Strong stabilization of a wind turbine tower model in the plane of the turbine blades

We investigate the strong stabilization of a wind turbine tower model in the plane of the turbine blades, which comprises a nonuniform SCOLE system and a two-mass drive-train model (with gearbox). The control input is the torque created by the electrical generator. Using a strong stabilization theorem for a class of impedance passive linear systems with bounded control and observation operators, we show that the wind turbine tower model can be strongly stabilized. The control is by static output feedback from the angular velocities of the nacelle and the generator rotor

Load reduction of a monopile wind turbine tower using optimal tuned mass dampers

We investigate to apply tuned mass dampers (TMDs) (one in the fore–aft direction, one in the side– side direction) to suppress the vibration of a monopile wind turbine tower. Using the spectral element method, we derive a finite-dimensional state-space model d from an infinite-dimensional model d of a monopile wind turbine tower stabilised by a TMD located in the nacelle. and d can be used to represent the dynamics of the tower and TMD in either the fore–aft direction or the side– side direction. The wind turbine tower subsystem of is modelled as a non-uniform SCOLE (NASA Spacecraft Control Laboratory Experiment) system consisting of an Euler–Bernoulli beam equation describing the dynamics of the flexible tower and the Newton–Euler rigid body equations describing the dynamics of the heavy rotor-nacelle assembly (RNA) by neglecting any coupling with blade motions. d can be used for fast and accurate simulation for the dynamics of the wind turbine tower as well as for optimal TMD designs. We show that d agrees very well with the FAST (fatigue, aerodynamics, structures and turbulence) simulation of the NREL 5-MW wind turbine model. We optimise the parameters of the TMD by minimising the frequency-limited H2-norm of the transfer function matrix of d which has input of force and torque acting on the RNA, and output of tower-top displacement. The performances of the optimal TMDs in the fore–aft and side–side directions are tested through FAST simulations, which achieve substantial fatigue load reductions. This research also demonstrates how to optimally tune TMDs to reduce vibrations of flexible structures described by partial differential equations

Approximate method for calculating free vibrations of a large-wind-turbine tower structure

A set of ordinary differential equations were derived for a simplified structural dynamic lumped-mass model of a typical large-wind-turbine tower structure. Dunkerley's equation was used to arrive at a solution for the fundamental natural frequencies of the tower in bending and torsion. The ERDA-NASA 100-kW wind turbine tower structure was modeled, and the fundamental frequencies were determined by the simplified method described. The approximate fundamental natural frequencies for the tower agree within 18 percent with test data and predictions analyzed

Towards greener horizontal-axis wind turbines: Analysis of carbon emissions, energy and costs at the early design stage

This paper describes the development of a quantitative analysis system as a platform for rapidly estimate energy, costs and carbon emission to facilitate the comparison of different wind turbine concept designs. This system aimed specifically at wind turbine manufacturing processes due to the fact that a large proportion of the environmental, costs and energy impacts would occur at this stage. The proposed method supports an initial assessment of multiple design concepts which allows the selection and development of a “greener” wind turbine. The developed system enables concept design of commercial wind turbine towers of hub heights between 44 and 135 m. The method supports an accurate estimation in regards to the dimension, energy consumed, maximum power output, costs and carbon emission in the early design phases of a wind turbine. As a result of the development, the proposed approach could potentially be used to minimise the carbon footprints of major engineering projects such as wind farms

Evaluating Tall Wind Turbine Tower Designs

Developing wind turbines taller than the 80 m standard used today is a major focus in the wind turbine industry in order to reach the stronger and steadier winds that occur at these heights. In order to access these winds and increase wind power production efficiency, new designs must be utilized to overcome issues with upscaling the current standard steel tubular tower design. In this research, a cost analysis of steel tubular towers was conducted to determine if this design is cost effective at heights above 80. Through this analysis, it was determined that steel tubular designs become less cost effective as tower height is increased and are not a cost effective option above 80 m. A second cost analysis was conducted to compare four potential 100 m turbine tower designs, each utilizing different materials. Cost estimates for each design were developed to compare capital costs and cost efficiency for both 20 and 40 year life cycles. In this analysis, the Ultra High Performance Concrete design was the most cost effective option. The precast concrete design was second most cost effective, followed by the steelconcrete hybrid design. The steel tubular design was the least cost effective at 100 m

Comparison of wind turbine tower failure modes under seismic and wind loads

This paper studies the structural responses and failure modes of a 1.5-MW horizontal-axis wind turbine under strong ground motions and wind loading. Ground motions were selected and scaled to match the two design response spectra given by the seismic code, and wind loads were generated considering tropical cyclone scenarios. Nonlinear dynamic time-history analyses were conducted and structural performances under wind loads as well as short- and long-period ground motions compared. The results show that under strong wind loads the collapse of the wind turbine tower is driven by the formation of a plastic hinge at the lower section of the tower. This area is also critical when the tower is subject to most ground motions. However, some short-period earthquakes trigger the collapse of the middle and upper parts of the tower due to the increased contribution of high-order vibration modes. Although long-period ground motions tend to result in greater structural responses, short-period earthquakes may cause brittle failure modes in which the full plastic hinge develops quickly in regions of the tower with only a moderate energy dissipation capacity. Based on these results, recommendations for future turbine designs are proposed

A Probabilistic Approach In Long-Term Fatigue Analysis Of Onshore Wind Turbine Tower

To address the fatigue damage induced by wind on the wind turbine tower, the present work introduces a novel probabilistic fatigue assessment framework. The idea is based on the deterministic fatigue approach combining with various statistical and probabilistic techniques. The proposed framework is applied to a Design Load Case (DLC) given in IEC 61400-1 standard using a reference wind turbine and carry out a probability distribution of cumulative fatigue damage on the cross-section of wind turbine tower under a turbulent wind condition

Analysis of support structure of wind turbine tower

Wind turbines are being used to generate electricity as an alternative energy source to conventional fossil fu- els, and it is well known that wind towers must to sus- tain continuous vibration forces throughout their opera- tional life. In this paper, a stability analysis of bending deflection of a wind turbine steel tower is presented. The wind turbine is modelled as the structure of a sim- plified beam-column by a switched system. It is mod- elled by using a Hamiltonian system, which simplifies the system under study and allows to analyze the sta- bility dynamics of the system. An eigenvalue analysis have been done in order to analyze the stability of the system; finally, also, some transient simulations of the system are presented to verify the results obtainedPostprint (published version

Influence of external loads to wind turbine tower

One of the most important parts of a wind turbine is a tower. There are various designs of the wind turbine towers, and they are most often made of steel pipes, lattice towers or concrete towers. In order to increase energy density to meet the growing electricity needs, larger wind turbine projects have been developed. Larger wind turbine towers can generate more electricity, but such large sizes also create higher costs in terms of development and maintenance. This research sets up a model of a wind turbine tower, where the load to the tower is calculated by its relation to the wind velocity. Analytical approach coupled with a finite element method (FEM) is used to analyse the distribution of tower stresses under these loads. The fatigue analysis of the column is performed using the load from its own weight, the weight of the housing and the distribution of the wind velocity. The effects of different loads are also compared. The results show that the main loads of the tower are the wind force acting on the area of ??rotation of the wind turbine blades and the moment caused by the uneven wind velocity. Construction is modelled using SolidWorks modelling package, where the analysis was performed using FEM in ANSYS software. As a result of the analysis, the stress distribution in the support was determined and compared with analytical calculations

Design, fabrication, and initial test of a fixture for reducing the natural frequency of the Mod-O wind turbine tower

It was desired to observe the behavior of a two bladed wind turbine where the tower first bending natural frequency is less than twice the rotor speed. The system then passes through resonance when accelerating to operating speed. The frequency of the original Mod-O tower was reduced by placing it on a spring fixture. The fixture is adjustable to provide a range of tower bending frequencies. Fixture design details are given and behavior during initial operation is described