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.

/pdf/definition-of-a-5-mw-reference-wind-turbine-for-offshore-1we0gw6e7j.pdf

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.

/pdf/dynamics-modeling-and-loads-analysis-of-an-offshore-floating-1vpwpvvxfj.pdf

Dynamics Modeling and Loads Analysis of an Offshore Floating Wind Turbine

In this paper we propose and examine numerical algorithms for coupling time-dependent multi-physics modules relevant to computer-aided engineering (CAE) of wind turbines. In particular, we examine algorithms for coupling modules where spatial grids are nonmatching at interfaces and module solutions are time advanced with different time increments and different time integrators. The new mesh-mapping algorithm supports mapping between spatial meshes that are highly disparate. Sharing of data between modules is accomplished with a predictor-corrector approach, which allows for either implicit or explicit time integration within each module. Algorithms are presented in a general framework, but are applied to simple problems that are representative of the systems found in a wholeturbine analysis. Numerical experiments are used to explore the stability, accuracy, and efficiency of the proposed algorithms. This work is motivated by an in-progress major revision of FAST, the National Renewable Energy Laboratory’s (NREL’s) premier aero-elastic CAE simulation tool. The algorithms described here will greatly increase the flexibility and efficiency of FAST.

/pdf/fast-modular-wind-turbine-cae-tool-nonmatching-spatial-and-4nowkwjsvc.pdf

FAST Modular Wind Turbine CAE Tool: Nonmatching Spatial and Temporal Meshes

. The main objective of the presented work is the validation of the simulation tool FAST.Farm for the calculation of power and structural loads in
single wake situations; the basis for the validation is the measurement database of the operating offshore wind farm alpha ventus. The approach is
described in detail and covers the calibration of the aeroelastic turbine model, transfer of environmental conditions to simulations, and comparison
between simulations and adequately filtered measurements. It is shown that FAST.Farm accurately predicts power and structural load distributions
over wind direction with discrepancies of less than 10 % for most of the cases compared to the measurements. Additionally, the frequency
response of the structure is investigated, and it is calculated by FAST.Farm in good agreement with the measurements. In general, the calculation of
fatigue loads is improved with a wake-added turbulence model added to FAST.Farm in the course of this study.

/pdf/fast-farm-load-validation-for-single-wake-situations-at-5gbynty1ky.pdf

FAST.Farm load validation for single wake situations at alpha ventus

Since 1999, the International Electrotechnical Commission (IEC) Maintenance Team 2 (MT2) has been working on a revision of the IEC 61400-2 standard on the safety, quality, integrity, and design requirements of small wind turbines (SWTs). During this effort, a study was conducted to evaluate the quality of the structural design criteria specified by the original 2 standard. Test measurements and aeroelastic predictions of loads were gathered for a collection of SWTs and evaluated against the simplified load models and load cases specified in the standard. The collection of turbines included variations in rotor size, blade number, rotor location (upwind/downwind), hub type (rigid/teetered), yaw mechanism (free/active), and others. In general, the comparison of load measurements and model predictions exemplified the inaccuracy of the design load levels in the original -2 standard and suggested methods of improvement. Revisions being made to the standard include enhanced load models, new load cases, and improved safety factors. This work should culminate in a revised IEC 61400-2 standard that has a higher degree of applicability and dependability than the original.

/pdf/investigation-of-the-iec-safety-standard-for-small-wind-5160gr7axa.pdf

Investigation of the IEC Safety Standard for Small Wind Turbine Design Through Modeling and Testing: Preprint

https://iopscience.iop.org/article/10.1088/1742-6596/1618/6/062061/pdf

Validation of FAST.Farm Against Full-Scale Turbine SCADA Data for a Small Wind Farm

The wind engineering community relies on multiphysics engineering software to run nonlinear time-domain simulations, e.g., for design standards-based loads analysis. Although most physics involved in wind energy are nonlinear, linearization of the underlying nonlinear system equations is often advantageous to understand the system properties and exploit well-established methods and tools for analyzing linear systems. Previous work in this area has focused on the development of the new linearization functionality of the open-source engineering tool OpenFAST for floating offshore wind turbines, as well as the concepts and mathematical background needed to understand and apply it correctly. This paper focuses on the verification of this new linearization functionality, which is carried out by comparing results to previous stable versions of FAST. A nonlinear time-domain simulation for a floating offshore platform is also compared to the time-domain response of the linearized state-space model. The linearized results show good alignment between OpenFAST and previous versions of FAST, as well as with the time-domain simulations, thereby showing the accuracy of the new features in OpenFAST.

Jason Jonkman

Papers

FAST Modular Wind Turbine CAE Tool: Nonmatching Spatial and Temporal Meshes

FAST.Farm load validation for single wake situations at alpha ventus

Investigation of the IEC Safety Standard for Small Wind Turbine Design Through Modeling and Testing: Preprint

Validation of FAST.Farm Against Full-Scale Turbine SCADA Data for a Small Wind Farm

Verification of Floating Offshore Wind Linearization Functionality in OpenFAST