Die vorliegende Dissertation untersucht die Stabilität und Regelung von Stromnetzen mit hohem Anteil Erneuerbarer Energien (EE). Dabei stehen drei Forschungsfragen, zu den neuartigen Herausforderungen für die zukünftige Stromnetzstabilität im Zuge der Energiewende, im Vordergrund. Erstens soll untersucht werden wie die Resilienz von Stromnetzen gemessen und im zweiten Schritt auch verbessert werden kann. Dabei zeige ich den notwendigen Detailgrad für transiente Stabilitätsuntersuchungen auf. Die zweite Frage lautet wie, trotz des zunehmenden Ausbaus von EE in Verteilnetzen, die statische Spannungsstabilität garantiert und Leitungsüberlastungen verhindert werden können. Hierfür analysiere ich mit einem konzeptionellen hierarchischen Verteilnetzmodell das zukünftige Potential für die Erzeugung von Blindleistung aus dezentralen Ressourcen am Beispiel Deutschlands. Die dritte Frage, wie eine dynamisch-stabile Integration von EE möglich ist, bildet den Hauptfokus meiner Dissertation. Dabei untersuche ich wie neuartige dynamische Aspekte EE, wie intermittente Fluktuationen oder auch Mess- und Reaktionszeiten von Leistungselektronik, die dynamische Netzstabilität beeinflussen und wie mögliche Instabilitäten durch Konzepte der Nachfragesteuerung behoben werden können. Dabei stoße ich bei der Analyse lokaler intermittenter Fluktuationen in ohmschen Verteilnetzen auf ein bemerkenswertes Wechselspiel zwischen Eigenschaften der Netzdynamik und -topologie. Als Zweites zeige ich wie mit der Einführung von Leistungselektronik und den damit verbundenen Mess- und Reaktionszeiten Resonanzkatastrophen hervorrufen werden können. Schließlich präsentiere ich wie die dezentrale Nachfragesteuerung von Elektroautos dynamische Instabilitäten, hervorgerufen durch Fluktuationen von EE, bereinigen kann. Zusammenfassend behandelt diese Arbeit verschiedene Aspekt zur Stabilität zukünftiger Stromnetze und integriert dabei sukzessive neuartige dynamische Aspekte von EE. / This PhD thesis is centered around the "Stability and Control of Power Grids with high Renewable Energy Share". With a conceptual modelers approach, I tackle three overarching questions related to the novel challenges the energy transition poses for the stability of future power grids. The first question focuses on how to measure and subsequently improve the resilience of a power grid. Here, I contribute important insights on the necessary model detail for transient stability assessments. The second question concerns how to ensure static voltage stability and avoid capacity overloading while the deployment of Renewable Energy Sources (RES) in the distribution grid layers is massively increasing. As a possible solution to this problem I analyze the future technical potential of reactive power provision from decentral resources in Germany. The third question, and main focus of this thesis, is on how to integrate renewable energies in a dynamically stable way. Specifically, I investigate the influence of intermittent RES and measurement delays from power electronic resources on frequency stability and how the latter can be restored by concepts of demand control. First, for local intermittent fluctuations in lossy distribution grids I find a remarkable and subtle but robust interplay of dynamical and topological properties, which is largely absent for lossless grids. Second, I show how delays may induce resonance catastrophes and how the existence of critical delays sets an upper limit for measurement times. Third and last, I present how the right parameterization of decentral electric vehicle control can completely overcome issues of short-term dynamic instability related to RES fluctuations. This control avoids demand synchronization and high battery stress. Altogether, this thesis investigates the stability of future power grids moving towards integrating more aspects of renewable energy dynamics. Finally, I point out open questions to encourage further research.

La simulation numérique des écoulements (CFD) est largement utilisée aujourd'hui dans l'industrie aéronautique, de l'avant-projet à la conception des appareils. En parallèle, la puissance des calculateurs s'est accrue, permettant d'effectuer des simulations résolvant les équations de Navier-Stokes moyennées (RANS) dans un délai de restitution acceptable du point de vue industriel. Cependant, les configurations simulées sont de plus en plus complexes géométriquement, rendant la réalisation du maillage très coûteuse en temps humain. Notre objectif est de proposer une méthode permettant de simplifier la génération de maillages autour de géométries complexes, en exploitant les avantages de la méthode Chimère, tout en levant les difficultés principales rencontrées par cette méthode dans le calcul des connectivités. Dans notre approche, le domaine de calcul est découpé en régions proches et en régions éloignées des corps. Des grilles curvilignes de faible extension décrivent les régions autour des corps. Le maillage de fond est défini par un ensemble de grilles cartésiennes superposées aux grilles de corps, qui sont engendrées et adaptées automatiquement selon les caractéristiques de l'écoulement. Afin de traiter des maillages recouvrants autour de géométries complexes sans surcoût humain, les différentes grilles sont regroupées par composant Chimère. Des relations d'assemblage sont alors définies entre composants, en s'inspirant de la Géométrie de Construction des Solides (CSG), où un solide peut être construit par opérations booléennes successives entre solides primitifs. Le calcul des connectivités Chimère est alors réalisé de manière simplifiée. Des simulations RANS sont effectuées autour d'un fuselage d'hélicoptère avec mât de soufflerie et autour d'une aile NACA0015 en incidence, afin de mettre en oeuvre la méthode. / Computational fluid dynamics (CFD) is widely used today in aeronautics, while the computing power has increased, enabling to perform simulations solving Reynolds-averaged Navier-Stokes equations (RANS) within an acceptable time frame from the industrial point of view. However, the configurations are more and more geometrically complex, making the mesh generation step prohibitive. Our aim is here to propose a method enabling a simplification of the mesh generation over complex geometries, taking advantage of the Chimera method and overcoming the major difficulties arising when performing overset grid connectivity. In our approach, the computational domain is partitioned into near-body regions and off-body regions. Near-body regions are meshed by curvilinear grids of short extension describing the obstacles involved in the simulation. Off-body mesh is defined by a set of adaptive Cartesian grids, overlapping near-body grids. In order to consider overset grids over complex geometries with no additional cost, grids are gathered by Chimera component, and assembly relations are defined between them, inspired by Constructive Solid Geometry, where a solid can result from boolean operations between primitive solids. The overset grid connectivity is thus simplified. RANS simulations are performed over a helicopter fuselage with a strut, and over a NACA0015 wing.

With the grasp of a smart grid in sight, discussions have shifted the focus of system security measures away from generation capacity; apart from modifying the supply side, demand may also be exploited to keep the system in balance. Specifically, Demand Response (DR) is the concept of consumer load modification as a result of price signaling, generation adequacy, or state of grid reliability. Implementation of DR mechanisms is one of the solutions being investigated to improve the efficiency of electricity markets and to maintain system-wide stability.  In a liberalized electricity sector, with a smart grid vision that is committed to market-based operation, end-users have now become the focal point of decision-making at every stage of the process in producing, delivering and consuming electricity. DR program implementation falls within the smart grid domain: a complex socio-technical energy system with a multiplicity of physical, economic, political and social interactions. This thesis thus employs both qualitative and quantitative research methods in order to address the ways in which residential end-users can become active DR flexibility providers in deregulated European electricity markets. The research focuses on economic incentives including dynamic pricing contracts, dynamic distribution price signals and the aggregation of load flexibility for participation in the various short-term electricity markets. / <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.</p><p>QC 20160225</p> / Erasmus Mundus Joint Doctorate in Sustainable Energy Technologies and Strategies (SETS)

In 2003, Winter, Watson, Gillman-Smith, Gilbert and Acton criticised the DSM-IV’s psychiatric conceptualisation of BPD, proposing a set of alternative descriptions based on Kelly’s (1955) Personal Construct Psychology (PCP) and diagnostic constructs. According to Winter et al. (2003), PCP offers not only a less “pre-emptive” stance towards BPD but is more clinically useful given its intrinsic implications for treatment. This correlational research study aimed to determine whether BPD symptomatology is associated with these proposed characteristics of construing. In addition, it was hypothesised that those with a belief that BPD was a part of their identity and untreatable would display higher levels of hopelessness. Ten participants with an existing diagnosis of BPD completed the following measures: a) Personal Construct Inventory (PCI; Chambers & O’Day, 1984); b) Millon Clinical Multiaxial Inventory, Third Edition, (MCMI-III, Millon, 1994); and c) Beck Hopelessness Scale (BHS; Beck & Steer, 1988). Participants were also asked to complete a repertory grid and a Likert Scale indicating the extent of their belief that: a) BPD is an intrinsic part of them; and b) BPD is a treatable condition. Two of the participants are presented as case examples. The most significant finding related to the hypothesis that greater BPD symptomatology would be associated with a higher degree of change in self-construction over time (‘slot-rattling’). Contrary to our prediction, similarity of construing of the elements ‘Me Now’ and ‘Me in the Past’ was correlated with greater BPD symptomatology. This may indicate a belief among participants that they are unable to change or may represent Kellian hostility. Construing one’s mother and father similarly to one’s therapist was associated with greater BPD symptomatology, as was construing one’s father and partner similarly, suggesting, as hypothesised, that those diagnosed with BPD tend to construe current relationships in the same terms as early relationships. Pre-emptive construing and poorly elaborated self-construction were also found to be associated with increased BPD symptoms as predicted. Content analyses performed on elicited constructs revealed that emotion regulation is the most salient area for participants. While the majority of participants considered that BPD was a part of their identity, most were uncertain as to whether BPD is treatable although these findings were not significantly correlated with levels of hopelessness. Participants’ feedback about their experiences of being diagnosed with BPD raises important ethical questions. Further hypotheses are generated based on the study findings and suggestions are made for a revision of the way in which psychological distress is conceptualized, with a particular emphasis on the utility of the PCP approach towards BPD. Clinical implications, limitations of the study and possibilities for further research are discussed.

published_or_final_version / abstract / Computer Science / Doctoral / Doctor of Philosophy

Secondary hypothyroidism is caused by treatment for hyperthyroidism and is a chronic condition. After adequate treatment, people can continue to experience persistent physical and depressive symptoms. There is a lack of research into the psychological factors involved in the condition, such as how people adjust to hypothyroidism. The study used Kelly’s (1955) Personal Construct Theory to explore the way in which patients construe (appraise) themselves with hypothyroidism and how this relates to coping, depression and hypothyroid symptoms. Twenty participants were recruited from an endocrinology clinic and online, through thyroid support organisations. Participants completed a semi-structured interview called a repertory grid and self-report measures of coping (Brief COPE), depression (HADS) and hypothyroid symptoms (ThySRQ). Repertory grid measures were extracted such as distances between different views of the self. The results showed that how unfavourably the self now was viewed compared to self before a thyroid disorder was positively correlated with depression, dysfunctional coping and hypothyroid symptoms. Identification with a negative view of hypothyroidism was associated with poorer mental and physical health and with dysfunctional coping. Polarized (i.e. black-and-white) construing and tight (i.e. rigid) construing were significantly and positively related to depression scores. Tightness of construing was also related to the number of hypothyroid symptoms experienced. Dysfunctional coping was positively correlated with depression and hypothyroid symptoms. Those with a history of depression experienced significantly more hypothyroid symptoms. Exploratory multiple regression analyses uncovered that how unfavourably the person viewed themselves now compared with before any thyroid problem, hypothyroid symptom frequency and dysfunctional coping accounted for 82.9% of the variance in depression. This highlights the importance of understanding how people construe the experience of hypothyroidism and their coping strategies and therefore psychological interventions may be helpful. Limitations include a small sample size and a correlational design, whereby cause and effect conclusions cannot be drawn.

This essay is a study of Agnes Martin (1912-2004), a Canadian-born and American-based contemporary artist, and her earlier painting practice including, but not limited, to her work Falling Blue of 1963. The exploration of this piece and others frames Martin’s early work as a process of material exploration analogous to weaving and fiber art. This framing is enhanced by the friendship and professional exchange between Martin and artist Lenore Tawney (1907-2007). The textile lens, as explored in this paper, has been undeveloped compared to other approaches to Martin’s early work and practice.

The outstanding features of modular multilevel converters (MMC) have recently gained much attention in the high-voltage direct-current (HVDC) transmission field. Power quality, converter cost and system performance are three crucial aspects of HVDC MMCs which are directly linked to the converter modulation and switching schemes. High power quality and performance require high switching frequency and large cell capacitor whereas low switching frequency and small cell capacitor are needed to reduce the converter cost. The main objective of this thesis is to propose a practical switching method for HVDC MMCs which balances the aforementioned contradictory requirements. A mathematical analysis of the converter switching pattern, against the power quality and converter cost, has been conducted to formulate an optimization problem for MMCs. Different objective functions are studied for the formulated optimization problem such as converter loss minimization, voltage imbalance minimization and computational burden minimization. This thesis proposes three methods to address different objective functions. Ultimately, a real-time simulator has been built to practically verify and investigate the performance of the proposed methods in a realistic point-to-point HVDC link. The most significant outcome of this thesis is the tolerance band-based switching scheme which offers a direct control of the cell capacitor voltage, low power losses, and robust dynamic performance. As a result, the converter switching frequency can reach frequencies as low as 70 Hz (with the proposed cell tolerance band (CTB) method). A modified optimized CTB method is proposed to minimize the converter switching losses and it could reduce the converter switching losses by 60% in comparison to the conventional phase shifted carrier modulation method. It is concluded intelligent utilization of sorting algorithm can enable efficient HVDC station operation by reducing the converter cost. / <p>QC 20160916</p>

O trabalho apresenta casas projetadas pelo arquiteto Eduardo de Almeida, entre 1959 e 2007, que revelam procedimentos consistentes de projeto para efeito de ensino e pesquisa em arquitetura, com ênfase no uso de retículas durante a elaboração do raciocínio do projeto. Entende-se que o uso de malhas reticuladas, ao orientar a organização espacial e construtiva, irá se refletir no resultado final da arquitetura. Porém, as retículas, enquanto procedimento, estão submetidas a uma intenção de projeto, assumindo características diferentes. Para um melhor entendimento do papel da retícula, discute-se brevemente a retícula na obra de Frank Lloyd Wright, Mies van der Rohe e Louis Kahn. / This essay presents houses made by Eduardo de Almeida between 1959 and 2007, which shows consistent project procedures for teaching and research in architecture, emphasizing the use of grids. It is considered that grids, by guiding the space and constructive organization, are reflected in the final results of architecture. Nevertheless, grids as a project procedure is submitted by a project intention, therefore different kinds of grids can be noticed while analyzing different architects. For a better understanding of grids, architects such as Frank Lloyd Wright, Mies van der Rohe and Louis Kahn are also briefly discussed.

O presente trabalho visa propor metodologia inovadora e abrangente que permita a avaliação sistêmica das diversas funcionalidades envolvidas no conceito de Redes Elétricas Inteligentes Smart Grids - (REI). Tal metodologia possibilita a avaliação de políticas de implementação destas funcionalidades de acordo com as características atuais das empresas, tendo como balizador central o benefício social fundamentado na visão dicotômica entre Concessionária e Consumidor. A metodologia proposta parte de modelagem inovadora de representação da rede e das funcionalidades emergentes de REIs, culminando em modelo de otimização que visa propor roadmaps tecnológicos fundamentados em avaliações de custos e benefícios de implantação. A importância das contribuições contidas na presente tese reside no fato de que o conceito de REI vem ganhando destaque nos cenários nacional e internacional, sendo apontado por especialistas do mundo todo como uma possível quebra de paradigma no setor elétrico. O referido conceito traz consigo uma série de funcionalidades e novas formas de integração e relacionamento entre os diversos agentes do setor. Tais funcionalidades necessitam de conceituação clara e objetiva, assim como metodologias de análise dos benefícios e dos custos decorrentes de sua aplicação nos respectivos segmentos do sistema de distribuição. Funcionalidades de REIs impactam tanto os processos de gestão do sistema de distribuição como os procedimentos de planejamento, operação e engenharia, além de permitirem ao consumidor, com possível papel adicional de produtor, maior gerência sobre seu consumo de energia. Diante de um cenário com diversos agentes, com alternância de papéis e com intensa interação entre si, somado às funcionalidades sistêmicas e de rede propiciadas pelos avanços tecnológicos crescentes, é fundamental uma análise global que estabeleça políticas ótimas de implantação das funcionalidades de REI, buscando a maximização do benefício social associado. Destarte, o produto principal desta tese, qual seja o modelo de proposição de plano ótimo de implantação de funcionalidades de REI, considerando os custos de implantação e os benefícios associados, não só ao setor elétrico, mas à sociedade como um todo, consiste em ferramenta valiosa para o planejamento de empresas concessionárias de distribuição na definição de roadmaps tecnológicos. Além disso, tal ferramenta permitirá a realização de estudos nacionais que fundamentem o balizamento de políticas públicas para o tema. / This thesis proposes an innovative and comprehensive methodology that allows the systematic evaluation of various functionalities involved in the concept of Smart Grids. Such methodology enables the proposition and evaluation of different policies for the implementation of smart grid functionalities according to the current characteristics of the utilities. Furthermore, the methodology is basically centered on the social benefits that consider a dichotomy view regarding Utility and Customer. This methodology considers an innovative model for network representation and Smart Grid emerging functionalities. Based on that, it leads to an optimization model that produces technologic roadmaps that take into account the evaluation of costs and benefits for the policies implementation. The importance of the contributions in this thesis lay in the fact that the concept of smart grids has been gaining attention in the national and international scenes, being pointed out by experts around the world as a possible paradigm break for the electricity sector. This concept brings a number of functionalities and new forms of integration and relationships amongst the various agents. These functionalities require clear and objective concepts, as well as methods for cost-benefit analysis regarding their implementation on the various segments of the distribution system. Smart grid functionalities impact most of the management processes in a distribution company as well as planning, operation and engineering procedures. Besides that customers are enabled to better manage their energy consumption, especially when playing the role of producers as well. Facing a scenario with several agents playing different roles with intense interaction, as well as systemic functionalities propitiated by advances in technology, one should devise a global analysis in order to establish optimal policies to implement Smart Grid functionalities, pursuing maximization of associated social benefits. In such a context, the main product of this thesis is an innovative model that produces optimal cost effective plans regarding the deployment of Smart Grid functionalities. Such a product is to be applied not only in the electricity sector but in society as a whole, consisting in a valuable planning tool for distribution utilities to define technological roadmaps as well as countrywide studies for the proposition of new public policies for smart grid implementation.