Resumo: O desenvolvimento da agricultura e o uso da terra de maneira não somente a protegê-la contra alterações superficiais provocadas pela ação constante dos fenômenos naturais, mas também a desenvolver aos poucos sua capacidade produtiva, requer um cuidadoso planejamento inicial. Para que o mesmo seja efetivo e eficiente, é necessário que se tenha acesso a informações corretas e detalhadas, as quais podem estar disponíveis em imagens aéreas de sensoriamento remoto. O uso das fotografias aéreas verticais dentre os produtos do Sensoriamento Remoto se tornou cada vez mais frequente nos projetos de levantamentos, planejamentos e explorações do solo, principalmente porque substitui, com vantagens, outras bases cartográficas, além da riqueza de detalhes que oferece, eliminando-se assim as dificuldades de acesso em áreas inacessíveis, bem como facilitando a visão tridimensional, por aumentar o rendimento e a precisão do mapeamento, por meio da combinação dos trabalhos de campo e laboratório, com o estudo de interpretação fotográfica. Este trabalho utilizou-se de fotografias aéreas pancromáticas nas escalas nominais 1:25000 (1962), 1:45000 (1977) e coloridas na escala nominal aproximada de 1:30.000, proveniente do levantamento aerofotogramétrico efetuado no ano de 2005, tendo como objetivo mostrar através da utilização de um Sistema de Informação Geográfica (SIG) a possibilidade de realizar uma análise mais completa e segura de valores de área, obtidos diretamente na foto sem correções de escala, e posteriormente compará-los com os valores de área obtidos de fotografias aéreas com escalas corrigidas, tendo como referência a carta do Instituto Geográfico e Cartográfico do Estado de São Paulo, resultando num coeficiente de erro que mostrará as diferenças das áreas através... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract : interpretation is a basic resource and it constitutes in a technique which enables infinite refining. Agricultural development and ground use requires a careful initial planning in order not only to protect them against superficial changing provoked by natural phenomena but also to gradually develop its productive capacity. For the efficiency of ground management, it is necessary to access correct and detailed information which can be available through aerial images of remote sensing. The use of vertical aerial photography through Remote Sensing has become more common in ground collection, management and exploration, mainly because it substitutes, with lots f advantage, for cartographic bases, besides offering detailed characteristics, eliminating access difficulties in inaccessible areas, as well as facilitating a tridimensional view once it increases map efficiency and accuracy by combining field and laboratory work with photography interpretation. This work, using panchromatic aerial photography in nominal scale 1:25000 (1962), 1:45000 (1977) , and approximate nominal scale of 1:30.000, proceeding from aerial photogrameter developed in 2005, aimed at showing through the Geographic Information System (GIS) the possibility of developing a more complete and accurate analysis of the area values, obtained directly from photos without scale correction, and after comparing it with area values obtained from aerial photography with correct scale referred in IGC (Brazilian Cartography and Geography Institute) guidelines, resulting in an error coefficient which shows area differences through two proposed study. Considering the aerial photographies in three different years: 192, 1977 and 2005, it is possible to affirm that the 2005's images presented lower values of area difference... (Complete abstract click electronic access below) / Orientador: Zacarias Xavier de Barros / Coorientador: Sergio Campos / Banca: Muricy Domingues / Banca: Otavio Yassuo Itame / Banca: Lincoln Gering Cardoso / Banca: Osmar Delmanto Junior / Doutor

This thesis investigates the effects of High Voltage Direct Current (HVDC) lines andmulti-terminal grids on power system small-disturbance stability in the presence ofoperational uncertainties. The main outcome of this research is the comprehensiveprobabilistic assessment of the stability improvements that can be achieved through theuse of supplementary damping control applied to HVDC systems.Power systems are increasingly operated closer to stability boundaries in order toimprove their efficiency and economic value whilst a growing number of conventionalcontrolled power plants are being replaced by stochastic renewable generation sources.The resulting uncertainty in conditions can increase the risk of operational stabilityconcerns and should be thoroughly evaluated. There is also a growing necessity toexplore the potential improvements and challenges created by the introduction of newequipment, such as HVDC systems. In recent years, HVDC systems have become moreeconomically competitive and increasingly flexible, resulting in a proliferation ofprojects. Although primarily installed for power transmission purposes, their flexibilityand controllability can provide further benefits, such as the damping of persistentoscillations in the interconnected networks.This work contributes to a number of areas of power systems research, specificallysurrounding the effects of HVDC systems on the small-disturbance stability oftransmission networks. The application and comprehensive assessment of a Wide AreaMeasurement System (WAMS) based damping controller with various HVDC systemsis completed. The studies performed on a variety of HVDC technology types andconfigurations – as well as differing AC test networks – demonstrate the potential forHVDC-based Power Oscillation Damping (POD). These studies include examinationsof previously unexplored topics such as the effects of available modulation capacity andthe use of voltage source converter multi-terminal HVDC grids for POD. Followingthese investigations, a methodology to probabilistically test the robustness of HVDC based damping controllers is developed. This methodology makes use of classificationtechniques to identify possible mitigation options for power system operators whenperformance is sub-optimal. To reduce the high computational burden associated withthis methodology, the Probabilistic Collocation Method (PCM) is developed in order toefficiently identify the statistical distributions of critical system modes in the presenceof uncertainties. Methods of uncertain parameter reduction based on eigenvaluesensitivity are developed and demonstrated to ensure accurate results when the PCM isused with large test systems. Finally, the concepts and techniques introduced within thethesis are combined to probabilistically design a WAMS-based POD controller morerobust to operational uncertainties. The use of the PCM during the probabilistic designresults in rapid and robust synthesis of HVDC-based POD controllers.

With the increasing demand for electrical power and the growing need for the restructuring of the power industry, electric power systems have become highly complex with inherent complicated dynamics. Therefore, the study of power system stability has continued to receive significant attention from both academic researchers and industrial practitioners. This thesis focuses on supervisory wide-area control for rotor angle stability of multi-machine power systems using Linear Quadratic Gaussian/Loop Transfer Recovery (LQG/LTR) control theory with guaranteed robustness. The supervisory controllers are developed in both continuous-time and discrete-time framework and their performances and robustness are assessed using both frequency-domain tools, and time-domain simulation results. The impact of the communication time-delays that commonly exist in wide-area power system control on the performance and robustness of the closed-loop system is investigated. In particular, different methods of incorporating such time-delays into the design of the supervisory LQG controller are considered. This thesis proposes a modified supervisory LQG controller that utilizes the Extended Kalman Filter to estimate the unknown/varying time-delays. Simulation results obtained using numerical examples involving non-linear power system models demonstrate the benefits of the proposed scheme for both time-invariant and time-varying delays. The resulting supervisory control scheme is well suited for maintaining power system stability in the presence of communication time-delays.

The increasing demand for electricity over the last few decades has not been followed by adequate growth in electric infrastructure. As a result, the reliability and safety of the electric grids are facing tremendously growing pressure. Large blackouts in the recent past indicate that sustaining system reliability and integrity turns out to be more and more difficult due to reduced transmission capacity margins and increased stress on the system. Due to the heavy loading conditions that occur when the system is under stress, the protection systems are susceptible to mis-operation. It is under such severe situations that the network cannot afford to lose its critical elements like the main generation units and transmission corridors. In addition to the slow but steady variations in the network structure over a long term, the grid also experiences drastic changes during the occurrence of a disturbance. One of the main reasons why protection relays mis-operate is due to the inability of the relays to adjust to the evolving network scenario. Such failures greatly compound the severity of the disturbance, while diminishing network integrity leading to catastrophic system-wide outages. With the advancement of Wide Area Measurement Systems (WAMS), it is now possible to redesign network protection schemes to make them more adaptive and thus improve the security of the system. Often flagged for exacerbating the events leading to a blackout, the back-up distance protection relay scheme for transmission line protection and the loss-of-field relay scheme for generator unit protection can be greatly improved from an adaptability-oriented redesign. Protection schemes in general would benefit from a power re-distribution technique that helps predict generator outputs immediately after the occurrence of a contingency. / Ph. D.

Synchronized phasor measurements during dynamics tend to be affected by prevailing system frequency. Some major blackouts in power systems are indeed featured with very large frequency disturbance. Quantitative study done in this dissertation shows that small frequency disturbance may lead to measurement errors, and large frequency disturbance may lead to wrong measurements as well as catastrophic results if applied in system protection and control. The purpose of this dissertation is to bring up this issue, point to some possible solutions and application examples. A synchronized frequency measurement method, which has better dynamic performance, is proposed in this dissertation. Based on this accurate synchronized frequency, a phasor compensation algorithm is proposed to correct the errors due to frequency disturbance in legacy PMUs or as alternative frequency tracking algorithm in new PMUs. Phasor positioning and unbalance issues are also investigated in this dissertation. With these improved synchronized measurements, wide area protection and control can be achieved with higher reliability. As an application example, traditional preset out-of-step protection could be replaced by the adaptive out-of-step protection using wide area measurements. Real-time swing curve and real-time EEAC based adaptive out-of-step protection schemes are developed respectively in this dissertation. Numerical Simulations are performed for validation of the proposed concepts. / Ph. D.

A global view of power system's frequency opens up a new window to the "world" of large system's dynamics. With the aid of global positioning system (GPS), measurements from different locations can be time-synchronized; therefore, a system-wide observation and analysis would be possible. As part of the U.S. nation-wide power frequency monitoring network project (FNET), the first part of the study focuses on utilizing system simulation as a tool to assess the frequency measurement accuracy needed to observe frequency oscillations from events such as remote generation drops in three U.S. power systems. Electromechanical wave propagation phenomena during system disturbances, such as generation trip, load rejection and line opening, have been observed and discussed. Further uniform system models are developed to investigate the detailed behaviors of wave propagation. Visualization tool is developed to help to view frequency behavior simulations. Frequency replay from simulation data provides some insights of how these frequency electromechanical waves propagate when major events occur. The speeds of electromechanical wave propagation in different areas of the U.S. systems, as well as the uniform models were estimated and their characteristics were discussed. Theoretical derivation between the generator's mechanical powers and bus frequencies is provided and the delayed frequency response is illustrated. Field-measured frequency data from FNET are also examined. Outlier removal and wavelet-based denoising signal processing techniques are applied to filter out spikes and noises from measured frequency data. System's frequency statistics of three major U.S. power grids are investigated. Comparison between the data from phasor measurement unit (PMU) at a high voltage substation and from FNET taken from 110 V outlets at distribution level illustrates the close tracking between the two. Several generator trip events in the Eastern Interconnection System and the Western Electricity Coordinating Council system are recorded and the frequency patterns are analyzed. Our trigger program can detect noticeable frequency drop or rise and sample results are shown in a 13 month period. In addition to transient states' observation, the quasi-steady-state, such as oscillations, can also be observed by FNET. Several potential applications of FNET in the areas of monitoring & analysis, system control, model validation, and others are discussed. Some applications of FNET are still beyond our imagination. / Ph. D.

La pile à combustible apparaît comme une technologie prometteuse pour la conversion énergétique à faible impact environnemental mais sa commercialisation à grande échelle nécessite de relever certains défis économiques et technologiques. Tout d'abord, pour fonctionner, la pile a besoin de systèmes (compresseurs, convertisseurs,...) parfois volumineux et coûteux en énergie. Ensuite, le prix de certains éléments constituants la pile reste élevé car ce sont des produits à haute valeur technologique utilisant des matériaux parfois très onéreux (membrane polymère, couche catalytique,...). L'optimisation du système pile à combustible et des éléments environnants n'est pas le seul défi à relever. En effet, la durabilité des assemblages membrane-électrodes (AME) constitue une barrière majeure à la commercialisation de ces systèmes pour des applications stationnaires ou dans les transports. Afin d'améliorer la durabilité de ces assemblages, il est nécessaire de bien caractériser les différents éléments les constituant et de déterminer et de quantifier les mécanismes de dégradation. Le premier chapitre de cette thèse présente une étude bibliographique sur les PEMFC et l'électrochimie fondamentale régissant le fonctionnement de ces systèmes. Le second chapitre présente les matériaux composant les différents éléments du système ainsi que les méthodes expérimentales utilisées pour caractériser les AME. Le chapitre suivant évoque l'étude et la mise en oeuvre d'une technique électrochimique de caractérisation d'un empilement, notamment la mesure de surface active des différentes cellules. Enfin, le quatrième et dernier chapitre concerne une étude du vieillissement hétérogène d'empilements de trois cellules / Proton exchange membrane (PEM) fuel cells are seen as a promising technology for environmentally friendly energy conversion but its wide spread commercialization need taking up several technological and economic challenges. First, to operate PEM fuel cells require sizeable and energy consuming surrounding systems (compressors, converters,...). Then, elements constituting the cell remain costly because with high technological value and using expensive materials (polymer membrane, catalyst layer,...). The optimization of the system and the surrounding elements is not the only challenge to take up. Indeed, durability of the membrane electrode assembly (MEA) constitutes the major barrier to commercialization of these systems for stationary or transport applications. In order to increase durability of the assemblies, a better understanding of the aging mechanisms is necessary. The first chapter of the thesis introduces a bibliographical study on PEMFC and the fundamental electrochemistry governing the system operation. The second chapter introduces materials composing the different system elements and experimental methods used for PEMFC characterization. The next chapter deals with a study on stack characterization, particularly the development of an electrochemical technique allowing active surface area measurement of the cells composing the stack. Finally, the last chapter deals with heterogeneous aging within PEMFC stacks

abstract: With growing complexity of power grid interconnections, power systems may become increasingly vulnerable to low frequency oscillations (especially inter-area oscillations) and dependent on stabilizing controls using either local signals or wide-area signals to provide adequate damping. In recent years, the ability and potential to use wide-area signals for control purposes has increased since a significant investment has been made in the U. S. in deploying synchrophasor measurement technology. Fast and reliable communication systems are essential to enable the use of wide-area signals in controls. If wide-area signals find increased applicability in controls the security and reliability of power systems could be vulnerable to disruptions in communication systems. Even though numerous modern techniques have been developed to lower the probability of communication errors, communication networks cannot be designed to be always reliable. Given this background the motivation of this work is to build resiliency in the power grid controls to respond to failures in the communication network when wide-area control signals are used. In addition, this work also deals with the delay uncertainty associated with the wide-area signal transmission. In order to counteract the negative impact of communication failures on control effectiveness, two approaches are proposed and both approaches are motivated by considering the use of a robustly designed supplementary damping control (SDC) framework associated with a static VAr compensator (SVC). When there is no communication failure, the designed controller guarantees enhanced improvement in damping performance. When the wide-area signal in use is lost due to a communication failure, however, the resilient control provides the required damping of the inter-area oscillations by either utilizing another wide-area measurement through a healthy communication route or by simply utilizing an appropriate local control signal. Simulation results prove that with either of the proposed controls included, the system is stabilized regardless of communication failures, and thereby the reliability and sustainability of power systems is improved. The proposed approaches can be extended without loss of generality to the design of any resilient controller in cyber-physical engineering systems. / Dissertation/Thesis / Ph.D. Electrical Engineering 2014

The aim of my dissertation work was to create an application for pocket PC with operating system Windows Mobile and touch screen, an application that would enable to position the current location of the pocket PC based on the GPS data, on distance measurement between two and more points of which the location is obtained from GPS, and on measurement of territory surface defined by certain number of points obtained from the GPS. The application also enables to display the characteristics of the received GPS signal, information about the number of visible satellites and also information about maximum deviation from positioning. In order to increase the accuracy of the positioning, an averaging function has been implemented. As additional function, a possibility of route location has been created. It measures the passed distance and records some other route characteristics. The application has been successfully tested on pocket PC E-ten M600+ and GPS receiver Navilock but it has been designed with general-purpose and should be compatible with all devices working with operating system Windows Mobile and touch screen. The text section of my dissertation work describes the positioning principle on the basis of satellites with known position, deals with the accuracy of these systems and describes few possibilities how to increase their accuracy. It also discusses the NMEA 0183 Protocol that is used by the majority of GPS modules for communication. The text section also describes several mathematic and cartographic calculations needed for realization of the application. In the end of the text section there is a detailed description of the created application.

Severe disturbances in a large electrical interconnection cause a large mismatch in generation and load in the network, leading to frequency instability. If the mismatch is not rectified quickly, the system may disintegrate into multiple islands. Though the Automatic Generation Controls (AGC) perform well in correcting frequency deviation over a period of minutes, they are ineffective during a rolling blackout. While traditional Under Frequency Load Shedding Schemes (UFLS) perform quick control actions to arrest frequency decline in an islanded network, they are not designed to prevent unplanned islanding. The proposed Intelligent Load Shedding algorithm combines the effectiveness of AGC Scheme by observing tie line flows and the speed of operation of the UFLS Scheme by shedding loads intelligently, to preserve system integrity in the event of an evolving cascading failure. The proposed scheme detects and estimates the size of an event by monitoring the tie lines of a control area using Wide Area Measurement Systems (WAMS) and initiates load shedding by removing loads whose locations are optimally determined by a sensitivity analysis. The amount and location of the load shedding depends on the location and size of the initiating event, making the proposed algorithm adaptive and selective. Case Studies have been presented to show that control actions of the proposed scheme can directly mitigate a cascading blackout. / Ph. D.