Over the past ten years, there has been increased use of electronic power processing in alternative, sustainable, and distributed energy sources, as well as energy storage systems, transportation systems, and the power grid. Three-phase voltage source converters (VSCs) have become the converter of choice in many ac medium- and high-power applications due to their many advantages, such as high efficiency and fast response. For transportation applications, high power density is the key design target, since increasing power density can reduce fuel consumption and increase the total system efficiency. While power electronics devices have greatly improved the efficiency, overall performance and power density of power converters, using power electronic devices also introduces EMI issues to the system, which means filters are inevitable in those systems, and they make up a significant portion of the total system size and cost. Thus, designing for high power density for both power converters and passive components, especially filters, becomes the key issue for three-phase converters. This dissertation explores two different approaches to reducing the EMI filter size. One approach focuses on the EMI filters itself, including using advanced EMI filter structures to improve filter performance and modifying the EMI filter design method to avoid overdesign. The second approach focuses on reducing the EMI noise generated from the converter using a three-level and/or interleaving topology and changing the modulation and control methods to reduce the noise source and reduce the weight and size of the filters. This dissertation is divided into five chapters. Chapter 1 describes the motivations and objectives of this research. After an examination of the surveyed results from the literature, the challenges in this research area are addressed. Chapter 2 studies system-level EMI modeling and EMI filter design methods for voltage source converters. Filter-design-oriented EMI modeling methods are proposed to predict the EMI noise analytically. Based on these models, filter design procedures are improved to avoid overdesign using in-circuit attenuation (ICA) of the filters. The noise propagation path impedance is taken into consideration as part of a detailed discussion of the interaction between EMI filters, and the key design constraints of inductor implementation are presented. Based on the modeling, design and implementation methods, the impact of the switching frequency on EMI filter weight design is also examined. A two-level dc-fed motor drive system is used as an example, but the modeling and design methods can also be applied to other power converter systems. Chapter 3 presents the impact of the interleaving technique on reducing the system passive weight. Taking into consideration the system propagation path impedance, small-angle interleaving is studied, and an analytical calculation method is proposed to minimize the inductor value for interleaved systems. The design and integration of interphase inductors are also analyzed, and the analysis and design methods are verified on a 2 kW interleaved two-level (2L) motor drive system. Chapter 4 studies noise reduction techniques in multi-level converters. Nearest three space vector (NTSV) modulation, common-mode reduction (CMR) modulation, and common-mode elimination (CME) modulation are studied and compared in terms of EMI performance, neutral point voltage balancing, and semiconductor losses. In order to reduce the impact of dead time on CME modulation, the two solutions of improving CME modulation and compensating dead time are proposed. To verify the validity of the proposed methods for high-power applications, a 100 kW dc-fed motor drive system with EMI filters for both the AC and DC sides is designed, implemented and tested. This topology gains benefits from both interleaving and multilevel topologies, which can reduce the noise and filter size significantly. The trade-offs of system passive component design are discussed, and a detailed implementation method and real system full-power test results are presented to verify the validity of this study in higher-power converter systems. Finally, Chapter 5 summarizes the contributions of this dissertation and discusses some potential improvements for future work. / Ph. D.

AC and DC impedances of switching power converters are used for the stability analysis of modern power electronics systems at three-phase AC and single-phase DC interfaces. Therefore, a small-signal characterization algorithm for switching power converter, which is based on FFT, will be presented and explained. The presented extraction algorithm is general and can be used to obtain other small-signal transfer functions of arbitrary power converter switching simulation models. Furthermore, FFT algorithm is improved by using cross power spectral density functions for identification, resulting in an algorithm, which is more noise immune. Both small-signal identification algorithms are validated in simulations, and CPSD algorithm is used in experimental measurement procedure. Several wide bandwidth injection signals, among which are chirp, multi-tone, pulse and white noise, are compared and theoretically analyzed. Several hardware examples are included in the analysis. The second part of the dissertation will focus on the modeling of small-signal input dq admittance of multi-pulse diode rectifiers, providing comparison between well-known averaged value models (AVMs), parametric averaged value models (PAVM), the switching simulation model and hardware measurements. Analytical expressions for all four admittances present in the dq matrix are derived and analyzed in depth, revealing the accuracy range of the averaged models. Furthermore, a hardware set-up is built, measured and modeled, showing that the switching simulation model captures nonlinear sideband effects accurately. In the end, a multi-pulse diode rectifier feeding a constant power load is analyzed with modified AVM and through detailed simulations of switching model, proving effectiveness of the proposed modifications. The third part describes implementation and design of a single-phase multi-level single-phase shunt current injection converter based on cascaded H-bridge topology. Special attention is given toward the selection of inductors and capacitors, trying to optimize the selected component values and fully utilize operating range of the converter. The proposed control is extensively treated, including inner current, outer voltage loop and voltage balancing loops. The designed converter is constructed and integrated with measurement system, providing experimental verification. The proposed multi-level single-phase converter is a natural solution for single-phase shunt current injection with the following properties: modular design, capacitor energy distribution, reactive element minimization, higher equivalent switching frequency, capability to inject higher frequency signals, suitable to perturb higher voltage power systems and capable of generating cleaner injection signals. Finally, a modular interleaved single-phase series voltage injection converter, consisting of multiple paralleled H-bridges is designed and presented. The decoupling control is proposed to regulate ac injection voltage, providing robust and reliable strategy for series voltage injection. The designed converter is simulated using detailed switching simulation model and excellent agreement between theory and simulation results are obtained. The presented control analysis treats different loads, examining robustness of the circuit to load variations. Simulation model and hardware prototype results verify the effectiveness of the proposed wide-bandwidth identification of small-signal dq impedances via single-phase injections. / Ph. D.

Reliability analysis plays an important role in keeping manufacturers in a competitive position. It can be applied in many areas such as warranty predictions, maintenance scheduling, spare parts provisioning, and risk assessment. This dissertation focuses on statistical modeling and predictions based on lifetime data, degradation data, and recurrent event data. The datasets used in this dissertation come from the field, and have complicated structures. The dissertation consists of three main chapters, in addition to Chapter 1 which is the introduction chapter, and Chapter 5 which is the general conclusion chapter. Chapter 2 consists of the traditional time-to-failure data analysis. We propose a statistical method to address the failure data from an appliance used at home with the consideration of retirement times and delayed reporting time. We also develop a prediction method based on the proposed model. Using the information of retirement-time distribution and delayed reporting time, the predictions are more accurate and useful in the decision making. In Chapter 3, we introduce a nonlinear mixed-effects general path model to incorporate dynamic covariates into degradation data analysis. Dynamic covariates include time-varying environmental variables and usage condition. The shapes of the effect functions of covariates may be constrained to be, for example, monotonically increasing (i.e., higher temperature is likely to cause more damage). Incorporating dynamic covariates with shape restrictions is challenging. A modified alternative algorithm and the corresponding prediction method are proposed. In Chapter 4, we introduce a multi-level trend-renewal process (MTRP) model to describe component-level events in multi-level repairable systems. In particular, we consider two-level repairable systems in which events can occur at the subsystem level, or the component (within the subsystem) level. The main goal is to develop a method for estimation of model parameters and a procedure for prediction of the future replacement events at component level with the consideration of the effects from the subsystem replacement events. To explain unit-to-unit variability, time-dependent covariates as well as random effects are introduced into the heterogeneous MTRP model (HMTRP). A Metropolis-within-Gibbs algorithm is used to estimate the unknown parameters in the HMTRP model. The proposed method is illustrated by a simulated dataset. / Ph. D.

The wide application of the genomic microarray technology triggers a tremendous need in the development of the high dimensional genetic data analysis. Many statistical methods for the microarray data analysis consider one gene at a time, but they may miss subtle changes at the single gene level. This limitation may be overcome by considering a set of genes simultaneously where the gene sets are derived from the prior biological knowledge and are called "pathways". We have made contributions on two specific research topics related to the high dimensional genetic pathway data. One is to propose a semi- parametric model for identifying pathways related to the zero inflated clinical outcomes; the other is to propose a multilevel Gaussian graphical model for exploring both pathway and gene level network structures. For the first problem, we develop a semiparametric model via a Bayesian hierarchical framework. We model the pathway effect nonparametrically into a zero inflated Poisson hierarchical regression model with unknown link function. The nonparametric pathway effect is estimated via the kernel machine and the unknown link function is estimated by transforming a mixture of beta cumulative density functions. Our approach provides flexible semiparametric settings to describe the complicated association between gene microarray expressions and the clinical outcomes. The Metropolis-within-Gibbs sampling algorithm and Bayes factor are used to make the statistical inferences. Our simulation results support that the semiparametric approach is more accurate and flexible than the zero inflated Poisson regression with the canonical link function, this is especially true when the number of genes is large. The usefulness of our approaches is demonstrated through its applications to a canine gene expression data set (Enerson et al., 2006). Our approaches can also be applied to other settings where a large number of highly correlated predictors are present. Unlike the first problem, the second one is to take into account that pathways are not independent of each other because of shared genes and interactions among pathways. Multi-pathway analysis has been a challenging problem because of the complex dependence structure among pathways. By considering the dependency among pathways as well as genes within each pathway, we propose a multi-level Gaussian graphical model (MGGM): one level is for pathway network and the second one is for gene network. We develop a multilevel L1 penalized likelihood approach to achieve the sparseness on both levels. We also provide an iterative weighted graphical LASSO algorithm (Guo et al., 2011) for MGGM. Some asymptotic properties of the estimator are also illustrated. Our simulation results support the advantages of our approach; our method estimates the network more accurate on the pathway level, and sparser on the gene level. We also demonstrate usefulness of our approach using the canine genes-pathways data set. / Ph. D.

[pt] Esta dissertação explora os processos de decisão que envolvem a transição para combustíveis de baixo carbono no setor marítimo, uma indústria vital para o comércio global, mas também uma significativa fonte de emissões de gases de efeito estufa. A investigação é guiada pela Teoria Institucional e pela Perspectiva Multinível (MLP) sobre transições para a sustentabilidade, oferecendo uma análise abrangente de como pressões institucionais e a necessidade de sustentabilidade influenciam as práticas organizacionais e as decisões estratégicas na adoção de novas tecnologias energéticas. Este estudo destaca-se por aplicar e ampliar teorias estabelecidas no contexto específico das transições de combustíveis no setor marítimo, contribuindo tanto para a teoria quanto para a prática ao fornecer um modelo de tomada de decisão aprimorado para o uso de combustíveis alternativos. O estudo adota uma abordagem de métodos mistos, integrando uma revisão sistemática de literatura e uma pesquisa detalhada com stakeholders da indústria marítima. A revisão de literatura foca na identificação de lacunas existentes e na compreensão das dinâmicas institucionais e de mercado que impactam a adoção de tecnologias de baixo carbono. A pesquisa, por outro lado, coleta dados primários sobre as percepções, barreiras e facilitadores percebidos por profissionais do setor, utilizando tanto análises quantitativas quanto qualitativas para uma compreensão mais profunda das atitudes em relação à transição energética. Os resultados revelam que inovações tecnológicas e incentivos econômicos emergem como facilitadores críticos, enquanto barreiras significativas incluem custos iniciais elevados, limitações de infraestrutura e desafios regulatórios complexos. Mais importante ainda, o estudo identifica e discute o papel das pressões institucionais - coercitivas, normativas e miméticas - e como elas moldam comportamentos organizacionais em direção a práticas sustentáveis. A dissertação propõe um framework de tomada de decisão que integra essas pressões com considerações práticas, ajudando as empresas a alinhar suas estratégias operacionais com objetivos de sustentabilidade ambiental. O trabalho expande a aplicação da Teoria Institucional e MLP ao examinar como essas teorias podem ser inter-relacionadas e aplicadas para explicar a complexidade das transições para combustíveis mais limpos na indústria marítima. A pesquisa oferece às empresas marítimas um modelo estratégico para orientar a transição para combustíveis alternativos, enfatizando a importância de um ambiente regulatório de suporte, cooperação internacional e colaboração entre stakeholders para facilitar essa mudança. O estudo conclui que a transição para combustíveis alternativos no setor marítimo é profundamente influenciada por uma complexa interação de fatores tecnológicos, econômicos e institucionais. O framework de tomada de decisão proposto ajuda as empresas marítimas a compreender essas dinâmicas existentes e também tráz à tona o papel crucial da inovação tecnológica, avaliações de impacto abrangentes e o desenvolvimento de políticas e frameworks regulatórios eficazes. Por fim, a dissertação sugere uma agenda de pesquisa futura focada na análise de transições tecnológicas específicas e na evolução dos comportamentos institucionais em resposta a desafios ambientais globais. / [en] This dissertation, titled The Adoption of Alternative Fuels in the Maritime Sector, critically examines the decision-making processes in the maritime industry under the lens of Institutional Theory and the Multi-Level Perspective (MLP) on sustainability transitions. Employing a mixed-method approach, which integrates a comprehensive literature review with a detailed survey, the study explores how institutional pressures and sustainability transitions influence the shift toward low-carbon fuels in maritime operations. The research identifies key enablers such as technological innovations and economic incentives, and addresses barriers including high initial costs, infrastructural limitations, and regulatory challenges. It also highlights the significant influence of coercive, normative, and mimetic pressures in shaping organizational behaviours towards sustainable practices. A novel decision-making framework that synthesizes insights from Institutional Theory and MLP is proposed to facilitate the adoption of alternative fuels, supporting maritime companies in navigating the complexities of sustainability transitions. A research agenda is also put forward. The practical relevance of this study lies in its strategic framework, which provides actionable insights for maritime companies pursuing environmental sustainability. Academically, the dissertation makes a significant theoretical contribution by applying and extending Institutional Theory and MLP within the context of maritime fuel transitions, enhancing our understanding of the interplay between institutional dynamics and sustainability practices in the maritime industry.

Today’s urban planners and scholars emphasize the necessity of a shift towards sustainable modes of transport. Among these, bicycle highways have emerged as an innovative infrastructure solution. Characterized by their broader lanes and separation from other transport modes, they offer a safer and more efficient alternative to traditional bike lanes. However, the implementation of bicycle highways presents challenges as they cross several municipal borders and involve multiple stakeholders across various governmental levels. This thesis explores the advantages and challenges of implementing bicycle highways in Skåne. By interviewing eight officials working with bicycle highway planning at various governmental levels, the thesis aims to explore and analyze the gaps in translating frameworks, such as multi-level governance, into practice. It also investigates the differences in frameworks, values, and attitudes to explore how these variations affect the conditions and efforts for collaboration across various governmental scales. The thesis discovers multiple advantages perceived by officials within the field in terms of a higher-quality design of the bicycle infrastructure, while also discovering the challenges of implementing such infrastructure. It also recognizes that collaboration within various governmental scales is needed to develop seamless bicycle highways. Different approaches among road actors related to prioritized values, allocation of budgets, political ideals, and timeframes are identified, and could affect the effectiveness of collaboration across scales. However, attitudes continue to be a crucial factor in the success of bicycle highways between urban areas.

Die Psychologie der Lebensspanne und die Soziologie des Lebensverlaufs betonen die Bedeutung von Kontexten für den Erwerb individueller Fähigkeiten und die Entwicklung im Leben. In Übereinstimmung mit diesen konzeptionellen Annahmen zeigen Studien, dass verschiedene Kontexte die Entwicklung individueller Bereiche beeinflussen. Jedoch ist wenig darüber bekannt, wie kontextuelle Faktoren in der zweiten Lebenshälfte Wohlbefinden formen und wie Wohlbefinden in diesen Lebensphasen von sich schnell verändernden Kontexten beeinflusst wird. In dieser Dissertation werden unter Anwendung des Ökosystemischen Ansatzes von Bronfenbrenner drei Kontexte unterschiedlicher Proximität untersucht, in die die Entwicklung des individuellen Wohlbefindens eingebettet ist. Als erster Kontext wird die vielfältige Ökologie des Lebens und Sterbens in den ehemaligen Regionen Ost- und Westdeutschland herangezogen, um herauszufinden wie dieses Makrosystem Wohlbefinden in den letzten Lebensjahren gestaltet. Als zweiter Kontext wird die Bedeutung des Exosystems von Gesundheitseinrichtungen in Landkreisen (z.B. Anzahl stationärer Pflegereinrichtungen) auf Wohlbefindensverläufe am Lebensende beleuchtet. Als dritten Kontext untersuchen wir, wie das Mikrosystem sozialer Ökologien und Situationen momentanes, affektives Wohlbefinden gestaltet, sowie Altersunterschiede in diesen Assoziationen. Gemeinsam zeigen die drei Studien dieser Dissertation, dass Ökologien auf regionaler, dienstleistender und sozialer Kontextebene Entwicklung von Wohlbefinden in der zweiten Lebenshälfte beeinflussen. Diese Arbeit zeigt, dass Kontexte sowohl kognitives als auch affektives Wohlbefinden und innerhalb des letzteren sowohl Valenz und Aktivierung beeinflussen, und untersucht länger- und kurzfristige Kontext-Wohlbefindens-Assoziationen in späteren Lebensphasen. Die Ergebnisse liefern erste Vorschläge für Interventionen und veränderbare regionale Faktoren für die Erhaltung oder Verbesserung von Wohlbefinden. / Lifespan psychology and life course sociology have long acknowledged the role of context for individual functioning and development throughout life. Consistent with these conceptual notions, empirical studies show that various contextual factors influence development of individual-level outcomes. However, we know little about how contextual factors shape individual-level well-being and how well-being is influenced by fast changing contexts in the second half of life. Applying Bronfenbrenner’s model of human ecology as the overarching theoretical frame, this dissertation examines three sets of contexts that differ in the degree of proximity in which individual well-being and its development is embedded in. As a first context, the multifaceted ecology of living and dying in former regions of East and West Germany is used to investigate how the macrosystem shapes individual well-being in the last years of life. For a second context, the role of the exosystem of county-level health care features (e.g., number of inpatient care facilities) on late-life trajectories in well-being is examined. As a third context, we examine how the microsystem of social ecologies and situations influences momentary affective well-being and how these associations differ across age. Jointly, the three studies in this dissertation show that regional, service, and social ecologies profoundly shape development in well-being during the second half of life. To conclude, this dissertation shows that these contexts influence both cognitive and affective components of well-being, among the affective domain two facets (valence and arousal), and investigates long-term and short-term contextwell- being associations in later life phases. Results provide initial suggestions for interventions and malleable regional factors to maintain or improve well-being.

Multilevel inverter technology has emerged recently as a very important alternative in the area of high-power medium-voltage energy control. Voltage operation above semiconductor device limits, lower common mode voltages, near sinusoidal outputs together with small dv/dt’s, are some of the characteristics that have made this power converters popular for industry and modern research. However, the existing solutions suffer from some inherent drawbacks like common mode voltage problem, DC-link capacitor voltage fluctuation etc. Cascaded multi-level inverter with open-end winding induction motor structure promises significant improvements for high power medium-voltage applications. This dissertation investigates such cascaded multi-level inverters for open-end winding induction motor drive with reduced switch count. Similar to the conventional two-level inverters, other multi-level inverters with PWM control generate alternating common mode voltage (CMV). The alternating common mode voltage coupled through the parasitic capacitors in the machine and results in excessive bearing current and shaft voltage. The unwanted shaft voltage may cross the limit of insulation breakdown voltage and cause motor failure. This alternating common mode voltage adds to the total leakage current through ground conductor and acts as a source of conducted EMI which can interfere with other electronic equipments around. As the number of level increase in the inverter, different voltage levels are made available by using DC-link capacitor banks, instead of using different isolated power supplies. The intermediate-circuit capacitor voltages which are not directly supplied by the power sources are inherently unstable and require a suitable control method for converter operation, preferably without influence on the load power factor. Apart from normal operation, the sudden fault conditions may occur in the system and it is necessary to implement the control strategy considering this condition also. A five-level inverter topology with cascaded power circuit structure is proposed in this dissertation with the strategy to eliminate the common mode voltage and also to maintain the balance in the DC-link capacitor voltages. The proposed scheme is based on a dual five-level inverter for open-end winding induction motor. The principle achievement of this work is the reduction of power circuit complexity in the five-level inverter compared to a previously proposed five-level inverter structure for open-end winding IM drive with common mode voltage elimination. The reduction in the number of power switching devices is achieved by sharing the two two-level inverters for both the inverter structures. The resultant inverter structure can produce a nine-level voltage vector structure with the presence of alternating common mode voltage. The inverter structure is formed by cascading conventional two-level inverters together with NPC three-level inverters. Thus it offers modular and simpler power bus structure. As the power circuit is realised by cascading conventional two-level and NPC three-level inverters the number of power diodes requirements also reduced compared to the conventional NPC five-level inverters. The present proposed structure is implemented for the open-end winding induction motor and the power circuit offers more number of switching state redundancies compared to any conventional five-level inverter. The inverter structure required half the DC-link voltage compared to the DC-link voltage required for the conventional five-level inverter structure for induction motor drive and this reduces the voltage stress on the individual power devices. The common mode voltage is eliminated by selecting only the switching states which do not generate any common mode voltage in pole voltages hence there will be no common mode voltage at the motor phase also. The technique of using the switching state selection for the common mode voltage elimination, cancels out the requirement of the filter for the same purpose. As the inverter output is achieved without the presence of common mode voltage, the dual inverter can be fed from the common DC-link sources, without generating any zero sequence current. Hence the proposed dual five-level inverter structure requires only four isolated DC supplies. The multi-level inverters supplied by single power supply, have inherent unbalance in the DC-link capacitor voltages. This unbalance in the DC-link capacitor voltages causes lower order harmonics at the inverter output, resulting in torque pulsation and increased voltage stress on the power switching devices. A five-level inverter with reduced power circuit complexity is proposed to achieve the dual task of eliminating common mode voltage and DC-link capacitor voltage balancing. The method includes the analysis of current through the DC-link capacitors, depending on the switching state selections. The conditions to maintain all the four DC-link capacitor voltages are analysed. In an ideal condition when there is no fault in the power circuit the balance in the capacitor voltages can be maintained by selecting switching states in consecutive intervals, which have opposite effect on the capacitor voltages. This is called the open loop control of DC-link capacitor voltage balancing, since the capacitor voltages are not sensed during the selection of the switching states. The switching states with zero common mode voltages are selected for the purpose of keeping the capacitor voltages in balanced condition during no fault condition. The use of any extra hardware is avoided. The proposed open loop control of DC-link capacitor voltage balancing is capable of keeping the DC-link capacitor voltages equal in the entire modulation region irrespective of the load powerfactor. The problem with the proposed open loop control strategy is that, it can not take any corrective action if there is any initial unbalance in the capacitor voltages or if any unbalance occurs in the capacitor voltages during operation of the circuit,. To get the corrective action in the capacitor voltages due occurrence of any fault in the circuit, the strategy is further improved and a closed loop control strategy for the DC-link capacitor voltages is established. All the possible fault conditions in the four capacitors are identified and the available switching states are effectively used for the corrective action in each fault condition. The strategy is implemented such a way that the voltage balancing can be achieved without affecting the output fundamental voltage. The proposed five-level inverter structure presented in this thesis is based on a previous work, where a five-level inverter structure is proposed for the open-end winding induction motor. In that previous work 48 switches are used for the realization of the power circuit. It is observed that all the available switching states in this previous work are not used for any of the performance requirement of CMV elimination or DC-link voltage balancing. So, in this proposed work, the power circuit is optimized by reducing some of the switches, keeping the performance of the inverter same as the power circuit proposed in the previous work. The five-level inverter proposed in this thesis used 36 switches and the number of switching states is also reduced. But, the available switching states are sufficient for the CMV elimination and DC-link capacitor voltage balancing. The advantage of the modular circuit structure of this proposed five-level inverter is further investigated and the inverter structure is modified to a seven-level inverter structure for the open end winding induction motor. The proposed power circuit of the seven-level inverter uses only 48 switches, which is less compared to any seven-level inverter structure for the open end winding induction motor with common mode voltage elimination. The power circuit is reduced by sharing four two-level inverters to both the individual seven-level inverters in both the sides of the of the open end winding induction motor. The cascaded structure eliminates the necessity of the power diodes as required by the conventional NPC multilevel inverters. The proposed seven-level inverter is capable of producing a thirteen-level voltage vector hexagonal structure with the presence of common mode voltage. The common mode voltage elimination is achieved by selecting only the switching states with zero common mode voltage from both the inverters and the combined inverter structure produce a seven-level voltage vector structure with zero common mode voltage. The switching frequency is also reduced for the seven-level inverter compared to the proposed five-level inverter. The advantage of this kind of power circuit structure is that the number of power diode requirement is same in both five-level and seven-level inverters. Since there is no common mode voltage in the output voltages, the dual seven-level inverter structure can be implemented with the common DC-link voltage sources for both the sides. Six isolated power supplies are sufficient for both the seven-level inverters. The available switching states in this proposed seven-level inverter are further analysed to implement the open loop and closed loop capacitor voltage balancing and this allow the power circuit to run with only three isolated DC supplies. All the proposed work presented in this thesis are initially simulated in SIMULINK toolbox and then implemented in a form of laboratory prototype. A 2.5KW open end winding induction motor is used for the implementation of these proposed works. But all these work general in nature and can be implemented for high power drive applications with proper device ratings.

There is currently an ongoing transition into more sustainable aviation. One of the sustainable alternatives to the conventional fossil-fueled aircraft is electric aviation. The research aim of the study could be divided into two parts. The first part was to identify the barriers to the development of electric aviation in Sweden. The second part was to ascertain if and, in that case, how the process to reach dominant design can be affected by the actors. Empirical data was mainly gathered through semi-structured interviews. In order to address the research aim, a theoretical framework built upon theories from both multi-level perspective and dominant design theory was used. There were barriers arising from Financial, Regulatory & Political, Business Model & Legitimacy, and Technical conditions. The theoretical analysis implied the existence of two socio-technical gates. These gates consist of collaboration and legitimacy aspects. Metaphorically passing through these gates would make overcoming the relevant barriers much easier. This would also align all elements of the transition, which makes it possible for the actors to affect the process of achieving dominant design. / Det pågår en övergång till mer hållbart flyg. Ett exempel på dessa hållbara flyg är elektriska flygplan. Målet med studien kan delas upp i två delar. Den första delen är att identifiera barriärerna som hindrar utvecklingen av dessa elektriska flygplan. Den andra delen är att ta reda på om och i så fall hur processen för att nå en dominant design på marknaden kan påverkas av aktörerna. Insamlingen av data gjordes huvudsakligen med hjälp av semistrukturerade intervjuer. Teorier från “multi-levelperspective” och dominant design-teori har använts. Resultaten visar på att det finns möjliga barriärer för utvecklingen inom områden av ekonomi, regelverk, affärsmodeller och legitimitet samt teknik. Analysen implicerar existensen av två “socio-tekniska portar”. Dessa består av legitimitet och samarbete mellan aktörer. Genom att bildligt passera genom dessa portar blir det mycket enklare att överbrygga alla relaterade barriärer. Detta riktar också alla element i övergången mot sammahåll. Det i sin tur möjliggör att aktörerna kan påverka processen för att nå den dominanta designen.

This thesis studies why car-initiatives are implemented and how political visions is intertwined in this process. These topics are further explored by looking at how certain critical groups are impacted by car-free initiatives and how they can affect polarization. We use a holistic multiple case comparing Oslo’s Car-free Livability Programme with Living Stockholm. This analysis is structured with our adapted version of the multi-level perspective framework, which emphasizes social components to a greater extent than the original framework. The results show that climate concerns, a common reason to implement car-free initiatives is superseded by softer values such as an increased appreciation of urban areas. Prohibiting cars from city centers has limited short term climate effects. Instead, the value of car-free initiatives is achieved when the urban environment is improved. Additionally, an important and often overlooked result is that car-free initiatives may help change the publics’ perception of the necessity of cars. Furthermore, the political vision behind the project is interlinked with how car-free initiatives are recognized in the public. A strong political vision backed by heavy rhetoric increases the societal impact of the project, as exemplified by Oslo. The project can potentially alter the general perception of the necessity of the car long-term with such an approach but is also exposed to the public’s glare. However, if the project only focuses on a specific area of the city, it may contribute towards polarization and a feeling of discontent within society. In comparison, by implementing an agile approach without a clear political vision as Stockholm did, the project becomes more flexible and reduces unintended consequences. but also has less influence on a national or international level. Furthermore, failing to cater for the needs of critical groups, such as people with disabilities and craftsmen, often results in difficulties and may become a major source of concern within the project. However, these issues can often be identified with improved communication and reduced with small means. To conclude, the emergence of car-free initiatives is a budding trend not only in Scandinavian cities, but around the world. Fueled by concerns about the climate and an urge for citizens to reclaim urban space, car-free initiatives will become more common. Therefore, to implement successful car-free initiatives, it is vital for institutional actors to keep in mind the key points proposed in this thesis, in order to create successful, vibrant cities in the future. / Den här uppsatsen studerar varför bilfria initiativ implementeras och hur den politiska visionen påverkar utformningen. Vi analyserar även hur vissa grupper kan beröras negativt av bilfria initiativ och hur det kan påverka polariseringen i en stad. Uppsatsen använder sig av en holistisk multipel case studie, och jämför de båda huvudstadsinitiativen Bilfritt Byliv i Oslo och Levande Stockholm. Analysen är strukturerad med hjälp av vår anpassade version av multi-level perspective ramverket, som lägger större vikt vid sociala aspekter än ursprungsmodellen. Resultaten visar att klimatförbättringar, en vanlig anledning till att implementera bilfria initiativ, inte är den främsta samhällsnyttan. Andra aspekter som ofta förbises, exempelvis en ökad uppskattning av urbana miljöer, tycks vara viktigare. Att förbjuda bilar har begränsad direkt klimatnytta, utan det är vad stadsytan används till i stället som skapar olika mervärden. En ökad insikt om detta skulle sannolikt kunna göra initiativ för att minska privat bilismen mer ändamålsenliga. Vidare kan bilfria initiativ påverka allmänhetens uppfattning om bilens nödvändighet, vilket är en fråga som inte fångas upp av existerande litteratur. Bilfria initiativs utformning, och allmänhetens uppfattning av det påverkas till stor del av projektets politiska vision. En tydlig vision och kommunikation kan skapa en bred allmän medvetenhet om projektet, som i Oslos fall. Initiativetkan på så sätt skapa en betydande förändring i samhället, men exponeras därigenom även för kritik. Om projektet enbart omfattar särskilda stadsområden finns det en risk för att projektet ökar polariseringen och upplevelsen av utanförskap i staden. Om man i stället använder en mer agil approach utan en tydlig politisk vision, likt Stockholm, blir projektet mer flexibelt och minskar risken för negativa konsekvenser. Men man går därmed till stor del miste om möjligheten att påverka attityder på nationell, eller internationell nivå. Att inte ta hänsyn till grupper med särskilda behov, som äldre eller personer med funktionsnedsättning, resulterar i svårigheter såväl för dessa gruppersom för projektet. Med en intressent analys i förväg och en tydlig kommunikation kan många problem åtgärdas med små medel. Sammanfattningsvis har vi funnit att bilfria initiativ är en trend som växer sig allt starkare runt om i världen, pådriven av en ökad klimatmedvetenhet och en vilja bland stadens invånare att återta urbana miljöer från bilar. Med studien presenterar vi viktiga aspekter för att möjliggöra en effektiv implementering av bilfria initiativ och skapa framtidens levande städer.