Decentralized stochastic adaptive control of interconnected systems

This paper considers the stochastic adaptive control problem for a class of large-scale systems formed by arbitrary interconnection of subsystems with unknown parameters and non-linearities. For the estimation of the unknown parameters of the local controllers, stochastic approximation algorithms are used. Conditions sufficient for global stability of the overall system are established. It is shown that the overall tracking error is bounded by a quantity depending on the size of interconnections.     

Formulation, computation and improvement of steady state security margins in power systems. Part II: Results

A steady state security margin for a particular operating point can be defined as the distance from this initial point to the secure operating limits of the system. Four of the most used steady state security margins are the power flow feasibility margin, the contingency feasibility margin, the load margin to voltage collapse, and the total transfer capability between system areas. This is the second part of a two part paper. Part I has proposed a novel framework of a general model able to formulate, compute and improve any steady state security margin. In Part II the performance of the general model is validated by solving a variety of practical situations in modern real power systems. Actual examples of the Spanish power system will be used for this purpose. The same computation and improvement algorithms outlined in Part I have been applied for the four security margins considered in the study, outlining the convenience of defining a general framework valid for the four of them. The general model is used here in Part II to compute and improve: (a) the power flow feasibility margin (assessing the influence of the reactive power generation limits in the Spanish power system), (b) the contingency feasibility margin (assessing the influence of transmission and generation capacity in maintaining a correct voltage profile), (c) the load margin to voltage collapse (assessing the location and quantity of loads that must be shed in order to be far away from voltage collapse) and (d) the total transfer capability (assessing the export import pattern of electric power between different areas of the Spanish system).     

Formulation, computation and improvement of steady state security margins in power systems. Part I: Theoretical framework

A steady state security margin for a particular operational point can be defined as the distance from this initial point to the secure operational limits of the system. Four of the most used steady state security margins are the power flow feasibility margin, the contingency feasibility margin, the load margin to voltage collapse, and the total transfer capability between system areas. A comprehensive literature survey has shown that these security margins have been studied separately. This fact has suggested to the authors the possibility of researching a common analysis framework valid for all of them. This is the first part of a two-part paper. In part I, a novel mathematical formulation valid to address the study of any steady state security margin is proposed. The developed general approach is presented in three steps: (a) formulation, (b) computation, and (c) improvement of security margins. In part II, the performance of the proposed approach when used to compute and improve the aforementioned steady security margins is illustrated through its application to the Spanish power system. Results denote that this approach can be a useful tool to solve a variety of practical situations in modern real power systems.     

Stability of the equilibria of adaptive systems with leakage estimator

We study the stability of the equilibria of the differential equations that describe an adaptive controller in closed loop with a linear time-invariant (LTI) undermodelled plant when the parameter update law is a leaky gradient, i.e. a s?-modified estimator. Hsu and Costa studied the full-order case and showed that under certain limiting conditions the resulting dynamic system has three, possibly unstable, equilibrium points. Here we provide a modest extension to that work by further characterizing the class of undermodelled LTI plants for which the equilibria exist and are (un)stable Interestingly enough, it is shown that the equilibria are stable iff a given compensator stabilizes the plant. This compensator is, up to the plant ‘steady state gain’, known to the designer.     

标准遗传算法的收敛性分析及其趋近稳态的速度估计

应用齐次Ｍｒｋｏｖ链仔细分析了标准遗传算法（ＳＧＡ）趋近于稳态的过程,给出其稳态分配的具体表示形式;同时得到了更广泛和严格意义上的与ＳＧＡ控制参数相联系的到达稳态的速度估计,其结果对于其他全局收敛ＧＡ的收敛性和收敛速度研究都有借鉴意义。     

Robust stability for singularly perturbed systems with structured state space uncertainties

This paper considers the robust stability of singularly perturbed systems with structured state space uncertainties. By making use of the Lyapunov stability criterion and combining it with the Lyapunov equations, a new approach for deciding a robust stability for uncertain linear singularly perturbed systems is presented. Based on the assumption that the reduced nominal system is stable, we also derive some sufficient conditions for robust stability. Some analytical methods and the Bellman–Gronwall inequality are used to investigate such sufficient conditions. In this paper, it is worth pointing out that we do not need to investigate both the slow system and the fast system by means of the singular perturbation methods because the proposed method is very direct. Furthermore, we only assume that the uncertainties are norm‐bounded. Therefore, the robust stability condition derived here is less conservative than those reported in the control literature. A numerical example is given to demonstrate the validity of our new results. © 2000 Scripta Technica, Electr Eng Jpn, 132(4): 62–72, 2000     

Input-output theory of high-gain adaptive stabilization of infinite-dimensional systems with non-linearities

This paper develops an input-output theory of high-gain adaptive stabilization of certain infinite-dimensional processes with actuator and sensor non-linearities. It is shown that there is a wide range of gain adaption rules achieving stability for the class of processes under consideration if proportional output feedback is used. The abstract input-output results are applied to retarded systems and Volterra integrodifferential systems. The paper shows that the scope of applicability of universal adaptive stabilization ideas extends far beyond finite-dimensional linear systems.     

具有非线性扰动的网络化随机系统鲁棒控制

针对具有非线性扰动的网络化随机系统的鲁棒控制问题,考虑到反馈控制环中由于实时通讯网络的存在会不可避免地出现网络诱导时延和数据丢失现象,建立了连续时间网络化随机系统模型.在此基础上,设计了状态反馈控制器,使得闭环系统最终均方有界.利用广义系统变换和Lyapunov-Krasovskii泛函方法,得到了闭环系统最终均方有界的充分条件,证明了理想的状态反馈控制器可以通过求解线性矩阵不等式得到.该方法可推广到以双线性随机系统为受控对象的网络化控制系统的镇定控制器设计中.     

On the steady state analysis of a current fed induction motor

Contents The performance equations of an induction motor operating on a current source inverter are derived using a stationary reference frame of two of the three phases. The equations are well suited for simulation of a current controlled inverter fed induction motor on a digital computer using well known numerical methods of integration. A method is presented for the steady state analysis via state transition signal flow graph. This method is found to offer several advantages over the methods available in the literature using state space techniques. The steady state solution of the equations can be used to show that the rotor flux varies sinusoidally and it induces a sinusoidal voltage in the stator phases accompanied with voltage spikes during commutation.

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Über das stationäre Verhalten eines Asynchronmotors mit eingeprägtem Strom

Übersicht Für einen Asynchronmotor, der über einen Umrichter mit eingeprägtem Strom arbeitet, werden die Gleichungen in einem auf zwei Strangachsen bezogenen Koordinatensystem aufgestellt. Diese sind für die Simulation des Motors unter Benutzung bekannter Integrationsmethoden auf einen Digitalrechner gut geeignet. Es wird eine Methode zur Untersuchung des stationären Zustands mit Hilfe von Signalflußdiagrammen vorgelegt. Diese Methode weist gegenüber der Darstellung im Zustandsraum einige Vorteile auf. Anhand der Lösungen wird gezeigt, daß der Fluß sich sinusförmig ändert und in den Ständersträngen sinusförmige Spannungen mit überlagerten Spitzen induziert.

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Nomenclature i _A,i _B,i _C Stator phase currents - i _a,i _b,i _c rotor phase currents - l _d D. C. link current - L _g mutual inductance between stator and rotor phases (L _m=3/2L _g) - L _s,L _r leakage inductance of stator and rotor windings per phase - L _s,L _r self inductances of stator and rotor windings - P pairs of poles - R _s,R _r stator and rotor resistances per phase - T _cl electromagnetic torque developed - u _A,u _B,u _C stator phase voltages - u _a,u _b,u _c rotor phase voltages - _A , _B , _C stator flux linkages - _a , _b , _c rotor flux linkages - 1–L _m ² /(L _s L _r)=leakage coefficient - electrical angle between the axes of the stator and rotor phases - d/dt=angular speed of the rotor     

Membership function shape and the dynamic behaviour of fuzzy systems

In this paper the influence of the shape of the membership functions on the dynamic behaviour of a fuzzy controlled system is investigated. Although several works on fuzzy logic have been presented in the literature, few efforts have been made to characterize the dynamic behaviour of a fuzzy system through the shape of the membership functions. A parametrization for a class of membership functions is introduced in this work, resulting in a variety of shapes. Various system steady state dynamics are analysed as a consequence of this change in shape and chaotic dynamics is shown to arise for some membership function shapes.     

直线感应电动机稳态运行特性的有限元分析

以一台容量5．5kW的直线感应电动机为例,在考虑纵向端部效应的情况下,将整个直线感应电动机模型作为求解域,采用有限元法对其磁场进行了数值计算。通过对磁场的分析,可以计算出直线感应电动机的运行特性。将理论计算结果与实验结果进行了比较,验证了计算方法的准确性。     

静态同步串联补偿器稳态特性分析与详细数学模型的建立

通过数学推导得出了静态同步串联补偿器（SSSC）的功率传输特性及包含交直流系统的详细数学模型。数学模型对SSSC的交流部分和直流部分分别进行分析和数学建模，并通过交、直流侧功率守恒将二者联系在一起。利用EMTDC提供的元件库，搭建了含单机无穷大系统及SSSC装置的仿真系统。SSSC装置包括二电平、六脉冲电压源逆变器及其SPWM脉冲发生回路。利用EMIDC中的控制模块构建了典型的PI控制回路，实现对线路潮流的实时控制。仿真结果验证了SSSC功率传输特性及其数学模型的正确性。     

带桥式交流器的凸极同步电机的稳态特性分析

本文给出了利用复数坐标变量系统解带桥式变流器的凸极同步电机稳态特性的计算方法,并对一台实际电机作了具体计算。计算波形和实验波形的一致性良好。文中还利用FFT对各电压及电流进行了诸波分析,并详细讨论了等效逆序电流的计算。最后,给出了计及谐波电流后的定子磁势。     

Modified algorithm of the revised simplex method applied to power system state estimation

A modification of the revised Simplex method applied to a weighted least-absolute-value state estimation is considered. A large basis matrix is replaced by a much smaller submatrix, so that memory requirements are considerably reduced. The algorithm is presented in detail, together with results of simulation studies which confirmed the good performance of the algorithm.     

永磁直线同步电机负载突变及稳态振荡特性

永磁直线同步电机(PMLSM)的负载突变时,电机的电流、速度、推力等参数都会发生很大的变化。基于电感矩阵的状态空间变量法分析电机的负载突变特性,很难考虑PMLSM磁路饱和、初级齿槽及初级铁芯有限长等因素。采用状态变量有限元法研究PMLSM负载突变特性,计算PMLSM的负载突变及稳态振荡特性。对计算结果进行分析,实验数据验证仿真结果,并给出合理解释。结果表明,磁阻力的端部分量是影响动子稳态运行速度振荡的主要因素;绕线电阻影响功角曲线,使电机可以工作在第一、第三象限。负载突变特性可为PMLSM的优化设计、控制策略实施、安全运行提供理论基础。     

Effects of load modelling on the behaviour of power systems

This paper describes the influence of the electrical load model on the behaviour of an electrical power system. Seven different load models have been selected and the impact of these models on four aspects of the behaviour of the network has been investigated. The investigation has been performed on the 220 and 110 kV FGO grid, which forms part of the Dutch high-voltage network. If, for a specific study, the nature of the load is unknown, it is recommended to use a load model in which the active and reactive parts are presented by a constant admittance.     

唯一稳态消谐法在中性点不接地系统铁磁谐振中的应用

唯一稳态消谐法是近年出现的消除非线性系统谐振新的分析方法.该方法的基本思想是如果非线性系统存在一个非谐振的正常解,并且该系统具有唯一的稳态,则此时对应的条件就是系统不发生谐振的条件.本文将这方法应用在消除中性点不接地电力系统的铁磁谐振中,以矩阵范数为工具,得到了相应的消谐条件.结果表明,消除谐振的条件可以用矩阵的范数条...     

Method for dynamic behaviour control of electric power systems

A statistical method that determines quality indices is presented. These indices give the regression relations for the dynamic behaviour of an electric power system as a function of some EPS scheme and regime parameters. The regression relations obtained are simple and allow a rapid and precise analysis and synthesis. The method is applied to solve an example of a real problem system.