To see the other types of publications on this topic, follow the link: Load and flow time.
Dissertations / Theses on the topic 'Load and flow time'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Load and flow time.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Gillam, David A. "Airloads on a finite wing in a time dependent incompressible freestream." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/12371.
Full text
2
Joubert, Adriaan Wolfgang. "Parallel methods for systems of nonlinear equations applied to load flow analysis." Thesis, Queen Mary, University of London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362721.
Full text
3
Macqueen, Christopher Neil. "Time based load-flow analysis and loss costing in electrical distribution systems." Thesis, Durham University, 1994. http://etheses.dur.ac.uk/1700/.
Full text
4
Ansari, Meisam. "REAL-TIME CONGESTION MANAGEMENT IN MODERN DISTRIBUTION SYSTEMS." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/dissertations/1904.
Full textAbstract:
In this research, the problem of real-time congestion management in a modern distribution system with massive active elements such as electric vehicles (EVs), distributed energy resources (DERs), and demand response (DR) is investigated. A novel hierarchical operation and management framework is proposed that can take advantage of the demand side contribution to manage the real-time congestion. There are five main steps in this framework as 1) the aggregators send their demand to the microgrid operators (MGOs), 2) the MGOs send their demand to the distribution system operator (DSO), 3) the DSO detects the congestions and calls the engaged MGOs to reduce their demand, 4) the MGOs update the electricity price to motivate the aggregators to reduce the overall demand, and 5) the DSO dispatches the system according to the finalized demand. The proposed framework is validated on two modified IEEE unbalanced test systems. The results illustrate two congestion cases at t=8:45 am and t=9:30 am in the modified IEEE 13-bus test system, which needs 363kW and 286 kW load reductions, respectively, to be fully addressed. MG#1 and MG#2 are engaged to maintain the 363 kW reduction at t=8:45, and MG#3 and MG#4 are called to reduce their demands by 386 kW at t=9:30 am. The overall interactions can relieve the congested branches. The DSO’s calculations show three congestions at t=1 pm, t=3 pm, and t=9 pm on the IEEE 123-bus test system. These congestion cases can be alleviated by reducing 809 kW, 1177 kW, and 497 kW from the corresponding MGs at t=1 pm, t=3 pm, and t=9 pm, respectively. The second part of the simulation results demonstrates that the proposed real-time data estimator (RDE) can reduce the DSO’s miss-detected congestion cases due to the uncertain data. There are two miss-detected congestions in the IEEE 13-bus test system at t=1:15 pm and t=1:30 pm that can be filtered for t=1:15 pm and minored for t=1:30 pm using the RDE. The proposed RDE can also reduce the miss-detected congestions from 18 cases to four cases in the IEEE 123-bus test system. As a result, the RDE can minimize the extra costs due to the uncertain data. The overall results validate that the proposed framework can adaptively manage real-time congestions in distribution systems.
5
Urquhart, Andrew J. "Accuracy of low voltage electricity distribution network modelling." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/21799.
Full textAbstract:
The connection of high penetrations of new low carbon technologies such as PV and electric vehicles onto the distribution network is expected to cause power quality problems and the thermal capacity of feeder cables may be exceeded. Replacement of existing infrastructure is costly and so feeder cables are likely to be operated close to their hosting capacity. Network operators therefore require accurate simulation models so that new connection requests are not unnecessarily constrained. This work has reviewed recent studies and found a wide range of assumptions and approximations that are used in network models. A number of these have been investigated further, focussing on methods to specify the impedances of the cable, the impacts of harmonics, the time resolution used to model demand and generation, and assumptions regarding the connectivity of the neutral and ground conductors. The calculation of cable impedances is key to the accuracy of network models but only limited data is available from design standards or manufacturers. Several techniques have been compared in this work to provide guidance on the level of detail that should be included in the impedance model. Network modelling results with accurate impedances are shown to differ from those using published data. The demand data time resolution has been shown to affect estimates of copper losses in network cables. Using analytical methods and simulations, the relationship between errors in the loss estimates and the time resolution has been demonstrated and a method proposed such that the accuracy of loss estimates can be improved. For networks with grounded neutral conductors, accurate modelling requires the resistance of grounding electrodes to be taken into account. Existing methods either make approximations to the equivalent circuit or suffer from convergence problems. A new method has been proposed which resolves these difficulties and allows realistic scenarios with both grounded and ungrounded nodes to be modelled. In addition to the development of models, the voltages and currents in a section of LV feeder cable have been measured. The results provide a validation of the impedance calculations and also highlight practical difficulties associated with comparing simulation models with real measurement results.
6
Widén, Joakim. "System Studies and Simulations of Distributed Photovoltaics in Sweden." Doctoral thesis, Uppsala universitet, Fasta tillståndets fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132907.
Full textAbstract:
Grid-connected photovoltaic (PV) capacity is increasing worldwide, mainly due to extensive subsidy schemes for renewable electricity generation. A majority of newly installed systems are distributed small-scale systems located in distribution grids, often at residential customers. Recent developments suggest that such distributed PV generation (PV-DG) could gain more interest in Sweden in the near future. With prospects of decreasing system prices, an extensive integration does not seem impossible. In this PhD thesis the opportunities for utilisation of on-site PV generation and the consequences of a widespread introduction are studied. The specific aims are to improve modelling of residential electricity demand to provide a basis for simulations, to study load matching and grid interaction of on-site PV and to add to the understanding of power system impacts. Time-use data (TUD) provided a realistic basis for residential load modelling. Both a deterministic and a stochastic approach for generating different types of end-use profiles were developed. The models are capable of realistically reproducing important electric load properties such as diurnal and seasonal variations, short time-scale fluctuations and random load coincidence. The load matching capability of residential on-site PV was found to be low by default but possible to improve to some extent by different measures. Net metering reduces the economic effects of the mismatch and has a decisive impact on the production value and on the system sizes that are reasonable to install for a small-scale producer. Impacts of large-scale PV-DG on low-voltage (LV) grids and on the national power system were studied. Power flow studies showed that voltage rise in LV grids is not a limiting factor for integration of PV-DG. Variability and correlations with large-scale wind power were determined using a scenario for large-scale building-mounted PV. Profound impacts on the power system were found only for the most extreme scenarios.Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 711
7
Goyal, Sachin. "Power network in the loop : subsystem testing using a switching amplifier." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/26521/1/Sachin_Goyal_Thesis.pdf.
Full textAbstract:
“Hardware in the Loop” (HIL) testing is widely used in the automotive industry. The sophisticated electronic control units used for vehicle control are usually tested and evaluated using HIL-simulations. The HIL increases the degree of realistic testing of any system. Moreover, it helps in designing the structure and control of the system under test so that it works effectively in the situations that will be encountered in the system. Due to the size and the complexity of interaction within a power network, most research is based on pure simulation. To validate the performance of physical generator or protection system, most testing is constrained to very simple power network. This research, however, examines a method to test power system hardware within a complex virtual environment using the concept of the HIL. The HIL testing for electronic control units and power systems protection device can be easily performed at signal level. But performance of power systems equipments, such as distributed generation systems can not be evaluated at signal level using HIL testing. The HIL testing for power systems equipments is termed here as ‘Power Network in the Loop’ (PNIL). PNIL testing can only be performed at power level and requires a power amplifier that can amplify the simulation signal to the power level. A power network is divided in two parts. One part represents the Power Network Under Test (PNUT) and the other part represents the rest of the complex network. The complex network is simulated in real time simulator (RTS) while the PNUT is connected to the Voltage Source Converter (VSC) based power amplifier. Two way interaction between the simulator and amplifier is performed using analog to digital (A/D) and digital to analog (D/A) converters. The power amplifier amplifies the current or voltage signal of simulator to the power level and establishes the power level interaction between RTS and PNUT. In the first part of this thesis, design and control of a VSC based power amplifier that can amplify a broadband voltage signal is presented. A new Hybrid Discontinuous Control method is proposed for the amplifier. This amplifier can be used for several power systems applications. In the first part of the thesis, use of this amplifier in DSTATCOM and UPS applications are presented. In the later part of this thesis the solution of network in the loop testing with the help of this amplifier is reported. The experimental setup for PNIL testing is built in the laboratory of Queensland University of Technology and the feasibility of PNIL testing has been evaluated using the experimental studies. In the last section of this thesis a universal load with power regenerative capability is designed. This universal load is used to test the DG system using PNIL concepts. This thesis is composed of published/submitted papers that form the chapters in this dissertation. Each paper has been published or submitted during the period of candidature. Chapter 1 integrates all the papers to provide a coherent view of wide bandwidth switching amplifier and its used in different power systems applications specially for the solution of power systems testing using PNIL.
8
Goyal, Sachin. "Power network in the loop : subsystem testing using a switching amplifier." Queensland University of Technology, 2009. http://eprints.qut.edu.au/26521/.
Full textAbstract:
“Hardware in the Loop” (HIL) testing is widely used in the automotive industry. The sophisticated electronic control units used for vehicle control are usually tested and evaluated using HIL-simulations. The HIL increases the degree of realistic testing of any system. Moreover, it helps in designing the structure and control of the system under test so that it works effectively in the situations that will be encountered in the system. Due to the size and the complexity of interaction within a power network, most research is based on pure simulation. To validate the performance of physical generator or protection system, most testing is constrained to very simple power network. This research, however, examines a method to test power system hardware within a complex virtual environment using the concept of the HIL. The HIL testing for electronic control units and power systems protection device can be easily performed at signal level. But performance of power systems equipments, such as distributed generation systems can not be evaluated at signal level using HIL testing. The HIL testing for power systems equipments is termed here as ‘Power Network in the Loop’ (PNIL). PNIL testing can only be performed at power level and requires a power amplifier that can amplify the simulation signal to the power level. A power network is divided in two parts. One part represents the Power Network Under Test (PNUT) and the other part represents the rest of the complex network. The complex network is simulated in real time simulator (RTS) while the PNUT is connected to the Voltage Source Converter (VSC) based power amplifier. Two way interaction between the simulator and amplifier is performed using analog to digital (A/D) and digital to analog (D/A) converters. The power amplifier amplifies the current or voltage signal of simulator to the power level and establishes the power level interaction between RTS and PNUT. In the first part of this thesis, design and control of a VSC based power amplifier that can amplify a broadband voltage signal is presented. A new Hybrid Discontinuous Control method is proposed for the amplifier. This amplifier can be used for several power systems applications. In the first part of the thesis, use of this amplifier in DSTATCOM and UPS applications are presented. In the later part of this thesis the solution of network in the loop testing with the help of this amplifier is reported. The experimental setup for PNIL testing is built in the laboratory of Queensland University of Technology and the feasibility of PNIL testing has been evaluated using the experimental studies. In the last section of this thesis a universal load with power regenerative capability is designed. This universal load is used to test the DG system using PNIL concepts. This thesis is composed of published/submitted papers that form the chapters in this dissertation. Each paper has been published or submitted during the period of candidature. Chapter 1 integrates all the papers to provide a coherent view of wide bandwidth switching amplifier and its used in different power systems applications specially for the solution of power systems testing using PNIL.
9
Saeidpour, Parizy Ehsan. "Electrical Energy Retail Price Optimization for an Interconnected/Islanded Power Grid." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1512463830323059.
Full text
10
Ciereszko, Tomasz. "Advanced probabilistic load flow." Master's thesis, Universidade de Aveiro, 2012. http://hdl.handle.net/10773/10204.
Full textAbstract:
Mestrado em Engenharia Electrónica e TelecomunicaçõesThis thesis sets forth a computational framework of probabilistic load flow analysis taking into consideration of high penetration of variable energy resources, such as the wind generation. The framework enables a faster and more precise estimation of the impact of variable energy resources in load flow analysis. This thesis consists of six chapters: introduction, probabilistic load flow algorithms, computer program for PLF calculations, conclusion and future work, appendices and reference. The second part contains the mathematical development of the framework based on Sequence Operation Theory newly established. The formulation is novel in that it provides an improved computational alternative to the existing simulation based frameworks. The third part contains information about program written in Fortran 90/95 environment like format of reading data etc. Include the studies based on the standard IEEE 9-bus system. Data obtained as a result of program’s work in debugging process are compared with manual calculations for the same network to check if the program is working in proper way. Moreover comprise the results obtained in the program for largest tested network 96-RTS (24 buses). Appendices include content of two input files (random generation, system configuration for 96-RTS) and intermediate result calculated for the 24-bus system.
Esta dissertação descreve parte do desenvolvimento de uma aplicação de software para calcular o fluxo de potência em sistemas de redes elétricas usando métodos probabilísticos, considerando o caso da existência de geradores com produção fortemente variável, como acontece nas quintas eólicas. A dissertação está dividida em seis capítulos: introdução, algoritmos de fluxo de potência probabilísticos, desenvolvimento do código, conclusão, apêndices e referências. A segunda parte é constituída pelo desenvolvimento matemático do método utilizado, que foi recentemente criado apresentando uma alternativa mais eficiente às tradicionais. A Terceira parte contem informação sobre a o programa criado para implementar o algoritmo e seu teste, nomeadamente o desempenho na análise do standard IEEE 96-RTS (24 - bus system). Os apêndices incluem o conteúdo dos ficheiros de entrada e resultados intermédios para debug da solução apresentada.
Praca przedstawia probabilistyczną metodę do obliczania przepływów mocy w sieci energetycznej z szczególnym uwzględnieniem zmiennych źródeł energii takich jak generacja wiatrowa. Prezentowane podejście umożliwia szybsze i bardziej precyzyjne oszacowanie zmiennych zasobów energetycznych w analizie rozpływów mocy. Dokument został podzielony na sześć następujących części: wstęp, algorytm probabilistic load flow, program komputerowy, podsumowanie i możliwośći rowoju projektu, dodatki, bibliografia. Druga część pracy zawiera założenia metody Sequence Operation Theory (SOT). Prezentowany algorytm jest nowy i stanowi alternatywę dla dotychczasowo stosowanych metod. Część trzecia opisuje program komputerowy z zaimplementowaną metodą SOT stworzony na potrzeby tej pracy. Kod programu został napisany w środowisku Fortran 90/95. Rozdział zawiera badania oparte na systemie sieci energetycznej 9 magistral w celu sprawdzenia poprawności działania kodu. Ponadto w tej części zostały zaprezentowane wyniki działania aplikacji dla systemu testowego 96-RTS (24 magistral). W dodatkach zaprezentowano zawartość dwóch plików wejściowych: konfigurację systemu testowego 96-RTS i wartości generacji dla zmiennego źródła oraz pośrednie wyniki obliczeniowe dla tego systemu.
11
Oiveira, Clovis Bosco Mendon?a. "T?cnicas de simplifica??o de redes e otimiza??o multiobjetivo para an?lise de varia??es de tens?o em regime permanente provocadas por parques e?licos integrados ao sistema el?trico." Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/15142.
Full textAbstract:
Made available in DSpace on 2014-12-17T14:54:54Z (GMT). No. of bitstreams: 1
ClovisBMO_TESE_1_a_75.pdf: 2549651 bytes, checksum: d03d835bba88763c08a8cb99eac15cd8 (MD5)
Previous issue date: 2010-03-12Universidade Federal do Rio Grande do Norte
This study presents a description of the development model of a representation of simplified grid applied in hybrid load flow for calculation of the voltage variations in a steady-state caused by the wind farm on power system. Also, it proposes an optimal load-flow able to control power factor on connection bar and to minimize the loss. The analysis process on system, led by the wind producer, it has as base given technician supplied by the grid. So, the propose model to the simplification of the grid that allows the necessity of some knowledge only about the data referring the internal network, that is, the part of the network that interests in the analysis. In this way, it is intended to supply forms for the auxiliary in the systematization of the relations between the sector agents. The model for simplified network proposed identifies the internal network, external network and the buses of boulders from a study of vulnerability of the network, attributing them floating liquid powers attributing slack models. It was opted to apply the presented model in Newton-Raphson and a hybrid load flow, composed by The Gauss-Seidel method Zbarra and Summation Power. Finally, presents the results obtained to a developed computational environment of SCILAB and FORTRAN, with their respective analysis and conclusion, comparing them with the ANAREDE
Este trabalho apresenta uma descri??o do desenvolvimento de modelo para representa??o de rede simplificada aplicado em fluxo de carga h?brido para c?lculo das varia??es de tens?o em regime permanente provocadas pela conex?o de aerogeradores na rede el?trica. Al?m disso, se apresenta um fluxo de carga ?timo capaz de controlar remotamente o fator de pot?ncia na barra de conex?o e minimizar perdas. O princ?pio do processo de an?lise do sistema, conduzido pelo acessante, tem como base dados t?cnicos fornecidos pela rede acessada. Assim, se prop?e um modelo para simplifica??o de redes que permita a necessidade do conhecimento apenas dos dados referente a rede interna, ou seja, a parcela da rede de interesse para an?lise. Dessa forma, pretende-se fornecer meios para auxiliar na sistematiza??o das rela??es entre concession?ria e acessante. O modelo para simplifica??o de rede proposto identifica a rede interna, rede externa e as barras de fronteira a partir de dados provenientes de um estudo de vulnerabilidade da rede, atribuindo-as pot?ncias l?quidas flutuantes, ou seja, modelando-as como barras slack. Aplica-se o referido modelo no fluxo de carga Newton-Raphson e em um fluxo de carga h?brido, composto pelos m?todos de Gauss Seidel Zbarra e Soma de Pot?ncias. Ao final, apresentam-se os resultados obtidos por um ambiente computacional desenvolvido do SCILAB e FORTRAN, com suas respectivas an?lises e conclus?es, comparando-os com o ANAREDE
12
Khosravi-Dehkordi, Iman. "Load flow feasibility under extreme contingencies." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100252.
Full textAbstract:
This thesis examines the problem of load flow feasibility, in other words, the conditions under which a power network characterized by the load flow equations has a steady-state solution. In this thesis, we are particularly interested in load flow feasibility in the presence of extreme contingencies such as the outage of several transmission lines.Denoting the load flow equations by z = f(x) where z is the vector of specified injections (the real and reactive bus demands, the specified real power bus generations and the specified bus voltage levels), the question addressed is whether there exists a real solution x to z = f( x) where x is the vector of unknown bus voltage magnitudes at load buses and unknown bus voltage phase angles at all buses but the reference bus. Attacking this problem via conventional load flow algorithms has a major drawback, principally the fact that such algorithms do not converge when the load flow injections z define or are close to defining an infeasible load flow. In such cases, lack of convergence may be due to load flow infeasibility or simply to the ill-conditioning of the load flow Jacobian matrix.
This thesis therefore makes use of the method of supporting hyperplanes to characterize the load flow feasibility region, defined as the set the injections z for which there exists a real solution x to the load flow equations. Supporting hyperplanes allow us to calculate the so-called load flow feasibility margin, which determines whether a given injection is feasible or not as well as measuring how close the injection is to the feasibility boundary. This requires solving a generalized eigenvalue problem and a corresponding optimization for the closest feasible boundary point to the given injection.
The effect of extreme network contingencies on the feasibility of a given injection is examined for two main cases: those contingencies that affect the feasibility region such as line outages and those that change the given injection itself such as an increase in VAR demand or the loss of a generator. The results show that the hyperplane method is a powerful tool for analyzing the effect of extreme contingencies on the feasibility of a power network.
13
Ricker, Timothy J. Cowan Nelson. "Cognitive load and time based forgetting." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6470.
Full textAbstract:
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 18, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Thesis advisor: Dr. Nelson Cowan. Includes bibliographical references.
14
Rashid, Asim. "Harmonic load flow formulation and numerical resolution." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/665013.
Full textAbstract:
As a continuation of the work done by the QSE (Electrical Supply Quality) research group at the UPC (Polytechnic University of Catalonia) on harmonic load flow in electric power networks, this thesis aims to study existing harmonic load flow formulations, as well as the numerical resolution of the nonlinear equation systems derived from these formulations, in order to propose improvements for the former and compare performances of numerical methods for the latter. The improvements in the harmonic load flow formulations are related to a reduction in the number of iterations, for which an improved formulation is proposed. The comparison of numerical resolution methods is focused on analysing harmonic load flow formulation convergences and accuracies. The specific goals of the thesis are: (1) To propose an improved formulation for the harmonic load flow problem. This formulation should be applicable to electrical networks with highly distorted voltages. (2) To analyse the numerical resolution of all the considered harmonic load flow formulations (existing and improved) in terms of convergence and accuracy, by using a well-known numerical method (Newton-Raphson) and an alternative numerical method (Levenberg-Marquardt).
15
Xu, Wenyuan. "A multiphase harmonic load flow solution technique." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31035.
Full textAbstract:
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
16
SOARES, SERGIO MARINHO. "PROBABILISTC LOAD FLOW WITH ANALYSIS OF CONTINGENCIES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1985. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9809@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORO fluxo de potência probabilístico é considerado uma técnica eficiente na obtenção de índices de adequação, tais como: probabilidade do fluxo em uma linha ou em um transformador ser maior do que sua capacidade nominal, probabilidade da magnitude da tensão em um barramento estar fora dos limites usuais de operacio, etc., os quais são medidas extremamente úteis tanto no planejamento como na operação de sistemas de potência. Estes índices são obtidos dada a capacidade de tal algoritmo considerar a natureza probabilística das cargas, geração e da configuração da rede em uma única solução. Vários trabalhos tem sido propostos para resolver probabilisticamente o problema do fluxo de potência. A grande maioria tem considerado somente as incertezas nos dados de carga e geração, modelando a rede elétrica por uma configuração fixa, relativa ao caso base. A influência das incertezas na configuração de uma rede de potência devido à natureza probabilística das contingências de seus elementos foi, até então, muito pouco analisada. Esta tese apresenta um novo método de obtenção para a solução do fluxo de potência probabilístico quando a rede é modelada como uma variável aleatória. O algoritmo proposto é aplicado a um sistema típico e os resultados discutidos
Probabilistic load flow can be considered na efficient tecnnique in order to assess adequacy indices, such as: the probability of a transmission line or transformer flow being greater than its thermal rating, probability of a busbar voltage being outside its operational constraints, etc., which are extremely useful measurements in planning and operation of power systems. These indices are achieved due to the ability of such algorithm in recognising the probabilistic nature of load, generation and network configuration within one solution. Many tecniques have been proposed in order to solve the load flow problem probabilisticaly. The great majorit have aonly accounted for load and generation data uncertainties and therefore the network configuration has been considered fixed. So far, the effects of the configuration uncertainties due to the probabilistic nature of network contingencies have not been deeply analysed. This thesis presents a new method for obtaining a probabilistic load flow solution whe network outages are modelled as a random variable. The proposed technique is applied to a typical power system and the results discussed.
17
El-Khatib, Khalil M. "Dynamic load balancing for clustered time warp." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape16/PQDD_0003/MQ29686.pdf.
Full text
18
Soon, Wilson Wei-Chwen. "Near real-time extract, transform and load." [Denver, Colo.] : Regis University, 2007. http://165.236.235.140/lib/WSoon2007.pdf.
Full text
19
El-Khatib, Khalil M. "Dynamic load balancing for clustered time warp." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=27311.
Full textAbstract:
In this thesis, we consider the problem of dynamic load balancing for parallel discrete event simulation. We focus on the optimistic synchronization protocol, Time Warp.A distributed load balancing algorithm was developed, which makes use of the active process migration in Clustered Time Warp. Clustered Time Warp is a hybrid synchronization protocol; it uses an optimistic approach between the clusters and a sequential approach within the clusters. As opposed to the centralized algorithm developed by H. Avril for Clustered Time Warp, the presented load balancing algorithm is a distributed token-passing one.
We present two metrics for measuring the load: processor utilization and processor advance simulation rate. Different models were simulated and tested: VLSI models and queuing network models (pipeline and distributed networks). Results show that improving the performance of the system depends a great deal on the nature of the simulated model.
For the VLSI model, we also examined the effect of the dynamic load balancing algorithm on the total number of processed messages per unit time. Performance results show that dynamically balancing the load, the throughput of the simulation was improved by more than 100%.
20
Ghosh, Sushmita. "Real time data acquisition for load management." Thesis, Virginia Tech, 1985. http://hdl.handle.net/10919/45726.
Full textAbstract:
Demand for Data Transfer between computers has increased ever since the introduction of Personal Computers (PC). Data Communicating on the Personal Computer is much more productive as it is an intelligent terminal that can connect to various hosts on the same I/O hardware circuit as well as execute processes on its own as an isolated system.
Yet, the PC on its own is useless for data communication. It requires a hardware interface circuit and software for controlling the handshaking signals and setting up communication parameters. Often the data is distorted due to noise in the line. Such transmission errors are imbedded in the data and require careful filtering.
The thesis deals with the development of a Data Acquisition system that collects real time load and weather data and stores them as historical database for use in a load forecast algorithm in a load management system. A filtering technique has been developed here that checks for transmission errors in the raw data. The microcomputers used in this development are the IBM PC/XT and the AT&T 3B2 supermicro computer.Master of Science
21
Huang, Simon. "Load time optimization of JavaScript web applications." Thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17931.
Full textAbstract:
Background. Websites are getting larger in size each year, the median size increased from 1479.6 kilobytes to 1699.0 kilobytes on the desktop and 1334.3 kilobytes to 1524.1 kilobytes on the mobile. There are several methods that can be used to decrease the size. In my experiment I use the methods tree shaking, code splitting, gzip, bundling, and minification. Objectives. I will investigate how using the methods separately affect the loading time and con- duct a survey targeted at participants that works as JavaScript developers in the field. Methods. I have used Vue for creating a website and ran Lighthouse tests against the website. All this within two Docker containers to make the reproducibility easier. Interviews with JavaScript developers were made to find out if they use these methods in their work. Results. The best result would be to use all of the methods; gzip, minification, tree shaking, code splitting, and bundling in a combination. If gzip is the only option available for the developer to use, we can see around 60% decrease in loading time. The inter- views showed that most developers did not use or did not know of tree shaking and code splitting. Some frameworks have these methods built in to work automatically, therefor the developers does not know that it is being utilized. Conclusions. Since tree shaking and code splitting are two relatively new techniques, there is not much scientific measured values available. From the results, we can give the conclusion that using all of the mentioned methods will give the best result in loading time. All of the methods will affect the loading time, and only using gzip will affect it with a 60% decrease.
22
Herbig, Arnim. "On load flow control in electric power systems." Doctoral thesis, KTH, Electric Power Systems, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2919.
Full text
23
Toussaint, Margaret. "An analytical study of the load flow problem." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=22680.
Full textAbstract:
Some analytical properties of the load flow problem are examined in this work. In order to facilitate this, the load flow equations are expressed in rectangular co-ordinates.Each load flow equation is formulated as a fully quadratic form and the nature of these quadratic forms is studied in detail. The eigenvalues and eigenvectors of the matrix in each equation are derived and their significance to the nature and existence of load flow solutions is discussed.
An experimental study is also done on the load flow feasibility region which is defined, in the space of net real and reactive powers as well as the voltage magnitudes squared, for a general power network. The network is assumed to consist of a slack bus, voltage control buses and load buses. This region is characterised by all injections for which there is a real voltage solution to the load flow equations. The geometric nature of the region and its relationship to the number of load flow solutions are examined.
24
Reynolds, Mark Andrew. "Load-sensitive fluid-flow through fracture-matrix systems." Thesis, Heriot-Watt University, 2004. http://hdl.handle.net/10399/354.
Full text
25
SILVA, HELIO FRANCISCO DA. "ON ADDRESSING IRREGULARITIES IN ELECTRICITY LOAD TIME-SERIES AND SHORT TERM LOAD FORECASTING." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2001. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1737@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORAs alterações na legislação do Setor de Energia Elétrica Brasileiro em fins do milênio passado, provocou profundas mudanças no planejamento da Operação do Sistema e na Comercialização de energia elétrica no Brasil. O desmembramento das atividades de geração, de transmissão e de distribuição de energia elétrica criou novas características no comportamento dos Agentes Concessionários e as previsões de demanda por energia elétrica, que sempre foram ferramenta importante, por exemplo, na programação da operação, passaram a ser indispensáveis também, na comercialização de energia elétrica no mercado livre. Neste novo cenário, a obtenção e o armazenamento de dados confiáveis passou a ser parte integrante do patrimônio das Empresas e um sistema eficiente de previsões de carga passou a ser um diferencial na mesa de negociações. Os Agentes concessionários e o Operador Nacional do Sistema Elétrico vêm fazendo investimentos para aperfeiçoar os seus sistemas de aquisição de dados, entretanto em sistemas de multipontos algumas falhas imprevistas durante a sincronização da telemedição podem ocorrer, provocando defeitos nas séries. Nas séries de minuto em minuto, por exemplo, uma falha de algumas horas acarreta centenas de registros defeituosos e as principais publicações a respeito de modelagens de séries temporais para tratamento de dados não abordam as dificuldades encontradas diante de grandes falhas consecutivas nos dados.
As a result of the continuing privatization process within the energy sector,electricity load forecasting is a ritical tool for decision-making in the Industry. Reliable forecasts are now needed not only for developing strategies for business planning and short term operational scheduling, but also to define the spot market electricity price. The forecasting process is data-ntensive and interest has been driven to shorter and shorter intervals. Large investments are being made in modernizing and improving metering systems, so as to make more data available to the forecaster. However, the forecaster is still faced with irregular time-series. Gaps, missing values, spurious information or repeated values in the time-series can result from transmission errors or small failures in the recording process. These so- called irregularities have led to research that focused on either iterative processes,like the Kalman filter and the EM algorithm, or applications of the statistical literature on treatment of missing values and outliers. Nevertheless, these methods often result in large forecast errors when confronted with consecutive failures in the data. On the other hand, the minute to minute series have a large amount of points and so the one day ahead forecast horizont becomes very large to handling with the conventional methods. In this context, we propose an alternative to detect and replace values and present a methodology to perform the forecasting process by using of other information in the time-series that relate to the variability and seasonality, which are commonly encountered in electricity load-forecasting data. We illustrate the method and address the problem as part of a wider project that aims at the development of an automatic on line system for tracking the Brazilian Interlinked Electric Network Operation and performing short term load forecasting. The data were collected by ONS / ELETROBRAS - Brazil. We concentrate on 10 minutes data for the years 1997-1999 of Light Serviços de Eletricidade S.A. (Rio de Janeiro and its surroundings).
Las alteraciones en la legislación del Sector de Energía Elétrica Brasilero a finales del milenio pasado, provocó profundos cambios en el planificación de la Operación del Sistema y en la Comercialización de energía eléctrica en Brasil. La desarticulación de las actividades de generación, de transmisión y de distribuición de energía eléctrica creó nuevas características en el comportamiento de los Agentes Concesionarios. Así, las previsiones de demanda por energía eléctrica, que siempre fueron una herramienta importante, por ejemplo, en la programación de la operación, pasaron a ser indispensables también en la comercialización de energía eléctrica en el mercado libre. En este nuevo escenario, la obtención y almacenamiento de datos confiables pasó a ser parte integrante del patrimonio de las Empresas y un sistema eficiente de previsiones de carga constituye un diferencial en la mesa de negociaciones. Los Agentes concesionarios y el Operador Nacional del Sistema Eléctrico han invertido en el perfeccionamiento de sus sistemas de adquisición de datos. Sin embargo, en sistemas de multipuntos algunas fallas imprevistas durante la sincronización de la telemedición pueden ocurrir, provocando defectos en las series. En las series de minuto en minuto, por ejemplo, una falla de algunas horas trae consigo centenas de registros defectuosos y las principales publicaciones sobre modelos de series temporales para tratamiento de datos no abordan las dificuldades encontradas frente a grandes fallas consecutivas en los datos.
26
Assaf, Hamed. "Real-time flow forecasting." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/30815.
Full textAbstract:
The main objective of this research is to develop techniques for updating deterministic river flow forecasts using feedback of real-time (on-line) flow and snowpack data. To meet this objective, previous updating methods have been reviewed and evaluated and typical error patterns in flow forecasts have been analyzed using standard techniques. In addition, a new criterion based on the coefficient of determination and coefficient of efficiency has been introduced to evaluate systematic errors in flow forecasts. Moreover, lagged linear regression has been suggested as a method for detecting and estimating timing errors.
Arising from this initial work, two different updating procedures have been developed. Further work has shown that these two independent procedures can be usefully combined, leading to yet further improvement of forecast. Arising from these methods, two other additional approaches have been formulated, one for correcting timing errors and one for updating snowpack estimation parameters from flow measurements.
The first of the updating methods consists of a flow updating model which was developed
to update the flow forecasts of the UBC watershed model using the most recent flow measurement. The updating process is achieved using the Kalman filter technique. The performance of the updating model is mainly controlled by the relative values of two parameters of the Kalman filter technique: the measurement variance and the state variance. It is found that the measurement variance is best selected as the square of a percentage of the flow. The updating model has been applied on the Illecillewaet river basin in British Columbia. A significant improvement in flow forecasts has been observed.
The second method has been developed to update parameters of an energy budget
snowpack model using on-line snowpack measurements. The updating procedure is based on calculating the value of a snowpack parameter that yields a perfect correspondence between measured and calculated snowpacks. The updated value is then used in the snowpack model to enhance its future forecasts with feedback from previous snowpack measurements. The snowmelts generated by the updated snowpack model are then routed to produce flow forecasts. Applying this model on the snowpack measured at Mt. Fidelity in the upper Columbia River Basin in British Columbia showed that both the snowpack forecasts and the flow forecasts generated from these updated snowpack forecasts were greatly improved.
Because the above two updating methods operate independently, they can be applied in combination whenever an appropriate measurement is available. The combined use of these two methods to data from the Illecillewaet river basin showed an additional improvement in flow forecasts.
As a further development, the snowpack estimation model has been adapted so that a Kalman filter approach can be used to update snowpack estimation parameters from flow measurements.
It is finally concluded that flow forecast updating requires the application of several methods, rather than one simple approach, because errors arise from various sources. In addition, updating procedures may prove useful in achieving a better calibration for watershed models.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
27
Zimmerman, Nicole P. "Time-Variant Load Models of Electric Vehicle Chargers." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2297.
Full textAbstract:
In power distribution system planning, it is essential to understand the impacts that electric vehicles (EVs), and the non-linear, time-variant loading profiles associated with their charging units, may have on power distribution networks. This research presents a design methodology for the creation of both analytical and behavioral models for EV charging units within a VHDL-AMS simulation environment.
Voltage and current data collected from Electric Avenue, located on the Portland State University campus, were used to create harmonic profiles of the EV charging units at the site. From these profiles, generalized models for both single-phase (Level 2) and three-phase (Level 3) EV chargers were created. Further, these models were validated within a larger system context utilizing the IEEE 13-bus distribution test feeder system.
Results from the model's validation are presented for various charger and power system configurations. Finally, an online tool that was created for use by distribution system designers is presented. This tool can aid designers in assessing the impacts that EV chargers have on electrical assets, and assist with the appropriate selection of transformers, conductor ampacities, and protection equipment & settings.
28
Wong, Yuk-Chiu Jack. "An interactive load flow program for underground electrical system." Ohio : Ohio University, 1988. http://www.ohiolink.edu/etd/view.cgi?ohiou1182875190.
Full text
29
Oke, Oluwabukola A. "Enhanced unscented transform method for probabilistic load flow studies." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/14040/.
Full textAbstract:
The advent of deregulated electricity and the call for sustainable energy practices are major drivers for the continued increase of renewable energy systems within the modern day power network. Dominant among them is the wind energy system whose output is uncertain because of its dependence on the prevailing climatic conditions. This increases the level of uncertainty witnessed within the power system as such, as the penetration of renewable energy systems continue to increase, their effects cannot be trivialised. Probabilistic load flow (PLF) is employed by power system analysts to account for the effect of uncertainty within the power network. The common technique which is based on Monte Carlo Simulation (MCS), though accurate is very time consuming and for large systems it becomes unwieldy. Alternative approaches with the advantages of the MCS method but with reduced computational burden are required. A viable alternative method should therefore require minimum computational time and burden, be able to accurately model various network uncertainties, be applicable to practical small and large systems, be able to account for the effect of dependency among network variables and possess good overall accuracy. This thesis proposes a novel approximate approach referred to as the enhanced unscented transform method to meet the requirements of PLF. The method combines the Gaussian quadrature method and the Stieljes procedure with dimension reduction technique in deciding estimation points while the Cholesky decomposition is incorporated to account for the effect of dependency. The performance of the proposed technique is demonstrated using modified IEEE 6, 14, and 118 test systems and a practical distribution test system all incorporating wind farms. Results obtained for numerous scenarios show a good match between the proposed method and the MCS method but with significant computational burden saving. The performance of the method is also shown to compare favourably with other existing PLF methods.
30
Ellis, Mikle Val. "The ladder load-flow method extended to distribution networks." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/39138.
Full textAbstract:
The rigorous load-flow analysis of Distribution Networks requires the modeling of mutual coupling, multiphase possibilities and unbalanced loading. The Ladder Load-Flow Method meets these requirements, but is limited to radial systems. The Switch Compensation Method presented here, extends the Ladder Load-Flow Method to solve Distribution Networks. A network analysis program has been developed using the Electric Power Research Distribution Engineering Workstation (DEWorkstation). The program uses the pointers provided by the DEWorkstation to represent the connectivity of the system. The use of these pointers increases the speed of execution while naturally handling the sparsity of the system. The user is also provided with "on line" attribute and topological data maintenance. The extension technique is based on Thevenin's Theorem. This approach allows the accurate determination of the equivalent impedance for networks which contain series and shunt elements. The equivalent impedance can be changed during the iterative solution process. This allows the algorithm to simulate the operation of control devices which significantly alter the impedance of the network. A transformer model for the forward and reverse trace of the Ladder Method is also presented.Ph. D.
31
Amira, Sihem. "Electrical power system load flow using a distributed array processor." Thesis, Queen Mary, University of London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267799.
Full text
32
POMA, CARLOS ENRIQUE PORTUGAL. "AN ITERATIVE SOLVER FOR LINEAR-SYSTEMS: APPLICATION IN LOAD FLOW." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=17554@1.
Full textAbstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREste trabalho desenvolve um solucionador iterativo baseado no método Resíduo Mínimo Generalizado (GMRES) para solucionar o subproblema linear do problema de fluxo de carga, com destaque para cenários de difícil convergência. O solucionador agrega uma estratégia de reordenamento para minimização do número total de novos elementos não-nulos e um pré-condicionador baseado no algoritmo de Doolittle, com regra de preenchimento de elementos não-nulos baseada no erro resultante. O solucionador foi implementado em um programa computacional de fluxo de carga, a fim de se verificar sua robustez e eficiência em diversos sistemas-teste e diferentes condições de operação. Também é proposto um método para o ajuste dos parâmetros dos solucionadores iterativos, que permite identificar intervalos de valores permissíveis para cada um dos parâmetros, identificando os mais adequados, visando garantir a robustez e melhorar o desempenho do solucionador.
This work develops an iterative solver based on Generalized Minimal Residual method (GMRES) to solve the load flow linear subproblem, especially in scenarios of difficult convergence. The solver combines a reordering strategy to minimise the total number of fill-in terms and a preconditioning strategy based on the Doolittle algorithm with a fill-in dropping strategy based on the resulting error. The solver was implemented into a computational load flow program in order to verify its robustness and efficiency in several test-systems and different operating conditions. It is also proposed a method for adjusting the iterative solver parameters, the method is able to identify intervals of permissible values for each parameter, identifying the most appropriate in order to ensure the robustness and improve the solver performance.
33
Houde, Sébastien. "Analysis of the part-load and speed-no-load flow dynamics in a model propeller hydraulic turbine." Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/29823.
Full textAbstract:
Les turbines hydrauliques sont devenues un atout important pour la régulation de la puissance sur les réseaux électriques. Cependant, les scénarios de régulation de puissance exigent que les turbines fonctionnent loin de leurs points d'opération optimale, dans des régions où de grandes uctuations de pression peuvent affecter l'intégrité structurale de la turbine. Cette thèse présente des contributions a l'etude de l'hydrodynamique de l'écoulement dans une turbine helice modele fonctionnant dans des conditions de charge partielle et de vitesse-sans-charge. À charge partielle, les fluctuations de pression principales sont associées à un vortex cavitant. Des mesures provenant de Vélocimétrie par Imagerie de Particules (PIV) couplées à des techniques de fluorescence induite par laser et d'ombroscopie ont été utilisées pour reconstruire l'interface eau-vapeur et identier l'origine de fluctuations aectant la précision des mesures de PIV moyennées en phase. De plus, des capteurs de pression miniatures incorporés dans deux aubes de la roue ainsi que des jauges de deformation montées sur les aubes ont fourni des données pour quantier l'impact du vortex de charge partielle sur la turbine. Cette thèse présente également l'une des premieres etudes detaillees sur les conditions transitoires et sans charge dans une turbine modèle. Les capteurs de pression et de déformation sur les aubes ont ete utilisés pour identier les instabilités dominantes dans des conditions de vitesse sans charge et d'emballement. Des simulations basées sur la technologie Scale Adaptive Simulations (SAS) de la condition de vitesse-sans-charge ont été utilisés pour étudier un décrochage tournant dans la roue. Des simulations sans les aubes indiquent que le décrochage tournant est associé à une couche cisaillée provenant d'une recirculation autour du moyeu de la roue et d'une séparation de la couche limite sur le fond supérieur.Hydraulic turbines have become an important asset to provide power regulation on electrical grids. However, power-regulation scenarios require turbines to operate far from their best eciency conditions, in regions where large pressure uctuations aect the turbine structural integrity. This is particularly acute for xed blade reaction turbines such as propeller units. This thesis presents contributions to the study of the hydrodynamics of the ow in a model propeller turbine operating in part-load and speed-no-load conditions. In part load, the main pressure uctuations are associated with the part-load vortex. Data from Particle Image Velocimetry (PIV), coupled to Laser Induced Fluorescence and shadowgraphy techniques, were used to reconstruct the water-vapour interface and to identify the origin of uctuations aecting the precision of the phase-averaged PIV measurements. Furthermore, miniature pressure transducers imbedded in two runner blades and strain gages at the blade roots provided data to quantify the impact of the part load vortex on the runner. This thesis also presents one of the rst detailed studies on transient and no-load conditions in a model hydro-turbine. Pressure and strain sensors were used to identify the dominant ow instabilities in speed-no-load and runaway conditions. Scale Adaptive Simulations (SAS) of the speed-no-load condition were used to study a rotating stall dominating the runner ow. Simulations without runner blades indicate that the rotating stall is associated with an unstable shear-layer originating from a recirculation around the runner hub and a boundary layer separation on the turbine head cover. Those results open the possibility of eventually developing mitigation techniques.
34
Liljeroth, Henrik. "Measuring and Analysing Execution Time in an Automotive Real-Time Application." Thesis, Linköping University, Department of Computer and Information Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-51691.
Full textAbstract:
Autoliv has developed the Night Vision system, which is a safety system for use incars to improve the driver’s situational awareness during night conditions. It is areal-time system that is able to detect pedestrians in the traffic environment andissue warnings when there is a risk of collision. The timing behaviour of programsrunning on real-time systems is vital information when developing and optimisingboth hardware and software. As a part of further developing their Night Visionsystem, Autoliv wanted to examine detailed timing behaviour of a specific part ofthe Night Vision algorithm, namely the Tracking module, which tracks detectedpedestrians. Parallel to this, they also wanted a reliable method to obtain timingdata that would work for other parts of that system as well, or even other applications.
A preliminary study was conducted in order to determine the most suitable methodof obtaining the timing data desired. This resulted in a measurement-based approachusing software profiling, in which the Tracking module was measured usingvarious input data. The measurements were performed on simulated hardwareusing both a cycle accurate simulator and measurement tools from the systemCPU manufacturer, as well as tools implemented specifically to handle input andoutput data.
The measurements resulted in large amounts of data used to compile performancestatistics. Using different scenarios in the input data, we were able to obtain timingcharacteristics for several typical situations the system may encounter duringoperation. By manipulating the input data we were also able to observe generalbehaviour and achieve artificially high execution times, which serves as indicationson how the system responds to irregular and unexpected input data.
The method used for collecting timing information was well suited for this particularproject. It provided the possibility to analyse behavior in a better waythan other, more theoretical, approaches would have. The method is also easilyadaptable to other parts of the Night Vision system, or other systems, with onlyminor adjustments to measurement environment and tools.
35
Dädeby, Oskar. "Dynamic Blast Load Analysis using RFEM : Software evaluation." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-84784.
Full textAbstract:
The purpose of this Master thesis is to evaluate the RFEM software and determine if it could be used for dynamic analyses using blast loads from explosions. Determining the blast resistance for a structure is a growing market and would therefore be beneficial for Sweco Eskilstuna if RFEM could be used for this type of work. The verification involved comparing the RFEM software to a real experiment which consisted of a set of blast tested reinforced concrete beams. By using the structural properties from the experiment project with the experiment setup the same structure could be replicated in RFEM. RFEM would then simulate a dynamic analysis loaded with the same dynamic load measured from the experiment project in two different dynamic load cases caused by two differently loaded explosions. The structural response from the experiment could then be compared to the response simulated by the RFEM software, which consisted of displacement- and acceleration time diagrams. By analysing the displacement and acceleration of both the experiment and the RFEM software the accuracy was determined, and how well RFEM preformed the analysis for this specific situation. The comparison of the displacement and acceleration between the experiment and RFEM was considered acceptable if the maximum displacement was consistent with the experiments result and within the same time frame. The acceleration was considered acceptable if the initial acceleration was consistent with the experiment result. These criteria needed to be met for the verification that RFEM could simulate a dynamic analysis. If the software managed to complete a dynamic analysis for two dynamic load cases, then the software could be evaluated which consisted of determining if the post blast effects could be determined and if the modelling method was reliable. The acceleration from RFEM were in good agreement with the experiment test at the initial part of the blast, reaching a close comparison for both load cases after 3 ms. Then the RFEM acceleration had a chaotic behaviour reaching no similarities for the duration of the blast. The displacement managed to get a close comparison of the maximum displacement with a margin of 0,5 mm for both load cases within a 1 ms time margin. RFEM managed in conclusion to simulate a blast load analysis, the displacement and acceleration gave acceptable results according to the criteria. With the method chosen a fast simulation was achieved and with the same model complying with two different load cases for the same model gave indication that the first result was not a coincidence. The steps taken in the modelling method was straight forward, but two contributing parameters were determined to devalue the reliability. First parameter was the material model chosen for the concrete, which was chosen to a plastic material model. The two optional material model’s linear elastic and non-linear elastic both caused failed simulations. Also, the better model for the material model would have been a diagram model which insured that the concrete lost is capacity in tension with maximum capacity, but this was not available in a dynamic analysis with multiple load increments. Which is the reason why a plastic material model was chosen for the concrete. The second reason was the movement of the beam in the supports. This data was not recorded in the experiment but was determined to be a contributing part of the test. This however gave big differences of the result depending on how much the beam could move. In the end the best possible result was chosen to comply with the first load case where the same RFEM model was used in the second test. The second load case showed just as good results as the first load case, but with the big variation in results depending on the movement of the beam in the supports made this part unclear. For the evaluation the question if the RFEM could provide a post blast analysis needed to be addressed, where the answer is no. The failure mode was chosen to comply with the choice of modelling method which required the analysis of the plastic strain in the reinforcement bars. This information was not available using the add-on module DYNAM-PRO and could therefore not provide the answer if the model structure resisted the blast. For future work of this master thesis is to build a model that would give a more detailed post blast analysis, where this thesis was made to test the software. For this more work would be necessary by the creators Dlubal to further improve the add-on-module, which involves more extractable results and more detailed tools when using a dynamic load case, where some important functionality is only usable in a static load case. Other than that, RFEM managed to complete the dynamic analysis, and with further improving of the modelling method a more detailed analysis can be made and then be usable in real projects in the future.
36
Liu, Kin-shing. "Improved analysis of flow time scheduling." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B36274379.
Full text
37
Liu, Kin-shing, and 廖建誠. "Improved analysis of flow time scheduling." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B36274379.
Full text
38
Nandorf, Joel. "Responsive Web Design – Evaluation of Techniques to Optimize Load Time." Thesis, Umeå universitet, Institutionen för datavetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-81028.
Full textAbstract:
Responsive Web Design has, in short time, become a common method to create websites that automatically adapt the layout to different screen sizes. However, critique has been raised about poor performance due to large page size and high number of requests to the web server. The aim of this study is to evaluate techniques to optimize the load time of a responsive website. This is done by creating a prototype in the form of a responsive website, which is used as a base for the optimization. Tests are performed by measuring the page size and the number of requests when using four different optimization techniques. The results show that combining optimization techniques can dramatically reduce the page size and the number of requests. Consequently, this has a positive impact on the load time of the website. Furthermore, the Mobile First approach is important in responsive web design as it prioritizes the use of mobile devices and as a result highlights the significance of web performance. It is also suggested to set a Performance Budget early in web development projects in order to avoid slow websites and spread awareness about the importance of performance.
39
Khan, Asif H. "Analysis of time varying load for minimum loss distribution reconfiguration." Diss., This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-06062008-171313/.
Full text
40
Kockar, Ivana. "Iterative generation of synthetic power system networks for load flow studies." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0031/MQ50633.pdf.
Full text
41
Clothiaux, John D. "Verification of rain-flow reconstructions of a variable amplitude load history." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-11072008-063531/.
Full text
42
Rodriguez, Cuauhtemoc. "An investigation into the multiple equilibria of the load flow problem /." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79256.
Full textAbstract:
The load flow problem consists of finding the bus complex voltages that balance the power injections and power flows in a transmission network. Two linear formulations using continuous and integer variables are developed in order to find all the multiple equilibria of the load flow problem.The thesis begins with an analysis of the load flow equations together with the notions of feasibility regions and multiple equilibria.
Two new load flow formulations in polar coordinates are presented as mixed-integer linear problems. In the first one, the nonlinear nature of the equations is represented by segmenting the sinusoidal terms into a large number of linear components each of which is assigned a binary variable. In the second formulation, the sinusoidal terms are approximated with a large number of tangent planes, with each transmission line being assigned a single binary variable to denote whether the angle difference is positive or negative. A combinatorial approach is used to identify all the load flow solutions.
Both formulations are tested on two systems: a 3-bus, 3-line and a 6-bus, 7-line. The former has been widely studied and its multiple equilibria are known. The latter represents a larger system with up to 64 load flow solutions, whose exact number is parameter-dependent and generally unknown.
43
Sosebee, Philip D. "Flow visualization and detailed load measurements over a maneuvering UCAV 1303." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5743.
Full textAbstract:
Approved for public release, distribution unlimitedThe unsteady aerodynamic performance of a maneuvering 1/72nd scale model of an unmanned combat air vehicle (UCAV) 1303 geometry has been studied in the Naval Postgraduate School water tunnel. Despite the numerous past publications on UCAV flows, none pertains to the UCAV maneuvering characteristics. Due to its nonslender wing, the flow features over the chosen aircraft are unique in that both features of highly yawed wings and of delta wings are present. Even though the speeds and Reynolds numbers are low in a water tunnel, the results of the present studies attest to the suitability of a water tunnel for performing such studies. Force measurements taken at various Reynolds numbers, model attitudes and maneuvering rates for comparison proved to be valid for data comparison to potential flight scenarios. The UCAV 1303 model has a 47 degrees leading edge sweep and a cranked trailing edge delta wing with a fuselage. Pitching and rolling maneuvers were performed in various combinations to demonstrate the real flight conditions of a maneuvering UCAV. A five-component strain-gage and flow monitoring software were used to determine force and moment coefficients in real time. These coefficients were analyzed and compared to previous flow visualization tests to correlate the various flow features recorded during that phase of the study, and to determine the overall stability of a delta wing UCAV. These plots demonstrate what is seen visually at Reynolds numbers from 1.17x104 to 2.94x104. Where the pitch break occurs on the wings during maneuvers is correlated and dependent on Reynolds number, as initially suspected. Performing unsteady maneuvers helped in retaining the approximate linear variation of lift coefficient to higher angles of attack. Roll maneuvers produced oscillatory side forces and moments at high angles of attack and roll, indicating potentially serious unsteady forces.
44
RIBEIRO, SOLANGE MARIA PINTO. "APPLICATION OF PROBABILISTIC LOAD FLOW THE EXPANSION PLANNING OF POWER SYSTEMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1990. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9468@1.
Full textAbstract:
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEsta dissertação apresenta uma aplicação das técnicas de Fluxo de Potência Probabilístico (FPP) no planejamento da expansão de sistemas de potência. Um breve resumo da formulação e solução do problema de FPP é incluído para identificar as diferenças entre esta técnica e outras ferramentas disponíveis tais como os algoritmos de avaliação da confiabilidade composta - geração e transmissão. O potencial das técnicas de FPP será demonstrado através de um estudo utilizando o Sistema Norte/Nordeste brasileiro. O planejamento da expansão da rede elétrica de uma área deste sistema, obtido através de um algoritmo convencional de fluxo de potência, é comparado com aquele obtido por um programa de FPP que modela as indisponibilidades de capacidade de geração, bem como as incertezas existentes nos picos de cargas. As diferenças significativas demonstram os benefícios das técnicas de FPP. Uma ênfase especial é dada à modelagem de curto e longo prazos das incertezas das cargas.
This dissertation presents an application of Probabilistic Load Flow (PFL) techniques to the expansion planning of power systems. A brief review of the PFL formulation and solution is included to identify differences between this technique and other available tools such as composite generation and transmission reliability evaluation algorithms. The potencial of the PLF technique is demonstrated by a case study using the Brazilian North/Northeastern system. The network expansion planning of an area of this system is studied using a conventional load flow program and the results compared with those obtained from a PLF program that models generation capacity unavailabilities and peak load uncertainties. The significant diffrences demonstrate the benefits of the PLF technique. Special emphasis is given to short and long term modeling using analyses of real system load data.
45
Das, Syamantak. "Scheduling with outliers to minimize load and flow- time." Thesis, 2016. http://localhost:8080/iit/handle/2074/7147.
Full text
46
Agarwal, Tarun. "Noncooperative Games for Autonomous Consumer Load Balancing Over Smart Grid." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8450.
Full textAbstract:
Traditionally, most consumers of electricity pay for their consumption according to a fixed-rate. The few existing implementations of real time pricing have been restricted to large industrial consumers, where the benefits could justify the high implementation cost. With the advancement of Smart Grid technologies, large scale implementation of variable-rate metering will be more practical. Consumers will be able to control their electricity consumption in an automated fashion, where one possible scheme is to have each individual maximize their own utility as a noncooperative game. In this thesis, noncooperative games are formulated among the consumers of Smart Grid with two real-time pricing schemes, where the Nash equilibrium operation points are investigated for their uniqueness and load balancing properties. The first pricing scheme charges a price according to the average cost of electricity borne by the retailer and the second charges according to a time-variant increasing-block price. The zero revenue model and the constant revenue rate model, are the two revenue models being considered. The relationship between these games and certain congestion games, known as atomic flow games from the computer networking community, is demonstrated. It is shown that the proposed noncooperative game formulation falls under the class of atomic splittable flow games. It is shown that the Nash equilibrium exists for four different cases, with different pricing schemes and revenue models, and is shown to be unique for three of the cases, under certain conditions. It is shown that both pricing schemes lead to similar electricity loading patterns when consumers are interested only in the minimization of electricity costs. Finally, the conditions under which the increasing-block pricing scheme is preferred over the average cost based pricing scheme are discussed.
47
Kim, Hongseok. "Exploring tradeoffs in wireless networks under flow-level traffic: energy, capacity and QoS." 2009. http://hdl.handle.net/2152/7853.
Full textAbstract:
Wireless resources are scarce, shared and time-varying making resource allocation mechanisms, e.g., scheduling, a key and challenging element of wireless system design. In designing good schedulers, we consider three types of performance metrics: system capacity, quality of service (QoS) seen by users, and the energy expenditures (battery lifetimes) incurred by mobile terminals. In this dissertation we investigate the impact of scheduling policies on these performance metrics, their interactions, and/or tradeoffs, and we specifically focus on flow-level performance under stochastic traffic loads. In the first part of the dissertation we evaluate interactions among flow-level performance metrics when integrating QoS and best effort flows in a wireless system using opportunistic scheduling. We introduce a simple flow-level model capturing the salient features of bandwidth sharing for an opportunistic scheduler which ensures a mean throughput to each QoS stream on every time slot. We show that the integration of QoS and best effort flows results in a loss of opportunism, which in turn results in a reduction of the stability region, degradation in system capacity, and increased file transfer delay. In the second part of the dissertation we study several ways in which mobile terminals can backoff on their uplink transmit power (thus slow down their transmissions) in order to extend battery lifetimes. This is particularly effective when a wireless system is underloaded, so the degradation in the users' perceived performance can be negligible. The challenge, however, is developing a mechanism that achieves a good tradeoff among
transmit power, idling/circuit power, and the performance customers will see. We consider systems with flow-level dynamics supporting either real-time or best effort (e.g., file transfers) sessions. We show that significant energy savings can be achieved by leveraging dynamic spare capacity. We then extend our study to the case where mobile terminals have multiple transmit antennas. In the third part of the dissertation we develop a framework for user association in infrastructure-based wireless networks, specifically focused on adaptively balancing flow loads given spatially inhomogeneous traffic distributions. Our work encompasses several possible user association objective functions resulting in rate-optimal, throughput-optimal, delay-optimal, and load-equalizing policy, which we collectively denote [alpha]-optimal user association. We prove that the optimal load vector that minimizes this function is the fixed point of a certain mapping. Based on this mapping we propose an iterative distributed user association policy and prove that it converges to the globally optimal decision in steady state. In addition we address admission control policies for the case where the system cannot be stabilized.text
48
Srivastava, Suresh Chandra. "On some aspects of load flow and optimal load flow of interconnected power systems." Thesis, 1987. http://localhost:8080/xmlui/handle/12345678/5412.
Full text
49
CHEN, JIAN-FU, and 陳建富. "Numerical analysis of load flow problems." Thesis, 1985. http://ndltd.ncl.edu.tw/handle/88424953143501698348.
Full text
50
Hou, Ching-Wen, and 侯清文. "A Network-Based Distribution Load Flow." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/84632809574115470822.
Full textAbstract:
碩士義守大學
電機工程學系
89
Since the features of distribution systems are different from transmission systems, the solution techniques for load flow problem need to be modified. Comparing with transmission systems, distribution networks are commonly: (a) three-phase unbalanced oriented; (b) radial with sometimes weakly-meshed topology; (c) with high resistance to reactance (r/x) ratio; (d) unbalanced distributed load; (e) extremely large number of branches/nodes. Those features make the traditional load flow method, such as Newton-Raphson method and Gauss-Seidel method, fail to meet the requirements of efficiency and accuracy for distribution systems. Several load flow algorithms specially designed to handle the features of distribution systems have been proposed in the literature. In the thesis, a novel and fast three-phase load flow algorithm for unbalanced radial distribution systems is proposed. The proposed method uses branch voltages as state variables and employs the Newton-Raphson algorithm to solve the load flow problem. By utilizing branch voltages as state variables, a constant Jacobian matrix can be obtained and a building algorithm for Jacobian matrix is then developed based on the observation of the constant Jacobian matrix. A solution technique, which takes the network structure and computer economy into account, is also developed. For any equipment, if its equivalent current injection or admittance matrix can be obtained, it can be easily integrated into the proposed method. Test results show the proposed method is efficient and has great potential for real-time applications.