基于交流电路运行特性的电压稳定裕度指标

在分析交流电路临界电压崩溃特性的基础上,确定了交流电路支路临界电压崩溃的边界,提出了基于交流电路运行特性计算电压稳定裕度指标的方法。算例表明所提算法有效规避了在接近崩溃点附近潮流收敛困难的问题。     

基于广域测量的系统电压崩溃点预测

许多文章对电力系统电压崩溃问题进行了研究，其中潮流分析的方法是最常见的，大都是以Q—V曲线为基础。近些年，越来越多的人认识到电力系统电压稳定问题是一个动态问题，而电压崩溃点是可以提前预知的。随着GPS(全球定位系统)和PMU(向量测量单元)的进一步应用，广域测量技术应用范围越来越广，其用在电力系统电压崩溃点的预测也将成为必然。本文以广域测量技术为辅助手段，根据功率边缘的概念，使用电压崩溃预洲器来预洲系统中电压崩溃点的位置。     

在线多预想故障静态电压崩溃预防控制

提出在线多预想故障静态电压崩溃预防控制问题的数学模型及相应的数值计算方法。该模型以最小控制代价为目标,综合考虑了预防控制后正常运行点的可行性及多预想故障条件下的静态电压稳定裕度要求。对于多预想故障静态电压崩溃预防控制问题的求解,借鉴规划领域积极约束集策略的思想,在裕度扫描的基础上确定关键预想故障集,根据关键预想故障集计算预防控制策略,而后对预防控制后的电网进行裕度扫描,确定新的关键预想故障集,循环执行直至所有预想故障条件下的静态电压稳定裕度都得到满足。通过福建电网的数字仿真验证了模型的正确性及算法的有效性。     

基于局部网络电压相量的等值模型及其电压稳定性指标

基于输电系统中任意非PV节点及其邻近节点所组成的局部网络电压相量,建立一种新的系统等值模型。同时,在该模型的基础上提出节点电压稳定性裕度指标--节点等效负荷极限裕度(margin to node equivalent load limit,MNELL)。仿真结果表明,MNELL能准确识别系统的电压稳定薄弱节点,并且当系统某一节点的MNELL将达到0时,即该节点达到等效负荷极限时,系统将发生电压崩溃。这样,根据该指标就可方便地设置判断系统电压崩溃的门槛值,进而采取恰当的措施防止电压崩溃的发生。     

A new approach for estimating voltage collapse point based on quadratic approximation of PV-curves

The MW-distance to voltage collapse is a good indicator of voltage stability at a given operating condition in power systems. This indicator is determined using PV-curves obtained through continuation power flow (CPF) program. The CPF method performs several power flow runs requiring a large amount of computing time. This method is reliable for off-line voltage stability studies, but not very much suitable for real-time operation of today's stressed power systems. Given that, it is essential for system operators to have quick information about voltage stability, a new method is needed for a fast estimation of voltage collapse point. This is the main thrust of the presented paper. It is well known that PV-curves are approximately quadratic functions and become exactly quadratic in close neighborhood of the collapse point. Some authors used this fact and suggested methods that use two to three power flow solutions for a relatively quick, but approximate, calculation of the collapse point. The present paper, also based on quadratic approach, proposes a new method for the determination of voltage collapse that uses only one power flow solution and gives more accurate estimate of the collapse point when compared with other existing methods. Another advantage of the presented method is that the estimation becomes more accurate for stressed power systems. In addition, application of the presented method for performing the top/stable portion of the PV-curves provides an effective step-size that reduces the number of power flow runs. The method is tested using the New England 39-bus and the IEEE 300-bus test systems. The results confirm the effectiveness of the presented method.     

Preventive control based on complex-valued load-flow technique to avoid voltage instability in power systems

This paper presents a method for obtaining preventive control strategies based on nonlinear optimization for power systems which will incur voltage instability when load demand increases. An algorithm is proposed to determine an appropriate and effective control action taking into account the operating constraints to widen the margin between the present operating point and a voltage collapse point, thereby improving the system state. The method proposed here is based on a complex-valued load-flow technique using the Newton-Raphson method which has been developed already by the authors. Consequently, the preventive control algorithm also can evaluate the voltage instability in the event the present operating point becomes closer to the critical point and the system state becomes unfeasible at increased loading point. Further, in optimization, two-types of objective functions are introduced so that voltage stabilization and dissolution of constraint violation can be attained simultaneously. In addition, this paper discusses the extension of the proposed preventive control to the successive control method which carries out the control action to avoid voltage collapse while the load demand is increasing. Numerical examples for various model systems demonstrate the effectiveness of the proposed method.     

防止交直流联合系统电压崩溃措施的研究

在应用崩溃点法求得交直流联合系统电压崩溃点的基础上,利用左特征向量W和电压崩溃边界曲面Σ之间的关系计算出提高交直流联合系统负荷功率裕度的最优控制方向。在此基础上,研究可提高交直流联合系统负荷功率裕度、防止电压崩溃发生的交流系统措施和直流系统措施。     

一种计算静态电压崩溃裕度的简化实用方法

通过对基于潮流方程的计算电力系统电压崩溃裕度的扩展雅可比矩阵的迭代法,潮流方程二阶非线性特性的计入,最优乘子的引入,利用潮流多解特性引出的近似算法和入进近似算法这几种计算方法的分析比较,提出了一种计算电力系统稳态电夺崩溃裕度的简化实用的计算方法,该方法的基本思路为用改进近似计算方法计算静态电压崩溃裕度的近似值,以此近似值作为扩展雅可比矩阵的迭代法的初值,然而用计入潮流方程二阶非线性特性和引入最优乘     

基于电路模型的电压崩溃机理

摘要： 当系统负荷参数超过某一临界值时，电力系统就会发生电压崩溃。文中细致地研究了基于物理电路方程解流形的电压崩溃机理。研究结果表明：出现电压崩溃的几何本质是发电机和负荷注入支路方程的解流形与电力网络线性方程解流形在注入电流-电压空间出现非横截。文中还证明了这一非横截交点恰好对应于静态分岔点即电压崩溃的临界点。文中结果对于防止电压崩溃、保证系统安全运行具有重要意义。     

CORRESPONDENCE: DISCUSSION OF “GENERALIZED ANALYSIS AND PERFORMANCE OF RELUCTANCE MOTORS”

Abstract

Based on the boundary theorems developed in [1], a method of voltage stability analysis referred to as the Eigen-Structure Analysis method, is developed that does not require the complicated nonlinear programming calculations for evaluation of the closest boundary condition corresponding to a given power network operating point with voltage controlled and PQ buses. An algorithm for determining the stability margin and its sensitivity to bus voltages and bus injections is proposed which is capable of handling large scale power systems by utilizing the sparse matrix techniques for saving computation time and memory space. The Eigen-Structure Analysis method is applied to a number of test system models. The simulation results confirm the theory and show that the proposed stability margin decreases monotonically to zero when the system approaches voltage collapse. Simulation results for 30-bus New England Test System are included in this paper.     

基于交流电路的临界电压崩溃特性分析

针对电力系统电压崩溃问题,在简单电路的基础上,用更直观的方法对电压稳定性问题加以分析。分析交流电路的临界电压崩溃运行点,在求解交流电路的方程组过程中,采用了几何分析方法。分析得出在不同运行点情况下临界电压崩溃潮流的电流电压特性。通过分析不计电阻的交流电路临界电压崩溃时的负荷特性、电压特性,指出交流电路的工作域和崩溃域。同时分析指出,在电力系统的工作域中,交流电路的功率输送特性必须与负荷的功率特性相容。     

电力系统电压稳定与电压崩溃及负荷稳定的关系

电力系统的电压失稳、电压崩溃及负荷失稳是电压稳定问题中最基本的重要概念 ,它们既相互联系又有本质区别 ,正确和客观地认识它们之间的相互关系 ,对深入研究电压稳定问题的机理具有重要意义 .负荷稳定性是电力系统电压稳定性的最主要和最关键的方面 ,分析负荷对静态电压稳定性的影响时 ,负荷特性应当采用准静态功率—电压特性     

四川电网静态稳定裕度计算和电压薄弱区域分析

根据四川电网20013年度运行方式,运用开发的电压静态稳定分析软件对四川电网进行电压静态稳定分析,求出在几种典型运行方式下,系统的电压静稳裕度,寻找电压薄弱环节。对预防及控制电压失稳,保证四川电网安全稳定运行提供有价值的指导信息。同时,计算结果验证了所采用的软件是有实用价值的。     

考虑动态电压安全的发电机有功出力最优调整

在灵敏度方法的基础上,以系统当前运行点与最近的电压崩溃点的负荷几何距离作为电压稳定指标,提出了有效提高系统稳定裕度的发电机有功出力调整方案。在开放输电环境下,系统发生N-1故障后,首先进行电压稳定裕度分析,对于不满足系统安全运行要求的状态,计算发电机有功出力对稳定裕度的灵敏度,并以此为基准调整发电机有功出力,从而增大系统稳定裕度。IEEE 57节点系统仿真算例验证了所提出方法的有效性。     

综合考虑负荷增长和多预想故障的静态电压失稳预防控制策略

提出的综合的静态电压失稳预防控制策略以最小控制代价为目标,综合考虑了负荷增长方式和多预想故障条件下的静态电压稳定裕度约束对系统静态电压稳定性的影响。该策略分2步进行:首先考虑负荷增长的影响,若系统在未来运行点不满足静稳指标,则找出系统的薄弱区域和负荷最安全变化方向,在此方向进行合理的无功补偿;其次考虑多预想故障条件下系统的静态电压稳定裕度约束,并引入关键故障集的概念求解计算优化策略,施加控制措施后再进行扫描确定新的关键故障集,循环直至对所有故障都满足裕度要求。IEEE-39节点算例证明了该综合预防控制策略的有效性。     

电力市场环境下的电压稳定分析

传统垄断结构下电力输电系统的设计和运行原则之一是运行点不常接近安全边界。然而在新的开放电力市场环境下，电力市场的运行点倾向于越来越接近于安全边界；在这一环境下，如果无功功率支持不足，就可能出现电压失稳，电力市场为电压稳定分析带来了许多新的问题和挑战。为此分析了现有的电压稳定分析方法的机理，以及电力市场环境下的电压稳定分析遇到的新问题以及分析方法。     

面向智能电网电压崩溃路径的优化粒子群算法

随着智能电网系统的研究深入,针对复杂智能电网系统的电压崩溃路径,研究了基于智能电网系统的等效模型。通过AGENT图分析了系统脆性关系,采用一种在脆性发生时崩溃路径优化粒子群算法,给出系统内部的脆性对于系统稳定性的影响,发现脆性激发时崩溃传递路径具有多样性的解,并分析了崩溃路径。基于35 kV智能电网一次系统模型,通过对智能电网脆性电压崩溃路径的预测和控制,有效优化了整个系统性能,对智能电网系统的设计控制具有重要的指导意义。结果表明,智能电网系统节点的崩溃在各子系统层间传递,进而导致整个系统的电压崩溃。     

基于对数障碍函数的电压崩溃临界点改进算法

提出直角坐标下电压骨溃临界点计算的非线性规划模型，并充分利用该模型的二次性，对基于对数障碍函数的预测校正原－对偶内点法进行改进，最后通过对ＩＥＥＥ－３０节点测试系统的仿真计算验证了该算法的有效性。     

An innovative technique to evaluate network equivalent for voltage stability assessment in a widespread sub-grid system

The equivalent two-bus network models currently available are obtained by lumping all the series impedances and shunt admittances of transmission lines within a series equivalent impedance, to assess voltage stability of multi-bus power system. This paper reports the development of an equivalent pi-network model using a new methodology considering series and shunt parts of line loss separately obtained from the operational parameters of optimal power flow solution of the original multi-bus power network, which can be applied to assess the overall voltage stability status of the system accurately by developing the concept of a generalized global voltage stability margin (GVSM). Simulation results for a typical longitudinal power supply (LPS) system and a robust practical (Indian Eastern Grid) system establish that the pi-equivalent model obtained by the proposed method is highly promising for assessing voltage stability of any power system at any operating point in global scenario in a better way as compared to available series equivalent model. Continuation power flow (CPF) method has also been adopted here to verify the potential of the proposed method for voltage stability assessment. In the proposed equivalent network the generators have been modeled more accurately considering optimal operating criteria.     

北京电网夏季电压稳定分析

北京电网是典型的受电大系统，电压稳定性就是负荷的稳定性。特别是夏季大负荷方式下，主网部分设备负载率高，存在某些异常运行方式．随着用电负荷的逐年增长，电压稳定性问题日趋严重，提出了基于电压稳定多项指标的分档加权预想事故筛选算法，借助于BPA潮流分析程序，计算了北京电网度夏正常运行方式和预想事故下的有功裕度指标、无功裕度指标和灵敏度指标，并排序比较指出北京电网夏季的薄弱节点薄弱区域和预想事故下系统电压稳定的削弱程度，为制定防止电压崩溃的预案提供了量化依据。