Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Solving Load Flow Problems of Power System by Explicit Pseudo-Transient Continuation (E-ψtc) Method  [PDF]
Tianmin Han, Yuhuan Han
Energy and Power Engineering (EPE) , 2016, DOI: 10.4236/epe.2016.82009
Abstract: This paper is a further study of two papers [1] and [2], which were related to Ill-Conditioned Load Flow Problems and were published by IEEE Trans. PAS. The authors of this paper have some different opinions, for example, the 11-bus system is not an ill-conditioned system. In addition, a new approach to solve Load Flow Problems, E-ψtc, is introduced. It is an explicit method; solving linear equations is not needed. It can handle very tough and very large systems. The advantage of this method has been fully proved by two examples. The authors give this new method a detailed description of how to use it to solve Load Flow Problems and successfully apply it to the 43-bus and the 11-bus systems. The authors also propose a strategy to test the reliability, and by solving gradient equations, this new method can answer if the solution exists or not.
Application of Pseudo-Transient Continuation Method in Dynamic Stability Analysis  [PDF]
Xiaozhe Wang,Hsiao-Dong Chiang
Computer Science , 2014,
Abstract: In this paper, pseudo-transient continuation method has been modified and implemented in power system long-term stability analysis. This method is a middle ground between integration and steady state calculation, thus is a good compromise between accuracy and efficiency. Pseudo-transient continuation method can be applied in the long-term stability model directly to accelerate simulation speed and can also be implemented in the QSS model to overcome numerical difficulties. Numerical examples show that pseudo-transient continuation method can provide correct approximations for the long-term stability model in terms of trajectories and stability assessment.
Pseudo transient continuation and time marching methods for Monge-Ampere type equations  [PDF]
Gerard Awanou
Mathematics , 2013,
Abstract: We present two numerical methods for the fully nonlinear elliptic Monge-Ampere equation. The first is a pseudo transient continuation method and the second is a pure pseudo time marching method. The methods are proven to converge to a strictly convex solution of a natural discrete variational formulation with $C^1$ conforming approximations. The assumption of existence of a strictly convex solution to the discrete problem is proven for smooth solutions of the continuous problem and supported by numerical evidence for non smooth solutions.
Condition Estimates for Pseudo-Arclength Continuation  [PDF]
K. I. Dickson,C. T. Kelley,I. C. F. Ipsen,I. G. Kevrekidis
Mathematics , 2006,
Abstract: We bound the condition number of the Jacobian in pseudo arclength continuation problems, and we quantify the effect of this condition number on the linear system solution in a Newton GMRES solve. In pseudo arclength continuation one repeatedly solves systems of nonlinear equations $F(u(s),\lambda(s))=0$ for a real-valued function $u$ and a real parameter $\lambda$, given different values of the arclength $s$. It is known that the Jacobian $F_x$ of $F$ with respect to $x=(u,\lambda)$ is nonsingular, if the path contains only regular points and simple fold singularities. We introduce a new characterization of simple folds in terms of the singular value decomposition, and we use it to derive a new bound for the norm of $F_x^{-1}$. We also show that the convergence rate of GMRES in a Newton step for $F(u(s),\lambda(s))=0$ is essentially the same as that of the original problem $G(u,\lambda)=0$. In particular we prove that the bounds on the degrees of the minimal polynomials of the Jacobians $F_x$ and $G_u$ differ by at most 2. We illustrate the effectiveness of our bounds with an example from radiative transfer theory.
PAMPAC: A Parallel Adaptive Method for Pseudo-Arclength Continuation  [PDF]
Dhavide Aruliah,Lennaert van Veen,Alex Dubitski
Computer Science , 2013,
Abstract: Pseudo-arclength continuation is a well-established method for generating a numerical curve approximating the solution of an underdetermined system of nonlinear equations. It is an inherently sequential predictor-corrector method in which new approximate solutions are extrapolated from previously converged results and then iteratively refined. Convergence of the iterative corrections is guaranteed only for sufficiently small prediction steps. In high-dimensional systems, corrector steps are extremely costly to compute and the prediction step-length must be adapted carefully to avoid failed steps or unnecessarily slow progress. We describe a parallel method for adapting the step-length employing several predictor-corrector sequences of different step lengths computed concurrently. In addition, the algorithm permits intermediate results of unconverged correction sequences to seed new predictions. This strategy results in an aggressive optimization of the step length at the cost of redundancy in the concurrent computation. We present two examples of convoluted solution curves of high-dimensional systems showing that speed-up by a factor of two can be attained on a multi-core CPU while a factor of three is attainable on a small cluster.
Transient Cooling Load Characteristic of an Academic Building, using TRNSYS
Petrus Tri Bhaskoro,Syed Ihstham Ul Haq Gilani
Journal of Applied Sciences , 2011,
Abstract: One of the major energy consumers in any commercial building, in hot and humid area is the air conditioning system. Therefore matching between Air Conditioning (AC) systems strategies with the cooling load characteristic is crucial to ensure effectiveness. Previous researches have been done to determine cooling load characteristic for offices and residential buildings. However, same research for academic buildings is rare and still need further development. The occupancy schedule in office and residential buildings are significantly different with academic buildings and so does the cooling load characteristic. Due to that the paper aims to provide transient cooling load characteristic for academic building through simulation using TRNSYS. The results showed that the major contributor to the cooling load was heat gain from building envelope which was counted up to 52.57% of the total cooling load in a year. The result also implied that cooling energy wasted during peak and off-peak period was approximately 50% of the total cooling load. Once transient cooling load characteristic was presented, three possible solutions were applied to the system to find best solution in reducing the cooling load. The result showed that the AC system with adjustable room temperature set point would have lowest cooling load. This solution would reduce the cooling load by 27.4%.
Fabiola Acon-Rojas,Rafael Gutierrez-Alvarez,Rolando Ulloa-Gutierrez,,Maria L Avila-Aguero
Electronic Journal of Biomedicine , 2005,
Abstract: SUMMARYWe describe a 2 year-old boy with severe vasculitis who presented with a typical Kawasaki disease complicated with an intestinal pseudo-obstruction, gallbladder hydrops, myocarditis and transient coronary abnormalities despite early administration of intravenous immunoglobulin treatment.RESUMENDescribimos el caso de un ni o de 2 a os con vasculitis grave que presentó un cuadro típico de enfermedad de Kawasaki complicada con una pseudo-obtrucción intestinal, hidrops vesicular, miocarditis y anormalidades coronarias transitorias, a pesar de la administración temprana de tratamiento con inmunoglulina intravenosa
Non-Intrusive Demand Monitoring and Load Identification for Energy Management Systems Based on Transient Feature Analyses  [PDF]
Hsueh-Hsien Chang
Energies , 2012, DOI: 10.3390/en5114569
Abstract: Energy management systems strive to use energy resources efficiently, save energy, and reduce carbon output. This study proposes transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the power demand and load operation. This study uses the wavelet transform (WT) of the time-frequency domain to analyze and detect the transient physical behavior of loads during the load identification. The experimental results show the transient response time and transient energy are better than the steady-state features to improve the recognition accuracy and reduces computation requirements in non-intrusive load monitoring (NILM) systems. The discrete wavelet transform (DWT) is more suitable than short-time Fourier transform (STFT) for transient load analyses.
Transient Vibration Prediction for Rotors on Ball Bearings Using Load-Dependent Nonlinear Bearing Stiffness  [PDF]
David P. Fleming,J. V. Poplawski
International Journal of Rotating Machinery , 2004, DOI: 10.1155/s1023621x0400048x
Abstract: Rolling-element bearing forces vary nonlinearly with bearing deflection. Thus an accurate rotordynamic transient analysis requires bearing forces to be determined at each step of the transient solution. Analyses have been carried out to show the effect of accurate bearing transient forces (accounting for nonlinear speed and load-dependent bearing stiffness) as compared to conventional use of average rolling-element bearing stiffness. Bearing forces were calculated by COBRA-AHS (Computer Optimized Ball and Roller Bearing Analysis—Advanced High Speed) and supplied to the rotordynamics code ARDS (Analysis of Rotor Dynamic Systems) for accurate simulation of rotor transient behavior. COBRA-AHS is a fast-running five degree-of-freedom computer code able to calculate high speed rolling-element bearing load-displacement data for radial and angular contact ball bearings and also for cylindrical and tapered roller bearings. Results show that use of nonlinear bearing characteristics is essential for accurate prediction of rotordynamic behavior.
Functionally-fitted explicit pseudo two-step Runge-Kutta-Nystr?m methods  [PDF]
N. S. Hoang
Mathematics , 2014,
Abstract: A general class of functionally-fitted explicit pseudo two-step Runge-Kutta-Nystr\"{o}m (FEPTRKN) methods for solving second-order initial value problems has been studied. These methods can be considered generalized explicit pseudo two-step Runge-Kutta-Nystr\"{o}m (EPTRKN) methods. We proved that an $s$-stage FEPTRKN method has step order $p = s$ and stage order $r = s$ for any set of distinct collocation parameters $(c_i)_{i=1}^s$. Supperconvergence for the accuracy orders of these methods can be obtained if the collocation parameters $(c_i)_{i=1}^s$ satisfy some orthogonality conditions. We proved that an $s$-stage FEPTRKN method can attain accuracy order $p = s + 3$. Numerical experiments have shown that the new FEPTRKN methods work better than do EPTRKN methods on problems whose solutions can be well approximated by the functions in bases on which these FEPTRKN methods are developed.
Page 1 /100
Display every page Item

Copyright © 2008-2017 Open Access Library. All rights reserved.