的DFT相量测量算法。首先,利用频谱修正法获得精确的电网频率,然后采用相量校正算法纠正误差。通过滑动数据窗的递推算法提高了计算效率和时间响应,仿真证实了所提算法是有效和可行的。     

一种适用于同步相量测量的新算法

在异步采样的情况下,离散傅里叶变换(DFT)由于频谱泄漏及栅栏效应,计算结果不够精确,不能满足同步相量测量精度的要求.对现有的同步采样及误差消除方法进行了分析,提出了一种新的相量测量算法.通过线性插值计算,得到采样序列两相邻过零点进行频率跟踪,由所测频率对采样序列进行同步修正得到满足同步采样的新序列,采用DFT进行相量估计.仿真结果表明:该算法具有高精度、计算量小等特点,能够满足同步相量测量对精度及实时性的要求.     

一种适用于同步相量测量的新算法

在异步采样的情况下,离散傅里叶变换(DFT)由于频谱泄漏及栅栏效应,计算结果不够精确,不能满足同步相量测量精度的要求。对现有的同步采样及误差消除方法进行了分析,提出了一种新的相量测量算法。通过线性插值计算,得到采样序列两相邻过零点进行频率跟踪,由所测频率对采样序列进行同步修正得到满足同步采样的新序列,采用DFT进行相量估计。仿真结果表明:该算法具有高精度、计算量小等特点,能够满足同步相量测量对精度及实时性的要求。     

适用于闭环控制的快速相量计算方法

近年来,大量电力电子设备在电力系统电源、电网与负荷侧广泛应用,导致电力系统跨区域、跨电压等级的系统性连锁故障逐渐增多,亟需精细化闭环控制。这要求同步相量测量装置(SynchrophasorMeasurementUnits,PMUs)在保证测量精度的同时,具有快速的响应速度。针对这一问题,提出了一种适用于闭环控制的快速相量测量方法。该方法分析了传统DFT算法在系统动态条件下的测量误差特性,揭示了时标位置对相量测量精度与上传延时的影响。为减少PMU上传延时,研究了将时标打在时间窗尾部时相量测量误差与动态相量模型参数的规律,提出了相量修正方法,在减少上传延时的同时兼顾了测量精度。仿真测试验证了所提方法的测量精度与上传延时远高于PMU标准对保护控制类PMU的要求,可用于复杂电力系统闭环控制应用。     

基于相量量测的电力系统谐波状态估计算法的研究

基于相量量测单元的电力系统谐波状态估计技术,可选取电力网络的节点谐波电压为状态量,支路电流、节点注入电流和节点电压相量为量测量,从而使谐波状态方程成为线性方程.本文根据这个特点,再结合量测方案的不同情况,提出了在冗余量测和基本量测时,采用便于工程实际应用的乔累斯基算法来求解线性谐波状态方程,其计算量只是高斯消元法的一半,且不用考虑选主元,大大减少了计算的时间;在量测矩阵欠定时,采用奇异值分解算法,不仅可以为欠定的状态方程提供稳定的最小二乘解,而且该算法本身具有可观性分析的功能,不需要采用其它算法进行可观性分析,从而极大地简化了谐波状态估计分析的难度.最后通过仿真程序验证了这两种算法在谐波状态估计求解问题中的有效性和可靠性.     

一种高精度的电力系统相量测量方法

在传统的离散傅里叶算法的基础上提出了一种新的相量测量算法,首先,对纯基波信号,该算法利用2个数据窗的DFT变换数据推导出了一个关于频率偏移的方程,解此方程后可以求出基波信号的频率、幅值及相位的精确解,在推导过程中无任何近似误差,有效减小计算量的同时提高了测量的精确性.接着,为了提高谐波情况下测量的精度,利用迭代法对原采样序列进行修正,然后在最终的修正序列上用前面的算法进行相量测量.最后,分别对存在谐波和噪声的情况进行了仿真,结果表明,该算法在各种情况下具有测量精度高的优点.     

A novel hybrid state estimator for including synchronized phasor measurements

State estimator is crucial for on-line power system monitoring, analysis and control. With the increasing use of synchronized phasor measurement units (PMU) in power grids, how to utilize phasor measurements to improve the precision of state estimator becomes imperative. Since there are lots of traditional measurements in SCADA system and it is hard for phasor measurements to replace them in the near future, the best way is to develop hybrid state estimator which includes both phasor and traditional measurements to get better behavior. In this paper, a novel state estimator for including voltage phasors, branch current phasors and traditional measurements is proposed. The detailed model and how to calculate covariance matrix of PMU measurements are described in detail. New England 39-bus system and IEEE 118-bus system are used as test systems and the simulation results demonstrate that the proposed state estimation algorithm improves the precision greatly and gets better behavior as compared with other state estimators with or without phasor measurements.     

一种快速矩阵束相量提取方法的研究

电力系统的监控、保护及模态识别通常依赖于相量参数的准确程度,因而快速准确地提取各类相量十分重要。本文基于矩阵束算法,利用前后两个耦合时段的输入信号采样阵构成一个方阵,该方阵的特征值不仅表示前后两个时刻工频、谐波及其他各类分量的复幅值之比,也表示着各分量的极值点信息。通过求解该方阵的特征根,在已知初始相量前提下,即可得到所需各分量的相量值。为减少求解计算量,本文利用方阵的Krylov子空间来构造相量的最小多项式,快速求解代表特定分量的特征值。理论分析和仿真结果表明,本文提出的快速矩阵束相量提取方法,与传统矩阵束法相比,计算量显著减小且实现方式简单,不受非目标分量及频率偏移的影响,在较短数据窗内仍具有较高精度。该方法适用于工频信息的提取,也适用于各次谐波信息。     

A novel short-window algorithm of phasor computation for EHV line protection

A novel phasor computation algorithm is presented in this paper. The real and imaginary part filters of this algorithm have identical magnitude frequency characteristic (IMFC) at all the frequencies and orthogonal phase frequency characteristic (PFC) at fundamental frequency. Considering the conditions of the same magnitude frequency characteristic (MFC) and the orthogonal PFC, the two-sample algorithm is derived. Once two-sample orthogonal filters with IMFC are obtained, the algorithm design is just to select proper shapes and lengths of windows, which determine the filtering performance and response-time, respectively. This method could be applied to design filter in any window-length, especially in short-window. Therefore, this class of phasor algorithms is suitable for EHV transmission line protection where a short-window is crucial for fast response and better operation performance. The proposed algorithm has been applied to a series of EHV relay devices by China Xuchang Relay Group.     

Neuro-fuzzy networks for voltage security monitoring based onsynchronized phasor measurements

The ability to rapidly acquire synchronized phasor measurements from around a power network opens up new possibilities for power system operation and control. A novel neuro-fuzzy network, the fuzzy hyperrectangular composite neural network, is proposed for voltage security monitoring (VSM) using synchronized phasor measurements as input patterns. This paper demonstrates how neuro-fuzzy networks can be constructed offline and then utilized online for monitoring voltage security. The neuro-fuzzy network is tested on 3000 simulated data from randomly generated operating conditions on the IEEE 30-bus system to indicate its high classification rate for voltage security monitoring     

Nondominated sorting genetic algorithm for optimal phasor measurement placement

This paper considers a phasor measurement unit (PMU) placement problem requiring simultaneous optimization of two conflicting objectives, such as minimization of the number of PMUs and maximization of the measurement redundancy. The objectives are in conflict since the improvement of one of them leads to the deterioration of another. Instead of a unique optimal solution, it exists a set of best tradeoffs between competing objectives, the so-called Pareto-optimal solutions. A specially tailored nondominated sorting genetic algorithm (NSGA) for a PMU placement problem is proposed as a methodology to find these Pareto-optimal solutions. The algorithm is combined with the graph-theoretical procedure and a simple GA to reduce the initial number of the PMU's candidate locations. The NSGA parameters are carefully set by performing a number of trial runs and evaluating the NSGA performances based on the number of distinct Pareto-optimal solutions found in the particular run and distance of the obtained Pareto front from the optimal one. Illustrative results on the 39- and 118-bus IEEE systems are presented.     

一种改进状态模型的动态相量测量算法

同步相量测量技术的一个关键问题是如何实时有效地估算包含电力参数信息的相量值。建立了计及电压、电流、频率、相位、有功和无功等电气参量的状态估计模型,在自适应陷波提取基波电压电流分量的基础上,借助无迹卡尔曼滤波递推框架进行状态估计,实时获得电压、电流、频率、相位、有功和无功功率等电气参量的估计值。通过状态扩展系统模型,增强了系统的鲁棒性,在前端增加自适应陷波器,有效降低了谐波对跟踪性能高的影响。四组仿真对比分析说明提出的新算法较文献[12]方法而言,对频率突变和幅值突变的影响更小,跟踪性能受谐波的影响程度更小,在频率缓变情况下的跟踪性能优于文献的方法,从而说明提出的新方法更优。     

A new frequency tracking and phasor estimation algorithm forgenerator protection

Digital generator protection is a complex and difficult problem. Analog and solid state methods have been successfully applied to generator protection in the past and implementation of these functions in a digital device is a continuing trend. This paper explores a new method to implement frequency tracking and phasor estimation in a numerical relay. A new algorithm is presented which utilizes a variable window discrete Fourier transform (DFT) for frequency tracking. Use of the DFT to compute the phasor estimates at a frequency other than the assumed frequency is outlined first. Next, a new technique for tracking the frequency is outlined. The paper concludes with testing of the new algorithm     

低频采样下基于卡尔曼滤波的同步相量测量算法的研究

各种基于定间隔采样的传统相量测量算法在跟踪速度和测量精度上不能很好地统一,在低频采样情况(每周波4~8个采样点)下提出一种基于线性卡尔曼滤波技术的10状态卡尔曼滤波模型,用于实时跟踪电力系统的电压有效值、频率、频率变化率和初相角,为系统提供精确的参数。结合二元泰勒展开公式,推导出各个参数的计算公式,并依据信号模型选取合适的时间区间保证算法对突变信号的响应速度。从采样频率、数据窗持续时间和算法对突变信号的跟踪精度方面对算法进行了讨论,结果表明使用该算法可以在低频采样下获得较高的参数估计精度。     

Synchronized phasor measurements of a power system event

The paper describes one of the first field measurements of positive sequence voltage phasors at key system buses during a switching operation at Plant Scherer of the Georgia Power Company. The phasor measurements were synchronized using time transmissions from the Global Positioning System (GPS) satellites. The data show the first ever observation of power swings recorded via synchronized phasors at several points on an integrated power network. Measurements were made on the Georgia Power Company (GPC) system, the Florida Power and Light (FPL) system, and on the Tennessee Valley Authority (TVA) system. The disturbance was also simulated on a stability program. Results of the simulation, and a comparison with the observed field data are also included     

Multi area state estimation using synchronized phasor measurements

This paper investigates the problem of state estimation in very large power systems, which may contain several control areas. An estimation approach which coordinates locally obtained decentralized estimates while improving bad data processing capability at the area boundaries is presented. Each area is held responsible for maintaining a sufficiently redundant measurement set to allow bad data processing among its internal measurements. It is assumed that synchronized phasor measurements from different area buses are available in addition to the conventional measurements provided by the substation remote terminal units. The estimator is implemented and tested using different measurement configurations for the IEEE 118-bus test system and the 4520-bus ERCOT system.     

基于改进泰勒加权最小二乘法的相量测量算法

大部分相量测量算法将信号相量作为一个静态模型,因此对电网中经常发生的电压幅值和相角波动特别敏感。基于标准频率下动态相量模型的泰勒加权最小二乘法(Taylor Weighted Least Squares, TWLS)不仅提供了相量值,还提供了相量导数值,可以提高对电网动态状况的监测。在此基础上,提出了一种基于基波频率值的改进泰勒加权最小二乘法。首先用非线性最小二乘法得到基波频率值。然后介绍了基于测量基波频率值的改进泰勒加权最小二乘法推导过程,并对该算法所涉及的窗函数、数据窗长度和泰勒多项式阶数进行分析选择。最后采用不同的信号模型和实际数据来检验算法的性能。仿真结果表明:提出的改进泰勒加权最小二乘法的测量精度满足要求。     

一种滤除衰减直流分量的快速算法

针对全周傅氏算法在处理含有衰减直流分量的周期信号时会产生误差的问题,在全周傅氏算法的基础上提出了一种滤除衰减直流分量的快速算法,增加一个采样点,进行两次全周傅氏变换,经过理论推导,得到各周期分量的精确计算公式。并通过仿真证实,此算法具有速度快,精度高的特点。