Design of a minimum sensitivity controller for a power system under different operating conditions taking into account the effect of local load characteristics

The effect of local load characteristics on synchronous machine stability has been studied using the analytical expressions developed for damping and synchronizing torques. The inclusion of system loads may lead to instability conditions due to negative damping. Improvement of power system stability can be achieved by sending an additional signal from an optimal pole placer controller to the input of the excitation and mechanical systems of the synchronous machines. The proposed pole placer can allocate the sytem poles to desired prescribed locations while ensuring minimum sensitivity of such poles to operating condition variations over a wide range. Controller parameters are determined by minimization of an objective function using the Powell—Botm optimization routine. Time response simulations are used to illustrate the dynamic behavior of the controlled system with wide variations of operating conditions, different local load characteristics and various exciter gains.     

系统辨识法在同步电机参数测量中的应用

现代电力系统的发展,不断对同步电机的各种动态性能计算提出了新的要求,而如何简单有效地测定同步电机参数则是动态计算的关键。通过在抛载试验中引入加权最小二乘参数辨识法,处理电枢电压和电枢电流,直接得到参数。针对参数辨识的收敛性和多值性问题,提出了一些有效的方法,如采用动态阻尼因子和动态增益矩阵,提高了参数辨识的精度和算法的稳定性。     

系统辨识理论在电力系统中的应用

阐述了系统辨识技术的基本概念,结合电力系统实际需要,提出电力系统四大参数（发电机,励磁系统,原动机调速系统以及负荷动态参数）动态建模;着重介绍了发电机及励磁系统参数的现场测试方法。     

The effects of unbalanced networks on synchronous and asynchronous machine transient stability

Untransposed lines and feeders, together with single-phase loads, impose permanent unbalanced conditions on the rest of the power system. Unbalanced phase voltages at the terminals of a machine can be represented as balanced sets of positive-, negative- and zero-sequence voltages. The negative-sequence voltage gives rise to negative-sequence current which creates excessive heating, particularly in the rotor circuits. Much attention has been paid to the heating aspect, and protection provided against this, by limiting the levels of negative-sequence current; however, power system stability studies, in particular for multimachine systems, have until now ignored the imbalance and its effects upon the dynamic response of the rotor speed of each machine. This paper reconsiders the transient stability of a single synchronous generator connected to an infinite bus and evaluates the significance of the error incurred by representing the unbalanced line and shunt load by an equivalent balanced system. The paper also reconsiders the transient stability of a multimachine system containing a synchronous generator and an induction motor when subjected to different types and degrees of imbalance and finds that significant errors are incurred under certain conditions.     

Analytical Comparison of Static and Dynamic Reactive Power Compensation in Isolated Wind–Diesel System Using Dynamic Load Interaction Model

This article presents static and dynamic reactive power compensators together for a self-excited induction generator and synchronous generator based isolated hybrid power system. Reactive power is required for excitation of the induction machine and for load under steady-state and transient state operations in an isolated hybrid power system. For small perturbation of load reactive power and input wind power, the use of a dynamic compensator alone may give better voltage stability but at a high cost; in contrast, the static compensator reduces the cost on compromising with the voltage stability. The proper rating selection of both compensators used may give the optimum solution between the voltage stability as system performance and cost of compensation. The fixed costs and voltage profiles are compared for the different participations of the fixed capacitor bank and STATCOM. The interaction of the dynamic load model is also introduced to make the system more reliable and hence a new power balance equation is derived. A 10% step disturbance in the dynamic load model as well as wind power input is considered for the system study. Four different cases designed for unique participation of static and dynamic reactive power compensators are presented. The analytical comparison is based on cost, rating selection, and voltage stability under transient condition.     

基于虚拟同步电机的负荷换流器建模及参数设计

随着电力电子技术的不断发展,负荷换流器不断接入电网中,电网逐步发展为低惯量、欠阻尼网络,电网的安全性和稳定性问题日益突出。传统负荷换流器控制下,负荷难以有效的参与电网动态调节,而虚拟同步电机技术能够为系统提供惯性支撑,因此受到广泛关注。文中介绍了负荷虚拟同步电机的工作原理,建立了负荷虚拟同步电机的小信号模型,给出了一种负荷虚拟同步电机的控制参数设计方法,该方法可兼顾系统的稳定性和动态性能。Matlab/Simulink仿真结果表明该方法中小信号模型的正确性和设计方法的有效性,能够对电网的稳定提供支撑作用。     

简化同步电机模型中的运动方程

介绍了简化同步电机模型的几种运动方程的表达式及其阻尼系数的物理意义。通过一个典型的2区域系统算例分析了各种运动方程对电力系统动态稳定特性的影响,为提高大规模电力系统仿真的准确度,提出了适用于电力系统动态稳定性分析的运动方程。     

变频空调负荷虚拟同步机化改造及其参与微网互动调控

为了提高微网系统运行的安全稳定性,充分发掘海量空调负荷资源的可调潜力,从而增强负荷响应自主性,在对空调压缩机电机控制电路改造的基础上,提出了一种变频空调负荷虚拟同步机群参与微网调频的控制方法。首先对变频空调压缩机电机进行负荷虚拟同步机控制改造,建立其控制模型;然后将空调压缩机电机进行聚合等值,便于其参与微网互动调控;接着建立了变频空调负荷虚拟同步机群参与微网互动的控制架构;最后提出变频空调负荷参与微网一次和二次调频的策略,并通过对变频空调负荷虚拟同步机群控制仿真,验证了负荷虚拟同步机化改造能够有效提升空调负荷参与调频的能力。     

不同转子结构无刷双馈电机的电磁和动态特性分析

简要介绍了无刷双馈电机(BDFM)的结构特点和工作原理,利用Ansoft/Maxwell建立笼型转子和磁障式磁阻转子的BDFM模型,进行了二维瞬态电磁场有限元计算,得出电机磁力线分布、气隙磁通密度波形,通过对气隙磁通密度波形的谐波频谱分析,得到了磁障式磁阻转子结构具有较好磁场调制效果。研究了由单馈异步牵入自然同步、亚同步和超同步运行状态的动态响应能力和机械负载突变时的转速转矩变化情况。结果表明磁障式磁阻转子BDFM在由单馈异步牵入自然同步、亚同步和超同步运行状态下,具有较好的动态响应能力,同时在加载时稳定性也较好,为进一步深入研究BDFM转子的优化设计和运行稳定性提供了参考。     

Identification of power system load dynamics using artificialneural networks

Power system loads are important in the planning and operation of an electric power system. Load characteristics can significantly influence the results of synchronous stability and voltage stability studies. This paper presents a methodology for the identification of power system load dynamics using neural networks. Input-output data of a power system dynamic load is used to design a neural network model which comprises delayed inputs and feedback connections. The developed neural network model can predict the future power system dynamic load behavior for arbitrary inputs. In particular, a third-order induction motor load neural network model is developed to verify this methodology. Neural network simulation results are illustrated and compared with the actual induction motor load response     

Construction of Lyapunov function for power system based on solving linear matrix inequality

This paper presents construction of Lyapunov functions for power systems based on solving the Linear Matrix Inequality (LMI) derived from the Lyapunov stability theorem considering the dynamics of load characteristic and AVR control system. The proposed Lyapunov function is constructed as a quadratic form of state variables and an integral term which satisfies the curl equation and the sector condition. An induction machine and a synchronous machine are considered as load characteristics. One‐machine one‐load infinite bus system is considered taking into account the flux decay effects and AVR with one time constant of the generator. To verify the proposed Lyapunov function, the transient stability assessment is shown. The critical clearing times given by the proposed Lyapunov function are compared with those obtained by the numerical integration method, and they are shown to be practical. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 158(4): 42– 50, 2007; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20328     

Effects of Synchronous Machine Saturation,Circuit Parameters,and Control Systems on Transient Stability

The effects of synchronous machine iron saturation, circuit parameters, and control systems on the power system transient stability phenomena are presented in this paper. Effect of saturation is considered to be very important on the power system steady-state and transient performances when it is required to calculate the power system stability characteristics accurately. For solid round rotor body synchronous machines, saturation effects are significant in both d- and q-axis, and because of this nonlinearity, the d- and q-axis magnetizing reactances are depressed to a considerable degree from their unsaturated values under both steady-state and transient operations. The system stability performance is also greatly influenced by the machine control system and damper circuit parameter variations.     

同步发电机-整流器-反电动势负载系统的稳定性分析

建立了同步发电机－整流器－反电动势负载系统的等效电路模型,在此基础上,导出了发电机整流系统的状态方程,求出了系统微变稳定的条件,该稳定条件比现有文献更为精确,并提出了在隐极电机转子上设置交轴短路绕组来解决系统稳定性的措施。     

Effects of Synchronous Machine Saturation,Circuit Parameters,and Control Systems on Steady State Stability

Analysis of elementary power system configuration by means of idealized model illustrates some of the fundamental stability properties of power system. Instability in a power system may be manifested in many different ways, depending on the system configuration and operating mode. Analysis of synchronous machine performance, including saturation effect, is very important. Synchronous machine performance is greatly influenced by its iron saturation. The developed synchronous machine model, and hence the power system model, which takes this saturation effect into account will also depict the effects of the control systems on power system steady state stability. The objective of this paper is to provide an overview of the power system stability phenomena, which is also dependent on the synchronous machine circuit parameters with and without automatic voltage regulator and governor systems.     

凸极同步电机V形曲线的解析计算

同步电机V形曲线能表明同步电机在大电网上运行时如何合理地调节电机的无功功率输出,是同步电机的重要运行特性曲线。已有文献的理论分析和推导大都限于隐极同步电机,对凸极同步电机V形曲线的理论分析推导较少。对凸极同步电机应用其功角方程和稳定条件,通过求解关于sin2q和sinq的3次方程的方法,分别就凸极同步电机稳定极限、功率因数、功率角的计算进行分析,得到了凸极同步电机V形曲线的解析表达式以及同步电机在cosj为定值时IM关于If的解析公式。利用计算机的高速运算能力可以迅速获得V形曲线。该方法可以推广到隐极同步电机。     

Control of dynamic overvoltages due to load rejection by static shunt compensation

A digital computer method used to evaluate the performance of a static shunt compensator as a device for controlling dynamic overvoltages caused by load rejection is presented. A typical system of a generating station connected to a load centre through an EHV transmission line with a static compensator at the load end is considered, and the envelopes of dynamic overvoltages following load rejection are evaluated. Detailed mathematical models incorporating the dynamics of a synchronous machine, transmission network and static shunt compensator are employed in the analysis. The static shunt compensator is shown to be an effective tool for controlling dynamic overvoltages. The application of this analysis for choosing an economic voltage rating of the surge arrestor is highlighted.     

抽水蓄能机组孤网运行稳定特性分析

由于抽水蓄能机组抽水调相转为抽水工况,后加负荷速度不可控,启停过程中负荷跃变剧烈,孤网期间容易影响电网频率稳定.为着力解决长期以来困扰海南电网"大机小网"下的频率稳定问题以及排查可能存在的安全稳定威胁,文章依据抽水蓄能机组同步机、水轮机及其调速器的数学模型,构建了水轮机调速器环节与同步机转子运动环节的动态反馈线性化模型.通过BPA仿真计算,研究了水轮机调速器动态对抽水蓄能机组的频率稳定性的影响.通过计算海南电网频率稳定性与机组功角稳定性,确定了抽水蓄能机组单机最大容量.该研究为未来海南电网稳定运行、抽水蓄能机组孤网运行提供了可靠的借鉴.     

同时带交流和整流负载的三相同步发电机系统的运行稳定性

参数匹配不当的同时带交流和整流负载的三相同步发电机系统会发生低频振荡而不能正常工作。为了对系统稳定运行的条件进行研究 ,在系统等效电路模型基础上 ,建立了该系统的线性化数学模型及相应的状态方程。使用劳斯判据得出了系统稳定运行的判据、直流侧等效动态电阻的计算公式和临界电阻的计算公式 ,揭示了系统“微变”稳定条件的物理实质。详细讨论了发电机参数、交轴稳定绕组及负载对系统运行稳定性的影响。实验与理论分析结果的对比说明了所建模型和分析方法的正确性     

负荷虚拟同步机惯性与阻尼自适应控制策略

虚拟同步机(VSM)技术通过模拟传统同步机转子惯性和系统阻尼,对电网提供惯性支撑。然而,阻尼与惯性的引入使得变换器的动态响应速度变慢,当变换器对输出功率进行主动调节时,无法快速、平稳地到达给定值。针对这一问题,提出一种惯性与阻尼自适应调节的负荷侧VSM优化控制策略。该控制策略通过在功率调节不同阶段,自主调节VSM的惯性J和阻尼D,实现对输出功率的优化控制。为了验证该控制策略的有效性,建立了VSM的MATLAB/Simulink模型,对其进行了仿真实验。仿真结果表明,与传统控制方法相比,基于该控制策略的同步机有功功率调节速度更快,调节过程中的波动和超调更小,具备更好的动态调节性能。     

船舶电站同步发电机状态反馈H∞调压器

船舶电力系统电压的稳定性主要取决于船舶电站同步发电机调压系统的响应特性.船舶电站同步发电机调压系统是一个非线性控制系统,为了分析系统的动态特性,首先建立同步发电机调压系统的非线性数学模型,然后以此为基础设计状态反馈H∞调压器.将H∞控制理论应用于同步发电机调压器的设计,把系统的性能要求转化为标准H∞控制问题,通过解Ri...