Sharif Digital Repository

Background/Objectives: In this paper by utilizing frequency tracking electrical loads are shared on voltage source converters and then by applying a proposed-supplementary control system, frequency changes during changing electrical loads inside network is omitted. Methods/Statistical Analysis: Using decentralized control in Microgrids and sharing loads on power generation units respect to their nominal capacity are unavoidable approaches to have stable and operational network. Droop control in load sharing is known as practical and significant solution. In droop control, units output frequency, changes proportional to output active power that is not preferable. Simulation results in PSCAD... 

This paper considers the problem of stabilizing a class of linear time-invariant large-scale systems composed of a number of subsystems using several local dynamic output feedback controllers. For this problem, a sufficient condition on each closed-loop individual subsystem is derived under which the decentralized controller composed of the local controllers designed for individual subsystems, achieves stability for the overall system. This condition is used to convert the decentralized stabilization problem to a set of the H∞ disturbance rejection subproblems  

This paper considers the problem of stabilizing a class of linear time-invariant large-scale systems composed of a number of subsystems using several local dynamic output feedback controllers. For this problem, a sufficient condition on each closed-loop individual subsystem is derived under which the decentralized controller composed of the local controllers designed for individual subsystems, achieves stability for the overall system. This condition is used to convert the decentralized stabilization problem to a set of the H∞ disturbance rejection subproblems  

In this paper, decentralized control algorithms for cooperative multi-agent manipulation systems are developed. To control the positions of the agents and the exerted forces on the object in the presence of uncertainties in the dynamics of the agents, two different methods are considered. In the first approach, robust control of the system is proposed. Using the Lyapunov stability method, the convergence of the position errors to zero is demonstrated. Also a bound on the errors of the exerted forces is achieved which can be made small enough by choosing the appropriate estimated values for the physical parameters of the agents. In the second approach, adaptive control algorithm is proposed... 

In this paper a decentralized control scheme for multiple cooperative manipulators is developed to achieve the desired performance in motion and force tracking, in the presence of uncertainties in dynamic equations of the robots. To eliminate the effects of uncertainties in the closed-loop performance, a new adaptive control algorithm is proposed. Based on the Lyapunov stability method, it is proved that all the error signals in the closed-loop system which is compose of a robot, an observer and a controller asymptotically converge to zero. Also to avoid the difficulties of using velocity sensors within the cooperative system, an output feedback control scheme with a linear observer is used.... 

In this paper an adaptive fuzzy decentralized control algorithm for trajectory tracking of robot manipulators is developed. The proposed decentralized control algorithm allows the overall closed-loop system to be stabilized while making the tracking error to be uniformly ultimately bounded (UUB), without having any prior knowledge of the robot manipulator dynamics. The interconnections in the dynamic equations of each subsystem are considered with unknown nonlinear bounds. The adaptive fuzzy neural networks (AFNNs) are proposed to model the unknown nonlinear dynamics of the robots and the interconnection terms. Using Lyapunov method, the stability of the overall system is investigated. ©... 

This paper attempted to control a hybrid DC microgrid in islanded operation mode using decentralized power management strategies. Proposed adaptive I/V characteristic for hybrid photovoltaic (PV) and battery energy storage system (BESS) and wind turbine generator (WTG) adapts the distributed energy resources (DER) behavior independently in accordance with the load demand. Hence, the PV module can spend its maximum power on load demand and spend the extra power for charging the BESS, which will regulate DC bus voltage and maintain the power balance within the microgrid. When load demand is beyond the maximum generation power of PV unit, WTG will supply the energy shortage. The proposed... 

Decentralized controllers with integral action represent a large portion of multivariable controllers currently employed in the process industry. The integrity of these systems with respect to loop failures has been relatively well researched. In particular, important results have been found with respect to the relative gain array (RGA). However, less has been done on the treatment of the integrity of uncertain systems. This paper considers the integrity conditions of uncertain systems with norm-bounded uncertainties, and extends four existing integrity conditions to these uncertain systems. These are: integral stabilizable (IS), integral controllable (IC), integral controllable with... 

Multivariate ring-model description and the delay operator are used to represent LTI systems with delays in the states, inputs and outputs. By using the concept of μ-Decentralized Fixed Mode (μ-DFM) and generalized Nyquist criterion, it is demonstrated that the steady-state gain information yet remains the only information necessary to assess integral stabilizability (IS), integral controllability (IC), integral controllability with integrity (ICI) and decentralized integral controllability (DIC) of LTI time-delay systems. The conditions involve no approximation of the delay terms. Furthermore, it is demonstrated that a previous assumption on the existence of a stabilizing and stable... 

In this paper, decentralized control of formation of a special category of leaderfollower networks on bounded velocity trajectories is addressed. The network of the agents in this study is supposed to have a directed graph with a spanning tree rooted at the leader agent. Moreover, follower agents do not receive online or have offine velocity of the desired trajectory, such as in tracking problem of trajectories which are not predefined or when the total bandwidth is narrow. Furthermore, the leader does not receive any information from any agent and its control is fully centralized. In the present study, formation problem is considered a consensus problem. The controller is designed for... 

Increasing rate of renewable energy sources (RESs) integration in the distribution system and development of multi-microgrids (MMG) structures have changed the operational condition of power grids. In this context, the stochastic and intermittent nature of the RESs has increased the need for ramp up power to balance the supply and demand when electricity generation of these resources drops. Moreover, bulk power generation units, which conventionally have the possibility to provide flexibility ramp, would face lack of financial justification for expansion and operation in a system with high rate penetration of RESs. Therefore, distribution system operators (DSOs) should rely on local... 

The integrity of decentralized controllers with integral action, with respect to loop failures, has been researched relatively well. Important results have been found, with respect to the Relative Gain Array (RGA). However, less has been done on the treatment of the integrity of uncertain systems. This paper builds on the more-recent progress on the analysis of uncertain systems and presents new conditions for the integrity of closed-loop systems. The developed Integral Controllable (IC), Integral Controllable with Integrity (ICI), and Decentralized Integral Controllability (DIC) conditions are derived using a model of uncertainties that allows both unstructured and structured independent... 

A decentralized control scheme for multiple cooperative manipulators system is developed to achieve the desired performance in motion and force tracking in the presence of uncertainties in the dynamic equations of the robots. To reduce the effects of uncertainties in the closed-loop performance, a robust control algorithm using a robustifying term is proposed. Based on the Lyapunov stability method, it is proved that all the signals in the closed-loop, composed of a robot, an observer and a controller are uniformly ultimately bounded. Also to avoid the difficulties of using velocity sensors within the hand architecture an output feedback control scheme with a linear observer is used. © 2005...