Thesis (Ph. D.)--University of California, San Diego, 2007. / Title from first page of PDF file (viewed January 8, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 112-124).

Thesis (Ph. D.), Memorial University of Newfoundland, 1999. / Bibliography: p. 179-186.

Thesis (Ph. D.)--Carleton University, 1997. / Also available in electronic format on the Internet.

Thesis (M.S.)--Cleveland State University, 2010. / Abstract. Title from PDF t.p. (viewed on June 3, 2010). Includes bibliographical references (p. 118-120). Available online via the OhioLINK ETD Center and also available in print.

Dentre as fontes de energia renováveis utilizadas para geração de energia elétrica a que mais se destaca atualmente e a energia eólica. 0 crescente índice de penetração da geração eólica na matriz energética dos sistemas de potencia impõe a necessidade da revisão de conceitos anteriormente estabelecidos sobre a estabilidade de sistemas de potencia, uma vez que ainda não e perfeitamente compreendida a influencia de uma maior integração deste recurso no comportamento dos sistemas de potencia. Este trabalho tem como foco o estudo da estabilidade de sistemas com aerogeradores de velocidade fixa equipados com geradores de indução de rotor em gaiola. E estudada a estabilidade angular de um sistema de geração eólica equipado com aerogeradores desta natureza. O problema da estabilidade foi decomposto em três partes: estabilidade estática, estabilidade dinâmica e estabilidade transitória. São definidos os modelos dos componentes do aerogerador para cada um dos estudos realizados. A topologia adotada á a máquina Barramento Infinito (MBI), na qual o restante do sistema de potência a representado pelo seu equivalente de Thevenin. Esta topologia típica de analise de estabilidade de sistemas de potencia e adotada por permitir a obtenção de resultados analíticos para as analises estática e dinâmica. A analise transitória se dá através de simulações computacionais. A fim de manter um caráter mais geral para os resultados as simulações são realizados com três aerogeradores de características distintas. Os resultados obtidos permitem uma melhor compreensão da influencia sobre a estabilidade do sistema de geração eólica dos parâmetros de rede do sistema de potencia como: potencia de curto-circuito do ponto de conexão comum com o sistema de potencia, relação X/R da linha de transmissão e do capacitor de compensação de fator de potencia. / Among the renewable energy sources used to generate electric power one of the most important at this time is the wind power. The growing penetration index of wind power in the power systems energetic matrix leads to the necessity of a reevaluation of the concepts previously established about the stability of power systems, since the influence of a major integration of this resource in the behavior of power systems is not perfectly understood. This work focuses on the stability study of wind power systems equiped with fixed-speed squirrel-cage induction generators. The angular stability of a wind generation system equipped with wind generators of this nature is studied. The stability problem was decomposed in three parts: static stability, dynamic stability and transient stability. The models of the components of the wind generator are defined for each of the studies. The considered topology was an Induction Generator Infinite Bus System (IBM), where the rest of the power system is represented by it’s Thévenin equivalent. This is a typical topology in power systems stability analysis and is adopted in this work aiming at obtaining analytical and general stability results. The transient analysis is performed by computer simulations. In order to provide more generatily to the stability results, all simulations are conducted with three wind generators with distinct characteristics. The obtained results allow a better comprehension about the influence, on the stability of wind power systems, of power system network parameters as: short-circuit capacity of the common connection point with the power system, the X/R relation of the transmission line and the power factor compensation capacitor.

Dentre as fontes de energia renováveis utilizadas para geração de energia elétrica a que mais se destaca atualmente e a energia eólica. 0 crescente índice de penetração da geração eólica na matriz energética dos sistemas de potencia impõe a necessidade da revisão de conceitos anteriormente estabelecidos sobre a estabilidade de sistemas de potencia, uma vez que ainda não e perfeitamente compreendida a influencia de uma maior integração deste recurso no comportamento dos sistemas de potencia. Este trabalho tem como foco o estudo da estabilidade de sistemas com aerogeradores de velocidade fixa equipados com geradores de indução de rotor em gaiola. E estudada a estabilidade angular de um sistema de geração eólica equipado com aerogeradores desta natureza. O problema da estabilidade foi decomposto em três partes: estabilidade estática, estabilidade dinâmica e estabilidade transitória. São definidos os modelos dos componentes do aerogerador para cada um dos estudos realizados. A topologia adotada á a máquina Barramento Infinito (MBI), na qual o restante do sistema de potência a representado pelo seu equivalente de Thevenin. Esta topologia típica de analise de estabilidade de sistemas de potencia e adotada por permitir a obtenção de resultados analíticos para as analises estática e dinâmica. A analise transitória se dá através de simulações computacionais. A fim de manter um caráter mais geral para os resultados as simulações são realizados com três aerogeradores de características distintas. Os resultados obtidos permitem uma melhor compreensão da influencia sobre a estabilidade do sistema de geração eólica dos parâmetros de rede do sistema de potencia como: potencia de curto-circuito do ponto de conexão comum com o sistema de potencia, relação X/R da linha de transmissão e do capacitor de compensação de fator de potencia. / Among the renewable energy sources used to generate electric power one of the most important at this time is the wind power. The growing penetration index of wind power in the power systems energetic matrix leads to the necessity of a reevaluation of the concepts previously established about the stability of power systems, since the influence of a major integration of this resource in the behavior of power systems is not perfectly understood. This work focuses on the stability study of wind power systems equiped with fixed-speed squirrel-cage induction generators. The angular stability of a wind generation system equipped with wind generators of this nature is studied. The stability problem was decomposed in three parts: static stability, dynamic stability and transient stability. The models of the components of the wind generator are defined for each of the studies. The considered topology was an Induction Generator Infinite Bus System (IBM), where the rest of the power system is represented by it’s Thévenin equivalent. This is a typical topology in power systems stability analysis and is adopted in this work aiming at obtaining analytical and general stability results. The transient analysis is performed by computer simulations. In order to provide more generatily to the stability results, all simulations are conducted with three wind generators with distinct characteristics. The obtained results allow a better comprehension about the influence, on the stability of wind power systems, of power system network parameters as: short-circuit capacity of the common connection point with the power system, the X/R relation of the transmission line and the power factor compensation capacitor.

Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. / Globally governments are faced with challenges in the energy sector which are exacerbated by uncertain financial markets and resource limitations. The over utilization of fossil fuels for electricity generation has had a profound impact on the climatic conditions on earth. Coal power stations release carbon dioxide (CO2) during the combustion process and studies show that concentrations have sharply risen in the atmosphere. Adverse environmental conditions like global warming exist as a result of high greenhouse gas (GHG) emissions in particular CO2. In 2015 Eskom constructed Sere Wind farm with a supply capability of 100 MW. Due to the lack of technical expertise and skills with regard to the new technology within Eskom, Siemens was offered a 5 year maintenance contract. Siemens also provides training on basic operation and maintenance (O&M) of the wind farm to Eskom staff. This excludes specialised training on Siemens Turbine Condition Monitoring (TCM) systems which is a critical part to develop optimum maintenance strategies. This shortage of specialised skills in the application of condition monitoring techniques within Eskom is a major concern. If the most cost effective maintenance strategies during the contract period are implemented, the long term plant health and design life of Sere wind farm will be reduced. There is a need to develop new condition monitoring techniques to complement or address the shortcomings of the existing systems. Developing these skills will increase the understanding of the technology and improve the operating and maintenance of Sere wind farm.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / Fixed speed wind turbines completely dominated the market until the mid-1990s and currently. Although most installed wind turbine are variable speed, many fixed speed wind are still in operation. In this context, this work presents a study concerned to coordinated operation of FACTS (Flexible Alternating Current Transmission Systems) device with fixed speed wind energy conversion system (WECS) equipped with a squirrel cage induction generator. The applied FACTS device is based on the control strategy of the Unified Conditioner Power Quality with inverted topology (i-UPQC), and consists of two static converters connected in back-to-back topology. A model was developed in the software PSCAD/EMTDC, tested under four different scenarios and discussed in order to validate the presented theory. The i-UPQC performance was analyzed for improving voltage quality in the point of common coupling (PCC), reduction of the harmonic currents drained from the wind turbine, and increasing the induction generator capacity to remain connected during a momentary collapse in the grid voltage. The i-UPQC presented good performance due to its capability to warrant the quality in the PCC voltage in spite of the wind variation and that the voltage sags at the PCC do not change the stator voltages. About the generator current, the i-UPQC has kept the stator current free of harmonic components and the effect of unbalanced loads. Under normal operation it was demonstrated that one of the I-UPQC converters can be sized as 50\% of the generator rated power, which is an advantage for real implementation. A comparison between two ways to connect the I-UPQC to the grid, along with the wind turbine, was made. The series converter connected between the wind turbine and the parallel converter, or between parallel converter and the common connection point (PCC). It was concluded that the shunt converter connected to the generator presents better performance than the series converter due to series converter currents are less than the stator currents. Under this configuration, there is no active power current from the generator injected in the PCC during voltage sags. / Turbinas de velocidade fixa dominaram completamente o mercado atà meados de 1990 e atualmente, apesar da maioria dos aerogeradores instalados serem de velocidade variÃvel, muitos aerogeradores de velocidade fixa ainda se encontram em funcionamento. Neste contexto, este trabalho apresenta um estudo sobre a operaÃÃo coordenada de um dispositivo FACTS (Flexible Alternating Current Transmission Systems) com um aerogerador de velocidade fixa, equipado com gerador de induÃÃo gaiola de esquilo. O dispositivo FACTS aplicado baseia-se na estratÃgia de controle do Condicionador Unificado de Qualidade de Energia com topologia invertida (i-UPQC, do inglÃs, Unified Power Quality Conditioner with inverted topology), e consiste de dois conversores estÃticos na configuraÃÃo back-to-back. Um modelo foi desenvolvido no software PSCAD/EMTDC e quatro cenÃrios diferentes foram simulados e discutidos a fim de validar a teoria apresentada. A partir dos resultados de simulaÃÃo, foi analisado o desempenho do i-UPQC para melhoria da qualidade da tensÃo no Ponto de ConexÃo Comum (PCC), diminuiÃÃo das correntes harmÃnicas drenadas do aerogerador e aumento da capacidade do gerador de induÃÃo de se manter conectado durante um afundamento momentÃneo da tensÃo da rede. O i-UPQC atuou de forma satisfatÃria, pois nÃo permitiu que variaÃÃes na velocidade do vento afetassem a qualidade da tensÃo fornecida ao PCC, nem que o afundamento da tensÃo no PCC alterasse a tensÃo nos terminais do estator. Quando cargas nÃo lineares foram adicionadas no sistema, o i-UPQC manteve a corrente do estator livre das componentes harmÃnicas e desbalanÃos presentes na corrente da carga. Demonstrou-se que, em condiÃÃes normais de operaÃÃo, um dos conversores do i-UPQC pode ser especificado para 50\% da potÃncia nominal do aerogerador, o que pode representar uma vantagem do i-UPQC para o caso de uma implementaÃÃo real. Foi feita uma comparaÃÃo entre duas diferentes configuraÃÃes de conexÃo do i-UPQC com o aerogerador e a rede: ora com o conversor paralelo conectado entre o conversor sÃrie e o ponto de conexÃo comum (PCC), ora conectado entre o aerogerador e o conversor sÃrie. Concluiu-se que a configuraÃÃo com o conversor paralelo conectado ao aerogerador à mais vantajosa, pois a corrente que circula atravÃs do conversor sÃrie à menor que a corrente do estator. Nesta configuraÃÃo, nenhuma corrente referente à potÃncia ativa do aerogerador à injetada no PCC durante um afundamento de tensÃo.

Dentre as fontes de energia renováveis utilizadas para geração de energia elétrica a que mais se destaca atualmente e a energia eólica. 0 crescente índice de penetração da geração eólica na matriz energética dos sistemas de potencia impõe a necessidade da revisão de conceitos anteriormente estabelecidos sobre a estabilidade de sistemas de potencia, uma vez que ainda não e perfeitamente compreendida a influencia de uma maior integração deste recurso no comportamento dos sistemas de potencia. Este trabalho tem como foco o estudo da estabilidade de sistemas com aerogeradores de velocidade fixa equipados com geradores de indução de rotor em gaiola. E estudada a estabilidade angular de um sistema de geração eólica equipado com aerogeradores desta natureza. O problema da estabilidade foi decomposto em três partes: estabilidade estática, estabilidade dinâmica e estabilidade transitória. São definidos os modelos dos componentes do aerogerador para cada um dos estudos realizados. A topologia adotada á a máquina Barramento Infinito (MBI), na qual o restante do sistema de potência a representado pelo seu equivalente de Thevenin. Esta topologia típica de analise de estabilidade de sistemas de potencia e adotada por permitir a obtenção de resultados analíticos para as analises estática e dinâmica. A analise transitória se dá através de simulações computacionais. A fim de manter um caráter mais geral para os resultados as simulações são realizados com três aerogeradores de características distintas. Os resultados obtidos permitem uma melhor compreensão da influencia sobre a estabilidade do sistema de geração eólica dos parâmetros de rede do sistema de potencia como: potencia de curto-circuito do ponto de conexão comum com o sistema de potencia, relação X/R da linha de transmissão e do capacitor de compensação de fator de potencia. / Among the renewable energy sources used to generate electric power one of the most important at this time is the wind power. The growing penetration index of wind power in the power systems energetic matrix leads to the necessity of a reevaluation of the concepts previously established about the stability of power systems, since the influence of a major integration of this resource in the behavior of power systems is not perfectly understood. This work focuses on the stability study of wind power systems equiped with fixed-speed squirrel-cage induction generators. The angular stability of a wind generation system equipped with wind generators of this nature is studied. The stability problem was decomposed in three parts: static stability, dynamic stability and transient stability. The models of the components of the wind generator are defined for each of the studies. The considered topology was an Induction Generator Infinite Bus System (IBM), where the rest of the power system is represented by it’s Thévenin equivalent. This is a typical topology in power systems stability analysis and is adopted in this work aiming at obtaining analytical and general stability results. The transient analysis is performed by computer simulations. In order to provide more generatily to the stability results, all simulations are conducted with three wind generators with distinct characteristics. The obtained results allow a better comprehension about the influence, on the stability of wind power systems, of power system network parameters as: short-circuit capacity of the common connection point with the power system, the X/R relation of the transmission line and the power factor compensation capacitor.

<p>Red spruce forests, one of the most critically endangered ecosystems in the United States</p>provides critical habitat for several endemic species or subspecies of the Appalachian Mountains, including the Virginia northern flying squirrel. Once listed as threatened under the Endangered Species Act, the Virginia northern flying squirrel was delisted in 2013. Managers are currently focusing their efforts on projects that increase the extent and connectivity of the squirrel’s habitat through red spruce restoration. At present, there is a paucity of available data to assess the implications of the silvicultural activities associated with red spruce restoration on the movement and occupancy of the Virginia northern flying squirrel. In order to inform management activities, I measured home range, fine-scale habitat use, and estimated detection and occupancy for northern flying squirrels across a gradient of red spruce stands in the Monongahela National Forest. I concluded that home ranges for northern flying squirrels within this region are comprised primarily of red spruce and that northern flying squirrels were selecting larger diameter trees compared to the nearest available neighbor. Additionally, I found that microhabitat characteristics alone did not sufficiently predict northern flying squirrel occupancy and that acoustic methods for surveying northern flying squirrels will require further refinement. Future research efforts should focus on a combination of landscape-level and microhabitat covariates to best predict occupancy of this species across the landscape. Future red spruce management should be approached with caution regarding the potential impact on northern flying squirrel habitat in the short-term. I recommended using spatially-explicit modeling to assess the long-term effects of proposed red spruce restoration projects on northern flying squirrel population demographics, dispersal, and metapopulation connectivity prior to the implementation of silvicultural treatments.