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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Aplicação do dispositivo FACTS (Flexible AC Transmission Systems) em sistema de distribuição -simulação de desempenho. / Distribution system FACTS (flexible AC transmission systems) application - performance simulation.

Masuda, Mario 13 September 2006 (has links)
As novas tecnologias FACTS aplicadas ao sistema de transmissão, com base em eletrônica de potência, podem também ser úteis à distribuição. Para tal é preciso conduzir um procedimento de consolidação da utilização e do desempenho destas, para sua aplicação sem riscos. Neste trabalho, dois aspectos serão contemplados. O primeiro se refere à aplicação do dispositivo FACTS atuando como um capacitor série. Em se tendo controle de módulo e da fase da tensão inserida em série com a linha pode-se fazê-la comportar-se como uma queda em uma reatância série capacitiva ou indutiva. O controle dessa reatância série (aumentando/diminuindo) permitirá a aplicação do conceito de compensação série em qualquer ponto do sistema de distribuição, provendo benefícios de um controle contínuo da tensão e também do controle do fluxo de carga no sistema independente da corrente. O segundo aspecto refere-se ao uso dos dispositivos na conexão de alimentadores controlando a potência ativa entre eles. Para esta operação outro dispositivo UPFC, com conceito similar ao descrito acima, entretanto atuando na fase da tensão entre 2 barras, comporta-se como um transformador defasador com variação contínua de ?taps?, podendo controlar a potência ativa entre os alimentadores. A aplicação destas tecnologias propiciarão vários benefícios para a expansão da distribuição tais como, flexibilização do uso da rede, interligação de alimentadores permitindo manobras de blocos de energia sem ?pisca?, ajuste contínuo do suporte de reativos durante a operação, controle dinâmico do fluxo de potência. O objetivo deste trabalho é estudar a aplicabilidade da tecnologia FACTS e estender este conceito para aplicação em sistemas de distribuição e conduzir simulações digitais em redes de distribuição (15kV) identificando o desempenho e os benefícios atingidos. O programa de simulação utilizado é o ATP (Alternative Transients Program). / The new FACTS technologies applied to the transmission system, based on power electronics, can also be useful to the distribution. For that, it is necessary to drive a procedure to consolidate the use and the performance for their application without risks. In this work two aspects will be approached. The first refers to the application of a FACTS device acting as series compensator. This device will be able to control the voltage in module and phase in order to act as a voltage drop in a serie reactance with capacitive or inductive features. The control of this series reactance (increasing/ decreasing) will allow the application of series compensation concept to any point of the distribution system, providing the benefits of continuous control of the voltage added to the load flow control in the system independent of the current. The second aspect refers to its use in the connection of two feeders controlling the active power between them. For this operation other device, UPFC, with similar concept as described previously, acts mainly in the phase of the injected voltage in the line, performing as a phase-shift with continuous taps variation and is able to control the active power flow between feeders. The application of this technology will provide several benefits for the distribution expansion, such as, a greater flexibility in the use of the network, connection of feeders without load flow interruption, continuous adjust of reactive power during the operation and dynamic control of power flow. The purpose of this work is to study the applicability of the FACTS technology, to extend this concept for the application in the distribution system by using digital simulations in distribution network up to 15kV identifying the performance and the reached benefits.
52

Power control in CDMA systems.

January 2000 (has links)
by Kin Kwong Leung. / Thesis submitted in: November 1999. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 67-[70]). / Abstracts in English and Chinese. / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Code Division Multiple Access (CDMA) --- p.1 / Chapter 1.1.1 --- The Cellular Concept --- p.2 / Chapter 1.2 --- Fading and Power Control --- p.3 / Chapter 1.2.1 --- Large Scale Fading --- p.3 / Chapter 1.2.2 --- Small Scale Fading --- p.4 / Chapter 1.2.3 --- Power Control --- p.5 / Chapter 1.2.4 --- Standard Interference Function --- p.5 / Chapter 1.3 --- Previous Work --- p.6 / Chapter 1.3.1 --- Power Control --- p.6 / Chapter 1.3.2 --- Convergence Analysis --- p.8 / Chapter 1.4 --- Scope of this Thesis --- p.8 / Chapter 1.5 --- Organization of the Thesis --- p.9 / Chapter 2 --- System Model --- p.10 / Chapter 2.1 --- System and Definitions --- p.10 / Chapter 2.2 --- Varying Link Gains Model --- p.11 / Chapter 2.3 --- SIR model in CDMA System --- p.13 / Chapter 2.4 --- Simulation Model --- p.14 / Chapter 3 --- Fade Margin --- p.17 / Chapter 3.1 --- Introduction --- p.17 / Chapter 3.2 --- Fixed-step Power Control Algorithm --- p.18 / Chapter 3.3 --- Definitions and Feasibility of SIR --- p.19 / Chapter 3.3.1 --- Definition --- p.19 / Chapter 3.3.2 --- Feasibility --- p.20 / Chapter 3.4 --- Performance Analysis on Fading Channel --- p.22 / Chapter 3.4.1 --- Single-User --- p.22 / Chapter 3.4.2 --- Multiple-User --- p.24 / Chapter 4 --- Generalized Step Power Control Algorithm --- p.28 / Chapter 4.1 --- Introduction --- p.28 / Chapter 4.2 --- Generalized Fixed Step Power Control Algorithm --- p.29 / Chapter 4.3 --- Existence of the Solution --- p.30 / Chapter 4.4 --- Parameter Optimization --- p.31 / Chapter 4.4.1 --- Single-User --- p.34 / Chapter 4.4.2 --- Multiple-User --- p.37 / Chapter 4.5 --- Performance Analysis --- p.41 / Chapter 4.5.1 --- Single-User --- p.41 / Chapter 4.5.2 --- Multiple-User --- p.42 / Chapter 4.6 --- Hybrid Scheme --- p.47 / Chapter 5 --- Convergence Analysis --- p.49 / Chapter 5.1 --- Introduction --- p.49 / Chapter 5.2 --- Totally Asynchronous Models --- p.50 / Chapter 5.3 --- Normalized Interference Function --- p.52 / Chapter 5.4 --- Existence of Quantized Solution --- p.53 / Chapter 5.5 --- Convergence Theorem --- p.55 / Chapter 6 --- Conclusion and Future Work --- p.64 / Chapter 6.1 --- Conclusion --- p.64 / Chapter 6.2 --- Future Works --- p.65 / Bibliography --- p.67
53

Differences in Frequency and Severity of Violence For Intimate Terrorism Across Genders: A Test of Johnson's Theory

Wagers, Shelly 14 November 2005 (has links)
This study sought to further build on previous empirical findings regarding Johnsons theory that the gender symmetry debate can at least be partially resolved by acknowledging that two distinct subgroups of physical violence exist within intimate partner violence: Intimate Terrorism (IT) and Situational Couple Violence (SCV). According to Johnsons predictions these separate groups can be distinguished by the use of non-violent control tactics. This study focused on testing the ability of non-violent control tactics to predict the frequency and severity of violence within the sub-group intimate terrorism. It further explored Johnsons assertion that intimate terrorism is gender asymmetric with females experiencing a greater amount of victimization. Previous studies demonstrated moderate support that two subgroups do exist within intimate partner violence and that intimate terrorism may be asymmetrical. However, only one of the previous studies included a male sample that was not reflective of the general population. This study will test the gender asymmetry of intimate terrorism by using both a male and female sub-sample form the National Violence Against Women Survey. This studies sample consisted of males and females reporting at least on incident of physical violence by either their current spouse or cohabitating heterosexual partner. The statistical analysis showed moderate support that there are two subgroups within intimate partner violence that can be distinguished by the use of non-violent control tactics. It also demonstrated that for the subgroup intimate terrorism there are some differences across gender when examining severity and frequency of violence. However, only a small amount of the variance in intimate terrorism can be explained by non-violent control tactics.
54

Nonlinear neural control with power systems applications

Chen, Dingguo 30 September 1998 (has links)
Extensive studies have been undertaken on the transient stability of large interconnected power systems with flexible ac transmission systems (FACTS) devices installed. Varieties of control methodologies have been proposed to stabilize the postfault system which would otherwise eventually lose stability without a proper control. Generally speaking, regular transient stability is well understood, but the mechanism of load-driven voltage instability or voltage collapse has not been well understood. The interaction of generator dynamics and load dynamics makes synthesis of stabilizing controllers even more challenging. There is currently increasing interest in the research of neural networks as identifiers and controllers for dealing with dynamic time-varying nonlinear systems. This study focuses on the development of novel artificial neural network architectures for identification and control with application to dynamic electric power systems so that the stability of the interconnected power systems, following large disturbances, and/or with the inclusion of uncertain loads, can be largely enhanced, and stable operations are guaranteed. The latitudinal neural network architecture is proposed for the purpose of system identification. It may be used for identification of nonlinear static/dynamic loads, which can be further used for static/dynamic voltage stability analysis. The properties associated with this architecture are investigated. A neural network methodology is proposed for dealing with load modeling and voltage stability analysis. Based on the neural network models of loads, voltage stability analysis evolves, and modal analysis is performed. Simulation results are also provided. The transient stability problem is studied with consideration of load effects. The hierarchical neural control scheme is developed. Trajectory-following policy is used so that the hierarchical neural controller performs as almost well for non-nominal cases as they do for the nominal cases. The adaptive hierarchical neural control scheme is also proposed to deal with the time-varying nature of loads. Further, adaptive neural control, which is based on the on-line updating of the weights and biases of the neural networks, is studied. Simulations provided on the faulted power systems with unknown loads suggest that the proposed adaptive hierarchical neural control schemes should be useful for practical power applications. / Graduation date: 1999
55

Planning for controllable network devices in power transmission systems

Kosterev, Dmitry N. 28 February 1996 (has links)
The full capacity of the existing transmission lines is often underutilized due to the system stability requirements. Controllable network devices represent the effective means of improving the system stability, and their deployment allows better use of the existing transmission facilities and can help to avoid construction of new lines. This dissertation addresses system analysis and modeling of controllable network devices. Transient angle stability is one of the major requirements limiting transfer capability of the power transmission systems. The theoretical concepts of transient angle controllability using controllable network devices are considered in this dissertation. The main results are derived for a general transmission network structure and applied to series and shunt compensators as well as braking resistors. The proposed approach allows to quantify controllability and to relate it to the control device size, type and location in the transmission network. Transient stability controllers are needed to maximize the device effect on the transient angle stability enhancement. The transient stability controller functional structure is discussed and the design requirements for each component are specified. The examples of controller designs are presented. Emerging technologies such as Thyristor-Controlled Series Compensators and Synchronous Voltage Sources offer superior control capabilities and performance characteristics as compared to conventional compensators. Unlike conventional compensators, the new controllable network devices are very complex dynamical systems and require more comprehensive modeling for time-domain studies and controller designs. Detailed models of a Thyristor-Controlled Series Compensator and a Synchronous Voltage Source for powerflow, transient stability, and electro-magnetic transient studies are presented. Finally, a detailed planning study for increasing transfer capability of the Montana transmission system using controlled series compensation is presented. A variety of design and performance requirements is considered in this study, which makes it a useful reference for similar planning projects. / Graduation date: 1996
56

Robustness and stability of power-system models using damping and synchronizing torques

January 1981 (has links)
Sherman M. Chan, Michael Athans. / Bibliography: leaf 9. / Caption title. "August 15, 1981." / Supported by the U.S. Department of Energy, Division of Electric Energy Systems, under Contract DE-AC01-78RA03395
57

Independent Counsel and Independent Prosecutor System

Wu, Shih-Chi 23 August 2006 (has links)
In March 19, 2004, That day was before the presidential election day, when The presidential campaign was in full swing, the President Chen and the Vice President was shot by a shooter. This criminal act shocked the whole world, and even the opposition parties argued this event had already changed the result of the presidential Election. After the presidential election, the KMT legislators and the PFP legislators are in the majority in The Legislative Yuan, and they passed ¡ythe Act of the Special Commission on the Investigation of the Truth in Respect of the 319 Shooting¡z(hereinafter the ¡§SCITA¡¨) without considering controversial issues. According to the law, the Special Commission on the Investigation of the Truth in Respect of the 319 Shooting (hereinafter the ¡§SCIT¡¨) was set up. December 15, 2004, J.Y. Interpretation NO.585 recognized the ¡¨SCIT¡¨ was the organization responsible for the exercise of investigation, and admitted the ¡¨SCIT¡¨ to be no violation of the Constitution. But the ¡§SCIAT¡¨ provided the power to ¡§SCIT¡¨ for ordering prosecutors and retrial, etc. There was in violation of the Constitution. The Legal Profession¡Bjurists and political scientists had different opinions with the character of ¡§SCIT¡¨¡Aand it also meant that the legislators of KMT and PFP challenged the independence of Taiwan¡¦s prosecutor system. Accordingly, they hoped the character of ¡§SCIT¡¨ can be similar with the¡¨ WARREN COMMISSION¡¨ in America. They even hoped to legislate for establishing the Independent Counsel System. Because they believe the prosecutor system in Taiwan cannot avoid intervention from politics or administrative organizations, so when a prosecutor investigates crimes, he might ignored some kinds of crime involving with high-position administrators. April 12,2004, a part of prosecutors from Shihlin District Prosecutors Office¡BTaoyuan District Prosecutors Office, and etc. They cosigned a public statement. It meant that ¡§Begin the independent prosecutor system, solve the crisis of the 319 truth and the innovation of prosecutor system to win-win situation¡¨. Their suggestion is establishing the independent prosecutor system to investigate some crimes involving with high-position administrators. Those prosecutors asserted that establishing the independent prosecutor System would be better than leading in the Independent Counsel System. And making the prosecutor a categoric judicatory position¡Battorney general substitutes the minister of Ministry of Justice to be the chief of the prosecutor system¡Ball prosecutor personnel matters decided by the prosecutor personnel committee, and etc. These methods will improve the independence of the prosecutor system, and avoid intervention from any illegitimate reasons. For the character of the Independent Counsel in America, it belongs to administration. United States Congress pass a law (Ethics in Government Act of 1978) to assure the Independent Counsel can exercise his power without interference. So the Independent Counsel in America is different from the prosecutor in Taiwan. Some constitutionalists claim that the Independent Counsel was in violation of constitution, and this contention was a key point of many reasons to make the law become void. According to these reasons, what is the difference between the Independent Counsel and the independent prosecutor system? Whether we must lead in the Independent Counsel System to solve the defect of the prosecutor system in Taiwan or not? Whether the power of control (one of the five powers of the government specified in the Constitution of the Republic of China) is analogous to the Independent Counsel System? Above-mentioned questions would be the topics of debate.
58

A Study of the Administrative Supervision System in Taiwan

Chen, Rung-jou 08 July 2008 (has links)
Uncorrupted political system is the basic criterion for the government policy. It affects the development of the whole country from political, economical and social perspectives. If the policy systems and the governors are corrupted, the credibility of the government will be decreased. Therefore, the whole country¡¦s administration and regulation will be in serious danger. Today, fighting for corruption is in the reforming stage, and every party in Taiwan all supports this policy. However, due to different political concerns, during the process of implementing the Sunshine Act, the original idea of fighting corruption has been contorted. Under this circumstance and in order to satisfy people¡¦s expectation, it is necessary to seriously concentrate on the problems of establishing an uncorrupted political system. In the nations with honest government systems, administrative supervision system is a very important segment. The system places administrative power under supervision and inspection controls. Within their independent and detached status and fair operation, administrative supervisory organs can have influential and powerful controls over the administrative departments and staff. Under this mechanism, a completely anti-corruption system and a reputation of honor government can be successfully established. This research made an in-depth study of the Control Yuan and the government employee ethics units as the major study subjects and combined with the supplementary administrative law materials to further examine the administrative supervision system in Taiwan. This research was mainly prepared with the use of literature analysis, comparative analysis and inductive analysis and has employed the basic theories of Administration Act, i.e. the five major structures of administrative principles, administrative organization, limit of administrative rights, administrative relief and administrative surveillance, as the research approaches of the study to examine the law of the administrative supervision system thoroughly. It is hoped that through the analysis of the Control Yuan and the government employee ethics units from the jural, institutional, and functional perspectives, this study would be able to provide the government an effective and practicable administrative supervision system.
59

Dynamic control of grid power flow using controllable network transformers

Das, Debrup 19 December 2011 (has links)
The objective of the research is to develop a cost-effective, dynamic grid controller called the controllable network transformer (CNT) that can be implemented by augmenting existing load tap changing (LTC) transformers with an AC-AC converter. The concept is based on using a fractionally rated direct AC-AC converter to control the power through an existing passive LTC. By using a modulation strategy based on virtual quadrature sources (VQS), it is possible to control both the magnitude and the phase angle of the output voltage of the CNT without having any inter-phase connections. The CNT architecture has many advantages over existing power flow controllers, like absence of low frequency storage, fractional converter rating, retro-fitting existing assets and independent per-phase operation making it potentially attractive for utility applications. The independent control of the magnitude and the phase angle of the output voltage allow independent real and reactive power flow control through the CNT-controlled line. In a meshed network with asymmetric network stresses this functionality can be used to redirect power from critically loaded assets to other relatively under-utilized parallel paths. The power flow controllability of CNT can thus be used to lower the overall cost of generation of power. The solid state switches in the CNT with fast response capability enable incorporation of various additional critical functionalities like grid fault ride through, bypassing internal faults and dynamic damping. This bouquet of features makes the CNT useful under both steady state and transient conditions without compromising the grid reliability.
60

Microprocessor-based field-oriented control of a synchronous motor drive using a three-phase solid-state sinusoidal current source

韋盧溝, Wai, Lo-kau. January 1988 (has links)
published_or_final_version / Electrical Engineering / Master / Master of Philosophy

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