计及发电机励磁调差系数的潮流计算方法分析

研究了发电机励磁调差系数与无功功率的关系,以及计及发电机励磁调差系数的潮流计算模型。该模型摒弃了传统潮流中将发电机节点设为PV节点的假设,而将发电机节点的电压看成随无功功率而变化的变量。以IEEE14、IEEE30、IEEE118节点和某省实际电网等不同规模的电力系统为算例,并与传统潮流对比,结果表明该算法不仅对小规模电力系统具有很好的收敛性,对大规模电力系统也具有良好的收敛性。本文方法可使潮流计算结果更加准确,无功功率在发电机之间的分配更加合理,并且在维持电压稳定、降低系统网损方面具有优越性。     

多平衡机潮流计算在调度员潮流中的应用

在调度员潮流中。多平衡机潮流计算比常规潮流计算更加符合电力系统的实际情况。计算结果更为准确。围绕系统不平衡功率的计算，提出了多平衡机潮流计算的三种算法：静态法、准动态法和基于动态潮流理论的动态法。并对每一种算法进行了详细介绍。平衡机群中各平衡发电机进行不平衡功率的分配可以采取多种分配方式。且需要考虑发电机有功出力的限制。对照IEEE14节点标准系统的测试结果表明本文的计算方法是有效、可行的。     

电力系统潮流计算中风电场节点的处理方法

比较了国内风电场两种最主要机型异步发电机和双馈异步发电机的差异,并基于两种发电机的稳态数学模型,分别给出了电力系统潮流计算中两种机型以及不同运行方式下风电场节点的处理方法。最后,结合算例进行了计算,验证了所述方法的正确性。     

一种无迭代的电力系统潮流计算方法

把Taylor级数引入到电力系统潮流计算当中．提出了一种无迭代的求解潮流的新方法。通过对逆潮流方程组进行Taylor级数展开，可以把潮流的结果表示成为一系列级数项之和。经一个实际的5节点系统和IEEE-14节点系统验证。表明这种无迭代的电力系统潮流计算方法是正确和有效的。     

基于全纯嵌入法的非迭代电力系统最优潮流计算

通过求解电力系统最优潮流获得各发电机的有功出力对于电力系统经济运行具有重要意义。全纯嵌入法是一种用于潮流计算的非迭代算法。该文将全纯嵌入法应用于最优潮流的求解,首先推导出约束条件和KKT条件的全纯嵌入形式;然后通过上述两组方程交叉得到求解通式,递归地计算出节点电压和发电机有功出力的表达式;最后根据解析表达式直接得到各发电机的有功出力,进而计算系统的最低发电成本。在IEEE 3节点、4节点、30节点、118节点和新英格兰39节点电力系统上的仿真结果验证了所提方法的可行性和准确性。     

电力系统潮流计算中的频率计算

在电力系统潮流计算之前,先进行频率计算.为提高频率和潮流计算精度,通过调整发电机和负荷,比较真实地模拟了实际电力系统发生扰动后的动态过程,提出频率计算流程;并以Ⅰ型考题为例进行调频计算,计算结果与给定结果一致,验证了该计算方法的正确性.     

计及发电机运行极限的电压稳定临界点计算

为解决潮流雅可比矩阵在电压稳定临界点的奇异问题,在传统连续潮流PV-PQ转换逻辑的基础上,计及发电机定转子电流约束来表达发电机的无功动态特性。基于电力系统非线性等值泰勒级数,建立了计及发电机定转子电流约束的节点电压和负荷电流的非线性等值模型。在负荷功率因数任意变化的情形下,将节点电压和负荷电流展开为节点电压模的泰勒级数,能够较大范围地直接计算系统极限潮流和临界电压,加快了计算速度,同时也更加接近电力系统实际运行状态。IEEE典型系统的仿真结果,证明了所建模型的正确性和快速性。     

基于图分割的潮流计算中的节点优化编号

随着社会的发展,电网的拓扑结构变得越来越复杂,电力系统潮流计算的维数也越来越大,适当的节点优化编号能够有效地加速电力系统的潮流计算。电力网络作为一种无标度的网络,可以抽象成图来表示各个节点之间的拓扑关系,为了解决电力系统潮流计算中的节点优化编号问题,提出了基于图分割算法中的多层次嵌套排序算法进行节点优化编号的方法,大幅提高了节电优化编号的速度,能够有效地加速大规模系统的潮流计算,并以IEEE14节点算例为例,介绍了所提方法的流程。算例结果验证了该算法无论是在速度上还是在内存占用均优于传统方法,能够更有效地满足大规模电网潮流计算的需求。     

获取电力系统运行方式的约束潮流方法

提出一种获取电力系统运行方式的约束潮流方法。该方法通过松弛多台发电机出力来提高潮流解域,再利用对松弛发电机出力及节点电压幅值进行限制来保证潮流解的合理性。将约束潮流模型转化为非线性优化问题,用原对偶内点法进行求解,即可获得电力系统的一种可行运行方式。该方法对于病态潮流可以扩大其收敛域,对于潮流无解问题,可以根据发电机出力完全松弛时的潮流解来调整其它发电机出力。在增广直角坐标下,该方法求解所用海森矩阵全为非常稀疏的定常矩阵,可提高程序设计效率。IEEE 118节点系统和陕甘联网系统的仿真结果证明了所提方法的有效性和灵活性。     

含电力机车负荷的一种不对称潮流计算方法

以电力机车为不对称负荷，根据P-Q分解法基本原理，推导了一种电力系统不对 称潮流计算的数学模型。模型中发电机内电势节点不直接参与迭代，可以充分运用稀疏技术 ，从而提高计算速度和减少占用计算机内存。     

稳态控制潮流的设定空载频率及空载电压算法

针对电力系统中、长期电压稳定分析等需确定各发电机组出力的潮流计算问题，根据稳态运行时，发电机组的输出功率由机组的有功—频率静态特性和无功—电压静态特性所确定，该文列出计及控制环节的求解方程，提出不需设置平衡节点的给定有功—频率特性的空载频率fo、无功—电压特性的空载电压Voo(foVoo）的潮流算法。在非限制情况下，该算法满足任一机组的调节，影响了全系统各机组的输出；系统中的任一扰动，全系统参与一次自动调节的机组均有响应的实际情况。5节点系统和IEEE30节点系统算例说明，该算法可用于分析控制目标和控制参数对电力系统潮流的影响。     

基于PSCAD的双馈风电机组建模与仿真

双馈感应风电机组仿真建模研究的文献很多,但鲜有描述双馈风电机组详细建模过程的。为此,介绍在PscAD／EMTcD软件中建立包含风力机、双馈风力发电机、变频器和控制系统的双馈感应风电机组的全过程,在此基础上搭建系统电磁暂态仿真模型并进行仿真分析。仿真结果表明所构建的模型可实现有功、无功功率的解耦控制和最大风能跟踪;实现保持直流母线电压恒定和交流侧单位功率因素控制;与实际双馈风电机组的风速-输出功率具有较高的一致性。     

Power flow tracing based transmission congestion pricing in deregulated power markets

The objective of this paper is to propose a simple transmission congestion pricing scheme based on tracing principle by considering generator fixed cost, cost for incurring loss and transmission congestion cost. Restructuring has brought about considerable changes by the virtue of which electricity is now a commodity and has converted into deregulated type. Such a competitive market has paved way for innumerable participants. This concept of restructuring has led to overloading of transmission lines. In this paper, power flow tracing has been employed by using suitable optimization algorithm, where the real power generation has been maximized. Congestion in the transmission line has been produced in a new fashion by maximizing the real power demand. The power flow under normal operating condition and congestion is determined and hence the difference in power flow is estimated. Based on the estimated power flow difference, the transmission line congestion cost is computed. Pool model and bilateral model has been considered in simulation study to introduce the concept of deregulation. The proposed method is tested and validated on Modified IEEE 30 bus test system and Indian utility 69 bus test system.     

一种判别电力系统电压稳定和功角稳定的新方法

本文以恒电势模型为基础，导出了发电机矩阵和负荷矩阵的概念，由此给出了一种判别电力系统压稳定和功角稳定的新方法，对一个６机２２节点系统的计算验证了此方法的有效性。     

Low-order dynamic equivalent estimation of power systems using data of phasor measurement units

This paper utilizes data measured by phasor measurement units (PMUs) to extract a low-order dynamic equivalent model for power system stability studies. The estimated model is a 2-order model for synchronous machines. This model has the advantage of simplicity of classical model and considerably reduces the oversimplifying error of classical model. This method offers an alternative approach to analytical model reduction techniques based on the detailed system models. The proposed method uses the synchronized bus voltage and current phasors measured by PMUs. Using post disturbance data, electrical and mechanical parameters of the equivalent generator are estimated sequentially. Furthermore, a new approach for estimation of two-machine and single machine infinite bus (SMIB) equivalent systems are presented for analysis of electromechanical oscillations. To evaluate the performance of the proposed approach, simulations are performed on a two area 13-bus test system and real measured PMU data. Simulation results show that the estimated model can represent the dynamic behavior of the studied system with good approximation.     

电力系统动态安全分析中的PEBS/BCU分类器

提出一种用于电力系统动态安全分析的综合直接法,即ＰＥＢＳ／ＢＣＵ方法。该方法以故障点是否发生于机端为标记,若是,则采用ＰＥＢＳ方法确定临界能量;若否,则采用ＢＣＵ确定临界能量。利用这两种方法的改进方法及其优势互补性,可以显提高直接法的可靠性和计算速度。当用于互补性,可以显提高直接法的可靠性和计算速度。当其用在线动态安全分析中作为分类器时,仅有极少数偶然事故需要用在线时域仿真分析,因而能够有效地     

Analysis and assessment of VSC excitation system for power system stability enhancement

The voltage source converter (VSC) excitation system is a novel excitation system based on pulse-width modulation (PWM) voltage source converter, which is proposed as improved alternatives to the conventional thyristor excitation systems. This paper aims to provide theoretical confirmation of power system stability enhancement by the VSC excitation system. The reactive current injected to generator terminals by the VSC excitation system can be controlled flexibly. Its capability of enhancing power system stability is investigated in this paper. The simplified model of VSC excitation system suitable for use in system stability studies is developed. An extended Philips–Heffron model of a single-machine infinite bus (SMIB) system with VSC excitation system is established and applied to analyze the damping torque contribution of the injected reactive current to the power system. This paper also gives a brief explanation on why the VSC excitation system can enhance the transient stability in light of equal area criterion. The results of calculations and simulations show that the injected reactive current of VSC excitation system contributes to system damping significantly and has a great effect on the transient stability. When compared with conventional thyristor excitation systems, the VSC excitation system can not only improve the small-signal performance of the power system, but also can improve the system transient stability limit.     

Observer-based nonlinear control of power system using sliding mode control strategy

This paper presents a new transient stabilization with voltage regulation analysis approach of a synchronous power generator driven by steam turbine and connected to an infinite bus. The aim is to obtain high performance for the terminal voltage and the rotor speed simultaneously under a large sudden fault and a wide range of operating conditions. The methodology adopted is based on sliding mode control technique. First, a nonlinear sliding mode observer for the synchronous machine damper currents is constructed. Second, the stabilizing feedback laws for the complete ninth order model of a power system, which takes into account the stator dynamics as well as the damper effects, are developed. They are shown to be asymptotically stable in the context of Lyapunov theory. Simulation results, for a single-Machine-Infinite-Bus (SMIB) power system, are given to demonstrate the effectiveness of the proposed combined observer-controller for the transient stabilization and voltage regulation.     

Fully reference-independent LMP decomposition using reference-independent loss factors

The decomposition of locational marginal price (LMP) under the popular DCOPF framework generally depends on the choice of the reference bus. A previous work has achieved reference independence for the overall LMP and LMP congestion component, but not all individual LMP components. This paper proposes a method to obtain a truly reference-independent LMP decomposition such that all three components of LMP at each bus will be invariant w.r.t. the choice of the system reference bus. This is achieved with loss factors based on a new AC-based distribution factor model, which depends on the network topology and the present operating condition only, but not the system reference bus. This model gives reference-independent loss prices, which can serve for a better loss hedging financial transmission rights, since the choice of reference bus will not change the loss prices. Further, this paper uses the fictitious nodal demand (FND) model to obtain loss distribution factors (LDFs). FND gives more reasonable power flows since losses should be distributed in each individual line, rather than at load buses when the load-weighted LDFs are applied. Also, the proposed reference-independent distribution factors and loss factors may have great potentials in other areas of power system analysis.     

Optimal siting and sizing of intermittent distributed generators in distribution system

Intermittent distributed generators (IDGs), such as distributed wind turbine generator (WTG) and photovoltaic generator (PVG), have been developing rapidly in recent years. The output power of WTG and PVG highly depends on the wind speed and illumination intensity, respectively. There always exist correlations among the wind speed, illumination intensity, and bus load, which could have significant influence on the determination of siting and sizing of IDGs in distribution system. Given this background, a chance‐constrained‐programming‐based IDGs planning model, which can take into account the correlations, is developed in this paper. Latin hypercube sampling technique and Cholesky decomposition are introduced to handle the correlations. A Monte Carlo simulation‐embedded multi‐population differential evolution algorithm is employed to solve the developed model. Case studies carried out on the Baran & Wu 33‐bus distribution system verify the feasibility of the developed model and effectiveness of the proposed solving methodology. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.