Variability of extreme flap loads during turbine operation

Energy Technology Data Exchange (ETDEWEB)

Ronold, K O [Det Norske Veritas, Hoevik (Norway); Larsen, G C [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

1999-03-01

The variability of extreme flap loads is of utmost importance for design of wind-turbine rotor blades. The flap loads of interest consist of the flap-wise bendin moment response at the blade root whose variability in the short-term, for a given wind climate, can be represented by a stationary process. A model for the short-term bending moment process is presented, and the distribution of its associated maxima is derived. A model for the wind climate is given in terms of the probability distributions for the 10-minute mean wind speed and the standard deviation of the arbitrary wind speed. This is used to establish the distribution of the largest flap-wise bending moment in a specific reference period, and it is outlined how a characteristic bending moment for use in design can be extracted from this distribution. The application of the presented distribution models is demonstrated by a numerical example for a site-specific wind turbine. (au)

Probabilistic analysis of extreme wind events

Energy Technology Data Exchange (ETDEWEB)

Chaviaropoulos, P.K. [Center for Renewable Energy Sources (CRES), Pikermi Attikis (Greece)

1997-12-31

A vital task in wind engineering and meterology is to understand, measure, analyse and forecast extreme wind conditions, due to their significant effects on human activities and installations like buildings, bridges or wind turbines. The latest version of the IEC standard (1996) pays particular attention to the extreme wind events that have to be taken into account when designing or certifying a wind generator. Actually, the extreme wind events within a 50 year period are those which determine the ``static`` design of most of the wind turbine components. The extremes which are important for the safety of wind generators are those associated with the so-called ``survival wind speed``, the extreme operating gusts and the extreme wind direction changes. A probabilistic approach for the analysis of these events is proposed in this paper. Emphasis is put on establishing the relation between extreme values and physically meaningful ``site calibration`` parameters, like probability distribution of the annual wind speed, turbulence intensity and power spectra properties. (Author)

Danish extreme wind atlas: Background and methods for a WAsP engineering option

Energy Technology Data Exchange (ETDEWEB)

Rathmann, O; Kristensen, L; Mann, J [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark); Hansen, S O [Svend Ole Hansen ApS, Copenhagen (Denmark)

1999-03-01

Extreme wind statistics is necessary design information when establishing wind farms and erecting bridges, buildings and other structures in the open air. Normal mean wind statistics in terms of directional and speed distribution may be estimated by wind atlas methods and are used to estimate e.g. annual energy output for wind turbines. It is the purpose of the present work to extend the wind atlas method to also include the local extreme wind statistics so that an extreme value as e.g. the 50-year wind can be estimated at locations of interest. Together with turbulence estimates such information is important regarding the necessary strength of wind turbines or structures to withstand high wind loads. In the `WAsP Engineering` computer program a flow model, which includes a model for the dynamic roughness of water surfaces, is used to realise such an extended wind atlas method. With basis in an extended wind atlas, also containing extreme wind statistics, this allows the program to estimate extreme winds in addition to mean winds and turbulence intensities at specified positions and heights. (au) EFP-97. 15 refs.

A risk analysis for natural-draught cooling towers under wind load

International Nuclear Information System (INIS)

Niemann, H.J.

1977-01-01

A satisfactory safety level of natural-draught cooling towers is usually reached by assuming an extreme wind load, for which the probability of being exceeded is very low. Taking into account the dispersion of strength, the relevant extreme wind velocity for the limiting carrying capacity is calculated for a desired probability of failure. Compared with the method of partial safety coefficients, the reliability can be calculated more exactly in this way, even though the probability distribution of the extreme wind velocity must be extrapolated from limited observations. (orig.) [de

Extreme load alleviation using industrial implementation of active trailing edge flaps in a full design load basis

OpenAIRE

Barlas, Athanasios; Pettas, Vasilis; Gertz, Drew Patrick; Aagaard Madsen , Helge

2016-01-01

The application of active trailing edge flaps in an industrial oriented implementation is evaluated in terms of capability of alleviating design extreme loads. A flap system with basic control functionality is implemented and tested in a realistic full Design Load Basis (DLB) for the DTU 10MW Reference Wind Turbine (RWT) model and for an upscaled rotor version in DTU's aeroelastic code HAWC2. The flap system implementation shows considerable potential in reducing extreme loads in components o...

Framing Failures in Wood-Frame Hip Roofs under Extreme Wind Loads

Directory of Open Access Journals (Sweden)

Sarah A. Stevenson

2018-02-01

Full Text Available Wood-frame residential roof failures are among the most common and expensive types of wind damage. Hip roofs are commonly understood to be more resilient during extreme wind in relation to gable roofs. However, inspection of damage survey data from recent tornadoes has revealed a previously unstudied failure mode in which hip roofs suffer partial failure of the framing structure. In the current study, evidence of partial framing failures and statistics of their occurrence are explored and discussed, while the common roof design and construction practice are reviewed. Two-dimensional finite element models are developed to estimate the element-level load effects on hip roof trusses and stick-frame components. The likelihood of failure in each member is defined based on relative demand-to-capacity ratios. Trussed and stick-frame structures are compared to assess the relative performance of the two types of construction. The present analyses verify the common understanding that toenailed roof-to-wall connections are likely to be the most vulnerable elements in the structure of a wood-frame hip roof. However, the results also indicate that certain framing members and connections display significant vulnerability under the same wind uplift, and the possibility of framing failure is not to be discounted. Furthermore, in the case where the roof-to-wall connection uses hurricane straps, certain framing members and joints become the likely points of failure initiation. The analysis results and damage survey observations are used to expand the understanding of wood-frame residential roof failures, as they relate to the Enhanced Fujita Scale and provide assessment of potential gaps in residential design codes.

Adaptive pitch control for load mitigation of wind turbines

Science.gov (United States)

Yuan, Yuan; Tang, J.

2015-04-01

In this research, model reference adaptive control is examined for the pitch control of wind turbines that may suffer from reduced life owing to extreme loads and fatigue when operated under a high wind speed. Specifically, we aim at making a trade-off between the maximum energy captured and the load induced. The adaptive controller is designed to track the optimal generator speed and at the same time to mitigate component loads under turbulent wind field and other uncertainties. The proposed algorithm is tested on the NREL offshore 5-MW baseline wind turbine, and its performance is compared with that those of the gain scheduled proportional integral (GSPI) control and the disturbance accommodating control (DAC). The results show that the blade root flapwise load can be reduced at a slight expense of optimal power output. The generator speed regulation under adaptive controller is better than DAC.

The Load Level of Modern Wind Turbines according to IEC 61400-1

International Nuclear Information System (INIS)

Freudenreich, K; Argyriadis, K

2007-01-01

The paper describes some effects on the load level of state-of-the art multi megawatt wind turbines introduced by the new edition of the standard IEC 61400-1:2005 W ind Turbines - Part 1: Design requirements . Compared to the previous edition, especially the extreme load determination has been modified by applying stochastic and statistical analyses. Within this paper the effect on the overall load level of wind turbines is demonstrated and occurring problems are discussed. Load simulations have been carried out for four state-of-the-art multi-megawatt wind turbines of different design concepts and from different manufacturers. The blade root bending moments and tip deflection have been determined by applying different extrapolation methods. Advantages and disadvantages of these methods and tail fittings for different load components and wind turbine technologies are discussed and interpreted. Further on, the application of the extreme turbulence model is demonstrated. The dependence of the load level on the turbulence intensity and control system, as well as the interaction with extrapolated loads is discussed and limitations outlined. The obtained load level is compared to the overall load level of the turbines according to the previous edition of the standard, IEC 61400-1:1999

Directional analysis of extreme winds under mixed climate conditions

CSIR Research Space (South Africa)

Kruger, A

2013-07-01

Full Text Available Directional statistics provide design engineers with the opportunity to realise considerable cost savings, but these are not yet provided for in the South African standard for wind loading. The development of the directional statistics of extreme...

Wind simulation for extreme and fatigue loads

Energy Technology Data Exchange (ETDEWEB)

Nielsen, M.; Larsen, G.C.; Mann, J.; Ott, S.; Hansen, K.S.; Pedersen, B.J.

2004-01-01

Measurements of atmospheric turbulence have been studied and found to deviate from a Gaussian process, in particular regarding the velocity increments over small time steps, where the tails of the pdf are exponential rather than Gaussian. Principles for extreme event counting and the occurrence of cascading events are presented. Empirical extreme statistics agree with Rices exceedence theory, when it is assumed that the velocity and its time derivative are independent. Prediction based on the assumption that the velocity is a Gaussian process underpredicts the rate of occurrence of extreme events by many orders of magnitude, mainly because the measured pdf is non-Gaussian. Methods for simulation of turbulent signals have been developed and their computational efficiency are considered. The methods are applicable for multiple processes with individual spectra and probability distributions. Non-Gaussian processes are simulated by the correlation-distortion method. Non-stationary processes are obtained by Bezier interpolation between a set of stationary simulations with identical random seeds. Simulation of systems with some signals available is enabled by conditional statistics. A versatile method for simulation of extreme events has been developed. This will generate gusts, velocity jumps, extreme velocity shears, and sudden changes of wind direction. Gusts may be prescribed with a specified ensemble average shape, and it is possible to detect the critical gust shape for a given construction. The problem is formulated as the variational problem of finding the most probable adjustment of a standard simulation of a stationary Gaussian process subject to relevant event conditions, which are formulated as linear combination of points in the realization. The method is generalized for multiple correlated series, multiple simultaneous conditions, and 3D fields of all velocity components. Generalization are presented for a single non-Gaussian process subject to relatively

Database on wind characteristics - Analyses of wind turbine design loads

DEFF Research Database (Denmark)

Larsen, Gunner Chr.; Hansen, K.S.

2004-01-01

the design load cases with relevance for to wind turbine structures. The present report constitutes thesecond part of the Annex XVII reporting. Both fatigue and extreme load aspects are dealt with, however, with the main emphasis on the latter. The work has been supported by The Ministry of Environment...... and Energy, Danish Energy Agency, The NetherlandsAgency for Energy and the Environment (NOVEM), The Norwegian Water Resources and Energy Administration (NVE), The Swedish National Energy Administration (STEM) and The Government of the United States of America....

Database on wind characteristics - Analyses of wind turbine design loads

Energy Technology Data Exchange (ETDEWEB)

Larsen, G.C.; Hansen, K.S.

2004-06-01

The main objective of IEA R and D Wind Annex XVII - Database on Wind Characteristics - has been to provide wind energy planners, designers and researchers, as well as the international wind engineering community in general, with a source of actual wind field data (time series and resource data) observed in a wide range of different wind climates and terrain types. Connected to an extension of the initial Annex period, the scope for the continuation was widened to include also support to the international wind turbine standardisation efforts.. The project partners are Sweden, Norway, U.S.A., The Netherlands and Denmark, with Denmark as the Operating Agent. The reporting of the continuation of Annex XVII falls in two separate parts. Part one accounts in details for the available data in the established database bank, and part two describes various data analyses performed with the overall purpose of improving the design load cases with relevance for to wind turbine structures. The present report constitutes the second part of the Annex XVII reporting. Both fatigue and extreme load aspects are dealt with, however, with the main emphasis on the latter. The work has been supported by The Ministry of Environment and Energy, Danish Energy Agency, The Netherlands Agency for Energy and the Environment (NOVEM), The Norwegian Water Resources and Energy Administration (NVE), The Swedish National Energy Administration (STEM) and The Government of the United States of America. (au)

Assessment of Gearbox Operational Loads and Reliability under High Mean Wind Speeds

DEFF Research Database (Denmark)

Dabrowski, Dariusz; Natarajan, Anand

2015-01-01

wind turbine that operates in storm conditions with mean wind speeds less than 30 m/s is presented. In the study, normal shut-downs of a wind turbine in storm conditions were investigated. The analysis were conducted for two storm control strategies and different wind conditions from an extreme...... operating gust, normal turbulence model and extreme turbulence model. In the paper, loads in the planetary gear are quantified as well as the torsional moments in the main shaft. On the basis of simulation results the annual probability of failure of the gearbox in a wind turbine with soft storm controller...... is calculated, and compared with the one had the gearbox working in a wind turbine operating with hard storm controller. In the study, it was found that normal shut-downs do not have a significant influence on the ultimate loads in the gearbox, since they are related mostly to the gusts occurring during...

On Wind Forces in the Forest-Edge Region During Extreme-Gust Passages and Their Implications for Damage Patterns

Science.gov (United States)

Gromke, Christof; Ruck, Bodo

2018-03-01

A damage pattern that is occasionally found after a period of strong winds shows an area of damaged trees inside a forest stand behind an intact stripe of trees directly at the windward edge. In an effort to understand the mechanism leading to this damage pattern, wind loading in the forest-edge region during passages of extreme gusts with different characteristics are investigated using a scaled forest model in the wind tunnel. The interaction of a transient extreme gust with the stationary atmospheric boundary layer (ABL) as a background flow at the forest edge leads to the formation of a vortex at the top of the canopy. This vortex intensifies when travelling downstream and subsequently deflects high-momentum air from above the canopy downwards resulting in increased wind loading on the tree crowns. Under such conditions, the decrease in wind loading in the streamwise direction can be relatively weak compared to stationary ABL approach flows. The resistance of trees with streamwise distance from the forest edge, however, is the result of adaptive growth to wind loading under stationary flow conditions and shows a rapid decline within two to three tree heights behind the windward edge. For some of the extreme gusts realized, an exceedance of the wind loading over the resistance of the trees is found at approximately three tree heights behind the forest edge, suggesting that the damage pattern described above can be caused by the interaction of a transient extreme gust with the stationary ABL flow.

Early warnings of extreme winds using the ECMWF Extreme Forecast Index

OpenAIRE

Petroliagis, Thomas I.; Pinson, Pierre

2014-01-01

The European FP7 SafeWind Project aims at developing research towards a European vision of wind power forecasting, which requires advanced meteorological support concerning extreme wind events. This study is focused mainly on early warnings of extreme winds in the early medium-range. Three synoptic stations (airports) of North Germany (Bremen, Hamburg and Hannover) were considered for the construction of time series of daily maximum wind speeds. All daily wind extremes were found to be linked...

Vertical Axis Wind Turbine Design Load Cases Investigation and Comparison with Horizontal Axis Wind Turbine

DEFF Research Database (Denmark)

Galinos, Christos; Larsen, Torben J.; Aagaard Madsen, Helge

2016-01-01

The paper studies the applicability of the IEC 61400-1 ed.3, 2005 International Standard of wind turbine minimum design requirements in the case of an onshore Darrieus VAWT and compares the results of basic Design Load Cases (DLCs) with those of a 3-bladed HAWT. The study is based on aeroelastic...... computations using the HAWC2 aero-servo-elastic code A 2-bladed 5 MW VAWT rotor is used based on a modified version of the DeepWind rotor For the HAWT simulations the NREL 3-bladed 5 MW reference wind turbine model is utilized Various DLCs are examined including normal power production, emergency shut down...... and parked situations, from cut-in to cut-out and extreme wind conditions. The ultimate and 1 Hz equivalent fatigue loads of the blade root and turbine base bottom are extracted and compared in order to give an insight of the load levels between the two concepts. According to the analysis the IEC 61400-1 ed...

Summary of international extreme load design requirements for nuclear power plant facilities

International Nuclear Information System (INIS)

Stevenson, J.D.

1978-01-01

An attempt is made to trace the development of extreme load criteria as it applies to earthquakes, extreme wind, high energy system rupture (LOCA), floods and other manmade and natural external hazards, from 1965 until the present, in the leading nuclear power nations throughout the world. (Author)

Monitoring of wind load and response for cable-supported bridges in Hong Kong

Science.gov (United States)

Wong, Kai-yuen; Chan, Wai-Yee K.; Man, King-Leung

2001-08-01

Structural health monitoring for the three cable-supported bridges located in the West of Hong Kong or the Tsing Ma Control Area has been carried out since the opening of these bridges to public traffic. The three cable-supported bridges are referred to as the Tsing Ma (suspension) Bridge, the Kap Shui Mun (cable-stayed) Bridge and the Ting Kau (cable-stayed) Bridge. The structural health monitoring works involved are classified as six monitoring categories, namely, wind load and response, temperature load and response, traffic load and response, geometrical configuration monitoring, strains and stresses/forces monitoring and global dynamic characteristics monitoring. As wind loads and responses had been a major concern in the design and construction stages, this paper therefore outlines the work of wind load and response monitoring on Tsing Ma, Kap Shui Mun and Ting Kau Bridges. The paper starts with a brief description of the sensory systems. The description includes the layout and performance requirements of sensory systems for wind load and responses monitoring. Typical results of wind load and response monitoring in graphical forms are then presented. These graphical forms include the plots of wind rose diagrams, wind incidences vs wind speeds, wind turbulence intensities, wind power spectra, gust wind factors, coefficient of terrain roughness, extreme wind analyses, deck deflections/rotations vs wind speeds, acceleration spectra, acceleration/displacement contours, and stress demand ratios. Finally conclusions on wind load and response monitoring on the three cable-supported bridges are drawn.

Investigation of potential extreme load reduction for a two-bladed upwind turbine with partial pitch

DEFF Research Database (Denmark)

Kim, Taeseong; Larsen, Torben J.; Yde, Anders

2015-01-01

This paper presents a wind turbine concept with an innovative design combining partial pitch with a two-bladed (PP-2B) turbine configuration. Special emphasis is on extreme load reduction during storm situations at standstill, but operational loads are also investigated. In order to compare...... loads are reduced by approximately 20% for the PP-2B and 18% for the PP-3B compared with the 3B turbine for the parked condition in a storm situation. Moreover, a huge potential of 60% is observed for the reduction of the extreme tower bottom bending moment for the PP-2B turbine, when the wind direction...... is from ±90° to the turbine, but this also requires that the turbine is parked in a T-configuration. © 2014 The Authors. Wind Energy published by John Wiley & Sons, Ltd....

On Space-Time Resolution of Inflow Representations for Wind Turbine Loads Analysis

Directory of Open Access Journals (Sweden)

Lance Manuel

2012-06-01

Full Text Available Efficient spatial and temporal resolution of simulated inflow wind fields is important in order to represent wind turbine dynamics and derive load statistics for design. Using Fourier-based stochastic simulation of inflow turbulence, we first investigate loads for a utility-scale turbine in the neutral atmospheric boundary layer. Load statistics, spectra, and wavelet analysis representations for different space and time resolutions are compared. Next, large-eddy simulation (LES is employed with space-time resolutions, justified on the basis of the earlier stochastic simulations, to again derive turbine loads. Extreme and fatigue loads from the two approaches used in inflow field generation are compared. On the basis of simulation studies carried out for three different wind speeds in the turbine’s operating range, it is shown that inflow turbulence described using 10-meter spatial resolution and 1 Hz temporal resolution is adequate for assessing turbine loads. Such studies on the investigation of adequate filtering or resolution of inflow wind fields help to establish efficient strategies for LES and other physical or stochastic simulation needed in turbine loads studies.

Early warnings of extreme winds using the ECMWF Extreme Forecast Index

DEFF Research Database (Denmark)

Petroliagis, Thomas I.; Pinson, Pierre

2014-01-01

The European FP7 SafeWind Project aims at developing research towards a European vision of wind power forecasting, which requires advanced meteorological support concerning extreme wind events. This study is focused mainly on early warnings of extreme winds in the early medium-range. Three synoptic...... regimes. Overall, it becomes clear that the first indications of an extreme wind event might come from the ECMWF deterministic and/or probabilistic components capturing very intense weather systems (possible windstorms) in the medium term. For early warnings, all available EPS Extreme Forecast Index (EFI......) formulations were used, by linking daily maximum wind speeds to EFI values for different forecast horizons. From all possible EFI schemes deployed for issuing early warnings, the highest skill was found for the Gust Factor formulation (EFI-10FGI). Using EFI-10FGI, the corresponding 99% threshold could provide...

Wind Structure and Wind Loading

DEFF Research Database (Denmark)

Brorsen, Michael

The purpose of this note is to provide a short description of wind, i.e. of the flow in the atmosphere of the Earth and the loading caused by wind on structures. The description comprises: causes to the generation of windhe interaction between wind and the surface of the Earthhe stochastic nature...

Statistical Model of Extreme Shear

DEFF Research Database (Denmark)

Larsen, Gunner Chr.; Hansen, Kurt Schaldemose

2004-01-01

In order to continue cost-optimisation of modern large wind turbines, it is important to continously increase the knowledge on wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describe the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of high-sampled full-scale time series measurements...... are consistent, given the inevitabel uncertainties associated with model as well as with the extreme value data analysis. Keywords: Statistical model, extreme wind conditions, statistical analysis, turbulence, wind loading, statistical analysis, turbulence, wind loading, wind shear, wind turbines....

Wind Turbine Load Mitigation based on Multivariable Robust Control and Blade Root Sensors

Science.gov (United States)

Díaz de Corcuera, A.; Pujana-Arrese, A.; Ezquerra, J. M.; Segurola, E.; Landaluze, J.

2014-12-01

This paper presents two H∞ multivariable robust controllers based on blade root sensors' information for individual pitch angle control. The wind turbine of 5 MW defined in the Upwind European project is the reference non-linear model used in this research work, which has been modelled in the GH Bladed 4.0 software package. The main objective of these controllers is load mitigation in different components of wind turbines during power production in the above rated control zone. The first proposed multi-input multi-output (MIMO) individual pitch H" controller mitigates the wind effect on the tower side-to-side acceleration and reduces the asymmetrical loads which appear in the rotor due to its misalignment. The second individual pitch H" multivariable controller mitigates the loads on the three blades reducing the wind effect on the bending flapwise and edgewise momentums in the blades. The designed H" controllers have been validated in GH Bladed and an exhaustive analysis has been carried out to calculate fatigue load reduction on wind turbine components, as well as to analyze load mitigation in some extreme cases.

Extreme Value Predictions for Wave- and Wind-induced Loads on Floating Offshore Wind Turbines using FORM

DEFF Research Database (Denmark)

Joensen, Sunvard; Jensen, Jørgen Juncher; Mansour, Alaa E.

2007-01-01

duration of the time domain simulations needed (typically 60-300s to cover the hy-drodynamic memory effects in the response) the calcu-lation of the mean out-crossing rates of a given response are very fast. Thus complicated non-linear effects can be included. The FORM analysis also identifies the most...... probable wave episodes leading to given re-sponses. As an example the motions of floating foundations for offshore wind turbines are analysed taking into consid-eration both the wave and wind induced loads and con-sidering different mooring systems. The possible large horizontal motions make it important...

Fusing Simulation Results From Multifidelity Aero-servo-elastic Simulators - Application To Extreme Loads On Wind Turbine

DEFF Research Database (Denmark)

Abdallah, Imad; Sudret, Bruno; Lataniotis, Christos

2015-01-01

Fusing predictions from multiple simulators in the early stages of the conceptual design of a wind turbine results in reduction in model uncertainty and risk mitigation. Aero-servo-elastic is a term that refers to the coupling of wind inflow, aerodynamics, structural dynamics and controls. Fusing...... the response data from multiple aero-servo-elastic simulators could provide better predictive ability than using any single simulator. The co-Kriging approach to fuse information from multifidelity aero-servo-elastic simulators is presented. We illustrate the co-Kriging approach to fuse the extreme flapwise...... bending moment at the blade root of a large wind turbine as a function of wind speed, turbulence and shear exponent in the presence of model uncertainty and non-stationary noise in the output. The extreme responses are obtained by two widely accepted numerical aero-servo-elastic simulators, FAST...

Wind Climate Parameters for Wind Turbine Fatigue Load Assessment

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Svenningsen, Lasse; Moser, Wolfgang

2016-01-01

Site-specific assessment of wind turbine design requires verification that the individual wind turbine components can survive the site-specific wind climate. The wind turbine design standard, IEC 61400-1 (third edition), describes how this should be done using a simplified, equivalent wind climate...... climate required by the current design standard by comparing damage equivalent fatigue loads estimated based on wind climate parameters for each 10 min time-series with fatigue loads estimated based on the equivalent wind climate parameters. Wind measurements from Boulder, CO, in the United States...

H∞ Based Control for Load Mitigation in Wind Turbines

Directory of Open Access Journals (Sweden)

Aron Pujana-Arrese

2012-04-01

Full Text Available This article demonstrates a strategy to design multivariable and multi-objective controllers based on the H∞ norm reduction applied to a wind turbine. The wind turbine model has been developed in the GH Bladed software and it is based on a 5 MW wind turbine defined in the Upwind European project. The designed control strategy works in the above rated power production zone and performs generator speed control and load reduction on the drive train and tower. In order to do this, two robust H∞ MISO (Multi-Input Single-Output controllers have been developed. These controllers generate collective pitch angle and generator torque set-point values to achieve the imposed control objectives. Linear models obtained in GH Bladed 4.0 are used, but the control design methodology can be used with linear models obtained from any other modelling package. Controllers are designed by setting out a mixed sensitivity problem, where some notch filters are also included in the controller dynamics. The obtained H∞ controllers have been validated in GH Bladed and an exhaustive analysis has been carried out to calculate fatigue load reduction on wind turbine components, as well as to analyze load mitigation in some extreme cases. The analysis compares the proposed control strategy based on H∞ controllers to a baseline control strategy designed using the classical control methods implemented on the present wind turbines.

Wind Turbine Load Mitigation based on Multivariable Robust Control and Blade Root Sensors

International Nuclear Information System (INIS)

Corcuera, A Díaz de; Pujana-Arrese, A; Ezquerra, J M; Segurola, E; Landaluze, J

2014-01-01

This paper presents two H ∞ multivariable robust controllers based on blade root sensors' information for individual pitch angle control. The wind turbine of 5 MW defined in the Upwind European project is the reference non-linear model used in this research work, which has been modelled in the GH Bladed 4.0 software package. The main objective of these controllers is load mitigation in different components of wind turbines during power production in the above rated control zone. The first proposed multi-input multi-output (MIMO) individual pitch H'' controller mitigates the wind effect on the tower side-to-side acceleration and reduces the asymmetrical loads which appear in the rotor due to its misalignment. The second individual pitch H'' multivariable controller mitigates the loads on the three blades reducing the wind effect on the bending flapwise and edgewise momentums in the blades. The designed H'' controllers have been validated in GH Bladed and an exhaustive analysis has been carried out to calculate fatigue load reduction on wind turbine components, as well as to analyze load mitigation in some extreme cases

Extreme Response for Wind Turbines

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

2009-01-01

The characteristic load on wind turbines during operation are among others dependent on the mean wind speed, the turbulence intensity and type and settings of the control system. The characteristic load during operation is normally estimated by statistical extrapolation of a limited number...... of simulated 10min time series of the response according to the wind turbine standard IEC 61400-1. However, this method assumes that the individual 10min time series and the extracted peaks from the time series are independent. In the present paper is this assumption investigated based on field measurements...

Breaking phase focused wave group loads on offshore wind turbine monopiles

DEFF Research Database (Denmark)

Ghadirian, Amin; Bredmose, Henrik; Dixen, M.

2016-01-01

The current method for calculating extreme wave loads on offshore wind turbine structures is based on engineering models for non-breaking regular waves. The present article has the aim of validating previously developed models at DTU, namely the OceanWave3D potential flow wave model and a coupled...

The influence of the static wind load concept on the material requirements for reinforced-concrete natural-draught cooling towers

International Nuclear Information System (INIS)

Harnach, R.

1977-01-01

The natural wind is the decisive risk factor in natural-draught cooling towers; therefore, the establishment of an assumed velocity is indispensable for the safety and reliability of the construction. In the framework of a statistical wind concept, static substitution loads for the assumed dynamic wind pressure have been determined, also including dynamic wind effects and the resonance response of the structure. On this basis, it has been studied how wind loads with different periodicity affect the material requirements of reinforced-concrete natural-draught cooling towers. It is found that the additional steel requirements, related to the total building cost, remain within acceptable limits even for extreme wind loads. (orig.) [de

Regional tendencies of extreme wind characteristics in Hungary

Science.gov (United States)

Radics, Dr.; Bartholy, Dr.; Péliné

2009-09-01

Human activities have substantial effects on climate system. It has already accepted that change in the long-term climatic mean state will have significant consequences in the global economy and society, but the most important effects of climate change may come from changes in the intensity and frequency of climatic extremes. It is therefore of great interest to document the extremes of surface wind that could assist in estimating the regional effects of climate change. The research presented is based on 34-year-long (1975-2008) wind (speed, direction, and wind gust) data sets of 36 Hungarian synoptic meteorological stations. After processing (including digitalisation of old instrumental records, quality control and homogenisation of wind time series) the measured wind data sets, time series and complex wind climate analysis were carried out. Spatial and temporal distributions of mean and extreme wind climate characteristics were estimated, wind extremes and trends were interpolated and mapped over the country. Finally, measured and reanalysed (ERA40) wind data were compared over Hungary, in order to verify not only the validity of ERA40 reanalysed data sets, but the adaptability of climate simulation results in estimation of regional climate change effects.

A model for Quick Load Analysis for monopile-type offshore wind turbine substructures

DEFF Research Database (Denmark)

Schløer, Signe; Castillo, Laura Garcia; Fejerskov, Morten

2016-01-01

A model for Quick Load Analysis, QuLA, of an offshore wind turbine substructure is presented. The aerodynamic rotor loads and damping are precomputed for a load-based configuration. The dynamic structural response is represented by the first global fore-aft mode only and is computed...... in the frequency domain using the equation of motion. The model is compared against the state of the art aeroelastic code, Flex5, and both life time fatigue and extreme loads are considered in the comparison. In general there is good similarity between the two models. Some derivation for the sectional forces...... are explained in terms of the model simplifications. The difference in the sectional moments are found to be within 14% for the fatigue load case and 10% for the extreme load condition....

Load Extrapolation During Operation for Wind Turbines

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

2008-01-01

In the recent years load extrapolation for wind turbines has been widely considered in the wind turbine industry. Loads on wind turbines during operations are normally dependent on the mean wind speed, the turbulence intensity and the type and settings of the control system. All these parameters...... must be taken into account when characteristic load effects during operation are determined. In the wind turbine standard IEC 61400-1 a method for load extrapolation using the peak over threshold method is recommended. In this paper this method is considered and some of the assumptions are examined...

Response Load Extrapolation for Wind Turbines during Operation Based on Average Conditional Exceedance Rates

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Naess, Arvid; Saha, Nilanjan

2011-01-01

to cases where the Gumbel distribution is the appropriate asymptotic extreme value distribution. However, two extra parameters are introduced by which a more general and flexible class of extreme value distributions is obtained with the Gumbel distribution as a subclass. The general method is implemented...... within a hierarchical model where the variables that influence the loading are divided into ergodic variables and time-invariant non-ergodic variables. The presented method for statistical response load extrapolation was compared with the existing methods based on peak extrapolation for the blade out......The paper explores a recently developed method for statistical response load (load effect) extrapolation for application to extreme response of wind turbines during operation. The extrapolation method is based on average conditional exceedance rates and is in the present implementation restricted...

Fatigue and extreme wave loads on bottom fixed offshore wind turbines. Effects from fully nonlinear wave forcing on the structural dynamics

DEFF Research Database (Denmark)

Schløer, Signe

2013-01-01

wind farms. As wind farms are being moved further offshore the wave loads become larger compared to the wind loads and therefore more important in the design of offshore wind turbines. Yet, the water depth is still only shallow or intermediate where the waves should be described by nonlinear irregular...

Wind loads on flat plate photovoltaic array fields (nonsteady winds)

Science.gov (United States)

Miller, R. D.; Zimmerman, D. K.

1981-01-01

Techniques to predict the dynamic response and the structural dynamic loads of flat plate photovoltaic arrays due to wind turbulence were analyzed. Guidelines for use in predicting the turbulent portion of the wind loading on future similar arrays are presented. The dynamic response and the loads dynamic magnification factor of the two array configurations are similar. The magnification factors at a mid chord and outer chord location on the array illustrated and at four points on the chord are shown. The wind tunnel test experimental rms pressure coefficient on which magnification factors are based is shown. It is found that the largest response and dynamic magnification factor occur at a mid chord location on an array and near the trailing edge. A technique employing these magnification factors and the wind tunnel test rms fluctuating pressure coefficients to calculate design pressure loads due to wind turbulence is presented.

A Cyber-Based Data-Enabled Virtual Organization for Wind Load Effects on Civil Infrastructures: VORTEX-Winds

Directory of Open Access Journals (Sweden)

Ahsan Kareem

2017-08-01

Full Text Available Despite many advances in the area of wind effects on structures in recent decades, research has been traditionally conducted within limited resources scattered geographically. With the trend toward increasingly complex designs of civil infrastructure combined with the escalating potential for losses by extreme wind events, a new culture of research needs to be established based on innovative and collaborative solutions for better management of the impact of extreme wind events. To address this change, this paper presents a new paradigm of a multiscale cyber-based laboratory framework for the analysis/design, modeling, and simulation of wind load effects based on an ongoing collaborative cyberinfrastructure-based platform, Virtual Organization for Reducing the Toll of EXtreme Winds (VORTEX-Winds, https://vortex-winds.org, and discusses its current status since its inception in 2007 and ongoing developments. This collaborative framework as it evolves would enable a paradigm shift by offering advanced cyber-enabled modules (e-modules for accelerating advances in research and education to achieve improved understanding and better modeling of wind effects on structures. Accordingly, it will enhance wind community’s analysis and design capabilities to address next-generation challenges posed by wind. Through empowering those without computational or experimental resources, the e-modules will encompass a large set of subject areas and topics categorized as Database-enabled design, Full-scale/Field site data repository, Statistical/Stochastic toolboxes, Tele-experimentation, Uncertainty modeling, Damage assessment, and Computational platforms. This prototype will allow access to the individual e-module, while it is envisaged that next level of development in VORTEX-Winds will have the capability for an automated and integrated analysis/design through a nexus of e-modules. A highlight of the e-modules currently completed or in development is presented

Current summary of international extreme load design requirements for nuclear power plant facilities

International Nuclear Information System (INIS)

Stevenson, J.D.

1980-01-01

The development of extreme load design criteria both as to rate and depth within any national jurisdiction as applied to nuclear power plant design is a function of several factors. The prime factor is the number of nuclear power plant facilities which are operating, under construction or planned in a given country. The second most important factor seems to be the degree of development of a domestic independent nuclear steam system supplier, NSSS vendor. Finally, countries whose domestic NSSS firms are active in the export market appear to have more active criteria development programs or at least they appear more visible to the foreign observer. For the purposes of this paper, extreme loads are defined as those loads having probability of occurence less than 10 -1 /yr and whose occurence could result in radiological consequences in excess of those permitted by national health standards. The specific loads considered include earthquake, extreme wind (tornado), airplane crash, detonation, and high energy system rupture. The paper identifies five national centers for extreme load criteria development; Canada, Great Britian, USA, USSR, and West Germany with both France and Japan also about to appear as independent centers of criteria development. Criteria under development by each national center are discussed in detail. (orig.)

Operation and Equivalent Loads of Wind Turbines in Large Wind Farms

Science.gov (United States)

Andersen, Soren Juhl; Sorensen, Jens Norkaer; Mikkelsen, Robert Flemming

2017-11-01

Wind farms continue to grow in size and as the technology matures, the design of wind farms move towards including dynamic effects besides merely annual power production estimates. The unsteady operation of wind turbines in large wind farms has been modelled with EllipSys3D(Michelsen, 1992, and Sørensen, 1995) for a number of different scenarios using a fully coupled large eddy simulations(LES) and aero-elastic framework. The turbines are represented in the flow fields using the actuator line method(Sørensen and Shen, 2002), where the aerodynamic forces and deflections are derived from an aero-elastic code, Flex5(Øye, 1996). The simulations constitute a database of full turbine operation in terms of both production and loads for various wind speeds, turbulence intensities, and turbine spacings. The operating conditions are examined in terms of averaged power production and thrust force, as well as 10min equivalent flapwise bending, yaw, and tilt moment loads. The analyses focus on how the performance and loads change throughout a given farm as well as comparing how various input parameters affect the operation and loads of the wind turbines during different scenarios. COMWIND(Grant 2104-09- 067216/DSF), Nordic Consortium on Optimization and Control of Wind Farms, Eurotech Greentech Wind project, Winds2Loads, and CCA LES. Ressources Granted on SNIC and JESS. The Vestas NM80 turbine has been used.

Survey of extreme load design regulatory agency licensing requirements for nuclear power plants

Energy Technology Data Exchange (ETDEWEB)

Stevenson, J D

1976-04-01

Since 1965, when extreme load requirements began to be considered explicitly in nuclear power plant design, there has been a gradual divergence in requirements imposed by national regulatory agencies. However, nuclear plant safety is an international problem because of the potential international effects of any postulated plant failure. For this reason this paper has been prepared in an attempt to highlight the differences in national criteria currently used in the extreme load design of nuclear plant facilities. No attempt has been made to evaluate the relative merit of the criteria established by the various national regulatory agencies. This paper presents the results of a recent survey made of national atomic energy regulatory agencies and major nuclear steam supply design agencies, which requested a summary of current licensing criteria associated with earthquake, extreme wind (tornado), flood, airplane crash and accident (pipe break) loads applicable within the various national jurisdictions. Also presented are a number of comparisons which are meant to illustrate the differences in national regulatory criteria.

Survey of extreme load design regulatory agency licensing requirements for nuclear power plants

International Nuclear Information System (INIS)

Stevenson, J.D.

1976-01-01

Since 1965, when extreme load requirements began to be considered explicitly in nuclear power plant design, there has been a gradual divergence in requirements imposed by national regulatory agencies. However, nuclear plant safety is an international problem because of the potential international effects of any postulated plant failure. For this reason this paper has been prepared in an attempt to highlight the differences in national criteria currently used in the extreme load design of nuclear plant facilities. No attempt has been made to evaluate the relative merit of the criteria established by the various national regulatory agencies. This paper presents the results of a recent survey made of national atomic energy regulatory agencies and major nuclear steam supply design agencies, which requested a summary of current licensing criteria associated with earthquake, extreme wind (tornado), flood, airplane crash and accident (pipe break) loads applicable within the various national jurisdictions. Also presented are a number of comparisons which are meant to illustrate the differences in national regulatory criteria. (Auth.)

Assessment of Wind Parameter Sensitivity on Ultimate and Fatigue Wind Turbine Loads: Preprint

Energy Technology Data Exchange (ETDEWEB)

Robertson, Amy N [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Sethuraman, Latha [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Jonkman, Jason [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Quick, Julian [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2018-02-13

Wind turbines are designed using a set of simulations to ascertain the structural loads that the turbine could encounter. While mean hub-height wind speed is considered to vary, other wind parameters such as turbulence spectra, sheer, veer, spatial coherence, and component correlation are fixed or conditional values that, in reality, could have different characteristics at different sites and have a significant effect on the resulting loads. This paper therefore seeks to assess the sensitivity of different wind parameters on the resulting ultimate and fatigue loads on the turbine during normal operational conditions. Eighteen different wind parameters are screened using an Elementary Effects approach with radial points. As expected, the results show a high sensitivity of the loads to the turbulence standard deviation in the primary wind direction, but the sensitivity to wind shear is often much greater. To a lesser extent, other wind parameters that drive loads include the coherence in the primary wind direction and veer.

Mean and peak wind load reduction on heliostats

Energy Technology Data Exchange (ETDEWEB)

Peterka, J.A.; Tan, L.; Bienkiewcz, B.; Cermak, J.E.

1987-09-01

This report presents the results of wind-tunnel tests supported through the Solar Energy Research Institute (SERI) by the Office of Solar Thermal Technology of the US Department of Energy as part of the SERI research effort on innovative concentrators. As gravity loads on drive mechanisms are reduced through stretched-membrane technology, the wind-load contribution of the required drive capacity increases in percentage. Reduction of wind loads can provide economy in support structure and heliostat drive. Wind-tunnel tests have been directed at finding methods to reduce wind loads on heliostats. The tests investigated both mean and peak forces, and moments. A significant increase in ability to predict heliostat wind loads and their reduction within a heliostat field was achieved. In addition, a preliminary review of wind loads on parabolic dish collectors was conducted, resulting in a recommended research program for these type collectors. 42 refs., 38 figs., 1 tab.

Model of wind shear conditional on turbulence and its impact on wind turbine loads

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov; Natarajan, Anand; Kelly, Mark C.

2015-01-01

proposed for flat terrain and that can significantly decrease the uncertainty associated with fatigue load predictions for wind turbines with large rotors. An essential contribution is the conditioning of wind shear on the 90% quantile of wind turbulence, such that the appropriate magnitude of the design...... fatigue load is achieved. The proposed wind shear model based on the wind measurements is thereby probabilistic in definition, with shear jointly distributed with wind turbulence. A simplified model for the wind shear exponent is further derived from the full stochastic model. The fatigue loads over...... is most pronounced on the blade flap loads. It is further shown that under moderate wind turbulence, the wind shear exponents may be over-specified in the design standards, and a reduction of wind shear exponent based on the present measurements can contribute to reduced fatigue damage equivalent loads...

Estimation of extreme wind speeds in the mixed strong wind climate of South Africa

CSIR Research Space (South Africa)

Kruger, AC

2010-08-01

Full Text Available wind-generating mechanisms for Australia. Annual extreme wind speeds are generated by different mechanisms, forthcoming from thunderstorm activity and the passages of extratropical low pressure systems, which were identified. Separate extreme value...

Extreme Winds from the NCEP/NCAR Reanalysis Data

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Mann, Jakob

2009-01-01

wind. We examined extreme winds in different places where the strongest wind events are weather phenomena of different scales, including the mid-latitude lows in Denmark, channelling winds in the Gulf of Suez, typhoons in the western North Pacific, cyclones in the Caribbean Sea, local strong winds...

Load alleviation of wind turbines by yaw misalignment

DEFF Research Database (Denmark)

Kragh, Knud Abildgaard; Hansen, Morten Hartvig

2014-01-01

Vertical wind shear is one of the dominating causes of load variations on the blades of a horizontal axis wind turbine. To alleviate the varying loads, wind turbine control systems have been augmented with sensors and actuators for individual pitch control. However, the loads caused by a vertical...... wind shear can also be affected through yaw misalignment. Recent studies of yaw control have been focused on improving the yaw alignment to increase the power capture at below rated wind speeds. In this study, the potential of alleviating blade load variations induced by the wind shear through yaw...... misalignment is assessed. The study is performed through simulations of a reference turbine. The study shows that optimal yaw misalignment angles for minimizing the blade load variations can be identified for both deterministic and turbulent inflows. It is shown that the optimal yaw misalignment angles can...

Effect of linear and non-linear blade modelling techniques on simulated fatigue and extreme loads using Bladed

Science.gov (United States)

Beardsell, Alec; Collier, William; Han, Tao

2016-09-01

There is a trend in the wind industry towards ever larger and more flexible turbine blades. Blade tip deflections in modern blades now commonly exceed 10% of blade length. Historically, the dynamic response of wind turbine blades has been analysed using linear models of blade deflection which include the assumption of small deflections. For modern flexible blades, this assumption is becoming less valid. In order to continue to simulate dynamic turbine performance accurately, routine use of non-linear models of blade deflection may be required. This can be achieved by representing the blade as a connected series of individual flexible linear bodies - referred to in this paper as the multi-part approach. In this paper, Bladed is used to compare load predictions using single-part and multi-part blade models for several turbines. The study examines the impact on fatigue and extreme loads and blade deflection through reduced sets of load calculations based on IEC 61400-1 ed. 3. Damage equivalent load changes of up to 16% and extreme load changes of up to 29% are observed at some turbine load locations. It is found that there is no general pattern in the loading differences observed between single-part and multi-part blade models. Rather, changes in fatigue and extreme loads with a multi-part blade model depend on the characteristics of the individual turbine and blade. Key underlying causes of damage equivalent load change are identified as differences in edgewise- torsional coupling between the multi-part and single-part models, and increased edgewise rotor mode damping in the multi-part model. Similarly, a causal link is identified between torsional blade dynamics and changes in ultimate load results.

Inverse load calculation procedure for offshore wind turbines and application to a 5-MW wind turbine support structure: Inverse load calculation procedure for offshore wind turbines

Energy Technology Data Exchange (ETDEWEB)

Pahn, T. [Pahn Ingenieure, Am Seegraben 17b 03051 Cottbus Germany; Rolfes, R. [Institut f?r Statik und Dynamik, Leibniz Universit?t Hannover, Appelstra?e 9A 30167 Hannover Germany; Jonkman, J. [National Renewable Energy Laboratory, 15013 Denver West Parkway Golden Colorado 80401 USA

2017-02-20

A significant number of wind turbines installed today have reached their designed service life of 20 years, and the number will rise continuously. Most of these turbines promise a more economical performance if they operate for more than 20 years. To assess a continued operation, we have to analyze the load-bearing capacity of the support structure with respect to site-specific conditions. Such an analysis requires the comparison of the loads used for the design of the support structure with the actual loads experienced. This publication presents the application of a so-called inverse load calculation to a 5-MW wind turbine support structure. The inverse load calculation determines external loads derived from a mechanical description of the support structure and from measured structural responses. Using numerical simulations with the software fast, we investigated the influence of wind-turbine-specific effects such as the wind turbine control or the dynamic interaction between the loads and the support structure to the presented inverse load calculation procedure. fast is used to study the inverse calculation of simultaneously acting wind and wave loads, which has not been carried out until now. Furthermore, the application of the inverse load calculation procedure to a real 5-MW wind turbine support structure is demonstrated. In terms of this practical application, setting up the mechanical system for the support structure using measurement data is discussed. The paper presents results for defined load cases and assesses the accuracy of the inversely derived dynamic loads for both the simulations and the practical application.

Probabilistic Design of Wind Turbines

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard

During the last decades, wind turbines have been continuously developed with the aim of maximizing the life cycle benefits (production of electricity) minus the costs of planning, materials, installation, operation & maintenance as well as possible failure. In order to continue this development...... turbines and the central topics considered are statistical load extrapolation of extreme loads during operation and reliability assessment of wind turbine blades. Wind turbines differ from most civil engineering structures by having a control system which highly influences the loading. In the literature......, methods for estimating the extreme load-effects on a wind turbine during operation, where the control system is active, have been proposed. But these methods and thereby the estimated loads are often subjected to a significant uncertainty which influences the reliability of the wind turbine...

The Dutch wind tunnel guideline for wind loads

NARCIS (Netherlands)

Geurts, C.P.W.; Bentum, van C.A.; Willemsen, E.

2013-01-01

This paper addresses questions that arose during development and application of the Dutch guideline for wind tunnel testing to determine wind loads on buildings. This guideline (CUR 103) is being used since 2005, and a first revision is foreseen. Within this revision, the relation with Eurocode EN

When real life wind speed exceeds design wind assumptions

Energy Technology Data Exchange (ETDEWEB)

Winther-Jensen, M; Joergensen, E R [Risoe National Lab., Roskilde (Denmark)

1999-03-01

Most modern wind turbines are designed according to a standard or a set of standards to withstand the design loads with a defined survival probability. Mainly the loads are given by the wind conditions on the site defining the `design wind speeds`, normally including extreme wind speeds given as an average and a peak value. The extreme wind speeds are normally (e.g. in the upcoming IEC standard for wind turbine safety) defined as having a 50-year recurrence period. But what happens when the 100 or 10,000 year wind situation hits a wind turbine? Results on wind turbines of wind speeds higher than the extreme design wind speeds are presented based on experiences especially from the State of Gujarat in India. A description of the normal approach of designing wind turbines in accordance with the standards in briefly given in this paper with special focus on limitations and built-in safety levels. Based on that, other possibilities than just accepting damages on wind turbines exposed for higher than design wind speeds are mentioned and discussed. The presentation does not intend to give the final answer to this problem but is meant as an input to further investigations and discussions. (au)

Influence of wind conditions on wind turbine loads and measurement of turbulence using lidars

NARCIS (Netherlands)

Sathe, A.R.

2012-01-01

Variations in wind conditions influence the loads on wind turbines significantly. In order to determine these loads it is important that the external conditions are well understood. Wind lidars are well developed nowadays to measure wind profiles upwards from the surface. But how turbulence can be

Structural investigation of composite wind turbine blade considering various load cases and fatigue life

International Nuclear Information System (INIS)

Kong, C.; Bang, J.; Sugiyama, Y.

2005-01-01

This study proposes a structural design for developing a medium scale composite wind turbine blade made of E-glass/epoxy for a 750 kW class horizontal axis wind turbine system. The design loads were determined from various load cases specified at the IEC61400-1 international specification and GL regulations for the wind energy conversion system. A specific composite structure configuration, which can effectively endure various loads such as aerodynamic loads and loads due to accumulation of ice, hygro-thermal and mechanical loads, was proposed. To evaluate the proposed composite wind turbine blade, structural analysis was performed by using the finite element method. Parametric studies were carried out to determine an acceptable blade structural design, and the most dominant design parameters were confirmed. In this study, the proposed blade structure was confirmed to be safe and stable under various load conditions, including the extreme load conditions. Moreover, the blade adapted a new blade root joint with insert bolts, and its safety was verified at design loads including fatigue loads. The fatigue life of a blade that has to endure for more than 20 years was estimated by using the well-known S-N linear damage theory, the service load spectrum, and the Spera's empirical equations. With the results obtained from all the structural design and analysis, prototype composite blades were manufactured. A specific construction process including the lay-up molding method was applied to manufacturing blades. Full-scale static structural test was performed with the simulated aerodynamic loads. From the experimental results, it was found that the designed blade had structural integrity. In addition, the measured results of deflections, strains, mass, and radial center of gravity agreed well with the analytical results. The prototype blade was successfully certified by an international certification institute, GL (Germanisher Lloyd) in Germany

Wind and load variability in the Nordic countries

Energy Technology Data Exchange (ETDEWEB)

Holttinen, H.; Rissanen, S. [VTT Technical Research Centre of Finland, Espoo (Finland); Larsen, X. [Danmarks Tekniske Universitet, Lyngby (Denmark); Loevholm, A. L. [Kjeller Vindteknikk (Norway)

2013-04-15

This publication analysed the variability of wind production and load in Denmark, Finland, Sweden, and the Nordic region as a whole, based on real data measured from large-scale wind power during 2009-2011. The Nordic-wide wind power time series was scaled up such that Sweden had same amount of wind power production than Denmark, and Finland and Norway only 50% of the wind power production in Denmark. Wind power production in Denmark and Sweden is somewhat correlated (coefficient 0.7) but less correlation is found between the other countries. The variations from one hour to the next are only weakly correlated between all countries, even between Denmark and Sweden. Largest variations occur when the production is approximately 30-70% of installed capacity and variability is low during periods of light winds. The variability in shorter time scales was less than the hourly variations. During the three years analysed in this publication there were few storm incidents and they did not produce dramatic wind power ramps in the Nordic region. Wind and load variations are not correlated between the countries, which is beneficial from the viewpoint of wind integration. The smoothing effect is shown as reduction of variability from a single country to Nordic-wide wind power. The impact of wind power on the variability that the system experiences is evaluated by analysing the variability of net load with different wind power penetration levels. The Nordic-wide wind power production increases the highest hourly ramps by 2.4% (up) and -3.6% (down) of installed wind power capacity when there is 20% wind power penetration and by 2.7% (up) and -4.7% (down) for 30% wind penetration. These results assess the impacts of variability only. The next step will be assessing the uncertainty from forecast errors. The timing of ramp events, and occurrence of high-wind and low-load are studied. With current wind penetration, low production levels (2-5% of installed wind power) can occur in a

Load reduced control procedure for wind power plants. A holistic survey and experiences from field tests; Lastreduzierende Regelungsverfahren fuer Windenergieanlagen. Ein ganzheitlicher Ueberblick und Erfahrungen aus Feldversuchen

Energy Technology Data Exchange (ETDEWEB)

Shan, M.; Fischer, B.; Duckwitz, D. [Fraunhofer Institut fuer Windenergie und Energiesystemtechnik (IWES), Kassel (Germany)

2013-06-01

The control system of a wind turbine has a large impact on the structural dynamic loads of wind power plants. The contribution under consideration reports on the opportunities for an active reduction of fatigue loads and extreme loads for various mechanical components using the variables pitch angle and generator torque.

Assessment of wind turbine load measurement instrumentation

Energy Technology Data Exchange (ETDEWEB)

Morfiadakis, E; Papadopoulos, K [CRES (Greece); Borg, N van der [ECN, Petten (Netherlands); Petersen, S M [Risoe, Roskilde (Denmark); Seifert, H [DEWI, Wilhelmshaven (Germany)

1999-03-01

In the framework of Sub-Task3 `Wind turbine load measurement instrumentation` of EU-project `European Wind Turbine Testing Procedure Development`, the load measurement techniques have been assessed by laboratory, full scale and numerical tests. The existing methods have been reviewed with emphasis on the strain gage application techniques on composite materials and recommendations are provided for the optimisation of load measurement techniques. (au) EU. 14 refs.

Blade-Pitch Control for Wind Turbine Load Reductions

DEFF Research Database (Denmark)

Lio, Alan Wai Hou

Large wind turbines are subjected to the harmful loads that arise from the spatially uneven and temporally unsteady oncoming wind. Such loads are the known sources of fatigue damage that reduce the turbine operational lifetime, ultimately increasing the cost of wind energy to the end-users. In re...

Thermal loading of wind power converter considering dynamics of wind speed

DEFF Research Database (Denmark)

Baygildina, Elvira; Peltoniemi, Pasi; Pyrhönen, Olli

2013-01-01

The thermal loading of power semiconductors is a crucial performance related to the reliability and cost of the wind power converter. However, the thermal loading impacts by the variation of wind speeds have not yet been clarified, especially when considering the aerodynamic behavior of the wind...... turbines. In this paper, the junction temperatures in the wind power converter are studied under not only steady state, but also turbulent wind speed conditions. The study is based on a 1.5 MW direct-driven turbine system with aerodynamic model described by Unsteady Blade Element Momentum Method (BEMM......), and the thermal stress of power devices is investigated from the frequency spectrum point of view of wind speed. It is concluded that because of the strong inertia effects by the aerodynamic behavior of wind turbines, thermal stress of the semiconductors is relatively more stable and only influenced by the low...

Design Load Basis for Offshore Wind turbines

DEFF Research Database (Denmark)

Natarajan, Anand; Hansen, Morten Hartvig; Wang, Shaofeng

2016-01-01

DTU Wind Energy is not designing and manufacturing wind turbines and does therefore not need a Design Load Basis (DLB) that is accepted by a certification body. However, to assess the load consequences of innovative features and devices added to existing offshore turbine concepts or new offshore...... turbine concept developed in our research, it is useful to have a full DLB that follows the current design standard and is representative of a general DLB used by the industry. It will set a standard for the offshore wind turbine design load evaluations performed at DTU Wind Energy, which is aligned...... with the challenges faced by the industry and therefore ensures that our research continues to have a strong foundation in this interaction. Furthermore, the use of a full DLB that follows the current standard can improve and increase the feedback from the research at DTU Wind Energy to the international...

How good are remote sensors at measuring extreme winds?

NARCIS (Netherlands)

Sathe, A.R.; Courtney, M.; Mann, J.; Wagner, R.

2011-01-01

This article describes some preliminary efforts within the SafeWind project, aimed to identify the possible added value of using wind lidars to detect extreme wind events. Exceptionally good performance is now regularly reported in the measurement of the mean wind speed with some wind lidars in flat

A comparison of measured wind park load histories with the WISPER and WISPERX load spectra

Science.gov (United States)

Kelley, N. D.

1995-01-01

The blade-loading histories from two adjacent Micon 65/13 wind turbines are compared with the variable-amplitude test-loading histories known as the WISPER and WISPERX spectra. These standardized loading sequences were developed from blade flapwise load histories taken from nine different horizontal-axis wind turbines operating under a wide range of conditions in Europe. The subject turbines covered a broad spectrum of rotor diameters, materials, and operating environments. The final loading sequences were developed as a joint effort of thirteen different European organizations. The goal was to develop a meaningful loading standard for horizontal-axis wind turbine blades that represents common interaction effects seen in service. In 1990, NREL made extensive load measurements on two adjacent Micon 65/13 wind turbines in simultaneous operation in the very turbulent environment of a large wind park. Further, before and during the collection of the loads data, comprehensive measurements of the statistics of the turbulent environment were obtained at both the turbines under test and at two other locations within the park. The trend to larger but lighter wind turbine structures has made an understanding of the expected lifetime loading history of paramount importance. Experience in the US has shown that the turbulence-induced loads associated with multi-row wind parks in general are much more severe than for turbines operating individually or within widely spaced environments. Multi-row wind parks are much more common in the US than in Europe. In this paper we report on our results in applying the methodology utilized to develop the WISPER and WISPERX standardized loading sequences using the available data from the Micon turbines. While the intended purpose of the WISPER sequences were not to represent a specific operating environment, we believe the exercise is useful, especially when a turbine design is likely to be installed in a multi-row wind park.

Wind loads on flat plate photovoltaic array fields

Science.gov (United States)

Miller, R. D.; Zimmerman, D. K.

1981-01-01

The results of an experimental analysis (boundary layer wind tunnel test) of the aerodynamic forces resulting from winds acting on flat plate photovoltaic arrays are presented. Local pressure coefficient distributions and normal force coefficients on the arrays are shown and compared to theoretical results. Parameters that were varied when determining the aerodynamic forces included tilt angle, array separation, ground clearance, protective wind barriers, and the effect of the wind velocity profile. Recommended design wind forces and pressures are presented, which envelop the test results for winds perpendicular to the array's longitudinal axis. This wind direction produces the maximum wind loads on the arrays except at the array edge where oblique winds produce larger edge pressure loads. The arrays located at the outer boundary of an array field have a protective influence on the interior arrays of the field. A significant decrease of the array wind loads were recorded in the wind tunnel test on array panels located behind a fence and/or interior to the array field compared to the arrays on the boundary and unprotected from the wind. The magnitude of this decrease was the same whether caused by a fence or upwind arrays.

Aeroelastic Ground Wind Loads Analysis Tool for Launch Vehicles

Science.gov (United States)

Ivanco, Thomas G.

2016-01-01

Launch vehicles are exposed to ground winds during rollout and on the launch pad that can induce static and dynamic loads. Of particular concern are the dynamic loads caused by vortex shedding from nearly-cylindrical structures. When the frequency of vortex shedding nears that of a lowly-damped structural mode, the dynamic loads can be more than an order of magnitude greater than mean drag loads. Accurately predicting vehicle response to vortex shedding during the design and analysis cycles is difficult and typically exceeds the practical capabilities of modern computational fluid dynamics codes. Therefore, mitigating the ground wind loads risk typically requires wind-tunnel tests of dynamically-scaled models that are time consuming and expensive to conduct. In recent years, NASA has developed a ground wind loads analysis tool for launch vehicles to fill this analytical capability gap in order to provide predictions for prelaunch static and dynamic loads. This paper includes a background of the ground wind loads problem and the current state-of-the-art. It then discusses the history and significance of the analysis tool and the methodology used to develop it. Finally, results of the analysis tool are compared to wind-tunnel and full-scale data of various geometries and Reynolds numbers.

Extending wind turbine operational conditions; a comparison of set point adaptation and LQG individual pitch control for highly turbulent wind

International Nuclear Information System (INIS)

Engels, W P; Subhani, S; Zafar, H; Savenije, F

2014-01-01

Extreme wind conditions can cause excessive loading on the turbine. This not only results in higher design loads, but when these conditions occur in practice, will also result in higher maintenance cost. Although there are already effective methods of dealing with gusts, other extreme conditions should also be examined. More specifically, extreme turbulence conditions (e.g. those specified by design load case 1.3 in IEC61400-1 ed. 3) require special attention as they can lead to design-driving extreme loads on blades, tower and other wind turbine components. This paper examines two methods to deal with extreme loads in a case of extreme turbulent wind. One method is derating the turbine, the other method is an individual pitch control (IPC) algorithm. Derating of the turbine can be achieved in two ways, one is changing the rated torque, the other is changing the rated rotor speed. The effect of these methods on fatigue loads and extreme loads is examined. Non-linear aero-elastic simulations using Phatas, show that reducing the rated rotor speed is far more effective at reducing the loads than reducing torque. Then, the IPC algorithm is proposed. This algorithm is a linear quadratic Gaussian (LQG) controller based on a time invariant model, defined in the fixed reference frame that includes the first tower and blade modes. Because this method takes the dynamics of the system into account more than conventional IPC control, it is expected that these loads dealt with more effectively, when they are particularly relevant. It is expected that in extreme turbulent the blade and tower dynamics are indeed more relevant. The effect of this algorithm on fatigue loads and pitch effort is examined and compared with the fatigue loads and pitch effort of reference IPC. Finally, the methods are compared in non-linear aero-elastic simulations with extreme turbulent wind

Effects of extreme wind shear on aeroelastic modal damping of wind turbines

DEFF Research Database (Denmark)

Skjoldan, P.F.; Hansen, Morten Hartvig

2013-01-01

Wind shear is an important contributor to fatigue loads on wind turbines. Because it causes an azimuthal variation in angle of attack, it can also affect aerodynamic damping. In this paper, a linearized model of a wind turbine, based on the nonlinear aeroelastic code BHawC, is used to investigate...

Load consequences when sweeping blades - A case study of a 5 MW pitch controlled wind turbine

Energy Technology Data Exchange (ETDEWEB)

Verelst, D.R.S.; Larsen, Torben J.

2010-08-15

The generic 5 MW NREL wind turbine model is used in Risoe's aeroelastic simulator HAWC2 to investigate 120 different swept blade configurations (forward and backward sweep). Sensitivity for 2 different controllers is considered as well. Backward sweep results in a pitch to feather torsional moment of the blade, effectively reducing blade twist angles under increased loading. This behaviour results in decreased flap-wise fatigue and extreme loads, an increase for edge-wise fatigue loading and status quo or slight decrease in extreme loads (depending on the controller). Tower base and shaft-end bending moments are reduced as well. Forward sweep leads to an increase in angle of attack under loading. For a pitch controlled turbine this leads to an increase in fatigue and extreme loading in all cases. A controller inflicted instability is present for the more extreme forward swept cases. Due to the shape of considered sweep curves, an inherent and significant increase in torsional blade root bending moment is noted. A boomerang shaped sweep curve is proposed to counteract this problematic increased loading. Controller sensitivity shows that adding sweep affects some loadings differently. Power output is reduced for backward sweep since the blade twist is optimized as a rigid structure, ignoring the torsional deformations which for a swept blade can be significant. (author)

Estimation of Extreme Response and Failure Probability of Wind Turbines under Normal Operation using Probability Density Evolution Method

DEFF Research Database (Denmark)

Sichani, Mahdi Teimouri; Nielsen, Søren R.K.; Liu, W. F.

2013-01-01

Estimation of extreme response and failure probability of structures subjected to ultimate design loads is essential for structural design of wind turbines according to the new standard IEC61400-1. This task is focused on in the present paper in virtue of probability density evolution method (PDEM......), which underlies the schemes of random vibration analysis and structural reliability assessment. The short-term rare failure probability of 5-mega-watt wind turbines, for illustrative purposes, in case of given mean wind speeds and turbulence levels is investigated through the scheme of extreme value...... distribution instead of any other approximate schemes of fitted distribution currently used in statistical extrapolation techniques. Besides, the comparative studies against the classical fitted distributions and the standard Monte Carlo techniques are carried out. Numerical results indicate that PDEM exhibits...

The selective dynamical downscaling method for extreme-wind atlases

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Badger, Jake; Hahmann, Andrea N.

2012-01-01

A selective dynamical downscaling method is developed to obtain extreme-wind atlases for large areas. The method is general, efficient and flexible. The method consists of three steps: (i) identifying storm episodes for a particular area, (ii) downscaling of the storms using mesoscale modelling...... and (iii) post-processing. The post-processing generalizes the winds from the mesoscale modelling to standard conditions, i.e. 10-m height over a homogeneous surface with roughness length of 5 cm. The generalized winds are then used to calculate the 50-year wind using the annual maximum method for each...... mesoscale grid point. The generalization of the mesoscale winds through the post-processing provides a framework for data validation and for applying further the mesoscale extreme winds at specific places using microscale modelling. The results are compared with measurements from two areas with different...

Experimental investigation of ultimate loads

Energy Technology Data Exchange (ETDEWEB)

Petersen, S M; Larsen, G C; Antoniou, I; Lind, S O; Courtney, M [Risoe National Lab., Wind Energy and Atmospheric Physics, Roskilde (Denmark)

1999-03-01

Verification of the structural integrity of a wind turbine involves analysis of fatigue loading as well as ultimate loading. With the trend of persistently growing turbines, the ultimate loading seems to become relatively more important. For wind turbines designed according to the wind conditions prescribed in the IEC-61400 code, the ultimate load is often identified as the leading load parameter. Exemplified by the use of an extensive measurement campaign a procedure for evaluation of the extreme flap-wise bending moments, occurring during normal operating of a wind turbine, is presented. The structural measurements are made on a NEG Micon 650 kW wind turbine erected at a complex high wind site in Oak Creek, California. The turbine is located on the top of a ridge. The prevailing wind direction is perpendicular to the ridge, and the annual mean wind speed is 9.5 m/s. The associated wind field measurement, are taken from two instrumented masts erected less than one rotor diameter in front of the turbine in direction of the prevailing wind direction. Both masts are instrumented at different heights in order to gain insight of the 3D-wind speed structure over the entire rotor plane. Extreme distributions, associated with a recurrence period of 10 minutes, conditioned on the mean wind speed and the turbulence intensity are derived. Combined with the wind climate model proposed in the IEC standard, these distributions are used to predict extreme distributions with recurrence periods equal to one and fifty years, respectively. The synthesis of the conditioned PDF`s and the wind climate model is performed by means of Monte Carlo simulation. (au)

Outlier robustness for wind turbine extrapolated extreme loads

DEFF Research Database (Denmark)

Natarajan, Anand; Verelst, David Robert

2012-01-01

. Stochastic identification of numerical artifacts in simulated loads is demonstrated using the method of principal component analysis. The extrapolation methodology is made robust to outliers through a weighted loads approach, whereby the eigenvalues of the correlation matrix obtained using the loads with its...

Calculation of extreme wind atlases using mesoscale modeling. Final report

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Badger, Jake

This is the final report of the project PSO-10240 "Calculation of extreme wind atlases using mesoscale modeling". The overall objective is to improve the estimation of extreme winds by developing and applying new methodologies to confront the many weaknesses in the current methodologies as explai...

Load flow analysis for variable speed offshore wind farms

DEFF Research Database (Denmark)

Chen, Zhe; Zhao, Menghua; Blaabjerg, Frede

2009-01-01

factors such as the different wind farm configurations, the control of wind turbines and the power losses of pulse width modulation converters are considered. The DC/DC converter model is proposed and integrated into load flow algorithm by modifying the Jacobian matrix. Two iterative methods are proposed...... and integrated into the load flow algorithm: one takes into account the control strategy of converters and the other considers the power losses of converters. In addition, different types of variable speed wind turbine systems with different control methods are investigated. Finally, the method is demonstrated......A serial AC-DC integrated load flow algorithm for variable speed offshore wind farms is proposed. It divides the electrical system of a wind farm into several local networks, and different load flow methods are used for these local networks sequentially. This method is fast, more accurate, and many...

Wind load modeling for topology optimization of continuum structures

NARCIS (Netherlands)

Zakhama, R.; Abdalla, M.M.; Gürdal, Z.; Smaoui, H.

2010-01-01

Topology optimization of two and three dimensional structures subject to dead and wind loading is considered. The wind loading is introduced into the formulation by using standard expressions for the drag force, and a strategy is devised so that wind pressure is ignored where there is no surface

A final step towards the European wind loading code

NARCIS (Netherlands)

Staalduinen, P.C. van; Geurts, C.P.W.

1999-01-01

The process of the transition of national wind loading codes into a European Prestandard ENV 1991-2-4 for wind loading is being discussed. Backgrounds of this undertaking are being explained and specific technical issues to be resolved when drafting the final version of a European Standard for Wind

Wind load design methods for ground-based heliostats and parabolic dish collectors

Energy Technology Data Exchange (ETDEWEB)

Peterka, J A; Derickson, R G [Colorado State Univ., Fort Collins, CO (United States). Fluid Dynamics and Diffusion Lab.

1992-09-01

The purpose of this design method is to define wind loads on flat heliostat and parabolic dish collectors in a simplified form. Wind loads are defined for both mean and peak loads accounting for the protective influence of upwind collectors, wind protective fences, or other wind-blockage elements. The method used to define wind loads was to generalize wind load data obtained during tests on model collectors, heliostats or parabolic dishes, placed in a modeled atmospheric wind in a boundary-layer wind-tunnel at Colorado State University. For both heliostats and parabolic dishes, loads are reported for solitary collectors and for collectors as elements of a field. All collectors were solid with negligible porosity; thus the effects of porosity in the collectors is not addressed.

Preview-based Asymmetric Load Reduction of Wind Turbines

DEFF Research Database (Denmark)

Madsen, Mathias; Filsø, Jakob; Soltani, Mohsen

2012-01-01

Controller (MPC) developed is based on a model with individual blade pitching to utilize the LIDAR measurements. The MPC must also maintain a given power reference while satisfying a set of actuator constraints. The designed controller was tested on a 5 MW wind turbine in the FAST simulator and compared......Fatigue loads on wind turbines caused by an asymmetric wind field become an increasing concern when the scale of wind turbines increases. This paper presents a model based predictive approach to reduce asymmetric loads by using Light Detection And Ranging (LIDAR) measurements. The Model Predictive...

Load mitigation of unbalanced wind turbines using PI-R individual pitch control

DEFF Research Database (Denmark)

Zhang, Yunqian; Cheng, Ming; Chen, Zhe

2015-01-01

This study discusses the load mitigation of unbalanced wind turbines, including balanced and unbalanced loads. Regarding the wind turbine load reduction, it has been shown that individual pitch control (IPC) is more promising in comparison with collective pitch control. However, wind turbine......) controller and two resonant (R) compensators is presented. The PI-R regulator is implemented in the hub reference frame to reduce both the balanced and unbalanced loads of the turbine. The wind turbine code FAST (fatigue, aerodynamics, structures and turbulence) is used for the wind turbine load modelling....... The simulations are conducted on the NREL upwind 1.5 MW wind turbine model. Elimination of both the balanced and unbalanced loads of the wind turbine has been achieved, so that PI-R IPC is demonstrated as an effective means for load mitigation of unbalanced wind turbines....

Numerical simulation of wind loads on solar panels

Science.gov (United States)

Su, Kao-Chun; Chung, Kung-Ming; Hsu, Shu-Tsung

2018-05-01

Solar panels mounted on the roof of a building or ground are often vulnerable to strong wind loads. This study aims to investigate wind loads on solar panels using computational fluid dynamic (CFD). The results show good agreement with wind tunnel data, e.g. the streamwise distribution of mean surface pressure coefficient of a solar panel. Wind uplift for solar panels with four aspect ratios is evaluated. The effect of inclined angle and clearance (or height) of a solar panel is addressed. It is found that wind uplift of a solar panel increases when there is an increase in inclined angle and the clearance above ground shows an opposite effect.

Wind and load variability in the Nordic countries

DEFF Research Database (Denmark)

Holttinen, Hannele; Rissanen, Simo; Larsén, Xiaoli Guo

the three years analysed in this publication there were few storm incidents and they did not produce dramatic wind power ramps in the Nordic region. Wind and load variations are not correlated between the countries, which is beneficial from the viewpoint of wind integration. The smoothing effect is shown......This publication analysed the variability of wind production and load in Denmark, Finland, Sweden, and the Nordic region as a whole, based on real data measured from large-scale wind power during 2009–2011. The Nordic-wide wind power time series was scaled up such that Sweden had same amount...... of wind power production than Denmark, and Finland and Norway only 50% of the wind power production in Denmark. Wind power production in Denmark and Sweden is somewhat correlated (coefficient 0.7) but less correlation is found between the other countries. The variations from one hour to the next are only...

Wind inflow observation from load harmonics

OpenAIRE

Marta, Bertelè; Bottasso, Carlo L.; Cacciola, Stefano; Fabiano Daher Adegas,; Sara, Delport

2017-01-01

The wind field leaves its fingerprint on the rotor response. This fact can be exploited by using the rotor as a sensor: by looking at the rotor response, in the present case in terms of blade loads, one may infer the wind characteristics. This paper describes a wind state observer that estimates four wind parameters, namely the vertical and horizontal shears and the yaw and upflow misalignment angles, from out-of-plane and in-plane blade bending moments. The resulting observ...

Wind inflow observation from load harmonics

Directory of Open Access Journals (Sweden)

M. Bertelè

2017-12-01

Full Text Available The wind field leaves its fingerprint on the rotor response. This fact can be exploited by using the rotor as a sensor: by looking at the rotor response, in the present case in terms of blade loads, one may infer the wind characteristics. This paper describes a wind state observer that estimates four wind parameters, namely the vertical and horizontal shears and the yaw and upflow misalignment angles, from out-of-plane and in-plane blade bending moments. The resulting observer provides on-rotor wind inflow characteristics that can be exploited for wind turbine and wind farm control. The proposed formulation is evaluated through extensive numerical simulations in turbulent and nonturbulent wind conditions using a high-fidelity aeroservoelastic model of a multi-MW wind turbine.

Deterministic and Probabilistic Analysis of NPP Communication Bridge Resistance Due to Extreme Loads

Directory of Open Access Journals (Sweden)

Králik Juraj

2014-12-01

Full Text Available This paper presents the experiences from the deterministic and probability analysis of the reliability of communication bridge structure resistance due to extreme loads - wind and earthquake. On the example of the steel bridge between two NPP buildings is considered the efficiency of the bracing systems. The advantages and disadvantages of the deterministic and probabilistic analysis of the structure resistance are discussed. The advantages of the utilization the LHS method to analyze the safety and reliability of the structures is presented

Extreme pressure differences at 0900 NZST and winds across New Zealand

Science.gov (United States)

Salinger, M. James; Griffiths, Georgina M.; Gosai, Ashmita

2005-07-01

Trends in extremes in station daily sea-level pressure differences at 0900 NZST are examined, and extreme daily wind gusts, across New Zealand, since the 1960s. Annual time series were examined (with indices of magnitude and frequency over threshold percentiles) from the daily indices selected. These follow from earlier indices of normalized monthly mean sea-level pressure differences between station pairs, except the daily indices are not normalized. The frequency statistics quantify the number of extreme zonal (westerly and easterly), or extreme meridional (southerly or northerly), pressure gradient events. The frequency and magnitude of extreme westerly episodes has increased slightly over New Zealand, with a significant increase in the westerly extremes to the south of New Zealand. In contrast, the magnitude and frequency of easterly extremes has decreased over New Zealand, but increased to the south, with some trends weakly significant. The frequency and magnitude of daily southerly extremes has decreased significantly in the region.Extreme daily wind gust events at key climate stations in New Zealand and at Hobart, Australia, are highly likely to be associated with an extreme daily pressure difference. The converse was less likely to hold: extreme wind gusts were not always observed on days with extreme daily pressure difference, probably due to the strong influence that topography has on localized station winds. Significant correlations exist between the frequency indices and both annual-average mean sea-level pressures around the Australasian region and annual-average sea surface temperature (SST) anomalies in the Southern Hemisphere. These correlations are generally stronger for indices of extreme westerly or extreme southerly airflows. Annual-average pressures in the Tasman Sea or Southern Ocean are highly correlated to zonal indices (frequency of extreme westerlies). SST anomalies in the NINO3 region or on either side of the South Island are

Load prediction of stall regulated wind turbines

Energy Technology Data Exchange (ETDEWEB)

Bjoerck, A.; Dahlberg, J.Aa. [Aeronautical Research Inst. of Sweden, Bromma (Sweden); Carlen, I. [Chalmers Univ. of Technology, Goeteborg (Sweden). Div. of Marine Structural Engineering; Ganander, H. [Teknikgruppen AB, Sollentua (Sweden)

1996-12-01

Measurements of blade loads on a turbine situated in a small wind farm shows that the highest blade loads occur during operation close to the peak power i.e. when the turbine operates in the stall region. In this study the extensive experimental data base has been utilised to compare loads in selected campaigns with corresponding load predictions. The predictions are based on time domain simulations of the wind turbine structure, performed by the aeroelastic code VIDYN. In the calculations a model were adopted in order to include the effects of dynamic stall. This paper describes the work carried out so far within the project and key results. 5 refs, 10 figs

Wind effects on long-span bridges: Probabilistic wind data format for buffeting and VIV load assessments

Science.gov (United States)

Hoffmann, K.; Srouji, R. G.; Hansen, S. O.

2017-12-01

The technology development within the structural design of long-span bridges in Norwegian fjords has created a need for reformulating the calculation format and the physical quantities used to describe the properties of wind and the associated wind-induced effects on bridge decks. Parts of a new probabilistic format describing the incoming, undisturbed wind is presented. It is expected that a fixed probabilistic format will facilitate a more physically consistent and precise description of the wind conditions, which in turn increase the accuracy and considerably reduce uncertainties in wind load assessments. Because the format is probabilistic, a quantification of the level of safety and uncertainty in predicted wind loads is readily accessible. A simple buffeting response calculation demonstrates the use of probabilistic wind data in the assessment of wind loads and responses. Furthermore, vortex-induced fatigue damage is discussed in relation to probabilistic wind turbulence data and response measurements from wind tunnel tests.

Comparison of loads for wind turbine down-regulation strategies

DEFF Research Database (Denmark)

Zhu, Jiangsheng; Ma, Kuichao; N. Soltani, Mohsen

2017-01-01

For wind farm active power setpoint tracking, both farm level and turbine level down regulation strategies should to be optimized. Several down regulation strategies are chosen to analyse the wind turbine load performance according to different wind speed and power reference. In this paper we...... suggest appropriate down regulation strategy to control wind turbine for active power reference tracking. we compare four different control strategies, namely Const-Ω, Const-λ, Max-Ω and Min-Ct and discuss the loads on main components and downwind speed by presenting analysis of several wind scenarios...

The nature of wind turbine fatigue loads in wind farms

DEFF Research Database (Denmark)

Larsen, Gunner Chr.; Larsen, Torben J.; Aagaard Madsen, Helge

2013-01-01

The aim of the present paper is to further validate the predictive capability of the DWM/HAWC2 package for simulation of structural loadings in wind farms. The validation in particular focus on tower fatigue loading characteristics (i.e. equivalent moments) as function of turbine relative positio...

A new simulation method for turbines in wake - Applied to extreme response during operation

DEFF Research Database (Denmark)

Thomsen, K.; Aagaard Madsen, H.

2005-01-01

The work focuses on prediction of load response for wind turbines operating in wind forms using a newly developed aeroelostic simulation method The traditionally used concept is to adjust the free flow turbulence intensity to account for increased loads in wind farms-a methodology that might......, the resulting extremes might be erroneous. For blade loads the traditionally used simplified approach works better than for integrated rotor loads-where the instantaneous load gradient across the rotor disc is causing the extreme loads. In the article the new wake simulation approach is illustrated...

Wind loads on solar energy roofs

NARCIS (Netherlands)

Geurts, C.P.W.; Bentum, C.A. van

2007-01-01

This paper presents an overview of the wind loads on roofs, equipped with solar energy products, so called Active Roofs. Values given in this paper have been based on wind tunnel and full scale measurements, carried out at TNO, and on an interpretation of existing rules and guidelines. The results

Effects of Icing on Wind Turbine Fatigue Loads

International Nuclear Information System (INIS)

Frohboese, Peter; Anders, Andreas

2007-01-01

The external conditions occurring at cold climate sites will affect wind turbines in different ways. The effects of ice accretion on wind turbines and the influence on the turbine fatigue loads are examined. The amount of icing prior to turbine installation needs to be estimated by using standard measurement data and considering the geometry of the proposed turbine. A procedure to calculate the expected ice accretion on wind turbines out of standard measurement data is explained and the results are discussed. Different parameters to describe the accreted ice on the turbine are examined separately in a fatigue load calculation. The results of the fatigue load calculation are discussed and selected cases are presented

Study on Determination Method of Fatigue Testing Load for Wind Turbine Blade

Science.gov (United States)

Liao, Gaohua; Wu, Jianzhong

2017-07-01

In this paper, the load calculation method of the fatigue test was studied for the wind turbine blade under uniaxial loading. The characteristics of wind load and blade equivalent load were analyzed. The fatigue property and damage theory of blade material were studied. The fatigue load for 2MW blade was calculated by Bladed, and the stress calculated by ANSYS. Goodman modified exponential function S-N curve and linear cumulative damage rule were used to calculate the fatigue load of wind turbine blades. It lays the foundation for the design and experiment of wind turbine blade fatigue loading system.

A review of the wind loading zones for flat roofs in code provisions

NARCIS (Netherlands)

Geurts, C.P.W.; Kopp, G.A.; Morrison, M.J.

2013-01-01

The provisions for wind loads on flat roofs differ considerably between current wind loading standards in different jurisdictions. For a number of major wind loading codes, both the definition of roof zones, and the values applied to determine the wind loads are discussed. This paper concentrates on

A Wind Farm Controller for Load and Power Optimization in a Farm

DEFF Research Database (Denmark)

Soleimanzadeh, Maryam; Brand, Arno; Wisniewski, Rafal

2011-01-01

This paper describes the design procedure of an optimal wind farm controller. The controller optimizes the structural load and power production simultaneously, on the basis of an analytical wind farm model. The farm model delivers maps of wind, loads and energy in the wind farm. Moreover, the model...... computes the wind speed at the turbines, turbine bending moments and aerodynamic power and torque. The optimal control problem is formulated based on the model for two different wind directions. The controller determines the reference signals for each individual wind turbine controller in two scenarios...... based on low and high wind speed. In low wind speed, the reference signals for rotor speed are adjusted, taking the trade-off between power maximization and load minimization into account. In high wind speed, the power and pitch angle reference signals are determined while structural loads are minimized....

Spatial reliability analysis of a wind turbine blade cross section subjected to multi-axial extreme loading

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov; Bitsche, Robert; Blasques, José Pedro Albergaria Amaral

2017-01-01

This paper presents a methodology for structural reliability analysis of wind turbine blades. The study introduces several novel elements by taking into account loading direction using a multiaxial probabilistic load model, considering random material strength, spatial correlation between material...... properties, progressive material failure, and system reliability effects. An example analysis of reliability against material failure is demonstrated for a blade cross section. Based on the study we discuss the implications of using a system reliability approach, the effect of spatial correlation length......, type of material degradation algorithm, and reliability methods on the system failure probability, as well as the main factors that have an influence on the reliability. (C) 2017 Elsevier Ltd. All rights reserved....

Extreme wind conditions for a Danish offshore site

DEFF Research Database (Denmark)

Hansen, Kurt S.

2000-01-01

This paper presents an analysis of extreme wind speed gust values measured at a shallow water offshore site and at a coastal onshore site in Denmark. An estimate of 50-year extreme values has been evaluated using a new statistical method. In addition a mean gust shape is determined, based on a la...

Effects of gain-scheduling methods in a classical wind turbine controller on wind turbine aeroservoelastic modes and loads

DEFF Research Database (Denmark)

Tibaldi, Carlo; Henriksen, Lars Christian; Hansen, Morten Hartvig

2014-01-01

The eects of dierent gain-scheduling methods for a classical wind turbine controller, operating in full load region, on the wind turbine aeroservoelastic modes and loads are investigated in this work. The dierent techniques are derived looking at the physical problem to take into account the chan......The eects of dierent gain-scheduling methods for a classical wind turbine controller, operating in full load region, on the wind turbine aeroservoelastic modes and loads are investigated in this work. The dierent techniques are derived looking at the physical problem to take into account...

Load and Flicker Mitigation of Grid-Connected Wind Turbines with DFIG

DEFF Research Database (Denmark)

Zhang, Yunqian

power will result in the flicker emission in the power network, causing consumer annoyance and complaint. These issues make the study on the wind turbine load reduction and the flicker mitigation necessary and imperative. The research documented in this thesis addresses wind turbine load reduction under...... both balanced and unbalanced conditions and flicker mitigation issues of wind turbines system. To reduce the wind turbine loads, PI control based individual pitch control (IPC) scheme is presented. The PI IPC scheme is developed to reduce not only the loads on the blade, but also the loads on the rotor...... the balanced loads but also the unbalanced loads. Flicker emission which is harmful to the power system is induced by voltage fluctuations which are caused by load flow changes in the grid. One way for flicker mitigation is to reduce the power fluctuation from the fluctuation source. Individual pitch control...

Comparative analysis of methods for modelling the short-term probability distribution of extreme wind turbine loads

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov

2016-01-01

We have tested the performance of statistical extrapolation methods in predicting the extreme response of a multi-megawatt wind turbine generator. We have applied the peaks-over-threshold, block maxima and average conditional exceedance rates (ACER) methods for peaks extraction, combined with four...... levels, based on the assumption that the response tail is asymptotically Gumbel distributed. Example analyses were carried out, aimed at comparing the different methods, analysing the statistical uncertainties and identifying the factors, which are critical to the accuracy and reliability...

Normal and Extreme Wind Conditions for Power at Coastal Locations in China.

Science.gov (United States)

Gao, Meng; Ning, Jicai; Wu, Xiaoqing

2015-01-01

In this paper, the normal and extreme wind conditions for power at 12 coastal locations along China's coastline were investigated. For this purpose, the daily meteorological data measured at the standard 10-m height above ground for periods of 40-62 years are statistically analyzed. The East Asian Monsoon that affects almost China's entire coastal region is considered as the leading factor determining wind energy resources. For most stations, the mean wind speed is higher in winter and lower in summer. Meanwhile, the wind direction analysis indicates that the prevalent winds in summer are southerly, while those in winter are northerly. The air densities at different coastal locations differ significantly, resulting in the difference in wind power density. The Weibull and lognormal distributions are applied to fit the yearly wind speeds. The lognormal distribution performs better than the Weibull distribution at 8 coastal stations according to two judgement criteria, the Kolmogorov-Smirnov test and absolute error (AE). Regarding the annual maximum extreme wind speed, the generalized extreme value (GEV) distribution performs better than the commonly-used Gumbel distribution. At these southeastern coastal locations, strong winds usually occur in typhoon season. These 4 coastal provinces, that is, Guangdong, Fujian, Hainan, and Zhejiang, which have abundant wind resources, are also prone to typhoon disasters.

Performance Enhancement and Load Reduction on Wind Turbines Using Inflow Measurements

DEFF Research Database (Denmark)

Kragh, Knud Abildgaard

. The load variations on a wind turbine can be alleviated using either yaw or pitch actuation. A method is presented for alleviating load variations using yaw control, and it is shown how the method can be efficiently applied for decreasing the load variations that are caused by a vertical wind shear...... wind energy research is focused on decreasing the cost of the energy that can be produced from the wind. The cost of energy can for example be decreased by ensuring that wind turbines are operated in a way that ensures that the maximum amount of energy is extracted, and that the turbines are not loaded...... excessively. The operation of a wind turbine is governed by a number of controllers that are based on a series of sensors and actuators. Classical wind turbine control utilizes sensors for measuring turbine parameters such as rotor speed, power and shaft torque, as well as actuators for applying generator...

Wind turbine optimal control during storms

International Nuclear Information System (INIS)

Petrović, V; Bottasso, C L

2014-01-01

This paper proposes a control algorithm that enables wind turbine operation in high winds. With this objective, an online optimization procedure is formulated that, based on the wind turbine state, estimates those extremal wind speed variations that would produce maximal allowable wind turbine loads. Optimization results are compared to the actual wind speed and, if there is a danger of excessive loading, the wind turbine power reference is adjusted to ensure that loads stay within allowed limits. This way, the machine can operate safely even above the cut-out wind speed, thereby realizing a soft envelope-protecting cut-out. The proposed control strategy is tested and verified using a high-fidelity aeroservoelastic simulation model

Potential of Offshore Wind Energy and Extreme Wind Speed Forecasting on the West Coast of Taiwan

Directory of Open Access Journals (Sweden)

Pei-Chi Chang

2015-02-01

Full Text Available It is of great importance and urgency for Taiwan to develop offshore wind power. However, relevant data on offshore wind energy resources are limited. This study imported wind speeds measured by a tidal station and a buoy into the software WAsP to estimate the high-altitude wind speeds in the two areas. A light detection and ranging (Lidar system was set up near the tidal station and buoy. High-altitude wind speeds measured by the Lidar system were compared with the WAsP-estimated values, and it was discovered that the two data sets were consistent. Then, long-term wind speed data observed by buoys and tidal stations at various locations were imported into WAsP to forecast wind speeds at heights of 55–200 m on the west coast of Taiwan. The software WAsP Engineering was used to analyze the extreme wind speeds in the same areas. The results show that wind speeds at 100 m are approximately 9.32–11.24 m/s, which means that the coastal areas of west Taiwan are rich in wind energy resources. When a long-term 10-min average wind speed is used, the extreme wind speed on the west coast is estimated to be between 36.4 and 55.3 m/s.

Statistical Model of Extreme Shear

DEFF Research Database (Denmark)

Hansen, Kurt Schaldemose; Larsen, Gunner Chr.

2005-01-01

In order to continue cost-optimisation of modern large wind turbines, it is important to continuously increase the knowledge of wind field parameters relevant to design loads. This paper presents a general statistical model that offers site-specific prediction of the probability density function...... by a model that, on a statistically consistent basis, describes the most likely spatial shape of an extreme wind shear event. Predictions from the model have been compared with results from an extreme value data analysis, based on a large number of full-scale measurements recorded with a high sampling rate...

A Two-Bladed Concept Wind Turbine

DEFF Research Database (Denmark)

Kim, Taeseong

2012-01-01

This article shows the potential for reducing extreme loads with an innovative design of wind turbine, a partial pitch two-bladed concept turbine. The most extreme conditions to test a turbine are considered to be stand-still combined with a grid failure in which the wind comes from all directions...

AC-DC integrated load flow calculation for variable speed offshore wind farms

DEFF Research Database (Denmark)

Zhao, Menghua; Chen, Zhe; Blaabjerg, Frede

2005-01-01

This paper proposes a sequential AC-DC integrated load flow algorithm for variable speed offshore wind farms. In this algorithm, the variable frequency and the control strategy of variable speed wind turbine systems are considered. In addition, the losses of wind turbine systems and the losses...... of converters are also integrated into the load flow algorithm. As a general algorithm, it can be applied to different types of wind farm configurations, and the load flow is related to the wind speed....

Fatigue Load Sensitivity Based Optimal Active Power Dispatch For Wind Farms

DEFF Research Database (Denmark)

Zhao, Haoran; Wu, Qiuwei; Huang, Shaojun

2017-01-01

This paper proposes an optimal active power dispatch algorithm for wind farms based on Wind Turbine (WT) load sensitivity. The control objectives include tracking power references from the system operator and minimizing fatigue loads experienced by WTs. The sensitivity of WT fatigue loads to power...... sensitivity are derived, which significantly improves the computation efficiency of the local WT controller. The proposed algorithm can be implemented in different active power control schemes. Case studies were conducted with a wind farm under balance control for both low and high wind conditions...

Individual pitch control of NREL 5MW wind turbine blade for load reduction

International Nuclear Information System (INIS)

La, Yo Han; Nam, Yoon Su; Hoon, Son Jae

2012-01-01

As the size of a wind turbine increases, the rotor diameter increases. Rotor blades experience mechanical loads caused by the wind shear and the tower shadow effect. These mechanical loads reduce the life of the wind turbine. Therefore, with increasing size of the wind turbine, wind turbine control system design for the mitigation of mechanical loads is important. In this study, Individual Pitch Control in introduced for reducing the mechanical loads of rotor blades, and a simulation for IPC performance verification is discussed

Dependence of offshore wind turbine fatigue loads on atmospheric stratification

International Nuclear Information System (INIS)

Hansen, K S; Larsen, G C; Ott, S

2014-01-01

The stratification of the atmospheric boundary layer (ABL) is classified in terms of the M-O length and subsequently used to determine the relationship between ABL stability and the fatigue loads of a wind turbine located inside an offshore wind farm. Recorded equivalent fatigue loads, representing blade-bending and tower bottom bending, are combined with the operational statistics from the instrumented wind turbine as well as with meteorological statistics defining the inflow conditions. Only a part of all possible inflow conditions are covered through the approximately 8200 hours of combined measurements. The fatigue polar has been determined for an (almost) complete 360° inflow sector for both load sensors, representing mean wind speeds below and above rated wind speed, respectively, with the inflow conditions classified into three different stratification regimes: unstable, neutral and stable conditions. In general, impact of ABL stratification is clearly seen on wake affected inflow cases for both blade and tower fatigue loads. However, the character of this dependence varies significantly with the type of inflow conditions – e.g. single wake inflow or multiple wake inflow

Monitoring fatigue loads on wind turbines using cycle counting data acquisition systems

Energy Technology Data Exchange (ETDEWEB)

Soeker, H; Seifert, H [Deutsches Windenergie-Institut (Germany); Fragoulis, A; Vionis, P; Foussekis, D [Center for Renewable Energy Sources (Greece); Dahlberg, J A; Poppen, M [The Aeronautical Research Institue of Sweden (Sweden)

1996-09-01

As in any industrial application, the duration of a wind turbine`s life is a key parameter for the evaluation of its economic potential. Assuming a service life of 20 years, components of the turbine have to withstand a number of load cycles of up to 10{sup 8}. Such numbers of load cycles impose high demands on the fatigue characteristics of both, the used materials and the design. Nevertheless, fatigue loading of wind turbine components still remains a parameter of high uncertainty in the design of wind turbines. The specific features of these fatigue loads can be expected to vary with the type of turbine and the site of operation. In order to ensure the reliability of the next generation of larger scale wind turbines improved load assumptions will be of vital importance. Within the scope of the presented research program DEWI, C.R.E.S. and FFA monitored fatigue loads of serial produced wind turbines by means of a monitoring method that uses on-line cycle counting techniques. The blade root bending moments of two pitch controlled, variable speed wind turbines operating in the Hamswehrum wind farm, and also that of a stall controlled, fixed speed wind turbine operating in CRES` complex terrain test site, were measured by DEWI and CRES. In parallel FFA used their database of time series measurements of blade root bending moments on a stall controlled, fixed speed turbine at Alsvik Windfarm in order to derive semi-empirical fatigue load data. The experience gained from application of the on-line measurement technique is discussed with respect to performance, data quality, reliability and cost effectiveness. Investigations on the effects of wind farm and complex terrain operation on the fatigue loads of wind turbine rotor blades are presented. (au)

Grid faults' impact on wind turbine structural loads

Energy Technology Data Exchange (ETDEWEB)

Hansen, A.D.; Cutululis, N.A.; Soerensen, P.; Larsen, T.J. [Risoe National Lab., DTU, Wind Energy Dept. (Denmark); Iov, F.

2007-11-15

The objective of this work is to illustrate the impact of the grid faults on the wind turbine structural loads. Grid faults are typically in detailed power system simulation tools, which by applying simplified mechanical models, are not able to provide a throughout insight on the structural loads caused by sudden disturbances on the grid. On the other hand, structural loads of the wind turbine are typically assessed in advanced aeroelastic computer codes, which by applying simplified electrical models do not provide detailed electrical insight. This paper presents a simulation strategy, where the focus is on how to access a proper combination of two complementary simulation tools, such as the advanced aeroelastic computer code HAWC2 and the detailed power system simulation tool DIgSILENT, in order to provide a whole overview of both the structural and the electrical behaviour of the wind turbine during grid faults. The effect of a grid fault on the wind turbine flexible structure is assessed for a typical fixed speed wind turbine, equipped with an induction generator. (au)

Extreme wind-wave modeling and analysis in the south Atlantic ocean

Science.gov (United States)

Campos, R. M.; Alves, J. H. G. M.; Guedes Soares, C.; Guimaraes, L. G.; Parente, C. E.

2018-04-01

A set of wave hindcasts is constructed using two different types of wind calibration, followed by an additional test retuning the input source term Sin in the wave model. The goal is to improve the simulation in extreme wave events in the South Atlantic Ocean without compromising average conditions. Wind fields are based on Climate Forecast System Reanalysis (CFSR/NCEP). The first wind calibration applies a simple linear regression model, with coefficients obtained from the comparison of CFSR against buoy data. The second is a method where deficiencies of the CFSR associated with severe sea state events are remedied, whereby "defective" winds are replaced with satellite data within cyclones. A total of six wind datasets forced WAVEWATCH-III and additional three tests with modified Sin in WAVEWATCH III lead to a total of nine wave hindcasts that are evaluated against satellite and buoy data for ambient and extreme conditions. The target variable considered is the significant wave height (Hs). The increase of sea-state severity shows a progressive increase of the hindcast underestimation which could be calculated as a function of percentiles. The wind calibration using a linear regression function shows similar results to the adjustments to Sin term (increase of βmax parameter) in WAVEWATCH-III - it effectively reduces the average bias of Hs but cannot avoid the increase of errors with percentiles. The use of blended scatterometer winds within cyclones could reduce the increasing wave hindcast errors mainly above the 93rd percentile and leads to a better representation of Hs at the peak of the storms. The combination of linear regression calibration of non-cyclonic winds with scatterometer winds within the cyclones generated a wave hindcast with small errors from calm to extreme conditions. This approach led to a reduction of the percentage error of Hs from 14% to less than 8% for extreme waves, while also improving the RMSE.

Wind loads on post-panamax container ship

DEFF Research Database (Denmark)

Andersen, Ingrid Marie Vincent

2013-01-01

An investigation of the influence of the container configuration on the deck of a 9000+ TEU container ship on wind forces has been carried out through a series of wind tunnel tests with a 1:450 scale model. An analysis of earlier studies was used to select a series of appropriate loading conditions...

An Optimization Framework for Load and Power Distribution in Wind Farms

DEFF Research Database (Denmark)

Soleimanzadeh, Maryam; Wisniewski, Rafal; Kanev, Stoyan

2012-01-01

The aim of this paper is to develop a controller for wind farms to optimize the load and power distribution. In this regard, the farm controller calculates the power reference signals for individual wind turbine controllers such that the sum of the power references tracks the power demanded...... by a system operator. Moreover, the reference signals are determined to reduce the load acting on wind turbines at low frequencies. Therefore, a trade-off is made for load and power control, which is formulated as an optimization problem. Afterwards, the optimization problem for the wind farm modeled...

Extreme winds in the Western North Pacific

DEFF Research Database (Denmark)

Ott, Søren

2006-01-01

satellite images is discussed with emphasis on the empirical basis, which, unfortunately, is not very strong. This is stressed by the fact that Japanese and US agencies arrive at markedly different estimates. Onthe other hand, best track data records cover a long period of time and if not perfect......A statistical model for extreme winds in the western North Pacific is developed, the region on the Planet where tropical cyclones are most common. The model is based on best track data derived mostly from satellite images of tropical cyclones. The methodsused to estimate surface wind speeds from...... they are at least coherent over time in their imperfections. Applying the the Holland model to the best track data, wind profiles can be assigned along the tracks. Fromthis annual wind speed maxima at any particular point in the region can be derived. The annual maxima, in turn, are fitted to a Gumbel distribution...

Rational Calibration of Four IEC 61400-1 Extreme External Conditions

DEFF Research Database (Denmark)

Larsen, Gunner Chr.; Hansen, Kurt Schaldemose

2008-01-01

Based on a set of asymptotic statistical models on closed form this paper presents a rational and consistent calibration of four extreme external conditions defined in the International Electrotechnical Commission (IEC) 61400-1 standard: extreme operating gust, extreme wind shear, extreme coheren...... and proposed specifications of the magnitudes of the extreme external wind conditions are highlighted and discussed using an illustrative example based on two selected terrain types. Copyright © 2008 John Wiley & Sons, Ltd....... gust with direction change and extreme wind direction change. These four extreme external conditions are used in the definition of six of the IEC 61400-1 ultimate load cases. The statistical models are based on simple and easily accessible mean wind speed and turbulence characteristics...

Assessment of the impact of frequency support on DFIG wind turbine loads

DEFF Research Database (Denmark)

Barahona Garzón, Braulio; You, Rui; Hansen, Anca Daniela

2013-01-01

This study presents models and tools for the assessment of the impact that providing frequency support has on doubly-fed generator (DFIG) wind turbine structural loads and drive train. The focus is on primary frequency support, aiming at quantifying the impact on wind turbines acting as frequency...... code and electrical models. In this simulation framework, the impact that power system conditions can have on wind turbines, and vice versa the support that wind turbines can offer to the power system can be investigated....... containment reserve and providing inertial response. The sensitivity of wind turbine load indicators—load duration- distribution and maximum load values—to inertial response control actions and different torsional models of drive train is investigated. The analysis is done by co-simulations of an aeroelastic...

Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

DEFF Research Database (Denmark)

Pedersen, Mads M.; Larsen, Torben J.; Madsen, Helge Aa

2017-01-01

In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can...... be performed from a few hours or days of measurements. In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup...... anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation...

Extreme wind atlases of South Africa from global reanalysis data

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Kruger, Andries; Badger, Jake

2013-01-01

Extreme wind atlases of South Africa were developed using three reanalysis data and recently developed approaches. The results are compared with the maps produced using standard wind measurements over the region. It was found that different reanalyses with the same approach provide similar spatia...

Fatigue load reductions in co-located wind-wave arrays

DEFF Research Database (Denmark)

Clark, Caitlyn; Velarde, Joey; Nielsen, Jannie Sønderkær

2018-01-01

As offshore wind turbines (OWTs) increase in size and are placed farther offshore, hydrodynamic loads have increased contribution to total load, resulting in fatigue limit states becoming more important to consider in structural design. Previous literature shows that placing wave energy converters...... is investigated. A method for quantifying relative sea state reductions from WECs are applied, and fully-coupled time-domain fatigue analyses are performed for a 10 MW reference offshore wind turbine. Results indicate that a single WEC and a WEC array can lead to 8% and 10% fatigue load reduction, respectively....

Reducing Turbine Mechanical Loads Using Flow Model-Based Wind Farm Controller

DEFF Research Database (Denmark)

Kazda, Jonas; Cutululis, Nicolaos Antonio

Cumulated O&M costs of offshore wind farms are comparable with wind turbine CAPEX of such wind farm. In wind farms, wake effects can result in up to 80% higher fatigue loads at downstream wind turbines [1] and consequently larger O&M costs. The present work therefore investigates to reduce...... these loads during the provision of grid balancing services using optimal model-based wind farm control. Wind farm controllers coordinate the operating point of wind turbines in a wind farm in order to achieve a given objective. The investigated objective of the control in this work is to follow a total wind...... farm power reference while reducing the tower bending moments of the turbines in the wind farm. The wind farm controller is tested on a 8 turbine array, which is representative of a typical offshore wind farm. The operation of the wind farm is simulated using the dynamic wind farm simulation tool S imWind...

Stochastic Extreme Load Predictions for Marine Structures

DEFF Research Database (Denmark)

Jensen, Jørgen Juncher

1999-01-01

Development of rational design criteria for marine structures requires reliable estimates for the maximum wave-induced loads the structure may encounter during its operational lifetime. The paper discusses various methods for extreme value predictions taking into account the non-linearity of the ......Development of rational design criteria for marine structures requires reliable estimates for the maximum wave-induced loads the structure may encounter during its operational lifetime. The paper discusses various methods for extreme value predictions taking into account the non......-linearity of the waves and the response. As example the wave-induced bending moment in the ship hull girder is considered....

Multivariate Modelling of Extreme Load Combinations for Wind Turbines

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov

2015-01-01

into a periodic part and a perturbation term, where each part has a known probability distribution. The proposed model shows good agreement with simulated data under stationary conditions, and a design load envelope based on this model is comparable to the load envelope estimated using the standard procedure...

Behavior of a nuclear power plant ventilation stack for wind loads

International Nuclear Information System (INIS)

Venkatachalapathy, V.

2012-01-01

This paper describes behavior of self supporting tall reinforced concrete (RC) ventilation stack of a nuclear power plant (NPP) for wind loads. Since the static and equivalent dynamic wind loads are inter-dependant on overall size of the stack, proper sizing of the stack geometry is important for reducing wind loads. The present study investigated the influence of engineered backfill soil on lateral response of ventilation stack. Ignoring backfill soil stiffness up to ground height does not allow to predict actual critical wind velocity causing across wind oscillation. The results show that proposed modification in the stack geometry modeled using 2D beam-spring elements is economical than that of single tapered geometry. Shaft diameter reduced in the proposed geometry indicates that there is a scope for overall space savings in the NPP layout. (author)

Load calculation methods for offshore wind turbine foundations

DEFF Research Database (Denmark)

Passon, Patrik; Branner, Kim

2014-01-01

Calculation of design loads for offshore wind turbine (OWT) foundations is typically performed in a joint effort between wind turbine manufactures and foundation designers (FDs). Ideally, both parties would apply the same fully integrated design tool and model for that purpose. However, such solu...

Assessment of wind turbine drive-train fatigue loads under torsional excitation

DEFF Research Database (Denmark)

Gallego Calderon, Juan Felipe; Natarajan, Anand

2015-01-01

allows the computation of the bearing and gear-mesh loads. The proposed models are validated by experiments from a 750 kW test-rig. The drive-train model is configured for a 5 MW power capacity and coupled to the corresponding wind turbine and load simulations are carried out under turbulent wind...... model is used in comparison to a simplified approach for load calculation. It is found that some of the wind turbine modes can have negative consequences on the life-time of the planetary bearings. © 2015 Elsevier Ltd. All rights reserved....

Along-wind response of a wind turbine tower with blade coupling subjected to rotationally sampled wind loading

Energy Technology Data Exchange (ETDEWEB)

Murtagh, P J; Basu, B; Broderick, B M [Department of Civil, Structural and Environmental Engineering, Trinity College, Dublin (Ireland)

2005-07-15

This paper proposes an approach to investigate the along-wind forced vibration response of a wind turbine tower and rotating blades assembly subjected to rotationally sampled stationary wind loading. The wind turbine assembly consists of three rotating rotor blades connected to the top of a flexible annular tower, constituting a multi-body dynamic entity. The tower and rotating blades are each modelled as discretized multi-degree-of-freedom (MDOF) entities, allowing the free vibration characteristics of each to be obtained using a discrete parameter approach. The free vibration properties of the tower include the effect of a rigid mass at the top, representing the nacelle, and those of the blade include the effects of centrifugal stiffening due to rotation and blade gravity loadings. The blades are excited by drag force time-histories derived from discrete Fourier transform (DFT) representations of rotationally sampled wind turbulence spectra. Blade response time-histories are obtained using the mode acceleration method, which allows for the quantification of base shear forces due to flapping for the three blades to be obtained. This resultant base shear is imparted into the top of the tower. Wind drag loading on the tower is also considered, with a series of spatially correlated nodal force time-histories being derived using DFTs of wind force spectra. The tower/nacelle is then coupled with the rotating blades by combining their equations of motion and solving for the displacement at the top of the tower under compatibility conditions in the frequency domain. An inverse Fourier transform of the frequency domain response yields the response time-history of the coupled system. The response of an equivalent system that does not consider the blade/tower interaction is also investigated, and the results are compared. (Author)

Simulation of wind loads on facades - Out in the wind; Simulation von Windlasten auf Fassaden. Vom Winde umstroemt

Energy Technology Data Exchange (ETDEWEB)

Menti, U.-P.; Pluess, I.

2007-07-01

This illustrated article discusses the wind loads experienced by buildings at exposed locations and, in particular, the correct design of their facades. The various numerical methods such as computational fluid dynamics (CFD) available for this purpose are introduced and explained. The validation of the models is discussed and the simulation of wind loads on the new revolving restaurant on the Hohe Kasten mountain in eastern Switzerland is looked at. Here winds with speeds of up to 250 km/h from various directions can be expected. Illustrations are provided of the results obtained. Practical results obtained from the simulations such as the design of the building's facades and the correct placing of air vents are presented and discussed.

Loads on Wind Turbines Access Platforms with Gratings

DEFF Research Database (Denmark)

Andersen, Thomas Lykke; Frigaard, Peter; Rasmussen, Michael R.

2011-01-01

The present paper deals with loads on wind turbine access platforms. The many planned new wind turbine parks together with the observed damages on platforms in several existing parks make the topic very important. The paper gives an overview of recently developed design formulae for different types...

Model predictive control of trailing edge flaps on a wind turbine blade

DEFF Research Database (Denmark)

Castaignet, Damien Bruno

of the wind turbine fatigue and extreme loads. This potential was confirmed with wind tunnel tests made on blade sections with trailing edge flaps and on a scaled two-bladed wind turbine in a wind tunnel. The work presented in this thesis includes a full-scale test run on a Vestas V27 wind turbine equipped...... fatigue loads by 23%, but also the main shaft and the tower fatigue loads by up to 32%. Extreme loads during normal production also benefit from the trailing edge flaps. At last, the same controller was run on the Vestas V27 wind turbine located at the Risø Campus of the Technical University of Denmark......Trailing edge flaps on wind turbine blades have been investigated for several years. Aero-servoelastic simulations carried out with different simulation tools, trailing edge flaps configurations and controller designs proved that trailing edge flaps are a suitable solution for reducing some...

Participation of Flexible Loads in Load Frequency Control to Support High Wind Penetration

DEFF Research Database (Denmark)

Uslu, Umur; Zhang, Boyang; Pillai, Jayakrishnan Radhakrishna

2016-01-01

The increasing amount of fluctuating wind power penetration in power systems presents many challenges to its operation and control. The new wind power plants are replacing many of the conventional large power plants that ensure power balancing and ancillary services for stable and reliable...... operation of the grid. Therefore, new solutions for power balancing reserves have to be explored and utilized by the grid utilities. To meet these challenges, large sizable loads like alkaline electrolysers, heat pumps and electric vehicles which are gaining popularity can provide system support to the grid...... through their inherent flexibility and energy storage characteristics. This paper investigates the possibilities and potential of such flexible loads to participate in power system frequency regulation in a wind dominated power system. The results show that these consumption units provide better...

Wind integration in self-regulating electric load distributions

Energy Technology Data Exchange (ETDEWEB)

Parkinson, Simon; Wang, Dan; Crawford, Curran; Djilali, Ned [University of Victoria, Department of Mechanical Engineering, Institute for Integrated Energy Systems, STN CSC, Victoria, BC (Canada)

2012-12-15

The purpose of this paper is to introduce and assess an alternative method of mitigating short-term wind energy production variability through the control of electric loads. In particular, co-located populations of electric vehicles and heat pumps are targeted to provide regulation-based ancillary services, as the inherent operational flexibility and autonomous device-level control strategy associated with these load-types provide an ideal platform to mitigate enhanced variability within the power system. An optimal control strategy capable of simultaneously balancing these grid-side objectives with those typically expected on the demand-side is introduced. End-use digital communication hardware is used to track and control population dynamics through the development of online aggregate load models equivalent to conventional dispatchable generation. The viability of the proposed load control strategy is assessed through model-based simulations that explicitly track end-use functionality of responsive devices within a power systems analysis typically implemented to observe the effects of integrated wind energy systems. Results indicate that there is great potential for the proposed method to displace the need for increased online regulation reserve capacity in systems considering a high penetration of wind energy, thereby allowing conventional generation to operate more efficiently. (orig.)

Wind climate modeling using Weibull and extreme value distribution ...

African Journals Online (AJOL)

It is very much important to fit wind speed data into some suitable statistical model for two aspects. One is fatigue failure due to periodic vortex shedding and the other is to estimate the wind energy potential of a particular location. For the fatigue failure due to periodic vortex shedding, it is important to analyse the load cycle.

Modelo de análisis de cargas máximas en aerogeneradores producidas por vientos extremos // Model of analysis of maximum loads in wind generators produced by extreme winds.

Directory of Open Access Journals (Sweden)

Omar Herrera - Sánchez

2010-05-01

renewable source of energy totally, either because the country isvery small, or because it coincides the area of more potential fully with that of high risk. To counteractthis situation, a model of analysis of maxims loads has been elaborated taken place the extremewinds in wind turbines of great behavior. This model has the advantage of determining, in a chosenplace, for the installation of a wind farm, the micro-areas with higher risk of wind loads above theacceptable for the standard classes of wind turbines.Key words: Wind turbines, wind loads, modeling of wind farm.

WindPACT Reference Wind Turbines

Energy Technology Data Exchange (ETDEWEB)

Dykes, Katherine L [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Rinker, Jennifer [Former National Renewable Energy Laboratory (NREL) employee

2018-04-02

To fully understand how loads and turbine cost scale with turbine size, it is necessary to have identical turbine models that have been scaled to different rated powers. The report presents the WindPACT baseline models, which are a series of four baseline models that were designed to facilitate investigations into the scalings of loads and turbine cost with size. The models have four different rated powers (750 kW, 1.5 MW, 3.0 MW, and 5.0 MW), and each model was designed to its specified rated power using the same design methodology. The models were originally implemented in FAST_AD, the predecessor to NREL's open-source wind turbine simulator FAST, but have yet to be implemented in FAST. This report contains the specifications for all four WindPACT baseline models - including structural, aerodynamic, and control specifications - along with the inherent assumptions and equations that were used to calculate the model parameters. It is hoped that these baseline models will serve as extremely useful resources for investigations into the scalings of costs, loads, or optimization routines.

Towards a reliable design of facade and roof elements against wind loading

NARCIS (Netherlands)

Geurts, C.P.W.; Staalduinen, P.C. van; Wit, M.S. de

2004-01-01

The most vulnerable parts of buildings with respect to wind loading are facades and roofs. Current standards on wind loading provide data to determine design loads for the elements in facades and roofs. These data are available for a limited number of simple building shapes. Up to now there is no

Wind/seismic comparison for upgrading existing structures

International Nuclear Information System (INIS)

Giller, R.A.

1989-01-01

This paper depicts the analysis procedures and methods used to evaluate three existing building structures for extreme wind loads. The three structures involved in this evaluation are located at the US Department of Energy's Hanford Site near Richland, Washington. This site is characterized by open flat grassland with few surrounding obstructions and has extreme winds in lieu of tornados as a design basis accident condition. This group of buildings represents a variety of construction types, including a concrete stack, a concrete load-bearing wall structure, and a rigid steel-frame building. The three structures included in this group have recently been evaluated for response to the design basis earthquake that included non-linear time history effects. The resulting loads and stresses from the wind analyses were compared to the loads and stresses resulting from seismic analyses. This approach eliminated the need to prepare additional capacity calculations that were already contained in the seismic evaluations

Performance enhancement and load reduction on wind turbines using inflow measurements

Energy Technology Data Exchange (ETDEWEB)

Abildgaard Kragh, K.

2013-06-15

Wind energy is being applied at a larger and larger scale worldwide, and is one of the technologies eligible for accommodating the increasing demand for renewable energy. However, wind energy is still not competitive compared to technologies that are based on fossil energy sources. Therefore, much wind energy research is focused on decreasing the cost of the energy that can be produced from the wind. The cost of energy can for example be decreased by ensuring that wind turbines are operated in a way that ensures that the maximum amount of energy is extracted, and that the turbines are not loaded excessively. The operation of a wind turbine is governed by a number of controllers that are based on a series of sensors and actuators. Classical wind turbine control utilizes sensors for measuring turbine parameters such as rotor speed, power and shaft torque, as well as actuators for applying generator torque and collective pitch angle changes. Thus, classical wind turbine control schemes are based on measurements of the effects of the inflow on the turbine. Therefore, the reactions of the control system to the inflow changes are inherently delayed compared to the actual inflow changes. Because of the inherent delay of the control system, the ability of the system to react promptly to inflow changes is limited. Control schemes that are based on inflow measurements have been developed to overcome the limitations of the classical wind turbine control system. By measuring the inflow directly, actuation can be initiated instantly as the inflow changes. If the inflow is measured upstream of the turbine, actuation can be initiated prior to the occurrence of a wind speed change at the turbine. Hereby, even the actuator delay can be compensated for. Upstream inflow measurements could for example be acquired using ''Light Detection and Ranging''. In this thesis, the potentials for improving the power production and decreasing the load variations of horizontal axis upwind turbines

Sensor comparison study for load alleviating wind turbine pitch control

DEFF Research Database (Denmark)

Kragh, Knud Abildgaard; Hansen, Morten Hartvig; Henriksen, Lars Christian

2014-01-01

As the size of wind turbines increases, the load alleviating capabilities of the turbine controller are becoming increasingly important. Load alleviating control schemes have traditionally been based on feedback from load sensor; however, recent developments of measurement technologies have enabled...... control on the basis of preview measurements of the inflow acquired using, e.g., light detection and ranging. The potential of alleviating load variations that are caused by mean wind speed changes through feed-forward control have been demonstrated through both experiments and simulations in several...... studies, whereas the potential of preview control for alleviating the load variations caused by azimuth dependent inflow variations is less described. Individual or cyclic pitch is required to alleviate azimuth dependent load variations and is traditionally applied through feedback control of the blade...

Floating wind generators offshore wind farm: Implications for structural loads and control actions

International Nuclear Information System (INIS)

Garcia, E.; Morant F, Quiles E.; Correcher, A.

2009-01-01

This paper describes the work currently carried out in the design of floating wind generators and their involvement in the future development of power generation in marine farms in depths exceeding 20 m. We discuss the main issues to be taken into account in the design of floating platforms, including the involvement of structural loads they bear. Also from a standpoint of control engineering are discussed strategies to reduce structural loads such a system to ensure adequate durability and therefore ensuring their economic viability. Finally, the abstract modeling tools for floating wind turbines that can be used in both structural design and the design of appropriate control algorithms

Dependence of offshore wind turbine fatigue loads on atmospheric stratification

DEFF Research Database (Denmark)

Hansen, Kurt Schaldemose; Larsen, Gunner Chr.; Ott, Søren

2014-01-01

The stratification of the atmospheric boundary layer (ABL) is classified in terms of the M-O length and subsequently used to determine the relationship between ABL stability and the fatigue loads of a wind turbine located inside an offshore wind farm. Recorded equivalent fatigue loads, representi...... conditions. In general, impact of ABL stratification is clearly seen on wake affected inflow cases for both blade and tower fatigue loads. However, the character of this dependence varies significantly with the type of inflow conditions – e.g. single wake inflow or multiple wake inflow....

Wake-Effect Minimising Optimal Control of Wind Farms, with Load Reduction

DEFF Research Database (Denmark)

Borchersen, Anders Bech; Larsen, Jesper Abildgaard; Sivabalan, Senthuran

2014-01-01

A power generating wind turbine causes a speed reduction and an added turbulence to the wind. Wind turbines in wind farms are often caught in these wakes and are found to have a higher structural load than non affected wind turbines. This article investigates the possibility of designing a contro...

Extreme winds over Europe in the ENSEMBLES regional climate models

Directory of Open Access Journals (Sweden)

S. D. Outten

2013-05-01

Full Text Available Extreme winds cause vast amounts of damage every year and represent a major concern for numerous industries including construction, afforestation, wind energy and many others. Under a changing climate, the intensity and frequency of extreme events are expected to change, and accurate projections of these changes will be invaluable to decision makers and society as a whole. This work examines four regional climate model downscalings over Europe following the SRES A1B scenario from the "ENSEMBLE-based Predictions of Climate Changes and their Impacts" project (ENSEMBLES. It investigates the projected changes in the 50 yr return wind speeds and the associated uncertainties. This is accomplished by employing the peaks-over-threshold method with the use of the generalised Pareto distribution. The models show that, for much of Europe, the 50 yr return wind is projected to change by less than 2 m s−1, while the uncertainties associated with the statistical estimates are larger than this. In keeping with previous works in this field, the largest source of uncertainty is found to be the inter-model spread, with some locations showing differences in the 50 yr return wind of over 20 m s−1 between two different downscalings.

Four wind speed multi-step forecasting models using extreme learning machines and signal decomposing algorithms

International Nuclear Information System (INIS)

Liu, Hui; Tian, Hong-qi; Li, Yan-fei

2015-01-01

Highlights: • A hybrid architecture is proposed for the wind speed forecasting. • Four algorithms are used for the wind speed multi-scale decomposition. • The extreme learning machines are employed for the wind speed forecasting. • All the proposed hybrid models can generate the accurate results. - Abstract: Realization of accurate wind speed forecasting is important to guarantee the safety of wind power utilization. In this paper, a new hybrid forecasting architecture is proposed to realize the wind speed accurate forecasting. In this architecture, four different hybrid models are presented by combining four signal decomposing algorithms (e.g., Wavelet Decomposition/Wavelet Packet Decomposition/Empirical Mode Decomposition/Fast Ensemble Empirical Mode Decomposition) and Extreme Learning Machines. The originality of the study is to investigate the promoted percentages of the Extreme Learning Machines by those mainstream signal decomposing algorithms in the multiple step wind speed forecasting. The results of two forecasting experiments indicate that: (1) the method of Extreme Learning Machines is suitable for the wind speed forecasting; (2) by utilizing the decomposing algorithms, all the proposed hybrid algorithms have better performance than the single Extreme Learning Machines; (3) in the comparisons of the decomposing algorithms in the proposed hybrid architecture, the Fast Ensemble Empirical Mode Decomposition has the best performance in the three-step forecasting results while the Wavelet Packet Decomposition has the best performance in the one and two step forecasting results. At the same time, the Wavelet Packet Decomposition and the Fast Ensemble Empirical Mode Decomposition are better than the Wavelet Decomposition and the Empirical Mode Decomposition in all the step predictions, respectively; and (4) the proposed algorithms are effective in the wind speed accurate predictions

Determination of Correlation for Extreme Metocean Variables

Directory of Open Access Journals (Sweden)

Nizamani Zafarullah

2017-01-01

Full Text Available Metocean environmental load includes wind, wave and currents. Offshore structures are designed for two environmental load design conditions i.e. extreme and operational load conditions of environmental loads are evaluated. The ccorrelation between load variables using Joint probability distribution, Pearson correlation coefficient and Spearman’s rank correlation coefficients methods in Peninsular Malaysia (PM, Sabah and Sarawak are computed. Joint probability distribution method is considered as a reliable method among three different methods to determine the relationship between load variables. The PM has good correlation between the wind-wave and wave-current; Sabah has both strong relationships of wind-wave and wind-current with 50 year return period; Sarawak has good correlation between wind and current in both 50 years and 100 years return period. Since Sabah has good correlation between the associated load variables, no matter in 50 years or 100 years of return period of load combination. Thus, method 1 of ISO 19901-1, specimen provides guideline for metocean loading conditions, can be adopted for design for offshore structure in Sabah. However, due to weak correlations in PM and Sarawak, this method cannot be applied and method 2, which is current practice in offshore industry, should continueto be used.

Mitigation of mechanical loads of NREL 5MW wind turbine tower

International Nuclear Information System (INIS)

Nam, Yoonsu; Im, Chang Hee

2012-01-01

As the size of a wind turbine increases, the mechanical structure has to have an increasing mechanical stiffness that is sufficient to withstand mechanical fatigue loads over a lifespan of more than 20 years. However, this leads to a heavier mechanical design, which means a high material cost during wind turbine manufacturing. Therefore, lightweight design of a wind turbine is an important design constraint. Usually, a lightweight mechanical structure has low damping. Therefore, if it is subjected to a disturbance, it will oscillate continuously. This study deals with the active damping control of a wind turbine tower. An algorithm that mitigates the mechanical loads of a wind turbine tower is introduced. The effectiveness of this algorithm is verified through a numerical simulation using GH Bladed, which is a commercial aero elastic code for wind turbines

Grid faults' impact on wind turbine structural loads

DEFF Research Database (Denmark)

Hansen, Anca Daniela; Cutululis, Nicolaos Antonio; Iov, F.

2007-01-01

The objective of this work is to illustrate the impact of the grid faults on the wind turbine structural loads. Grid faults are typically simulated in detailed power system simulation tools, which by applying simplified mechanical models, are not able to provide a throughout insight...... on the structural loads caused by sudden disturbances on the grid. On the other hand, structural loads of the wind turbine are typically assessed in advanced aerolastic computer codes, which by applying simplified electrical models do not provide detailed electrical insight. This paper presents a simulation...... strategy, where the focus is on how to access a proper combination of two complimentary simulations tools, such as the advanced aeroelastic computer code HAWC2 and the detailed power system simulation tool DIgSILENT, in order to provide a whole overview of both the structural and the electrical behaviour...

Structural Optimization of an Innovative 10 MW Wind Turbine Nacelle

DEFF Research Database (Denmark)

Dabrowski, Dariusz; Natarajan, Anand; Stehouwer, Ewoud

2015-01-01

For large wind turbine configurations of 10 MW and higher capacities, direct-drives present a more compact solution over conventional geared drivetrains. Further, if the generator is placed in front of the wind turbine rotor, a compact “king-pin” drive is designed, that allows the generator...... to be directly coupled to the hub. In presented study, the structural re-design of the innovative 10 MW nacelle was made using extreme loads obtained from a 10 MW reference wind turbine. On the basis of extreme loads the ultimate stresses on critical nacelle components were determined to ensure integrity...

Aerodynamic load control strategy of wind turbine in microgrid

Science.gov (United States)

Wang, Xiangming; Liu, Heshun; Chen, Yanfei

2017-12-01

A control strategy is proposed in the paper to optimize the aerodynamic load of the wind turbine in micro-grid. In grid-connection mode, the wind turbine adopts a new individual variable pitch control strategy. The pitch angle of the blade is rapidly given by the controller, and the pitch angle of each blade is fine tuned by the weight coefficient distributor. In islanding mode, according to the requirements of energy storage system, a given power tracking control method based on fuzzy PID control is proposed. Simulation result shows that this control strategy can effectively improve the axial aerodynamic load of the blade under rated wind speed in grid-connection mode, and ensure the smooth operation of the micro-grid in islanding mode.

Simple model of cable-stayed bridge deck subjected to static wind loading

Science.gov (United States)

Kang, Yi-Lung; Wang, Yang Cheng

1997-05-01

Cable-stayed bridges have been known since 18th century with aesthetics design. The structural system and the structural behavior are significantly different from those of continuous bridges. Compared to continuous bridge, cable- stayed bridges have more flexure bridge deck than those of continuous bridges.On the other hand, cable-stayed bridges have less stiffness to resist wind loading especially for lateral loads. The first considering of bridge engineering is safety. In 1940's, Tacoma Narrows Suspension Bridge destroyed by wind loading is a good example even though it is not a cable-stayed bridge. After the bridge was destroyed, a lot of research articles have been published regarding cable supported bridge subjected to wind loading. In recent days, high strength materials have been served. The bridge engineers use the advantages to expand the span length of cable-stayed bridges. Due to the span length increased and the use of high strength materials, cable- stayed bridges have more significant nonlinear behavior subjected to wind loading. In this paper, a slice bridge deck of cable-stayed bridge connected to internal support cables is considered. The deck has been considered to be subjected to lateral static wind loading. Since cables can not take compressive force, the deck has strongly nonlinear behavior even though the materials are linear elastic. Several primary load combinations have ben considered in this paper such as the bridge deck supposed to be moved horizontally without rotation or the bridge deck supposed to be moved horizontally with rotational deformation. The mathematical formulas and the numerical solutions are found and represented in graphical forms. The results can be provided to bridge designers and researchers for further study of this type of structure subjected to wind loading.

Calculating the sensitivity of wind turbine loads to wind inputs using response surfaces

International Nuclear Information System (INIS)

Rinker, Jennifer M.

2016-01-01

This paper presents a methodology to calculate wind turbine load sensitivities to turbulence parameters through the use of response surfaces. A response surface is a highdimensional polynomial surface that can be calibrated to any set of input/output data and then used to generate synthetic data at a low computational cost. Sobol sensitivity indices (SIs) can then be calculated with relative ease using the calibrated response surface. The proposed methodology is demonstrated by calculating the total sensitivity of the maximum blade root bending moment of the WindPACT 5 MW reference model to four turbulence input parameters: a reference mean wind speed, a reference turbulence intensity, the Kaimal length scale, and a novel parameter reflecting the nonstationarity present in the inflow turbulence. The input/output data used to calibrate the response surface were generated for a previous project. The fit of the calibrated response surface is evaluated in terms of error between the model and the training data and in terms of the convergence. The Sobol SIs are calculated using the calibrated response surface, and the convergence is examined. The Sobol SIs reveal that, of the four turbulence parameters examined in this paper, the variance caused by the Kaimal length scale and nonstationarity parameter are negligible. Thus, the findings in this paper represent the first systematic evidence that stochastic wind turbine load response statistics can be modeled purely by mean wind wind speed and turbulence intensity. (paper)

Wind Loads on Ships and Offshore Structures Estimated by CFD

DEFF Research Database (Denmark)

Aage, Christian; Hvid, S.L.; Hughes, P.H.

1997-01-01

Wind loads on ships and offshore structures could until recently be determined only by model tests, or by statistical methods based on model tests. By the development of Computational Fluid Dynamics or CFD there is now a realistic computational alternative available. In this paper, wind loads...... on a seagoing ferry and on a semisubmersible offshore platform have been estimated by CFD. The results have been compared with wind tunnel model tests and, for the ferry, a few full-scale measurements, and good agreement is obtained. The CFD method offers the possibility of a computational estimate of scale...... effects related to wind tunnel model testing. An example of such an estimate on the ferry is discussed. Due to the time involved in generating the computational mesh and in computing the solution, the CFD method is not at the moment economically competitive to routine wind tunnel model testing....

A systematic hub loads model of a horizontal wind turbine

International Nuclear Information System (INIS)

Kazacoks, Romans; Jamieson, Peter

2014-01-01

The wind turbine industry has focused offshore on increasing the capacity of a single unit through up-scaling their machines. There is however a lack of systematic studies on how loads vary due to properties of a wind turbine and scaling of wind turbines. The purpose of this paper is to study how applied blade modifications, with similarities such as mass, stiffness and dimensions, influence blade root moments and lifetime damage equivalent loads (DELs) of the rotor blades. In order to produce fatigue load blade root moment trends based on the applied modifications. It was found that a linear trend of lifetime DELs based on the applied modifications of blades, which have effect on the natural frequency of blade of the original or reference model. As the control system was tuned for the specific frequency of the reference model. The linear trend of lifetime DELs was generated as long as the natural frequency of the reference model was preserved. For larger modifications of the wind turbine the controller would need retuning

Correlated wind-power production and electric load scenarios for investment decisions

International Nuclear Information System (INIS)

Baringo, L.; Conejo, A.J.

2013-01-01

Highlights: ► Investment models require an accurate representation of the involved uncertainty. ► Demand and wind power production are correlated and uncertain parameters. ► Two methodologies are provided to represent uncertainty and correlation. ► An accurate uncertainty representation is crucial to get optimal results. -- Abstract: Stochastic programming constitutes a useful tool to address investment problems. This technique represents uncertain input data using a set of scenarios, which should accurately describe the involved uncertainty. In this paper, we propose two alternative methodologies to efficiently generate electric load and wind-power production scenarios, which are used as input data for investment problems. The two proposed methodologies are based on the load- and wind-duration curves and on the K-means clustering technique, and allow representing the uncertainty of and the correlation between electric load and wind-power production. A case study pertaining to wind-power investment is used to show the interest of the proposed methodologies and to illustrate how the selection of scenarios has a significant impact on investment decisions.

A Wind Farm Active Power Dispatch Strategy for Fatigue Load Reduction

DEFF Research Database (Denmark)

Zhang, Baohua; N. Soltani, Mohsen; Hu, Weihao

2016-01-01

One of the biggest challenges in wind farm management is to cope with requirements from the grid companies and to optimize efficiency and minimize wear on wind turbines. This paper addresses an optimized active power dispatch strategy of a wind farm to reduce the fatigue load of wind turbines, wh...

Parameterized Disturbance Observer Based Controller to Reduce Cyclic Loads of Wind Turbine

Directory of Open Access Journals (Sweden)

Raja M. Imran

2018-05-01

Full Text Available This paper is concerned with bump-less transfer of parameterized disturbance observer based controller with individual pitch control strategy to reduce cyclic loads of wind turbine in full load operation. Cyclic loads are generated due to wind shear and tower shadow effects. Multivariable disturbance observer based linear controllers are designed with objective to reduce output power fluctuation, tower oscillation and drive-train torsion using optimal control theory. Linear parameterized controllers are designed by using a smooth scheduling mechanism between the controllers. The proposed parameterized controller with individual pitch was tested on nonlinear Fatigue, Aerodynamics, Structures, and Turbulence (FAST code model of National Renewable Energy Laboratory (NREL’s 5 MW wind turbine. The closed-loop system performance was assessed by comparing the simulation results of proposed controller with a fixed gain and parameterized controller with collective pitch for full load operation of wind turbine. Simulations are performed with step wind to see the behavior of the system with wind shear and tower shadow effects. Then, turbulent wind is applied to see the smooth transition of the controllers. It can be concluded from the results that the proposed parameterized control shows smooth transition from one controller to another controller. Moreover, 3p and 6p harmonics are well mitigated as compared to fixed gain DOBC and parameterized DOBC with collective pitch.

Toward Isolation of Salient Features in Stable Boundary Layer Wind Fields that Influence Loads on Wind Turbines

Directory of Open Access Journals (Sweden)

Jinkyoo Park

2015-04-01

Full Text Available Neutral boundary layer (NBL flow fields, commonly used in turbine load studies and design, are generated using spectral procedures in stochastic simulation. For large utility-scale turbines, stable boundary layer (SBL flow fields are of great interest because they are often accompanied by enhanced wind shear, wind veer, and even low-level jets (LLJs. The generation of SBL flow fields, in contrast to simpler stochastic simulation for NBL, requires computational fluid dynamics (CFD procedures to capture the physics and noted characteristics—such as shear and veer—that are distinct from those seen in NBL flows. At present, large-eddy simulation (LES is the most efficient CFD procedure for SBL flow field generation and related wind turbine loads studies. Design standards, such as from the International Electrotechnical Commission (IEC, provide guidance albeit with simplifying assumptions (one such deals with assuming constant variance of turbulence over the rotor and recommend standard target turbulence power spectra and coherence functions to allow NBL flow field simulation. In contrast, a systematic SBL flow field simulation procedure has not been offered for design or for site assessment. It is instructive to compare LES-generated SBL flow fields with stochastic NBL flow fields and associated loads which we evaluate for a 5-MW turbine; in doing so, we seek to isolate distinguishing characteristics of wind shear, wind veer, and turbulence variation over the rotor plane in the alternative flow fields and in the turbine loads. Because of known differences in NBL-stochastic and SBL-LES wind fields but an industry preference for simpler stochastic simulation in design practice, this study investigates if one can reproduce stable atmospheric conditions using stochastic approaches with appropriate corrections for shear, veer, turbulence, etc. We find that such simple tuning cannot consistently match turbine target SBL load statistics, even though

Reliability Analysis of Wind Turbines

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard

2008-01-01

In order to minimise the total expected life-cycle costs of a wind turbine it is important to estimate the reliability level for all components in the wind turbine. This paper deals with reliability analysis for the tower and blades of onshore wind turbines placed in a wind farm. The limit states...... consideres are in the ultimate limit state (ULS) extreme conditions in the standstill position and extreme conditions during operating. For wind turbines, where the magnitude of the loads is influenced by the control system, the ultimate limit state can occur in both cases. In the fatigue limit state (FLS......) the reliability level for a wind turbine placed in a wind farm is considered, and wake effects from neighbouring wind turbines is taken into account. An illustrative example with calculation of the reliability for mudline bending of the tower is considered. In the example the design is determined according...

Active load control techniques for wind turbines.

Energy Technology Data Exchange (ETDEWEB)

van Dam, C.P. (University of California, Davis, CA); Berg, Dale E.; Johnson, Scott J. (University of California, Davis, CA)

2008-07-01

This report provides an overview on the current state of wind turbine control and introduces a number of active techniques that could be potentially used for control of wind turbine blades. The focus is on research regarding active flow control (AFC) as it applies to wind turbine performance and loads. The techniques and concepts described here are often described as 'smart structures' or 'smart rotor control'. This field is rapidly growing and there are numerous concepts currently being investigated around the world; some concepts already are focused on the wind energy industry and others are intended for use in other fields, but have the potential for wind turbine control. An AFC system can be broken into three categories: controls and sensors, actuators and devices, and the flow phenomena. This report focuses on the research involved with the actuators and devices and the generated flow phenomena caused by each device.

Response Analysis and Comparison of a Spar-Type Floating Offshore Wind Turbine and an Onshore Wind Turbine under Blade Pitch Controller Faults

DEFF Research Database (Denmark)

Etemaddar, M.; Blanke, Mogens; Gao, Z.

2016-01-01

in the controller dynamic link library and a short-term extreme response analysis is performed using the HAWC2 simulation tool.The main objectives of this paper are to investigate how different faults affect the performance of wind turbines for condition monitoring purposes and which differences exist...... in the structural responses between onshore and offshore floating wind turbines. Statistical analysis of the selected response parameters are conducted using the six1-hour stochastic samples for each load case.For condition monitoring purpose,the effects of faults on the responses at different wind speeds and fault...... amplitudes are investigated by comparing the same response under normal operation.The severities of the individual faults are categorized by the extreme values of structural loads and the structural components are sorted based on the magnitude of the fault effects on the extreme values.The pitch sensor fixed...

Cost optimization of wind turbines for large-scale offshore wind farms

International Nuclear Information System (INIS)

Fuglsang, P.; Thomsen, K.

1998-02-01

This report contains a preliminary investigation of site specific design of off-shore wind turbines for a large off-shore wind farm project at Roedsand that is currently being proposed by ELKRAFT/SEAS. The results were found using a design tool for wind turbines that involve numerical optimization and aeroelastic calculations of response. The wind climate was modeled in detail and a cost function was used to estimate costs from manufacture and installation. Cost of energy is higher for off-shore installations. A comparison of an off-shore wind farm site with a typical stand alone on-shore site showed an increase of the annual production of 28% due to the difference in wind climate. Extreme loads and blade fatigue loads were nearly identical, however,fatigue loads on other main components increased significantly. Optimizations were carried out to find the optimum overall off-shore wind turbine design. A wind turbine for the off-shore wind farm should be different compared with a stand-alone on-shore wind turbine. The overall design changed were increased swept area and rated power combined with reduced rotor speed and tower height. Cost was reduced by 12% for the final 5D/14D off-shore wind turbine from 0.306 DKr/kWh to 0.270 DKr/kWh. These figures include capital costs from manufacture and installation but not on-going costs from maintenance. These results make off-shore wind farms more competitive and comparable to the reference on-shore stand-alone wind turbine. A corresponding reduction of cost of energy could not be found for the stand alone on-shore wind turbine. Furthermore the fatigue loads on wind turbines in on-shore wind farms will increase and cost of energy will increase in favor of off-shore wind farms. (au) EFP-95; EU-JOULE-3; 21 tabs., 7 ills., 8 refs

Validation of Simplified Load Equations Through Loads Measurement and Modeling of a Small Horizontal-Axis Wind Turbine Tower

Energy Technology Data Exchange (ETDEWEB)

Dana, Scott [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Van Dam, Jeroen J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Damiani, Rick R [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2018-04-24

As part of an ongoing effort to improve the modeling and prediction of small wind turbine dynamics, the National Renewable Energy Laboratory (NREL) tested a small horizontal-axis wind turbine in the field at the National Wind Technology Center. The test turbine was a 2.1-kW downwind machine mounted on an 18-m multi-section fiberglass composite tower. The tower was instrumented and monitored for approximately 6 months. The collected data were analyzed to assess the turbine and tower loads and further validate the simplified loads equations from the International Electrotechnical Commission (IEC) 61400-2 design standards. Field-measured loads were also compared to the output of an aeroelastic model of the turbine. In particular, we compared fatigue loads as measured in the field, predicted by the aeroelastic model, and calculated using the simplified design equations. Ultimate loads at the tower base were assessed using both the simplified design equations and the aeroelastic model output. The simplified design equations in IEC 61400-2 do not accurately model fatigue loads and a discussion about the simplified design equations is discussed.

Gearbox Fatigue Load Estimation for Condition Monitoring of Wind Turbines

DEFF Research Database (Denmark)

Perisic, Nevena; Pedersen, Bo Juul; Kirkegaard, Poul Henning

2012-01-01

control and data acquisition (SCADA) system. Estimated loads can be further used for prediction of remaining operating lifetime of turbine components, detection of high stress level or fault detection. An augmented Kalman filter is chosen as the fatigue load estimator because its characteristics well suit......The focus of the paper is on a design of a fatigue load estimator for predictive condition monitoring systems (CMS) of wind turbines. In order to avoid high-price measurement equipment required for direct load measuring, an indirect approach is suggested using only measurements from supervisory...... for the real time application. This paper presents results of the estimation of the gearbox fatigue load, often called shaft torque, using simulated data of wind turbine. Noise sensitivity of the algorithm is investigated by assuming different levels of measurement noise. Shaft torque estimations are compared...

Probabilistic forecasting of wind power generation using extreme learning machine

DEFF Research Database (Denmark)

Wan, Can; Xu, Zhao; Pinson, Pierre

2014-01-01

an extreme learning machine (ELM)-based probabilistic forecasting method for wind power generation. To account for the uncertainties in the forecasting results, several bootstrapmethods have been compared for modeling the regression uncertainty, based on which the pairs bootstrap method is identified......Accurate and reliable forecast of wind power is essential to power system operation and control. However, due to the nonstationarity of wind power series, traditional point forecasting can hardly be accurate, leading to increased uncertainties and risks for system operation. This paper proposes...... with the best performance. Consequently, a new method for prediction intervals formulation based on theELMand the pairs bootstrap is developed.Wind power forecasting has been conducted in different seasons using the proposed approach with the historical wind power time series as the inputs alone. The results...

European wind turbine standards 2 (EWTS-2)

Energy Technology Data Exchange (ETDEWEB)

Pierik, J T.G.; Dekker, J W.M.; Braam, H [and others

1999-03-01

A summary is given of the main results of the European Wind Turbine Standards II project. EWTS-II was completed in 1998 and included investigations on: 1) wind farms-wind field and turbine loading; 2) complex terrain and fatigue loading; 3) extreme wind conditions; 4) quantification of failure probabilities; 5) integration of blade tests in design; 6) power performance in complex terrain; 7) site evaluation. In addition to these scientific evaluations, the EWTS-II participants established an organization of qualified measuring institute in the field of wind energy, the MEASNET organization. MEASNET unified measurement procedures of the participating institutes and guarantees qualified measurements and mutual acceptance among its members. (LN)

Full-load converter connected asynchronous generators for MW class wind turbines

Energy Technology Data Exchange (ETDEWEB)

Akhmatov, Vladislav

2005-06-15

Wind turbines equipped with full-load converter-connected asynchronous generators are a known concept. These have rating up to hundreds of kW and are a feasible concept for MW class wind turbines and may have advantages when compared to conventional wind turbines with directly connected generators. The concept requires the use of full-scale frequency converters, but the mechanical gearbox is smaller than in conventional wind turbines of the same rating. Application of smaller gearbox may reduce the no-load losses in the wind turbines, which is why such wind turbines with converter connected generators may start operation at a smaller wind speed. Wind turbines equipped with such converted connected asynchronous generators are pitch-controlled and variable-speed. This allows better performance and control. The converter control may be applied to support the grid voltage at short-circuit faults and to improve the fault-ride-through capability of the wind turbines, which makes the concepts relevant for large wind farms. The Danish transmission system operator Energinet-DK has implemented the general model of wind turbines equipped with converter connected asynchronous generators with the simulation tool Powerfactory (DlgSilent). The article presents Energinet-DK's experience of modeling this feasible wind turbine concept. (Author)

Extreme and First-Passage Time of Ship Collision Loads

DEFF Research Database (Denmark)

Nielsen, Søren R. K.; Thoft-Christensen, Palle

1983-01-01

The paper outlines a general theory from which the distribution function of the extreme peak collision load encountered during a certain intended lifetime can be cal culated assuming the arrival of ship collisions to be specified by a Poisson counting proces s.......The paper outlines a general theory from which the distribution function of the extreme peak collision load encountered during a certain intended lifetime can be cal culated assuming the arrival of ship collisions to be specified by a Poisson counting proces s....

Review of climatic input data for wind load design in accordance with SANS 10160-3

CSIR Research Space (South Africa)

Goliger, Adam MW

2017-12-01

Full Text Available factor QWE that provides for the wind engineering procedures, such as the wind speed profile and pressure coefficients. The characteristic wind load is then given by Equation 4, where CoV is the coefficient of variation (σV/µV): QW,k = QWE (µV + 2....59 σV)2 = QWE µVk2(1+ 2.59 CoVV)2 (6) Design wind load The design wind load can be obtained by determining the wind speed according to Equation 4 for an exceedance probability (PF) that corresponds with the appropriate target reliability (β...

A wind-tunnel investigation of wind-turbine wakes in different yawed and loading conditions

Science.gov (United States)

Bastankhah, Majid; Porté-Agel, Fernando

2015-04-01

Wind-turbine wakes have negative effects on wind-farm performance. They are associated with: (a) the velocity deficit, which reduces the generated power of downwind turbines; and (b) the turbulence level, which increases the fatigue loads on downwind turbines. Controlling the yaw angle of turbines can potentially improve the performance of wind farms by deflecting the wake away from downwind turbines. However, except for few studies, wakes of yawed turbines still suffer from the lack of systematic research. To fill this research gap, we performed wind-tunnel experiments in the recirculating boundary-layer wind tunnel at the WIRE Laboratory of EPFL to better understand the wakes of yawed turbines. High-resolution stereoscopic particle image-velocimetry (S-PIV) was used to measure three velocity components in a horizontal plane located downwind of a horizontal-axis, three-blade model turbine. A servo-controller was connected to the DC generator of the turbine, which allowed us to apply different loadings. The power and thrust coefficients of the turbine were also measured for each case. These power and thrust measurements together with the highly-resolved flow measurements enabled us to study different wake characteristics such as the energy entrainment from the outer flow into the wake, the wake deflection and the helicoidal tip vortices for yawed turbines.

Calibration procedures for improved accuracy of wind turbine blade load measurement

Energy Technology Data Exchange (ETDEWEB)

Dahlberg, J.Aa. [Aeronautical Research Inst. of Sweden, Bromma (Sweden); Johansson, Hjalmar [Teknikgruppen AB, Sollentuna (Sweden)

1996-12-01

External loads acting on wind turbine blades are mainly transferred via the hub to the rest of the structure. It is therefore a normal approach to measure the loads acting on the turbine by load measurements in the blade roots. The load measurement is often accomplished by measurements of strain on the surface of the blade or the hub. The strain signals are converted to loads by applying calibration factors to the measurements. This paper deals with difficulties associated with load measurements on two different wind turbines; one with strain gauges applied to a steel hub where a linear stress-load relationship is expected and the other with strain gauges applied to the GFRP blade close to the bearings where strong non-linearity`s and temperature effects are expected. This paper suggests calibration methods to overcome these problems. 2 refs, 11 figs

Wake Influence on Dynamic Load Characteristics of Offshore Floating Wind Turbines

DEFF Research Database (Denmark)

Jeon, Minu; Lee, Soogab; Kim, Taeseong

2016-01-01

Because the flow conditions of an offshore floating wind turbine and onshore fixed wind turbine differ, it is debatable whether the aerodynamic load predictions of an offshore floating wind turbine using the conventional blade-element momentum theory, which does not consider the dynamic wake effe...

Validation of SWAY Wind Turbine Response in FAST, with a Focus on the Influence of Tower Wind Loads: Preprint

Energy Technology Data Exchange (ETDEWEB)

Koh, J. H.; Robertson, A.; Jonkman, J.; Driscoll, R.; Yin Kwee Ng, E.

2015-04-23

Need to modify simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions. the SWAY system in both turbine operating and nonoperating conditions. Mixed results were observed when comparing the simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions. without the new tower-load capability to examine its influence on the response characteristics of the system. This is important in situations when the turbine is parked in survival conditions. The simulation results were then compared to measured data from the SWAY system in both turbine operating and nonoperating conditions. Mixed results were observed when comparing the simulated system behavior to the measured data, but the tower wind loads improved the comparison for nonoperating conditions.

Full scale experimental analysis of wind direction changes (EOD)

DEFF Research Database (Denmark)

Hansen, Kurt Schaldemose

2007-01-01

wind direction gust amplitudes associated with the investigated European sites are low compared to the recommended IEC- values. However, these values, as function of the mean wind speed, are difficult to validate thoroughly due to the limited number of fully correlated measurements....... the magnitudes of a joint gust event defined by a simultaneously wind speed- and direction change in order to obtain an indication of the validity of the magnitudes specified in the IEC code. The analysis relates to pre-specified recurrence periods and is based on full-scale wind field measurements. The wind......A coherent wind speed and wind direction change (ECD) load case is defined in the wind turbine standard. This load case is an essential extreme load case that e.g. may be design driving for flap defection of active stall controlled wind turbines. The present analysis identifies statistically...

Extreme winds in the Western North Pacific

Energy Technology Data Exchange (ETDEWEB)

Ott, S.

2006-11-15

A statistical model for extreme winds in the western North Pacific is developed, the region on the Planet where tropical cyclones are most common. The model is based on best track data derived mostly from satellite images of tropical cyclones. The methods used to estimate surface wind speeds from satellite images is discussed with emphasis on the empirical basis, which, unfortunately, is not very strong. This is stressed by the fact that Japanese and US agencies arrive at markedly different estimates. On the other hand, best track data records cover a long period of time and if not perfect they are at least coherent over time in their imperfections. Applying the the Holland model to the best track data, wind profiles can be assigned along the tracks. From this annual wind speed maxima at any particular point in the region can be derived. The annual maxima, in turn, are fitted to a Gumbel distribution using a generalization Abild's method that allows for data wind collected from multiple positions. The choice of this method is justified by a Monte Carlo simulation comparing it to two other methods. The principle output is a map showing fifty year winds in the region. The method is tested against observed winds from Philippine synoptic stations and fair agreement is found for observed and predicted 48 year maxima. However, the almost biasfree performance of the model could be fortuitous, since precise definitions of 'windspeed' in terms averaging time, height above ground and assumed surface roughness are not available, neither for best tracks nor for the synoptic data. The work has been carried out under Danish Research Agency grant 2104-04-0005 'Offshore wind power' and it also covers the findings and analysis carried out in connection with task 1.6 of the project 'Feasibility Assessment and Capacity Building for Wind Energy Development in Cambodia, The Philippines and Vietnam' during 2005-06 under contract 125-2004 with EU

Wind Tunnel Tests for Wind Pressure Distribution on Gable Roof Buildings

Science.gov (United States)

2013-01-01

Gable roof buildings are widely used in industrial buildings. Based on wind tunnel tests with rigid models, wind pressure distributions on gable roof buildings with different aspect ratios were measured simultaneously. Some characteristics of the measured wind pressure field on the surfaces of the models were analyzed, including mean wind pressure, fluctuating wind pressure, peak negative wind pressure, and characteristics of proper orthogonal decomposition results of the measured wind pressure field. The results show that extremely high local suctions often occur in the leading edges of longitudinal wall and windward roof, roof corner, and roof ridge which are the severe damaged locations under strong wind. The aspect ratio of building has a certain effect on the mean wind pressure coefficients, and the effect relates to wind attack angle. Compared with experimental results, the region division of roof corner and roof ridge from AIJ2004 is more reasonable than those from CECS102:2002 and MBMA2006.The contributions of the first several eigenvectors to the overall wind pressure distributions become much bigger. The investigation can offer some basic understanding for estimating wind load distribution on gable roof buildings and facilitate wind-resistant design of cladding components and their connections considering wind load path. PMID:24082851

Active aerodynamic load control on wind turbines : Aeroservoelastic modeling and wind tunnel

NARCIS (Netherlands)

Barlas, A.

2011-01-01

This thesis investigates particular concepts and technologies that can alleviate fatigue loads on wind turbines by using distributed active aerodynamic devices on the blades, a concept briefly referred to as `smart blades'. Firstly, published research work on smart control devices is reviewed, and

Fluidic load control for wind turbines blades

NARCIS (Netherlands)

Boeije, C.S.; Vries, de H.; Cleine, I.; Emden, van E.; Zwart, G.G.M.; Stobbe, H.; Hirschberg, A.; Hoeijmakers, H.W.M.; Maureen Hand, xx

2009-01-01

This paper describes the initial steps into the investigation of the possibility of reducing fatigue loads on wind turbine blades by the application of fluidic jets. This investigation involves static pressure measurements as well as numerical simulations for a non-rotating NACA-0018 airfoil. The

Estimating return periods of extreme values from relatively short time series of winds

Science.gov (United States)

Jonasson, Kristjan; Agustsson, Halfdan; Rognvaldsson, Olafur; Arfeuille, Gilles

2013-04-01

An important factor for determining the prospect of individual wind farm sites is the frequency of extreme winds at hub height. Here, extreme winds are defined as the value of the highest 10 minutes averaged wind speed with a 50 year return period, i.e. annual exceeding probability of 2% (Rodrigo, 2010). A frequently applied method to estimate winds in the lowest few hundred meters above ground is to extrapolate observed 10-meter winds logarithmically to higher altitudes. Recent study by Drechsel et al. (2012) showed however that this methodology is not as accurate as interpolating simulated results from the global ECMWF numerical weather prediction (NWP) model to the desired height. Observations of persistent low level jets near Colima in SW-Mexico also show that the logarithmic approach can give highly inaccurate results for some regions (Arfeuille et al., 2012). To address these shortcomings of limited, and/or poorly representative, observations and extrapolations of winds one can use NWP models to dynamically scale down relatively coarse resolution atmospheric analysis. In the case of limited computing resources one has typically to make a compromise between spatial resolution and the duration of the simulated period, both of which can limit the quality of the wind farm siting. A common method to estimate maximum winds is to fit an extreme value distribution (e.g. Gumbel, gev or Pareto) to the maximum values of each year of available data, or the tail of these values. If data are only available for a short period, e.g. 10 or 15 years, then this will give a rather inaccurate estimate. It is possible to deal with this problem by utilizing monthly or weekly maxima, but this introduces new problems: seasonal variation, autocorrelation of neighboring values, and increased discrepancy between data and fitted distribution. We introduce a new method to estimate return periods of extreme values of winds at hub height from relatively short time series of winds, simulated

Multi-objective Extremum Seeking Control for Enhancement of Wind Turbine Power Capture with Load Reduction

Science.gov (United States)

Xiao, Yan; Li, Yaoyu; Rotea, Mario A.

2016-09-01

The primary objective in below rated wind speed (Region 2) is to maximize the turbine's energy capture. Due to uncertainty, variability of turbine characteristics and lack of inexpensive but precise wind measurements, model-free control strategies that do not use wind measurements such as Extremum Seeking Control (ESC) have received significant attention. Based on a dither-demodulation scheme, ESC can maximize the wind power capture in real time despite uncertainty, variabilities and lack of accurate wind measurements. The existing work on ESC based wind turbine control focuses on power capture only. In this paper, a multi-objective extremum seeking control strategy is proposed to achieve nearly optimum wind energy capture while decreasing structural fatigue loads. The performance index of the ESC combines the rotor power and penalty terms of the standard deviations of selected fatigue load variables. Simulation studies of the proposed multi-objective ESC demonstrate that the damage-equivalent loads of tower and/or blade loads can be reduced with slight compromise in energy capture.

Modelling of extreme gusts for design calculations (NewGust)

Energy Technology Data Exchange (ETDEWEB)

Bierbooms, W; Cheng, Po-Wen [Delft Univ. of Technology, Inst. for Wind Energy, Delft (Netherlands); Larsen, G [Risoe National Lab., Roskilde (Denmark); Juul Pedersen, B [Vestas Wind Systems A/S, Lem (Denmark); Hansen, K [Tecnical Univ. of Denmark (Denmark)

1999-03-01

The main objective of the NewGust project is to come to a realistic and verified description of extreme gusts based on the stochastic properties of wind. In this paper the first results of the project are presented. Theoretical considerations indicate that the shape of extreme gusts is very sharp. Based on simulated wind time series, mean gust shapes (for several amplitudes and mean wind speeds) are determined and compared with the theoretical curves. The resemblance turned out to be very good. Furthermore, the influence of the sampling rate and the dynamics of a cup anemometer on the empirical mean gust shape are examined. The promising results are confirmed by a (preliminary) verification based on measured wind time series, available from the database on wind characteristics. The mean shape of gusts, of certain amplitude, together with their probability of occurrence can be used to obtain the distribution of the extreme response of wind turbines to gust loading. (au)

Committee VI.1. Extreme Hull Girder Loading

DEFF Research Database (Denmark)

Jensen, Jørgen Juncher

2000-01-01

Committee Mandate. Evaluate and develop direct calculation procedures for extreme wawe loads on ship hull girders. Due consideration shall be given to stochastic and non-linear effects. The procedures shall be assessed by comparison with in-service experiences, model tests and more refined...

Reliability of offshore wind power production under extreme wind conditions. Deliverable D 9.5. Work Package 9: Electrical grid

DEFF Research Database (Denmark)

Cutululis, Nicolaos Antonio; Zeni, Lorenzo

years, with each year simulated with five random seeds, leading to a total of 25 annual wind power time series for six large offshore wind farms, summing up to a little over 330 wind turbines. Two storm control strategies were used. The analysis involved several aspects inspired from reliability studies....... The aspects investigated are storm events occurrences and durations, storm control strategy impact on the capacity factor (lost production), the loss of production (power produced from wind drops below a certain threshold due to high wind speeds and storm controller) and finally, the wind power production......Reliability of offshore wind production under extreme wind conditions was investigated in this report. The wind power variability from existing and future large offshore wind farms in Western Denmark were simulated using the Correlated Wind model developed at Risø. The analysis was done for five...

Dynamic Loads and Wake Prediction for Large Wind Turbines Based on Free Wake Method

Institute of Scientific and Technical Information of China (English)

Cao Jiufa; Wang Tongguang; Long Hui; Ke Shitang; Xu Bofeng

2015-01-01

With large scale wind turbines ,the issue of aerodynamic elastic response is even more significant on dy-namic behaviour of the system .Unsteady free vortex wake method is proposed to calculate the shape of wake and aerodynamic load .Considering the effect of aerodynamic load ,inertial load and gravity load ,the decoupling dy-namic equations are established by using finite element method in conjunction of the modal method and equations are solved numerically by Newmark approach .Finally ,the numerical simulation of a large scale wind turbine is performed through coupling the free vortex wake modelling with structural modelling .The results show that this coupling model can predict the flexible wind turbine dynamic characteristics effectively and efficiently .Under the influence of the gravitational force ,the dynamic response of flapwise direction contributes to the dynamic behavior of edgewise direction under the operational condition of steady wind speed .The difference in dynamic response be-tween the flexible and rigid wind turbines manifests when the aerodynamics/structure coupling effect is of signifi-cance in both wind turbine design and performance calculation .

Bayesian analysis applied to statistical uncertainties of extreme response distributions of offshore wind turbines

NARCIS (Netherlands)

Cheng, P.W.; Kuik, van G.A.M.; Bussel, van G.J.W.; Vrouwenvelder, A.C.W.M.

2002-01-01

Extreme response is an important design variable for wind turbines. The statistical uncertainties concerning the extreme response distribution are simulated here with data concerning physical characteristics obtained from measurements. The extreme responses are the flap moment at the blade root and

Spatio-temporal modelling of wind speed variations and extremes in the Caribbean and the Gulf of Mexico

Science.gov (United States)

Rychlik, Igor; Mao, Wengang

2018-02-01

The wind speed variability in the North Atlantic has been successfully modelled using a spatio-temporal transformed Gaussian field. However, this type of model does not correctly describe the extreme wind speeds attributed to tropical storms and hurricanes. In this study, the transformed Gaussian model is further developed to include the occurrence of severe storms. In this new model, random components are added to the transformed Gaussian field to model rare events with extreme wind speeds. The resulting random field is locally stationary and homogeneous. The localized dependence structure is described by time- and space-dependent parameters. The parameters have a natural physical interpretation. To exemplify its application, the model is fitted to the ECMWF ERA-Interim reanalysis data set. The model is applied to compute long-term wind speed distributions and return values, e.g., 100- or 1000-year extreme wind speeds, and to simulate random wind speed time series at a fixed location or spatio-temporal wind fields around that location.

Determination of the wind power systems load to achieve operation in the maximum energy area

Science.gov (United States)

Chioncel, C. P.; Tirian, G. O.; Spunei, E.; Gillich, N.

2018-01-01

This paper analyses the operation of the wind turbine, WT, in the maximum power point, MPP, by linking the load of the Permanent Magnet Synchronous Generator, PMSG, with the wind speed value. The load control methods at wind power systems aiming an optimum performance in terms of energy are based on the fact that the energy captured by the wind turbine significantly depends on the mechanical angular speed of the wind turbine. The presented control method consists in determining the optimal mechanical angular speed, ωOPTIM, using an auxiliary low power wind turbine, WTAUX, operating without load, at maximum angular velocity, ωMAX. The method relies on the fact that the ratio ωOPTIM/ωMAX has a constant value for a given wind turbine and does not depend on the time variation of the wind speed values.

Characterization of the wind loads and flow fields around a gable-roof building model in tornado-like winds

Energy Technology Data Exchange (ETDEWEB)

Hu, Hui; Yang, Zifeng; Sarkar, Partha [Iowa State University, Department of Aerospace Engineering, Ames, IA (United States); Haan, Fred [Iowa State University, Department of Aerospace Engineering, Ames, IA (United States); Rose-Hulman Institute of Technology, Department of Mechanical Engineering, Terre Haute, IN (United States)

2011-09-15

An experimental study was conducted to quantify the characteristics of a tornado-like vortex and to reveal the dynamics of the flow-structure interactions between a low-rise, gable-roof building model and swirling, turbulent tornado-like winds. The experimental work was conducted by using a large-scale tornado simulator located in the Aerospace Engineering Department of Iowa State University. In addition to measuring the pressure distributions and resultant wind loads acting on the building model, a digital Particle Image Velocimetry system was used to conduct detailed flow field measurements to quantify the evolution of the unsteady vortices and turbulent flow structures around the gable-roof building model in tornado-like winds. The effects of important parameters, such as the distance between the centers of the tornado-like vortex and the test model and the orientation angles of the building model related to the tornado-like vortex, on the evolutions of the wake vortices and turbulent flow structures around the gable-roof building model as well as the wind loads induced by the tornado-like vortex were assessed quantitatively. The detailed flow field measurements were correlated with the surface pressure and wind load measurements to elucidate the underlying physics to gain further insight into flow-structure interactions between the gable-roof building model and tornado-like winds in order to provide more accurate prediction of wind damage potential to built structures. (orig.)

LIDAR Wind Speed Measurement Analysis and Feed-Forward Blade Pitch Control for Load Mitigation in Wind Turbines: January 2010--January 2011

Energy Technology Data Exchange (ETDEWEB)

Dunne, F.; Simley, E.; Pao, L.Y.

2011-10-01

This report examines the accuracy of measurements that rely on Doppler LIDAR systems to determine their applicability to wind turbine feed-forward control systems and discusses feed-forward control system designs that use preview wind measurements. Light Detection and Ranging (LIDAR) systems are able to measure the speed of incoming wind before it interacts with a wind turbine rotor. These preview wind measurements can be used in feed-forward control systems designed to reduce turbine loads. However, the degree to which such preview-based control techniques can reduce loads by reacting to turbulence depends on how accurately the incoming wind field can be measured. The first half of this report examines the accuracy of different measurement scenarios that rely on coherent continuous-wave or pulsed Doppler LIDAR systems to determine their applicability to feed-forward control. In particular, the impacts of measurement range and angular offset from the wind direction are studied for various wind conditions. A realistic case involving a scanning LIDAR unit mounted in the spinner of a wind turbine is studied in depth with emphasis on choices for scan radius and preview distance. The effects of turbulence parameters on measurement accuracy are studied as well. Continuous-wave and pulsed LIDAR models based on typical commercially available units were used in the studies present in this report. The second half of this report discusses feed-forward control system designs that use preview wind measurements. Combined feedback/feed-forward blade pitch control is compared to industry standard feedback control when simulated in realistic turbulent above-rated winds. The feed-forward controllers are designed to reduce fatigue loads, increasing turbine lifetime and therefore reducing the cost of energy. Three feed-forward designs are studied: non-causal series expansion, Preview Control, and optimized FIR filter. The input to the feed-forward controller is a measurement of

Grid Faults Impact on the Mechanical Loads of Active Stall Wind Turbine

DEFF Research Database (Denmark)

Iov, Florin; Cutululis, Nicolaos A.; Hansen, Anca D.

2008-01-01

Emphasis in this paper is on the fault ride-through operation impact on the wind turbines structural loads. Grid faults are typically simulated in power system simulation tools using simplified drive train mechanical model, approach which doesn't allow a thorough investigation of structural loads...... as the electrical design of the wind turbine response during grid faults. The two-step simulation procedure is assessed by means of a simulation example. The effect of a grid fault on the structural part of a typical fixed speed wind turbine, equipped with an induction generator, is assessed....

Directional Considerations for Extreme Wind Climatic Events in the ...

African Journals Online (AJOL)

This paper takes a look at the importance and role of probability concepts structural design of transmission line. The reliability of transmission structure is clearly a function of the maximum loads that may be imposed over the useful life of the structure. These loads are, more often than not, caused by the extreme atmospheric ...

Hydraulic Soft Yaw System Load Reduction and Prototype Results

DEFF Research Database (Denmark)

Stubkier, Søren; Pedersen, Henrik C.; Markussen, Kristian

2013-01-01

Introducing a hydraulic soft yaw concept for wind turbines leads to significant load reductions in the wind turbine structure. The soft yaw system operates as a shock absorption system on a car, hence absorbing the loading from turbulent wind conditions instead of leading them into the stiff wind...... turbine structure. Results presented shows fatigue reductions of up to 40% and ultimate load reduction of up to 19%. The ultimate load reduction increases even more when the over load protection system in the hydraulic soft yaw system is introduced and results show how the exact extreme load cut off...... operates. Further it is analyzed how the soft yaw system influence the power production of the turbine. It is shown that the influence is minimal, but at larger yaw errors the effect is possitive. Due to the implemeted functions in the hydraulic soft yaw system such as even load distribution on the pinions...

Calculation and characteristics analysis of blade pitch loads for large scale wind turbines

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

Based on the electric pitch system of large scale horizontal-axis wind turbines,the blade pitch loads coming mainly from centrifugal force,aerodynamic force and gravity are analyzed,and the calculation models for them are established in this paper.For illustration,a 1.2 MW wind turbine is introduced as a practical sample,and its blade pitch loads from centrifugal force,aerodynamic force and gravity are calculated and analyzed separately and synthetically.The research results showed that in the process of rotor rotating 360o,the fluctuation of blade pitch loads is similar to cosine curve when the rotor rotational speed,in-flow wind speed and pitch angle are constant.Furthermore,the amplitude of blade pitch load presents quite a difference at a different pitch angle.The ways of calculation for blade pitch loads are of the universality,and are helpful for further research of the individual pitch control system.

Design and Analysis of Wind Turbine Blade Hub using Aluminium Alloy AA 6061-T6

Science.gov (United States)

Ravikumar, S.; Jaswanthvenkatram, V.; Sai kumar, Y. J. N. V.; Sohaib, S. Md.

2017-05-01

This work presents the design and analysis of horizontal axis wind turbine blade hub using different material. The hub is very crucial part of the wind turbine, which experience the loads from the blades and the loads were transmitted to the main shaft. At present wind turbine is more expensive and weights more than a million pounds, with the nacelle, rotor hub and blades accounting for most of the weight. In this work Spheroidal graphite cast iron GGG 40.3 is replaced by aluminium alloy 6061-T6 to enhance the casting properties and also to improve the strength-weight ratio. This transition of material leads to reduction in weight of the wind turbine. All the loads caused by wind and extreme loads on the blades are transferred to the hub. Considering the IEC 61400-1 standard for defining extreme loads on the hub the stress and deflection were calculated on the hub by using Finite element Analysis. Result obtained from ANSYS is compared and discussed with the existing design.

On Small-Signal Stability of Wind Power System with Full-Load Converter Interfaced Wind Turbines

DEFF Research Database (Denmark)

Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård

2010-01-01

the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind turbine model with all grid relevant control functions is used in the study. Furthermore is the wind power plant......Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants. In this paper an analysis is presented which assess...... (WPP) equipped with a WPP voltage controller and comparisons are presented. The models of wind turbine and WPP voltage controller are kindly provided by Siemens Wind Power A/S for this work. The study is based on modal analysis which are complemented with simulations on the nonlinear system....

Calculation of design load for the MOD-5A 7.3 mW wind turbine system

Science.gov (United States)

Mirandy, L.; Strain, J. C.

1995-01-01

Design loads are presented for the General Electric MOD-SA wind turbine. The MOD-SA system consists of a 400 ft. diameter, upwind, two-bladed, teetered rotor connected to a 7.3 mW variable-speed generator. Fatigue loads are specified in the form of histograms for the 30 year life of the machine, while limit (or maximum) loads have been derived from transient dynamic analysis at critical operating conditions. Loads prediction was accomplished using state of the art aeroelastic analyses developed at General Electric. Features of the primary predictive tool - the Transient Rotor Analysis Code (TRAC) are described in the paper. Key to the load predictions are the following wind models: (1) yearly mean wind distribution; (2) mean wind variations during operation; (3) number of start/shutdown cycles; (4) spatially large gusts; and (5) spatially small gusts (local turbulence). The methods used to develop statistical distributions from load calculations represent an extension of procedures used in past wind programs and are believed to be a significant contribution to Wind Turbine Generator analysis. Test/theory correlations are presented to demonstrate code load predictive capability and to support the wind models used in the analysis. In addition MOD-5A loads are compared with those of existing machines. The MOD-5A design was performed by the General Electric Company, Advanced Energy Program Department, under Contract DEN3-153 with NASA Lewis Research Center and sponsored by the Department of Energy.

CFD simulations of wind loads on a container ship : Validation and impact of geometrical simplifactions

NARCIS (Netherlands)

Janssen, W.D.; Blocken, B.J.E.; van Wijhe, H.J.

2017-01-01

Due to the increasing windage area of container ships, wind loads are playing a more important role in navigating the ship at open sea and especially through harbor areas. This paper presents 3D steady RANS CFD simulations of wind loads on a container ship, validation with wind-tunnel measurements

Wind Energy Management System EMS Integration Project: Incorporating Wind Generation and Load Forecast Uncertainties into Power Grid Operations

Energy Technology Data Exchange (ETDEWEB)

Makarov, Yuri V.; Huang, Zhenyu; Etingov, Pavel V.; Ma, Jian; Guttromson, Ross T.; Subbarao, Krishnappa; Chakrabarti, Bhujanga B.

2010-01-01

The power system balancing process, which includes the scheduling, real time dispatch (load following) and regulation processes, is traditionally based on deterministic models. Since the conventional generation needs time to be committed and dispatched to a desired megawatt level, the scheduling and load following processes use load and wind and solar power production forecasts to achieve future balance between the conventional generation and energy storage on the one side, and system load, intermittent resources (such as wind and solar generation), and scheduled interchange on the other side. Although in real life the forecasting procedures imply some uncertainty around the load and wind/solar forecasts (caused by forecast errors), only their mean values are actually used in the generation dispatch and commitment procedures. Since the actual load and intermittent generation can deviate from their forecasts, it becomes increasingly unclear (especially, with the increasing penetration of renewable resources) whether the system would be actually able to meet the conventional generation requirements within the look-ahead horizon, what the additional balancing efforts would be needed as we get closer to the real time, and what additional costs would be incurred by those needs. To improve the system control performance characteristics, maintain system reliability, and minimize expenses related to the system balancing functions, it becomes necessary to incorporate the predicted uncertainty ranges into the scheduling, load following, and, in some extent, into the regulation processes. It is also important to address the uncertainty problem comprehensively by including all sources of uncertainty (load, intermittent generation, generators’ forced outages, etc.) into consideration. All aspects of uncertainty such as the imbalance size (which is the same as capacity needed to mitigate the imbalance) and generation ramping requirement must be taken into account. The latter

Controller design for a Wind Farm, Considering both Power and Load Aspects

DEFF Research Database (Denmark)

Soleimanzadeh, Maryam; Wisniewski, Rafal

2011-01-01

turbine. The control algorithm determines the reference signals for each individual wind turbine controller in two scenarios based on low and high wind speed. In low wind speed, the reference signals for rotor speed are adjusted, taking the trade-off between power maximization and load minimization...

Drivers and seasonal predictability of extreme wind speeds in the ECMWF System 4 and a statistical model

Science.gov (United States)

Walz, M. A.; Donat, M.; Leckebusch, G. C.

2017-12-01

As extreme wind speeds are responsible for large socio-economic losses in Europe, a skillful prediction would be of great benefit for disaster prevention as well as for the actuarial community. Here we evaluate patterns of large-scale atmospheric variability and the seasonal predictability of extreme wind speeds (e.g. >95th percentile) in the European domain in the dynamical seasonal forecast system ECMWF System 4, and compare to the predictability based on a statistical prediction model. The dominant patterns of atmospheric variability show distinct differences between reanalysis and ECMWF System 4, with most patterns in System 4 extended downstream in comparison to ERA-Interim. The dissimilar manifestations of the patterns within the two models lead to substantially different drivers associated with the occurrence of extreme winds in the respective model. While the ECMWF System 4 is shown to provide some predictive power over Scandinavia and the eastern Atlantic, only very few grid cells in the European domain have significant correlations for extreme wind speeds in System 4 compared to ERA-Interim. In contrast, a statistical model predicts extreme wind speeds during boreal winter in better agreement with the observations. Our results suggest that System 4 does not seem to capture the potential predictability of extreme winds that exists in the real world, and therefore fails to provide reliable seasonal predictions for lead months 2-4. This is likely related to the unrealistic representation of large-scale patterns of atmospheric variability. Hence our study points to potential improvements of dynamical prediction skill by improving the simulation of large-scale atmospheric dynamics.

Fatigue Load Modeling and Control for Wind Turbines based on Hysteresis Operators

DEFF Research Database (Denmark)

Barradas Berglind, Jose de Jesus; Wisniewski, Rafal; Soltani, Mohsen

2015-01-01

method based on hysteresis operators, which can be used in control loops. Furthermore, we propose a model predictive control (MPC) strategy that incorporates the online fatigue estimation through the objective function, where the ultimate goal in mind is to reduce the fatigue load of the wind turbine......The focus of this work is on fatigue load modeling and controller design for the wind turbine level. The main purpose is to include a model of the damage effects caused by the fatigue of the wind turbine components in the controller design process. This paper addresses an online fatigue estimation...

Small-Signal Stability of Wind Power System With Full-Load Converter Interfaced Wind Turbines

DEFF Research Database (Denmark)

Knüppel, Thyge; Nielsen, Jørgen Nygaard; Jensen, Kim Høj

2012-01-01

Small-signal stability analysis of power system oscillations is a well established field within power system analysis, but not much attention has yet been paid to systems with a high penetration of wind turbines and with large wind power plants (WPP). In this paper a comprehensive analysis...... is presented which assesses the impact of full-load converter interfaced wind turbines on power system small-signal stability. The study is based on a 7 generator network with lightly damped inter-area modes. A detailed wind turbine (WT) model with all grid relevant control functions is used in the study....... The WT is, furthermore, equipped with a park level WPP voltage controller and comparisons are presented. The WT model for this work is a validated dynamic model of the 3.6 MW Siemens Wind Power WT. The study is based on modal analysis which is complemented with time domain simulations on the nonlinear...

IDENTIFICATION OF WIND LOAD APPLIED TO THREE-DIMENSIONAL STRUCTURES BY VIRTUE OF ITS SIMULATION IN THE WIND TUNNEL

Directory of Open Access Journals (Sweden)

Doroshenko Sergey Aleksandrovich

2012-10-01

Full Text Available The authors discuss wind loads applied to a set of two buildings. The wind load is simulated with the help of the wind tunnel. In the Russian Federation, special attention is driven to the aerodynamics of high-rise buildings and structures. According to the Russian norms, identification of aerodynamic coefficients for high-rise buildings, as well as the influence of adjacent buildings and structures, is performed on the basis of models of structures exposed to wind impacts simulated in the wind tunnel. This article deals with the results of the wind tunnel test of buildings. The simulation was carried out with the involvement of a model of two twenty-three storied buildings. The experiment was held in a wind tunnel of the closed type at in the Institute of Mechanics of Moscow State University. Data were compared at the zero speed before and after the experiment. LabView software was used to process the output data. Graphs and tables were developed in the Microsoft Excel package. GoogleSketchUp software was used as a visualization tool. The three-dimensional flow formed in the wind tunnel can't be adequately described by solving the two-dimensional problem. The aerodynamic experiment technique is used to analyze the results for eighteen angles of the wind attack.

Flap controllers applied on the OffshoreWindChina (OWC) 5MW reference wind turbine for Chinese typhoon conditions

DEFF Research Database (Denmark)

Barlas, Athanasios

The report describes the development of flap controllers applied on the OffshoreWindChina (OWC) 5MW reference wind turbine for Chinese typhoon conditions. Optimal flap controllers are designed and tuned based on linear aeroelastic models from HawcStab2. The controllers are evaluated in normal......, parked and storm conditions, targeting the alleviation of fatigue and extreme loads....

Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

Directory of Open Access Journals (Sweden)

Judit Lecina-Diaz

Full Text Available Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1 determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together and (2 ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires. The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn

Extreme fire severity patterns in topographic, convective and wind-driven historical wildfires of Mediterranean pine forests.

Science.gov (United States)

Lecina-Diaz, Judit; Alvarez, Albert; Retana, Javier

2014-01-01

Crown fires associated with extreme fire severity are extremely difficult to control. We have assessed fire severity using differenced Normalized Burn Ratio (dNBR) from Landsat imagery in 15 historical wildfires of Pinus halepensis Mill. We have considered a wide range of innovative topographic, fuel and fire behavior variables with the purposes of (1) determining the variables that influence fire severity patterns among fires (considering the 15 wildfires together) and (2) ascertaining whether different variables affect extreme fire severity within the three fire types (topographic, convective and wind-driven fires). The among-fires analysis showed that fires in less arid climates and with steeper slopes had more extreme severity. In less arid conditions there was more crown fuel accumulation and closer forest structures, promoting high vertical and horizontal fuel continuity and extreme fire severity. The analyses carried out for each fire separately (within fires) showed more extreme fire severity in areas in northern aspects, with steeper slopes, with high crown biomass and in climates with more water availability. In northern aspects solar radiation was lower and fuels had less water limitation to growth which, combined with steeper slopes, produced more extreme severity. In topographic fires there was more extreme severity in northern aspects with steeper slopes and in areas with more water availability and high crown biomass; in convection-dominated fires there was also more extreme fire severity in northern aspects with high biomass; while in wind-driven fires there was only a slight interaction between biomass and water availability. This latter pattern could be related to the fact that wind-driven fires spread with high wind speed, which could have minimized the effect of other variables. In the future, and as a consequence of climate change, new zones with high crown biomass accumulated in non-common drought areas will be available to burn as extreme

Probabilistic model for multi-axial load combinations for wind turbines

DEFF Research Database (Denmark)

Dimitrov, Nikolay Krasimirov

2016-01-01

into a periodic part and a perturbation term, where each part has a known probability distribution. The proposed model shows good agreement with simulated data under stationary conditions, and a design load envelope based on this model is comparable to the load envelope estimated using the standard procedure...... for determining contemporaneous loads. Using examples with simulated loads on a 10 MW wind turbine,the behavior of the bending moments acting on a blade section is illustrated under different conditions.The loading direction most critical for material failure is determined using a finite-element model...

Wind Energy Management System Integration Project Incorporating Wind Generation and Load Forecast Uncertainties into Power Grid Operations

Energy Technology Data Exchange (ETDEWEB)

Makarov, Yuri V.; Huang, Zhenyu; Etingov, Pavel V.; Ma, Jian; Guttromson, Ross T.; Subbarao, Krishnappa; Chakrabarti, Bhujanga B.

2010-09-01

The power system balancing process, which includes the scheduling, real time dispatch (load following) and regulation processes, is traditionally based on deterministic models. Since the conventional generation needs time to be committed and dispatched to a desired megawatt level, the scheduling and load following processes use load and wind power production forecasts to achieve future balance between the conventional generation and energy storage on the one side, and system load, intermittent resources (such as wind and solar generation) and scheduled interchange on the other side. Although in real life the forecasting procedures imply some uncertainty around the load and wind forecasts (caused by forecast errors), only their mean values are actually used in the generation dispatch and commitment procedures. Since the actual load and intermittent generation can deviate from their forecasts, it becomes increasingly unclear (especially, with the increasing penetration of renewable resources) whether the system would be actually able to meet the conventional generation requirements within the look-ahead horizon, what the additional balancing efforts would be needed as we get closer to the real time, and what additional costs would be incurred by those needs. In order to improve the system control performance characteristics, maintain system reliability, and minimize expenses related to the system balancing functions, it becomes necessary to incorporate the predicted uncertainty ranges into the scheduling, load following, and, in some extent, into the regulation processes. It is also important to address the uncertainty problem comprehensively, by including all sources of uncertainty (load, intermittent generation, generators’ forced outages, etc.) into consideration. All aspects of uncertainty such as the imbalance size (which is the same as capacity needed to mitigate the imbalance) and generation ramping requirement must be taken into account. The latter unique

Specific gas turbines for extreme peak-load

International Nuclear Information System (INIS)

Bellot, C.

1992-12-01

As with other European countries, in France peak consumption of electricity occurs during winter. Due to the increasing use of electricity for domestic heating, outside temperature greatly influences consumption (1 200 MW for a drop of 1 deg C). To meet requirements during cold spells, EDF has sought to determine which special facilities are best suited for extreme peak load conditions (i.e. offering short lifespan and minimum capital cost) and has studied the possibility of installing generation means in transformer substations (20 kV). This solution does not require extension of networks since these means are scattered near consumption areas. An experiment conducted on 3 Diesel generators of 800 kWe each at Senlis revealed some of the disadvantages of Diesel (maintenance requirements, polluting emissions and noise). EDF then examined, for this same application, the use of gas turbines, for which these drawbacks are significantly less. A study carried out under an EDF contract by the French manufacturer TURBOMECA showed that it is possible to design a small capacity gas turbine that can compete with Diesel generators, and that capital costs could be minimized by simplifying the machine, adapting its lifespan to extreme peak load needs, and taking advantage of lower cost provided by mass production. TURBOMECA defined the machine's characteristics (2 MW, 6 000 hours lifespan) and aerodynamic flow. It also estimated the cost of packaging. In terms of overall cost (including initial investment, maintenance and fuel) the gas turbine appears cheaper than Diesel generators for annual operation times of less than one hundred hours, which corresponds closely with extreme peak load use. The lower maintenance costs and the better availability counterbalance the higher capital cost (+6%) and the greater consumption (+50%). (author). 7 figs

Model Predictive Control for Load Frequency Control with Wind Turbines

Directory of Open Access Journals (Sweden)

Yi Zhang

2015-01-01

Full Text Available Reliable load frequency (LFC control is crucial to the operation and design of modern electric power systems. Considering the LFC problem of a four-area interconnected power system with wind turbines, this paper presents a distributed model predictive control (DMPC based on coordination scheme. The proposed algorithm solves a series of local optimization problems to minimize a performance objective for each control area. The scheme incorporates the two critical nonlinear constraints, for example, the generation rate constraint (GRC and the valve limit, into convex optimization problems. Furthermore, the algorithm reduces the impact on the randomness and intermittence of wind turbine effectively. A performance comparison between the proposed controller with and that without the participation of the wind turbines is carried out. Good performance is obtained in the presence of power system nonlinearities due to the governors and turbines constraints and load change disturbances.

Measuring power output intermittency and unsteady loading in a micro wind farm model

OpenAIRE

Bossuyt, Juliaan; Howland, Michael; Meneveau, Charles; Meyers, Johan

2016-01-01

In this study porous disc models are used as a turbine model for a wind-tunnel wind farm experiment, allowing the measurement of the power output, thrust force and spatially averaged incoming velocity for every turbine. The model's capabilities for studying the unsteady turbine loading, wind farm power output intermittency and spatio temporal correlations between wind turbines are demonstrated on an aligned wind farm, consisting of 100 wind turbine models.

The Effects of Load Carriage and Muscle Fatigue on Lower-Extremity Joint Mechanics

Science.gov (United States)

Wang, He; Frame, Jeff; Ozimek, Elicia; Leib, Daniel; Dugan, Eric L.

2013-01-01

Military personnel are commonly afflicted by lower-extremity overuse injuries. Load carriage and muscular fatigue are major stressors during military basic training. Purpose: To examine effects of load carriage and muscular fatigue on lower-extremity joint mechanics during walking. Method: Eighteen men performed the following tasks: unloaded…

Load Flow Analysis of Hybrid AC-DC Power System with Offshore Wind Power

DEFF Research Database (Denmark)

Dhua, Debasish; Huang, Shaojun; Wu, Qiuwei

2017-01-01

The offshore wind power has received immense attention because of higher wind speed and lower opposition for construction. A wide range of combinations of high-voltage ACDC transmission have been proposed for integrating offshore wind farms and long-distance power transmission. This paper...... is to model such hybrid AC-DC systems including the interfacing converters, which have several control parameters that can change the load flow of the hybrid systems. Then, the paper proposes a Load Flow algorithm based on the Newton-Raphson method, which covers three different section types...

Shear and Turbulence Estimates for Calculation of Wind Turbine Loads and Responses Under Hurricane Strength Winds

Science.gov (United States)

Kosovic, B.; Bryan, G. H.; Haupt, S. E.

2012-12-01

Schwartz et al. (2010) recently reported that the total gross energy-generating offshore wind resource in the United States in waters less than 30m deep is approximately 1000 GW. Estimated offshore generating capacity is thus equivalent to the current generating capacity in the United States. Offshore wind power can therefore play important role in electricity production in the United States. However, most of this resource is located along the East Coast of the United States and in the Gulf of Mexico, areas frequently affected by tropical cyclones including hurricanes. Hurricane strength winds, associated shear and turbulence can affect performance and structural integrity of wind turbines. In a recent study Rose et al. (2012) attempted to estimate the risk to offshore wind turbines from hurricane strength winds over a lifetime of a wind farm (i.e. 20 years). According to Rose et al. turbine tower buckling has been observed in typhoons. They concluded that there is "substantial risk that Category 3 and higher hurricanes can destroy half or more of the turbines at some locations." More robust designs including appropriate controls can mitigate the risk of wind turbine damage. To develop such designs good estimates of turbine loads under hurricane strength winds are essential. We use output from a large-eddy simulation of a hurricane to estimate shear and turbulence intensity over first couple of hundred meters above sea surface. We compute power spectra of three velocity components at several distances from the eye of the hurricane. Based on these spectra analytical spectral forms are developed and included in TurbSim, a stochastic inflow turbulence code developed by the National Renewable Energy Laboratory (NREL, http://wind.nrel.gov/designcodes/preprocessors/turbsim/). TurbSim provides a numerical simulation including bursts of coherent turbulence associated with organized turbulent structures. It can generate realistic flow conditions that an operating turbine

Wave loads on offshore wind turbines: Accurate tools and structural response

DEFF Research Database (Denmark)

Bredmose, Henrik

2014-01-01

Can the design models for offshore wind turbine wave loads be improved? And how will that change the overall load picture? Core questions of the Wave Loads project which was finalised in 2013 with two PhD theses, response calculations for jackets and monopiles, a detailed set of experiments and a3D...... coupled CFD wave solver...

A stochastic framework for the grid integration of wind power using flexible load approach

International Nuclear Information System (INIS)

Heydarian-Forushani, E.; Moghaddam, M.P.; Sheikh-El-Eslami, M.K.; Shafie-khah, M.; Catalão, J.P.S.

2014-01-01

Highlights: • This paper focuses on the potential of Demand Response Programs (DRPs) to contribute to flexibility. • A stochastic network constrained unit commitment associated with DR is presented. • DR participation levels and electricity tariffs are evaluated on providing a flexible load profile. • Novel quantitative indices for evaluating flexibility are defined to assess the success of DRPs. • DR types and customer participation levels are the main factors to modify the system load profile. - Abstract: Wind power integration has always been a key research area due to the green future power system target. However, the intermittent nature of wind power may impose some technical and economic challenges to Independent System Operators (ISOs) and increase the need for additional flexibility. Motivated by this need, this paper focuses on the potential of Demand Response Programs (DRPs) as an option to contribute to the flexible operation of power systems. On this basis, in order to consider the uncertain nature of wind power and the reality of electricity market, a Stochastic Network Constrained Unit Commitment associated with DR (SNCUCDR) is presented to schedule both generation units and responsive loads in power systems with high penetration of wind power. Afterwards, the effects of both price-based and incentive-based DRPs are evaluated, as well as DR participation levels and electricity tariffs on providing a flexible load profile and facilitating grid integration of wind power. For this reason, novel quantitative indices for evaluating flexibility are defined to assess the success of DRPs in terms of wind integration. Sensitivity studies indicate that DR types and customer participation levels are the main factors to modify the system load profile to support wind power integration

Wind-induced transmission tower foundation loads. A field study-design code comparison

Energy Technology Data Exchange (ETDEWEB)

Savory, E. [Department of Mechanical and Materials Engineering, University of Western Ontario, London, Ont. (Canada); Parke, G.A.R.; Disney, P.; Toy, N. [School of Engineering, University of Surrey, Guildford, Surrey GU2 7XH (United Kingdom)

2008-06-15

This paper presents a comparison between the wind-induced foundation loads measured on a type L6 transmission line tower during a field study in the UK and those computed using the UK Code of Practice for lattice tower and transmission line design (BS8100). In this work, the Code provisions have been generalised to give the wind-induced strain in each of the tower legs immediately above the foundation as a function of wind direction and wind speed at the top of the tower. The complete data set from the field monitoring has been decomposed to provide a similar formulation for comparison purposes. The analysis shows excellent agreement between the Code calculations and the measured results, within the overall accuracy of the field data. This indicates that, at least for the tower type examined here, the existing design Code provides a reliable transformation of the local wind speed at the top of the tower into tension and compression loads on the foundations. (author)

The design of models for cryogenic wind tunnels. [mechanical properties and loads

Science.gov (United States)

Gillespie, V. P.

1977-01-01

Factors to be considered in the design and fabrication of models for cryogenic wind tunnels include high model loads imposed by the high operating pressures, the mechanical and thermodynamic properties of materials in low temperature environments, and the combination of aerodynamic loads with the thermal environment. Candidate materials are being investigated to establish criteria for cryogenic wind tunnel models and their installation. Data acquired from these tests will be provided to users of the National Transonic Facility.

Optimized Power Dispatch in Wind Farms for Power Maximizing Considering Fatigue Loads

DEFF Research Database (Denmark)

Zhang, Baohua; N. Soltani, Mohsen; Hu, Weihao

2018-01-01

Wake effects in a wind farm (WF) include the wind velocity deficit and added turbulence. The wind velocity deficit may bring significant loss of the wind power and the added turbulence may cause extra fatigue load on the wind turbines (WTs). Inclusion of the wake effects in the wind farm control...... at a series of turbulence intensity, mean wind speed and active power reference to form a lookup table, which is used for the WF control. The proposed strategy is compared with WT MPPT control strategy and WF MPPT control strategy. The simulation results show the effectiveness of the proposed strategy....

Using wind speed from a blade-mounted flow sensor for power and load assessment on modern wind turbines

Directory of Open Access Journals (Sweden)

M. M. Pedersen

2017-11-01

Full Text Available In this paper an alternative method to evaluate power performance and loads on wind turbines using a blade-mounted flow sensor is investigated. The hypothesis is that the wind speed measured at the blades has a high correlation with the power and loads such that a power or load assessment can be performed from a few hours or days of measurements.In the present study a blade-mounted five-hole pitot tube is used as the flow sensor as an alternative to the conventional approach, where the reference wind speed is either measured at a nearby met mast or on the nacelle using lidar technology or cup anemometers. From the flow sensor measurements, an accurate estimate of the wind speed at the rotor plane can be obtained. This wind speed is disturbed by the presence of the wind turbine, and it is therefore different from the free-flow wind speed. However, the recorded wind speed has a high correlation with the actual power production as well as the flap-wise loads as it is measured close to the blade where the aerodynamic forces are acting.Conventional power curves are based on at least 180 h of 10 min mean values, but using the blade-mounted flow sensor both the observation average time and the overall assessment time can potentially be shortened. The basis for this hypothesis is that the sensor is able to provide more observations with higher accuracy, as the sensor follows the rotation of the rotor and because of the high correlation between the flow at the blades and the power production. This is the research question addressed in this paper.The method is first tested using aeroelastic simulations where the dependence of the radial position and effect of multiple blade-mounted flow sensors are also investigated. Next the method is evaluated on the basis of full-scale measurements on a pitch-regulated, variable-speed 3.6 MW wind turbine.It is concluded that the wind speed derived from the blade-mounted flow sensor is highly correlated with the

Frequency-domain characteristics of aerodynamic loads of offshore floating vertical axis wind turbines

DEFF Research Database (Denmark)

Borg, Michael; Collu, M.

2015-01-01

The re-emerging interest in vertical axis wind turbines for floating offshore applications has led to a need to investigate the relatively complex dynamics of such floating offshore structures. Through the use of a coupled model of dynamics this article investigates the frequency......-domain characteristics of floating vertical axis wind turbine aerodynamic loads. The impact of platform induced motion on aerodynamic loads is discussed in detail, with results indicating an increase in aerodynamic loads of several orders of magnitude over the range of frequencies usually containing significant wave...

Assessment of load extrapolation methods for wind turbines

DEFF Research Database (Denmark)

Toft, H.S.; Sørensen, John Dalsgaard; Veldkamp, D.

2010-01-01

an approximate analytical solution for the distribution of the peaks is given by Rice. In the present paper three different methods for statistical load extrapolation are compared with the analytical solution for one mean wind speed. The methods considered are global maxima, block maxima and the peak over...

Assessment of Load Extrapolation Methods for Wind Turbines

DEFF Research Database (Denmark)

Toft, Henrik Stensgaard; Sørensen, John Dalsgaard; Veldkamp, Dick

2011-01-01

, an approximate analytical solution for the distribution of the peaks is given by Rice. In the present paper, three different methods for statistical load extrapolation are compared with the analytical solution for one mean wind speed. The methods considered are global maxima, block maxima, and the peak over...

Scaling Issues in the Determination of Wind loads on Lattice Masts

DEFF Research Database (Denmark)

Koss, Holger; Srouji, Robin G.

2015-01-01

The paper presents a study conducted to investigate the influence of geometric scale and flow condition on the wind load coefficients for lattice masts structures. An initial study in 2008 on a full size mast section indicated a possible contingency, which could be used to add equipment on teleco......The paper presents a study conducted to investigate the influence of geometric scale and flow condition on the wind load coefficients for lattice masts structures. An initial study in 2008 on a full size mast section indicated a possible contingency, which could be used to add equipment...

Dynamic modeling and analysis of load sharing characteristics of wind turbine gearbox

Directory of Open Access Journals (Sweden)

Pengxing Yi

2015-03-01

Full Text Available A coupled dynamic model, which contains helical gears-shafts-bearings for a wind turbine gearbox transmission system, was built considering nonlinear factors of the time-varying mesh stiffness, the external varying load, and the dynamic transmission error at first. The model is confirmed to be right after comparing the theoretical data with the experimental load sharing values, and also it is found that the static load sharing is conservative to evaluate the non-equilibrium effect of a planetary gear system. Besides, the analyzing results of the influence of average error and amplitude error on the load sharing show that the load sharing could be decreased if the error goes up a little. Then, by means of treating the static tracing point as the dynamic initial values, we analyzed the initial position’s influence on the load sharing of transmission system to provide a theoretical basis of load sharing control. Furthermore, we explored the influence of high-speed shaft position angle on the load sharing and the dynamic load factor of gears fixed on the parallel shafts. The results provide useful theoretical guidelines for the design of parallel shaft gear system in the wind turbines.

Calculating the sensitivity of wind turbine loads to wind inputs using response surfaces

DEFF Research Database (Denmark)

Rinker, Jennifer M.

2016-01-01

at a low computational cost. Sobol sensitivity indices (SIs) can then be calculated with relative ease using the calibrated response surface. The proposed methodology is demonstrated by calculating the total sensitivity of the maximum blade root bending moment of the WindPACT 5 MW reference model to four......This paper presents a methodology to calculate wind turbine load sensitivities to turbulence parameters through the use of response surfaces. A response surface is a high-dimensional polynomial surface that can be calibrated to any set of input/output data and then used to generate synthetic data...... turbulence input parameters: a reference mean wind speed, a reference turbulence intensity, the Kaimal length scale, and a novel parameter reflecting the nonstationarity present in the inflow turbulence. The input/output data used to calibrate the response surface were generated for a previous project...

Extreme winds in Denmark

DEFF Research Database (Denmark)

Kristensen, L.; Rathmann, O.; Hansen, S.O.

2000-01-01

(Technical Report, Danish Technical press, 1970) and by Abild (Technical Report R-522 (EN), Riso National Laboratory, 1994). A short discussion of the wind storm on the 3rd of December 1999 is included. It is demonstrated how the data can be applied to non-standard situations where the roughness length......Wind-speed data from four sites in Denmark have been analyzed in order to obtain estimates of the basic wind velocity, defined as the 50 yr wind speed (10 min averages) under standard conditions, i.e., 10 m over a homogeneous terrain with the roughness length 0.05 m, The sites are Skjern (15 yr......), Kegnaes (7 yr), Sprogo (20 yr), and Tystofte (16 yr). The measured data are wind speed, wind direction, temperature and pressure. The wind records are cleaned for terrain effects by means of WASP (Mortensew ct al., Technical Report I-666 (EN), Riso National Laboratory, 1993. Vol. 2. User's Guide...

Uncertainties of the 50-year wind from short time series using generalized extreme value distribution and generalized Pareto distribution

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Mann, Jakob; Rathmann, Ole

2015-01-01

This study examines the various sources to the uncertainties in the application of two widely used extreme value distribution functions, the generalized extreme value distribution (GEVD) and the generalized Pareto distribution (GPD). The study is done through the analysis of measurements from...... as a guideline for applying GEVD and GPD to wind time series of limited length. The data analysis shows that, with reasonable choice of relevant parameters, GEVD and GPD give consistent estimates of the return winds. For GEVD, the base period should be chosen in accordance with the occurrence of the extreme wind...

Validated Loads Prediction Models for Offshore Wind Turbines for Enhanced Component Reliability

DEFF Research Database (Denmark)

Koukoura, Christina

To improve the reliability of offshore wind turbines, accurate prediction of their response is required. Therefore, validation of models with site measurements is imperative. In the present thesis a 3.6MW pitch regulated-variable speed offshore wind turbine on a monopole foundation is built...... are used for the modification of the sub-structure/foundation design for possible material savings. First, the background of offshore wind engineering, including wind-wave conditions, support structure, blade loading and wind turbine dynamics are presented. Second, a detailed description of the site...

Inflow characteristics associated with high-blade-loading events in a wind farm

Science.gov (United States)

Kelley, N. D.

1993-07-01

The stochastic characteristics of the turbulent inflow have been shown to be of major significance in the accumulation of fatigue in wind turbines. Because most of the wind turbine installations in the U.S. have taken place in multi-turbine or windfarm configurations, the fatigue damage associated with the higher turbulence levels within such arrangements must be taken into account when making estimates of component service lifetimes. The simultaneous monitoring of two adjacent wind turbines over a wide range of turbulent inflow conditions has given the authors more confidence in describing the structural load distributions that can be expected in such an environment. The adjacent testing of the two turbines allowed the authors to postulate that observed similarities in the response dynamics and load distributions could be considered quasi-universal, while the dissimilarities could be considered to result from the differing design of the rotors. The format has also allowed them to begin to define appropriate statistical load distribution models for many of the critical components in which fatigue is a major driver of the design. In addition to the adjacent turbine measurements, they also briefly discuss load distributions measured on a teetered-hub turbine.

Reduction mechanism of dynamic loads on down wind rotor; Furyoku hatsuden system down wind rotor no doteki kaju no keigen kiko ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Seki, K; Shimizu, Y; Yasui, T [Tokai University, Tokyo (Japan)

1997-11-25

Dynamic force on blades in a large wind mill changes with rotational speed for various reasons, such as wind shear that causes vertical distribution of wind velocity or titling angle. Therefore, a 2-blade system on a teetered hub is a practical selection for the coned, down-wind type. Use of teetered axis greatly reduces bending moment in the flap direction and that at the axis of rotation. An attempt was made to understand dynamic loads by inertial force resulting from oscillation of the blade rotating on the teetered axis, and thereby to avoid them. The in-plane load can be diminished to zero when the teetered axis is coincided with the center of gravity, but generally cannot be avoided when the blade is strained significantly, except it is operated at the rated condition. The in-plane load and bending moment can be avoided, when rotational freedom is given around the y axis. Dynamic load on a down-wind rotor can be avoided by use of universal joint. 3 refs., 6 figs.

Assessment of Gearbox Operational Loads and Reliability under High Mean Wind Speeds

OpenAIRE

Dabrowski, Dariusz; Natarajan, Anand

2015-01-01

This paper investigates the dynamic loads occurring in the drivetrain of wind turbines with a focus on offshore applications. Herein a model of the gearbox of the 5 MW wind turbine is presented. The model is developed in a multi-body framework using commercial software MSC ADAMS. Validation of the model was based on the experimental data provided by NREL for 750 kW prototype gearbox. Failures of gearboxes caused by high dynamic loads have a significant influence on the cost of operation of wi...

Investigation of the effect of bending twisting coupling on the loads in wind turbines with superelement blade definition

International Nuclear Information System (INIS)

Gözcü, M O; Kayran, A

2014-01-01

Bending-twisting coupling in the composite blades is exploited for load alleviation in the whole turbine system. For the purpose of the study, inverse design of a reference blade is performed such that sectional beam properties of the 3D blade design approximately match the sectional beam properties of NREL's 5MW turbine blade. In order to appropriately account for the bending-twisting coupling effect, dynamic superelement of the blade is created and introduced into the multi-body dynamic model of the wind turbine system. Initially, a comparative study is conducted on the performance of wind turbines which have blades defined as superelements and geometrically nonlinear beams, and conclusions are inferred with regard to the appropriateness of the use of superelement blade definition in the transient analysis of the 5MW wind turbine system that is set up in the present study. Multi-body dynamic simulations of the wind turbine system are performed for the power production load case with the constant wind and the normal turbulence model as external wind loadings. For the internal loads, fatigue damage equivalent load is used as the metric to assess the effect of bending-twisting coupling on the load alleviation in the whole wind turbine system. Results show that in the overall, through the bending-twisting coupling induced with the use of off-axis plies in the main spar caps of the blade, damage equivalent loads associated with the critical load components can be reduced in the wind turbine system

Full scale investigation of the wind loads on a light-weight building-integrated photovoltaic system

NARCIS (Netherlands)

Geurts, C.P.W.; Bronkhorst, A.J.; Bentum, C.A. van

2017-01-01

The wind loads on solar energy systems are crucial for the engineering of the panels, substructure and fixings. There is a demand for aesthetically more acceptable solutions such as frameless solar systems. For these frameless systems, the wind loads are carried by the panels themselves. Combined

Artificial bee colony algorithm for economic load dispatch with wind power energy

Directory of Open Access Journals (Sweden)

Safari Amin

2016-01-01

Full Text Available This paper presents an efficient Artificial Bee Colony (ABC algorithm for solving large scale economic load dispatch (ELD problems in power networks. To realize the ELD, the valve-point loading effect, system load demand, power losses, ramp rate limits and prohibited operation zones are considered here. Simulations were performed on four different power systems with 3, 6, 15 and 40 generating units and the results are compared with two forms of power systems, one power system is with a wind power generator and other power system is without a wind power generator. The results of this study reveal that the proposed approach is able to find appreciable ELD solutions than those of previous algorithms.

Wind-wave induced dynamic response analysis for motions and mooring loads of a spar-type offshore floating wind turbine

Institute of Scientific and Technical Information of China (English)

马钰; 肖龙飞; 胡志强

2014-01-01

Due to the energy crisis and the environmental issues like pollution and global warming, the exploration for renewable and clean energies becomes crucial. The offshore floating wind turbines (OFWTs) draw a great deal of attention recently as a means to exploit the steadier and stronger wind resources available in deep water seas. This paper studies the hydrodynamic characteristics of a spar-type wind turbine known as the OC3-Hywind concept and the dynamic responses of the turbine. Response characteristics of motions and mooring loads of the system under different sea states are evaluated and the effects of the loads induced by the wind and the wave on the system are discussed. The calculations are carried out with the numerical simulation code FAST in the time domain and the frequency analysis is made by using the FFT method. The results and the conclusions from this paper might help better understand the behavior characteristics of the floating wind turbine system under actual ocean environments and provide valuable data in design and engineering practice.

Impact of extreme load requirements and quality assurance on nuclear power plant costs

International Nuclear Information System (INIS)

Stevenson, J.D.

1993-01-01

Definitive costs, applicable to nuclear power plant concrete structures, as a function of National Regulatory Requirements, standardization, the effect of extreme load design associated with both design basis accidents and extreme external events and quality assurance are difficult to develop since such effects are interrelated and not only differ widely from country to country, project to project but also vary in time. Table 1 shows an estimate of the of the overall plant cost effects of external event extreme load design on nuclear power plant design for the U.S -and selected foreign countries for which experience with LWRs exist- Germany is the most expensive primarily due to a military aircraft crash resistance. However, the German requirement for 4 safeguards trains rather than 2 and the containment design requirement to consider one Steam Generator blowdown concurrent with a RCS blowdown. This presentation will concentrate on the direct current impact extreme load design and quality assurance have on concrete structures, systems and components for nuclear plants. This presentation is considered timely due to the increased interest in the c potential backfit of Eastern European nuclear power stations of the WWER 440 and WWER 1000 types which typically did not consider the extreme loads identified in Table 1 and accident loads in Table 3 and quality assurance in Table 5 in their original design. Concrete structures in particular are highlighted because they typically form the last barrier to radioactive release from the containment and other Safety Related Structures

Extreme wind estimate for Hornsea wind farm

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo

The purpose of this study is to provide estimation of the 50-year winds of 10 min and 1-s gust value at hub height of 100 m, as well as the design parameter shear exponent for the Hornsea offshore wind farm. The turbulence intensity required for estimating the gust value is estimated using two...... approaches. One is through the measurements from the wind Doppler lidar, WindCube, which implies serious uncertainty, and the other one is through similarity theory for the atmospheric surface layer where the hub height is likely to belong to during strong storms. The turbulence intensity for storm wind...... strength is taken as 0.1. The shear exponents at several heights were calculated from the measurements. The values at 100 m are less than the limit given by IEC standard for all sectors. The 50-year winds have been calculated from various global reanalysis and analysis products as well as mesoscale models...

Wind load effects on high rise buildings in Peninsular Malaysia

Science.gov (United States)

Nizamani, Z.; Thang, K. C.; Haider, B.; Shariff, M.

2018-04-01

Wind is a randomly varying dynamic phenomenon composed of a multitude of eddies of varying sizes and rotational characteristics along a general stream of air moving relative to the ground. These eddies give wind its gustiness, creating fluctuation and results in a complex flow characteristics. The wind vector at any point can be regarded as the sum of mean wind vector and the fluctuation components. These components not only vary with height but also dependant on the approach terrain and topography. Prevailing wind exerts pressure onto the structural surfaces. The effects of wind pressure in the form of shear and bending moments are found to be a major problem in structural failure. This study aims to study the effects of wind load on a fifteen-storey high rise building using EN 1991-1-4 code and MS1553:2002. The simulation results showed that by increasing the wind speed, the storey resultant forces, namely storey shear and storey moment increases significantly. Furthermore, simulation results according to EN 1991-1-4 yield higher values compared to the simulation results according to MS1553:2002.

Analysis of wind driven self-excited induction generator supplying isolated DC loads

Directory of Open Access Journals (Sweden)

Khaled S. Sakkoury

2017-05-01

Full Text Available This paper presents the analysis, modelling and simulation of wind-driven self-excited induction generator (SEIG. The three-phase SEIG is driven by a variable-speed prime mover to represent a wind turbine. Also, the paper investigates the dynamic performance of the SEIG during start-up, increasing or decreasing the load or rotor speed. The value of the excitation capacitance required for the SEIG is calculated to give suitable saturation level to assure self-excitation and to avoid heavy saturation levels. Matching of the maximum power available from the wind turbine is performed through varying the load value. The effect of AC–DC power conversion on the generator is investigated. The system simulation is carried out using MATLAB/SIMULINK toolbox program.

Material matters: Controllable rubber trailing edge flap regulates load on wind turbine blades

DEFF Research Database (Denmark)

Aagaard Madsen, Helge

2010-01-01

In wind farms, nearby wind turbines exert considerable influence and generate turbulence on turbine blades. Because the blades are so long, there can be considerable differences in localized loading from the gusts along the blade. The Risø DTU researchers has developed a controllable rubber trail...... in an open jet wind tunnel shows promising results. In the wind tunnel, it is possible to regulate the wind speed as well as turn the blade profile to simulate a change in wind direction in relation to the profile....

76 FR 74776 - Forum-Trends in Extreme Winds, Waves, and Extratropical Storms Along the Coasts

Science.gov (United States)

2011-12-01

... Winds, Waves, and Extratropical Storms Along the Coasts AGENCY: National Environmental Satellite, Data...-extratropical-storms/home . FOR FURTHER INFORMATION CONTACT: Brooke Stewart, National Climatic Data Center, 151.../noaa.gov/extreme-winds-waves-extratropical-storms/home . Topics To Be Addressed This forum will address...

Coordination of Voltage and Frequency Feedback in Load-Frequency Control Capability of Wind Turbine

DEFF Research Database (Denmark)

Hoseinzadeh, Bakhtyar; Silva, Filipe Faria Da; Bak, Claus Leth

2014-01-01

In close future, with high Wind Energy (WE) penetration in the power system, the burden of Load-Frequency Control (LFC) is gradually shifted to Variable Speed Wind Turbines (VSWTs). In order to equip the VSWT with LFC capability to support the grid during sudden variation in generation or load...... regulation. The proposed scheme demonstrates remarkable improvement transient state of both voltage and frequency profiles in comparison with conventional LFC designs provided by Central Power Plants (CPP) or Wind Power Plants (WPP). Numerical simulations carried out in DigSilent Power- Factory confirm...

Gaussian vs non-Gaussian turbulence: impact on wind turbine loads

DEFF Research Database (Denmark)

Berg, Jacob; Natarajan, Anand; Mann, Jakob

2016-01-01

taking into account the safety factor for extreme moments. Other extreme load moments as well as the fatigue loads are not affected because of the use of non-Gaussian turbulent inflow. It is suggested that the turbine thus acts like a low-pass filter that averages out the non-Gaussian behaviour, which......From large-eddy simulations of atmospheric turbulence, a representation of Gaussian turbulence is constructed by randomizing the phases of the individual modes of variability. Time series of Gaussian turbulence are constructed and compared with its non-Gaussian counterpart. Time series from the two...

On the Use of Coupled Wind, Wave, and Current Fields in the Simulation of Loads on Bottom-Supported Offshore Wind Turbines during Hurricanes: March 2012 - September 2015

Energy Technology Data Exchange (ETDEWEB)

Kim, Eungsoo [Univ. of Texas, Austin, TX (United States); Manuel, Lance [Univ. of Texas, Austin, TX (United States); Curcic, Milan [Univ. of Miami, Coral Gables, FL (United States); Chen, Shuyi S. [Univ. of Miami, Coral Gables, FL (United States); Phillips, Caleb [National Renewable Energy Lab. (NREL), Golden, CO (United States); Veers, Paul [National Renewable Energy Lab. (NREL), Golden, CO (United States)

2016-06-01

In the United States, potential offshore wind plant sites have been identified along the Atlantic seaboard and in the Gulf of Mexico. It is imperative that we define external conditions associated with hurricanes and severe winter storms and consider load cases for which wind turbines may need to be designed. We selected two hurricanes, Ike (2008) and Sandy (2012), and investigated the effect these tropical storms would have on bottom-supported offshore wind turbines that were hypothetically in or close to their path as they made landfall. For realistic turbine loads assessment, it is important that the coupled influences of the changing wind, wave, and current fields are simulated throughout the evolution of the hurricanes. We employed a coupled model--specifically, the University of Miami Coupled Model (UMCM)--that integrates atmospheric, wave, and ocean components to produce needed wind, wave, and current data. The wind data are used to generate appropriate vertical wind profiles and full wind velocity fields including turbulence; the current field over the water column is obtained by interpolated discrete output current data; and short-crested irregular second-order waves are simulated using output directional wave spectra from the coupled model. We studied two monopile-supported offshore wind turbines sited in 20 meters of water in the Gulf of Mexico to estimate loads during Hurricane Ike, and a jacket space-frame platform-supported offshore wind turbine sited in 50 meters of water in the mid-Atlantic region to estimate loads during Hurricane Sandy. In this report we discuss in detail how the simulated hurricane wind, wave, and current output data are used in turbine loads studies. In addition, important characteristics of the external conditions are studied, including the relative importance of swell versus wind seas, aerodynamic versus hydrodynamic forces, current velocity effects, yaw control options for the turbine, hydrodynamic drag versus inertia forces

Calculation of wind turbine aeroelastic behaviour. The Garrad Hassan approach

Energy Technology Data Exchange (ETDEWEB)

Quarton, D C [Garrad Hassan and Partners Ltd., Bristol (United Kingdom)

1996-09-01

The Garrad Hassan approach to the prediction of wind turbine loading and response has been developed over the last decade. The goal of this development has been to produce calculation methods that contain realistic representation of the wind, include sensible aerodynamic and dynamic models of the turbine and can be used to predict fatigue and extreme loads for design purposes. The Garrad Hassan calculation method is based on a suite of four key computer programs: WIND3D for generation of the turbulent wind field; EIGEN for modal analysis of the rotor and support structure; BLADED for time domain calculation of the structural loads; and SIGNAL for post-processing of the BLADED predictions. The interaction of these computer programs is illustrated. A description of the main elements of the calculation method will be presented. (au)

Real-time POD-CFD Wind-Load Calculator for PV Systems

Energy Technology Data Exchange (ETDEWEB)

Huayamave, Victor [Centecorp; Divo, Eduardo [Centecorp; Ceballos, Andres [Centecorp; Barriento, Carolina [Centecorp; Stephen, Barkaszi [FSEC; Hubert, Seigneur [FSEC

2014-03-21

The primary objective of this project is to create an accurate web-based real-time wind-load calculator. This is of paramount importance for (1) the rapid and accurate assessments of the uplift and downforce loads on a PV mounting system, (2) identifying viable solutions from available mounting systems, and therefore helping reduce the cost of mounting hardware and installation. Wind loading calculations for structures are currently performed according to the American Society of Civil Engineers/ Structural Engineering Institute Standard ASCE/SEI 7; the values in this standard were calculated from simplified models that do not necessarily take into account relevant characteristics such as those from full 3D effects, end effects, turbulence generation and dissipation, as well as minor effects derived from shear forces on installation brackets and other accessories. This standard does not include provisions that address the special requirements of rooftop PV systems, and attempts to apply this standard may lead to significant design errors as wind loads are incorrectly estimated. Therefore, an accurate calculator would be of paramount importance for the preliminary assessments of the uplift and downforce loads on a PV mounting system, identifying viable solutions from available mounting systems, and therefore helping reduce the cost of the mounting system and installation. The challenge is that although a full-fledged three-dimensional computational fluid dynamics (CFD) analysis would properly and accurately capture the complete physical effects of air flow over PV systems, it would be impractical for this tool, which is intended to be a real-time web-based calculator. CFD routinely requires enormous computation times to arrive at solutions that can be deemed accurate and grid-independent even in powerful and massively parallel computer platforms. This work is expected not only to accelerate solar deployment nationwide, but also help reach the SunShot Initiative goals

Extreme winds in Denmark

DEFF Research Database (Denmark)

Kristensen, L.; Rathmann, Ole; Hansen, S.O.

1999-01-01

Wind-speed data from four sites in Denmark have been analyzed in order to obtain estimates of the basic wind velocity which is defined as the 50-year wind speed under standard conditions, i.e. ten-minute averages at the height 10 m over a uniform terrainwith the roughness length 0.05 m. The sites...... by means of the geostrophic drag law for neutral stratification. The basic wind velocity in 30o sectors are obtainedthrough ranking of the largest values of the ¤friction velocity pressure¤ 1/2 ¤#rho#¤¤u¤"2_x taken both once every two months and once every year. The main conclusion is that the basic wind...

Extreme load alleviation using industrial implementation of active trailing edge flaps in a full design load basis

DEFF Research Database (Denmark)

Barlas, Athanasios; Pettas, Vasilis; Gertz, Drew Patrick

2016-01-01

The application of active trailing edge flaps in an industrial oriented implementation is evaluated in terms of capability of alleviating design extreme loads. A flap system with basic control functionality is implemented and tested in a realistic full Design Load Basis (DLB) for the DTU 10MW...

Linear active disturbance rejection-based load frequency control concerning high penetration of wind energy

International Nuclear Information System (INIS)

Tang, Yanmei; Bai, Yan; Huang, Congzhi; Du, Bin

2015-01-01

Highlights: • A disturbance rejection solution to the load frequency control issue is proposed. • Several power systems with wind energy conversation system have been tested. • A tuning algorithm of the controller parameters was proposed. • The performance of the proposed approach is better than traditional controllers. - Abstract: A new grid load frequency control approach is proposed for the doubly fed induction generator based wind power plants. The load frequency control issue in a power system is undergoing fundamental changes due to the rapidly growing amount of wind energy conversation system, and concentrating on maintaining generation-load balance and disturbance rejection. The prominent feature of the linear active disturbance rejection control approach is that the total disturbance can be estimated and then eliminated in real time. And thus, it is a feasible solution to deal with the load frequency control issue. In this paper, the application of the linear active disturbance rejection control approach in the load frequency control issue for a complex power system with wind energy conversation system based on doubly fed induction generator is investigated. The load frequency control issue is formulated as a decentralized multi-objective optimization control problem, the solution to which is solved by the hybrid particle swarm optimization technique. To show the effectiveness of the proposed control scheme, the robust performance testing based on Monte-Carlo approach is carried out. The performance superiority of the system with the proposed linear active disturbance rejection control approach over that with the traditional proportional integral and fuzzy-proportional integral-based controllers is validated by the simulation results

On Advanced Control Methods toward Power Capture and Load Mitigation in Wind Turbines

Institute of Scientific and Technical Information of China (English)

Yuan Yuan; Jiong Tang

2017-01-01

This article provides a survey of recently emerged methods for wind turbine control.Multivariate control approaches to the optimization of power capture and the reduction of loads in components under time-varying turbulent wind fields have been under extensive investigation in recent years.We divide the related research activities into three categories:modeling and dynamics of wind turbines,active control of wind turbines,and passive control of wind turbines.Regarding turbine dynamics,we discuss the physical fundamentals and present the aeroelastic analysis tools.Regarding active control,we review pitch control,torque control,and yaw control strategies encompassing mathematical formulations as well as their applications toward different objectives.Our survey mostly focuses on blade pitch control,which is considered one of the key elements in facilitating load reduction while maintaining power capture performance.Regarding passive control,we review techniques such as tuned mass dampers,smart rotors,and microtabs.Possible future directions are suggested.

Determining the impact of wind on system costs via the temporal patterns of load and wind generation

International Nuclear Information System (INIS)

Davis, Clay D.; Gotham, Douglas J.; Preckel, Paul V.; Liu, Andrew L.

2013-01-01

Ambitious targets have been set for expanding electricity generation from renewable sources, including wind. Expanding wind power impacts needs for other electricity generating resources. As states plan for increasing levels of wind generation in their portfolio of generation resources it is important to consider how this intermittent resource impacts the need for other generation resources. A case study for Indiana estimates the value of wind capacity and demonstrates how to optimize its level and the levels of other generation resources. Changes are driven by temporal patterns of wind power output and load. System wide impacts are calculated for energy, capacity, and costs under multiple wind expansion scenarios which highlight the geographic characteristics of a systems portfolio of wind generation. The impacts of carbon prices, as proposed in the Bingaman Bill, are considered. Finally, calculations showing the effect increasing levels of wind generation will have on end use Indiana retail rates are included. - Highlights: • We estimate the value of wind capacity. • We determine wind generation's impact on the optimal mix of non-wind generation. • Optimal levels of wind and non-wind generation are determined. • We consider the impact of a carbon price on the optimal mix of resources. • The impact of additional wind capacity on Indiana residential rates is calculated

Thermal Loading and Reliability of 10 MW Multilevel Wind Power Converter at Different Wind Roughness Classes

DEFF Research Database (Denmark)

Isidori, Andrea; Rossi, Fabio Mario; Blaabjerg, Frede

2014-01-01

This paper focuses on the design, thermal loading, and reliability of a three-level neutral-point-clamped back-to-back full-scale converter for a 10-MW direct-drive wind turbine equipped with a permanent-magnet synchronous generator. The reliability performance of the three-level converter...... is strongly influenced by the thermal behavior of the semiconductor devices and their mission profile which directly affects the lifetime and the cost of the entire converter. Therefore, a simulation platform is developed in a Matlab/Simulink and PLECS simulation environment to analyze the dynamics...... of the system using different kinds of modulation strategies and analyzing the different wind-load conditions that are dependent on roughness classes. This paper shows that the 60 ° discontinuous pulsewidth-modulation strategies allow better thermal performance and increase the estimated lifetime...

Thermal loading and reliability of 10 MW multilevel wind power converter at different wind roughness classes

DEFF Research Database (Denmark)

Isidori, Andrea; Rossi, Fabio Mario; Blaabjerg, Frede

2012-01-01

This paper focuses on the design, thermal loading and reliability of a three-level Neutral Point Clamped (3-L NPC) back-to-back full scale converter for a 10 MW direct-drive wind turbine equipped with a Permanent Magnet Synchronous Generator (PMSG). The reliability performance of the three......-level converter is strongly influenced by the thermal behaviour of the semiconductor devices and their mission profile which directly affects the lifetime and the cost of the whole converter. Therefore, the simulation platform is developed in Matlab/Simulink and PLECS simulation environment to analyse...... the dynamics of the system using different kinds of modulation strategies and analyzing different wind load conditions dependent on roughness classes. It is concluded that 60° discontinuous PWM modulation strategies show better thermal performance and increase the estimated lifetime of the converter...

Effect of blade flutter and electrical loading on small wind turbine noise

Science.gov (United States)

The effect of blade flutter and electrical loading on the noise level of two different size wind turbines was investigated at the Conservation and Production Research Laboratory (CPRL) near Bushland, TX. Noise and performance data were collected on two blade designs tested on a wind turbine rated a...

On long-term fatigue damage and reliability analysis of gears under wind loads in offshore wind turbine drivetrains

OpenAIRE

Rasekhi Nejad, Amir; Gao, Zhen; Moan, Torgeir

2014-01-01

In this paper, a long-term fatigue damage analysis method for gear tooth root bending in wind turbine’s drivetrains is presented. The proposed method is established based on the ISO gear design codes which are basically developed for gears in general applications, not specifically for wind turbine gears. The ISO procedure is adapted and further improved to include the long-term fatigue damage of wind turbine’s gears. The load duration distribution (LDD) method is used to obtain the short-term...

Stochastic model for joint wave and wind loads on offshore structures

DEFF Research Database (Denmark)

Ditlevsen, Ove Dalager

2002-01-01

_s,T_z)$ from the North Sea a well fitting joint distribution of $(H_s,T_z)$ is obtained as a so-called Nataf model. Since the wave field is wind driven, there is a correlation between the time averaged wind velocity pressure $Q$ and the characteristic wave height in the stationary situation. Using the Poisson...... process model to concentrate on those load events that are of importance for the evaluation of the safety of the structure, that is, events with $Q$ larger than some threshold $q_0$, available information about the wind velocity pressure distributionin high wind situations can be used to formulate a Nataf...

Small-Signal Stability Analysis of Full-Load Converter Interfaced Wind Turbines

DEFF Research Database (Denmark)

Knüppel, Thyge; Akhmatov, Vladislav; Nielsen, Jørgen Nygård

2009-01-01

focus since the share of wind power increases substituting power generation from conventional power plants. Here, a study based on modal analysis is presented which investigate the effect of large scale integration of full-load converter interfaced wind turbines on inter-area oscillations in a three...... generator network. A detailed aggregated wind turbine model is employed which includes all necessary control functions. It is shown that the wind urbines have very low participation in the inter-area power oscillation.......Power system stability investigations of wind farms often cover the tasks of low-voltage-fault-ride-through, voltage and reactive power control, and power balancing, but not much attention has yet been paid to the task of small-signal stability. Small-signal stability analysis needs increasing...

Directionality Effects of Aligned Wind and Wave Loads on a Y-Shape Semi-Submersible Floating Wind Turbine under Rated Operational Conditions

Directory of Open Access Journals (Sweden)

Shengtao Zhou

2017-12-01

Full Text Available The Y-shape (triangular semi-submersible foundation has been adopted by most of the built full-scale floating wind turbines, such as Windfloat, Fukushima Mirai and Shimpuu. Considering the non-fully-symmetrical shape and met-ocean condition, the foundation laying angle relative to wind/wave directions will not only influence the downtime and power efficiency of the floating turbine, but also the strength and fatigue safety of the whole structure. However, the dynamic responses induced by various aligned wind and wave load directions have scarcely been investigated comparatively before. In our study, the directionality effects are investigated by means of combined wind and wave tests and coupled multi-body simulations. By comparing the measured data in three load directions, it is found that the differences of platform motions are mainly derived from the wave loads and larger pitch motion can always be observed in one of the directions. To make certain the mechanism underlying the observed phenomena, a coupled multi-body dynamic model of the floating wind turbine is established and validated. The numerical results demonstrate that the second-order hydrodynamic forces contribute greatly to the directionality distinctions for surge and pitch, and the first-order hydrodynamic forces determine the variations of tower base bending moments and nacelle accelerations. These findings indicate the directionality effects should be predetermined comprehensively before installation at sea, which is important for the operation and maintenance of the Y-shape floating wind turbines.

A Floating Offshore Wind Turbine in Extreme Wave Conditions

DEFF Research Database (Denmark)

Wehmeyer, Christof

is an expected maximum wave in accordance with a Rayleigh distribution. The maximum waves are numerically represented by embedded Stream-function waves. The author compares the resulting bow tendon loading of the hybrid model to the measured responses, as a key performance indicator. 90% to 95% of the loads show...... a satisfying match, though the hybrid model over predicts the remaining 5% to 10% maximum loads by 32%, 34% and 29% for a linear irregular sea state, a nonlinear irregular sea state and a nonlinear irregular sea state with an embedded Stream-function wave, respectively. The limited number of sea states during...... important aspects, which make them non-conservative in use for FOWT: (A) The offshore wind industry intends to install floating structures at much lower water depth (from 50m onwards), than the offshore oil & gas industry (from 300m onwards). In such cases a linear wave theory approach might...

Proportional resonant individual pitch control for mitigation of wind turbines loads

DEFF Research Database (Denmark)

Zhang, Yunqian; Chen, Zhe; Cheng, Ming

2013-01-01

attenuation. The individual pitch control (IPC) is a promising way to reduce the wind turbine loads. This study presents a proportional resonant (PR) IPC, which does not need the measurement of blade azimuth angle and multiple complex Coleman transformations between rotational coordinate frame and stationary...... coordinate frame. The new strategy can attenuate the 1p and higher harmonics on the wind turbine blades as well as 3p on the hub without any filters. The wind turbine code fatigue, aerodynamics, structures and turbulence is applied to a doubly fed induction generator-based wind power generation system....... The simulations are performed on the National Renewable Energy Laboratory 1.5 MW upwind reference wind turbine model. The simulation results are presented and discussed to demonstrate the capability and effectiveness of the proposed PR IPC method....

Wind Turbine Pitch Control and Load Mitigation Using an L1 Adaptive Approach

Directory of Open Access Journals (Sweden)

Danyong Li

2014-01-01

Full Text Available We present an application of L1 adaptive output feedback control design to wind turbine collective pitch control and load mitigation. Our main objective is the design of an L1 output feedback controller without wind speed estimation, ensuring that the generator speed tracks the reference trajectory with robustness to uncertain parameters and time-varying disturbances (mainly the uniform wind disturbance across the wind turbine rotor. The wind turbine model CART (controls advanced research turbine developed by the national renewable energy laboratory (NREL is used to validate the performance of the proposed L1 adaptive controller using the FAST (fatigue, aerodynamics, structures, and turbulence code. A comparative study is also conducted between the proposed controller and the most popular methods in practice: gain scheduling PI (GSPI controls and disturbance accommodating control (DAC methods. The results show better performance of L1 output feedback controller over the other two methods. Moreover, based on the FAST software and LQR analysis in the reference model selection of L1 adaptive controller, tradeoff can be achieved between control performance and loads mitigation.

Energy researchers - 8. Wind power production: Wind power, the energy of the future; A mature sector; The ecological attraction of wind

International Nuclear Information System (INIS)

Minster, Jean-Francois; Appert, Olivier; Moisan, Francois; Salha, Bernard; Tardieu, Bernard; Florette, Marc; Ghidaglia, Jean-Michel; Viterbo, Jerome

2012-01-01

A first article comments the development in the design of wind turbines which become more powerful, with higher performance. Researchers are also working on blade shape, on alternator technology, on the use of multiplier to enable the reduction of the alternator weight, on better control and command systems to increase the load factor. The development of offshore wind farms is also a challenge in terms of maintenance, in wind turbine design in order to withstand sea corrosion, and in terms of connection to the grid. A second article comments the evolution of the wind energy sector in terms of installed capacity, costs and competitiveness. In an interview, three researchers outline the extremely positive carbon footprint and other benefits of wind power, and also discuss its disadvantages: they mainly concern the impact on landscape, but also birds and marine fauna

A Compendium of Wind Statistics and Models for the NASA Space Shuttle and Other Aerospace Vehicle Programs

Science.gov (United States)

Smith, O. E.; Adelfang, S. I.

1998-01-01

The wind profile with all of its variations with respect to altitude has been, is now, and will continue to be important for aerospace vehicle design and operations. Wind profile databases and models are used for the vehicle ascent flight design for structural wind loading, flight control systems, performance analysis, and launch operations. This report presents the evolution of wind statistics and wind models from the empirical scalar wind profile model established for the Saturn Program through the development of the vector wind profile model used for the Space Shuttle design to the variations of this wind modeling concept for the X-33 program. Because wind is a vector quantity, the vector wind models use the rigorous mathematical probability properties of the multivariate normal probability distribution. When the vehicle ascent steering commands (ascent guidance) are wind biased to the wind profile measured on the day-of-launch, ascent structural wind loads are reduced and launch probability is increased. This wind load alleviation technique is recommended in the initial phase of vehicle development. The vehicle must fly through the largest load allowable versus altitude to achieve its mission. The Gumbel extreme value probability distribution is used to obtain the probability of exceeding (or not exceeding) the load allowable. The time conditional probability function is derived from the Gumbel bivariate extreme value distribution. This time conditional function is used for calculation of wind loads persistence increments using 3.5-hour Jimsphere wind pairs. These increments are used to protect the commit-to-launch decision. Other topics presented include the Shuttle Shuttle load-response to smoothed wind profiles, a new gust model, and advancements in wind profile measuring systems. From the lessons learned and knowledge gained from past vehicle programs, the development of future launch vehicles can be accelerated. However, new vehicle programs by their very

Unbalanced voltage faults: the impact on structural loads of doubly fed asynchronous generator wind turbines

DEFF Research Database (Denmark)

Barahona Garzón, Braulio; Cutululis, Nicolaos Antonio; Hansen, Anca Daniela

2014-01-01

This paper investigates the impact that unbalanced voltage faults have on wind turbine structural loads. In such cases, electromagnetic torque oscillations occur at two times the supply voltage frequency. The objectives of this work are to quantify wind turbine structural loads induced...... by unbalanced voltage faults relative to those during normal operation; and to evaluate the potential for reducing structural loads with the control of the generator. The method applied is integrated dynamic analysis. Namely, dynamic analysis with models that consider the most important aeroelastic, electrical...

Model-Based Load Estimation for Predictive Condition Monitoring of Wind Turbines

DEFF Research Database (Denmark)

Perisic, Nevena; Pederen, Bo Juul; Grunnet, Jacob Deleuran

signal is performed online, and a Load Indicator Signal (LIS) is formulated as a ratio between current estimated accumulated fatigue loads and its expected value based only on a priori knowledge (WTG dynamics and wind climate). LOT initialisation is based on a priori knowledge and can be obtained using...... programme for pre-maintenance actions. The performance of LOT is demonstrated by applying it to one of the most critical WTG components, the gearbox. Model-based load CMS for gearbox requires only standard WTG SCADA data. Direct measuring of gearbox fatigue loads requires high cost and low reliability...... measurement equipment. Thus, LOT can significantly reduce the price of load monitoring....

Probabilistic Constrained Load Flow Considering Integration of Wind Power Generation and Electric Vehicles

DEFF Research Database (Denmark)

Vlachogiannis, Ioannis (John)

2009-01-01

A new formulation and solution of probabilistic constrained load flow (PCLF) problem suitable for modern power systems with wind power generation and electric vehicles (EV) demand or supply is represented. The developed stochastic model of EV demand/supply and the wind power generation model...... are incorporated into load flow studies. In the resulted PCLF formulation, discrete and continuous control parameters are engaged. Therefore, a hybrid learning automata system (HLAS) is developed to find the optimal offline control settings over a whole planning period of power system. The process of HLAS...

Short-term load and wind power forecasting using neural network-based prediction intervals.

Science.gov (United States)

Quan, Hao; Srinivasan, Dipti; Khosravi, Abbas

2014-02-01

Electrical power systems are evolving from today's centralized bulk systems to more decentralized systems. Penetrations of renewable energies, such as wind and solar power, significantly increase the level of uncertainty in power systems. Accurate load forecasting becomes more complex, yet more important for management of power systems. Traditional methods for generating point forecasts of load demands cannot properly handle uncertainties in system operations. To quantify potential uncertainties associated with forecasts, this paper implements a neural network (NN)-based method for the construction of prediction intervals (PIs). A newly introduced method, called lower upper bound estimation (LUBE), is applied and extended to develop PIs using NN models. A new problem formulation is proposed, which translates the primary multiobjective problem into a constrained single-objective problem. Compared with the cost function, this new formulation is closer to the primary problem and has fewer parameters. Particle swarm optimization (PSO) integrated with the mutation operator is used to solve the problem. Electrical demands from Singapore and New South Wales (Australia), as well as wind power generation from Capital Wind Farm, are used to validate the PSO-based LUBE method. Comparative results show that the proposed method can construct higher quality PIs for load and wind power generation forecasts in a short time.

Yawing characteristics during slippage of the nacelle of a multi MW wind turbine

Science.gov (United States)

Kim, M.-G.; Dalhoff, P. H.; Gust, P.

2016-09-01

High aerodynamic yaw loads coupled with electrical failures in the wind turbine can result to a slippage of the nacelle, due to limited braking capabilities of the yaw system. A slippage on the other hand can lead to a mechanical malfunction of the yaw system. To analyse the yawing characteristics of a wind turbine during nacelle slippage situations, a detailed multibody system model of the yaw system has been developed and incorporated in a multibody system model of a wind turbine based on a 3.3 MW turbine. Extreme load cases which lead to a nacelle slippage have been simulated. The dynamics and loads on different wind turbine components are presented and discussed. First results show minimal load increases of the rotor torque and the bending moments of the blade root sections during slippage but unfavourable rotational speeds of the yaw drives.

Optimum Parameters of a Tuned Liquid Column Damper in a Wind Turbine Subject to Stochastic Load

Science.gov (United States)

Alkmim, M. H.; de Morais, M. V. G.; Fabro, A. T.

2017-12-01

Parameter optimization for tuned liquid column dampers (TLCD), a class of passive structural control, have been previously proposed in the literature for reducing vibration in wind turbines, and several other applications. However, most of the available work consider the wind excitation as either a deterministic harmonic load or random load with white noise spectra. In this paper, a global direct search optimization algorithm to reduce vibration of a tuned liquid column damper (TLCD), a class of passive structural control device, is presented. The objective is to find optimized parameters for the TLCD under stochastic load from different wind power spectral density. A verification is made considering the analytical solution of undamped primary system under white noise excitation by comparing with result from the literature. Finally, it is shown that different wind profiles can significantly affect the optimum TLCD parameters.

Voltage control of a variable speed wind turbine connected to an isolated load: Experimental study

International Nuclear Information System (INIS)

Masmoudi, Abdelkarim; Krichen, Lotfi; Ouali, Abderrazak

2012-01-01

Highlights: ► We develop an experimental test bench of a wind energy conversion system. ► A DC motor is emulating a variable speed wind turbine using a DS1104 card. ► The production unit is supplying a three-phase load. ► A voltage control is established in order to regulate the DC bus voltage and the line-to-line voltages. - Abstract: This study is interested in the development of an experimental test bench of an autonomous wind energy conversion system (WECS) based on a permanent magnet synchronous generator (PMSG). After the description of the test bench, the elements constituting the WECS are presented. Then, a real time model implemented under a digital signal processor (DSP) system is established. The first objective of this work is to validate the functionality of the test bench leading to experiment some principles developed in theory. The second objective is to control the load connection voltages and the DC bus voltage. For the first control, two resonant controllers are used and for the second one, a dump load, connected to the DC bus, offers the possibility to maintain a balance between production and consumption in spite of wind fluctuations and load variations. The experimental results show the effectiveness of the test bench trying out in real time the behavior of a WECS supplying an isolated load.

Reliability assessment of Wind turbines

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard

2015-01-01

Wind turbines can be considered as structures that are in between civil engineering structures and machines since they consist of structural components and many electrical and machine components together with a control system. Further, a wind turbine is not a one-of-a-kind structure...... but manufactured in series production based on many component tests, some prototype tests and zeroseries wind turbines. These characteristics influence the reliability assessment where focus in this paper is on the structural components. Levelized Cost Of Energy is very important for wind energy, especially when...... comparing to other energy sources. Therefore much focus is on cost reductions and improved reliability both for offshore and onshore wind turbines. The wind turbine components should be designed to have sufficient reliability level with respect to both extreme and fatigue loads but also not be too costly...

Modeling of quasi-static thrust load of wind turbines based on 1 s SCADA data

Directory of Open Access Journals (Sweden)

N. Noppe

2018-03-01

Full Text Available A reliable load history is crucial for a fatigue assessment of wind turbines. However, installing strain sensors on every wind turbine is not economically feasible. In this paper, a technique is proposed to reconstruct the thrust load history of a wind turbine based on high-frequency Supervisory Control and Data Acquisition (SCADA data. Strain measurements recorded during a short period of time are used to train a neural network. The selection of appropriate input parameters is performed based on Pearson correlation and mutual information. Once the training is done, the model can be used to predict the thrust load based on SCADA data only. The technique is validated on two different datasets, one consisting of simulation data (using the software FAST v8, created by Jonkman and Jonkman, 2016 obtained in a controllable environment and one consisting of measurements taken at an offshore wind turbine. In general, the relative error between simulated or measured and predicted thrust load barely exceeds 15 % during normal operation.

Optimized Control Strategy For Over Loaded Offshore Wind Turbines

DEFF Research Database (Denmark)

Odgaard, Peter Fogh; Knudsen, Torben; Wisniewski, Rafal

2015-01-01

controller tuning for a given wind turbine. It also enables a very safe and robust comparison between a new control strategy and the present one. Main body of abstract Is it true that power de-rating indeed the best way to reduce loads? The power de-rating approach has the drawback of only indirectly...

Decoupled simulations of offshore wind turbines with reduced rotor loads and aerodynamic damping

Directory of Open Access Journals (Sweden)

S. Schafhirt

2018-02-01

Full Text Available Decoupled load simulations are a computationally efficient method to perform a dynamic analysis of an offshore wind turbine. Modelling the dynamic interactions between rotor and support structure, especially the damping caused by the rotating rotor, is of importance, since it influences the structural response significantly and has a major impact on estimating fatigue lifetime. Linear damping is usually used for this purpose, but experimentally and analytically derived formulas to calculate an aerodynamic damping ratio often show discrepancies to measurement and simulation data. In this study decoupled simulation methods with reduced and full rotor loads are compared to an integrated simulation. The accuracy of decoupled methods is evaluated and an optimization is performed to obtain aerodynamic damping ratios for different wind speeds that provide the best results with respect to variance and equivalent fatigue loads at distinct output locations. Results show that aerodynamic damping is not linear, but it is possible to match desired output using decoupled models. Moreover, damping ratios obtained from the empirical study suggest that aerodynamic damping increases for higher wind speeds.

Application of two passive strategies on the load mitigation of large offshore wind turbines

Science.gov (United States)

Shirzadeh, Rasoul; Kühn, Martin

2016-09-01

This study presents the numerical results of two passive strategies to reduce the support structure loads of a large offshore wind turbine. In the first approach, an omnidirectional tuned mass damper is designed and implemented in the tower top to alleviate the structural vibrations. In the second approach, a viscous fluid damper model which is diagonally attached to the tower at two points is developed. Aeroelastic simulations are performed for the offshore 10MW INNWIND.EU reference wind turbine mounted on a jacket structure. Lifetime damage equivalent loads are evaluated at the tower base and compared with those for the reference wind turbine. The results show that the integrated design can extend the lifetime of the support structure.

Wave induced extreme hull girder loads on containerships

DEFF Research Database (Denmark)

Jensen, Jørgen Juncher; Pedersen, Preben Terndrup; Shi, Bill

2009-01-01

This paper provides simple but rational procedures for prediction of extreme wave – induced sectional hull girder forces with reasonable engineering accuracy. The procedures take into account main ship hull characteristics such as: length, breadth, draught, block coefficient, bow flare coefficient......, forward speed and hull flexibility. The vertical hull girder loads are evaluated for specific operational profiles. Firstly a quadratic strip theory is presented which can give separate predictions for the hogging and sagging bending moments and shear forces and for hull girder loads. Then this procedure...... is based on rational methods it can be applied for novel single hull ship types not presently covered by the rules of the classification societies or to account for specific operational profiles....

Wind loads on stand-off photovoltaic systems on pitched roofs

NARCIS (Netherlands)

Geurts, C.P.W.; Blackmore, P.A.

2013-01-01

Stand-off photovoltaic systems are a popular measure for retrofitting of existing pitched roofs. Panels are generally mounted parallel to the existing roof coverings, usually roofing tiles. Full scale and wind tunnel experiments have been performed to determine the net uplift loads on these systems,

Ultimate design load analysis of planetary gearbox bearings under extreme events

DEFF Research Database (Denmark)

Gallego Calderon, Juan Felipe; Natarajan, Anand; Cutululis, Nicolaos Antonio

2017-01-01

This paper investigates the impact of extreme events on the planet bearings of a 5 MW gearbox. The system is simulated using an aeroelastic tool, where the turbine structure is modeled, and MATLAB/Simulink, where the drivetrain (gearbox and generator) are modeled using a lumped-parameter approach....... Three extreme events are assessed: low-voltage ride through, emergency stop and normal stop. The analysis is focused on finding which event has the most negative impact on the bearing extreme radial loads. The two latter events are carried out following the guidelines of the International...

Analysis of Damage in Laminated Architectural Glazing Subjected to Wind Loading and Windborne Debris Impact

Directory of Open Access Journals (Sweden)

Daniel S. Stutts

2013-05-01

Full Text Available Wind loading and windborne debris (missile impact are the two primary mechanisms that result in window glazing damage during hurricanes. Wind-borne debris is categorized into two types: small hard missiles; such as roof gravel; and large soft missiles representing lumber from wood-framed buildings. Laminated architectural glazing (LAG may be used in buildings where impact resistance is needed. The glass plies in LAG undergo internal damage before total failure. The bulk of the published work on this topic either deals with the stress and dynamic analyses of undamaged LAG or the total failure of LAG. The pre-failure damage response of LAG due to the combination of wind loading and windborne debris impact is studied. A continuum damage mechanics (CDM based constitutive model is developed and implemented via an axisymmetric finite element code to study the failure and damage behavior of laminated architectural glazing subjected to combined loading of wind and windborne debris impact. The effect of geometric and material properties on the damage pattern is studied parametrically.

Observations of Building Performance under Combined Wind and Surge Loading from Hurricane Harvey

Science.gov (United States)

Lombardo, F.; Roueche, D. B.; Krupar, R. J.; Smith, D. J.; Soto, M. G.

2017-12-01

Hurricane Harvey struck the Texas coastline on August 25, 2017, as a Category 4 hurricane - the first major hurricane to reach the US in twelve years. Wind gusts over 130 mph and storm surge as high as 12.5 ft caused widespread damage to buildings and critical infrastructure in coastal communities including Rockport, Fulton, Port Aransas and Aransas Pass. This study presents the methodology and preliminary observations of a coordinated response effort to document residential building performance under wind and storm surge loading. Over a twelve day survey period the study team assessed the performance of more than 1,000 individual, geo-located residential buildings. Assessments were logged via a smartphone application to facilitate rapid collection and collation of geotagged photographs, building attributes and structural details, and structural damage observations. Detailed assessments were also made of hazard intensity, specifically storm surge heights and both wind speed and direction indicators. Preliminary observations and findings will be presented, showing strong gradients in damage between inland and coastal regions of the affected areas that may be due in part to enhanced individual loading effects of wind and storm surge and potentially joint-hazard loading effects. Contributing factors to the many cases of disproportionate damage observed in close proximity will also be discussed. Ongoing efforts to relate building damage to near-surface hazard measurements (e.g., radar, anemometry) in close proximity will also be described.

Short-Term Forecasting of Loads and Wind Power for Latvian Power System: Accuracy and Capacity of the Developed Tools

Directory of Open Access Journals (Sweden)

Radziukynas V.

2016-04-01

Full Text Available The paper analyses the performance results of the recently developed short-term forecasting suit for the Latvian power system. The system load and wind power are forecasted using ANN and ARIMA models, respectively, and the forecasting accuracy is evaluated in terms of errors, mean absolute errors and mean absolute percentage errors. The investigation of influence of additional input variables on load forecasting errors is performed. The interplay of hourly loads and wind power forecasting errors is also evaluated for the Latvian power system with historical loads (the year 2011 and planned wind power capacities (the year 2023.

Short-Term Forecasting of Loads and Wind Power for Latvian Power System: Accuracy and Capacity of the Developed Tools

Science.gov (United States)

Radziukynas, V.; Klementavičius, A.

2016-04-01

The paper analyses the performance results of the recently developed short-term forecasting suit for the Latvian power system. The system load and wind power are forecasted using ANN and ARIMA models, respectively, and the forecasting accuracy is evaluated in terms of errors, mean absolute errors and mean absolute percentage errors. The investigation of influence of additional input variables on load forecasting errors is performed. The interplay of hourly loads and wind power forecasting errors is also evaluated for the Latvian power system with historical loads (the year 2011) and planned wind power capacities (the year 2023).

Influence of turbulence, orientation, and site configuration on the response of buildings to extreme wind.

Science.gov (United States)

Aly, Aly Mousaad

2014-01-01

Atmospheric turbulence results from the vertical movement of air, together with flow disturbances around surface obstacles which make low- and moderate-level winds extremely irregular. Recent advancements in wind engineering have led to the construction of new facilities for testing residential homes at relatively high Reynolds numbers. However, the generation of a fully developed turbulence in these facilities is challenging. The author proposed techniques for the testing of residential buildings and architectural features in flows that lack fully developed turbulence. While these methods are effective for small structures, the extension of the approach for large and flexible structures is not possible yet. The purpose of this study is to investigate the role of turbulence in the response of tall buildings to extreme winds. In addition, the paper presents a detailed analysis to investigate the influence of upstream terrain conditions, wind direction angle (orientation), and the interference effect from the surrounding on the response of high-rise buildings. The methodology presented can be followed to help decision makers to choose among innovative solutions like aerodynamic mitigation, structural member size adjustment, and/or damping enhancement, with an objective to improve the resiliency and the serviceability of buildings.

Influence of Turbulence, Orientation, and Site Configuration on the Response of Buildings to Extreme Wind

Science.gov (United States)

2014-01-01

Atmospheric turbulence results from the vertical movement of air, together with flow disturbances around surface obstacles which make low- and moderate-level winds extremely irregular. Recent advancements in wind engineering have led to the construction of new facilities for testing residential homes at relatively high Reynolds numbers. However, the generation of a fully developed turbulence in these facilities is challenging. The author proposed techniques for the testing of residential buildings and architectural features in flows that lack fully developed turbulence. While these methods are effective for small structures, the extension of the approach for large and flexible structures is not possible yet. The purpose of this study is to investigate the role of turbulence in the response of tall buildings to extreme winds. In addition, the paper presents a detailed analysis to investigate the influence of upstream terrain conditions, wind direction angle (orientation), and the interference effect from the surrounding on the response of high-rise buildings. The methodology presented can be followed to help decision makers to choose among innovative solutions like aerodynamic mitigation, structural member size adjustment, and/or damping enhancement, with an objective to improve the resiliency and the serviceability of buildings. PMID:24701140

Application of Load Carrying Sandwich Elements in Wind Turbine Blades

DEFF Research Database (Denmark)

Jensen, Jacob Fisker; Schultz, Jacob Pagh; Berggreen, Carl Christian

2005-01-01

The present work investigates the possibilities and drawbacks when applying sandwich as opposed to single skin composites in the flanges of the load carrying spar in a future 180 m wind turbine rotor. FEA is applied to investigate two basic designs with single skin and sandwich flanges respectively...

Active load reduction by means of trailing edge flaps on a wind turbine blade

DEFF Research Database (Denmark)

Couchman, Ian; Castaignet, Damien; Poulsen, Niels Kjølstad

2014-01-01

This paper presents the blade fatigue load reduction achieved with a trailing edge flap during a full scale test on a Vestas V27 wind turbine. A frequency-weighted linear model predictive control (MPC) is tuned to decrease flapwise blade root fatigue loads at the frequencies where most of the blade...... damage occurs, i.e. the 1P and 2P frequencies (respectively 1 and 2 events per revolution). Frequency-weighted MPC is chosen for its ability to handle constraints on the trailing edge flap deflection and to optimise its actuation in order to decrease wear and tear of the actuator. The controller...... was first tested in aero-servo-elastic simulations, before being implemented on a Vestas V27 wind turbine. Consistent load reduction is achieved during the full-scale test. An average of 14% flapwise blade root fatigue load reduction is measured....

Optimization and Reliability Problems in Structural Design of Wind Turbines

DEFF Research Database (Denmark)

Sørensen, John Dalsgaard

2007-01-01

are discussed. Limit state equations are presented for fatigue limit states and for ultimate limit states with extreme wind load, and illustrated by bending failure. Illustrative examples are presented, and as a part of the results optimal reliability levels are obtained which corresponds to an annual...... reliability index equal to 3. An example with fatigue failure indicates that the reliability level is almost the same for single wind turbines and for wind turbines in wind farms if the wake effects are modeled equivalently in the design equation and the limit state equation....

An extreme wind erosion event of the fresh Eyjafjallajökull 2010 volcanic ash.

Science.gov (United States)

Arnalds, Olafur; Thorarinsdottir, Elin Fjola; Thorsson, Johann; Waldhauserova, Pavla Dagsson; Agustsdottir, Anna Maria

2013-01-01

Volcanic eruptions can generate widespread deposits of ash that are subsequently subjected to erosive forces which causes detrimental effects on ecosystems. We measured wind erosion of the freshly deposited Eyjafjallajökull ash at a field site the first summer after the 2010 eruption. Over 30 wind erosion events occurred (June-October) at wind speeds > 10 m s(-1) in each storm with gusts up to 38.7 m s(-1). Surface transport over one m wide transect (surface to 150 cm height) reached > 11,800 kg m(-1) during the most intense storm event with a rate of 1,440 kg m(-1) hr(-1) for about 6½ hrs. This storm is among the most extreme wind erosion events recorded on Earth. The Eyjafjallajökull wind erosion storms caused dust emissions extending several hundred km from the volcano affecting both air quality and ecosystems showing how wind erosion of freshly deposited ash prolongs impacts of volcanic eruptions.

Design off-shore wind climate

Energy Technology Data Exchange (ETDEWEB)

Larsen, G C; Joergensen, H E [Risoe National Lab., Wind Energy and Atmospheric Physics Dept., Roskilde (Denmark)

1999-03-01

Specific recommendations of off-shore turbulence intensities, applicable for design purposes, are lacking in the present IEC-code. The present off-shore wind climate analysis presents the distribution of the turbulence standard deviation around the mean turbulence standard deviation, conditioned on the mean wind speed. Measured distributions, based on a huge amount of measuring data from two shallow water off-shore sites, are parameterized by fitting to a three parameter Weibull distribution. Combining a simple heuristic load model with the parameterized probability density functions of the turbulence standard deviations, an empirical off-shore design turbulence intensity is evaluated that in average yields the same fatigue damage as the distributed turbulence intensity. The proposed off-shore design turbulence intensity is, within the IEC code framework, applicable for extreme as well as for fatigue load determination. (au)

Structural Load Alleviation Applied to Next Generation Aircraft and Wind Turbines

Science.gov (United States)

Frost, Susan

2011-01-01

Reducing the environmental impact of aviation is a goal of the Subsonic Fixed Wing Project under the Fundamental Aeronautics Program of NASAs Aeronautics Research Mission Directorate. Environmental impact of aviation is being addressed by novel aircraft configurations and materials that reduce aircraft weight and increase aerodynamic efficiency. NASA is developing tools to address the challenges of increased airframe flexibility created by wings constructed with reduced structural material and novel light-weight materials. This talk will present a framework and demonstration of a flight control system using optimal control allocation with structural load feedback and constraints to achieve safe aircraft operation. As wind turbines age, they become susceptible to many forms of blade degradation. Results will be presented on work in progress that uses adaptive contingency control for load mitigation in a wind turbine simulation with blade damage progression modeled.

Analysis of Global Sensitivity of Landing Variables on Landing Loads and Extreme Values of the Loads in Carrier-Based Aircrafts

Directory of Open Access Journals (Sweden)

Jin Zhou

2018-01-01

Full Text Available When a carrier-based aircraft is in arrested landing on deck, the impact loads on landing gears and airframe are closely related to landing states. The distribution and extreme values of the landing loads obtained during life-cycle analysis provide an important basis for buffering parameter design and fatigue design. In this paper, the effect of the multivariate distribution was studied based on military standards and guides. By establishment of a virtual prototype, the extended Fourier amplitude sensitivity test (EFAST method is applied on sensitivity analysis of landing variables. The results show that sinking speed and rolling angle are the main influencing factors on the landing gear’s course load and vertical load; sinking speed, rolling angle, and yawing angle are the main influencing factors on the landing gear’s lateral load; and sinking speed is the main influencing factor on the barycenter overload. The extreme values of loads show that the typical condition design in the structural strength analysis is safe. The maximum difference value of the vertical load of the main landing gear is 12.0%. This research may provide some reference for structure design of landing gears and compilation of load spectrum for carrier-based aircrafts.

Aerodynamic loads calculation and analysis for large scale wind turbine based on combining BEM modified theory with dynamic stall model

Energy Technology Data Exchange (ETDEWEB)

Dai, J.C. [College of Mechanical and Electrical Engineering, Central South University, Changsha (China); School of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan (China); Hu, Y.P.; Liu, D.S. [School of Electromechanical Engineering, Hunan University of Science and Technology, Xiangtan (China); Long, X. [Hara XEMC Windpower Co., Ltd., Xiangtan (China)

2011-03-15

The aerodynamic loads for MW scale horizontal-axis wind turbines are calculated and analyzed in the established coordinate systems which are used to describe the wind turbine. In this paper, the blade element momentum (BEM) theory is employed and some corrections, such as Prandtl and Buhl models, are carried out. Based on the B-L semi-empirical dynamic stall (DS) model, a new modified DS model for NACA63-4xx airfoil is adopted. Then, by combing BEM modified theory with DS model, a set of calculation method of aerodynamic loads for large scale wind turbines is proposed, in which some influence factors such as wind shear, tower, tower and blade vibration are considered. The research results show that the presented dynamic stall model is good enough for engineering purpose; the aerodynamic loads are influenced by many factors such as tower shadow, wind shear, dynamic stall, tower and blade vibration, etc, with different degree; the single blade endures periodical changing loads but the variations of the rotor shaft power caused by the total aerodynamic torque in edgewise direction are very small. The presented study approach of aerodynamic loads calculation and analysis is of the university, and helpful for thorough research of loads reduction on large scale wind turbines. (author)

Mitigation of Fatigue Loads Using Individual Pitch Control of Wind Turbines Based on FAST

DEFF Research Database (Denmark)

Zhang, Yunqian; Chen, Zhe; Cheng, Ming

2011-01-01

moments and fatigue. The loading transfer from rotational coordinate system to the fixed coordinate system of the wind turbine is analyzed. In order to make the simulation results more reliable, the wind turbine code FAST is applied to doubly fed induction generator (DFIG) based power system...

Design Loads on Platforms on Offshore wind Turbine Foundations with Respect to Vertical Wave Run-up

DEFF Research Database (Denmark)

Damsgaard, Mathilde L.; Gravesen, Helge; Andersen, Thomas Lykke

2007-01-01

reduction in the loads by up to 75%. Furthermore it is indicated, that the fact that offshore wind turbines often are placed on limited water depths thereby increasing the amount of (nearly) breaking waves, seems to increase the run-up height and thereby the pressures on the structure.......Experiences have shown that the vertical run-up generated by waves meeting the offshore wind turbine foundations, can result in rather vigorous loads on appurtenances and platform structures. This study aims to provide a qualitative method of determining run-up height and the following loads...

Detailed Load Analysis of the baseline 5MW DeepWind Concept

DEFF Research Database (Denmark)

Verelst, David Robert; Aagaard Madsen, Helge; Kragh, Knud Abildgaard

This report presents an overview of the design of the DeepWind vertical axis oating wind turbine. One could present this as the "nal design", however, it is hoped that more design iterations will follow in the future, but under the umbrella of new and dierent projects. The state of the design...... that is reported here will be called version 2.2.0. The numbering system has just been introduced at the present design version, but the rst 5MW design called the "baseline design" [1] was developed in 2011 and this will therefore be called version 1.0.0. In this report, the design loads of the DeepWind 5 MW...

Analyzing the Energy Performance, Wind Loading, and Costs of Photovoltaic Slat Modules on Commercial Rooftops

Energy Technology Data Exchange (ETDEWEB)

Van Geet, Otto D. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Fu, Ran [National Renewable Energy Lab. (NREL), Golden, CO (United States); Horowitz, Kelsey A. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kurup, Parthiv [National Renewable Energy Lab. (NREL), Golden, CO (United States); MacAlpine, Sara M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Silverman, Timothy J. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

2018-02-13

NREL studied a new type of photovoltaic (PV) module configuration wherein multiple narrow, tilted slats are mounted in a single frame. Each slat of the PV slat module contains a single row of cells and is made using ordinary crystalline silicon PV module materials and processes, including a glass front sheet and weatherproof polymer encapsulation. Compared to a conventional ballasted system, a system using slat modules offer higher energy production and lower weight at lower LCOE. The key benefits of slat modules are reduced wind loading, improved capacity factor and reduced installation cost. First, the individual slats allow air to flow through, which reduce wind loading. Using PV performance modeling software, we compared the performance of an optimized installation of slats modules to a typical installation of conventional modules in a ballasted rack mounting system. Based on the results of the performance modeling two different row tilt and spacing were tested in a wind tunnel. Scaled models of the PV Slat modules were wind tunnel tested to quantify the wind loading of a slat module system on a commercial rooftop, comparing the results to conventional ballasted rack mounted PV modules. Some commercial roofs do not have sufficient reserve dead load capacity to accommodate a ballasted system. A reduced ballast system design could make PV system installation on these roofs feasible for the first time without accepting the disadvantages of penetrating mounts. Finally, technoeconomic analysis was conducted to enable an economic comparison between a conventional commercial rooftop system and a reduced-ballast slat module installation.

Statistical Modeling of Extreme Values and Evidence of Presence of Dragon King (DK) in Solar Wind

Science.gov (United States)

Gomes, T.; Ramos, F.; Rempel, E. L.; Silva, S.; C-L Chian, A.

2017-12-01

The solar wind constitutes a nonlinear dynamical system, presenting intermittent turbulence, multifractality and chaotic dynamics. One characteristic shared by many such complex systems is the presence of extreme events, that play an important role in several Geophysical phenomena and their statistical characterization is a problem of great practical relevance. This work investigates the presence of extreme events in time series of the modulus of the interplanetary magnetic field measured by Cluster spacecraft on February 2, 2002. One of the main results is that the solar wind near the Earth's bow shock can be modeled by the Generalized Pareto (GP) and Generalized Extreme Values (GEV) distributions. Both models present a statistically significant positive shape parameter which implyies a heavy tail in the probability distribution functions and an unbounded growth in return values as return periods become too long. There is evidence that current sheets are the main responsible for positive values of the shape parameter. It is also shown that magnetic reconnection at the interface between two interplanetary magnetic flux ropes in the solar wind can be considered as Dragon Kings (DK), a class of extreme events whose formation mechanisms are fundamentally different from others. As long as magnetic reconnection can be classified as a Dragon King, there is the possibility of its identification and even its prediction. Dragon kings had previously been identified in time series of financial crashes, nuclear power generation accidents, stock market and so on. It is believed that they are associated with the occurrence of extreme events in dynamical systems at phase transition, bifurcation, crises or tipping points.

Structural Load Analysis of a Wind Turbine under Pitch Actuator and Controller Faults

International Nuclear Information System (INIS)

Etemaddar, Mahmoud; Gao, Zhen; Moan, Torgeir

2014-01-01

In this paper, we investigate the characteristics of a wind turbine under blade pitch angle and shaft speed sensor faults as well as pitch actuator faults. A land-based NREL 5MW variable speed pitch reg- ulated wind turbine is considered as a reference. The conventional collective blade pitch angle controller strategy with independent pitch actuators control is used for load reduction. The wind turbine class is IEC-BII. The main purpose is to investigate the severity of end effects on structural loads and responses and consequently identify the high-risk components according to the type and amplitude of fault using a servo-aero-elastic simulation code, HAWC2. Both transient and steady state effects of faults are studied. Such information is useful for wind turbine fault detection and identification as well as system reliability analysis. Results show the effects of faults on wind turbine power output and responses. Pitch sensor faults mainly affects the vibration of shaft main bearing, while generator power and aerodynamic thrust are not changed significantly, due to independent pitch actuator control of three blades. Shaft speed sensor faults can seriously affect the generator power and aerodynamic thrust. Pitch actuator faults can result in fully pitching of the blade, and consequently rotor stops due to negative aerodynamic torque

Validation of the dynamic wake meander model for loads and power production in the Egmond aan Zee wind farm

DEFF Research Database (Denmark)

Larsen, Torben J.; Aagaard Madsen, Helge; Larsen, Gunner Chr.

2013-01-01

This paper investigates wake effects on load and power production by using the dynamic wake meander (DWM) model implemented in the aeroelastic code HAWC2. The instationary wind farm flow characteristics are modeled by treating the wind turbine wakes as passive tracers transported downstream using...... a meandering process driven by the low frequent cross-wind turbulence components. The model complex is validated by comparing simulated and measured loads for the Dutch Egmond aan Zee wind farm consisting of 36 Vestas V90 turbine located outside the coast of the Netherlands. Loads and production are compared...... for two distinct wind directions—a free wind situation from the dominating southwest and a full wake situation from northwest, where the observed turbine is operating in wake from five turbines in a row with 7D spacing. The measurements have a very high quality, allowing for detailed comparison of both...

Planetary Load Sharing in Three-Point- Mounted Wind Turbine Gearboxes: Preprint

Energy Technology Data Exchange (ETDEWEB)

Guo, Yi [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Keller, Jonathan A [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-09-15

Wind turbine gearboxes do not achieve their expected design life. The cost of gearbox replacements and rebuilds and the downtime associated with these failures increase the cost of wind energy. In 2007, the U.S. Department of Energy established the National Renewable Energy Laboratory (NREL) Gearbox Reliability Collaborative (GRC). Its goals are to understand the root causes of premature gearbox failures and improve their reliability. To date, the GRC has focused on a 750-kW drivetrain with a three-stage, three-point-mounted gearbox. A nonproprietary version of the gearbox containing CRBs with C3 clearances in the planetary stage was customized. Two of these gearboxes, GB1 and GB2, were manufactured and then tested in the National Wind Technology Center's 2.5-MW dynamometer and in the field. Major GRC findings include the detrimental effect of rotor moments on planetary load sharing and predicted fatigue, and the risk of bearing sliding in low-torque conditions for three-point configuration drivetrains. Based on the knowledge gained from testing and analysis of the original design, the GRC gearbox was redesigned to improve its load-sharing characteristics and predicted fatigue. This new gearbox is named GB3. As shown in Figure 1, its key improvement is the incorporation of preloaded TRBs that support the planet carrier and planets. Roller loads can be optimized and bearing life maximized with a small preload [4]. These preloaded bearings, along with interference-fitted planet pins, improve alignments and load-sharing characteristics. A semi-integrated planet bearing design also increases capacity and eliminates outer race fretting. Romax Technology, with Powertrain Engineers and the Timken Company (Timken), completed the redesign. Timken manufactured and instrumented the planet gears and bearings. Brad Foote Gearing manufactured the other gearing and assembled the gearbox.

Performance and load data from Mod-0A and Mod-1 wind turbine generators

Science.gov (United States)

Spera, D. A.; Janetzke, D. C.

1982-01-01

Experimental data, together with supporting analysis, are presented on the power conversion performance and blade loading of large, horizontal-axis wind turbines tested at electric utility sites in the U.S. Four turbine rotor configurations, from 28 to 61 meters in diameter, and data from five test sites are included. Performance data are presented in the form of graphs of power and system efficiency versus free-stream wind speed. Deviations from theoretical performance are analyzed statistically. Power conversion efficiency averaged 0.34 for all tests combined, compared with 0.31 predicted. Round blade tips appeared to improve performance significantly. Cyclic blade loads were normalized to develop load factors which can be used in the design of rotors with rigid hubs.

Model predictive control of trailing edge flaps on a wind turbine blade

Energy Technology Data Exchange (ETDEWEB)

Castaignet, D.B.

2011-11-15

Trailing edge flaps on wind turbine blades have been investigated for several years. Aero-servoelastic simulations carried out with different simulation tools, trailing edge flaps configurations and controller designs proved that trailing edge flaps are a suitable solution for reducing some of the wind turbine fatigue and extreme loads. This potential was confirmed with wind tunnel tests made on blade sections with trailing edge flaps and on a scaled two-bladed wind turbine in a wind tunnel. The work presented in this thesis includes a full-scale test run on a Vestas V27 wind turbine equipped with three trailing edge flaps on one blade, located on DTU's Risoe Campus in Roskilde, Denmark. This thesis is divided into three parts: the controller design, results from simulations, and results from the experiments. The trailing edge flaps controller designed for this project is based on a frequency-weighted model predictive control, tuned in order to target only the flapwise blade root loads at the frequencies contributing the most to blade root fatigue damage (the 1P, 2P and 3P frequencies), and to avoid unnecessary wear and tear of the actuators at high frequencies. A disturbance model consisting in periodic disturbances at the rotor speed harmonic frequencies and a quasi-steady input disturbance is aggregated to an analytical model of a spinning blade with trailing edge flaps. Simulations on a multi-megawatt wind turbine show the potential of the trailing edge flaps to reduce the flapwise blade root fatigue loads by 23%, but also the main shaft and the tower fatigue loads by up to 32%. Extreme loads during normal production also benefit from the trailing edge flaps. At last, the same controller was run on the Vestas V27 wind turbine located at the Risoe Campus of the Technical University of Denmark, in Roskilde, Denmark. One blade of the turbine was equipped with three independent trailing edge flaps. In spite of the failure of several sensors and actuators, the

Online wind turbine measurement laboratory

DEFF Research Database (Denmark)

Hansen, K.S.; Helgesen Pedersen, K.O.; Schmidt Paulsen, U.

2006-01-01

conditions, 3) electrical quantities and 4) mechanical loads in terms of strain gauge signals. The data acquisition system has been designed and implemented by Risø together with students and teachers from DTU. It is based on LabVIEW© combined with a MySQL database for data management. The system enables...... calculations and extreme loads estimation in basic wind turbine courses. Power quality analysis is carried out based on high speed sampled, three-phase voltage and current signals. The wide spectrum of sensors enables a detailed study of the correlation between meteorological, mechanical and electrical...

Comparison of Second-Order Loads on a Tension-Leg Platform for Wind Turbines: Preprint

Energy Technology Data Exchange (ETDEWEB)

Gueydon, S.; Wuillaume, P.; Jonkman, J.; Robertson, A.; Platt, A.

2015-03-01

The first objective of this work is to compare the two floating offshore wind turbine simulation packages {DIFFRAC+aNySIM} and {WAMIT+FAST}. The focus is on second-order wave loads, and so first- and second-order wave loads are applied to a structure sequentially for a detailed comparison and a more precise analysis of the effects of the second-order loads. aNySIM does not have the capability to model flexible bodies, and so the simulations performed in this tool are done assuming a rigid body. FAST also assumes that the platform is rigid, but can account for the flexibility of the tower. The second objective is to study the effects of the second-order loads on the response of a TLP floating wind turbine. The flexibility of the tower must be considered for this investigation, and therefore only FAST is used.

ewec 2007 - Europe's premier wind energy event

International Nuclear Information System (INIS)

Chaviaropoulos, T.

2007-01-01

This online collection of papers - the ewec 2007 proceedings - reflects the various sessions and lectures presented at the ewec wind-energy convention held in Milan in 2007. The first day's sessions looked at the following topics: Renewable Energy Roadmap, the changing structure of the wind industry, politics and programmes, aerodynamics and innovation in turbine design, wind resources and site characterisation (2 sessions), energy scenarios, harmonisation of incentive schemes, structural design and materials, forecasting, integration studies, integrating wind into electricity markets, wind-turbine electrical systems and components, as well as loads, noise and wakes. The second day included sessions on offshore: developments and prospects, extreme wind conditions and forecasting techniques, small wind turbines, distributed generation and autonomous systems cost effectiveness, cost effectiveness of wind energy, financing wind energy concepts, wind and turbulence, wind power plants and grid integration, offshore technology, global challenges and opportunities, aero-elasticity, loads and control, operations and maintenance, carbon trading and the emission trading schemes, investment strategies of power producers, wind power plants and grid integration, wind turbine electrical systems and components, and wakes. The third day offered sessions on environmental issues, condition monitoring, operation and maintenance, structural design and materials, the Up-Wind workshop, winning hearts and minds, offshore technology, advances in measuring methods and advancing drive-train reliability. In a closing session the conference was summarised, awards for poster contributions were made and the Poul la Cour Prize was presented

Wind Turbine Measurement Technique—an Open Laboratory for Educational Purposes

DEFF Research Database (Denmark)

Pedersen, Knud Ole Helgesen; Hansen, Kurt Schaldemose; Schmidt Paulsen, Uwe

2008-01-01

operational parameters, (ii) meteorological onditions, (iii) electrical quantities and (iv) mechanical loads. The data acquisition system was PC based, and it was combined with a MySQL® database for data management.The system enabled online access for real-time recordings,which were used both...... of non-commercial time series, which would be available for practicing fatigue calculations and extreme load estimation in basic wind turbine courses. Power quality analysis was carried out based on high-speed-sampled, three-phase voltage and current signals. The wide spectrum of sensors enabled....... The WTMLAB was included in a new course entitled Wind Turbine Measurement Techniques....

Loads in wind farms under non-neutral ABL stability conditions: A full-scale validation study of the DWM model

DEFF Research Database (Denmark)

The purpose of this study is twofold: To validate a generalized version of the DWM approach for load prediction under non-neural atmospheric stability conditions, and to demonstrate the importance of atmospheric stability for wind turbines operating in wind farm conditions.......The purpose of this study is twofold: To validate a generalized version of the DWM approach for load prediction under non-neural atmospheric stability conditions, and to demonstrate the importance of atmospheric stability for wind turbines operating in wind farm conditions....

Wind and load forecast error model for multiple geographically distributed forecasts

Energy Technology Data Exchange (ETDEWEB)

Makarov, Yuri V.; Reyes-Spindola, Jorge F.; Samaan, Nader; Diao, Ruisheng; Hafen, Ryan P. [Pacific Northwest National Laboratory, Richland, WA (United States)

2010-07-01

The impact of wind and load forecast errors on power grid operations is frequently evaluated by conducting multi-variant studies, where these errors are simulated repeatedly as random processes based on their known statistical characteristics. To simulate these errors correctly, we need to reflect their distributions (which do not necessarily follow a known distribution law), standard deviations. auto- and cross-correlations. For instance, load and wind forecast errors can be closely correlated in different zones of the system. This paper introduces a new methodology for generating multiple cross-correlated random processes to produce forecast error time-domain curves based on a transition probability matrix computed from an empirical error distribution function. The matrix will be used to generate new error time series with statistical features similar to observed errors. We present the derivation of the method and some experimental results obtained by generating new error forecasts together with their statistics. (orig.)

Mapping of grid faults and grid codes[Wind turbines

Energy Technology Data Exchange (ETDEWEB)

Iov, F. [Aalborg Univ., Inst. of Energy Technology (Denmark); Hansen, Anca D.; Soerensen, Poul; Cutululis, N.A. [Risoe National Lab. - DTU, Wind Enegy Dept., Roskilde (Denmark)

2007-06-15

The objective of this project is to investigate into the consequences of the new grid connection requirements for the fatigue and extreme loads of wind turbines. The goal is also to clarify and define possible new directions in the certification process of power plant wind turbines, namely wind turbines, which participate actively in the stabilisation of power systems. Practical experience shows that there is a need for such investigations. The grid connection requirements for wind turbines have increased significantly during the last 5-10 years. Especially the requirements for wind turbines to stay connected to the grid during and after voltage sags, imply potential challenges in the design of wind turbines. These requirements pose challenges for the design of both the electrical system and the mechanical structure of wind turbines. An overview over the frequency of grid faults and the grid connection requirements in different relevant countries is done in this report. The most relevant study cases for the quantification of the loads' impact on the wind turbines' lifetime are defined. The goal of this report is to present a mapping of different grid fault types and their frequency in different countries. The report provides also a detailed overview of the Low Voltage Ride-Through Capabilities for wind turbines in different relevant countries. The most relevant study cases for the quantification of the loads' impact on the wind turbines' lifetime are defined. (au)

Assessing Fatigue and Ultimate Load Uncertainty in Floating Offshore Wind Turbines Due to Varying Simulation Length

Energy Technology Data Exchange (ETDEWEB)

Stewart, G.; Lackner, M.; Haid, L.; Matha, D.; Jonkman, J.; Robertson, A.

2013-07-01

With the push towards siting wind turbines farther offshore due to higher wind quality and less visibility, floating offshore wind turbines, which can be located in deep water, are becoming an economically attractive option. The International Electrotechnical Commission's (IEC) 61400-3 design standard covers fixed-bottom offshore wind turbines, but there are a number of new research questions that need to be answered to modify these standards so that they are applicable to floating wind turbines. One issue is the appropriate simulation length needed for floating turbines. This paper will discuss the results from a study assessing the impact of simulation length on the ultimate and fatigue loads of the structure, and will address uncertainties associated with changing the simulation length for the analyzed floating platform. Recommendations of required simulation length based on load uncertainty will be made and compared to current simulation length requirements.

Decentralized/stand-alone hybrid Wind-Diesel power systems to meet residential loads of hot coastal regions

International Nuclear Information System (INIS)

Elhadidy, M.A.; Shaahid, S.M.

2005-01-01

In view of rising costs, pollution and fears of exhaustion of oil and coal, governments around the world are encouraging to seek energy from renewable/sustainable energy sources such as wind. The utilization of energy from wind (since the oil embargo of the 1970s) is being widely disseminated for displacement of fossil fuel produced energy and to reduce atmospheric degradation. A system that consists of a wind turbine and Diesel genset is called a Wind-Diesel power system.The literature indicates that the commercial/residential buildings in Saudi Arabia consume an estimated 10-40% of the total electric energy generated. In the present study, the hourly mean wind-speed data of the period 1986-1997 recorded at the solar radiation and meteorological station, Dhahran (26 deg. 32'N, 50 deg. 13'E in the Eastern Coastal Region of Saudi Arabia), has been analyzed to investigate the potential of utilizing hybrid (Wind-Diesel) energy conversion systems to meet the load requirements of a hundred typical two bedroom residential buildings (with annual electrical energy demand of 3512 MWh). The long term monthly average wind speeds for Dhahran range from 4.2 to 6.4 m/s. The hybrid systems considered in the present case study consist of different combinations/clusters of 150 kW commercial wind machines supplemented with battery storage and Diesel back-up. The deficit energy generated by the Diesel generator (for different battery capacities) and the number of operational hours of the Diesel system to meet a specific annual electrical energy demand of 3512 MWh have also been presented. The evaluation of the hybrid system shows that with seven 150 kW wind energy conversion system (WECS) and one day of battery storage, the Diesel back-up system has to provide 21.6% of the load demand. Furthermore, with three days of battery storage, the Diesel back-up system has to provide 17.5% of the load demand. However, in the absence of battery storage, about 37% of the load needs to be

Load alleviation on wind turbine blades using variable airfoil geometry

Energy Technology Data Exchange (ETDEWEB)

Basualdo, S.

2005-03-01

A two-dimensional theoretical study of the aeroelastic behaviour of an airfoil has been performed, whose geometry can be altered using a rear-mounted flap. This device is governed by a controller, whose objective is to reduce the airfoil displacements and, therefore, the stresses present in a real blade. The aerodynamic problem was solved numerically by a panel method using the potential theory, suitable for modelling attached flows. It is therefore mostly applicable for Pitch Regulated Variable Speed (PRVS) wind turbines, which mainly operate under this flow condition. The results show evident reductions in the airfoil displacements by using simple control strategies having the airfoil position and its first and second derivatives as input, especially at the system's eigenfrequency. The use of variable airfoil geometry is an effective means of reducing the vibration magnitudes of an airfoil that represents a section of a wind turbine blade, when subject to stochastic wind signals. The results of this investigation encourage further investigations with 3D aeroelastic models to predict the reduction in loads in real wind turbines. (author)

Sensitivity Analysis of Expected Wind Extremes over the Northwestern Sahara and High Atlas Region.

Science.gov (United States)

Garcia-Bustamante, E.; González-Rouco, F. J.; Navarro, J.

2017-12-01

A robust statistical framework in the scientific literature allows for the estimation of probabilities of occurrence of severe wind speeds and wind gusts, but does not prevent however from large uncertainties associated with the particular numerical estimates. An analysis of such uncertainties is thus required. A large portion of this uncertainty arises from the fact that historical observations are inherently shorter that the timescales of interest for the analysis of return periods. Additional uncertainties stem from the different choices of probability distributions and other aspects related to methodological issues or physical processes involved. The present study is focused on historical observations over the Ouarzazate Valley (Morocco) and in a high-resolution regional simulation of the wind in the area of interest. The aim is to provide extreme wind speed and wind gust return values and confidence ranges based on a systematic sampling of the uncertainty space for return periods up to 120 years.

PROBABILISTIC HAZARD ASSESSMENT FOR TORNADOES, STRAIGHT-LINE WIND, AND EXTREME PRECIPITATION AT THE SAVANNAH RIVER SITE

Energy Technology Data Exchange (ETDEWEB)

Werth, D.; (NOEMAIL), A.; Shine, G.

2013-12-04

distribution, and extrapolating the values for any return period from the tail of that function. For the DOE mandated return periods, we expect straight winds of 123 mph every 2500 years, and 132mph every 6250 years at any point within the SRS. These values are similar to those from the W98 report (which also used the Gumbel distribution for wind speeds) which gave wind speeds of 115mph and 122 mph for return periods of 2500 years and 6250 years, respectively. For extreme precipitation accumulation periods, we compared the fits of three different theoretical extreme-value distributions, and in the end decided to maintain the use of the Gumbel distribution for each period. The DOE mandated 6-hr accumulated rainfall for return periods of 2500 years and 6250 years was estimated as 7.8 inches and 8.4 inches, respectively. For the 24- hr rainfall return periods of 10,000 years and 25,000 years, total rainfall estimates were 10.4 inches and 11.1 inches, respectively. These values are substantially lower than comparable values provided in the W98 report. This is largely a consequence of the W98 use of a different extreme value distribution with its corresponding higher extreme probabilities.

Feature selection in wind speed prediction systems based on a hybrid coral reefs optimization – Extreme learning machine approach

International Nuclear Information System (INIS)

Salcedo-Sanz, S.; Pastor-Sánchez, A.; Prieto, L.; Blanco-Aguilera, A.; García-Herrera, R.

2014-01-01

Highlights: • A novel approach for short-term wind speed prediction is presented. • The system is formed by a coral reefs optimization algorithm and an extreme learning machine. • Feature selection is carried out with the CRO to improve the ELM performance. • The method is tested in real wind farm data in USA, for the period 2007–2008. - Abstract: This paper presents a novel approach for short-term wind speed prediction based on a Coral Reefs Optimization algorithm (CRO) and an Extreme Learning Machine (ELM), using meteorological predictive variables from a physical model (the Weather Research and Forecast model, WRF). The approach is based on a Feature Selection Problem (FSP) carried out with the CRO, that must obtain a reduced number of predictive variables out of the total available from the WRF. This set of features will be the input of an ELM, that finally provides the wind speed prediction. The CRO is a novel bio-inspired approach, based on the simulation of reef formation and coral reproduction, able to obtain excellent results in optimization problems. On the other hand, the ELM is a new paradigm in neural networks’ training, that provides a robust and extremely fast training of the network. Together, these algorithms are able to successfully solve this problem of feature selection in short-term wind speed prediction. Experiments in a real wind farm in the USA show the excellent performance of the CRO–ELM approach in this FSP wind speed prediction problem

NWTC Researchers Field-Test Advanced Control Turbine Systems to Increase Performance, Decrease Structural Loading of Wind Turbines and Plants

Energy Technology Data Exchange (ETDEWEB)

2015-08-01

Researchers at the National Renewable Energy Laboratory's (NREL's) National Wind Technology Center (NWTC) are studying component controls, including new advanced actuators and sensors, for both conventional turbines as well as wind plants. This research will help develop innovative control strategies that reduce aerodynamic structural loads and improve performance. Structural loads can cause damage that increase maintenance costs and shorten the life of a turbine or wind plant.

Reliability-based design methods to determine the extreme response distribution of offshore wind turbines

NARCIS (Netherlands)

Cheng, P.W.; Bussel, van G.J.W.; Kuik, van G.A.M.; Vugts, J.H.

2003-01-01

In this article a reliability-based approach to determine the extreme response distribution of offshore wind turbines is presented. Based on hindcast data, the statistical description of the offshore environment is formulated. The contour lines of different return periods can be determined.

Probing the extreme wind confinement of the most magnetic O star with COS spectroscopy

Science.gov (United States)

Petit, Veronique

2014-10-01

We propose to obtain phase-resolved UV spectroscopy of the recently discovered magnetic O star NGC 1624-2, which has the strongest magnetic field ever detected in a O-star, by an order of magnitude. We will use the strength and variability of the UV resonance line profiles to diagnose the density, velocity, and ionization structure of NGC 1624-2's enormous magnetosphere that results from entrapment of its stellar wind by its strong, nearly dipolar magnetic field. With this gigantic magnetosphere, NGC 1624-2 represents a new regime of extreme wind confinement that will constrain models of magnetized winds and their surface mass flux properties. A detailed understanding of such winds is necessary to study the rotational braking history of magnetic O-stars, which can shed new light on the fundamental origin of magnetism in massive, hot stars.

Economic emission dispatching with variations of wind power and loads using multi-objective optimization by learning automata

International Nuclear Information System (INIS)

Liao, H.L.; Wu, Q.H.; Li, Y.Z.; Jiang, L.

2014-01-01

Highlights: • Apply multi-objective optimization by learning automata to power system. • Sequentially dimensional search and state memory are incorporated. • Track dispatch under significant variations of wind power and load demand. • Good performance in terms of accuracy, distribution and computation time. - Abstract: This paper is concerned with using multi-objective optimization by learning automata (MOLA) for economic emission dispatching in the environment where wind power and loads vary. With its capabilities of sequentially dimensional search and state memory, MOLA is able to find accurate solutions while satisfying two objectives: fuel cost coupled with environmental emission and voltage stability. Its searching quality and efficiency are measured using the hypervolume indicator for investigating the quality of Pareto front, and demonstrated by tracking the dispatch solutions under significant variations of wind power and load demand. The simulation studies are carried out on the modified midwestern American electric power system and the IEEE 118-bus test system, in which wind power penetration and load variations present. Evaluated on these two power systems, MOLA is fully compared with multi-objective evolutionary algorithm based on decomposition (MOEA/D) and non-dominated sorting genetic algorithm II (NSGA-II). The simulation results have shown the superiority of MOLA over NAGA-II and MOEA/D, as it is able to obtain more accurate and widely distributed Pareto fronts. In the dynamic environment where the operation condition of both wind speed and load demand varies, MOLA outperforms the other two algorithms, with respect to the tracking ability and accuracy of the solutions

Full scale measurements of wind loads on stand-off photovoltaic systems

NARCIS (Netherlands)

Geurts, C.P.W.; Steenbergen, R.D.J.M.; Borri, C.

2009-01-01

Solar energy systems are becoming increasingly popular. A large potential for these systems is found on buildings, in particular on roofs. For existing buildings with pitched roofs, stand-off systems, which can be applied as retrofit solutions, are frequently applied. Wind loads for such systems are

Recommendation for an European wind turbine safety standard

Energy Technology Data Exchange (ETDEWEB)

Hjuler Jensen, P.; Hauge Madsen, P.; Winther-Jensen, M.; Machielse, L.; Stam, W.; Einsfeld, V.; Woelfel, E.; Elliot, G.; Wilde, L. de

1988-09-15

The objective is to establish an European standard for wind safety which should apply for all member countries of the European Communities. The document contains a list of recommended safety requirements in relation to the system, structure, electrical installations, operation and maintenance of wind turbines. The recommended safety standards cover electricity producing wind turbines connected to electricity grids in both single and cluster applications and with a swept area in excess of 25 square meters and/or a rated power of 10kW. The document should be used in combination with The European Standards for Wind Turbine Loads and other relevant European Standards. Environmental condition, with the emphasis of wind conditions and more extreme climatic conditions, are also considered in relation to safety requirements. (AB).

Investigating extreme event loading on coastal bridges using wireless sensor technology

Science.gov (United States)

Gelineau, Douglas A.; Davis, Justin R.; Rice, Jennifer A.

2017-04-01

Coastal infrastructure, such as bridges, are susceptible to many forms of coastal hazards: particularly hurricane surge and wave loading. These two forms of loading can cause catastrophic damage to aging highway infrastructure. It is estimated that storm damage costs the United States about $50 Billion per year. In light of this, it is crucial that we understand the damaging forces placed on infrastructure during storm events so that we can develop safer and more resilient coastal structures. This paper presents the ongoing research to enable the efficient collection of extreme event loads acting on both the substructure and superstructure of low clearance, simple span, reinforced concrete bridges. Bridges of this type were commonly constructed during the 1950's and 60's and are particularly susceptible to deck unseating caused by hurricane surge and wave loading. The sensing technology used to capture this data must be ruggedized to survive in an extremely challenging environment, be designed to allow for redundancy in the event of sensors or other network components being lost in the storm, and be relatively low cost to allow for more bridges to be instrumented per storm event. The prototype system described in this paper includes wireless technology, rapid data transmission, and, for the sensors, self-contained power. While this specific application focuses on hurricane hazards, the framework can be extended to include other natural hazards.

Impacts of Providing Inertial Response on Dynamic Loads of Wind Turbine Drivetrains: Preprint

Energy Technology Data Exchange (ETDEWEB)

Girsang, I. P.; Dhupia, J.; Singh, M.; Gevorgian, V.; Muljadi, E.; Jonkman, J.

2014-09-01

There has been growing demand from the power industry for wind power plants to support power system operations. One such requirement is for wind turbines to provide ancillary services in the form of inertial response. When the grid frequency drops, it is essential for wind turbine generators (WTGs) to inject kinetic energy stored in their inertia into the grid to help arrest the frequency decline. However, the impacts of inertial response on the structural loads of the wind turbine have not been given much attention. To bridge this gap, this paper utilizes a holistic model for both fixed-speed and variable-speed WTGs by integrating the aeroelastic wind turbine model in FAST, developed by the National Renewable Energy Laboratory, with the electromechanical drivetrain model in SimDriveline and SimPowerSystems.

Forces and Moments on Flat Plates of Small Aspect Ratio with Application to PV Wind Loads and Small Wind Turbine Blades

OpenAIRE

Xavier Ortiz; David Rival; David Wood

2015-01-01

To improve knowledge of the wind loads on photovoltaic structures mounted on flat roofs at the high angles required in high latitudes, and to study starting flow on low aspect ratio wind turbine blades, a series of wind tunnel tests were undertaken. Thin flat plates of aspect ratios between 0.4 and 9.0 were mounted on a sensitive three-component instantaneous force and moment sensor. The Reynolds numbers varied from 6 × 10 4 to 2 × 10 5 . Measurements were made for angles of attack between 0°...

Wind Farm Active Power Dispatch for Output Power Maximizing Based on a Wind Turbine Control Strategy for Load Minimizing

DEFF Research Database (Denmark)

Zhang, Baohua; Hu, Weihao; Hou, Peng

2015-01-01

Inclusion of the wake effect in the wind farm control design (WF) can increase the total captured power by wind turbines (WTs), which is usually implemented by derating upwind WTs. However, derating the WT without a proper control strategy will increase the structural loads, caused by operation...... in stall mode. Therefore, the WT control strategy for derating operation should be considered in the attempt at maximizing the total captured power while reducing structural loads. Moreover, electrical power loss on the transmission system inside a WF is also not negligible for maximizing the total output...... power of the WF. In this paper, an optimal active power dispatch strategy based on a WT derating strategy and considering the transmission loss is proposed for maximizing the total output power. The active power reference of each WT is chosen as the optimization variable. A partial swarm optimizing...

Hydrogen ion induced ultralow wear of PEEK under extreme load

Science.gov (United States)

Yan, Shuai; Wang, Anying; Fei, Jixiong; Wang, Zhenyang; Zhang, Xiaofeng; Lin, Bin

2018-03-01

As a high-performance engineering polymer, poly(ether ether ketone) (PEEK) is a perfect candidate material for applications under extreme working conditions. However, its high wear rate greatly shortens its service life. In this study, ultralow friction and wear between PEEK and silicon nitride (Si3N4) under extreme-load conditions (with a mean contact pressure above 100 MPa) are found in acid lubricating solutions. Both friction and wear decrease sharply with decreasing pH. At pH = 1, the friction coefficient decreases by an order of magnitude and the wear rate of the PEEK decreases by two orders of magnitude compared to the results with water lubrication. These reductions in friction and wear occur for different speed, load, and surface roughness conditions. The underlying mechanism can be attributed to the formation of hydrogen-ion-induced electrical double layers on the surfaces of PEEK and Si3N4. The combined effect of the resulting repulsive force, electro-viscosity, and low shear strength of the water layer dramatically reduces both friction and wear.

Assessment of ENSEMBLES regional climate models for the representation of monthly wind characteristics in the Aegean Sea (Greece): Mean and extremes analysis

Science.gov (United States)

Anagnostopoulou, Christina; Tolika, Konstantia; Tegoulias, Ioannis; Velikou, Kondylia; Vagenas, Christos

2013-04-01

The main scope of the present study is the assessment of the ability of three of the most updated regional climate models, developed under the frame of the European research project ENSEMBLES (http://www.ensembles-eu.org/), to simulate the wind characteristics in the Aegean Sea in Greece. The examined models are KNMI-RACMO2, MPI-MREMO, and ICTP - RegCM3. They all have the same spatial resolution (25x25km) and for their future projections they are using the A1B SRES emission scenarios. Their simulated wind data (speed and direction) were compared with observational data from several stations over the domain of study for a time period of 25 years, from 1980 to 2004 on a monthly basis. The primer data were available every three or six hours from which we computed the mean daily wind speed and the prevailing daily wind direction. It should be mentioned, that the comparison was made for the grid point that was the closest to each station over land. Moreover, the extreme speed values were also calculated both for the observational and the simulated data, in order to assess the ability of the models in capturing the most intense wind conditions. The first results of the study showed that the prevailing winds during the winter and spring months have a north - northeastern or a south - south western direction in most parts of the Aegean sea. The models under examination seem to capture quite satisfactorily this pattern as well as the general characteristics of the winds in this area. During summer, winds in the Aegean Sea have mainly north direction and the models have quite good agreement both in simulating this direction and the wind speed. Concerning the extreme wind speed (percentiles) it was found that for the stations in the northern Aegean all the models overestimate the extreme wind indices. For the eastern parts of the Aegean the KNMI and the MPI model underestimate the extreme wind speeds while on the other hand the ICTP model overestimates them. Finally for the

Medium fidelity modelling of loads in wind farms under non-neutral ABL stability conditions – a full-scale validation study

DEFF Research Database (Denmark)

Larsen, Gunner Chr.; Larsen, Torben J.; Chougule, A.

2017-01-01

The aim of the present paper is to demonstrate the capability of medium fidelity modelling of wind turbine component fatigue loading, when the wind turbines are subjected to wake affected non-stationary flow fields under non-neutral atmospheric stability conditions. To accomplish this we combine......) in description of both large- and small scale atmospheric boundary layer turbulence is facilitated by a generalization of the classical Mann spectral tensor, which consistently includes buoyancy effects. With non-stationary wind turbine inflow fields modelled as described above, fatigue loads are obtained using...... the state-of-the art aeroelastic model HAWC2. The Lillgrund offshore wind farm (WF) constitute an interesting case study for wind farm model validation, because the WT interspacing is small, which in turn means that wake effects are significant. A huge data set, comprising 5 years of blade and tower load...

Relevance of aerodynamic modelling for load reduction control strategies of two-bladed wind turbines

Science.gov (United States)

Luhmann, B.; Cheng, P. W.

2014-06-01

A new load reduction concept is being developed for the two-bladed prototype of the Skywind 3.5MW wind turbine. Due to transport and installation advantages both offshore and in complex terrain two-bladed turbine designs are potentially more cost-effective than comparable three-bladed configurations. A disadvantage of two-bladed wind turbines is the increased fatigue loading, which is a result of asymmetrically distributed rotor forces. The innovative load reduction concept of the Skywind prototype consists of a combination of cyclic pitch control and tumbling rotor kinematics to mitigate periodic structural loading. Aerodynamic design tools must be able to model correctly the advanced dynamics of the rotor. In this paper the impact of the aerodynamic modelling approach is investigated for critical operational modes of a two-bladed wind turbine. Using a lifting line free wake vortex code (FVM) the physical limitations of the classical blade element momentum theory (BEM) can be evaluated. During regular operation vertical shear and yawed inflow are the main contributors to periodic blade load asymmetry. It is shown that the near wake interaction of the blades under such conditions is not fully captured by the correction models of BEM approach. The differing prediction of local induction causes a high fatigue load uncertainty especially for two-bladed turbines. The implementation of both cyclic pitch control and a tumbling rotor can mitigate the fatigue loading by increasing the aerodynamic and structural damping. The influence of the time and space variant vorticity distribution in the near wake is evaluated in detail for different cyclic pitch control functions and tumble dynamics respectively. It is demonstrated that dynamic inflow as well as wake blade interaction have a significant impact on the calculated blade forces and need to be accounted for by the aerodynamic modelling approach. Aeroelastic simulations are carried out using the high fidelity multi body

Vientos extremos en la provincia de Neuquén Extreme winds in the province of Neuquén

Directory of Open Access Journals (Sweden)

Jorge L. Lassig

2011-12-01

Full Text Available El objetivo de este trabajo es calcular los valores extremos de la velocidad del viento con distintos modelos propuestos en normas internacionales que son utilizadas tanto en el diseño de parques eólicos como en el de obras civiles. Se describen los modelos empleados y se realizan los cálculos en 5 lugares de la Provincia de Neuquén, utilizando datos de vientos medidos cuyas series tienen entre 8 meses y 5 años de longitud. Los valores extremos se obtienen con una recurrencia media de 50 años, y corresponden a la velocidad del viento media en intervalos de 10 minutos y de 3 segundos. Los valores encontrados se analizan y se los compara entre sí, con mediciones y con valores propuestos en la norma argentina de seguridad de obras civiles. Los valores extremos estimados según la European Wind Turbine Standards II no subestiman las mediciones disponibles, y comparados con los obtenidos por los otros modelos, se observa que las menores diferencias corresponden a las estaciones con series de mayor longitud. El parámetro de forma de Weibull y la longitud de los registros serían los factores más importantes en las estimaciones de los valores extremos de la velocidad del viento.The objective of this work is to calculate the extreme values of wind speed with different models proposed in international standards that are utilized so much in the design of wind farms as in civil structures. The employed models are described and the calculations are carried out in 5 places of the Neuquén Province, utilizing data of winds measured whose series have between 8 months and 5 years of length. The extreme values are obtained with a return period of 50 years and they correspond to the extreme of the 10-minute and 3-second average wind speed. The found values are analysed and it are compared among them, with measurements and with values proposed in the standard of security of civil structures of Argentina. The extremes values that were estimated according

Sources of fatigue damage to passive yaw wind turbine blades

Energy Technology Data Exchange (ETDEWEB)

Laino, D.J. [Univ. of Utah, Salt Lake City, UT (United States)

1997-12-31

Using an integrated computer analysis approach developed at the University of Utah, fatigue damage sources to passive yaw wind turbine blades have been investigated. Models of a rigid hub and teetering hub machine reveal the parameters important to the fatigue design of each type. The teetering hub proved much less susceptible to fatigue damage from normal operation loads. As a result, extreme events were critical to the teetering hub fatigue life. The rigid hub blades experienced extremely large gyroscopic load cycles induced by rapid yaw rates during normal operation. These yaw rates stem from turbulence activity which is shown to be dependent upon atmospheric stability. Investigation revealed that increasing yaw damping is an effective way of significantly reducing these gyroscopic fatigue loads.

Wind pressure loading for tall buidings: a case study of Warsaw Trade Tower

CSIR Research Space (South Africa)

Cwik, M

2012-12-01

Full Text Available of the building model and its surroundings, as well as the testing methods are described. The second part provides a description of the evaluation of the extreme pressure values using Gumbel distribution. Minimum and maximum wind pressure patterns over facade...

A zero torsional stiffness twist morphing blade as a wind turbine load alleviation device

Science.gov (United States)

Lachenal, X.; Daynes, S.; Weaver, P. M.

2013-06-01

This paper presents the design, analysis and realization of a zero stiffness twist morphing wind turbine blade. The morphing blade is designed to actively twist as a means of alleviating the gust loads which reduce the fatigue life of wind turbine blades. The morphing structure exploits an elastic strain energy balance within the blade to enable large twisting deformations with modest actuation requirements. While twist is introduced using the warping of the blade skin, internal pre-stressed members ensure that a constant strain energy balance is achieved throughout the deformation, resulting in a zero torsional stiffness structure. The torsional stability of the morphing blade is characterized by analysing the elastic strain energy in the device. Analytical models of the skin, the pre-stressed components and the complete blade are compared to their respective finite element models as well as experimental results. The load alleviation potential of the adaptive structure is quantified using a two-dimensional steady flow aerodynamic model which is experimentally validated with wind tunnel measurements.

Offshore wind turbine risk quantification/evaluation under extreme environmental conditions

International Nuclear Information System (INIS)

Taflanidis, Alexandros A.; Loukogeorgaki, Eva; Angelides, Demos C.

2013-01-01

A simulation-based framework is discussed in this paper for quantification/evaluation of risk and development of automated risk assessment tools, focusing on applications to offshore wind turbines under extreme environmental conditions. The framework is founded on a probabilistic characterization of the uncertainty in the models for the excitation, the turbine and its performance. Risk is then quantified as the expected value of some risk consequence measure over the probability distributions considered for the uncertain model parameters. Stochastic simulation is proposed for the risk assessment, corresponding to the evaluation of some associated probabilistic integral quantifying risk, as it allows for the adoption of comprehensive computational models for describing the dynamic turbine behavior. For improvement of the computational efficiency, a surrogate modeling approach is introduced based on moving least squares response surface approximations. The assessment is also extended to a probabilistic sensitivity analysis that identifies the importance of each of the uncertain model parameters, i.e. risk factors, towards the total risk as well as towards each of the failure modes contributing to this risk. The versatility and computational efficiency of the advocated approaches is finally exploited to support the development of standalone risk assessment applets for automated implementation of the probabilistic risk quantification/assessment. -- Highlights: ► A simulation-based risk quantification/assessment framework is discussed. ► Focus is on offshore wind turbines under extreme environmental conditions. ► Approach is founded on probabilistic description of excitation/system model parameters. ► Surrogate modeling is adopted for improved computational efficiency. ► Standalone risk assessment applets for automated implementation are supported

Extreme gust wind estimation using mesoscale modeling

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Kruger, Andries

2014-01-01

, surface turbulence characteristics. In this study, we follow a theory that is different from the local gust concept as described above. In this theory, the gust at the surface is non-local; it is produced by the deflection of air parcels flowing in the boundary layer and brought down to the surface...... from the Danish site Høvsøre help us to understand the limitation of the traditional method. Good agreement was found between the extreme gust atlases for South Africa and the existing map made from a limited number of measurements across the country. Our study supports the non-local gust theory. While...... through turbulent eddies. This process is modeled using the mesoscale Weather Forecasting and Research (WRF) model. The gust at the surface is calculated as the largest winds over a layer where the averaged turbulence kinetic energy is greater than the averaged buoyancy force. The experiments have been...

Average profiles of the solar wind and outer radiation belt during the extreme flux enhancement of relativistic electrons at geosynchronous orbit

Directory of Open Access Journals (Sweden)

R. Kataoka

2008-06-01

Full Text Available We report average profiles of the solar wind and outer radiation belt during the extreme flux enhancement of relativistic electrons at geosynchronous orbit (GEO. It is found that seven of top ten extreme events at GEO during solar cycle 23 are associated with the magnetosphere inflation during the storm recovery phase as caused by the large-scale solar wind structure of very low dynamic pressure (<1.0 nPa during rapid speed decrease from very high (>650 km/s to typical (400–500 km/s in a few days. For the seven events, the solar wind parameters, geomagnetic activity indices, and relativistic electron flux and geomagnetic field at GEO are superposed at the local noon period of GOES satellites to investigate the physical cause. The average profiles support the "double inflation" mechanism that the rarefaction of the solar wind and subsequent magnetosphere inflation are one of the best conditions to produce the extreme flux enhancement at GEO because of the excellent magnetic confinement of relativistic electrons by reducing the drift loss of trapped electrons at dayside magnetopause.

Recipes for correcting the impact of effective mesoscale resolution on the estimation of extreme winds

DEFF Research Database (Denmark)

Larsén, Xiaoli Guo; Ott, Søren; Badger, Jake

2012-01-01

Extreme winds derived from simulations using mesoscale models are underestimated due to the effective spatial and temporal resolutions. This is reflected in the spectral domain as an energy deficit in the mesoscale range. The energy deficit implies smaller spectral moments and thus underestimatio...

Extreme Sea Conditions in Shallow Water: Estimation based on in-situ measurements

Science.gov (United States)

Le Crom, Izan; Saulnier, Jean-Baptiste

2013-04-01

The design of marine renewable energy devices and components is based, among others, on the assessment of the environmental extreme conditions (winds, currents, waves, and water level) that must be combined together in order to evaluate the maximal loads on a floating/fixed structure, and on the anchoring system over a determined return period. Measuring devices are generally deployed at sea over relatively short durations (a few months to a few years), typically when describing water free surface elevation, and extrapolation methods based on hindcast data (and therefore on wave simulation models) have to be used. How to combine, in a realistic way, the action of the different loads (winds and waves for instance) and which correlation of return periods should be used are highly topical issues. However, the assessment of the extreme condition itself remains a not-fully-solved, crucial, and sensitive task. Above all in shallow water, extreme wave height, Hmax, is the most significant contribution in the dimensioning process of EMR devices. As a case study, existing methodologies for deep water have been applied to SEMREV, the French marine energy test site. The interest of this study, especially at this location, goes beyond the simple application to SEMREV's WEC and floating wind turbines deployment as it could also be extended to the Banc de Guérande offshore wind farm that are planned close by. More generally to pipes and communication cables as it is a redundant problematic. The paper will first present the existing measurements (wave and wind on site), the prediction chain that has been developed via wave models, the extrapolation methods applied to hindcast data, and will try to formulate recommendations for improving this assessment in shallow water.

ewec 2007 - Europe's premier wind energy event

Energy Technology Data Exchange (ETDEWEB)

Chaviaropoulos, T. (ed.)

2007-07-01

This online collection of papers - the ewec 2007 proceedings - reflects the various sessions and lectures presented at the ewec wind-energy convention held in Milan in 2007. The first day's sessions looked at the following topics: Renewable Energy Roadmap, the changing structure of the wind industry, politics and programmes, aerodynamics and innovation in turbine design, wind resources and site characterisation (2 sessions), energy scenarios, harmonisation of incentive schemes, structural design and materials, forecasting, integration studies, integrating wind into electricity markets, wind-turbine electrical systems and components, as well as loads, noise and wakes. The second day included sessions on offshore: developments and prospects, extreme wind conditions and forecasting techniques, small wind turbines, distributed generation and autonomous systems cost effectiveness, cost effectiveness of wind energy, financing wind energy concepts, wind and turbulence, wind power plants and grid integration, offshore technology, global challenges and opportunities, aero-elasticity, loads and control, operations and maintenance, carbon trading and the emission trading schemes, investment strategies of power producers, wind power plants and grid integration, wind turbine electrical systems and components, and wakes. The third day offered sessions on environmental issues, condition monitoring, operation and maintenance, structural design and materials, the Up-Wind workshop, winning hearts and minds, offshore technology, advances in measuring methods and advancing drive-train reliability. In a closing session the conference was summarised, awards for poster contributions were made and the Poul la Cour Prize was presented.

Structural optimization procedure of a composite wind turbine blade for reducing both material cost and blade weight

Science.gov (United States)

Hu, Weifei; Park, Dohyun; Choi, DongHoon

2013-12-01

A composite blade structure for a 2 MW horizontal axis wind turbine is optimally designed. Design requirements are simultaneously minimizing material cost and blade weight while satisfying the constraints on stress ratio, tip deflection, fatigue life and laminate layup requirements. The stress ratio and tip deflection under extreme gust loads and the fatigue life under a stochastic normal wind load are evaluated. A blade element wind load model is proposed to explain the wind pressure difference due to blade height change during rotor rotation. For fatigue life evaluation, the stress result of an implicit nonlinear dynamic analysis under a time-varying fluctuating wind is converted to the histograms of mean and amplitude of maximum stress ratio using the rainflow counting algorithm Miner's rule is employed to predict the fatigue life. After integrating and automating the whole analysis procedure an evolutionary algorithm is used to solve the discrete optimization problem.

Wind and Wave Setup Contributions to Extreme Sea Levels at a Tropical High Island: A Stochastic Cyclone Simulation Study for Apia, Samoa

Directory of Open Access Journals (Sweden)

Ron Karl Hoeke

2015-09-01

Full Text Available Wind-wave contributions to tropical cyclone (TC-induced extreme sea levels are known to be significant in areas with narrow littoral zones, particularly at oceanic islands. Despite this, little information exists in many of these locations to assess the likelihood of inundation, the relative contribution of wind and wave setup to this inundation, and how it may change with sea level rise (SLR, particularly at scales relevant to coastal infrastructure. In this study, we explore TC-induced extreme sea levels at spatial scales on the order of tens of meters at Apia, the capitol of Samoa, a nation in the tropical South Pacific with typical high-island fringing reef morphology. Ensembles of stochastically generated TCs (based on historical information are combined with numerical simulations of wind waves, storm-surge, and wave setup to develop high-resolution statistical information on extreme sea levels and local contributions of wind setup and wave setup. The results indicate that storm track and local morphological details lead to local differences in extreme sea levels on the order of 1 m at spatial scales of less than 1 km. Wave setup is the overall largest contributor at most locations; however, wind setup may exceed wave setup in some sheltered bays. When an arbitrary SLR scenario (+1 m is introduced, overall extreme sea levels are found to modestly decrease relative to SLR, but wave energy near the shoreline greatly increases, consistent with a number of other recent studies. These differences have implications for coastal adaptation strategies.

More power and less loads in wind farms. 'Heat and flux'

Energy Technology Data Exchange (ETDEWEB)

Corten, G.P.; Schaak, P. [ECN Wind Energy, Petten (Netherlands)

2004-11-01

We consider a farm as a single energy extracting body instead of a superposition of individual energy extractors, i.e. wind turbines. As a result we found two new hypotheses called Heat and Flux. Both hypotheses reveal that the classical operation of turbines in a wind farm at the Lanchester-Betz optimum does not lead to maximum farm output. However, when the turbines at the windward side of the farm are operated below their optimum, then the power of the turbines under the lee increases in such a way that the net farm production increases slightly. Next to this production advantage of Heat and Flux operation there is also a loading advantage. The average axial loading of the upwind turbines of a farm is reduced in a 'Heat and Flux'-farm. As a result those turbines generate less turbines so that the fatigue loads of the downwind turbines reduce too. The results were confirmed by in a boundary layer tunnel by means of differential measurements between a 'Heat and Flux'-farm and a classical farm.

Frequency domain design of gain scheduling control for large wind systems in full-load region

International Nuclear Information System (INIS)

Burlibaşa, A.; Ceangă, E.

2014-01-01

Highlights: • A large wind energy system, operating under full-load regime, is considered. • According to its particularities in frequency domain, control law design is provided. • These particularities are influenced by the interactions of wind–tower–blade ensemble. • Control low, within gain scheduling strategy, is achieved imposing stability reserve. • Supplementary a criterion, aimed at reducing mechanical loads, is imposed. - Abstract: The paper presents the issue of power control law synthesis, in the case of a large wind system that operates under full-load regime, based on dynamic properties details in frequency domain. Solving this problem involves two phases: the establishment of a linearized model as faithfully as possible in various operating points of the full-load region, and synthesis of the power controller, considered with classic structure, taking into account frequency particularities of the obtained linearized model. Obtained linear model of the controlled process is of order 16 and encloses subsystems for tower fore-aft oscillations damping, and for drive-train torsion oscillations damping. The designed controller contains a PI component and a lag compensator for dynamic correction at high frequencies. It is known that the main features of wind system dynamics generated by the interaction of wind–tower–blade ensemble cause a gap in the gain characteristic of the model and complex conjugate zeros, which can move between right and left half-planes, depending on the average wind speed value. Consequently, for control law synthesis an interactive frequency solution is adopted. This is “transparent” in relation to particularities induced by wind–tower–blade interaction. This solution allows evaluation of the extent to which control law is affected by the subsystem for tower oscillations damping. Given the strong dependence between the model and the mean wind speed value, a gain scheduling control law is designed. At

Mechanical Loads Test Report for the U.S. Department of Energy 1.5-Megawatt Wind Turbine

Energy Technology Data Exchange (ETDEWEB)

Santos, Rick [Santos Wind Engineering Technologies, Inc., Portland, ME (United States); van Dam, Jeroen [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2015-07-16

The objective of the test was to obtain a baseline characterization of the mechanical loads of the DOE 1.5 wind turbine located at NREL. The test was conducted in accordance with the International Electrotechnical Commission (IEC) Technical Specification, IEC 61400-13 Wind Turbine Generator Systems – Part 13: Measurement of mechanical loads; First Edition 2001-06 [1]. The National Wind Technology Center (NWTC) at NREL conducted this test in accordance with its quality system procedures so that the final test report meets the full requirements of its accreditation by the American Association for Laboratory Accreditation (A2LA). NREL’s quality system requires that all applicable requirements specified by A2LA and International Standards Organization/IEC 17025 be met or to note any exceptions in the test report.

Optimal control of a fuel cell/wind/PV/grid hybrid system with thermal heat pump load

CSIR Research Space (South Africa)

Sichilalu, S

2016-10-01

Full Text Available This paper presents an optimal energy management strategy for a grid-tied photovoltaic–wind-fuel cell hybrid power supply system. The hybrid system meets the load demand consisting of an electrical load and a heat pump water heater supplying thermal...

Energy Coordinative Optimization of Wind-Storage-Load Microgrids Based on Short-Term Prediction

Directory of Open Access Journals (Sweden)

Changbin Hu

2015-02-01

Full Text Available According to the topological structure of wind-storage-load complementation microgrids, this paper proposes a method for energy coordinative optimization which focuses on improvement of the economic benefits of microgrids in the prediction framework. First of all, the external characteristic mathematical model of distributed generation (DG units including wind turbines and storage batteries are established according to the requirements of the actual constraints. Meanwhile, using the minimum consumption costs from the external grid as the objective function, a grey prediction model with residual modification is introduced to output the predictive wind turbine power and load at specific periods. Second, based on the basic framework of receding horizon optimization, an intelligent genetic algorithm (GA is applied to figure out the optimum solution in the predictive horizon for the complex non-linear coordination control model of microgrids. The optimum results of the GA are compared with the receding solution of mixed integer linear programming (MILP. The obtained results show that the method is a viable approach for energy coordinative optimization of microgrid systems for energy flow and reasonable schedule. The effectiveness and feasibility of the proposed method is verified by examples.

Design of a new urban wind turbine airfoil using a pressure-load inverse method

Energy Technology Data Exchange (ETDEWEB)

Henriques, J.C.C.; Gato, L.M.C. [IDMEC, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Marques da Silva, F. [LNEC - Laboratorio Nacional de Engenharia Civil, Av. Brasil, 101, 1700-066 Lisboa (Portugal); Estanqueiro, A.I. [INETI - Instituto Nacional de Engenharia, Tecnologia e Inovacao Estrada do Paco do Lumiar, 1649-038 Lisboa (Portugal)

2009-12-15

This paper presents the design methodology of a new wind turbine airfoil that achieves high performance in urban environment by increasing the maximum lift. For this purpose, an inverse method was applied to obtain a new wind turbine blade section with constant pressure-load along the chord, at the design inlet angle. In comparison with conventional blade section designs, the new airfoil has increased maximum lift, reduced leading edge suction peak and controlled soft-stall behaviour, due to a reduction of the adverse pressure gradient on the suction side. Wind tunnel experimental results confirmed the computational results. (author)

Wind and tornado guidelines

International Nuclear Information System (INIS)

McDonald, J.R.

1989-01-01

The objective of the Department of Energy Natural Phenomena Hazards Project is to provide guidance and criteria for design of new facilities and for evaluation of existing ones subjected to extreme winds, earthquakes, and floods. This paper describes the treatment of wind and tornado hazards. Four facility-use categories are defined which represent increasing levels of risk to personnel or the environment in the event of a high wind event. Facilities are assigned to a particular category, depending on their mission, value, or toxic material content. The assigned facility-use category determines the design and evaluation criteria. The criteria are based on probabilistic hazard assessment. Performance goals are also specified for each facility-use category. A uniform approach to design wind loads, based on the ANSI A58.1-1982 standard, allows treatment of high winds and hurricane and tornado winds in a similar manner. Based on the wind hazard models, some sites must account for the possibility of tornadoes while others do not. Atmospheric pressure changes and missiles must be taken into account when considering tornadoes. The design and evaluation guidelines are designed to establish consistent levels of risk for different natural phenomena hazards and for facilities at different geographical locations

Sliding mode load frequency control for multi-area time-delay power system with wind power integration

DEFF Research Database (Denmark)

Mi, Yang; Hao, Xuezhi; Liu, Yongjuan

2017-01-01

The interconnected time-delay power system has become an important issue for the open communication network. Meanwhile, due to the output power fluctuation of integrated wind energy, load frequency control (LFC) for power system with variable sources and loads has become more complicated. The novel...

Design of a wind tunnel scale model of an adaptive wind turbine blade for active aerodynamic load control experiments

NARCIS (Netherlands)

Hulskamp, A.W.; Beukers, A.; Bersee, H.E.N.; Van Wingerden, J.W.; Barlas, T.

2007-01-01

Within wind energy research there is a drive towards the development of a “smart rotor”; a rotor of which the loading can be measured and controlled through the application of a sensor system, a control system and an aerodynamic device. Most promising solutions from an aerodynamic point of view are

A zero torsional stiffness twist morphing blade as a wind turbine load alleviation device

International Nuclear Information System (INIS)

Lachenal, X; Daynes, S; Weaver, P M

2013-01-01

This paper presents the design, analysis and realization of a zero stiffness twist morphing wind turbine blade. The morphing blade is designed to actively twist as a means of alleviating the gust loads which reduce the fatigue life of wind turbine blades. The morphing structure exploits an elastic strain energy balance within the blade to enable large twisting deformations with modest actuation requirements. While twist is introduced using the warping of the blade skin, internal pre-stressed members ensure that a constant strain energy balance is achieved throughout the deformation, resulting in a zero torsional stiffness structure. The torsional stability of the morphing blade is characterized by analysing the elastic strain energy in the device. Analytical models of the skin, the pre-stressed components and the complete blade are compared to their respective finite element models as well as experimental results. The load alleviation potential of the adaptive structure is quantified using a two-dimensional steady flow aerodynamic model which is experimentally validated with wind tunnel measurements. (paper)

Thermal Loading and Lifetime Estimation for Power Device Considering Mission Profiles in Wind Power Converter

DEFF Research Database (Denmark)

Ma, Ke; Liserre, Marco; Blaabjerg, Frede

2015-01-01

for the reliability improvement and also for cost reduction of wind power technology. Unfortunately, the existing lifetime estimation methods for the power electronic converter are not yet suitable in the wind power application, because the comprehensive mission profiles are not well specified and included......As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial...... devices, more detailed information of the lifetime-related performance in wind power converter can be obtained. Some experimental results are also included to validate the thermal behavior of power device under different mission profiles....

Development of SMA Actuated Morphing Airfoil for Wind Turbine Load Alleviation

Science.gov (United States)

Karakalas, A.; Machairas, T.; Solomou, A.; Riziotis, V.; Saravanos, D.

Wind turbine rotor upscaling has entered a range of rotor diameters where the blade structure cannot sustain the increased aerodynamic loads without novel load alleviation concepts. Research on load alleviation using morphing blade sections is presented. Antagonistic shape memory alloy (SMA) actuators are implemented to deflect the section trailing edge (TE) to target shapes and target time-series relating TE movement with changes in lift coefficient. Challenges encountered by the complex thermomechanical response of morphing section and the enhancement of SMA transient response to achieve frequencies meaningful for aerodynamic load alleviation are addressed. Using a recently developed finite element for SMA actuators [1], actuator configurations are considered for fast cooling and heating cycles. Numerical results quantify the attained ranges of TE angle movement, the moving time period and the developed stresses. Estimations of the attained variations of lift coefficient vs. time are also presented to assess the performance of the morphing section.

Low-order aeroelastic models of wind turbines for controller design

DEFF Research Database (Denmark)