Robust adaptive control for uncertain time‐delay systems

The problem of robust stabilization for uncertain dynamic time‐delay systems is considered. Firstly a class of time‐delay systems with uncertainties bounded by high‐order polynomials and unknown coefficients are considered. The corresponding controller is designed by employing adaptive method. It is shown that the controller designed can render the closed‐loop system uniformly ultimately bounded stable based on Lyapunov–Krasovskii method and Lyapunov stability theory. Then the proposed adaptive idea is applied to stabilizing a class of large‐scale time‐delay systems with strong interconnections. A decentralized feedback adaptive controller is designed which guarantees the closed‐loop large‐scale systems uniformly ultimately bounded stable. Finally, numerical examples are given to show the potential of the proposed techniques. Copyright © 2005 John Wiley & Sons, Ltd.     

一种包含不确定参数的暂态稳定分析方法

动态电力系统是一个非线性、多变量、强耦合的系统,由于大量参数的不确定,建立精确的模型比较困难。该文基于UUB(一致最终有界)定理,提出一种利用二次型的Lyapunov函数分析多机均匀阻尼经典模型中参数不确定性对暂态稳定影响的解析方法。通过比较某一运行方式下的计算指标与极限指标来判断该系统的参数偏差是否会引起暂态稳定性的变化。对两个算例进行了一系列仿真,结果表明该方法结果尽管保守,但简单、可靠、容易实现。     

Decentralized robust controller design for robots with torque saturation constraint

Decentralized robust tracking control problems for robots with control input amplitude limitation are investigated. The robust controller, proposed in our previous paper, is improved to avoid windup caused by amplitude limitation. To cope with the difficulties in calculating the controller parameters, a method based on evolutionary optimization is presented. Simulation results verify the effectiveness of the improved controller.     

A robust SMES controller design for stabilization of inter-area oscillations based on wide area synchronized phasor measurements

This paper proposes a robust power controller design of superconducting magnetic energy storage (SMES) based on wide area synchronized phasor measurement units (PMUs) for stabilization of inter-area oscillation. The structure of active and reactive power controllers of SMES is the first-order lead/lag compensator. Assuming multiple PMUs are located in an interconnected power system, the steady state phasor data are obtained by applying the small load perturbation. Using the phasor data, the simplified oscillation model (SOM) included with SMES power controllers can be identified and applied to estimate the dominant inter-area oscillation modes. In the robust control design, unstructured system uncertainties such as various operating conditions, system parameters variation, etc., are represented by the inverse additive perturbation and included in the SOM. To enhance the system robust stability margin, the optimization of SMES control parameters is solved by genetic algorithm in the SOM. Simulation studies in the West Japan 6-machine power system confirm that the robustness of the proposed SMES is much superior to the conventional SMES against various operating conditions and fault locations.     

Decentralized adaptive controller for synchronization of nonlinear dynamical heterogeneous networks

For a network of interconnected nonlinear dynamical systems, an adaptive leader–follower output feedback synchronization problem is considered. The proposed structure of decentralized controller and adaptation algorithm is based on speed gradient and passivity. Sufficient conditions of synchronization for one class of heterogeneous networks are established. An example of synchronization of the network of nonidentical Chua systems is analyzed. The main contribution of the paper is adaptive controller design and analysis under conditions of incomplete measurements, incomplete control, and uncertainty. Copyright © 2012 John Wiley & Sons, Ltd.     

Decentralized robust adaptive-output feedback controller for power system load frequency control

In this paper, a new model reference-decentralized robust adaptive-output feedback controller is proposed for the load frequency control (LFC) of large-scale power systems with unknown parameters. This control strategy requires only local input–output data and can follow random changes in the operating conditions. The controller is designed such that the trajectory errors and the control gains of each area remain uniformly bounded. In the proposed method, firstly an adaptive observer is designed to estimate the state variables and system parameters using local data only. Then a locally linear combination of the estimated states and the model reference states are used to design a robust adaptive-output feedback controller for each area. Simulation results for a three-area power system show that the proposed controller achieves good performance even in the presence of plant parameter changes and system non-linearities. Received: 18 October 2001/Accepted: 24 October 2001     

基于免疫原理的自适应模糊控制器优化设计

利用免疫系统的克隆选择原理设计了全局搜索优化算法和局部搜索优化算法，并提出了一种时变对象的模糊控制器参数自整定方案。该方案利用全局优化算法离线组合优化标称参数下的控制器，对象发生变化后，利用局部优化算法在线优化，可快速获得新的控制器参数，以实现自适应控制。仿真结果表明，该控制系统在被控对象参数变化的情况下，仍具有良好的控制性能，能够对一类时变对象实施高精度控制，具有较大的工程应用价值。     

Modular design of adaptive robust controller for strict-feedback stochastic nonlinear systems

A modular approach of the estimation-based design in adaptive linear control systems has been extended to the adaptive robust control of strict-feedback stochastic nonlinear systems with additive standard Wiener noises and constant unknown parameters. By using It?’s differentiation rule, nonlinear damping and adaptive Backstepping procedure, the input-to-state stable controller of global stabilization in probability is developed, which guarantees that system states are bounded and the system has a robust stabilization. According to Swapping technique, we develop two filters and convert dynamic parametric models into static ones to which the gradient update law is designed. Transient performance of the system is estimated by the norm of error. Results of simulation show the effectiveness of the control algorithms. The modular design, which has a concise hierarchy, is more flexible and versatile than a Lyapunov-based algorithm. __________ Translated from Journal of University of Science and Technology of China, 2004, 34(4): 495–503 (in Chinese)     

A robust centralized SMES controller design based on WAMS considering system and communication delay uncertainties

It is well known that the communication delay due to the phasor measurement in wide area monitoring system (WAMS) as well as various system operating conditions such as heavy line flows and unpredictable network structures, may deteriorate the wide-area stabilizing control effect. To overcome this problem, the inverse input and output multiplicative model is proposed to represent unstructured uncertainties due to system operations and communication delay in the robust centralized damping controller design of superconducting magnetic energy storage (SMES) based on WAMS. The structure of centralized controller for SMES is the practical 1st-order lead/lag compensator. To automatically tune the control parameters, the optimization problem based on the enhancement of damping performance and system robust stability margin is achieved by particle swarm optimization. Simulation studies in the West Japan six-area interconnected system confirm that the proposed robust SMES centralized controller is superior to the conventional SMES centralized controller in terms of damping performance and robustness against system and time delay uncertainties.     

基于Dijkstra算法的配电网孤岛划分

针对传统孤岛划分方法存在的没有合理利用电网拓扑结构、算法搜索性能差等问题,提出了一种基于Dijkstra算法的配电网孤岛划分方法。首先,采用Dijkstra算法得出DG到重要负荷的最短路径,在满足孤岛划分约束条件的情况下,将含有重要负荷的路径划分入孤岛。然后,根据所得孤岛的邻接关系和负荷节点优先级,在孤岛安全稳定运行的前提下,逐步将更多的负荷划入孤岛。该方法能够充分发挥DG的供电能力,并且具有较好的搜索能力,不仅可以在最大程度上保证重要负荷的供电,而且能够有效计及联络开关的作用。最后,通过算例验证了算法可以有效地处理配电网孤岛划分问题。     

Optimal robust adaptive fuzzy synergetic power system stabilizer design

A new particle swarm optimized robust indirect adaptive power system stabilizer is developed based on recently developed synergetic control methodology. Fuzzy systems are used in an adaptive scheme to approximate the system using a nonlinear model while synergetic control guarantees robustness and the use of a chatter free continuous control law which makes the controller easy to implement. In addition the controller parameters are optimized using PSO approach. Simulation of severe operating conditions of a power system is conducted to validate the effectiveness of the proposed approach while stability is guaranteed via Lyapunov synthesis.     

A study on robust adaptive modulation controller for TCSC based on COI signal in interconnected power systems

This paper proposes a novel robust adaptive modulation controller (RAMC) for thyristor controlled series capacitor (TCSC) in interconnected power systems to damp low frequency oscillation. The main idea of the controller is to drive the area centers of inertia (COI) to a stable equilibrium point and keep system synchronization. COI-coordinate-based model is derived first. Then RAMC for TCSC is derived using back-stepping method with COI dynamic signals from WAMS. The new controller performance is tested through a three-area power system and the simulation results show clearly that the new controller using COI signals has superior performance as compared with the conventional controller.     

复杂网络的社团发现方法在电网分区识别中的应用研究

电网传统分区方案主要依据地理和行政区域,这样的分区往往对网络结构没有太多关注,而引发大停电事故又多源自分区联络线。复杂网络理论中的社团发现利用节点之间的连接关系来识别网络拓扑分区,与电网的分区结构极为相似。简介了社团结构及其模块化Q函数的概念及其评价指标,提出了基于社团发现的电网分区方法。利用电网潮流和阻抗参数作为边的权重建立四种不同的加权复杂网络模型,引入Louvain改进层次算法,并结合实际电网的特点对分区流程进行了实用化改进。基于标准的IEEE39、118、300节点电网及南方电网,分析了不同模型下     

基于自适应权重Voronoi图的配电网供电分区方法

在研究常规Voronoi图应用的基础上,针对配电网负荷分布不均匀的情况,提出了基于自适应权重Voronoi图的配电网供电分区方法。该方法按照道路、河流等自然障碍将供电区域划分成若干网格,以变电站为生成元向四周扩散。考虑变电站的负载能力、供电距离、地理障碍和网格归属地等因素,动态调整V图生成元在不同方向上的扩算速度,使得供电分区的结果更加科学合理。为了保证分区结果与城市规划的协调性,体现配电网发展的延续性,引入了虚拟元的概念,解决分区内无电源点问题。最后经实际算例验证,表明该方法具有一定有效性和合理性。     

A robust adaptive LQG/LTR TCSC controller applied to damp power system oscillations

This paper investigates the use of self-tuning Linear Quadratic Gaussian control with Loop Transfer Recovery (LQG/LTR), applied in Thyristor Controlled Series Capacitors (TCSC) installed in interconnected power systems. The proposed robust adaptive controller can improve power system stability margins, damping properly the system's dominant electromechanical modes. Although this TCSC controller is designed mainly to identify and damp inter-area modes, it does not affect negatively the local modes damping, therefore enhancing the overall system performance. The proposed controller properties can be verified using non-linear simulations for a four-machine power system, in different operation conditions.     

A robust model-free controller for a three-phase grid-connected photovoltaic system based on ultra-local model

In this paper, a robust model-free controller for a grid-connected photovoltaic (PV) system is designed. The system consists of a PV generator connected to a three-phase grid by a DC/AC converter. The control objectives of the overall system are to extract maximum power from the PV source, to control reactive power exchange and to improve the quality of the current injected into the grid. The model-free control technique is based on the use of an ultra-local model instead of the dynamic model of the overall system. The local model is continuously updated based on a numerical differentiator using only the input–output behavior of the controlled system. The model-free controller consists of a classical feedback controller and a compensator for the effects of internal parameter changes and external disturbances. Simulation results illustrate the efficiency of the controller for grid-connected PV systems.     

Decentralized load frequency controller for a multi-area interconnected power system

This paper proposes a control scheme for the load frequency control (LFC) problem of multi-area power systems. These systems are treated as interconnected dynamical systems. In the design of the proposed controller, each local area network is overlapped with states representing the interconnections with the other local area networks in the global system. Then, a decentralized control scheme is developed as function of the local area state variables and those resulting from the overlapped states which represent an approximation of the interconnection variables. The proposed controller guarantees the asymptotic stability of the overall closed loop system.The simulation results indicate that the proposed control scheme works well. In addition, they show that the controlled system is robust to changes in the parameters of the power system and to bounded input disturbances acting on the system. Moreover, the simulation results show that the controlled system behaves well even when there is a maximum limit on the rate of change in power generation.     

基于Riccati法的舰船电力系统鲁棒励磁控制研究

介绍了鲁棒控制器设计的Riccati方法，建立了单台发电机工作的典型工况下舰船电力系统的数学模型，并按鲁棒控制理论对状态反馈控制进行了研究。仿真研究取得了较为满意的结果。     

基于启发式规则的配电网孤岛划分算法

随着分布式电源(Distributed Generation, DG)的大量接入电网,孤岛运行成为一种提高供电可靠性的重要方式,合理地划分孤岛具有重要意义。首先,针对配电网的特点,构建了平均层数和平均度值两个目标函数。然后,根据孤岛划分的多目标优化问题,提出了支路和节点优先级的确定方法。在此基础上,以支路和节点优先级作为启发式规则,提出了一种基于启发式规则的配电网孤岛划分算法。该算法以DG节点或以该DG节点形成的孤岛为根,采取"搜索+调整"的思路进行求解。最后,通过仿真算例验证了该算法可以有效计及联络开关、负荷的重要程度、负荷的可控程度、节点度值、节点层数和负荷量大小的因素,能够很好地解决孤岛划分问题。     

Decentralized adaptive robust stabilization of uncertain interconnected time‐delay systems

This paper considers the problem of decentralized adaptive robust stabilization of a class of interconnected time‐delay systems with arbitrarily bounded matched but limitedly bounded unmatched uncertainties. A new class of decentralized adaptive controllers based on Lyapunov–Krasovskii functional is proposed that guarantees bounded stability of the system and ensures nonfragileness of the controller to perturbations in its nonadaptive gain factor. The existence of such controllers is formulated in the LMI framework besides being presented using the Algebraic Riccati Equations. A numerical example is considered to illustrate the applicability and effectiveness of the proposed controller. Copyright © 2011 John Wiley & Sons, Ltd.