Дисертації з теми "Power-flow solution"
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1
Laury, John. "Optimal Power Flow for an HVDC Feeder Solution for AC Railways." Thesis, KTH, Elektrisk energiomvandling, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-104655.
Повний текст джерелаАнотація:
With today’s increasing railway traffic, the demand for electrical power has increased. However, several railway systems are weak and are not being controlled optimally. Thus, transmission losses are high and the voltage can be significantly lower than the nominal level. One proposal, instead of using an extra HVAC power supply system, is to implement a HVDC supply system. A HVDC supply line would be installed in parallel to the current railway catenary system and power can be exchanged between the HVDC grid and the catenary through converters. This thesis investigates different properties and behaviours of a proposed HVDC feeder solution. An AC/DC unified Optimal Power Flow (OPF) model is developed and presented. Decision variables are utilized to obtain proper control of the converters. The used power flow equations and converter loss function, which are non linear, and the use of binary variables for the unit commitment leads to an optimization problem, that requires Mixed Integer Non-Linear Programing (MINLP) for solving. The optimization problem is formulated in the software GAMS, and is solved by BONMIN. In each case investigated, the objective is to minimize the total active power losses. The results of the investigated cases presented in this thesis, show that the proposed OPF-controlled HVDC solution reduces the losses and provides better voltage profile at the catenary, compared with today’s supply systems.
2
Kleinberg, Michael R. Miu Karen Nan. "Distributed multi-phase distribution power flow : modeling, solution algorithm, and simulation results /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1307.
Повний текст джерела
3
Huneault, Maurice. "An investigation of the solution to the optimal power flow problem incorporating continuation methods /." Thesis, McGill University, 1988. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=75853.
Повний текст джерелаАнотація:
This thesis analyzes and tests some new solution techniques for the optimal power flow problem. This new methodology exploits a parametric technique, called the continuation method, which is applied to different tasks in the solution procedure. In a first application, the continuation method solves the quadratic subproblems generated sequentially by the optimal power flow's nonlinear program. It first creates a simple subproblem, which is easy to solve, and then links it to the subproblem we wish to solve. Starting at the solution of the simple problem, it generates optimal solution trajectories for the intermediate problems, leading to the desired optimal solution. In a second application, the algorithm tracks optimal solutions trajectories of the nonlinear problem when the load is slowly varied. This constitutes an example of "incremental loading", a technique already used for real power dispatch, but in this case a complete network model is used. The flexibility of the algorithm at various levels allows for some excellent computation times in this load-tracking mode: we have observed reductions in computation times for new solutions of the order of 70%, compared to the computation time of the initial load.This thesis first presents an analysis of the various structures used in optimal power flow algorithms. Then, having chosen and presented the structure of our algorithm, we analyze the quadratic subproblems generated by this algorithm for some of its more important tasks: minimum cost, minimum losses and load shedding. New rules are proposed to link the solutions of successive subproblems to ensure the convergence of the nonlinear problem. Then, as a final contribution to the theory, some extensions are suggested for the subproblems: among them are ramp constraints, bus incremental costs, and provisions for redispatching.
Numerical simulations of the proposed optimal power flow algorithm using the minimum fuel cost task were performed on four test systems, with sizes ranging from 6 to 118 buses. The results are documented in detail, and results for the 30 bus test are compared to those reported by other authors. All in all, our results demonstrate quite well the potential of this technique. (Abstract shortened with permission of author.)
4
Isazadeh, Mohammad Ali. "Numerical solution of reacting laminar flow heat and mass transfer in ducts of arbitrary cross-sections for power-law fluids." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41628.
Повний текст джерелаАнотація:
This study is concerned with the numerical analysis, formulation, programming and computation of solution of steady, 3D conservation equations of reacting laminar duct flow heat and mass transfer in ducts of arbitrary cross-sections. The non-orthogonal boundary-fitted coordinate transformation method is applied to the Cartesian form of overall-continuity, momenta, energy and species-continuity equations, parabolized in the axial direction. The boundary conditions are also transformed accordingly.In the mathematical modelling of the system under consideration, variable physical and transport properties of fluid, viscous heat-dissipation and buoyancy effects are also considered. The non-Newtonian power-law constitutive equation is employed to express the rheology of the purely viscous fluid considered.
Applying a novel feature of the solution procedure, the contravariant velocity components are introduced into the transformed equations while the physical Cartesian velocity components are retained as dependent variables of the velocity field in the equations. This approach greatly simplifies the subsequent finite-difference formulation of the transformed equations. The latter equations are discretized by the control-volume finite-difference method in which a suitably-adopted staggered grid is employed using Patankar's B-type arrangement in the transformed plane. For discretization, the transformed equations are integrated over 3D control-volumes, followed by differencing the convective and diffusive terms employing upwind and central-difference schemes respectively. A modified version of the SIMPLER algorithm is introduced in the solution procedure and a line-by-line TDMA algorithm is employed for the solution of the discretization equations.
A computer-programme is developed for the generation of non-orthogonal grids corresponding to the B-type arrangement in the transformed plane. A general computer programme in Fortran is developed in this study for the solution of flow, heat and mass transfer problems for laminar reacting fluids in straight ducts of arbitrary cross-sections for Newtonian and purely viscous non-Newtonian fluids. The model and computer codes are validated by theoretical, experimental and numerical results from various sources.
The computer programmes are employed for studies in the analysis of hydrodynamics and heat transfer in the thermal entrance regions of ducts of arbitrary cross-sections for Newtonian and non-Newtonian fluids. Relevant results are documented for triangular, trapezoidal and pentagonal ducts. The computer programmes are ultimately employed for simulation of the production of polystyrene in arbitrary cross-sectional duct reactors.
5
HIPOLITO, FABIO C. "Avaliação das metodologias de análise de sistemas de tubulações de vapor sujeitas a carregamentos do tipo Steam Hammer." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26938.
Повний текст джерелаАнотація:
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Carregamentos transientes termo hidráulicos do tipo Steam Hammer são eventos comuns em sistemas de tubulações de vapor com grandes potenciais de catástrofes em plantas de geração de energia. Uma vez iniciado o evento, ondas de pressões são geradas com amplitudes, geralmente, de grande magnitude ocasionando altas pressões no sistema, ruídos, deformações, fadiga, com possibilidade de danos materiais e econômicos e em casos extremos fatalidades. Os procedimentos da indústria para análise deste tipo de sistema consistem realização de análises estáticas equivalentes ou análise de espectro de resposta com carregamentos caracterizados por meio de métodos analíticos baseados em hipóteses simplificadoras do fluido e fluxo. Neste trabalho é proposta a analise de sistema de tubulações por meio do método de integração numérica com superposição modal e carregamento caracterizado por método numérico com base no método das características. Comparações foram efetuadas entre os resultados obtidos pela metodologia proposta e os procedimentos da indústria, demonstrando que, dado ao alto grau de conservadorismo, os procedimentos da indústria acarretam em superdimensionamento de estruturas e tubulações ocasionando custos adicionais de projeto, sendo a otimização do projeto obtida aplicando-se a metodologia proposta no trabalho.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
6
Xu, Wenyuan. "A multiphase harmonic load flow solution technique." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31035.
Повний текст джерелаАнотація:
This thesis presents a comprehensive solution technique for power system harmonic analysis
with unbalanced load flow conditions. It is based on multiphase modelling of the system in phase quantities.
Two of the most important features of this technique are the multiphase approach to the harmonic load flow problem, and the capability to add component nonlinearities easily. The first feature allows the technique to be used for either single-phase or three-phase, and for either balanced or unbalanced harmonic analysis. The second feature allows the later addition of power electronic device models.
The technique is simple in concept. The nonlinear elements are first modelled as harmonic
Norton equivalent circuits based on the network load flow conditions. These linear circuits are then included in the network solution with multiphase load flow constraints and network unbalances. Once the new load flow solutions are obtained, improved Norton
equivalent circuits can be calculated, which in turn are used for improved network solutions. The entire solution scheme is therefore iterative, and stops when certain convergence
criteria are met.
The unbalanced harmonics from nonlinear inductors, synchronous machines and static compensators with thyristor-controlled reactors are studied in this thesis. The convergence
properties of the technique are investigated with test cases and theoretical analysis.
In addition to the harmonic load flow analysis, this technique can also be used as an improved initialization procedure for the Electromagnetic Transient Program (EMTP).Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
7
Salgado, Roberto de Souza. "Optimal power flow solutions using the gradient projection method." reponame:Repositório Institucional da UFSC, 1989. http://repositorio.ufsc.br/xmlui/handle/123456789/75577.
Повний текст джерела
8
Abur, Ali. "Knowledge-based power flow models and array processor-based power flow solutions for fast prediction of system states /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487261553057511.
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9
García-Blanco, Raquel. "Efficient solvers for power flow equations : parametric solutions with accuracy control assessment." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/458887.
Повний текст джерелаАнотація:
The Power Flow model is extensively used to predict the behavior of electric grids and results in solving a nonlinear algebraic system of equations. Modeling the grid is essential for design optimization and control. Both applications require a fast response for multiple queries to a parametric family of power flow problems. Different solvers have been introduced especially designed for the algebraic nonlinear power flow equations, providing efficient solutions for single problems, even when the number of degrees of freedom is considerably large. However, there is no existing methodology providing an explicit solution of the Parametric Power Flow problem (viz. a computational vademecum, explicit in terms of the parameters).
This work aims precisely at designing algorithms producing computational vademecums for the Parametric Power Flow problem. Once these solutions are available, solving for different values of the parameters is an extremely fast (real-time) post-process and therefore both the optimal design and the control problem can readily be addressed.
In a first phase, a new family of iteratives solvers for the non-parametric version of the problem is devised. The method is based on a hybrid formulation of the problem combined with an alternated search directions scheme. These methods are designed such that it can be generalized to deal with the parametric version of the problem following a Proper Generalized Decomposition (PGD) strategy.
The solver for the parametric problem is conceived by performing the operations involving the unknowns in a PGD fashion. The algorithm follows the basic steps of the algebraic solver, but some operations are carried out in a PGD framework, that is requiring a nested iterative algorithm. The PGD solver is accompanied with an error assessment technique that allows monitoring the convergence of the iterative procedures and deciding the number of terms required to meet the accuracy prescriptions. Different examples of realistic grids and standard benchmark tests are used to demonstrate the performance of the proposed methodologies.El modelo de flujo de potencias se usa para predecir el comportamiento de redes eléctricas y desemboca en la resolución de un sistema de ecuaciones algebraicas no lineales. Modelar una red es esencial para optimizar su diseño y control. Ambas aplicaciones requieren una respuesta rápida a las múltiples peticiones de una familia paramétrica de problemas de flujo de potencias. Diversos métodos de resolución se diseñaron especialmente para resolver la versión algebraica de las ecuaciones de flujo de potencias. Sin embargo, no existe ninguna metodología que proporcione una solución explícita al problema paramétrico de flujo de potencias (esto quiere decir, un vademecum computacional explícito en términos de los parámetros). Esta tesis tiene como objetivo diseñar algoritmos que produzcan vademecums para el problema paramétrico de flujo de potencias. Una vez que las soluciones están disponibles, resolver problemas para diferentes valores de los parámetros es un posproceso extremadamente rápido (en tiempo real) y por lo tanto los problemas de diseño óptimo y control se pueden resolver inmediatamente. En la primera fase, una nueva familia de métodos de resolución iterativos para la versión algebraica del problema se construye. El método se basa en una formulación híbrida del problema combinado con un esquema de direcciones alternadas. Estos métodos se han diseñado para generalizarlos de forma que puedan resolver la versión paramétrica del problema siguiendo una estrategia llamada Descomposición Propia Generalizada (PGD). El método de resolución para el problema paramétrico calcula las incógnitas paramétricas usando la técnica PGD. El algoritmo sigue los mismo pasos que el algoritmo algebraico, pero algunas operaciones se llevan a cabo en el ambiente PGD, esto requiere algoritmos iterativos anidados. El método de resolución PGD se acompaña con una evaluación del error cometido permitiendo monitorizar la convergencia de los procesos iterativos y decidir el número de términos que requiere la solución para alcanzar la precisión preescrita. Diferentes ejemplos de redes reales y tests estándar se usan para demostrar el funcionamiento de las metodologías propuestas.
10
Wu, Wei. "Research on loop flow problem and its solutions in Macau power system." Thesis, University of Macau, 2003. http://umaclib3.umac.mo/record=b1807202.
Повний текст джерела
11
McCraney, Joshua Thomas. "Analysis of Capillary Flow in Interior Corners : Perturbed Power Law Similarity Solutions." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2725.
Повний текст джерелаАнотація:
The design of fluid management systems requires accurate models for fluid transport. In the low gravity environment of space, gravity no longer dominates fluid displacement; instead capillary forces often govern flow. This thesis considers the redistribution of fluid along an interior corner. Following a rapid reduction of gravity, fluid advances along the corner measured by the column length z = L(t), which is governed by a nonlinear partial differential equation with dynamical boundary conditions. Three flow types are examined: capillary rise, spreading drop, and tapered corner. The spreading drop regime is shown to exhibit column length growth L ~ t2/5, where a closed form analytic solution exists. No analytic solution is available for the capillary rise problem. However, a perturbed power law similarity solution is pursued to approximate an analytic solution in the near neighborhood of the exact solution for the spreading drop. It is recovered that L ~ t1/2 for the capillary rise problem. The tapered corner problem is not analytically understood and hence its corresponding L is undocumented. Based on the slender corner geometry, it is natural to hypothesize the tapered corner column length initially behaves like the capillary rise regime, but after sufficient time has elapsed, it transitions into the spreading drop regime. This leads to a conjecture that its column length growth L is restricted to t2/5 < L < t1/2. To verify this conjecture an explicit finite difference numerical solution is developed for all three regimes. As will be shown, the finite difference scheme converges towards the analytic solutions for the spreading drop and capillary rise regimes. From this we assume the finite difference scheme is accurate for corner flows of similar geometries, and thus apply this scheme the more onerous criteria of the tapered corner. Numerical results support the conjectured L behavior for the tapered corner. Understanding the dynamics of such flows and responses to various geometries offers design advantages for spacecraft waste-management systems, fuel control, hydration containment, cryogenic flows, and a myriad of other fluid applications.
12
Bukhsh, Waqquas Ahmed. "Islanding model for preventing wide-area blackouts and the issue of local solutions of the optimal power flow problem." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9671.
Повний текст джерелаАнотація:
Optimization plays a central role in the control and operation of electricity power networks. In this thesis we focus on two very important optimization problems in power systems. The first is the optimal power flow problem (OPF). This is an old and well-known nonconvex optimization problem in power system. The existence of local solutions of OPF has been a question of interest for decades. Both local and global solution techniques have been put forward to solve OPF problem but without any documented cases of local solutions. We have produced test cases of power networks with local solutions and have collected these test cases in a publicly available online archive (http://www.maths.ed.ac.uk/optenergy/LocalOpt/), which can be used now by researchers and practitioners to test the robustness of their solution techniques. Also a new nonlinear relaxation of OPF is presented and it is shown that this relaxation in practice gives tight lower bounds of the global solution of OPF. The second problem considered is how to split a network into islands so as to prevent cascading blackouts over wide areas. A mixed integer linear programming (MILP) model for islanding of power system is presented. In recent years, islanding of power networks is attracting attention, because of the increasing occurrence and risk of blackouts. Our proposed approach is quite flexible and incorporates line switching and load shedding. We also give the motivation behind the islanding operation and test our model on variety of test cases. The islanding model uses DC model of power flow equations. We give some of the shortcomings of this model and later improve this model by using piecewise linear approximation of nonlinear terms. The improved model yields good feasible results very quickly and numerical results on large networks show the promising performance of this model.
13
Ebrahimpour, Mohammad Reza. "An analytical study of the power flow equations with applications to systems with multiple close solutions." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/15746.
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14
Cheng, Yu Syuan, and 鄭宇軒. "Pareto optimal solution and optimal multiobjective solution for risk-limiting optimal power flow." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/9jeguw.
Повний текст джерела
15
Liu, Min-Fun, and 劉明芳. "A NETWORK-CLUSTER METHOD FOR POWER FLOW SOLUTION BASED ON MULTI-PROCESSORS." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/65223311269577033103.
Повний текст джерелаАнотація:
碩士國立成功大學
電機工程研究所
82
In this paper, we utilize the multi-processors for investigating the solution of power flow in two ways. First, by properly clustering and sorting the Jacobi matrix, we transform the matrix into a block diagonal form. Most of the non-zero entries are now gathered near the main diagonal. We then investigate the effect that the number of non-zero entries of non-diagonal blocks will have on the convergence of the solution. The multi-processors are adopted to get all the solutions.Secondly, we perform clustering directly from the network. Then we can obtain a border block diagonal form of the Jacobi matrix. Since the parallel processing of multi- processors can be applied to it, the execution time is largely reduced. We have implemented our method to cluster the IEEE-30, 57, and 118 bus network testing systems. From the experimental results, we see that our method requires less execution time when comparing with the traditional method using sequential computing.
16
CHEN, XIN-DE, and 陳新得. "A study on the uniqueness of load flow solution for radial distribution power networks." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/63499700427094213083.
Повний текст джерела
17
Chen, Shibing. "Convex Solutions to the Power-of-mean Curvature Flow, Conformally Invariant Inequalities and Regularity Results in Some." Thesis, 2013. http://hdl.handle.net/1807/43516.
Повний текст джерелаАнотація:
In this thesis we study three different problems: convex ancient solutions to the power-of-mean curvature flow; Sharp inequalities; regularity results in some applications of optimal transportation.
The second chapter is devoted to the power-of-mean curvature flow; We prove some estimates for convex ancient solutions (the existence time for the solution starts from -\infty) to the power-of-mean curvature flow, when the power is strictly greater than \frac{1}{2}. As an application, we prove that in two dimension, the blow-down of an entire convex translating solution, namely u_{h}=\frac{1}{h}u(h^{\frac{1}{1+\alpha}}x), locally uniformly converges to \frac{1}{1+\alpha}|x|^{1+\alpha} as
h\rightarrow\infty. The second application is that for generalized curve shortening flow (convex curve evolving in its normal direction with speed equal to a power of its curvature), if the convex compact ancient solution sweeps the whole space \mathbb{R}^{2}, it must be a shrinking circle. Otherwise the solution must be defined in a strip region.
In the first section of the third chapter, we prove a one-parameter family of sharp conformally invariant integral inequalities for functions on the $n$-dimensional unit ball. As a limiting case, we obtain an inequality that generalizes Carleman's inequality for harmonic functions in the plane to poly-harmonic functions in higher dimensions. The second section represents joint work with Tobias Weth and Rupert Frank; the main result is that, one can always put a sharp remainder term on the righthand side of the sharp fractional sobolev inequality.
In the first section of the final chapter, under some suitable condition, we prove that the solution to the principal-agent problem must be C^{1}. The proof is based on a perturbation argument. The second section represents joint work with Emanuel Indrei; the main result is that, under (A3S) condition on the cost and c-convexity condition on the domains, the free boundary in the optimal partial transport problem is C^{1,\alpha}.
18
Liu, Jen-Sen, and 劉振森. "Modeling and Numerical Solution of Power Flow Computation for Ungrounded DC Rail Traction System Using Ladder Circuits." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/cmz25b.
Повний текст джерелаАнотація:
博士國立臺北科技大學
電機工程系博士班
102
Accurate solution of ungrounded DC rail system load flow requires the inclusion of detailed negative path components in the traction power network circuit model, resulting in large numbers of circuit nodes and branches. Such modeling complexity brings about heavy computational burden, ill numerical conditions, and nonlinear circuit components not readily solved for by nodal equations. In this dissertation we present a novel methodology utilizing the ladder-circuit topology of ungrounded DC rail traction networks to perform accurate and efficient load flow computation. We first study the circuit configuration of traditional grounded traction networks, and introduce a ladder-circuit load flow solution formulation based on the similarity to AC radial power distribution systems. Compare with the common-used nodal equation formulation, this solution scheme can do without large scale simultaneous circuit equations or the need to perform large-dimensional matrix manipulations, hence can achieve computational efficiency as well as numerical stability. Modern ungrounded DC traction power systems have cross bondings in the negative return circuits to reduce resistance, adding more complexity and asymmetry to the traction circuit. Thus we propose an approximate model of the so-called double ladder circuit to preserve the simplicity of grounded DC track networks without sacrificing analytical accuracy. The ladder circuit model is implemented by diakoptics to decompose an ungrounded DC traction networks into individual track circuits and substations. By iterative solution of load flows in two loops of calculations for track circuit layers and substation layers, respectively, the proposed algorithm requires computational burden proportional to the number of substations and track circuits. The computation results from two transit lines in Taiwan show that the proposed algorithm achieves the objectives of computational proficiency, numerical robustness, and versatility to various network configurations such as branch lines.
19
"Solving for the Low-Voltage/Large-Angle Power-Flow Solutions by using the Holomorphic Embedding Method." Doctoral diss., 2015. http://hdl.handle.net/2286/R.I.34817.
Повний текст джерелаАнотація:
abstract: For a (N+1)-bus power system, possibly 2N solutions exists. One of these solutions
is known as the high-voltage (HV) solution or operable solution. The rest of the solutions
are the low-voltage (LV), or large-angle, solutions.
In this report, a recently developed non-iterative algorithm for solving the power-
flow (PF) problem using the holomorphic embedding (HE) method is shown as
being capable of finding the HV solution, while avoiding converging to LV solutions
nearby which is a drawback to all other iterative solutions. The HE method provides a
novel non-iterative procedure to solve the PF problems by eliminating the
non-convergence and initial-estimate dependency issues appeared in the traditional
iterative methods. The detailed implementation of the HE method is discussed in the
report.
While published work focuses mainly on finding the HV PF solution, modified
holomorphically embedded formulations are proposed in this report to find the
LV/large-angle solutions of the PF problem. It is theoretically proven that the proposed
method is guaranteed to find a total number of 2N solutions to the PF problem
and if no solution exists, the algorithm is guaranteed to indicate such by the oscillations
in the maximal analytic continuation of the coefficients of the voltage power series
obtained.
After presenting the derivation of the LV/large-angle formulations for both PQ
and PV buses, numerical tests on the five-, seven- and 14-bus systems are conducted
to find all the solutions of the system of nonlinear PF equations for those systems using
the proposed HE method.
After completing the derivation to find all the PF solutions using the HE method, it
is shown that the proposed HE method can be used to find only the of interest PF solutions
(i.e. type-1 PF solutions with one positive real-part eigenvalue in the Jacobian
matrix), with a proper algorithm developed. The closet unstable equilibrium point
(UEP), one of the type-1 UEP’s, can be obtained by the proposed HE method with
limited dynamic models included.
The numerical performance as well as the robustness of the proposed HE method is
investigated and presented by implementing the algorithm on the problematic cases and
large-scale power system.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2015
20
Armistead, Robert Bernard. "MPI-based Parallel Solution of Sparse Linear Systems Using Chio's Condensation Algorithm and Test Data from Power Flow Analysis." 2010. http://trace.tennessee.edu/utk_gradthes/601.
Повний текст джерелаАнотація:
Solving sparse systems of linear equations permeates power system analysis. Newton-Raphson, decoupled, and fast decoupled algorithms all require the repeated solving of sparse systems of linear equations in order to capture the steady state operational conditions of the power system under test. Solving these systems of equations is usually done using LU Factorization which has an order of complexity O(n3) where n represents the number of equations in the system. The Chio’s condensation algorithm is an alternative approach, which in general has a complexity of O(n4). However, it has a straightforward formulation that can be easily implemented in a parallel computing architecture. Previous research has not investigated the application of the Chio’s algorithm under sparse matrix, which is typical for power system analysis. This thesis presents a MPI-based parallel solution of sparse linear systems using Chio’s condensation algorithm and realistic test data from power flow analysis. Different sparse matrix techniques are discussed, and a reordering scheme is applied to further improve the efficiency for solving the sparse linear system.
21
Liu, Jen-Sen, and 劉振森. "Solution of DC Power Flow for Non-grounded Traction Systems Using Chain-rule Reduction of Ladder Circuit Jacobian Matrices." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/36315839882462607911.
Повний текст джерелаАнотація:
碩士國立臺北科技大學
電機工程系碩士班
90
Traditionally DC power flow of traction systems are based on grounded load model. That is, like AC power system, each train is modeled as a load with power feeding from the third rail to ground. This model was appropriate for grounded DC traction systems in early days. As the trend migrating to non-grounded systems, the negative return path is batter described as a sequence of nodes and impedance among them, similar to the positive path. Together the circuit is of ladder-like configuration and can be solved using nodel circuit analysis and other computational algorithms. Numerical methods such as Newton-Raphson method are usually applied to implement DC power flow solution techniques. The dimension of the Jacobian matrices for Newton-Raphson methods grows with the complexity of the network, namely, the total number of nodes in the network. Our approach first solves each ladder circuit between two adjacent traction substations (TSS) in the inner loop using chain rule to convert the Jacobian matrix into the product of a sequence of small Jacobian matrices. This can reduce the computational complexity dramatically as matrix inversion is involved. Then power flow into all ladder circuits and output of each TSS are calculated in the outer loop. Finally, iterative procedures are repeated to obtain the complete DC power solution. We apply our method to a section of the planned extension of the Orange line of Taipei rapid transit system. The results show that both the inner and outer loops converge in a few iterations. Moreover, by decoupling power flow computation of each ladder circuit with the whole network we can make it easier to combine it with train performance simulation to obtain more accurate transit system simulation.
22
Blaette, Lutz. "Vortex Driven Acoustic Flow Instability." 2011. http://trace.tennessee.edu/utk_graddiss/951.
Повний текст джерелаАнотація:
Most combustion machines feature internal flows with very high energy densities. If a small fraction of the total energy contained in the flow is diverted into oscillations, large mechanical or thermal loads on the structure can be the result, which are potentially devastating if not predicted correctly. This is particularly the case for lightweight high performing devices like rockets. The problem is commonly known as "Combustion Instability". Several mechanisms have been identified in the past that link the flow field to the acoustics inside a combustion chamber and thereby drive or dampen oscillations, one of them being vortex shedding. The interaction between the highly sheared flow behind an obstacle and longitudinal acoustic oscillations inside a solid rocket booster is investigated both analytically and experimentally.The analytical approach is developed based on modeling of the second order acoustic energy. The energy model is applied to the specific flow conditions just downstream of a single baffle protruding into the flow. The mean flow profile is assumed to be of the form of a hyperbolic tangent, the unsteady acoustic velocities are assumed to be sinusoidally oscillating. Solutions for the unsteady rotational velocities and the unsteady vorticity are derived. The resulting flow field is utilized in stability calculations for a simplified two-dimensional axial-symmetric geometry. This yields to linear growth rates of the (longitudinal) oscillation modes. The growth rates are functions of the chamber geometry, the mean flow properties and the properties of the shear layer created by the flow restriction.A cold flow experiment is designed, tested and performed in order to validate the analytical findings. Flow is injected radially into a tube with acoustic closed-closed end conditions. A single baffle is installed in the tube, the axial position of the baffle is varied as well as its inner diameter. Frequency spectra of pressure oscillations are recorded. The experimental data is then compared qualitatively to the analytical growth rates. Those longitudinal Normal Modes, which feature the highest theoretical growth rates, are expected to be most prominent in the experimental data. This behavior is clearly observable.
23
Avalos, Munoz Jose Rafael. "Analysis and Application of Optimization Techniques to Power System Security and Electricity Markets." Thesis, 2008. http://hdl.handle.net/10012/3692.
Повний текст джерелаАнотація:
Determining the maximum power system loadability, as well as preventing the system from being operated close to the stability limits is very important in power systems planning and operation. The application of optimization techniques to power systems security and electricity markets is a rather relevant research area in power engineering. The study of optimization models to determine critical operating conditions of a power system to obtain secure power dispatches in an electricity market has gained particular attention. This thesis studies and develops optimization models and techniques to detect or avoid voltage instability points in a power system in the context of a competitive electricity market.
A thorough analysis of an optimization model to determine the maximum power loadability points is first presented, demonstrating that a solution of this model corresponds to either Saddle-node Bifurcation (SNB) or Limit-induced Bifurcation (LIB) points of a power flow model. The analysis consists of showing that the transversality conditions that characterize these bifurcations can be derived from the optimality conditions at the solution of the optimization model. The study also includes a numerical comparison between the optimization and a continuation power flow method to show that these techniques converge to the same maximum loading point. It is shown that the optimization method is a very versatile technique to determine the maximum loading point, since it can be readily implemented and solved. Furthermore, this model is very flexible, as it can be reformulated to optimize different system parameters so that the loading margin is maximized.
The Optimal Power Flow (OPF) problem with voltage stability (VS) constraints is a highly nonlinear optimization problem which demands robust and efficient solution techniques. Furthermore, the proper formulation of the VS constraints plays a significant role not only from the practical point of view, but also from the market/system perspective. Thus, a novel and practical OPF-based auction model is proposed that includes a VS constraint based on the singular value decomposition (SVD) of the power flow Jacobian. The newly developed model is tested using realistic systems of up to 1211 buses to demonstrate its practical application. The results show that the proposed model better represents power system security in the OPF and yields better market signals. Furthermore, the corresponding solution technique outperforms previous approaches for the same problem. Other solution techniques for this OPF problem are also investigated. One makes use of a cutting planes (CP) technique to handle the VS constraint using a primal-dual Interior-point Method (IPM) scheme. Another tries to reformulate the OPF and VS constraint as a semidefinite programming (SDP) problem, since SDP has proven to work well for certain power system optimization problems; however, it is demonstrated that this technique cannot be used to solve this particular optimization problem.
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Niu, Yun. "Transmission congestion solutions by optimal power flow and load management." Thesis, 2002. http://hdl.handle.net/2429/12149.
Повний текст джерелаАнотація:
Deregulation of power industry creates big challenges to the operation of a
transmission system due to the physical limits of the system. One of the challenges is
transmission congestion management. Transmission congestion can not only pose a
physical threat to the system security but also can result in severe economic problems
such as price volatility. In particular, when customers within a congested area cannot
flexibly reduce their consumption, they may suffer from extremely high prices. The
economic benefit of deregulation can, therefore, be reduced by a large extent. To avoid
the system security problems and the reduction of economic benefit of the deregulated
system, an effective approach to solve the transmission congestion problem is presented
in this thesis. In the proposed solution, one load customer was chosen to lower its
consumption of electricity when congestion occurs. Three indices are used to decide who
will be this customer and how much load curtailment is required. At the same time, to
keep the balance of the power within the entire system, a generation redispatch procedure
is also suggested by using a similar decision procedure. The proposed scheme is tested in
simulation on modified IEEE 14 and 30 bus systems. The simulation results prove that
the proposed solution effectively relieves congestion while taking into consideration
physical and economic factors of the transmission system.
25
Yeh, Guey-Haw, and 葉桂華. "A Novel Algorithm to Compute All the Type-1 Power Flow Solutions." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/22623102724411724528.
Повний текст джерелаАнотація:
碩士國立臺灣大學
電機工程學系
86
This thesis presents a novel, numerically efficient algorithm, which is base don Continuation Power Flow to compute all the type-1 power flow solutions. Ty pe-1solutions are used in conjunction with techniques such as energy methods a nd thevoltage instability proximity index for assessing system voltage instabi lity.
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Magan, Avnish Bhowan. "Group invariant solutions and conservation laws for jet flow models of non-Newtownian power-law fluids." Thesis, 2014. http://hdl.handle.net/10539/14926.
Повний текст джерелаАнотація:
The non-Newtonian incompressible power-law
uid in jet
ow models is investigated.
An important feature of the model is the de nition of a suitable
Reynolds number, and this is achieved using the standard de nition of a
Reynolds number and ascertaining the magnitude of the e ective viscosity.
The jets under examination are the two-dimensional free, liquid and wall
jets. The two-dimensional free and wall jets satisfy a di erent partial di erential
equation to the two-dimensional liquid jet. Further, the jets are reformulated
in terms of a third order partial di erential equation for the stream
function. The boundary conditions for each jet are unique, but more signi -
cantly these boundary conditions are homogeneous. Due to this homogeneity
the conserved quantities are critical in the solution process.
The conserved quantities for the two-dimensional free and liquid jet are
constructed by rst deriving the conservation laws using the multiplier approach.
The conserved quantity for the two-dimensional free jet is also derived
in terms of the stream function. For a Newtonian
uid with n = 1 the twodimensional
wall jet gives a conservation law. However, this is not the case for
the two-dimensional wall jet for a non-Newtonian power-law
uid.
The various approaches that have been applied in an attempt to derive a
conservation law for the two-dimensional wall jet for a power-law
uid with
n 6= 1 are discussed. In conjunction with the attempt at obtaining conservation
laws for the two-dimensional wall jet we present tenable reasons for its failure,
and a feasible way forward.
Similarity solutions for the two-dimensional free jet have been derived for
both the velocity components as well as for the stream function. The associated
Lie point symmetry approach is also presented for the stream function. A
parametric solution has been obtained for shear thinning
uid free jets for
0 < n < 1 and shear thickening
uid free jets for n > 1. It is observed that for
values of n > 1 in the range 1=2 < n < 1, the velocity pro le extends over a
nite range.
For the two-dimensional liquid jet, along with a similarity solution the
complete Lie point symmetries have been obtained. By associating the Lie
point symmetry with the elementary conserved vector an invariant solution
is found. A parametric solution for the two-dimensional liquid jet is derived
for 1=2 < n < 1. The solution does not exist for n = 1=2 and the range 0 < n < 1=2 requires further investigation.
27
Saad, Tony. "Theoretical Models for Wall Injected Duct Flows." 2010. http://trace.tennessee.edu/utk_graddiss/748.
Повний текст джерелаАнотація:
This dissertation is concerned with the mathematical modeling of the flow in a porous cylinder with a focus on applications to solid rocket motors. After discussing the historical development and major contributions to the understanding of wall injected flows, we present an inviscid rotational model for solid and hybrid rockets with arbitrary headwall injection. Then, we address the problem of pressure integration and find that for a given divergence free velocity field, unless the vorticity transport equation is identically satisfied, one cannot find an analytic expression for the pressure by direct integration of the Navier-Stokes equations. This is followed by the application of a variational procedure to seek novel solutions with varying levels of kinetic energies. These are found to cover a wide spectrum of admissible motions ranging from purely irrotational to highly rotational fields. Subsequently, a second law analysis as well as an extension of Kelvin's energy theorem to open boundaries are presented to verify and corroborate the variational model. Finally, the focus is shifted to address the problem of laminar viscous flow in a porous cylinder with regressing walls. This is tackled using two different analytical techniques, namely, perturbation and decomposition. Comparisons with numerical Runge--Kutta solutions are also provided for a variety of wall Reynolds numbers and wall regression speeds.