A simplified and generalized dynamic simulation of multi-terminal HVDC transmission system

Multi-terminal HVDC transmission systems have a large potential for applications in future power systems. One of the prime requirements of planning-stage investigations and in-operation investigations on the multi-terminal schemes is to have a simplified, dynamic model using a digital computer. One such generalized digital computer program developed, is reported here. The program includes frequency (damping) controllers, power controllers, constant current controllers, limiting nonlinearities, communication delay and central current co-ordinator it can deal with any number of converters connected in any parallel system configuration namely mesh, tapped or a combination of them both. A few case studies are included to demonstrate the ability of the program.     

Port-Hamiltonian based Optimal Power Flow algorithm for multi-terminal DC networks

In this paper an algorithm for solving the Optimal Power Flow problem for multi-terminal DC networks based on the gradient method is proposed. The aim is seeking the optimal point subject to voltage, current and power constraints. The algorithm is described by a continuous-time port-Hamiltonian model, and the inequality constrains are included by the use of barrier functions. The dynamics of the algorithm is studied and stability conditions are obtained. Finally, the method is used for the offshore wind integration grid in the North Sea and the interconnection with the network dynamics is tested by means of numerical simulations.     

布尔控制网络的输出稳定与镇定

矩阵的半张量积是将逻辑变量转化为向量研究的主要工具.本文利用半张量积把逻辑控制系统表示为离散时间仿射线性系统,在逻辑系统的状态空间框架下研究了以布尔控制网络为代表的逻辑动态系统的输出稳定与镇定.首先给出布尔网络输出稳定的定义,研究了布尔网络输出稳定的充要条件;其次讨论了布尔控制网络的输出镇定,分别得到了布尔控制网络由常值输入变量、自由控制序列、状态反馈控制序列输出镇定的条件.本文讨论的系统输出稳定与镇定是(部分)变量稳定与镇定的推广.     

Smart control techniques for design of TCSC and PSS for stability enhancement of dynamical power system

This paper deals with the simultaneous application of thyristor controlled series capacitor based damping controller and power system stabilizer for stability improvement of dynamic power system. The adaptive neuro-fuzzy inference system and Levenberg–Marquardt artificial neural network algorithm are used to develop the control strategy for thyristor controlled series capacitor based damping controller and power system stabilizer. The power system stabilizer generates appropriate supplementary control signal to an excitation system of synchronous generator to damp the frequency oscillations and improves the performance of the power system dynamic. The performance of power system affected due to the system configuration and load variation. In order to achieve the appreciable damping, the series capacitor is suggested in addition to the power system stabilizer. Nonlinear simulations of single machine infinite bus system are carried out using the individual application of power system stabilizer and simultaneous application of power system stabilizer and thyristor controlled series capacitor. The comparison analysis between conventional and smart control strategies based controllers is demonstrated. Single machine infinite bus system is tested under various operating conditions and disturbances to show the effectiveness of proposed control schemes.     

Exponential stability of genetic regulatory networks with mixed delays by periodically intermittent control

This paper investigates the exponential stability for a class of mixed delayed genetic regulatory networks by periodically intermittent control, mixed delays here include time-varying delays and finite distributed delays. Some sufficient criteria for exponential stabilization are derived by using mathematical induction methods and the analysis techniques. Finally, an example is presented to demonstrate the effectiveness of the theoretical results.     

动态网络的稳定性与分布控制研究

针对分散控制无法实现子系统之间的信息交换，将分布式控制应用于网络化系统，以期实现子系统之间的信息交换和提高网络的性能．利用Lyapunov函数法，分别给出了在传统分散控制和网络分布式控制下的整个网络化系统稳定性的判据；给出了可容许的最大时滞的优化算法．将所得到的理论结果，结合到一个简单的网络化系统，进行数值仿真．结果表明，与传统分散控制相比较，网络分布式控制更能提高整个网络化系统稳定性的收敛速度．     

网络控制系统中的稳定性研究

网络控制系统中由于通讯网络的引入产生了不确定的网络延时、数据包丢失以及数据包时序错乱等问题，这些问题严重影响了系统的稳定性能甚至引起了系统的不稳定。为了保证系统的稳定性应根据网络控制系统中出现的时延问题设计控制器，本文针对线性和非线性控制对象提出了控制器模型。     

无线Ad Hoc网络中的功率控制问题

分析了Adhoe网络中节点的能量消费模式,详细论述了几种MAC层的功率控制技术和网络层具有能量意识的路由的主要度量准则,并提出了一些有前景的研究方法。     

Power control and capacity of spread spectrum wireless networks

Transmit power control is a central technique for resource allocation and interference management in spread-spectrum wireless networks. With the increasing popularity of spread-spectrum as a multiple access technique, there has been significant research in the area in recent years. While power control has been considered traditionally as a means to counteract the harmful effect of channel fading, the more general emerging view is that it is a flexible mechanism to provide quality of service to individual users. In this paper, we will review the main threads of ideas and results in the recent development of this area, with a bias towards issues that have been the focus of our own research. For different receivers of varying complexity, we study both questions about optimal power control as well as the problem of characterizing the resulting network capacity. Although spread-spectrum communications has been traditionally viewed as a physical-layer subject, we argue that by suitable abstraction, many control and optimization problems with interesting structure can be formulated at the network layer.     

伺服系统的恒稳定控制

分析了伺服系统稳定控制的实质,结合神经元和模糊控制设计了恒稳定控制方案,仿真结果验证了其有效性。     

火电厂多代理控制系统

针对火电厂非线性、多变量和多控制目标的特点,设计了一个火电厂多代理控制系统(PPMACS).在PP MACS中,前馈控制代理(FFCAs)采用神经模糊系统进行决策,反馈控制代理(FBCAs)采用基于遗传算法的模糊系统进行决策.优化任务分解代理(OTDAs)通过一个优化代理和一个分解代理来进行多目标优化分解PPMACS的任务.协调代理根据运行条件协调PPMACS的各个代理.仿真结果显示了火电厂多代理控制系统能够实现火电单元机组的多目标运行和大范围负荷跟踪.神经网络、模糊逻辑和遗传算法是PPMACS中的智能代理进行决策的有效工具.     

一种增强任务关键无线网络可信性的消息调度策略

任务关键无线网络面临实时和安全等可信因素的挑战,而已有的消息调度算法忽略了安全因素。提出一种安全感知的实时调度算法(SAMS)。在不违背关键消息的实时约束和安全约束的前提下,该算法能最大化提升系统的安全服务质量。仿真结果显示SAMS的有效性和健壮性。     

Eventual stability of an adaptive control system

The eventual stability of the adaptive scheme reported in [1] is proved by appealing to a theorem due to LaSalle and Rath [2].     

Algebraic aspects of linear control system stability

After formulating the problem of linear control system stability in very general terms, the problem is resolved by 1) establishing a necessary and sufficient condition for stability, 2) exploring in some detail the nature of this condition, and 3) developing a parametric characterization of all controllers which stabilize a given plant. The problem formulation is based on a ring theoretic setting for linear systems, and is distinguished by the use of a novel control system configuration. Any interconnection of two distinct systems can be represented in terms of this configuration while preserving the distinction between the two systems. Furthermore, no other configuration has this property. Several benefits and extensions are accrued as a result of using this configuration. First, a completely general, yet physically meaningful problem formulation results. Consequently, state-space and operator theoretic approaches to linear control system stability are thoroughly reconciled. This reconciliation embraces continuous-time as well as discrete-time systems, lumped as well as distributed systems, and 1-D as well asn-D systems. Second, the controller parametrization affords four degrees-of-freedom, two more than any existing parametrization. The additional degrees-of-freedom make explicit the design opportunity associated with controller implementation, and thus determine several important control system characteristics. This result is expected to provide a theoretical basis for the development of comprehensive control system design methodologies, wherein design considerations related to controller implementation are addressed.     

An improved Backstepping technique using sliding mode control for transient stability enhancement and voltage regulation of SMIB power system

The problem of transient stability and voltage regulation for a single machine infinite bus (SMIB) system is addressed in this paper. An improved Backstepping design method for transient stability enhancement and voltage regulation of power systems is discussed beginning with the classical Backstepping to designing the nonlinear excitation control of synchronous generator. Then a more refined version of this technique will be suggested incorporating the sliding mode control to enhance voltage regulation and transient stability. The proposed method is based on a standard third-order model of a synchronous generator connected to the grid (SMIB system). It is basically implemented on the excitation side of the synchronous generator and compared to the classical Backstepping controller as well as the conventional controllers which are the automatic voltage regulator and the power system stabiliser. Simulation results prove the effectiveness of the proposed method which ameliorates to a great extent the transient stability compared to the other methods.     

时滞控制神经网络的稳定性和Turing斑图结构

本文讨论了一类时滞反应扩散神经网络模型.利用时滞来控制系统的稳定性、分岔和Turing斑图.研究结果表明,在一定条件下,时滞不仅能影响系统的稳定性和周期震荡性,还能影响系统的Turing不稳定性.数值模拟验证了理论分析的正确性,同时还说明了时滞能改变斑图的结构.     

Access control system for distributed computing networks

The architecture of access control system for user jobs access to computational resources of grid distributed computing networks, which provides protection of data being processed against threats of exceeding user privileges, is presented. The developed system is compared to the available analogues, and the results of efficiency assessment of performance of the developed system are discussed.     

Power grasp force distribution control using artificial neural networks

In this article, methods for force distribution control of power grasp are developed. A power grasp is characterized by multiple points of contact between the object grasped and the surfaces of the fingers and palm. The grasp is highly stable because of form closure. However, modeling power grasps is difficult because of the resulting closed kinematic structure and the complexity of multiple contacts. The first method used to obtain the desired force distribution is based on linear programming. In particular, a model of the DIGITS grasping system, under development at The Ohio State University, is used, and constraint equations are formulated for force balance and actuator torque limits. Supervisory control of the desired forces at the contacts is achieved by prescribing a desired clinch level. The objective function is designed to achieve the desired clinch level, except in cases where the specified force is inadequate to stably hold the object. Although this method yields the desired force distribution, a second method based on artificial neural networks (ANNs) is developed to achieve constant-time solutions. Linear programming solutions are used to generate training data for a set of ANNs. Two techniques, modular networks and adaptive slopes, are also developed and employed in the training to improve the training time and accuracy of the ANNs. The results show that the ANNs learn the appropriate nonlinear mapping for the force distribution and provide stable grasp over a wide range of object sizes and clinch levels.     

Almost sure exponential stability of stochastic fluid networks with nonlinear control

Due to the objective of controlling fluid flows, fluid networks are high-order nonlinear stochastic systems in essential. Taking the nonlinearities in pressure drop of fan branch, measurement error of inertia coefficients, and random factors into consideration, this paper presents a stochastic fluid networks model described by Itô stochastic differential equations. As drift term of the stochastic fluid networks does not satisfy the linear growth condition, the almost sure exponential stability cannot get from the moment exponential stability. We directly investigate the almost sure exponential stability of the tracking and regulation problems for fluid networks under decentralised and adaptive control. It shows that the fluid flows in all branches can reach their reference values if we set controller only in links of the networks. We illustrate the results with two examples.