Subsea DC Collection Grid with High Power Security for Offshore Renewables

This work was supported by the Engineering and Physical Sciences Research Council [grant number EP/K006428/1]; and the European Regional Development Fund [grant number LUPS/ERDF/2010/4/1/0164].

DC fault performance and cost analysis of DC grids for connecting multiple offshore wind farms

ACKNOWLEDGMENT We are thankful to RTE for financial support of this project.

BIDIRECTIONAL AC-DC CONVERTERS USING ONE CYCLE CONTROL (OCC) FOR ELECTRIC VEHICLES

The electric vehicle (EV) market has seen a rapid growth in the recent past. With an increase in the number of electric vehicles on road, there is an increase in the number of high capacity battery banks interfacing the grid. The battery bank of an EV, besides being the fuel tank, is also a huge energy storage unit. Presently, it is used only when the vehicle is being driven and remains idle for rest of the time, rendering it underutilized. Whereas on the other hand, there is a need of large energy storage units in the grid to filter out the fluctuations of supply and demand during a day. EVs can help bridge this gap. The EV battery bank can be used to store the excess energy from the grid to vehicle (G2V) or supply stored energy from the vehicle to grid (V2G ), when required. To let power flow happen, in both directions, a bidirectional AC-DC converter is required. This thesis concentrates on the bidirectional AC-DC converters which have a control on power flow in all four quadrants for the application of EV battery interfacing with the grid. This thesis presents a bidirectional interleaved full bridge converter topology. This helps in increasing the power processing and current handling capability of the converter which makes it suitable for the purpose of EVs. Further, the benefit of using the interleaved topology is that it increases the power density of the converter. This ensures optimization of space usage with the same power handling capacity. The proposed interleaved converter consists of two full bridges. The corresponding gate pulses of each switch, in one cell, are phase shifted by 180 degrees from those of the other cell. The proposed converter control is based on the one-cycle controller. To meet the challenge of new requirements of reactive power handling capabilities for grid connected converters, posed by the utilities, the controller is modified to make it suitable to process the reactive power. A fictitious current derived from the grid voltage is introduced in the controller, which controls the converter performance. The current references are generated using the second order generalized integrators (SOGI) and phase locked loop (PLL). A digital implementation of the proposed control ii scheme is developed and implemented using DSP hardware. The simulated and experimental results, based on the converter topology and control technique discussed here, are presented to show the performance of the proposed theory.

Digital geometric-sequence control technique for bidirectional dual active bridge DC-DC converters used in future electric vehicles

Bidirectional DC-DC converters are widely used in different applications such as energy storage systems, Electric Vehicles (EVs), UPS, etc. In particular, future EVs require bidirectional power flow in order to integrate energy storage units into smart grids. These bidirectional power converters provide Grid to Vehicle (V2G)/ Vehicle to Grid (G2V) power flow capability for future EVs. Generally, there are two control loops used for bidirectional DC-DC converters: The inner current loop and The outer loop. The control of DAB converters used in EVs are proved to be challenging due to the wide range of operating conditions and non-linear behavior of the converter. In this thesis, the precise mathematical model of the converter is derived and non-linear control schemes are proposed for the control system of bidirectional DC-DC converters based on the derived model. The proposed inner current control technique is developed based on a novel Geometric-Sequence Control (GSC) approach. The proposed control technique offers significantly improved performance as compared to one for conventional control approaches. The proposed technique utilizes a simple control algorithm which saves on the computational resources. Therefore, it has higher reliability, which is essential in this application. Although, the proposed control technique is based on the mathematical model of the converter, its robustness against parameter uncertainties is proven. Three different control modes for charging the traction batteries in EVs are investigated in this thesis: the voltage mode control, the current mode control, and the power mode control. The outer loop control is determined by each of the three control modes. The structure of the outer control loop provides the current reference for the inner current loop. Comprehensive computer simulations have been conducted in order to evaluate the performance of the proposed control methods. In addition, the proposed control have been verified on a 3.3 kW experimental prototype. Simulation and experimental results show the superior performance of the proposed control techniques over the conventional ones.

Validação da Versão Portuguesa da Center for Epidemiologic Studies Depression Scale for Children (CES-DC)

A Depressão na infância e adolescência, tal como na população adulta, é uma das perturbações mentais mais comuns. Uma vez que o seu aparecimento nestas faixas etárias conduz a graves consequências na idade adulta, é fundamental identificar os sintomas depressivos precocemente. Desta forma, os instrumentos de autorrelato têm um papel fundamental, uma vez que permitem com facilidade, de forma fidedigna e válida, ter acesso a formas de pensar, sentir e agir dos sujeitos. O objetivo do presente trabalho consistiu na tradução, adaptação e estudo da Center for Epidemiological Studies Depression Scale for Children (CES-DC) (Weissman, Orvash & Padian, 1980) para os adolescentes portugueses. A amostra é constituída por 417 adolescentes, com idades compreendidas entre os 12 e os 18 anos a frequentar o 3º ciclo do ensino básio e ensino secundário. Para o estudo da validade convergente e divergente da CES-DC, foram utilizados a Depression Anxiety Stress Scales (DASS 21) (Lovibond & Lovibond, 1995), o Children's Depresssion Inventory (CID) (Marujo, 1994) e a Students' Life Satisfaction Scale (SLSS) (Marques, Pais-Ribeiro & Lopez, 2007) que avaliam, respetivamente, os estados emocionais negativos (depressão, ansiedade e stress), a sintomatologia depressiva e a satisfação global com a vida. Os resultados obtidos mostram que a escala possui uma boa consistência interna, uma estabilidade temporal adequada, assim como uma boa validade. Sugerem, ainda, tratar-se de uma escala tridimensional: fator humor, fator interpessoal e fator felicidade. Estes dados permitem o avanço da Psicologia, no que diz respeito à avaliação e prática clínica com adolescentes. A utilidade do questionário deve ser verificada noutras faixas etárias, principalmente, nas de menos de 12 anos de idade, e também numa amostra clínica. Não obstante as limitações apontadas, os resultados sugerem que a CES-DC é um questionário útil na avaliação de sintomas depressivos nos adolescentes. / Depression in children and adolescents, as well as in adults, is one of the most common mental disorders. Since its appearance in these age groups leads to serious consequences in adulthood, it is critical to identify depressive symptoms in early stages. Therefore, self-report instruments play a key role in this contexto since they allow to easily, reliably and validly have access to ways the subject thinks, feels and acts. The aim of this study was to translate, adapt and study the Center for Epidemiological Studies Depression Scale for Children (CES-DC) (Weissman, Orvash & Padian, 1980) for portuguese adolescents. The sample consists of 417 adolescents, aged between 12 and 18 years old, attending the 3rd cycle of basic education and secondary education schools. To study the convergent and divergent validity of the CES-DC, the Depression Anxiety Stress Scales (DASS 21) (Lovibond & Lovibond, 1995) was used, along with the Children's depression Inventory (CDI) (Sailor, 1994) and the Students' Life Satisfaction Scale (SLSS) (Marques, Pais-Ribeiro & Lopez, 2007) that evaluate, respectively, the negative emotional states (depression, anxiety and stress), depressive symptoms and overall satisfaction with life. The results show that the evaluated scale presents a good internal consistency, an adequate temporal stability as well as good validity. They also suggest that this is a three-dimensional scale: humor factor, interpersonal factor and happiness factor. These data allow for the progress of psychology, regarding the assessment and clinical practice among adolescents. The usefulness of the questionnaire should be verified in other age groups, especially in children with less than 12 years old and in a clinical sample. Despite these limitations, the results suggest that CES-DC is useful in the assessment questionnaire of depressive symptoms in adolescents.

Estudo anatômico de trembleya phlogiformis dc.

v. 13, n. 2, p. 82-92, 2016.

Controle de uma microrrede ilhada baseada em geração eólica-diesel com alto nível de inserção de geração eólica

The insertion of distributed generation units in the electric power systems have contributed to the popularization of microgrid concepts. With the microgrids, several potential benefits can be achieved in regard to power quality and supply reliability. However, several technical challenges related to the control and operation of microgrids, which are associated with high insertion of generation systems based on static converters, must be overcame. Among the opportunities in the context of microgrids, there is the islanded operation of microgrids temporarily disconnected from the electric power systems and also the autonomous operation of geographically isolated microgrids. The frequency in large power systems is traditionally controlled by the generation units based on traditional synchronous generator. The insertion of distributed generation units based on static power converters may bring difficulties to the frequency control in microgrids, due to the reduction of the equivalent inertia of conventional synchronous generators present in islanded and isolated microgrids. In this context, it becomes necessary the proposition of new operational and control strategies for microgrids control, taking into account the presence of distributed generation units based on full-rated converter. This paper proposes an operational and control strategy for the islanded operation of a winddiesel microgrid with high insertion level of wind generation. The microgrid adopted in this study comprises of a wind energy conversion system with synchronous generator based on full rated converter, a diesel generator (DIG) and a dump load. Due to the high insertion level of wind generation, the wind unit operates in Vf mode and the diesel generator operates in PQ mode. The diesel generator and the dump load are used to regulate the DC-link voltage of the wind generation unit. The proposed control allows the islanded operation of the microgrid only with wind generation, wind-only mode (WO), and with wind-diesel generation, wind-diesel mode (WD). For the wind-only mode, with 100% of penetration level of wind generation, it is proposed a DC-link voltage control loop based on the use of a DC dump load. For the winddiesel mode, it is proposed a DC-link voltage control loop added to the diesel generator, which is connected to the AC side of the microgrid, in coordinated action with the dump load. The proposed operational and control strategy does not require the use of batteries and aims to maximize the energy production from wind generation, ensuring the uninterrupted operation of the microgrid. The results have showed that the operational and control strategy allowed the stable operation of the islanded microgrid and that the DC-link voltage control loop added to the diesel generator and the dump load proved to be effective during the typical variations of wind speed and load.

QUALIDADE FISIOLÓGICA DE SEMENTES DE Tabernaemontana fuchsiaefolia A. DC EM FUNÇÃO DO TESTE DE ENVELHECIMENTO ACELERADO1

Tabernaemontana fuchsiaefolia A. DC é uma espécie da família Apocynaceae, nativa do Brasil, com característica invasora, possuindo potencial para uso em recuperação de áreas degradadas. O trabalho teve o objetivo de avaliar a influência dos métodos de envelhecimento acelerado sobre a qualidade fisiológica e germinação de sementes, utilizando-se o método tradicional e em solução de NaCl, empregando-se a metodologia de gerbox, formando minicâmaras de envelhecimento, em três temperaturas (41, 43 e 45°C) e cinco tempos de envelhecimento (0, 24, 48, 72 e 96 horas). As sementes, após o envelhecimento, foram colocadas para germinar em rolos de papel germitest, em quatro repetições de 25 sementes, em câmaras BOD a temperatura de 30°C, com fotoperíodo de 8 horas. O efeito da temperatura foi comparado pelo teste de Tukey em nível de 5% de probabilidade e o efeito do tempo de envelhecimento, pela análise de regressão. Após 35 dias, foram avaliados percentual, índice de velocidade, tempo médio e frequência da germinação, bem como comprimento de raiz e parte aérea, massa seca de plântulas e percentual de plântulas normais. Observou-se que o método alternativo de envelhecimento com solução de NaCl teve pouca influência na qualidade das sementes, não sendo indicado para testes de vigor para a espécie. O método tradicional, na temperatura de 45°C em período de envelhecimento de 96 horas, promoveu queda na germinação e pode ser utilizado para testar o vigor de sementes de leiteira.

Floral expression and pollen germination ability in productive mountain papaya ( Vasconcellea pubescens A.DC.) orchards

Mountain papaya ( Vasconcellea pubescens A.DC.) is described as trioecious in the centers of origin of Ecuador, Colombia, and Peru. However, under cultivation conditions in La Serena (30° S, 70° W), Chile, it is found to be dioecious and monoecious. The objective was to learn about the variations in floral expression of mountain papaya. Flowers from monoecious and dioecious plants were therefore identified and quantified during two seasons. In vitro pollen germination ability was also evaluated based on the factors of site, season, and plant sex. Monoecious plant inflorescences are polygamous; female and male flowers are observed, as well as bisexual flowers that are usually deformed. This condition allows them to be classified as an ambisexual plant. The existence of flowers of different sexes appears to depend on the season; the female dioecious plant is maintained as such, independently of climatic conditions. Pollen from male flowers, from both ambisexual and male plants, germinates 75% in summer, while germination decreases to 56% in spring (P ≤ 0.05). Flowering of female plants coincides with the permanent occurrence of male flowers in ambisexual plants, which ensures pollination without the need for male plants as pollinators in orchards. Based on this information, some management practices and possible lines of research about this species are proposed.

Participación ciudadana en el desarrollo de la localidad de Chapinero, Bogotá DC 2013-2014

Tesis (Maestría en Estudios y Gestión del Desarrollo).-- Universidad de La Salle. Maestría en Estudios y Gestión del Desarrollo, 2014

Germinação e armazenamento de sementes de COCA (Erythroxylum ligustrinum DC. - Erythroxylaceae)

O objetivo deste trabalho foi avaliar o efeito da temperatura sobre a germinação e o armazenamento de sementes de Erythroxylum ligustrinum DC. As sementes foram colocadas germinar caixas de plásticas sobre duas folhas de papel, umedecidas com Nistatina 0, 2%, mantidas em germinadores nas temperaturas constantes de 5, 10, 15, 20, 25, 30, 35, 40 e 45ºC e com fotoperíodo de 12 horas. Para o armazenamento, as sementes foram colocadas em sacos de papel, mantidos à temperatura ambiente e em geladeira. em seguida, mensalmente, foi avaliada a germinação das sementes. A temperatura mínima, a faixa de temperatura ideal e a temperatura máxima para germinação de sementes de coca estão entre 10 e 15ºC, 25 e 30ºC e 40 e 45ºC, respectivamente. O armazenamento de sementes coca por longo período é inviável em embalagens de papel na geladeira (10ºC ± 2) e em temperatura ambiente (27ºC ± 5).