Vibration attenuation performance of wind turbine tower using a prestressed tuned mass damper under seismic excitation

With the rapid development of large megawatt wind turbines,the operation environment of wind turbine towers(WTTs)has become increasingly complex.In particular,seismic excitation can create a resonance response and cause excessive vibration of the WTT.To investigate the vibration attenuation performance of the WTT under seismic excitations,a novel passive vibration control device,called a prestressed tuned mass damper(PS-TMD),is presented in this study.First,a mathematical model is established based on structural dynamics under seismic excitation.Then,the mathematical analytical expression of the dynamic coefficient is deduced,and the parameter design method is obtained by system tuning optimization.Next,based on a theoretical analysis and parameter design,the numerical results showed that the PS-TMD was able to effectively mitigate the resonance under the harmonic basal acceleration.Finally,the time-history analysis method is used to verify the effectiveness of the traditional pendulum tuned mass damper(PTMD)and the novel PS-TMD device,and the results indicate that the vibration attenuation performance of the PS-TMD is better than the PTMD.In addition,the PS-TMD avoids the nonlinear effect due to the large oscillation angle,and has the potential to dissipate hysteretic energy under seismic excitation.

Rapid seismic analysis methodology for in-service wind turbine towers

The wind energy industry has been growing rapidly during the past decades.Along with this growth,engineering problems have gradually emerged in the wind power industry,including those related to the structural reliability of turbine towers.This study proposes a rapid seismic analysis methodology for existing wind turbine tower structures.The method is demonstrated and validated using a case study on a 1.5 MW tubular steel wind turbine tower.Three finite element(FE)models are developed first.Field tests are conducted to obtain the turbine tower’s vibrational characteristics.The tests include(1) remotely measuring the tower vibration frequencies using a long range laser Doppler Vibrometer and(2) monitoring the tower structural vibration by mounting accelerometers along the height of the tubular structure.In-situ measurements are used to validate and update the FE models of the wind turbine tower.With the updated FE model that represents the practical structural conditions,seismic analyses are performed to study the structural failure,which is defined by the steel yielding of the tubular tower.This research is anticipated to benefit the management of the increasing number of wind energy converters by providing an understanding of the seismic assessment of existing tubular steel wind turbine towers.

Dynamic analysis of wind turbine tower structures in complex ocean environment

Studying and analyzing the dynamic behavior of offshore wind turbines are of great importance to ensure the safety and improve the efficiency of such expensive equipments.In this work,a tapered beam model is proposed to investigate the dynamic response of an offshore wind turbine tower on the monopile foundation assembled with rotating blades in the complex ocean environment.Several environment factors like wind,wave,current,and soil resistance are taken into account.The proposed model is ana-lytically solved with the Galerkin method.Based on the numerical results,the effects of various structure parameters including the taper angle,the height and thickness of the tower,the depth,and the diameter and the cement filler of the monopile on the funda-mental natural frequency of the wind turbine tower system are investigated in detail.It is found that the fundamental natural frequency decreases with the increase in the taper angle and the height and thickness of the tower,and increases with the increase in the diameter of the monopile.Moreover,filling cement into the monopile can effectively im-prove the fundamental natural frequency of the wind turbine tower system,but there is a critical value of the amount of cement maximizing the property of the monopile.This research may be helpful in the design and safety evaluation of offshore wind turbines.

Multi-Objective Structural Optimization of Wind Turbine Tower Using Nondominated Sorting Genetic Algorithm

A multi-objective optimization process for wind turbine steel towers is described in present work.The objective functions are tower top deformation and mass.The tower's height,radius and thickness are considered as design variables.The mathematical relationships between objective functions and variables were predicted by adopting a response surface methodology(RSM).Furthermore,the multi-objective non-dominated sorting genetic algorithm-II(NSGA-II)is adopted to optimize the tower structure to achieve accurate results with the minimum top deformation and total mass.A case study on a 2MW wind turbine tower optimization is given,which computes the desired tower structure parameters.The results are compared with the original tower:a reduction of tower top deformation reduction by about 16.5%and a reduction of a mass by about 1.5%could be achieved for such an optimization process.

Wind Turbine Tower Optimization under Various Requirements by Using Genetic Algorithm

The purpose of this study is to optimize the mass of 1.5 MW wind turbine steel tower performing Genetic Algorithm method (GA). In accordance with ASCE 7-98, AISC-89 and IEC61400-1 , the impact of loads on tower is calculated within the highest safety conditions against buckling strength of each sections of tower by means of GA codes. The stifness along tower is ensured entirely while the mass of tower is mitigated and optimized.

A New Approach for Structural Optimization with Application to Wind Turbine Tower

This work takes the bionic bamboo tower(BBT)of 2 MW wind turbine as the target,and the nondominated sorting genetic algorithm(NSGA-II)is utilized to optimize its structural parameters.Specifically,the objective functions are deformation and mass.Based on the correlation analysis,the target optimization parameters were determined.Furthermore,the Kriging model of the BBT was established through the Latin Hypercube SamplingDesign(LHSD).Finally,the BBT structure is optimized withmultiple objectives under the constraints of strength,natural frequency,and size.The comparison shows that the optimized BBT has an advantage in the Design Load Case(DLC).This advantage is reflected in the fact that the overall stability of the BBT has increased by 2.45%,while the displacement of the BBT has decreased by 0.77%.In addition,the mass of the tower is decreased by 1.49%.Correspondingly,the steel consumption of each BBT will be reduced by 2789 Kg.This work provides a scientific basis for the structural design of the tower in service.

Fatigue Life Prediction for Flange Connecting Bolts of Wind Turbine Tower

Flange joint part is the weak link of wind turbine tower.In view of the special structure,complex stress and easy failure of the connecting bolt of the wind turbine tower flange,the relationship between the external load of the tower section and the internal stress of the bolt is established by the finite element method,and the time series internal stress of the bolt is calculated by the Schmidt-Neuper algorithm.The S-N curve which is suitable for the connecting bolt material of the tower flange is selected by the GL2010 specification.On the basis of Miner’s fatigue cumulative damage theory and rain flow counting method,the fatigue strength of the whole ring bolt is roughly calculated,and the most dangerous part is determined.The axial symmetry model of screw connection is used for accurately calculating the fatigue cumulative damage of the bolt at the dangerous part.The results show that the fatigue life of the bolts in the most dangerous position can meet the requirements,the engineering algorithm has advantages in determining the dangerous part of the whole ring bolt,and the finite element method has high accuracy in predicting the fatigue life of the bolts in the dangerous part.The proposed method is feasible and effective in predicting the fatigue life of the flange joint bolts of the tower.

Multi-Objective Structural Optimization of a Wind Turbine Tower

The 2MW wind turbine tower is considered as the baseline configuration for structural optimization.The design variables consist of the thickness and height located at the top tower junction.The relationships between the design variables and the optimization objectives(mass,equivalent stress,top displacement and fatigue life)are mapped on the basis of uniform design and regression analysis.Subsequently,five solutions are developed by an algorithm,NSGA-III.According to their efficiency and applicability,the most suitable solution is found.This approach yields a decrease of 0.48%in the mass,a decrease of 54.48%in the equivalent stress and an increase of 8.14%in fatigue life,as compared with existing tower designs.An improved wind turbine tower is obtained for this practice.