Showing papers by "Vignan University published in 2009"
28 Dec 2009
TL;DR: In this article, the optimal power flow (OPF) problem is defined as a power flow problem in which certain variables are adjusted to minimize an objective function such as cost of the active power generation or the losses, while satisfying physical operating limits on various controls, dependent variables and function of control variables.
Abstract: The optimal power flow is a power flow problem in which certain variables are adjusted to minimize an objective function such as cost of the active power generation or the losses,while satisfying physical operating limits on various controls, dependent variables and function of control variables. Current interest in OPF covers around its ability to solve for the optimal solution that takes account of security of the system. Practical solutions for OPF problems with separable objective functions have been obtained with special linear programming methods,but the classical OPF has defined practical solutions, the Newton approach is a flexible formulation that can be used to develop different OPF algorithms suited to the requirements of different applications. In other words, the optimal power problem seeks to find an optimal profile of active and reactive power generations along with voltage magnitudes in such a manner as to minimize the total operating costs of a thermal electric power system, while satisfying network security constraints. The OPF method is based on load flow solution by the Newton’s method, a first order gradient adjustment algorithm for minimizing the objective function and use of penalty functions to account for inequality constraints on dependent variables.
16 citations
28 Dec 2009
TL;DR: Advanced load flow models for the Static VAR compensator are presented and it is shown that the power system losses are decreased after incorporating the SVC in this N-R method.
Abstract: Static VAR compensator (SVC) is incorporated in Newton Raphson method in which Power Flow Solution is a solution of the network under steady state conditions subjected to certain constraints under which the system operates. The power flow solution gives the nodal voltages and phase angles given a set of power injections at buses and specified voltages at a few, both the models of SVC i.e.SVC Susceptance and Firing Angle Models are discussed. It is also shown that the power system losses are decreased after incorporating the SVC in this N-R method. The results are generated for 24-Bus system. The reactors are thyristor-controlled and the capacitors can be either fixed or controlled. Advanced load flow models for the SVC are presented in this paper. The models are incorporated into existing load flow (LF) Newton Raphson algorithm. The new models depart from the generator representation of the SVC and are based instead on the variable susceptance concept. The SVC state variables are combined with the nodal voltage magnitudes and angles of the network in a single frame of reference for a unified, iterative solution through Newton methods. The algorithm for Load Flow exhibit very strong convergence characteristics, regardless of the network size and the number of controllable devices. Results are presented which demonstrate the process of the new SVC models.
13 citations
01 Dec 2009
TL;DR: A comparison with the peak-signal-to-noise ratio (PSNR) and state of the art metric, Mean Structural Similarity Index (MSSIM), shows that the proposed measure correlates better with the judgment of human observers.
Abstract: In this paper a full reference objective image quality assessment technique is presented which is based on the properties of the human visual system (HVS). By integrating the notion of perceptually important regions with the measurement of structural similarity between the original image and distorted image a contrast weighted Perceptual Structural SIMilarity Index PSSIM c is proposed. The method first evaluates the structural similarity indices between the original and distorted image in local regions. These local indices are then weighted based on the perceptual weights of the corresponding region, characterized by the contrast value of the local region. PSSIM c of an image is calculated as the average of these weighted indices. A comparison with the peak-signal-to-noise ratio (PSNR) and state of the art metric, Mean Structural Similarity Index (MSSIM), shows that the proposed measure correlates better with the judgment of human observers.
8 citations
28 Dec 2009
TL;DR: A rule-based fuzzy logic controller is designed for Yaw control, which is used for the rudder movement of an underwater vehicle, and the control algorithm becomes shorter and runs faster than those that reinterpret the rules at each control cycle of the system.
Abstract: The underwater vehicle is six degrees of freedom model. The execution of spatial maneuvers are determined mainly by the dynamic properties of underwater vehicle particularly controllability and stability. The control surfaces are situated at the rear end of the underwater vehicle which moves either vertically or horizontally (Pitch, Yaw, Roll, Pitch-rate,Yaw-rate etc.) used to steer the vehicle to run according to preprogrammed course as per logic till such a time the target is acquired. The underwater vehicle response is slow compared to air scenario due to constraints like higher density of water; the resistance motion is many hundred times greater than air. In this paper a rule-based fuzzy logic controller is designed for Yaw control, which is used for the rudder movement of an underwater vehicle. A Plant model is extracted using the input and output behavior and is assumed to be a linear time invariant second order. For on line implementation a decision table is stored in underwater vehicle computer memory in the form of Lookup table. For each combination of Inputs the required search will be done in the table and the appropriate value will be picked up. Using this technique the control algorithm becomes shorter and runs faster than those that reinterpret the rules at each control cycle of the system. This Lookup Table is used in the simulation of Yaw control of a Six Degrees of Freedom Model. The plant responses are compared for both conventional controller and fuzzy logic controller with regard to time of response, overshoot and steady state error.
5 citations
TL;DR: In this article, the design and sizing of a Multiple Input Hybrid Charging System (MIHCS) to be used in Hybrid Electric Vehicle (HEV) propulsion is proposed.
Abstract: The scarcity and cost of fossil fuels, combined with their greenhouse gas emissions, make the development of nonfossil fuel-based methods of transportation a high-priority task. This paper proposes the designing and sizing of a Multiple Input Hybrid Charging System (MIHCS) to be used in Hybrid Electric Vehicle (HEV) propulsion. It includes a fuel cell generator, solar cell charger, Internal Combustion Engine (ICE), flywheel storage system, on-board sources and a combined Energy Storage System (ESS) comprising a battery pack. Based on the speed range of the vehicle, multiple sources like solar energy, fuel cells and wind power are automatically selected for propulsion or charging purposes by using computer and interfacing circuits. To realise this logic, a program has been developed in 'C' language. This logic also helps in controlling the charging and discharging times of the batteries placed in the energy storage unit.
2 citations