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.

Influence of Wind Turbine Structural Parameters on Wind Shear and Tower Shadow Effect

To overcome the problems of natural decreases in power quality,and to eliminate wind speed fluctuation due to wind shear and tower shadow effect arising from wind turbine structural parameters,an improved prediction model accounting for the dual effect of wind shear and tower shadow is,in this paper,built.Compared to the conventional prediction model,the proposed model contains a new constraint condition,which makes the disturbance term caused by the tower shadow effect always negative so that the prediction result is closer to the actual situation.Furthermore,wind turbine structural parameters such as hub height,rotor diameter,the diameter of the tower top,and rotor overhang on wind shear and tower shadow effect are also explored in detail.The results show that the wind shear effect became weaker with the increase in hub height.The hub height is independent of the tower shadow effect.The rotor diameter is positively correlated with the wind shear and tower shadow effect.The tower shadow effect is positively correlated with the diameter of the tower top and negatively correlated with the rotor overhang.

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.

Smart Semi-active PID-ACO control strategy for tower vibration reduction in Wind Turbines with MR damper

Wind turbine technology is well known around the globe as an eco-friendly and eff ective renewable power source. However, this technology often faces reliability problems due to structural vibration. This study proposes a smart semi-active vibration control system using Magnetorheological (MR) dampers where feedback controllers are optimized with nature-inspired algorithms. Proportional integral derivative (PID) and Proportional integral (PI) controllers are designed to achieve the optimal desired force and current input for MR the damper. PID control parameters are optimized using an Ant colony optimization (ACO) algorithm. The eff ectiveness of the ACO algorithm is validated by comparing its performance with Ziegler-Nichols (Z-N) and particle swarm optimization (PSO). The placement of the MR damper on the tower is also investigated to ensure structural balance and optimal desired force from the MR damper. The simulation results show that the proposed semi-active PID-ACO control strategy can signifi cantly reduce vibration on the wind turbine tower under diff erent frequencies (i.e., 67%, 73%, 79% and 34.4% at 2 Hz, 3 Hz, 4.6 Hz and 6 Hz, respectively) and amplitudes (i.e. 50%, 58% and 67% for 50 N, 80 N, and 100 N, respectively). In this study, the simulation model is validated with an experimental study in terms of natural frequency, mode shape and uncontrolled response at the 1st mode. The proposed PID-ACO control strategy and optimal MR damper position is also implemented on a lab-scaled wind turbine tower model. The results show that the vibration reduction rate is 66% and 73% in the experimental and simulation study, respectively, at the 1st mode.

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.

Analysis of Near-Wake Deflection Characteristics of Horizontal Axis Wind Turbine Tower under Yaw State

The yaw of the horizontal axis wind turbine results in the deflection of the wake flow field of the tower.The reasonable layout of wind farm can reduce the power loss of the downstream wind turbine generators due to the blocking effect of the upstream wake flow and increase the output power of the whole wind farm.However,there is still much space for further research.In this paper,experimental research is conducted on the near-wake deflection characteristics of wind turbine tower under yaw state,expecting the effect of throwing away a brick in order to get a gem.In the low-turbulence wind tunnel test,regarding the most unfavorable position where the rotating blades coincide with the tower,Particle image velocimetry(PIV)technology is used to test the instantaneous velocity field and output power and analyze experimental data at four different yaw angles,different inflow velocities and heights.Meanwhile,in order to quantitatively analyze the laws on wake deflection,the radon transformation is used to analyze the velocity contour for calculating the wake direction angle,and the results show high reliability.The comprehensive experimental results indicate that the near-wake flow field of the tower obviously deflects towards a side in the horizontal plane.With the increase of the yaw angle,the deflection angle of the wake flow field further increases,and the recovery of wake velocity accelerates.The closer to the blade root,the more complex the flow is,and the influence of the blade on the near wake of the tower is gradually weakened.The change laws on the wake direction angle with the yaw angle and the blade spanwise direction are obtained.The experiment in this paper can provide guidance for layout optimization of wind farm,and the obtained data can provide a scientific basis for the research on performance prediction of horizontal axis wind turbine.

Fluid-structure interaction simulation of dynamic response and wake of floating offshore wind turbine considering tower shadow effect

The comprehensive numerical simulation of the tower shadow effect on floating offshore wind turbines(FOWTs),an area less explored compared to fixed-bottom wind turbines,is presented in this study.The atmospheric boundary layer inflow and the joint north sea wave project random wave are used as the operating conditions for FOWT.The combination of computational fluid dynamics(CFD)software simulator for wind farm applications and turbine simulation tool OpenFAST is used to implement fluid-structure interaction calculations.The output power,platform motion,wake velocity deficit and vortex structures are analyzed to reveal the influence of the tower shadow effect on the FOWT.The results indicate that due to the fluctuation caused by the turbulent wind and the floating platform motion,the tower shadow effect of FOWT is less significant for its periodic power decay than that of fixed-bottom wind turbines.And according to the velocity deficit analysis,the influence area of the tower shadow effect on the wake is mainly in the near wake region.

Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind

The purpose of this study is to improve the efficiency of the power generation system of a solar tower using fluid dynamics. The power generation system of a solar tower can be designed and constructed at relatively low cost. However, the energy output tends to be low for its physical size compared with other renewable energy production systems. The technical and scientific improvement of these types of generation systems has lost its momentum since the shutdown of the wellknown Spanish pilot plant “Manzanares Solar Chimney” in 1989, although it still has the potential to play a role in renewable energy in the future. We have focused on the tower component of the system to seek possible enhancements of the power output of the internal turbine. As a result of our fluid dynamic shape optimization, a diffuser-shaped tower was employed to increase the internal flow speed of a scaled model. The results show a remarkable improvement in the power output of the internal wind turbine.

Erratum to “Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind” [Energy and Power Engineering Vol. 6 No. 11 (October 2014) 362-370]

The original online version of this article (Masataka Motoyama, Kenichiro Sugitani, Yuji Ohya, et al. (2014) “Improving the Power Generation Performance of a Solar Tower Using Thermal Updraft Wind”, 2014, 6, 362-370. http://dx.doi.org/10.4236/epe.2014.611031) was published in October, 2014.The author wishes to correct the following error in text and Figures 9-11.

动态风向变化下风力机叶片和塔架应力及功率特性分析

风向变化显著影响风力机气动载荷分布,从而影响风力机稳定高效的运行,而气动载荷是风力机结构应力和功率变化主要影响因素之一。该文以S翼型三叶片水平轴风力机为研究对象,在旋转平台上进行风洞实验,对不同风向变化速度(0.5°、1°、1.5°、2°/s)下风力机叶片和塔架的应力以及风力机功率特性进行分析。结果表明:风向变化速度为0.5°/s时,在风向由0°变化到30°时,叶片弦向和展向应力值和风力机功率下降幅度最大;在风向由0°变化到20°时,叶片应力值和功率下降较为缓慢,风向变化结束后,风力机应力与功率会进一步减小;风向变化角度在0°~20°范围内,受叶片转速和气动载荷下降速度与风向变化耦合作用的影响,塔架应力值出现较大波动,并随风向变化速度的增加,波动出现的区间从15°~20°提前到0°~5°;风向变化结束后,叶片转速持续下降,造成塔架应力仍有不同程度的波动。结果可为考虑风向变化下运行的风力机结构设计提供一定理论依据。

超高钢混风电塔筒液压导向系统研究

为了更加高效的利用高空风能,作为绿色清洁能源之一的风力发电,朝着风电机组单机容量越来越大、承载基础的塔筒建设高度越来越高的趋势发展。传统锥筒式全钢塔筒逐渐被预应力混凝土-钢组合塔筒所取代。预应力混凝土-钢组合塔筒兼具混凝土塔筒及钢塔筒两者的优势,具有承载力高、稳定性好、运输施工维护方便、建设成本低等特点,以适应较高高度风电场的需求,代表了未来风电塔筒结构发展的方向。由于高空风载荷大、风电机组的偏心载荷大等不利因素,导致提升过程中产生大弯矩和扭转的工况。因此,导向问题已成为预应力混凝土-钢组合塔筒建设中需要首先解决的技术难题。针对这一难题,创新研制了超高钢混风电塔筒导向液压系统,结合传感检测和智能控制算法,克服上述不利因素,依次将混凝土内塔筒和中塔筒提升到位,高质量地实现了国内陆上最高的国家电投鲁阳170 m高的风电钢混塔筒的安装。

风电机组纯钢塔架和组合式塔架动力特性对比研究

对某风电场2.0 MW风电机组120 m高单管式风力发电钢塔和钢-混凝土组合式风力发电塔的振动进行长期监测,分别采用峰值拾取法(PP)和随机子空间法(SSI)对塔架的模态参数进行识别和分析,并与数值分析结果进行对比。结果表明:两座塔架的振动主要以前三阶模态为主,高阶模态的影响不可忽略。相较于钢-混凝土组合塔架,纯钢塔架受塔顶叶轮转动的影响更大,更易发生共振。模态阻尼中气动阻尼占比较大,其与环境风速和桨距角关系密切,与风速呈非线性关系,并且在桨叶变桨时变化明显。对比实测识别和数值分析结果发现,两座塔架的模态频率以及混塔的振型数值分析结果与实测结果比较吻合,钢塔的振型数值分析结果与实测结果存在差异,在运维养护时应重点关注。

近场地震作用下风力发电塔结构振动台试验研究

为研究近场脉冲型地震和竖向地震分量对风力发电塔结构地震响应的影响,以2MW风力发电塔结构为原型,按缩尺比为1/20进行模拟地震振动台试验。选用脉冲型地震Westmorland记录和Chi-Chi记录以及普通地震Taft记录和El-Centro记录作为输入地震动。对比分析结构的动力特性,脉冲效应对结构地震响应的影响,竖向地震分量对结构的地震响应的影响。试验结果表明:在试验过程中风力发电塔结构一直处于弹性工作状态;脉冲型近场地震动对结构的加速度响应、位移响应和应变响应具有显著的影响;竖向地震动分量对塔顶水平加速度响应和水平位移响应的影响较小,但对结构的竖向加速度和竖向位移有显著的影响。因此为提高风力发电塔结构的抗震能力,在结构设计中应更加考虑近场地震的脉冲效应和竖向地震效应的影响。

基于IDA的钢-混凝土混合风电塔筒地震易损性分析

为研究钢-混凝土混合风电塔筒的抗震性能,基于弹塑性纤维梁柱单元理论建立了某钢-混凝土混合风电塔筒二维数值模型,先依据推覆分析结果确定塔筒的5种损伤状态限值,然后分别以截面曲率和考虑高阶振型的复合地震动强度参数IM 1I&2E作为结构需求参数和地震动强度参数,接着选取20条地震动记录进行塔筒的增量动力分析,建立塔筒的地震易损性曲线,并对塔筒的抗震性能进行评估。结果表明:混合塔筒模型的损伤程度与地震动强度参数呈正相关,其抗震性能可满足Ⅶ度(0.15 g)地震作用下的抗震要求,但在Ⅷ度罕遇地震作用下及处于更高烈度区的风电塔筒应当进行专门的抗震设计。

海上漂浮式风电机组塔筒优化方法研究

为适应复杂多变的海上环境,高效利用风资源、减少用钢成本,开展漂浮式风电机组塔筒的结构优化设计。以船载风电机组为研究对象,引入漂浮式基础的动态响应,作为影响塔筒弯曲变形的重要约束条件。在保证风电机组稳定功率输出的前提下,以质量最轻为优化目标,以塔筒构造要求和规范为基本约束条件,建立漂浮式基础风电机组塔筒的数值优化模型,并利用遗传算法完成了模型优化。结果显示,在保证风电机组稳定性和正常功率输出要求下,塔筒的质量降低了35%,刚度提高了25%。

矩形钢管混凝土束风机塔筒风振特性研究

随着风电资源优势区开发逐渐饱和,风电开发的重心开始向风资源条件相对恶劣的低风速地区转移,分布式、大功率、高塔筒和长叶片已经成为风电行业发展趋势。基于此提出了一种新型的矩形钢管混凝土束风机塔筒,该塔筒由矩形钢管混凝土束拼接而成,具有强度高、刚度大和耗能能力强的优点。为研究该塔筒结构的风振响应特性,选用Kaimal脉动风速功率谱,采用谐波合成法模拟风荷载时程曲线,对其进行了动力时程分析,并计算了风振系数及等效静力风荷载。结果表明:该新型塔筒在额定风速下位移塔顶位移最大值为911.84 mm,对应的水平位移角为1/154,符合规范要求。塔筒各构件的强度较好,且具有较大的安全富余度。基于位移等效的阵风荷载因子法计算得到的风振系数值较低;在惯性风荷载法计算得到的等效静力风荷载作用下,结构位移、基底剪力与结构随机振动分析得到的基本一致。

考虑P-Δ效应的钢-混凝土混合塔筒动力响应分析

为了提高风电机组钢-混凝土混合塔筒动力响应的分析效率,将风电机组钢-混凝土混合塔筒视为自由端有集中质量的欧拉-伯努利悬臂梁,提出了动力响应的高效分析方法.该方法考虑了重力二阶效应(P-Δ效应)对整体结构的动力响应,以及钢材与混凝土对结构整体阻尼比的影响.通过与基于ABAQUS的有限元模拟结果进行对比,验证了所提出分析方法的有效性,并研究了P-Δ效应对整体动力响应的影响程度.对比结果表明:与忽略P-Δ效应相比,考虑P-Δ效应时理论分析结果更接近于有限元分析结果;理论分析结果与有限元分析结果关于位移、速度和加速度均方根的最大相对误差分别为3.09%、3.81%、4.63%.这表明所建立的风电机组钢-混凝土混合塔筒动力响应分析模型具有与有限元分析相当的计算精度.