Impulsive consensus for complex dynamical networks with nonidentical nodes and coupling time-delays

This paper investigates the problem of global consensus between a complex dynamical network (CDN) and a known goal signal by designing an impulsive consensus control scheme. The dynamical network is complex with respect to the uncertainties, nonidentical nodes, and coupling time-delays. The goal signal can be a measurable vector function or a solution of a dynamical system. By utilizing the Lyapunov function and Lyapunov-Krasovskii functional methods, robust global exponential stability criteria are derived for the error system, under which global exponential impulsive consensus is achieved for the CDN. These criteria are expressed in terms of linear matrix inequalities (LMIs) and algebraic inequalities. Thus, the impulsive controller can be easily designed by solving the derived inequalities. Meanwhile, the estimations of the consensus rate for global exponential consensus are also obtained. Two examples with numerical simulations are worked out for illustration. © 2011 Society for Industrial and Applied Mathematics.published_or_final_versio

First and last and always: Streetwork as a methodology for radical community social work practice.

This conceptual paper aims to introduce and explore the practice of social streetwork. Streetwork is located as a historical professional discourse that has contemporary relevance fora rapidly changing and globalised world. Streetwork as a practice discourse occurs across a range of community based helping professions including social work, youth work and community work. The social work profession is increasingly becoming clinical and situated within statutory organisations placing a greater emphasis on outcome based targets, rather than building relationships; and as a result of austerity, traditional youth workers are becoming invisible, often moving into statutory education settings and complex needs welfare agencies. This paper will argue that for the broad helping professions to remain relevant we must engage with vulnerable and complex populations where we find them: at a street level - promoting a direct practice of social justice at a micro level. Within this discussion, we will define and explore a streetwork approach by examining the methodologies and objectives of street work practice. We will argue that by keeping to its origins of using informal and non-formal education as its primary tools, street work as an intervention works to combat poverty, social exclusion and discrimination. The paper articulates a foundation for practice based on the promotion of low threshold interventions with complex and hard to reach social populations. One of the key themes we will explore is how to locate streetwork practice as a form of social support, accompaniment and as a tool for promoting social inclusion and social democracy

Exponential Synchronization of Complex Delayed Dynamical Networks With Switching Topology

This paper studies the local and global exponential synchronization of a complex dynamical network with switching topology and time-varying coupling delays. By using stability theory of switched systems and the network topology, the synchronization of such a network under some special switching signals is investigated. Firstly, under the assumption that all subnetworks are self-synchronizing, a delay-dependent sufficient condition is given in terms of linear matrix inequalities, which guarantees the solvability of the local synchronization problem under an average dwell time scheme. Then this result is extended to the situation that not all subnetworks are self-synchronizing. For the latter case, in addition to average dwell time, an extra condition on the ratio of the total activation time of self-synchronizing and nonsynchronizing subnetworks is needed to achieve synchronization of the entire switched network. The global synchronization of a network whose isolate dynamics is of a particular form is also studied. Three different examples of delayed dynamical networks with switching topology are given, which demonstrate the effectiveness of obtained results. © 2006 IEEE.published_or_final_versio

Distributed load-side frequency regulation for power systems

This paper studies frequency control of power systems by coordinating generation-side control and load-side control with nonlinear network-preserving models. A distributed consensus-based controller is designed for each bus in the transmission network. The total power imbalance of the system is discovered periodically by a distributed consensus mechanism, and then compensated by both generators and controllable loads accordingly. It is shown in simulation studies that the proposed method can achieve frequency regulation more effectively than the traditional automatic generation control (AGC) and reduce the needed system spinning reserve significantly. The impact of renewables on the system frequency under the designed control method is also discussed systematically in this paper.postprin

Network-Based Analysis of Small-Disturbance Angle Stability of Power Systems

This paper investigates small-disturbance angle stability of power systems with emphasis on the role of power network topology, which sheds new light on the instability mechanism. We introduce the concepts of active power flow graph and critical lines. It is shown that the inertia of the Laplacian matrix of this graph provides information on the stability and type of an equilibrium point. Then, the instability mechanism is elaborated from the impact of critical lines on the inertia of the Laplacian matrix. A stability criterion in terms of a critical line-based matrix is established. This criterion is a necessary and sufficient condition to judge the stability and type of an equilibrium point. It includes the existing results in the literature and applies to the unsolved cases where the critical lines exist but do not form cutsets. Moreover, we introduce the concept of equivalent weight between a pair of buses. Another stability criterion in terms of the equivalent weight is developed, from which the small-disturbance instability can be interpreted as the “electrical antagonism” between some buses in the power network resulting from the critical lines. The equivalent weight can also be used as a stability index and provides guidance for system operation. The obtained results are illustrated by numerical simulations.postprin

Cooperative output regulation of multi-agent systems coupled by dynamic edges

This paper investigates a new class of linear multi-agent systems, in which nodes are coupled by dynamic edges in the sense that each edge has a dynamic system attached. The outputs of the edge dynamic systems combine to form the external input of the node dynamic system, which is called neighboring input; while the outputs of the node dynamic systems are inputs of the edge dynamic systems that therefore cannot be directly controlled. Distributed controllers for nodes are presented to realize output synchronization and output cooperation. Output cooperation makes the outputs of nodes realize some cooperation that here is specified as making the neighboring input track a predefined trajectory. The controllers depending on local state and neighboring inputs are designed by combining the feedback passivity theory and the internal model principle. A simulation example on the cooperated current control of an electrical network illustrates the potential applications of the analytic results.preprin

Synchronization of dynamical networks with nonidentical nodes: Criteria and control

This paper presents a framework for global synchronization of dynamical networks with nonidentical nodes. Several criteria for synchronization are given using free matrices for both cases of synchronizing to a common equilibrium solution of all isolated nodes and synchronizing to the average state trajectory. These criteria can be viewed as generalizations of the master stability function method for local synchronization of networks with identical nodes to the case of nonidentical nodes. The controlled synchronization problem is also studied. The control action, which is subject to certain constraints, is viewed as reorganization of the connection topology of the network. Synchronizability conditions via control are put forward. The synchronizing controllers can be obtained by solving an optimization problem.published_or_final_versio

Incremental-dissipativity-based output synchronization of dynamical networks with switching topology

This paper studies asymptotic output synchronization for a class of dynamical networks with switching topology whose node dynamics are characterized by a quadratic form of incremental-dissipativity. The output synchronization problem of the switched network is first converted into a set stability analysis of a nonlinear dissipative system with a particular selection of input-output pair, which is related to special features of interconnected incremental-dissipative systems. Then, synchronization by designing switching among subnetworks, where none of them is self-synchronizing, is investigated by using the single Lyapunov function method. Algebraic synchronization criteria are established, and the results are applied to investigate synchronization of coupled biochemical oscillators. © 2014 IEEE.published_or_final_versio

Aggregated effect of demand response on performance of future grid scenarios

Session 32 - Future power system infrastructure: no. 459750Conference Theme: Towards Future Power Systems and Emerging TechnologiesThe existing future grid (FG) feasibility studies have mostly considered simple balancing, but largely neglected network related issues and the effect of demand response (DR) for modelling nett future demand. This paper studies the effect of DR on performance of the Australian National Electricity Market in 2020 with the increased penetration of renewable energy sources (RESs). The demand model integrates the aggregated effect of DR in a simplified representation of the effect of market/dispatch processes aiming at minimising the overall cost of supplying electrical energy. The conventional demand model in the optimisation formulation is augmented by including the aggregated effect of numerous price anticipating users equipped with rooftop photovoltaic (PV)-storage systems. Simulation results show that increasing penetration of DR improves loadability and damping of the system with the increased penetration of RESs.postprin

Passivity-based output synchronization of dynamical networks with non-identical nodes

Article no. 5717720Output synchronization of dynamical networks with non-identical nodes is studied using the passivity property. A synchronization criterion is developed for networks with general outer coupling topologies which need to be neither symmetric nor have the zero-row-sum property. When the passivity property cannot give synchronization for a single outer coupling topology, the problem of how to achieve synchronization by switching among several outer coupling topologies is studied. Synchronization conditions by switching among these topologies are presented and an output-dependent switching law is designed. In particular, it is shown that synchronizability can be checked by verifying if a certain nonlinear programming problem has no feasible solution or has a negative maximum. ©2010 IEEE.published_or_final_versio