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As massively multiuser virtual environments (MMVEs) expand in terms of size and user population, they tend toward using P2P architectures as a way to provide scalability without the need for large centralized resources. Distributed hash table (DHT)-based networks have been introduced as a promising option for overlay-based distributed massively multiuser virtual environment applications. However, overlay latency stretch seriously affects MMVE performance where QoS is crucial for real-time user collaboration. This work includes a series of efforts in the alleviation of such undesired latency. Our approach to latency mitigation consists of two phases. First, we propose a position-based ID... 

As massively multiuser virtual environments (MMVEs) expand in terms of size and user population, they tend toward using P2P architectures as a way to provide scalability without the need for large centralized resources. Distributed hash table (DHT)-based networks have been introduced as a promising option for overlay-based distributed massively multiuser virtual environment applications. However, overlay latency stretch seriously affects MMVE performance where QoS is crucial for real-time user collaboration. This work includes a series of efforts in the alleviation of such undesired latency. Our approach to latency mitigation consists of two phases. First, we propose a position-based ID... 

Presence of energy hubs in the future vision of energy networks creates a great opportunity for system planners and operators to move towards more efficient systems. The role of energy hubs as the intermediate in multi-carrier energy (MCE) systems calls for a generic framework to study the new upcoming technical as well as economical effects on the system performance. In response, this paper attempts to develop a general optimization and modeling framework for coupled power flow studies on different energy infrastructures. This, as a large-scale nonlinear problem, is approached through a robust optimization technique, i.e., multi-agent genetic algorithm (MAGA). The proposed procedure... 

In this paper, Bat Algorithm is proposed to solve the Optimal Power Flow (OPF) problem. The approach employs a Meta heuristic optimization algorithm called bat optimization algorithm to determine the optimal settings of control variables of OPF problem. The performance of proposed method examined on the IEEE 9, 14, 30 and 57-buses test systems with fuel cost minimization as the objective function. The numerical results are compared to those of Particle Swarm Optimization (PSO), Harmony Search (HS) and Cuckoo algorithms. Simulation results obtained from the proposed approach demonstrate that this method provide effective and robust high-quality answer for the OPF problem. © 2016 IEEE  

This study assesses the management of reactive power generation to improve the voltage stability margin using modal analysis technique. The simulation results show that after the optimal reactive power re-scheduling, the voltage stability margin of the system is improved and the active/reactive power losses are decreased. Improving the voltage stability margin of power system without adding new VAR (Volt Ampere Reactive) sources and changing the active power dispatch, is the most important advantage of proposed method. © 2009 Asian Network for Scientific Information  

In this paper, we present a decentralized algorithm that computes minimum cost QoS flow subgraphs in network coded multicast networks. These subgraphs are minimum cost solutions that also satisfy user-specified QoS constraints, specifically handling elastic rate and delay demands. Although earlier network coding algorithms in this area have only demonstrated QoS improvements, the proposed QoS network coding is clearly different in the sense that it guarantees that given QoS constraints are met over the network. ©2008 IEEE  

This paper presents a modified particle swarm optimization (MPSO) algorithm for solving the optimal power flow (OPF) problems. The main distinction of this approach is in using particle's worth experience in stead of the best previous experience. The proposed approach is evaluated on the IEEE 30-bus test system which minimizes the total fuel cost considering operational constraints such as power flow equations, transmission flow limits, bus voltages and reactive power of generators. The results obtained using the proposed approach are compared with results of other optimization methods  

This paper presents a fuzzy based modified artificial bee colony (MABC) algorithm to solve discrete optimal power flow (OPF) problem that has both discrete and continuous variables considering valve point effects. The OPF problem is formulated as a multi-objective mixed-integer nonlinear problem, where optimal settings of the OPF control variables for simultaneous minimization of total fuel cost of thermal units, total emission, total real power losses, and voltage deviation are obtained. The proposed approach is applied to the OPF problem on IEEE 30-bus and IEEE 118-bus test systems. The performance and operation of the proposed approach is compared with the conventional methods. The... 

This paper proposes a new coordinated voltage control scheme to ensure voltage security of power systems. The scheme schedules reactive power injection from VAR sources, including synchronous generators and condensers, capacitor banks, switchable reactors and FACTS devices, to ensure desired loading margin of power systems for a given horizon of time. The problem is treated as voltage security constrained multi-period optimal reactive power flow (VSC-MPORPF). To incorporate scheduling of both continuous and discrete VAR sources, the VSC-MPORPF is formulated as a mixed-integer nonlinear programming problem, and is solved using generalized Benders decomposition (GBD). Multi-period formulation... 

Management of reactive power resources is vital for stable and secure operation of power systems in the view point of voltage stability. This paper deals with the management of on-load tap changers (OLTCs) and dynamic VAR sources (including synchronous generators, synchronous condensers, and shunt reactive power compensators) to improve voltage stability margin (VSM) of power systems. This problem is usually called optimal reactive power dispatch (ORD) in the literature. The main contribution of the paper is to introduce a new objective function for the ORD problem. The proposed objective function is derived based on a local voltage stability index, called DSY, and has a strong correlation... 

Spinning reserve (SR) is one of the most important ancillary services which are needed for satisfying reliability requirements, including the desired level of security in power systems. By definition, spinning reserve is the unloaded section of synchronized generation that is able to respond immediately to serve load. This paper proposes a hybrid DCOPF and harmony search (HS) optimization method as a novel heuristic approach to the joint dispatch of energy and reserve considering the bottling of reserve due to transmission limits. The effectiveness of the proposed method is examined by applying it to the IEEE 30-bus test system. The results obtained using the proposed method are presented... 

In this paper, a hierarchical frequency regulation system is presented for real-time operation of the electrical grids. It includes a decentralized transactive energy system for clearing transactions of producers/consumers in real-time. The proposed system is implemented in a distributed fashion with small data communication requirement. It is proved that the proposed transactive energy system converges to the optimal power flow (OPF). An iterative method for optimizing control parameters of the proposed hierarchical frequency regulation system is also given. The proposed method is developed for high penetration of renewable energy sources (RESs) as the sizes, locations, and uncertainties of... 

The participants in auction-based electricity markets need to take part in a competition way, which operates, based on the concept of supply and demand theory to buy or sell the electricity. However, to have a feasible market solution, reactive power services are necessary to support the transmission of power from generation to end-users. This paper presents a methodology for optimal reactive power procurement, consistent with the auction-based electricity market mechanism. The proposed reactive power market is run in subsequence of the primary electricity market, allowing active power modification in light of available transmission capacity and reactive power resources. The IEEE 30-bus test... 

In our investigation, the model of optimal energy flow in a passenger vehicle has been founded on the theory of firm microeconomics. Based on this theory, the car owner tries to minimize the total cost of the system (including the cost of time of the traveller) subject to the satisfaction of the required transport services and technological, economical, environmental and institutional constraints. The aforementioned model has been developed using a technique of mathematical programming. The model depicts the behaviour of a nonlinear system and it includes many nonlinear functions in the objective function and in the constraints. Solving the large nonlinear set of constraints and identifying... 

Voltage stability is the ability of a power system to maintain acceptable voltages at all buses in the system under normal conditions and after being subjected to a disturbance. This paper employs the management of reactive power generation to improve the voltage stability margin (VSM), in the framework of optimal reactive power dispatch (ORD) problem. Scheduling of VAR sources is performed using the concept of relative value of VAR sources. The proposed methodology has been tested on the IEEE 14-bus test system. Simulation results show that after the optimal reactive power scheduling, VSM of the systems is increased considerably. In addition, it is observed that reactive power reserve is... 

Reactive power dispatch in power systems is a complex combinatorial optimization problem involving nonlinear functions with multiple local minima and nonlinear constraints. In an open electricity market reactive power support is an ancillary service for real power transportation. From the viewpoint of ISO, this paper provides a dispatching reactive power model, based on optimal power flow, by which both the cost of procuring reactive power as auxiliary service and the losses of active power are minimized. In this paper the cost of reactive power support consists of two components: reactive power cost of generators and shunt capacitors. In addition an extremely powerful differential evolution...