Actuator Saturation Control of Floating Wind Turbines

2012 ◽  
Author(s):  
Roberto Ramos
Keyword(s):  
Wind Turbine ◽  
Actuator Saturation ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Rigid Body Model ◽  
Integral Controller ◽  
Proportional Integral Controller ◽  
Saturation Effects ◽  
Wave Induced ◽  
Blade Element

A state feedback aerodynamic controller is proposed for the stabilization and reduction of platform/tower pitch vibrations of a spar-type floating wind turbine, considering blade pitch saturation effects. The controller is synthesized from a linearized rigid body model developed for a NREL 5-MW offshore wind turbine operating at the above rated condition (region 3). Wind turbulence and wave induced loads are obtained from the blade element momentum (BEM) aerodynamic theory and Morison’s equation, respectively. The simulation results show that the proposed nonlinear control system yields significant vibration reduction in comparison to a proportional-integral controller.

Simulation of an Offshore Wind Turbine Using a Weakly-Compressible CFD Solver Coupled With a Blade Element Turbine Model

2019 ◽  
Author(s):  
Baptiste Elie ◽  
Guillaume Oger ◽  
David Le Touzé
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Simulation Tool ◽  
Weakly Compressible ◽  
Element Simulation ◽  
Development And Validation ◽  
Elastic Modules ◽  
Turbine Model ◽  
Blade Element

Abstract The present study addresses the first steps of development and validation of a coupled CFD-BE (Blade Element) simulation tool dedicated to offshore wind turbine farm modelling. The CFD part is performed using a weakly-compressible solver (WCCH). The turbine is taken into account using FAST (from NREL) and its effects are imposed into the fluid domain through an actuator line model. The first part of this paper is dedicated to the presentation of the WCCH solver and its coupling with the aero-elastic modules from FAST. In a second part, for validation purposes, comparisons between FAST and the WCCH-FAST coupling are presented and discussed. Finally, a discussion on the performances, advantages and limitations of the formulation proposed is provided.

scholarly journals Modeling the TetraSpar Floating Offshore Wind Turbine Foundation as a Flexible Structure in OrcaFlex and OpenFAST

Energies ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7866
Author(s):  
Jonas Bjerg Thomsen ◽  
Roger Bergua ◽  
Jason Jonkman ◽  
Amy Robertson ◽  
Nicole Mendoza ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Entire Body ◽  
Floating Offshore Wind Turbine ◽  
Modeling Approaches ◽  
Rigid Body Model ◽  
Six Degree Of Freedom ◽  
Turbine Design ◽  
Floating Platforms

Floating offshore wind turbine technology has seen an increasing and continuous development in recent years. When designing the floating platforms, both experimental and numerical tools are applied, with the latter often using time-domain solvers based on hydro-load estimation from a Morison approach or a boundary element method. Commercial software packages such as OrcaFlex, or open-source software such as OpenFAST, are often used where the floater is modeled as a rigid six degree-of-freedom body with loads applied at the center of gravity. However, for final structural design, it is necessary to have information on the distribution of loads over the entire body and to know local internal loads in each component. This paper uses the TetraSpar floating offshore wind turbine design as a case study to examine new modeling approaches in OrcaFlex and OpenFAST that provide this information. The study proves the possibility of applying the approach and the extraction of internal loads, while also presenting an initial code-to-code verification between OrcaFlex and OpenFAST. As can be expected, comparing the flexible model to a rigid-body model proves how motion and loads are affected by the flexibility of the structure. OrcaFlex and OpenFAST generally agree, but there are some differences in results due to different modeling approaches. Since no experimental data are available in the study, this paper only forms a baseline for future studies but still proves and describes the possibilities of the approach and codes.

Modelling the Aerodynamics of a Floating Wind Turbine Model Using a CFD-Based Actuator Disc Method

2019 ◽  
Author(s):  
Ryan Bezzina ◽  
Tonio Sant ◽  
Daniel Micallef
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Speed Ratio ◽  
Offshore Wind Turbine ◽  
Floating Platform ◽  
Blade Element Theory ◽  
Floating Wind Turbine ◽  
Actuator Disc ◽  
Turbine Wake ◽  
Blade Element

Abstract Significant research in the field of Floating Offshore Wind Turbine (FOWT) rotor aerodynamics has been documented in literature, including validated aerodynamic models based on Blade Element Momentum (BEM) and vortex methods, amongst others. However, the effects of platform induced motions on the turbine wake development downstream of the rotor plane or any research related to such areas is rather limited. The aims of this paper are two-fold. Initially, results from a CFD-based Actuator Disc (AD) code for a fixed (non-surging) rotor are compared with those obtained from a Blade Element Momentum (BEM) theory, as well as previously conducted experimental work. Furthermore, the paper also emphasises the effect of tip speed ratio (TSR) on the rotor efficiency. This is followed by the analysis of floating wind turbines specifically in relation to surge displacement, through an AD technique implemented in CFD software, ANSYS Fluent®. The approach couples the Blade Element Theory (BET) for estimating rotating blade loads with a Navier Stokes solver to simulate the turbine wake. With regards to the floating wind turbine cases, the code was slightly altered such that BET was done in a transient manner i.e. following sinusoidal behaviour of waves. The AD simulations were performed for several conditions of TSRs and surge frequencies, at a constant amplitude. Similar to the fixed rotor analysis, significant parameters including thrust and power coefficients, amongst others, were studied against time and surge position. The floating platform data extracted from the AD approach was compared to the non-surging turbine data obtained, to display platform motion effects clearly. Data from hot wire near wake measurements and other simulation methods were also consulted.

Multi-Fidelity Aerodynamic Modeling of a Floating Offshore Wind Turbine Rotor

2020 ◽  
Author(s):  
Kai Zhang ◽  
Onur Bilgen
Keyword(s):  
Wind Turbine ◽  
Turbine Rotor ◽  
Modeling Method ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Blade Element Theory ◽  
Momentum Theory ◽  
Element Theory ◽  
Wind Turbine Rotor ◽  
Blade Element

Abstract This paper presents a comparison of low- and mid-fidelity aerodynamic modelling of floating offshore wind turbine rotors. The low-fidelity approach employs the conventional Blade Element Momentum theory implemented in AeroDyn of OpenFAST. This model ignores the aerodynamic interactions between different blade elements, and the forces on the blade are determined from the balance between momentum theory and blade element theory. With this method, it is possible to calculate the aerodynamic performance for different settings with low computational cost. For the mid-fidelity approach, the Actuator Line Modeling method implemented in turbinesFoam (an OpenFOAM library) is used. This method is built upon a combination of the blade element theory for modeling the blades, and a Navier-Stokes description of the wake flow field. Thus, it can capture the wake dynamics without resolving the detailed flows near the blades. The aerodynamic performance of the DTU 10 MW reference wind turbine rotor is studied using the two methods. The effects of wind speed, tip speed ratio, and blade pitch angles are assessed. Good agreement is observed between the two methods at low tip speed ratios, while the Actuator Line Modeling method predicts slightly higher power coefficients at high tip speed ratios. In addition, the ability of the Actuator Line Modeling Method to capture the wake dynamics of the rotor in an unsteady inflow is demonstrated. In the future, the multi-fidelity aerodynamic modules developed in this paper will be integrated with the hydro-kinematics and hydro-dynamics of a floating platform and a mooring system, to achieve a fully coupled framework for the analysis and design optimization of floating offshore wind turbines.

Optimal Vibration Control of Floating Wind Turbines in the Presence of Nonlinearities

2013 ◽  
Author(s):  
Roberto Ramos
Keyword(s):  
Wind Speed ◽  
Wind Turbines ◽  
Actuator Saturation ◽  
Rigid Body Dynamic ◽  
Speed Regulation ◽  
Control Objective ◽  
Integral Controller ◽  
Proportional Integral Controller ◽  
Persistent Disturbances ◽  
Wave Induced

This paper investigates the effects of nonlinearities on the design of a constrained optimal controller for spar-type floating wind turbines. The considered nonlinearities are due to wind speed variation and actuator saturation. The collective blade pitch actuator, usually employed for aerodynamic rotor speed regulation, is adopted for the mitigation of platform pitch vibrations as well. The wind speed effects and the control law are obtained from a linearized rigid-body dynamic model, taking into account persistent disturbances related to wind turbulence and wave induced loads, which are estimated using the Blade Element Momentum aerodynamic theory and Morison equation, respectively. A performance analysis is carried out for several operating points in the above rated wind speed region, considering the reduction of the platform pitch motion as the main control objective. The simulation results show that the designed fixed-gain multivariable controller can yield significant vibration reduction in comparison with a baseline gain-scheduled proportional-integral controller in the presence of the considered nonlinearities.

scholarly journals Dynamic Response of a Conceptual Designed Articulated Offshore Wind Turbine

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Pei Zhang ◽  
Yan Li ◽  
Jiayang Gu ◽  
Tianchang Yin ◽  
Zhiqiang Hu ◽  
...  
Keyword(s):  
Dynamic Response ◽  
Wind Turbine ◽  
Three Dimensional ◽  
Wind Pressure ◽  
Offshore Wind ◽  
Offshore Wind Turbine ◽  
Aerodynamic Load ◽  
Offshore Area ◽  
Momentum Theory ◽  
Blade Element

Abstract Focusing on the 75 m depth offshore area, an articulated foundation is proposed for supporting National Renewable Energy Laboratory (NREL) 5 MW offshore wind turbine (OWT). Through the overall sensitivity check on hydrostatic performance, the main parameters are set to meet the requirements of stability and economy. An in-house code was programmed to simulate the dynamic response of the articulated offshore wind turbine (AOWT). The aerodynamic load on rotating blades and the wind pressure load on tower are calculated based on the blade element momentum theory and the empirical formula, respectively. The hydrodynamic load is simulated by the three-dimensional potential flow theory. The motions of foundation, the aerodynamic performance of the wind turbine, and the loads on the articulated joint are documented in different cases. According to the simulations, the articulated offshore wind turbine shows feasibility to work in the particular area.

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