大型海上风力发电高塔随机最优减震控制

考察了基于结构动力可靠度的调谐液体柱形阻尼器(TLCD)参数优化设计方法,并用于风-地震联合作用及地震作用下海上风力发电高塔系统的随机最优控制。文中,采用Kane动力学-有限元一体化模型,建立了TLCD-结构整体系统方程。基于概率密度演化理论的极值分布方法,给出了基于可靠度的TLCD参数优化设计方法及程序解答。在数值算例中,采用随机谐和函数和物理随机风场模型分别模拟随机地震动和随机风荷载,通过对优化的受控系统进行随机反应分析与可靠度分析,比较了不同控制准则和约束条件下TLCD的减震控制效果。研究表明基于可靠度的随机最优控制方法是可行的。     

考虑流固耦合效应的海上单桩式风电塔动力响应研究

风荷载与波浪荷载是海上风电塔承受的主要荷载,对风电塔结构设计起着决定性作用,其动力响应极为复杂。以南通沿海3.0 MW风电机为研究对象,利用数值模拟和现场实测手段,考虑流固耦合效应,建立"基础-塔筒-机舱-风轮"整机模型、风荷载模型、波浪荷载模型,研究海上风电塔在风-波浪联合作用下的结构动力响应以及不同水深对风电机系统振动频率的影响。计算结果表明:采用考虑流固耦合效应与风电塔整机模型分析得到的计算结果与实测结果较一致,可为海上风电塔结构在风-波浪联合作用下的振动分析和结构设计等提供分析方法;波浪荷载对海上风电塔的动力响应存在一定的影响,以风荷载作为主要荷载计算的结果不甚合理;水深对结构低阶振动频率影响不大,但水深对风电塔系统高阶振动频率影响较大,水深越大,高阶振动频率降幅越大。     

考虑土壤-结构共同作用影响的双曲冷却塔可靠度

本文建立了对风荷载、自重和温度荷载组合作用下的双曲冷却塔结构进行可靠度分析的半随机过程模型,研究了考虑土壤-结构共同作用、塔底用连续弹性支承和离散支柱所造成的可靠度评估差异.运用等效静态的方法,考虑湍流动态风荷载响应.将动态随机过程模型转化为静态随机变量模型.TR荷载组合规则被用来考虑各荷载效应之间的关系.以广东茂名90米双曲冷却塔作为算例,数值结果表明不考虑共同作用的设计是保守的.     

一种基于可靠度分析的简化风振系数

为将风致响应分析与体系可靠性评价结合起来,提出了一种基于可靠度分析的简化风振系数。该简化风振系数通过计算出风荷载动力效应下与静风作用下结构整体最大位移或极限承载能力的比值,将动力可靠度问题转变为静力可靠度问题,方便了可靠度的求解。同时采用该简化风振系数进行分析还能给出峰值因子一个合理的取值。示例验算过程表明,该简化风振系数具有较好的效果。这为实现考虑风致响应的可靠度分析提供了一种方法。     

悬索拉线塔(塔线耦合模型)脉动风分析

基于脉动风的动力特性,采用谐波合成法以Davenport风谱模拟了多条风荷载时程曲线。在时间域内对输电塔做了风振响应时程分析。通过大量的数值模拟和统计分析得到脉动风功率谱和相干函数曲线以及悬索塔四线三塔的耦合模型的风振系数。     

2.5MW海上风力发电机钢塔筒地震响应分析

以福建某海滩单机容量为2.5MW海上风力发电机为原型,应用ABAQUS有限元软件分别建立风力发电塔的地基刚接模型和考虑土与结构相互作用的质量-弹簧-阻尼模型.通过给模型施加地震波,对风力发电塔体系进行地震动力作用时程分析.主要研究了土与结构相互作用（Soil-structure interaction,SSI）对风力发电塔体系地震响应的影响.研究表明,SSI效应降低了风力发电塔的地震应力响应,增加了其地震位移响应.     

风力发电结构动力反应的一体化有限元模型分析

本文通过对风力发电结构系统地震作用下的动力反应的大量研究,提出了一种可用于分析风力发电结构的"桨叶—塔体—基础"一体化有限元模型,并结合土-结构相互作用的分析形成了另一种对比模型。利用上述分析模型对风力发电结构分别进行动力荷载作用下的模态分析和动力时程分析。结果表明,地震作用下考虑土-结构相互作用对风力发电结构动力响应的影响不容忽视,并且可为工程设计提供参考。     

基于ABAQUS的近海塔筒式风机模型建立与模态分析

随着世界各国对新型、清洁、可再生能源的迫切需求,风力发电已成为应用范围十分广泛的一种新能源发电方式,风机结构自身振动和荷载作用下的动力响应是目前工程师们主要关心的课题之一,其中保证风机在自身运行时塔筒的固有自振频率和叶轮旋转频率不发生共振是设计风机时要考虑重要因素之一.采用有限元软件ABAQUS对某一近海塔筒式风力发电...     

数值模拟在高耸结构设计分析中的应用

以沿海地区某输电塔结构为原型,采用数值模拟的方法对结构在风荷载作用下的极限承载力进行了分析,结果表明:台风多发地区的输电塔设计必须考虑台风高湍流引起的动力风荷载增大效应,并指出数值模拟是高耸结构设计分析中经济有效的方法。     

某羊角型输电塔的风振响应分析

本文首先简述了应用线性滤波法中的自回归模型(AR模型)模拟出给定风速功率谱的风速时程序列,并验证其与目标谱的一致性,再通过规范公式推导脉动风载与风速之间的关系,从而得到作用在各节点的脉动风荷载时程样本。本文以某羊角形输电塔为原型进行了模拟计算分析,用有限元分析软件ANSYS建立了有限元模型,并用MATLAB生成塔架迎风面各节点上的风荷载时程信号作为动力输入。利用ANSYS对结构进行了模态分析,结果显示结构的基本模态为平面振动,但是同时具有扭转模态和局部振动模态;对此输电塔结构进行了平均风作用下的静力分析,同时,基于ANSYS时程分析方法计算了结构在一般风荷载作用下的风振响应。结果表明,在考虑一般风荷载作用的情况下,输电塔在顶部出现最大的位移和加速度响应,而在底部出现最大的轴力响应,但由于本文输电塔结构杆件的变截面设计,最大的应力出现在约1/3高处的杆件上。相对于平均风的作用,结构响应在一般风荷载下呈现出明显的动力放大效应。     

Wind field simulation and wind‐induced responses of large wind turbine tower‐blade coupled structure

Herein, by a case study on a 5‐MW wind turbine system developed by Nanjing University of Aeronautics and Astronautics, the wind field simulation and wind‐induced vibration characteristics of wind turbine tower‐blade coupled systems is analyzed. First, the blade‐nacelle‐tower‐basis integrated finite element model with centrifugal forces induced by rotational blades is established. Then, based on a harmony superposition method and the modified blade element‐momentum theory, the fluctuating wind field of tower‐blade coupled systems is simulated, which considers wind shear effect, tower shadow effect, rotational effect, blade‐tower dynamic and model interaction effects. Finally, the wind‐induced dynamic responses and wind vibration coefficients of the wind turbine tower‐blade coupled structure are discussed through the ‘consistent coupled method’ previously proposed by us. The results indicate that the wind‐induced responses of a large wind turbine tower‐blade coupled structure present complicated modal responses and multimode coupling effect. Additionally, the rotational effect would amplify aerodynamic loads on blades with high frequency, wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The centrifugal force effect could also amplify natural vibration frequency of the tower‐blade coupled system and reduce the wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The research could contribute to wind‐resistant design of structure for a large‐scale wind turbine tower‐blade system. Copyright © 2014 John Wiley & Sons, Ltd.     

Simulation of offshore wind turbine response for long-term extreme load prediction

When there is interest in estimating long-term extreme loads for an offshore wind turbine using simulation, statistical extrapolation is the method of choice. While the method itself is rather well-established, simulation effort can be intractable if uncertainty in predicted extreme loads and efficiency in the selected extrapolation procedure are not specifically addressed. Our aim in this study is to address these questions in predicting blade and tower extreme loads based on stochastic response simulations of a 5 MW offshore turbine. We illustrate the use of the peak-over-threshold method to predict long-term extreme loads. To derive these long-term loads, we employ an efficient inverse reliability approach which is shown to predict reasonably accurate long-term loads when compared to the more expensive direct integration of conditional load distributions for different environmental (wind and wave) conditions. Fundamental to the inverse reliability approach is the issue of whether turbine response variability conditional on environmental conditions is modeled in detail or whether only gross conditional statistics of this conditional response are included. We derive long-term loads for both these cases, and demonstrate that careful inclusion of response variability not only greatly influences such long-term load predictions but it also identifies different environmental conditions that bring about these long-term loads compared with when response variability is only approximately modeled. As we shall see, for this turbine, a major source of response variability for both the blade and tower arises from blade pitch control actions due to which a large number of simulations are required to obtain stable distribution tails for the turbine loads studied.     

海上风机的分部与整体结构设计现状

海上风机结构是一个相对复杂的结构系统,其动力响应受到多种环境因素影响,且多种荷载之间的相互作用是一种非线性行为。此外,风力机不同组成部分之间都有其独特特性,结构间的耦合作用决定着风机在非平稳环境力作用下的整体动力反应。分别综述了风机叶片的转动与弹性变形的耦合、塔架与叶片的耦合、塔架的优化设计、基础的模型以及结构随参数变化敏感性分析。最后对未来有待于进一步研究的问题进行介绍。     

Wind field simulation of large horizontal‐axis wind turbine system under different operating conditions

This paper proposes a technique of generating turbulent wind velocities on large horizontal‐axis wind turbine systems under different operating conditions. The rotational sampling effect, vertical wind shear and coherence between wind velocities at blades and on the tower were taken into account. Coordinate system of wind time series at certain discrete sampling points on the vertical plane of the wind turbine is generated by the hybrid weighted amplitude wave superposition and proper orthogonal decomposition (POD) methods. The POD eigenmodes on the blades after updating locations were calculated subsequently using B‐spline surface interpolation method, and the rotationally sampled wind velocities are reconstructed by taking advantage of POD method again. Examples are subsequently presented to validate this proposed technique and demonstrate the generation of wind velocities under different operating conditions. The results show that the simulated spectrum of turbulent wind velocities at blades corresponds well to the measured data and that on the tower agrees well with the fixed point Kaimal spectrum. The reasonable sampling points spacing is suggested to be about 10 m for the wind field simulation of wind turbine system. The proposed method is of great advantage in accuracy and efficiency, which is greatly significant for the fine analysis of multi‐megawatt wind turbines. Copyright © 2015 John Wiley & Sons, Ltd.     

Mitigation of tower and out-of-plane blade vibrations of offshore monopile wind turbines by using multiple tuned mass dampers

Offshore wind turbines are vulnerable to external vibration sources such as wind and wave excitations due to the increasing size and flexibility. It is necessary to mitigate the excessive vibrations of offshore wind turbines to ensure the safety and serviceability during their operations. Some research works have been carried out to control the excessive vibrations of the tower and the in-plane vibrations of blades. Very limited study focuses on the out-of-plane vibration mitigation of blades. In the present study, a detailed finite element (FE) model of the latest NREL 5MW wind turbine is developed by using the FE code ABAQUS. The tower and blades are explicitly modelled, and the rotating of the blades is considered. Multiple tuned mass dampers (MTMDs) are proposed to be installed in the tower and each blade to simultaneously mitigate the out-of-plane vibrations of the tower and blades when the wind turbine is subjected to the combined wind and wave loadings. The effectiveness and robustness of the proposed method are systematically investigated. Numerical results show that MTMDs can effectively mitigate the out-of-plane vibrations of the tower and blades when the wind turbine is in either the operational or parked condition.     

Theoretical study and experimental verification of vibration control of offshore wind turbines by a ball vibration absorber

In this paper, a ball vibration absorber (BVA) is introduced for vibration control of offshore wind turbines. The dynamic responses of offshore wind turbines equipped with a BVA are presented. Both theoretical and experimental investigations are carried out. An analytical model for the wind turbine tower system with installed BVA is developed based on Lagrange's equation. The BVA-structure integrated equations are derived and solved in both time domain and frequency domain. A series of shaking table tests on a 1/13-scale wind turbine model with and without a BVA were carried out to evaluate the effects of BVA on the vibration mitigation of the wind turbine tower system under earthquakes and equivalent wind-wave loads. Numerical simulations of the system are performed and compared with the experimental results. Good agreement between the numerical and experimental results is observed. The results indicate that BVA could effectively improve the performance of the offshore wind turbine.     

锥筒形风机塔架的风致响应分析

用有限元软件Abaqus对近海2.5MW的锥筒形风机塔架结构进行模态分析。通过质量-弹簧-阻尼单元模拟风机塔架的基础,提取它的前八阶模态进行分析。比较塔架固有频率和叶片的旋转频率,发现二者不会发生共振。在模态分析的基础上对风机结构整体进行风致响应分析,验证结构体系的安全性。通过对风机塔架进行风致动力响应分析,为结构的振动特性诊断和预报以及结构动力特性的优化设计提供依据。     

通信角钢塔脉动风荷载模拟及风振响应分析

针对作用于通信角钢塔的风荷载特点,将风荷载中脉动风视为平稳的高斯随机过程.从随机理论出发,考虑空间相关性,采用谐波合成法模拟出脉动风荷载的时程曲线.所采用的人工模拟风速时程曲线可应用于一般高耸结构的脉动风荷载模拟,符合风速随机过程的一般统计特征且具有很好的随机性.最后以通信角钢塔为工程背景,建立有限元模型,采用ANSY...     

Motion analysis of a floating offshore wind turbine considering rotor-rotation

Development of offshore wind energy is desired as a countermeasure against global warming. This article presents motion analysis of a floating offshore wind turbine during the rotor-rotation under wind loads. A 2 MW downwind turbine is mounted on a floating foundation of the spar-type. The wind loads acting on the rotor blades are calculated using the blade element momentum theory. The multibody dynamics system theory is employed to consider the effect of the rotor-rotation. As a result, the motion of yaw, sway and roll are generated due to the effect of the gyro-moment for the rotor-rotation.     

Tuned liquid column dampers in offshore wind turbines for structural control

With offshore wind turbines becoming larger, being moved out further at sea and subjected to ever greater wind and wave forces, it is necessary to analyse the dynamics and minimise the responses of these structures. In this paper, the structural responses of offshore wind turbines are simulated with an attached damper (Tuned Liquid Column Damper (TLCD)) for controlling the vibrations induced within the structure. This requires a realistic simulation of the forces that these tall, flexible and slender structures are subjected to, and consequently the implementation of a damper to control the resulting undesirable vibrations that are induced within the structure. Since sea waves are caused by wind blowing for a sufficiently long time, the state of the sea is related to wind parameters and there exists the possibility of correlating wind and wave loading conditions on structures. The Kaimal spectrum for wind loading is combined with the JONSWAP wave spectrum to formulate correlated wind and wave loadings. The offshore turbine tower is modelled as a Multi-Degree-of-Freedom (MDOF) structure. Cases for flat sea conditions, with which parallels to onshore wind turbines may be drawn, are first simulated. Simulations are presented for the MDOF structure subjected to both ‘moderate’ and ‘strong’ wind and wave loadings. Cases of the blades lumped at the nacelle along with rotating blades are investigated. The reduction in bending moments and structural displacement response with TLCDs for each case are examined. A fatigue analysis is carried out and the implementation of TLCDs is seen to enhance the fatigue life of the structure. An analysis, taking into account the extended fatigue life and reduced bending moments on the structure-TLCD system, is presented.