This report describes a three-bladed, upwind, variable-speed, variable blade-pitch-to-feather-controlled multimegawatt wind turbine model developed by NREL to support concept studies aimed at assessing offshore wind technology.

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Definition of a 5-MW Reference Wind Turbine for Offshore System Development

Simulation and the monte carlo method

FAST User's Guide

This paper presents a comprehensive study on the state-of-the-art and emerging wind energy technologies from the electrical engineering perspective. In an attempt to decrease cost of energy, increase the wind energy conversion efficiency, reliability, power density, and comply with the stringent grid codes, the electric generators and power electronic converters have emerged in a rigorous manner. From the market based survey, the most successful generator-converter configurations are addressed along with few promising topologies available in the literature. The back-to-back connected converters, passive generator-side converters, converters for multiphase generators, and converters without intermediate dc-link are investigated for high-power wind energy conversion systems (WECS), and presented in low and medium voltage category. The onshore and offshore wind farm configurations are analyzed with respect to the series/parallel connection of wind turbine ac/dc output terminals, and high voltage ac/dc transmission. The fault-ride through compliance methods used in the induction and synchronous generator based WECS are also discussed. The past, present and future trends in megawatt WECS are reviewed in terms of mechanical and electrical technologies, integration to power systems, and control theory. The important survey results, and technical merits and demerits of various WECS electrical systems are summarized by tables. The list of current and future wind turbines are also provided along with technical details.

High-Power Wind Energy Conversion Systems: State-of-the-Art and Emerging Technologies

This report describes the development, verification, and application of a comprehensive simulation tool for modeling coupled dynamic responses of offshore floating wind turbines.

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Dynamics Modeling and Loads Analysis of an Offshore Floating Wind Turbine

This report presents the work done to develop generator and gearbox models in the Matrix Laboratory (MATLAB) environment and couple them to the National Renewable Energy Laboratory's Fatigue, Aerodynamics, Structures, and Turbulence (FAST) program. The goal of this project was to interface the superior aerodynamic and mechanical models of FAST to the excellent electrical generator models found in various Simulink libraries and applications. The scope was limited to Type 1, Type 2, and Type 3 generators and fairly basic gear-train models. Future work will include models of Type 4 generators and more-advanced gear-train models with increased degrees of freedom. As described in this study, implementation of the developed drivetrain model enables the software tool to be used in many ways. Several case studies are presented as examples of the many types of studies that can be performed using this tool.

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Simulation for Wind Turbine Generators -- With FAST and MATLAB-Simulink Modules

This paper studies the influence of mooring line dynamics on the response of a coupled floating offshore wind turbine against an equivalent uncoupled model. The semisubmersible modeled in this paper is based on a design developed by the DeepCwind program and uses the National Renewable Energy Laboratory’s (NREL’s) 5megawatt (MW) baseline wind turbine to represent the tower, nacelle, and blade properties. The uncoupled model was formed using FAST, an open-source program that models the wind turbine aerodynamics, control, motion, tower/blade flexure, and wave forces, but with the mooring line forces treated using a quasi-static approximation. In contrast, the coupled model was enabled by pairing FAST with OrcaFlex. OrcaFlex replaces FAST’s wave force and quasi-static cable model with an equivalent subsea fluid-structure representation and a lumped-mass cable system to capture the mooring line dynamics. This analysis revealed that an uncoupled model using the quasi-static mooring approximation can underestimate peak mooring line loads versus a coupled model using a dynamic mooring line.

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Assessment of the Importance of Mooring Dynamics on the Global Response of the DeepCwind Floating Semisubmersible Offshore Wind Turbine

High-quality computer simulations are required when designing floating wind turbines because of the complex dynamic responses that are inherent with a high number of degrees of freedom and variable metocean conditions. In 2007, the FAST wind turbine simulation tool, developed and maintained by the U.S. Department of Energy's (DOE's) National Renewable Energy Laboratory (NREL), was expanded to include capabilities that are suitable for modeling floating offshore wind turbines. In an effort to validate FAST and other offshore wind energy modeling tools, DOE funded the DeepCwind project that tested three prototype floating wind turbines at 1/50th scale in a wave basin, including a semisubmersible, a tension-leg platform, and a spar buoy. This paper describes the use of the results of the spar wave basin tests to calibrate and validate the FAST offshore floating simulation tool, and presents some initial results of simulated dynamic responses of the spar to several combinations of wind and sea states. Wave basin tests with the spar attached to a scale model of the NREL 5-megawatt reference wind turbine were performed at the Maritime Research Institute Netherlands under the DeepCwind project. This project included free-decay tests, tests with steady or turbulent wind and still water (both periodic and irregular waves with no wind), and combined wind/wave tests. The resulting data from the 1/50th model was scaled using Froude scaling to full size and used to calibrate and validate a full-size simulated model in FAST. Results of the model calibration and validation include successes, subtleties, and limitations of both wave basin testing and FAST modeling capabilities.

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Calibration and validation of a spar-type floating offshore wind turbine model using the FAST dynamic simulation tool

With the intent of improving simulation tools, a 1/50th-scale floating wind turbine atop a TLP was designed based on Froude scaling by the University of Maine under the DeepCwind Consortium. This platform was extensively tested in a wave basin at MARIN to provide data to calibrate and validate a full-scale simulation model. The data gathered include measurements from static load tests and free-decay tests, as well as a suite of tests with wind and wave forcing. A full-scale FAST model of the turbine-TLP system was created for comparison to the results of the tests. Analysis was conducted to validate FAST for modeling the dynamics of this floating system through comparison of FAST simulation results to wave tank measurements. First, a full-scale FAST model of the as-tested scaled configuration of the system was constructed, and this model was then calibrated through comparison to the static load, free-decay, regular wave only, and wind-only tests. Next, the calibrated FAST model was compared to the combined wind and wave tests to validate the coupled hydrodynamic and aerodynamic predictive performance. Limitations of both FAST and the data gathered from the tests are discussed.

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Jason Jonkman

Papers

Simulation for Wind Turbine Generators -- With FAST and MATLAB-Simulink Modules

Assessment of the Importance of Mooring Dynamics on the Global Response of the DeepCwind Floating Semisubmersible Offshore Wind Turbine

Calibration and validation of a spar-type floating offshore wind turbine model using the FAST dynamic simulation tool

Calibration and Validation of a Fast Floating Wind Turbine Model of the Deepcwind Scaled Tension-Leg Platform

Renewable Energy Sources and Climate Change Mitigation: Wind Energy