One way to tackle the climate change society is facing today is through the change to renewable energy sources, such as wind power. Today, a trend when it comes to technology is that products are evolving into becoming more cyber-physical systems (CPS) by integrating functions realized with mechanics, control and communication. One challenge for CPS is to find cost-effective and reliable sensor solutions.  The purpose of this project is to lay the foundations for an intelligent CPS with the help of sensors and condition monitoring methods that, with further development, can reduce the downtime of a wind turbine. Thus, the reliability of the wind turbine and the profitability of its investors increase. The aim of the work is to develop an overall concept for a sensor package with analysis methods that enable real-time diagnosis in the gearbox of a wind turbine. This sensor package should be able to monitor the most common problems that arise in the gearbox and it should also be able to be used as a basis for a possible development of a CPS in the future.  The work is based on an information search that enables the creation of a list of requirements. This then forms the basis for concept generation through the use of a function/means tree and concept evaluation through the use of elimination matrix, weight determination matrix and weighted criteria matrix.  The work concludes that there are four main types of failures that occur in the gearbox and that should be monitored. These are scuffing, micropitting, propagation of cracks and bearing failure. The final concept uses vibration analysis for monitoring of micropitting, crack propagation and bearing failure, oil analysis for monitoring of scuffing and micropitting and temperature measurement for monitoring of scuffing and bearing failure. For vibration analysis, piezoelectric sensors are used, for oil analysis electromagnetic sensors and for temperature measurement resistance thermometers are used.  The work finds that it is appropriate in this day and age to use well-established methods for condition monitoring in the gearbox of wind turbines. / Ett sätt att tackla de klimatförändringar samhället står inför idag är genom omställningen till förnybara energikällor, såsom vindkraft. Idag är en trend när det kommer till teknik att produkter utvecklas till att allt mer bli cyberfysiska system (CPS) genom att de integrerar funktioner som realiseras med mekanik, reglering och kommunikation. En utmaning för CPS är att hitta kostnadseffektiva och tillförlitliga sensorlösningar.  Syftet med detta projekt är att lägga grunden till ett intelligent CPS med hjälp av sensorer och tillståndsövervakningsmetoder som med vidare utveckling ska kunna minska stilleståndstiden hos ett vindkraftverk. Således ökar tillförlitligheten hos vindkraftverket samt räntabiliteten för investerarna av dessa. Arbetets mål är att utveckla ett övergripande koncept för ett sensorpaket med analysmetoder som möjliggör realtidsdiagnos i växellådan hos ett vindkraftverk. Detta sensorpaket ska kunna övervaka de vanligaste problemen som uppstår i växellådan och ska kunna användas som grund för eventuell utveckling av ett CPS i framtiden.  Arbetet grundas i en informationssökning som möjliggör skapandet av en kravspecifikation. Denna ligger sedan till grund för konceptgenerering genom användandet av funktions/medelträd samt konceptutvärdering genom användandet av elimineringsmatris, viktbestämningsmatris samt kriterieviktsmetoden.  I arbetet framkommer att det finns fyra huvudsakliga skador som uppkommer i växellådan och som bör övervakas. Dessa är scuffing, mikropitting, sprickpropagering och lagerhaveri. Det slutgiltiga konceptet använder vibrationsanalys för övervakning av mikropitting, sprickpropagering och lagerhaveri, oljeanalys för övervakning av scuffing och mikropitting samt temperaturmätning för övervakning av scuffing och lagerhaveri. Vid vibrationsanalys används piezoelektriska sensorer, vid oljeanalys elektromagnetiska sensorer och för temperaturmätning resistanstermometrar.  Arbetet konstaterar att det i dagsläget är lämpligt att använda väletablerade metoder för tillståndsövervakning i växellådan hos vindkraftverk.

Under det senaste decenniet har miljöfrågan blivit ett ständigt växande problem. Fristående organisationer som IPCC, som är FN:s friståendeorgan för att sammanfatta och bedöma vetenskapen relaterad till den globala uppvärmningen, bedömer att den globala uppvärmningen till följd av mänsklig inverkan kommer att överstiga 1,5 grader år 2100 och att våra ekosystem kommer att påverkas negativt till icke återhämtningsbara nivåer. För att förbättra det kritiska läget har efterfrågan på förnybar energi ökat kraftigt. Till följd av detta så har vindkraftsindustrin utvecklatsi hög grad och utvecklas fortfarande. I detta kandidatexamensarbete undersöks en konceptidé om ett hopfällbart vindkraftverk för att öka årlig energiproduktion samt reducera de aerodynamiskalasterna. Hypotesen för detta arbete är att ett hopfällbart vindkraftverk kan ökaden årliga energiproduktionen med 100% genom en fördubbling av sveparean med samma mängd insatsmaterial. Konstruktionslösningen för hopfällbarhet antas vara löst av andra och tidigare konstruktionslösningar för hopfällbarhet har undersökts och presenterats. För att analysera en potentiell ökning av årlig energiproduktion användes NREL:s mjukvara WISDEM samt deras 3,4-MW landbaserade referensvindkraftverk. Resultatet tydde på att med dubbel sveparea kan man få en ökning med 79% av den årliga energiproduktionen, en ökning med 48% av lyftkraften och en ökning med 84%av motståndskraften. / During the last decade the environmental impact has become an increasingly growing problem. The IPCC have reported the ever increasingly environmental impact from fossil fuels and emissions of greenhouse gases. Their assessment from 2021 notes that the environmental impact because of humans will lead to at least an increase of 1.5 degrees increase in temperature by the year 2100 and that our ecosystems will be irreversibly damaged. To combat these changes the demand for renewable energy sources has increased. This increase in demand has led to the wind energy sector growing rapidly with a lot of recent developments in the field. In this bachelor thesis a concept idea of a foldable wind turbine has been proposed. The goal is to determine if an increase in annual energy production of 100% is possible with a doubling of the rotor swept area and a constant mass. The mechanism for foldability is assumed to be invented and research on previous works looking into foldability in wind turbines has been performed. To analyze the potential increase in annual energy production the software WISDEM, developed by NREL, was used together with their 3.4-MW reference wind turbine. The results showed that with a doubled rotor swept area an increase in annual energy production of 79% was achieved together with an increase of 48% of the lift force and an increase of 84% of the drag force.

No description available.

Offshore wind turbines have the potential to be an important part of the United States' energy production profile in the coming years. In order to accomplish this wind integration, offshore wind turbines need to be made more reliable and cost efficient to be competitive with other sources of energy. To capitalize on high speed and high quality winds over deep water, floating platforms for offshore wind turbines have been developed, but they suffer from greatly increased loading. One method to reduce loads in offshore wind turbines is the application of structural control techniques usually used in skyscrapers and bridges. Tuned mass dampers are one structural control system that have been used to reduce loads in simulations of offshore wind turbines. This thesis adds to the state of the art of offshore wind energy by developing a set of optimum passive tuned mass dampers for four offshore wind turbine platforms and by quantifying the effects of actuator dynamics on an active tuned mass damper design. The set of optimum tuned mass dampers are developed by creating a limited degree-of-freedom model for each of the four offshore wind platforms. These models are then integrated into an optimization function utilizing a genetic algorithm to find a globally optimum design for the tuned mass damper. The tuned mass damper parameters determined by the optimization are integrated into a series of wind turbine design code simulations using FAST. From these simulations, tower fatigue damage reductions of between 5 and 20% are achieved for the various TMD configurations. A previous study developed a set of active tuned mass damper controllers for an offshore wind turbine mounted on a barge. The design of the controller used an ideal actuator in which the commanded force equaled the applied force with no time lag. This thesis develops an actuator model and conducts a frequency analysis on a limited degree-of-freedom model of the barge including this actuator model. Simulations of the barge with the active controller and the actuator model are conducted with FAST, and the results are compared with the ideal actuator case. The realistic actuator model causes the active mass damper power requirements to increase drastically, by as much as 1000%, which confirms the importance of considering an actuator model in controller design.

En undersökning av vindturbiners hydraulolja med avseende på partikelinnehåll har genomförts. Med syftet att öka tillgängligheten på Statkrafts vindturbiner genom ändrade underhållsrutiner. Målsättningen har varit att minska mängden partiklar och hitta en lösning för förbättrat underhåll rörande hydrauloljan. För att lösa detta har en litteraturstudie, intervjuer och oljeprovtagning genomförts. Vidare installerades ett offlinefilter för att undersöka en potentiell lösning för partikelavskiljning och förändring av underhållsrutiner. Resultaten från oljeprovtagningen visade på höga halter av partiklar för de små och medelstora partiklarna, en låg viskositet och höga värden av föroreningar och vatteninnehåll. Samtliga parametrar förbättrades efter 24 timmar filtrering där partikelinnehållet hade minskat till godtyckliga värden tillsammans med vatteninnehållet samt att viskositeten hade en liten ökning. Efter filtrering i en vecka hade vissa av värdena gått upp ytterligare och partikelhalterna för små och medelstora partiklar hade ökat. Detta tros bero på provtagning i samband med återföring av smutsig olja från pitchcylindrarna. Lösningar på reningen av oljan undersöktes potentiellt att vara filtrering, partikelräknare, IR termografi och oljebyte. Där filtrering i kombination med partikelräknare i dagsläget ger det mest ekonomiska och lämpliga lösningen för företagets underhållsstrategi och målsättning. Slutsatsen från arbetet är att offlinefiltreringen fungerar och att underhållsrutinerna skulle kunna optimeras ytterligare om partikelräknare installerades i anslutning till detta. Ekonomiskt är denna lösning realistisk men för att göra större ändringar i underhållsrutinerna behövs vidare studier av filtreringstid och eventuellt manuell hantering / An investigation has been done of the particles in hydraulic oil in wind turbines. The purpose of this has been to increase the availability for Statkraft´s wind turbines through changing their maintenance routines. The goal has been to lower the particle count and finding a solution for bettering their maintenance with the hydraulic oil. A literature study, interviews and testing of the hydraulic oil has been done to solve this. Furthermore, an offline filtration unit has been mounted to investigate whether that may be a potential solution for clearing the oil from particles and if it can be useful for changing the maintenance routines within the oil service. The results from the oil analysis showed upon high particle counts for the smaller and middle-sized particles, low viscosity and high values for contamination and water content. All parameters were improved after 24 hours of filtration where the particle count had lowered to arbitrary values together with the water count and the viscosity had a slight increase. After filtration for a week some of the parameters had gone up slightly and the values for small and middle-sized particles hade increased. This is believed to be due to oil testing at the same time as the returning of the unclean oil from the pitch cylinders. Different solutions for clearing the oil were investigated, such as filtration, a particle counter and an oil change. The result from the investigation showed that filtration together with a particle counter is the best solution. This fits both economically and the goal for the business as of today. The conclusion of this work is that the offline filtration works and that the availability routines could be optimized further if a particle counter was to be installed together with the filtration unit. Economically this solution is most realistic but to be able to do any improvements on the availability routines further investigation of the filtration intervals has to be done with potential manual labour

The Cal Poly Sustainable Power for Electrical Resources (SuPER) project is a solar power DC distribution system designed to autonomously manage and supply the energy needs of a single family off-the-grid home. The following thesis describes the improvement and re-design of a MATLAB Simulink model for the Cal Poly SuPER system. This model includes a photovoltaic (PV) array, a lead-acid gel battery with temperature effects, a wind turbine model, a re-designed DC-DC converter, a DC microgrid, and multiple loads. This thesis will also include several control algorithms such as a temperature controlled thermoelectric (T.E.) cooler, intelligent load switching, and an intelligent power source selector. Furthermore, a seven day simulation and evaluation of the results are presented. This simulation is an important tool for further system development, re-design, and long term system performance prediction.

Inverse analysis of nonlinear dynamic systems is an important area of research in the eld of structural health monitoring for civil engineering structures. Structural damage usually involves localized nonlinear behaviors of dynamic systems that evolve into different classes of nonlinearity as well as change system parameter values. Numerous parametric modal analysis techniques (e.g., eigensystem realization algorithm and subspace identification method) have been developed for system identification of multi-degree-of-freedom dynamic systems. However, those methods are usually limited to linear systems and known for poor sensitivity to localized damage. On the other hand, non-parametric identification methods (e.g., artificial neural networks) are advantageous to identify time-varying nonlinear systems due to unpredictable damage. However, physical interpretation of non-parametric identification results is not as straightforward as those of the parametric methods. In this study, the Multidegree-ofFreedom Restoring Force Method (MRFM) is employed as a semi-parametric nonlinear identi- fication method to take the advantages of both the parametric and non-parametric identification methods. The MRFM is validated using two realistic experimental nonlinear dynamic tests: (i) largescale shake table tests using building models with different foundation types, and (ii) impact test using wind blades. The large-scale shake table test was conducted at Tongji University using 1:10 scale 12-story reinforced concrete building models tested on three different foundations, including pile, box and fixed foundation. The nonlinear dynamic signatures of the building models collected from the shake table tests were processed using MRFM (i) to investigate the effects of foundation types on nonlinear behavior of the superstructure and (ii) to detect localized damage during the shake table tests. Secondly, the MRFM was applied to investigate the applicability of this method to wind turbine blades. Results are promising, showing a high level of nonlinearity of the system and how the MRFM can be applied to wind-turbine blades. Fuiii ture studies were planned for the comparison of physical characteristic of this blade with blades created made of other material.

Offshore floating wind turbines represent the future of wind energy. However, significant challenges must be overcome before these systems can be widely used. Because of the dynamics of offshore floating wind turbines -- surge, sway, heave, roll, pitch, and yaw -- and the resulting interactions between the rotor and generated wake, the aerodynamic analysis methods and design codes that have found wide use throughout the wind energy industry may be inadequate. Application of these techniques to offshore floating wind turbine aerodynamics may result in off-optimal designs, effectively handicapping these next-generation systems, thereby minimizing their full potential. This dissertation will demonstrate that the aerodynamics of offshore floating wind turbines are sufficiently different from conventional offshore and onshore wind turbines, warranting the use of higher fidelity analysis approaches. It will outline the development and validation of a free vortex wake code, the Wake Induced Dynamics Simulator, or WInDS, which uses a more physically realistic Lagrangian approach to modeling complex rotor-wake interactions. Finally, results from WInDS simulations of various offshore floating wind turbines under different load conditions will be presented. The simulation results indicate that offshore floating wind turbine aerodynamics are more complex than conventional offshore or onshore wind turbines and require higher fidelity analysis approaches to model adequately. Additionally, platform pitching modes appear to drive the most aerodynamically-significant motions, followed by yawing modes. Momentum balance approaches are shown to be unable to accurately model these dynamic systems, and the associated dynamic inflow methods respond to velocity changes at the rotor incorrectly. Future offshore floating wind turbine designs should strive to either minimize platform motions or be complementarily optimized, via higher fidelity aerodynamic analysis techniques, to account for them. It is believed that this dissertation is the first in-depth study of offshore floating wind turbine aerodynamics and the applicability of various analysis methods.

Numerical simulations using CFD methods are performed for wind turbine applications. The aim of the project is to get a better understanding of the wake behaviour, which is needed since today’s industrial design codes for wind power applications are based on the BEM (Blade Element Momentum) method. This method has been extended with a number of empirical corrections not based on physical flow features. The importance of accurate design models does also increase as the turbines become larger. Therefore, the research is today shifting toward a more fundamental approach, aiming at understanding basic aerodynamic mechanisms. The result from the CFD simulation is evaluated and special interest is given to the circulation and the position of vortices. From these evaluations, it will hopefully be possible to improve the engineering methods and base them, to a greater extent, on physical features instead of empirical corrections. The simulations are performed using the program ”EllipSys3D” developed at DTU (The Technical University of Denmark). The Actuator Line Method is used, where the blade is represented by a line instead of a large number of panels. The forces on that line are introduced by using tabulated aerodynamic coefficients. In this way, the computer resource is used more efficiently since the number of node points locally around the blade is decreased, and they can instead be concentrated in the wake behind the blades. An evaluation method to extract values of the circulation from the wake flow field is developed. The result shows agreement with classical theorems from Helmholtz, from which it follows that the wake tip vortex has the same circulation as the maximum value of the bound circulation on the blade. / QC 20101203

Distributed generators (DGs) with integration of renewable resources (RRs) such as photovoltaic (PV) and wind turbine have been widely considered to reduce the dependency on conventional power generation systems along with enhancement of the quality and sustainability of the power system. Recently, DC microgrid has gained popularity in many real-world applications such as rural electrification due to its simplicity and low power losses. However, the power variability of renewable resources and continuous change in load demand imposes risks of power mismatch in standalone DC systems that increase the chances of stability and reliability issues. Therefore, complementary generation and/or storage systems are coupled with standalone DC microgrid to mitigate the power fluctuations and maintain a power balance in the system. This dissertation presents a power management strategy (PMS) based on model predictive control (MPC) for a standalone DC microgrid. A control scheme for a standalone DC microgrid system with RRs, storage, and load is desired to have the capability of effective power management that maximizes the extraction of energy from renewable generators, minimizes the transients in the system during disturbances, and protects the storage from over/under charging conditions. As a part of the proposed MPC, an optimization problem is formulated to meet the voltage performance in the system with respect to operating conditions and constraints. The proposed PMS uses the ARIMA prediction method to forecast the load and environmental parameters. The predicted parameters are utilized to estimate the future performance of the system by solving the dynamic model of the system, and a cost function is optimized to generate suitable control sequences. This research also presents detailed mathematical models of the considered systems. This dissertation presents an extensive simulation-based analysis of the proposed approach. With the proposed control, maximum utilization of the renewable generators has been achieved, and the DC bus voltage is regulated at nominal value with minimum transients under various load/environmental disturbances. Moreover, the research investigates the proposed MPC based on ARIMA prediction by comparing the performance of different types of prediction methods. The dissertation also measures the effectiveness of the proposed MPC by comparing its performance with a conventional PI controller.