Durante este trabalho foram produzidas amostras vítreas (na forma bulk) de composição Bi2O3-GeO2. Na primeira parte do trabalho foram analisadas condições de preparo. Para analisar a influência do cadinho foram usados cadinhos de alumina (Al2O3) e aluminosilicato (Al2O3 - SiO2) mantendo-se fixas as concentrações de Bi2O3 e temperatura de fusão. Para analisar o efeito da temperatura de fusão foram usadas temperaturas de 1100°C e 1200°C mantendo fixa a concentração de Bi2O3 e o tipo de cadinho. Por último para analisar o efeito da concentração de Bi2O3 foram usadas amostras com diferentes concentrações de 32 %, 42% e 62% (% em peso) mantendo a temperatura de fusão. A segunda parte do trabalho consistiu em analisar a transferência de energia entre os centros de luminescentes Bi+ e os íons de túlio (Tm3+) adicionando 2 % de óxido de túlio (Tm2O3) na composição dos vidros Bi2O3-GeO2, a fim de comparar com resultados da amostra sem o referido dopante. Posteriormente foi adicionada a concentração de 0,05 % de AgNO3 para aumentar a intensidade luminescente da emissão de Tm3+ segundo a teoria do efeito plasmonico, assim como o ganho em 1470 nm. Foi montado posteriormente arranjo para medir o ganho relativo das amostras na forma bulk Bi2O3-GeO2 dopadas com Tm3+, com e sem prata, para justificar a aplicação destes vidros como materiais para uso em dispositivos amplificadores na área de telecomunicação; o uso das amostras na forma de bulk é menos dispendioso do que a fabricação dos dispositivos, e nos permite avaliar o potencial do material previamente. Foram feitas medidas de emissão para comprovar as propriedades fotoluminescentes do material, e medidas de absorção para comprovar a presença de íons de bismuto, plasmon da prata, e incorporação dos íons de Tm3+; as medidas de MET (Microscópio Eletrônico de Transmissão) foram feitas para verificar o tamanho médio das nanopartículas de prata e difração de elétrons para identificar a estrutura cristalina das nanopartículas, comprovando assim a presença da prata nos vidros. Na presença da prata o ganho aumentou em 500% atingindo 4,5 dB/cm. Os resultados que serão reportados mostram o potencial de vidros de composição Bi2O3 - GeO2 com nanopartículas de prata e Tm3+ para aplicações que requeiram luminescência intensa de banda larga na região de 1300 - 1600 nm e amplificação óptica em 1470 nm. / During this work, we produced glass samples (in bulk form) with Bi2O3-GeO2 composition. In the first part of the work, we analyzed the preparation conditions. In order to evaluate the influence of the crucible we used alumina (Al2O3) and aluminosilicate (Al2O3 - SiO2) crucibles, keeping the concentration of Bi2O3 and melting temperature fixed. To analyze the melt temperature we used the temperature of 1100 °C and 1200 °C keeping the concentration of Bi2O3 and type of crucible fixed. Finally, to analyze the effect of the concentration samples we used different concentrations of 32%, 42% and 62% (in % wt) and the melting temperature and the crucible type remained fixed. The second part of the work consisted in evaluating the energy transfer between the Bi+ luminescent centers and the Tm3+ ions by adding 2% of Tm2O3 in the composition of the Bi2O3 - GeO2 glasses, in order to compare the results with those without the rare earth ions. Subsequently, 0.05 wt % of AgNO3 was added to increase the luminescent intensity of thulium ions (Tm3+) according to the theory of the plasmonic effect as well as the gain at 1470 nm. It was later assembled an arrangement to measure the relative gain of bulk samples Bi2O3 - GeO2 doped with thulium oxide (Tm2O3), with and without silver nanoparticles, to justify the application of these glasses as materials to be used in amplifying devices; the use of bulk sample is less expensive than the fabrication of devices and allows us to evaluate previously the material potential. We carried out emission measurements to verify the photoluminescent properties of the material and absorption measurements to verify the concentration of bismuth ions, the silver plasmonic effect, and the incorporation of Tm3+ ions. TEM (Transmission Electron Microscope) was used to verify the average size of silver nanoparticles and electron diffraction to identify the crystalline structure of the nanoparticles and to prove mainly the presence of silver in the glasses. Enhancement of about 500% was observed for the relative gain that reached 4.5 dB/cm. The reported results show the potential of Bi2O3 - GeO2 composite glasses with silver nanoparticles and Tm3+ for applications requiring intense large bandwidth luminescence in the 1300-1600 nm region and optical amplification at 1470 nm.

Durante este trabalho foram produzidas amostras vítreas (na forma bulk) de composição Bi2O3-GeO2. Na primeira parte do trabalho foram analisadas condições de preparo. Para analisar a influência do cadinho foram usados cadinhos de alumina (Al2O3) e aluminosilicato (Al2O3 - SiO2) mantendo-se fixas as concentrações de Bi2O3 e temperatura de fusão. Para analisar o efeito da temperatura de fusão foram usadas temperaturas de 1100°C e 1200°C mantendo fixa a concentração de Bi2O3 e o tipo de cadinho. Por último para analisar o efeito da concentração de Bi2O3 foram usadas amostras com diferentes concentrações de 32 %, 42% e 62% (% em peso) mantendo a temperatura de fusão. A segunda parte do trabalho consistiu em analisar a transferência de energia entre os centros de luminescentes Bi+ e os íons de túlio (Tm3+) adicionando 2 % de óxido de túlio (Tm2O3) na composição dos vidros Bi2O3-GeO2, a fim de comparar com resultados da amostra sem o referido dopante. Posteriormente foi adicionada a concentração de 0,05 % de AgNO3 para aumentar a intensidade luminescente da emissão de Tm3+ segundo a teoria do efeito plasmonico, assim como o ganho em 1470 nm. Foi montado posteriormente arranjo para medir o ganho relativo das amostras na forma bulk Bi2O3-GeO2 dopadas com Tm3+, com e sem prata, para justificar a aplicação destes vidros como materiais para uso em dispositivos amplificadores na área de telecomunicação; o uso das amostras na forma de bulk é menos dispendioso do que a fabricação dos dispositivos, e nos permite avaliar o potencial do material previamente. Foram feitas medidas de emissão para comprovar as propriedades fotoluminescentes do material, e medidas de absorção para comprovar a presença de íons de bismuto, plasmon da prata, e incorporação dos íons de Tm3+; as medidas de MET (Microscópio Eletrônico de Transmissão) foram feitas para verificar o tamanho médio das nanopartículas de prata e difração de elétrons para identificar a estrutura cristalina das nanopartículas, comprovando assim a presença da prata nos vidros. Na presença da prata o ganho aumentou em 500% atingindo 4,5 dB/cm. Os resultados que serão reportados mostram o potencial de vidros de composição Bi2O3 - GeO2 com nanopartículas de prata e Tm3+ para aplicações que requeiram luminescência intensa de banda larga na região de 1300 - 1600 nm e amplificação óptica em 1470 nm. / During this work, we produced glass samples (in bulk form) with Bi2O3-GeO2 composition. In the first part of the work, we analyzed the preparation conditions. In order to evaluate the influence of the crucible we used alumina (Al2O3) and aluminosilicate (Al2O3 - SiO2) crucibles, keeping the concentration of Bi2O3 and melting temperature fixed. To analyze the melt temperature we used the temperature of 1100 °C and 1200 °C keeping the concentration of Bi2O3 and type of crucible fixed. Finally, to analyze the effect of the concentration samples we used different concentrations of 32%, 42% and 62% (in % wt) and the melting temperature and the crucible type remained fixed. The second part of the work consisted in evaluating the energy transfer between the Bi+ luminescent centers and the Tm3+ ions by adding 2% of Tm2O3 in the composition of the Bi2O3 - GeO2 glasses, in order to compare the results with those without the rare earth ions. Subsequently, 0.05 wt % of AgNO3 was added to increase the luminescent intensity of thulium ions (Tm3+) according to the theory of the plasmonic effect as well as the gain at 1470 nm. It was later assembled an arrangement to measure the relative gain of bulk samples Bi2O3 - GeO2 doped with thulium oxide (Tm2O3), with and without silver nanoparticles, to justify the application of these glasses as materials to be used in amplifying devices; the use of bulk sample is less expensive than the fabrication of devices and allows us to evaluate previously the material potential. We carried out emission measurements to verify the photoluminescent properties of the material and absorption measurements to verify the concentration of bismuth ions, the silver plasmonic effect, and the incorporation of Tm3+ ions. TEM (Transmission Electron Microscope) was used to verify the average size of silver nanoparticles and electron diffraction to identify the crystalline structure of the nanoparticles and to prove mainly the presence of silver in the glasses. Enhancement of about 500% was observed for the relative gain that reached 4.5 dB/cm. The reported results show the potential of Bi2O3 - GeO2 composite glasses with silver nanoparticles and Tm3+ for applications requiring intense large bandwidth luminescence in the 1300-1600 nm region and optical amplification at 1470 nm.

Long term supporting schemes for photovoltaic (PV) system installation have led to accommodating large numbers of PV systems within load pockets in distribution grids. High penetrations of PV systems can cause new technical challenges, such as voltage rise due to reverse power flow during light load and high PV generation conditions. Therefore, new strategies are required to address the associated challenges. Moreover, due to these changes in distribution grids, a different response behavior of the distribution grid on the transmission side can be expected. Hence, a new equivalent model of distribution grids with high penetration of PV systems is needed to be addressed for future power system studies. The thesis contributions lie in three parts. The first part of the thesis copes with the PV modelling. A non-proprietary PV model of a three-phase, single stage PV system is developed in PSCAD/EMTDC and PowerFactory. Three different reactive power regulation strategies are incorporated into the models and their behavior are investigated in both simulation platforms using a distribution system with PV systems. In the second part of the thesis, the voltage rise problem is remedied by use of reactive power. On the other hand, considering large numbers of PV systems in grids, unnecessary reactive power consumption by PV systems first increases total line losses, and second it may also jeopardize the stability of the network in the case of contingencies in conventional power plants, which supply reactive power. Thus, this thesis investigates and develops the novel schemes to reduce reactive power flows while still keeping voltage within designated limits via three different approaches: decentralized voltage control to the pre-defined set-points developing a coordinated active power dependent (APD) voltage regulation Q(P)using local signals developing a multi-objective coordinated droop-based voltage (DBV) regulation Q(V) using local signals   In the third part of the thesis, furthermore, a gray-box load modeling is used to develop a new static equivalent model of a complex distribution grid with large numbers of PV systems embedded with voltage support schemes. In the proposed model, variations of voltage at the connection point simulate variations of the model’s active and reactive power. This model can simply be integrated intoload-flow programs and replace the complex distribution grid, while still keepingthe overall accuracy high. The thesis results, in conclusion, demonstrate: i) using rms-based simulations in PowerFactory can provide us with quite similar results using the time domain instantaneous values in PSCAD platform; ii) decentralized voltage control to specific set-points through the PV systems in the distribution grid is fundamentally impossible dueto the high level voltage control interaction and directionality among the PV systems; iii) the proposed APD method can regulate the voltage under the steady-state voltagelimit and consume less total reactive power in contrast to the standard characteristicCosφ(P)proposed by German Grid Codes; iv) the proposed optimized DBV method can directly address voltage and successfully regulate it to the upper steady-state voltage limit by causing minimum reactive power consumption as well as line losses; v) it is beneficial to address PV systems as a separate entity in the equivalencing of distribution grids with high density of PV systems. / <p>The Doctoral Degrees issued upon completion of the programme are issued by Comillas Pontifical University, Delft University of Technology and KTH Royal Institute of Technology. The invested degrees are official in Spain, the Netherlands and Sweden, respectively. QC 20141028</p>