6 MW漂浮式风电机组极限载荷特性研究

海上风电场建设由近海走向深远海,漂浮式风电机组将会是这一区域最适合的选择。选用华锐6 MW机组,结合东海某海域环境条件和IEC规范,利用气动-水动耦合时域分析方法,对不同基础型式下的风电机组载荷特性进行研究。计算结果表明:漂浮式风电机组叶片、轮毂极限载荷与海上固定式风电机组相比没有明显增加,塔筒底部极限载荷增加幅度可达30%;在正常发电工况和极端空转工况叶片和轮毂极限载荷主要受风载荷控制,而塔筒底部和顶部极限载荷在不同工况受风载荷和波浪载荷影响效果则有不同。     

风电机组塔筒固有频率的计算

风电机组塔筒与叶轮发生共振将严重影响风电机组的安全性。以四川A风场2 MW风电机组为对象,结合瑞利法、工程算法和规范估算公式等对风电机组塔筒进行了固有频率的解析计算,并且利用ANSYS有限元分析软件对风电机组塔筒的三维有限元数值仿真模型进行模态分析,计算出塔筒的理论频率。对比分析了所提出算法的塔筒频率计算结果。分析表明：风电机组正常运转情况下,塔筒不会和风轮发生共振;其中一部分公式精确度较好,可以为塔筒的动态设计提供理论依据,具有一定的实用价值。     

大型风电机组气动响应特性分析

针对大型风电机组柔性多体塔架-叶片耦合结构气动响应问题,文章提出了在不同偏航角度下的分析方法。根据该方法的流程图,建立了大型风电机组柔性多体塔架-叶片耦合结构动力学模型。采用谐波叠加法计算气动载荷分布,考虑塔影效应与风剪切的影响,得出诱导因子时程曲线与气动响应均值。计算结果表明:轴向与切向诱导因子变化较小,尾流稳定;偏航角逐渐增大导致塔顶顺风向位移均值减小,根方差值增大。该结果为大型风电机组运行过程中监测状态参数的变化与流体动力学分析提供了参考。     

大型风力机地震动力学响应及稳定性控制研究

为保障极端复杂环境下风力机塔架的结构安全,以NREL 5 MW风力机为研究对象,基于开源软件FAST预留数据接口开发地震载荷计算模块,研究气动阻尼和地震对风力机结构响应的影响,并在机舱和基础平台安装调谐质量阻尼器(Tuned Mass Damper,TMD),对塔架的振动进行控制。结果表明:塔顶响应主要受地震载荷影响,气动载荷对其影响较小,且气动阻尼在一定程度上可以抑制塔架的动力响应,风-震耦合效应不可忽略;地震诱导塔架振动,安装TMD可有效减缓塔架振动和降低塔架弯矩,保证风力机的结构安全和运行稳定。TMD与结构质量比u=0.01,阻尼系数ξ=0.1时,减振控制效果最佳。     

叶片质量不平衡下风机基础的疲劳性能

为探究基础环式风机基础在叶片质量不平衡时的疲劳性能,文章通过重构风力发电机组叶片质量不平衡模型推导了附加载荷,基于谐波合成法理论对脉动风速谱做单点模拟以计算风电机组气动荷载等基本运行载荷,并以实际工程为例建立了风机叶片—塔筒—基础一体化有限元模型,计算了结构自振特性和基本运行载荷与附加载荷共同作用下的载荷响应。结果表明：风机叶片质量不平衡程度加深会导致基础结构的应力集中现象,加剧应力幅增加,进而影响结构的疲劳性能与寿命;结构中混凝土的受力特性受影响较大,钢筋笼次之,基础环最小。     

基于参数化建模的风电机组塔筒法兰联接螺栓应力计算分析

以某MW级风电机组塔筒法兰联接螺栓为研究对象,对载荷特点进行分析,基于ANSYS Workbench软件,采用参数化建模的方法建立计算模型。对不同预紧力、不同外载荷、不同法兰厚度下的螺栓应力变化规律进行计算分析。研究结果表明:对于承受复杂载荷的风电机组塔筒法兰联接,需考虑外载与联接螺栓应力之间的非线性关系;增加预紧力可减小螺栓应力的波动范围,降低疲劳载荷,适当增加法兰厚度可有效降低螺栓应力,提高螺栓联接强度。     

大型风电机组塔筒应力监测点的选取与预警

针对大型风电机组塔筒应力监测缺失的情况,提出基于ANSYS软件应力点的选取和person相关系数法与灰色神经网络相结合的塔筒应力预警方法。通过软件分析和现场实验,研究风电数据和塔筒应力的关系并进行塔筒预测,并首次应用到风电机组塔筒监测中。通过实例分析验证,结果表明,该方法能够有效地进行塔筒应力监测,为风电机组塔筒的检测提供依据。     

风电机组低电压穿越过程机械载荷特性研究

分析电网电压跌落引起风电机组各主要结构部件机械载荷变化的应力传递过程,通过建立风电机组电气-机械联合仿真模型,仿真研究低电压穿越过程对机械载荷特性的影响。基于低电压穿越期间载荷测试数据,分析低电压穿越期间塔筒机械载荷及其疲劳损伤情况。研究结果表明,低电压穿越过程对风电机组机械载荷特性具有重要影响,尤其是当风力发电机组不具备低电压穿越能力而导致风电机组脱网时。     

叶片覆冰对风电机组关键结构安全性的影响

为研究低温条件下叶片覆冰对风电机组关键部位振动频率、翼型气动性能、发电功率、极限载荷和疲劳载荷的影响,对某3.XMW风电机组在覆冰、未覆冰条件下,基于IEC61400-1标准、线性疲劳累计损伤理论、雨流循环计数法,通过仿真软件建立该机型覆冰、未覆冰两种模型并进行计算。计算结果表明,叶片覆冰导致叶片和塔筒振动降低,翼型升力系数降低,阻力系数升高,发电功率降低,覆冰条件下的叶根、旋转轮毂中心、固定轮毂中心、偏航中心、塔筒底部极限载荷和等效疲劳载荷增大,最大累计循环次数降低,其中叶片挥舞载荷增幅最大。研究成果可为叶片覆冰时机组优化提供参考。     

风浪耦合作用下海上风电机组载荷特性研究

与陆上风电机组不同,海上风电机组承受风载荷以及波浪引起的水动力载荷共同作用。在风浪耦合作用下,海上风电机组基础结构以及各主要结构部件载荷特性更为复杂。为保障海上风电机组的运行结构安全,波浪特性对海上风电机组各主要承载部件载荷的影响应引起重视。该文基于改进的JONSWAP型谱,建立波浪动力学模型,以叶片根部挥舞方向弯矩以及塔筒底部俯仰方向弯矩为例,仿真研究波浪对于风电机组极限与疲劳载荷特性的影响。最后,基于海上风电机组载荷实测与仿真数据,对波浪动力学模型进行验证。     

Dynamic behavior of wind turbines influenced by aerodynamic damping and earthquake intensity

In the present paper the effects of aerodynamic damping and earthquake loads on the dynamic response of flexible‐based wind turbines are studied. A numerical analysis framework (NAF) is developed and applied. NAF is based on a user‐compiled module that is developed for the purposes of the present paper and is fully coupled with an open source tool. The accuracy of the developed NAF is validated through comparisons with predictions that are calculated with the use of different numerical analysis methods and tools. The results indicate that the presence of the aerodynamic loads due to the reduction of the maximum displacement of the tower attributed to the dissipation of earthquake excitation energy in fore‐aft direction. Emergency shutdown triggered by strong earthquakes results to a rapid change of aerodynamic damping, resulting to short‐term instability of the wind turbine. After shutdown of the wind turbine, enhanced dynamic response is observed. For the case where the wind turbine is parked, the maxima displacement and acceleration of tower‐top increase linearly with the peak ground acceleration. With the use of the least‐square method a dimensionless slope of tower‐top displacements is presented representing the seismic response coefficient of tower that can be used to estimate the tower‐top acceleration demand. Moreover, on the basis of the seismic response coefficient, an improved model for the evaluation of load design demand is proposed. This model can provide accurate predictions.     

极限环境载荷诱导风力机结构振动影响分析

风力机桩基、塔架及连接部件构成的支撑结构属顶部承担较大质量的力学结构,地震对其造成的影响远大于常规建筑.针对上述问题,基于NREL开发计算平台,联合TurbSim、AeroDyn、FAST及Seismic,对变风载荷、变地震载荷(波形、强度)下的风力机动力学响应进行研究.发现:地震横波对风力机结构响应造成剧烈影响,纵波...     

大型风力机筒式塔架涡致振动的数值分析

应用有限元数值分析方法分析了1.5MW变速变桨距风电机组圆筒型塔架在非定常气动力作用下的动力学响应.数值计算了塔架的动力特性,考察了风轮及机舱重量对塔架固有频率的影响;研究了作用在圆筒型塔架上的气动力特别是非定常气动力与雷诺数的关系;根据作用在塔架上的气动力,计算了塔顶处横向和顺风向在过临界和超临界条件下的动态位移.计算结果表明:非定常气动力是引起塔架振动的重要原因,研究塔架的动态问题比静态问题更重要.该文的工作也为风力机塔架振动分析和疲劳寿命分析等提供了实用的分析方法.     

Effects of seismic and aerodynamic load interaction on structural dynamic response of multi-megawatt utility scale horizontal axis wind turbines

Horizontal axis wind turbines can experience significant time varying aerodynamic loads that has the potential to cause adverse effects on structural, mechanical, and power production. The progress in the wind industry has caused the construction of wind farms in areas prone to high seismic activity. With the advances in computational tools, a more realistic representation of the behavior of wind turbines should be performed. One of the simulation platforms was developed using the 5 MW NREL utility scale reference turbine model. The performed simulations will be used to evaluate the effects of aerodynamic and seismic load coupling on the power generation and structural dynamics behavior of this structure. Different turbine operational scenarios such as (i) normal operational condition with no earthquake, (ii) idling condition with the presence of seismic loads, (iii) normal operational condition with earthquake, and (iv) earthquake-induced emergency shutdown will be simulated with various loading conditions to show the differences in generated power and dynamic response. The results of this paper provide formulations for calculating generated power and design deriving parameters by considering different intensity measures. Moreover, the effects of aerodynamic damping and pitch control system are presented to shows reduction in the resulting design demand loads.     

Predicting wind turbine blade loads and aeroelastic response using a coupled CFD–CSD method

The aeroelastic response and the airloads of horizontal-axis wind turbine rotor blades were numerically investigated using a coupled CFD–CSD method. The blade aerodynamic loads were obtained from a Navier–Stokes CFD flow solver based on unstructured meshes. The blade elastic deformation was calculated using a FEM-based CSD solver which employs a nonlinear coupled flap-lag-torsion beam theory. The coupling of the CFD and CSD solvers was accomplished in a loosely coupled manner by exchanging the information between the two solvers at infrequent intervals. At first, the present coupled CFD–CSD method was applied to the NREL 5MW reference wind turbine rotor under steady axial flow conditions, and the mean rotor loads and the static blade deformation were compared with other predicted results. Then, the unsteady blade aerodynamic loads and the dynamic blade response due to rotor shaft tilt and tower interference were investigated, along with the influence of the gravitational force. It was found that due to the aeroelastic blade deformation, the blade aerodynamic loads are significantly reduced, and the unsteady dynamic load behaviors are also changed, particularly by the torsional deformation. From the observation of the tower interference, it was also found that the aerodynamic loads are abruptly reduced as the blades pass by the tower, resulting in oscillatory blade deformation and vibratory loads, particularly in the flapwise direction.     

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

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 non‐linear aeroelastic code BHawC, is used to investigate the effect of wind shear on the modal damping of the turbine. In isotropic conditions with a uniform wind field, the modal properties can be extracted from the system matrix transformed into the inertial frame using the Coleman transformation. In shear conditions, an implicit Floquet analysis, which reduces the computational burden associated with classical Floquet analysis, is used for modal analysis. The methods are applied to a 2.3 MW three‐bladed pitch‐regulated wind turbine showing a difference in damping between isotropic and extreme shear conditions at rated wind speed when the turbine is operating closest to stall. The first longitudinal tower mode decreases slightly in damping, whereas the first flapwise backward whirling and symmetric modes increase in damping. This change in damping is attributed to an interaction between the periodic blade mode shapes and the azimuth‐dependent local aerodynamic damping in the shear condition caused by a beginning separation of the flow. Copyright © 2012 John Wiley & Sons, Ltd.     

Identification of support structure damping of a full scale offshore wind turbine in normal operation

The support structure damping of a 3.6 MW pitch controlled variable speed offshore wind turbine on a monopile foundation is estimated both in standstill conditions and in normal operation. The net substructure damping is identified from the parameters of an exponential curve fitted to the relative maxima of an impulse response caused by a boat impact. The result is used in the verification of the non aerodynamic damping in normal operation for low wind speeds. The auto-correlation function technique for damping estimation of a structure under ambient excitation was validated against the identified damping from the decaying time series. The Enhanced Frequency Domain Decomposition (EFDD) method was applied to the wind turbine response under ambient excitation, for estimation of the damping in normal operation. The aero-servo-hydro-elastic tool HAWC2 is validated with offshore foundation load measurements. The model was tuned to the damping values obtained from the boat impact to match the measured loads. Wind turbulence intensity and wave characteristics used in the simulations are based on site measurements. A flexible soil model is included in the analysis. The importance of the correctly simulated damping in the model is stressed for accurate load prediction. Differences in the identified damping between the model and the wind turbine are detailed and explained. Discrepancies between simulated and measured loads are discussed.     

浮式风机水池模型试验与仿真对比分析

为研究浮式风机动力特性以及验证数值仿真的准确性,以中国海装半潜型浮式风机参数为基础,阐述水池模型试验过程和环境工况,重点对试验与数值仿真结果进行对比分析。结果表明,采用推力相似和弗劳德数相似的水池试验方法可以满足验证浮式风机仿真模型的准确性。半潜型浮式风机低频运动响应明显,气动阻尼对共振响应可以起到抑制作用,横荡运动与横摇运动方向上具有较强的耦合现象。塔筒载荷能量主要位于低频段、波频段和风轮1P频率处,其中低频区主要受风载荷控制,波频区主要受波浪控制。     

风力发电机组塔架仿真和分析

简单介绍了风力发电机组塔架的类型和风力发电机组塔架设计的重要性。分别在某种参考风速及其风向改变90°和180°条件下,运用风力发电机组设计软件Bladed for Windows对风力发电机组塔架风载荷进行了仿真分析。最后,结合仿真结果和实际情况分析了叶片安装角、风轮锥角、风轮仰角、悬距、塔架气动阻力系数和塔架线密度等对塔架风载荷的影响。为风力发电机组的塔架设计提供了参考。     

风剪切下塔影效应对水平轴风力机叶片及风轮气动载荷的影响

采用CFD方法,以NH1500三叶片大型水平轴风力机为研究对象,研究额定风速剪切来流下的塔影效应对水平轴风力机叶片和风轮非定常气动载荷的影响。结果表明：剪切来流下,叶片和风轮的气动载荷均呈余弦变化规律,塔影效应的主要影响叶片方位角范围为160°~210°,且该范围不随风剪切指数的变化而变化。相同风剪切指数下,塔影效应对叶片和风轮气动载荷的均方根影响较小,对其波动影响较大。当风剪切指数从0.12增至0.30时,塔影效应下,叶片气动载荷的均方根减小,推力和转矩的波动幅度增大,偏航力矩和倾覆力矩的波动幅度减小;风轮推力和转矩的均方根减小,波动幅度变化较小,而倾覆力矩和偏航力矩的均方根增大,且波动幅度也增大。