scholarly journals On Tower Top Axial Acceleration and Drivetrain Responses in a Spar-Type Floating Wind Turbine

2017 ◽  
Author(s):  
Amir Rasekhi Nejad ◽  
Erin E. Bachynski ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Global Analysis ◽  
Correlation Study ◽  
Analysis Tool ◽  
Maximum Acceleration ◽  
Peak Period ◽  
Floating Wind Turbine ◽  
Axial Acceleration ◽  
Northern North Sea ◽  
Wave Induced

Common industrial practice for designing floating wind turbines is to set an operational limit for the tower-top axial acceleration, normally in the range of 0.2–0.3g, which is typically understood to be related to the safety of turbine components. This paper investigates the rationality of the tower-top acceleration limit by evaluating the correlation between acceleration and drivetrain responses. A 5 MW reference drivetrain is selected and modelled on a spar-type floating wind turbine in 320 m water depth. A range of environmental conditions are selected based on the long-term distribution of wind speed, significant wave height, and peak period from hindcast data for the Northern North Sea. For each condition, global analysis using an aero-hydro-servo-elastic tool is carried out for six one-hour realizations. The global analysis results provide useful information on their own — regarding the correlation between environmental condition and tower top acceleration, and correlation between tower top acceleration and other responses of interest — which are used as input in a decoupled analysis approach. The load effects and motions from the global analysis are applied on a detailed drivetrain model in a multi-body system (MBS) analysis tool. The local responses on bearings are then obtained from MBS analysis and post-processed for the correlation study. Although the maximum acceleration provides a good indication of the wave-induced loads, it is not seen to be a good predictor for significant fatigue damage on the main bearings in this case.

Effect of Axial Acceleration on Drivetrain Responses in a Spar-Type Floating Wind Turbine

2019 ◽  
Vol 141 (3) ◽  
Author(s):  
Amir R. Nejad ◽  
Erin E. Bachynski ◽  
Torgeir Moan
Keyword(s):  
Wind Turbine ◽  
Global Analysis ◽  
Correlation Study ◽  
Analysis Tool ◽  
Maximum Acceleration ◽  
Peak Period ◽  
Floating Wind Turbine ◽  
Axial Acceleration ◽  
Northern North Sea ◽  
Wave Induced

Common industrial practice for designing floating wind turbines is to set an operational limit for the tower-top axial acceleration, normally in the range of 0.2–0.3 g, which is typically understood to be related to the safety of turbine components. This paper investigates the rationality of the tower-top acceleration limit by evaluating the correlation between acceleration and drivetrain responses. A 5-MW reference drivetrain is selected and modeled on a spar-type floating wind turbine in 320 m water depth. A range of environmental conditions are selected based on the long-term distribution of wind speed, significant wave height, and peak period from hindcast data for the Northern North Sea. For each condition, global analysis using an aero-hydro-servo-elastic tool is carried out for six one-hour realizations. The global analysis results provide useful information on their own—regarding the correlation between environmental condition and tower top acceleration, and the correlation between tower top acceleration and other responses of interest—which are used as input in a decoupled analysis approach. The load effects and motions from the global analysis are applied on a detailed drivetrain model in a multibody system (MBS) analysis tool. The local responses on bearings are then obtained from MBS analysis and postprocessed for the correlation study. Although the maximum acceleration provides a good indication of the wave-induced loads, it is not seen to be a good predictor for significant fatigue damage on the main bearings in this case.

Global Analysis of a Floating Wind Turbine Using an Aero-Hydro-Elastic Model: Part 1—Code Development and Case Study

2011 ◽  
Author(s):  
Harald Ormberg ◽  
Elizabeth Passano ◽  
Neil Luxcey
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Global Analysis ◽  
Offshore Wind Turbine ◽  
System Response ◽  
Elastic Model ◽  
Analysis Tool ◽  
Time Step ◽  
Floating Wind Turbine ◽  
Study Results

This paper describes the extension of a well proven state-of-the-art simulation tool for coupled floating structures to accommodate offshore wind turbine applications, both floating and fixed. All structural parts, i.e. rotor blades, hub, nacelle, tower, vessel and mooring system, are included in the finite element model of the complete system. The aerodynamic formulation is based on the blade element momentum theory. A control algorithm is used for regulation of blade pitch angle and electrical torque. The system response is calculated by nonlinear time domain analysis. This approach ensures dynamic equilibrium every time step and gives a proper time domain interaction between the blade dynamics, the mooring dynamics and the tower motions. The developed computer code provides a tool for efficient analysis of motions, support forces and power generation potential, as influenced by waves, wind, and current. Some key results from simulations with wind and wave loading are presented in the paper. The results are compared with results obtained with a rigid blade model and quasi-static model of the anchor lines. The modelled wind turbine is the NREL offshore 5-MW baseline wind turbine, specifications of which are publicly available. In the accompanying paper, Global Analysis of a Floating Wind Turbine Using an Aero-Hydro-Elastic Numerical Model. Part 2: Benchmark Study, results from the new analysis tool are benchmarked against results from other analysis tools.

Impact of a Wind Turbine Blade Pitch Rate on a Floating Wind Turbine During an Emergency Shutdown Operation

2020 ◽  
Author(s):  
Pauline Louazel ◽  
Daewoong Son ◽  
Bingbin Yu
Keyword(s):  
Wind Turbine ◽  
Turbine Blades ◽  
Floating Platform ◽  
Floating Structure ◽  
Rapid Variation ◽  
Emergency Shutdown ◽  
Floating Wind Turbine ◽  
Time Period ◽  
Wave Induced ◽  
Loss Of Thrust

Abstract During the shutdown of a wind turbine, the turbine blades rotate from their typical operating angle to their typical idling angle (approximately 90 degrees) at a specific speed, called the blade pitch rate. This operation leads to rapid loss of thrust force on the turbine resulting in a corresponding heel response of the floating structure. This rapid variation of loads at the turbine also leads to large nacelle accelerations which are transferred to the bottom of the tower and consequently to the floating structure, making the turbine shutdowns, and specifically emergency shutdowns, of significance in the design and certification of the turbine, tower and floating structure. In case of an emergency shutdown (for instance due to a grid loss), the blades typically pitch from 0 degree to 90 degrees in approximately 20–35 seconds, whereas this time period can be more than 100 seconds in the case of a normal shutdown [6]. For fixed-bottom wind turbines, increasing the blade pitch rate leads to an increase of instantaneous loads at the nacelle and tower, leading to the emergency shutdown pitch rate being usually chosen to be as low as possible. In the case of a floating wind turbine, however, water/platform interaction effects such as wave induced damping on the floating platform, challenge this approach. Indeed, increasing the blade pitch rate can increase the effect of wave-induced damping on the floater and therefore reduce the loads on the overall structure. On the other hand, reducing the blade pitch rate during an emergency shutdown can reduce this damping effect and increase those loads, meaning that an optimal blade pitch rate for a fixed bottom turbine is not necessarily optimal for a floating wind turbine. This paper will examine the behavior of a floating offshore semi-submersible platform, the WindFloat, during turbine shutdown operations, with an emphasis on the blade pitch rate during an emergency shutdown.

Global Analysis of a Floating Wind Turbine Using an Aero-Hydro-Elastic Numerical Model: Part 2—Benchmark Study

2011 ◽  
Author(s):  
Neil Luxcey ◽  
Harald Ormberg ◽  
Elizabeth Passano
Keyword(s):  
Numerical Model ◽  
Wind Turbine ◽  
Global Analysis ◽  
Weather Conditions ◽  
Irregular Waves ◽  
Benchmark Study ◽  
Floating Wind Turbine ◽  
Calm Water ◽  
Internal Forces ◽  
System Power

This paper describes and presents the results of a benchmark study of a floating wind turbine numerical model that includes aero- and hydro-elasticity. The modelled wind turbine is the NREL offshore 5 MW baseline wind turbine whose specifications are publicly available. The first part of this paper demonstrates the importance of including aeroelasticity and hydroelasticity in the system. Power production, internal forces and motion amplitudes are compared to results from models using a rigid tower and rigid blades. Comparisons are performed for different weather conditions such as calm water, regular and irregular waves, constant and varying wind. The consequences of including elasticity in the different parts of the model are studied. The second part of the paper presents a benchmark study against the codes of the Offshore Code Comparison Collaboration. The floater motions, blade and tower deflection and power generation are presented and discussed.

Short and Long Term Extreme Reliability Analysis Applied to Floating Wind Turbine Design

2011 ◽  
Author(s):  
Timothe´e Perdrizet ◽  
Daniel Averbuch
Keyword(s):  
Wind Turbine ◽  
International Energy Agency ◽  
Energy Agency ◽  
Floating Wind Turbine ◽  
Extreme Response ◽  
Short And Long Term ◽  
Turbine Design ◽  
Wave Induced

This paper describes and exemplifies an efficient methodology to assess, jointly and in a single calculation, the short and long terms failure probabilities associated to the extreme response of a floating wind turbine, subjected to wind and wave induced loads. This method is applied to the realistic case study OC3-Hywind used in phase IV of the IEA (International Energy Agency) Annex XXIII Offshore Code Comparison Collaboration. The key point of the procedure, derived from the outcrossing approach, consists in computing the mean of the outcrossing rate of the floating wind turbine response in the failure domain over both the short term variables and the ergodic variables defining long term parameters.

scholarly journals Proposal of a Novel Semi-Submersible Floating Wind Turbine Platform Composed of Inclined Columns and Multi-Segmented Mooring Lines

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1809 ◽  
Author(s):  
Zhenqing Liu ◽  
Qingsong Zhou ◽  
Yuangang Tu ◽  
Wei Wang ◽  
Xugang Hua
Keyword(s):  
Wind Turbine ◽  
Offshore Wind ◽  
Mooring Line ◽  
Offshore Wind Turbine ◽  
Analysis Tool ◽  
Mooring Lines ◽  
Offshore Area ◽  
Floating Wind Turbine ◽  
Inclined Angle ◽  
Heave Motion

The semi-submersible floating offshore wind turbine has been studied in detail due to its good stability. However, the occurrence of typhoons are very frequent in China’s offshore area, putting forward a higher requirement for the stability of the floating wind turbine system. By changing the connection mode of the mooring line as well as the structural form of the platform based on the original OC4 model, two groups of models were examined by an in-house developed code named as the Analysis Tool of Floating Wind Turbine (AFWT). The influence of the arrangement of the mooring lines and the inclination angle of the upper columns on the motion response were clarified. It was found that the surge motion of the platform would be obviously decreased by decreasing the length of the upper segments of the mooring lines, while the heave motion of the platform would be significantly decreased as increasing the inclined angle of the columns. Therefore, a new model integrating the optimized multi-segmented mooring lines and the optimized inclined columns was proposed. The examinations showed that compared with the response motions of the original OC4 semi-submersible model, the proposed model could reduce both the surge and heave motions of the platform effectively.

Model Test Correlation Study for a Floating Wind Turbine on a Tension Leg Platform

2013 ◽  
Author(s):  
Bonjun Koo ◽  
Andrew J. Goupee ◽  
Kostas Lambrakos ◽  
Ho-Joon Lim
Keyword(s):  
Wind Turbine ◽  
Rotor Dynamics ◽  
Correlation Study ◽  
Mooring System ◽  
National Renewable Energy Laboratory ◽  
Floating Platform ◽  
Floating Wind Turbine ◽  
Integrated Program ◽  
Turbine Model ◽  
Test Correlation

The challenges related to floating wind turbine analysis simulations relate to the modeling of the flexible turbine tower dynamics, the rotor dynamics, and the floating platform dynamics. In order to simulate the interactions between the wind turbine and the floating platform, two existing numerical codes, FAST [1], developed by the National Renewable Energy Laboratory (NREL), and MLTSIM, a Technip proprietary software, were integrated into one code, MLTSIM-FAST. In this integrated program, the turbine tower and rotor dynamics are simulated by the subroutines of FAST, and the hydrodynamic loads and mooring system dynamics are simulated by the subroutines of MLTSIM. This paper presents validation of the MLTSIM-FAST code on the basis of data from the DeepCwind floating wind turbine model tests [2] and [3]. For the present MLTSIM-FAST validation study, the TLP floating wind turbine, which showed the strongest interactions between the wind turbine and the floating platform among the three platforms TLP, SEMI, and SPAR tested, is selected. The validation results are given on the basis of full scale measured and simulated motions and loads.

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