Search

For the detailed validation and verification of the capabilities of QBlade-Ocean in work package 2 (WP2) of FLOATECH, a detailed definition of the three considered models was recently presented in Deliverable 2.1 [1]. This document can be seen as a continuation of that work as the three aero-hydro-elastic models within QBlade-Ocean were thoroughly validated against experimental results and other state-of-the-art aero-servo-hydro-elastic simulation codes with complex load cases. As a first check, the models were validated in static and decay tests to assure that their natural frequencies and damping coefficients align. Secondly, regular and irregular wave only load cases were carried out to isolate the hydrodynamic response and quantify the hydrodynamic accuracy of QBlade-Ocean. Finally, combined irregular wave with turbulent wind load cases were analysed in order to obtain insight into the accuracy of QBlade- Ocean in complex load cases where aero-, hydro-, servo- and structural dynamics concurrently play a significant role. Of the simulated models, two include experimental validation: the upscaled 10 MW SOFTWIND experimental turbine mounted on a spar floater and the upscaled 5 MW OC5 experimental turbine mounted on a semi-submersible floater. Both models were additionally set up in the open-source software OpenFAST to, on the one hand, compare the performance of both software tools and on the other hand, as a preparatory step for a full-scale code-to-code comparison with the aim of uncertainty identification between the codes occurring later in WP2. The third model – the DTU 10MW Reference Wind Turbine mounted on the Hexafloat floater – is used for numerical validation against the established commercial code DeepLines Wind™ which was used during the design process of the floater by the company SAIPEM. The present document includes results of a selected set of load cases that demonstrate the capabilities of QBlade-Ocean compared to experimental results and the considered numerical codes. Links to the updated QBlade-Ocean models as well as the OpenFAST model are provided in the relevant sections of each model

This document is a deliverable of the FLOATECH project, funded under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101007142. The aim of this document is to present a report detailing the work carried out relevant to the main tasks of Deliverable 1.3 of work package 1 of the project. The main task of this work package isthe development of the open-source wind turbine simulation software suite QBlade to enable the simulation of offshore wind turbine platforms. Deliverable 1.3 revolves around the preparation of the software package and corresponding training material to facilitate uptake of the code and general public use. This is composed of three separate subtasks: - Training Manual: This has been prepared as an online manual to provide the user with all the necessary information to correctly operate the software. This has been prepared with two sections: The theory manual gives a detailed description of the physical models applied in the implementation of QBlade. The user guide gives a detailed overview of generating simulations and specifying inputs to the various modelling tools available in the software. - Project Partner Workshop: In order to ensure that the project partners of FLOATECH have the material and experience necessary to generate simulations within QBlade, a project partner workshop was held from Wed. 22nd to Friday 24th June 2022. A combination of presentation material and practical exercises was used to provide the users with practical experience applying the software. - Public Dissemination: The QBlade website has been prepared to ensure that the public has easy access to the source code and the compiled binaries on a range of platforms. In addition, the QBlade website will serve as a platform for communications regarding the user manual, past and upcoming events and publications relevant to the use of QBlade. These three tasks constitute the dissemination of the QBlade software along with the necessary material for members of the public and industry to easily apply the software and hence represent the final deliverable of work package 1 of the FLOATECH project. In the following, each of the above-mentioned tasks is described in greater detail

Load calculations play a key role in determining the design loads of different wind turbine components. To obtain the aerodynamic loads for these calculations, the industry relies heavily on the Blade Element Momentum (BEM) theory. BEM methods use several engineering correction models to capture the aerodynamic phenomena present in Design Load Cases (DLCs) with turbulent wind. Because of this, BEM methods can overestimate aerodynamic loads under challenging conditions when compared to higher-order aerodynamic methods – such as the Lifting-Line Free Vortex Wake (LLFVW) method – leading to unnecessarily high design loads and component costs. In this paper, we give a quantitative answer to the question of load overestimation of a particular BEM implementation by comparing the results of aeroelastic load calculations done with the BEM-based OpenFAST code and the QBlade code, which uses a particular implementation of the LLFVW method. We compare extreme and fatigue load predictions from both codes using sixty-six 10 min load simulations of the Danish Technical University (DTU) 10 MW Reference Wind Turbine according to the IEC 61400-1 power production DLC group. Results from both codes show differences in fatigue and extreme load estimations for the considered sensors of the turbine. LLFVW simulations predict 9 % lower lifetime damage equivalent loads (DELs) for the out-of-plane blade root and the tower base fore–aft bending moments compared to BEM simulations. The results also show that lifetime DELs for the yaw-bearing tilt and yaw moments are 3 % and 4 % lower when calculated with the LLFVW code. An ultimate state analysis shows that extreme loads of the blade root out-of-plane bending moment predicted by the LLFVW simulations are 3 % lower than the moments predicted by BEM simulations. For the maximum tower base fore–aft bending moment, the LLFVW simulations predict an increase of 2 %. Further analysis reveals that there are two main contributors to these load differences. The first is the different way both codes treat the effect of the nonuniform wind field on the local blade aerodynamics. The second is the higher average aerodynamic torque in the LLFVW simulations. It influences the transition between operating modes of the controller and changes the aeroelastic behavior of the turbine, thus affecting the loads.

For the detailed validation and verification of the capabilities of QBlade Ocean (QB) in work package 2, a detailed definition of the models is needed. This document presents the three aero-hydro-elastic models that will be used for this validation. These include two models for experimental validation: the upscaled 10 MW SOFTWIND experimental turbine mounted on a spar floater and the upscaled 5 MW OC5 experimental turbine mounted on a semi-submersible floater. The third model – the DTU 10MW Reference Wind Turbine mounted on the Hexafloat floater – is used for numerical validation against the established commercial code DeepLines Wind™. This document includes the definition of each of the three models and the results of the preliminary tests performed to validate the model behaviour. A link to the database is provided where the full QBlade Ocean model definition will be available.

This document is a report accompanying the deliverable 2.1 of the FLOATECH project, funded under the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101007142. For the detailed validation and verification of the capabilities of QBlade Ocean (QB) in work package 2, a detailed definition of the models is needed. This document presents the three aero-hydro-elastic models that will be used for this validation. These include two models for experimental validation: the upscaled 10 MW SOFTWIND experimental turbine mounted on a spar floater and the upscaled 5 MW OC5 experimental turbine mounted on a semisubmersible floater. The third model – the DTU 10MW Reference Wind Turbine mounted on the Hexafloat floater – is used for numerical validation against the established commercial code DeepLines Wind™. This document includes the definition of each of the three models and the results of the preliminary tests performed to validate the model behaviour. A link to the database is provided where the full QBlade Ocean model definition will be available.

This paper presents the results of an advanced control strategy that employs active trailing edge flaps to reduce the fatigue loads of an experimental wind turbine. The strategy, called repetitive model predictive control, is a multiple-input multiple-output controller that aims at the alleviation of out-of-plane blade root bending moments. The strategy incorporates the control commands, output errors, and state deviation from the previous rotation. This way, the time lag in the strain sensor input due to the blade inertia is compensated. Additionally, a strategy to limit the computational costs is presented. The load alleviation performance is evaluated at different yaw cases and compared with different individual flap control strategies. The repetitive model predictive control is able to reduce the fatigue loads by up to 23% compared with the better performing individual flap control strategy. This improvement in load reduction is accompanied by an increase in flap travel of up to 7% compared with the individual flap control strategies.

Increasing the size of wind turbines has been one of the most effective ways to decrease the cost of wind energy. If this trend is to continue, we need to ensure that the design loads of wind turbine components do not increase disproportionately with the turbine size. One promising way to do this is by increasing the accuracy of the aeroelastic modeling of wind turbine simulations. As aeroelastic load calculations are a critical part in determining the design loads of the turbine, increasing the model accuracy leads to more detailed load predictions and less conservative safety factors that need to be applied to compensate for model uncertainty.nAnother promising way to obtain competitive design loads for larger wind turbines is through the use of advanced control strategies that aim at reducing the design-driving loads of the turbine components. These loads are varied by nature so a combination of different actuators and strategies is required to effectively reduce them. The present work contributes to this effort in two separate but complementing ways. On the one hand, it includes a study of advanced aerodynamic models in aeroelastic simulations and their quantitative effect on wind turbine loads. On the other hand, it presents a wind turbine controller that is capable not only of performing a complete set of design load calculations but also includes advanced control strategies that mitigate design-driving loads using the generator torque, the blade pitch actuators and active trailing edge flaps distributed along the blade span. This controller is used in separate studies to reduce design-driving fatigue and extreme loads on the turbine. This dissertation is based on three papers that study different ways to achieve a load reduction. The first paper presents the turbine controller in detail. It also presents its advanced load reduction capabilities using traditional pitch and torque actuators and studies the load reduction capabilities of the individual pitch control strategy using the more accurate lifting line free vortex wake aerodynamic model in aeroelastic calculations. The second paper uses the developed controller in a study that quantifies how using more accurate aerodynamic models in aeroelastic simulations affects the loads. It compares the extreme and fatigue loads of key turbine sensors in aeroelastic simulations that are performed with the widely used blade element momentum aerodynamic model with simulations that use the lifting line free vortex wake aerodynamic model. It not only quantifies the loading differences but also finds the reasons that lead to these differences. The third paper explores the potential of active trailing edge flaps in reducing the design-driving extreme loads and critical deflections of the wind turbine blade. It considers the trailing edge flap hinge moment as a robust and readily available sensor that can be used as an input for the controller strategy. The hinge moment, in combination with other sensors, is used in a model-based observer to estimate the local inflow conditions and allow a fast response of the flap actuators. This observer is then used as part of a novel control strategy to effectively lower the extreme blade root loads and critical tip deflections. Each of the papers studies one aspect where load reduction can be obtained for larger wind turbines. This dissertation also includes suggestions for further developing and improving the respective aspects. Including them all in the design process of the next generation of wind turbines is a promising way of making this source of energy even more cost-competitive and its use more widespread. Die Vergrößerung von Windturbinen ist einer der effektivsten Wege die Stromgestehungskosten von Windenergie zu verringern. Um diesen Trend zu erhalten muss gewährleistet werden, dass die designtreibenden Lasten der Turbinenkomponenten nicht überproportional mit der Turbinengröße steigen. Eine versprechende Methode um dies zu erlangen ist die Verbesserung der aeroelastischen Modellierung in Windturbinensimulationen. Da aeroelastische Lastrechnungen eine kritische Rolle beim Design von Windturbinenkomponenten spielen, führt eine Verbesserung der Modellierung zu genaueren Designlasten und weniger konservativen Sicherheitsfaktoren bei den Lasten. Eine andere versprechende Methode um die Designlasten von großen Windturbinen zu verringern ist die Anwendung von fortgeschrittenen lastreduzierenden Regelungsstrategien. Unterschiedliche Lasten beeinflussen die Turbinenkomponenten anders und deshalb müssen auch verschiedene Aktuatoren in Betracht gezogen werden, um die desingtreibenden Lasten mehrerer Komponenten zu reduzieren. Diese Dissertation trägt zu diesem Thema in zwei separaten aber sich ergänzenden Themenbereiche bei. Einerseits beinhaltet die Arbeit eine Studie zu fortgeschrittenen aerodynamischen Modellen und deren quantitativen Effekt auf die Turbinenlasten. Andererseits präsentiert die Arbeit einen Windturbinenregler, der komplette Lastberechnungen durchführen kann und über fortgeschrittene lastreduzierende Regelungsstrategien verfügt. Diese Strategien nutzen verschiedene Aktuatoren wie Generator, Pitchaktuatoren und aktive Hinterkantenklappen und werden in unterschiedlichen Studien für die Verringerung von designtreibenden Extrem- und Ermüdungslasten verwendet. Die Arbeit basiert auf drei Veröffentlichungen die verschiedene Wege zur Lastreduzierung untersuchen. Die erste Veröffentlichung beschreibt den Windturbinenregler im Detail. Die Veröffentlichung beschreibt auch die fortgeschrittenen Lastreduktionsstrategien des entwickelten Reglers, welche auf traditionellen Aktuatoren wie die Pitchaktuatoren und dem Generatormoment beruhen. Die Lastreduktionsfähigkeit der Individual Pitch Control Strategie wird in aeroelastischen Simulationen untersucht, die das fortgeschrittene aerodynamische Modell Lifting Line Free Vortex Wake nutzen. Die zweite Veröffentlichung verwendet den Regler in einer Studie, die die Lasteffekte von fortgeschrittenen aerodynamischen Methoden in aeroelastischen Simulationen untersucht. Die Studie vergleicht Extrem- und Ermüdungslasten von wichtigen Turbinensensoren, die in aeroelastischen Simulationen mit zwei verschieden aerodynamischen Methoden berechnet worden sind. Die erste Methode ist die verbreitete Blade Element Momentum Methode. Die zweite Methode ist die fortgeschrittene Lifting Line Free Vortex Wake Methode. Die Studie quantifiziert nicht nur die Lastunterschiede sondern findet auch die Ursachen dieser Unterschiede. Die dritte Veröffentlichung untersucht das Potential von aktiven Hinterkantenklappen um designtreibende Extremlasten und kritische Durchbiegungen vom Rotorblatt zu reduzieren. Sie betrachtet das Klappengelenk-Moment als ein möglicher Regler-Sensor, der robust und bereits im Klappensystem vorhanden ist. In der Veröffentlichung wird das Klappengelenk-Moment und andere Sensoren für einen modellbasierten Beobachter genutzt, der die aerodynamischen Zustände an der Blattsektion schätzen kann. Dies ermöglicht eine schnelle Reaktion des Klappenreglers. Der Beobachter wird als Teil einer neuen Klappenstrategie verwendet, welche die Extremlasten und kritische Durchbiegung vom Rotorblatt effektiv reduziert. Die Veröffentlichungen untersuchen jeweils ein möglicher Lastreduktionsaspekt für größere Windturbinen. Diese Dissertation enthält Vorschläge, wie man diese einzelnen Aspekte verbessern kann. Alle Aspekte im Turbinen-Designprozess zu verwenden ist eine versprechende Option um die Kosten der Windenergie weiter zu reduzieren und die Nutzung dieser Technologie zu verbreiten.