L’intégration massive de la production d’énergie éolienne intermittente au niveau des réseaux électriques pose un problème de stabilité du système électrique. En effet les caractéristiques sont très différentes de celles de sources conventionnelles maîtrisées par les gestionnaires de réseau. Par conséquent, l’injection de cette énergie induit de nouveaux challenges pour les gestionnaires de réseaux électriques. De plus, les conditions de raccordement évoluent et tendent à ce que toutes les sources participent aux services rendus aux systèmes électriques. Les travaux de cette thèse sont focalisés sur la proposition d’une nouvelle stratégie de commande non-linéaire basée sur la commande par « platitude à une boucle » d’un système de conversion d’énergie éolienne. Cette stratégie de contrôle vise la gestion des interactions au point de connexion par la génération et le suivi de trajectoires de références. De par le fait que toutes les variables du système sont liées à la « sortie plate » de ce système, cette commande procure une rapidité de réponse et une bonne maitrise des régimes transitoires. La mise en œuvre de cette nouvelle stratégie de contrôle pour la constitution d’un parc éolien offshore, capable de satisfaire différentes conditions de raccordement a été simulée avec succès. Plus particulièrement, l’évaluation de l’impact de différents défauts du réseau sur les services proposés (Régulation de fréquence et de tension, la tenue aux creux de tension.) a été réalisée. / The massive integration of intermittent production of wind energy in electrical networks creates an electrical system stability problem. Indeed, its characteristics are very different from those of conventional sources controlled by Grid managers. Therefore, the injection of this energy makes new challenges for power Grid operators. Moreover, the connection conditions are evolving and go towards the situations that all different sources participate into services of electrical systems. This thesis proposes a new nonlinear control strategy based on a « one loop flatness control » of a wind energy conversion system. This control strategy has aim of energy interactions management at the connection point through generation and tracking of reference trajectories. As all system variables are functions of the « flat output » of the system, this control provides fast response and good control in transient state. The application of this new control strategy into an offshore wind farm which is able to satisfy different connection conditions was simulated successfully. Specifically, effects of various grid faults on the proposed ancillary services (frequency and voltage regulation, and low-voltage ride through capabilities) were performed.

Le gouvernement français s'est engagé sur un ambitieux objectif de développer l'éolien offshore pour atteindre une capacité de 6 GW d'ici 2020. La construction d'éoliennes terrestres, tout comme les éoliennes offshore, est très contestée en raison de leur impact visuel sur le paysage. Dans la région française du Languedoc Roussillon, les acteurs concernés (industrie touristique, commerces, pêcheurs, élus locaux), craignent que la construction de parc éoliens offshore aie des effets néfastes sur le tourisme, en donnant à la région une image industrialisée et « bétonnée ». Jusqu'à présent, en mer du Nord, il n'a jamais été mis en évidence que la construction de parcs éoliens offshore ait réellement affecté l'attractivité touristique des côtes environnantes. On peut se demander si ce constat peut être extrapolé à la cote méditerranéenne. Depuis une dizaine d'années, lorsqu'ont débuté les débats sur la possibilité d'exploiter les vents méditerranéens, beaucoup de préjugés sont apparus sur l'impact potentiel négatif que cela pourrait avoir sur le tourisme. La réticence a d'autant plus augmenté lorsque le Languedoc Roussillon a été inclus dans le zonage de l'appel d'offre concernant la construction de 2 GW de parcs éoliens.Il était donc pertinent de mener une enquête auprès des touristes du littoral pour évaluer comment l'installation de parcs éoliens, installés à des distances réalistes des côtés, pourrait affecter le tourisme balnéaire. Par ailleurs, il était également intéressant de proposer des stratégies que les stations balnéaires pourraient adopter pour augmenter le nombre de touristes et leurs profits, avec ou sans parc éolien. Pour répondre à ces questions, une enquête d'évaluation mobilisant la méthode des « choice experiment », a été réalisée durant l'été 2010, auprès de plus de 350 touristes, sur les plages languedociennes.Les résultats de cette enquête, présentés au chapitre 3, montrent que les coûts liés à la nuisance visuelle s'annulent lorsque le parc éolien est installé à des distances comprises entre 8 et 12 km de la côte. L'enquête a également mis en évidence une forte demande pour la mise en place de démarches éco responsable (favorisant les produits locaux, le vélo, les transports publics et les économies d'eau et d'énergie) par les stations balnéaires. Ainsi, nos résultats montrent que la nuisance vécue par l'installation d'un parc à 8 km de la cote serait compensée par la mise en place simultanée d'une « démarche verte ». Par ailleurs, la construction de récifs artificiels associé au parc éolien, qui permettrait l'accès à des loisirs récréatifs (plongée sous marine par ex.) générerait, d'après nos résultats, une augmentation des dépenses des touristes, si ce parc était installé à une distance d'au moins 5 km de la côte.De nos résultats émergent deux principaux constats :- L'implantation d'une éolienne à 12 km de la côte, sans aucune évolution de la station par ailleurs, n'aurait pas d'incidence négative sur le tourisme.- Si la station balnéaire met simultanément en place des actions environnementales et des activités récréatives, le parc éolien peut alors être conçu à partir d'une distance de 5 km de la côte.L'écart entre le Consentement à Payer pour un bien et le Consentement à Recevoir une compensation pour renoncer à ce même bien est un phénomène très largement mis en évidence en économie de l'environnement. Dans une seconde partie de la thèse, nous prenons en compte dans nos estimations économétriques cet écart entre les pertes et des gains dans la fonction d'utilité. En tenant compte de cette asymétrie, nous estimons une réduction de moitié de la nuisance vécue par rapport aux éoliennes si le parc éolien est déjà installé. D'un autre côté, les bénéfices liés aux activités récréatives et à une démarche éco responsable sont perçu comme plus élevés si ces activités étaient déjà mises en place. / The French government has committed itself to an ambitious target of boosting the offshore wind power capacity to reach 6 GW by 2020. Wind turbines onshore as well as offshore are highly contested on visual grounds. Affected stakeholders, ranging from business and property owners, fishermen and elected municipal planners, fear significant negative economic impacts on their ‘business' or their ‘property'. In the French Mediterranean region of the Languedoc Roussillon, the expectation is that the tourist industry will be chagrined in the presence of an offshore wind farm – giving a windy and cemented image of the region. Since talks began about 10 years ago, on the potential for ‘harvesting' the winds of the Mediterranean Sea, many postulates have been made with regard to the impact on coastal tourism. In particular, resistance mounted when plans to include the Languedoc Roussillon in the 2011 tender for the construction of 2 GW wind power capacity were materialising. In this light, it was considered of pertinence to investigate how offshore wind farms, installed at realistic distances from the coast (5, 8 or 12 km), would affect coastal tourism. Additionally, it was considered of interest to help define strategies that coastal community resort may adopt to boost visiting numbers or profit margins with or without wind farms. To answer these questions a full-scale choice experiment valuation survey with over 350 tourists was undertaken in the summer of 2010 on Languedoc beaches.Our survey results show (in chapter 3) that average visual disamenity costs tends to zero, when an offshore wind farm is installed somewhere between 8 and 12 km from the shore. We also find that there is considerable demand for “sustainable” coastal community resorts that favours local produce, bicycling, public transport, energy and water saving devices. Thus, our estimates show that a wind farm installed 8 km from the shore could be ‘compensated for' through the simultaneous ‘greening' of the coastal community resort. If in addition a wind farm is associated with artificial reefs and recreational user access, our results point to an actual rise in tourist related revenues when the wind farm is located min. 5 km from the coast. The policy recommendation is thus two fold: Everything else equals, a wind farm located 12 km offshore will have no negative incidence on tourism. With simultaneous application of a coherent environmental policy and wind farm associated recreational activities, wind farm siting can be conceived from 5 km and outwards.In a latter stage (chapter 5) we explicit account for the well-established fact that humans' over-estimate losses compared with equal-sized gains, in our econometric estimations. By incorporating so-called gain-loss asymmetry in the utility function, we observe that the WTP to remove wind farms had they already been installed is half the compensation required to accept their presence during a vacation. The disamenity costs associated with wind farm installation are thus of a significantly smaller magnitude had the wind farms already been installed. On the other hand, the welfare benefits associated with eco-efficiency and wind farm associated recreational activities are larger had they already been invigorated. The verdict is that asymmetry should be accounted for, or at least recognised in stated preference valuation studies that simultaneously use utility increasing and utility decreasing attributes.

The trend of offshore wind power is bigger and bigger wind turbines. Turbines are now becoming so big that existing installation vessels no longer are feasible and new bigger installation vessels are needed. Ship owners hesitate to order new vessels worried that the rapid turbine growth will continue and make also the new vessels obsolete in a few years. This can create a bottleneck in the offshore wind market.   This thesis assignment attempts to develop a telescopic tower as an alternative way of installing offshore wind turbines. A telescopic tower can decrease overall height and COG during marine installation, giving opportunity to install the largest wind turbines also with existing vessel fleet.   The method for developing the telescopic tower is to first find the main problems and functions of the concept. A design basis based on a 12 MW reference wind turbine is developed. Based on this reference turbine different solutions to the main problems and functions are developed by creative thinking, literature research, modelling, calculations and analysis. A cost/benefit analysis is performed to investigate if there is any economic potential in the developed solution. To complete the study other installation methods and telescopic tower concepts are investigated for benchmark comparison.   The telescopic tower will have two sections. Shoulders are welded to the inner wall of the lower tower. The upper tower fit inside the lower tower and a telescopic mechanism is installed below to lift the assembly as the mechanism climb the shoulders of the lower tower. The telescopic mechanism works much like a pin and hole mechanism used for jack-up rigs. The pins engage/disengage with the shoulders by the movement of linear actuators. The vertical climbing motion is provided by hydraulic cylinders. The power source is an HPU placed on the wind turbine external platform.   To connect the upper and lower tower permanently a friction connection with long slotted holes is used. This connection is developed for assembly of onshore towers in an EU-sponsored project called Histwin. The walls of the lower and the upper tower overlap at the connection and are pressed together by pretensioned bolts to create a friction surface that hold the loads from the upper tower.   The conclusion is that the telescopic tower is technically feasible and can be installed by the existing installation vessel fleet. The economic feasibility is dependent on the specific project characteristics, but there are scenarios where the telescopic tower can have great economical upside.

Durch Umwandlung unterschiedlichster Formen von Energie in mechanische oder elektrische Energie wird die Menschheit seit Jahrhunderten bei der Umsetzung von Arbeitsprozessen im Alltag und bei der industriellen Nutzung unterstützt. Strömende Medien wie Wasser oder Wind gelten dabei als die ältesten Energielieferanten. Im Rahmen der Dissertation wird das Konzept einer zugspannungsverankerten Plattform für Offshore Windenergieanlagen (WEA) vorgestellt, wobei neben den, für diesen Plattformtyp typischen, vertikalen auch geneigte Verankerungselemente Verwendung finden. Diese Art der Verspannung einer zugspannungsverankerten Plattform, respektive ’Tension Leg Platfrom’ (TLP) ist bisher von keiner Quelle bekannt und stellt ein Alleinstellungsmerkmal dar. Folglich sollen Untersuchungen zum dynamischen Verhalten schwimmender Gründungen für Offshore WEA, im Speziellen zu einer TLP mit vertikalen und geneigten Ankerelementen, im Rahmen dieser Arbeit erstmalig vorgestellt werden. Die Plattform ist ein modular gestaltetes Tragwerk bestehend aus großen Rohren und mit integrierten zylindrischen Auftriebskörpern. Diese erzeugen im Transportzustand der Plattform vom Hafen zum Einsatzort und im Betriebszustand innerhalb eines Windparks den nötigen Auftrieb. Infolge der speziellen Art der Verspannung werden die Bewegungen der TLP durch die, aus den Belastungen resultierenden, Seildehnungen dominiert. Damit stellte die TLP im Vergleich zu anderen schwimmenden Gründungen ein bewegungsarmes System dar. Inhalt der hier vorgelegten Arbeit sind Untersuchungen zum dynamischen Verhalten schwimmender Offshoregründungen, im speziellen einer TLP für Windenergieanlagen. Es wurden unterschiedliche Tragstrukturen für TLP-Systeme entwickelt und im Rahmen von Modellversuchen getestet. Den Kern der Arbeit bildet der Vergleich des dynamischen Tragverhaltens der unterschiedlichen Plattformen unter Berücksichtigung der geometrischen und strukturellen Randbedingungen.

Für Offshore-Windenergieanlagen (OWEA) wird die Überwachung mittels Monitoringsystemen immer wichtiger für den effizienten Betrieb. Problematisch ist, dass nicht nur die OWEA selbst, sondern auch die Monitoringsysteme altern. Für verlässliche Monitoringsysteme müssen daher auch deren Alterungsprozesse analysiert werden, damit das System lebensdauerumfassend an der OWEA verwendbar ist. Hierfür wurden Laser-Triangulationssensoren untersucht, die unterschiedlichen Temperaturen und Luftfeuchten ausgesetzt wurden. Das Messsignal wurde temperaturkompensiert und hinsichtlich seiner Messunsicherheit bewertet. Ferner ergaben erste Alterungsversuche, dass noch keine signifikanten Alterungserscheinungen aufgetreten sind.

As has been the case for onshore wind systems, the environmental effects of offshore wind farms are expected to play an important part of the development of future large-scale wind energy systems. This paper presents a detailed review of the status of, and recent developments in, research on the environmental impacts of fixed and floating offshore wind turbine systems. The primary information that has been reviewed has come from European sources where there are a significant number of offshore installations, but some work on this subject has been carried out recently in the United States. Information, from an extensive review, is presented on the environmental impacts of fixed and floating offshore wind turbines on benthic organisms, fish, marine mammals, avian species and bats. The environmental impacts of fixed and floating systems are anticipated to vary due to multiple parameters that need to be taken into account when identifying environmental impacts. Additionally, there are variations in the impact throughout the lifecycle of the offshore wind turbines. The primary focus for this paper is on the environmental impacts through the scope of barrier and habitat impacts in addition to the anticipated avian and bat fatalities. A noise propagation model is used to determine the extent of effects due to the installation of fixed and floating support structures using piling installation methods. Finally, a summary of progress in all the major environmental impact areas is given along with recommendations for future research.

Power generation of the future will be dominated by renewable energy sources. This is a positive trend as society aims to improve sustainability, energy security, and reduce CO2 emissions. This progress however bears challenges for the power systems of the future. One area of particular concern is the blackstart recovery capability of the power systems following blackout events that disrupt electricity supply, as traditional blackstart suppliers have originated from unsustainable power sources. As new sustainable technologies are explored to fill the void, offshore wind power has been identified as a potential suitor to address future blackstart deficiencies. However, following a blackout event that leaves an offshore wind farm isolated, the current technology does not allow for start-up of the wind farm in an islanded mode without assistance from the onshore grid. Hence, a STATCOM with active power storage, known as an ES-STATCOM, is the proposed solution to energize the offshore wind farm to operate in an islanded mode, in preparation for assisting the onshore grid with blackstart. An EMT model and simulation of an ES-STATCOM with grid forming control capabilities and the surrounding offshore wind farm export system were developed in this thesis to assess the viability of the STATCOM solution in energization. The results are promising and show that the ES-STATCOM is in fact able to energize the offshore system to a stable voltage, while avoiding high order harmonics and large overvoltages that have the potential to cause damage to expensive subsea power system components. Ultimately, this thesis serves as a proof-of-concept for blackstart technology, providing useful insights towards the maturity of offshore wind-based blackstart providers of the future. / Framtidens elproduktion kommer att domineras av förnybara energikällor. Detta är en positiv trend eftersom samhället strävar efter att förbättra hållbarheten, tryggheten gällande energiförsörjning samt minska koldioxidutsläppen.. Denna utveckling innebär dock utmaningar för framtidens kraftsystem. Ett område som är särskilt oroande är kraftsystemens förmåga att återhämta sig efter blackout som stör elförsörjningen, eftersom de traditionella leverantörerna av ett strömavbrott har sitt ursprung i ohållbara kraftkällor. I takt med att man utforskar ny hållbar teknik för att fylla tomrummet har havsbaserad vindkraft identifierats som en potentiell kandidat för att åtgärda framtida brister vid svartstart. Efter ett strömavbrott som gör att en havsbaserad vindkraftpark blir isolerad från kraftnätet kan vindkraftparken inte startas upp i ett ö-läge utan hjälp från landnätet med nuvarande teknik. Därför föreslås en STATCOM med aktiv energilagring, en så kallad ES-STATCOM, som lösning för att ge energi till havsbaserade vindkraftparker så att de kan fungera i ö-läge, som en förberedelse för att hjälpa landnätet med svartstart. En EMT-modell och simulering av en ES-STATCOM med nätbildande kontrollfunktioner och det omgivande exportsystemet för havsbaserade vindkraftparker utvecklades i denna avhandling för att bedöma lönsamheten hos STATCOM-lösningen för energitillförsel. Resultaten är lovande och visar att ES-STATCOM kan försörja det havsbaserade systemet med den en energi som krävs för en stabil spänning, samtidigt som man undviker harmoniska övertoner av hög ordning och stora överspänningar som har potential att skada dyra komponenter i det havsbaserade kraftsystemet. I slutändan tjänar denna avhandling som ett proof-of-concept för blackstart-teknik och ger användbara insikter om hur mogna framtida leverantörer av svartstart-teknik för havsbaserad vindkraft är.

Previous research has displayed that multi-source farms provide an opportunity to reduce the cost of energy and improve the energy output quality. This thesis assesses the cost competitiveness of co-located wind-wave farms, specifically floating offshore wind (FLOW) turbines and CorPower’s wave energy converters (WEC). This research was conducted in collaboration with CorPower, a Swedish WEC developer. A cost model is generated, which calculates the levelized cost of energy (LCOE) utilizing a life-cycle cost analysis. The model is developed by combining CorPower’s existing cost model with an agglomeration of FLOW cost models from previous studies. An in depth literature research informs about synergies, which are translated into shared costs within the model. The cost model is applied to a site on the Northern coast of Portugal; the location of a FLOW farm project under development. Including wave energy, improves the annual energy production of the farm by up to 10%. However, the effects on power smoothing are negligible, due to the high seasonal variability of the wave resource and the minimal complementarity of the two energy sources. The LCOE of a 1GW 50% wind - 50% wave farm is 63€/MWh. The high initial investment costs of the wind farm results in the standalone wind LCOE of 73€/MWh. The strong capacity factor of the WECs cause the LCOE to reduce to 55€/MWh, when evaluating a standalone wave farm. In all co-location configurations, savings for FLOW and wave farm developers are exhibited. The highest savings are identified for small wind/wave arrays co-located in large farms. This results in an LCOE reduction of up to 4.5% for both wind and wave farm developers. The largest relative savings are found in the DEVEX costs and the electrical transmission installation costs. The identified cost calculations and savings are inline with previous studies. The savings are in the lower range compared to other studies, due to the conservative estimations of the degree of shared costs. The cost model provides a tool, that can be continuously updated with the most recent findings of cost inputs and wind-wave synergies, i.e. shared cost opportunities. This thesis’ results reflect how co-locating wind and wave farms can improve the cost-competitiveness of both technologies. Nevertheless, more in depth research is required to comprehend the full potential of co-located wind-wave farms. There is a necessity of collaboration between wind and wave industry members to ensure that the synergies and shared cost-opportunities identified, are fully exploited. / Tidigare forskning har visat att parker med flera källor ger möjlighet att minska energikostnaderna och förbättra energiproduktionens kvalitet. I den här avhandlingen utvärderas kostnadskonkurrenskraften hos samlokaliserade vind- och vågkraftsparker, särskilt flytande havsbaserade vindkraftverk (FLOW) och CorPowers vågenergiomvandlare (WEC). Denna forskning genomfördes i samarbete med CorPower, en svensk WEC-utvecklare. En kostnadsmodell genereras, som beräknar den nivellerade energikostnaden (LCOE) med hjälp av en livscykelkostnadsanalys. Modellen är utvecklad genom att kombinera CorPowers befintliga kostnadsmodell med en agglomeration av FLOW-kostnadsmodeller från tidigare studier. En djupgående litteraturstudie ger information om synergier, som översätts till delade kostnader i modellen. Kostnadsmodellen tillämpas på en plats på Portugals norra kust, där ett FLOW-anläggningsprojekt är under utveckling. Genom att inkludera vågenergi förbättras parkens årliga energiproduktion med upp till 10%. Effekterna på effektutjämningen är dock försumbara, på grund av vågresursens stora säsongsvariationer och de två energikällornas minimala komplementaritet. LCOE för en 1GW 50% vind - 50% vågkraftspark är 63€/MWh. De höga initiala investeringskostnaderna för vindkraftsparken resulterar i en LCOE för fristående vindkraft på 73 €/MWh. Den starka kapacitetsfaktorn för WECs gör att LCOE minskar till 55€/MWh, vid utvärdering av en fristående vågkraftspark. I alla samlokaliseringskonfigurationer uppvisas besparingar för FLOW och vågparksutvecklare. De största besparingarna identifieras för små vind-/vågkraftsparker som samlokaliseras i stora parker. Detta resulterar i en minskning av LCOE med upp till 4,5% för både vind- och vågparksutvecklare. De största relativa besparingarna finns i DEVEX-kostnaderna och installationskostnaderna för elektrisk överföring. De identifierade kostnadsberäkningarna och besparingarna är i linje med tidigare studier. Besparingarna ligger i det lägre intervallet jämfört med andra studier, på grund av de konservativa uppskattningarna av graden av delade kostnader. Kostnadsmodellen är ett verktyg som kontinuerligt kan uppdateras med de senaste rönen om kostnadsingångar och synergier mellan vind och våg, dvs. möjligheter till delade kostnader. Resultaten i denna avhandling visar hur samlokalisering av vind- och vågkraftsparker kan förbättra kostnadskonkurrenskraften för båda teknikerna. Det krävs dock mer djupgående forskning för att förstå den fulla potentialen hossamlokaliserade vind- och vågparker. Det finns ett behov av samarbete mellanvind- och vågkraftsindustrin för att säkerställa att de identifierade synergierna ochgemensamma kostnadsmöjligheterna utnyttjas fullt ut.

Recognizing the imperative transition towards renewable energy sources to combat climate change, this study explores the outlooks for offshore wind power in Norway, a country endowed with extensive coastlines and favourable wind conditions. The thesis sets out to support decision-making processes by synthesizing contemporary research and applying context-specific insights to the southern half of the Norwegian economic zone (NEZ) into a comprehensive Spatial-Multi-criteria Analysis (SMCA). Through meticulous research, sub-criteria relevant to the geographical information systems-based SMCA are identified across four major categories: Wind, Techno-economic, Environ-mental, and Social considerations. Through the adoption of the Analytic hierarchy process (AHP) framework, the analysis generates suitability maps for all identified sites within the NEZ, facilitating a ranking procedure for both floating and bottom-fixed sites. By, among else, incorporating potential grid connection points and distance to suitable ports, this thesis offers a novel contribution to the limited body of literature on offshore wind power SMCA in the NEZ. Additionally, through state of the art data sets on mammal presence and cumulative impact on seabirds, the study not only advances the academic discourse on offshore wind power planning but also offers practical tools for policymakers and industry practitioners. The findings underscore the complexity of offshore wind farm siting, highlighting the impor-tance of a balanced consideration of various criteria to ensure sustainable and economically viable energy production. Significantly, amongst sites suitable for floating foundations, Ves-tavind A emerges as the prime location for wind farm development. The bottom rankings, however, are claimed by different sites depending on which weighting schema is applied. For future studies on the topic, important building blocks include incorporating data on seabed conditions such as geology and sloping into the SMCA alongside including more sub-criteria linked to met-ocean conditions (e.g., cut-out periods of the wind turbines caused by extreme weather). / Mot bakgrund av den globala omställningen till en alltmer grön energimix utforskar denna studie utsikterna för havsbaserad vindkraft i Norge, ett land med vidsträckta kustlinjer och gynnsamma vindförhållanden. Uppsatsen syftar till att stödja beslutsprocesser genom att sammanställa samtida forskning och tillämpa insikter anpassade till den södra halvan av Norges ekonomiska zon (NEZ) i en omfattande rumslig analys. Slutprodukten blir en relativ rangordning av en uppsättning områden som alla, enligt norska myndigheter, lämpar sig för installation av havsbaserad vindkraft. Genom noggrann efterforskning identifieras olika faktorer (subkriterier) som anses rel-evanta för den rumsliga analysen, dessa delas up i fyra övergripande kategorier: Vind, Tekno-ekonomiska faktorer, Miljöaspekter och Sociala aspekter. Med hjälp av en särskild viktningsmodell, där faktorerna ställs mot varandra och prioriteras utifrån deras relativa betydelse, genereras lämplighetskartor för alla platser inom studieområdet. Denna process ligger sedermera till grund för den ovannämnda rangordningen och görs både för platser som är tänkta för flytande och bottenfast havsbaserad vindkraft. Genom att bland an-nat inkludera potentiella anslutningspunkter till elnätet och avstånd till hamnar, som speficifkt lämpars sig för vindturbininstallationer, bidrar detta forskningsarbete med nytt innehåll till den vetenskapliga litteraturen. Därtill kan studien, utöver att bidra till den akademiska diskursen, komma att fungera som ett praktiskt verktyg för beslutsfattare och yrkesverksamma inom industrin. Resultaten påminner läsaren om komplexiteten i placeringen av havsbaserade vindkraftverk, vilket bekräftar vikten av en balanserad beaktning av olika kriterier. Detta för att kunna säkerställa att nya energiprojekt presterar bra utifrån ett miljömässigt och socialt perspektiv samtidigt som den ekonomiska lönsamheten säkras. Sett till de områden som studien utreder framstår Vestavind A som det bäst lämpade området för utveckling av havsbaserad vindkraft. De lägsta placeringarna upptas emellertid av olika platser beroende på hur de olika kriterierna viktas. Några förslag på hur denna studie kan utvecklas för att fortsatt kunna bidra till nya insikter inom forskningsområdet är att inkludera data om bottenförhållanden (exempelvis geologi och lutning) i den rumsliga analysen, samt att addera subkriterier med en naturlig koppling till meteorologiska aspekter såsom avbrottsperioder för vindturbiner till följd av extremväder.

The selection of the bulk power transmission technology in offshore wind farms is strongly related to the wind farm size and its distance to shore. Several alternatives can be evaluated depending on the rated power of the offshore wind farm, the transmission losses and the investment cost for constructing the transmission system. However, when is necessary to connect larger and more distant offshore wind farms; the best technological solution tends to the transmission system based on highvoltage and direct-current with line commutated converters (LCC-HVdc). This dissertation proposes the use of diode-based rectifers as a technical alternative to replace the thyristor-based rectifers in an LCC-HVdc link with unidirectional power flow. This alternative shows advantages with regard to lower conduction losses, lower installation costs and higher reliability. Nonetheless, as a counterpart the offshore ac-grid control performed by the thyristor-based HVdc rectifer is no longer available. This lack of control is compensated by using new control strategies over an offshore wind farm composed by wind turbines with permanent-magnet generators and fully-rated converters. The control strategies have been based mainly on the ability of the wind turbine grid-side converter to perform the control of the offshore ac-grid voltage and frequency. The performance has been evaluated by using PSCAD. Wherein, the most common grid disturbances have been used to demonstrate the fault-ride-through capability as well as the adequate steady state and transient response. / Rodríguez D'derlée, JJ. (2013). Control strategies for offshore wind farms based on PMSG wind turbines and HVdc connection with uncontrolled rectifier [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34510