风力机叶片在三维湍流下的载荷分析

载荷计算是风力机设计中最为关键的基础性工作,也是所有后续风力机设计、分析工作的基础.文章研究了在叶片坐标系下风力机主要载荷的确定方法;应用bladed软件计算稳态风速下的稳态运行载荷,并考虑湍流模型的影响;采用Improved yon Karman模型,将得到风文件加载到bladed里,来计算此风速下的空转运行载荷;最后通过自由频谱图验证整机是否有共振现象.     

风力机传动链齿轮齿根疲劳裂纹扩展剩余寿命评估

在叶轮气动载荷模型、柔性传动链模型和齿根弯曲应力模型的基础上,建立了随机风速下风力机传动链齿轮齿根疲劳裂纹扩展剩余寿命计算模型,对不同风速下的齿根弯曲应力进行了计算,分析了随机载荷下裂纹的扩展速率.对1.5 MW风力机太阳轮齿根疲劳裂纹的扩展进行了分析.结果表明:风力机齿轮齿根疲劳裂纹扩展寿命主要受风载荷影响,且紧急制动等冲击对裂纹扩展后期的影响不可忽视.     

基于激光雷达的风力机分离测风独立变桨控制策略

在基于叶片根部载荷的PID独立变桨控制的基础上,引入激光雷达并提出优化的独立变桨控制方法.利用激光雷达可重建风力机前方风场信息的特点,对风力机前方风速进行提前测量.提出并使用统一风演化模型对所测数据进行二次处理,得到更贴近实际的叶轮中心风速,进一步使用所提出的分离测风方法对叶根载荷进行提前计算,根据载荷的计算值进行独立...     

风力机尾流对风轮气动载荷影响的研究

为研究风电机组尾流对下游风电机组载荷的影响,根据已有的理论研究结果,假设几个重要尾流参数:上下游风电机组间距、上游风电机组推力系数、自然风速等。采用GH Bladed软件,在FL1500/70双馈式兆瓦风电机组上建模,并进行尾流计算。使用Matlab软件,对计算结果数据进行频谱图生成,用Bladed对计算结果进行后处理。所得结论为:机组间距减小,载荷稳定性降低,极限载荷增大;推力系数增大,载荷稳定性降低,极限载荷增大,但一般低于无尾流情况;自然风速增大,载荷主频增大且趋于0.3 Hz,载荷稳定性提高,载荷对其他参数的变化的敏感度上升。通过仿真分析,给出降低风电机组尾流影响的建议。     

1.5MW风力机叶片变形的分析

影响风力机叶片变形的载荷源主要是空气动力载荷、离心力载荷以及重力载荷.讨论了一种风力机叶片变形的计算方法,首先将叶片简化为悬臂梁进行初步分析并得出剪力和弯矩,然后进一步将悬臂梁离散化,通过对离散化节点的分析得出叶片各截面的变形.静载实验针对某1.5MW叶片的六个截面展开,测试了某叶片模型在其设计风速时各剖面的变形量.通过实验验证了文中计算方法的可靠性,并对实验和计算结果进行对比分析.     

基于粒子群优化的无载荷传感器风电机组独立变桨距控制

提出一种利用预测载荷进行独立变桨距控制的方法,应用叶素理论进行载荷预测,对测量风速以及受风剪效应和塔影效应影响的轮毂风速进行修正,使载荷计算更加准确;应用粒子群算法进行桨距角优化控制,优化搜索中通过对目标函数的选取和相关参数的设定保证控制的实时性.应用Bladed软件对某1.5MW变桨距风电机组进行仿真.结果表明:所提出的独立变桨距控制方法可在保证功率控制的同时实现载荷控制,能有效减小风轮不均衡载荷,降低机组疲劳载荷.     

MW级变桨距风电机组叶片转矩计算与特性分析

以叶素-动量理论及其修正方法为理论基础,以某MW级水平轴式风电机组为研究对象,建立MW级风电机组叶片转矩特性数学模型,对计算算法进行了分析与讨论.获得了来流风速切变条件下,诱导因子变化规律以及叶片载荷、叶轮转矩、机械功率、风能利用系数等计算结果,与风电机组实际状况基本吻合.计算结果表明,单个叶片承受周期性交变载荷,而风轮合转矩波动量较小,在满足风电机组功率稳定输出性能指标的同时,期望改善叶片载荷状况,延长其寿命,应采用独立变桨技术.     

独立变桨控制下的风力机齿轮箱动力学仿真分析

针对大型风电机组齿轮箱动态载荷问题,以多体动力学理论为基础建立风力机齿轮箱动力学模型,研究系统的独立变桨控制技术,提出线性二次高斯控制(LQG)独立变桨控制策略,建立LQG控制器,利用SIMPACK软件与Matlab/Simulink进行联合仿真,计算在仿真风速下的风力机齿轮箱载荷变化情况,计算并比较在不同风速、不同控制方式下风力机齿轮箱齿轮和轴承所受的动态载荷。计算结果表明,相对于统一变桨,独立变桨控制能更好地降低齿轮箱内部载荷波动,从而降低风力机齿轮箱齿轮和轴承的疲劳载荷。     

不同类型漂浮式风电场内机组塔基载荷研究

构建基于NREL 5 MW 风电机组的海上固定式风电场和不同类型的漂浮式风电场,考虑不同类型风电机组尾流特性、平台漂浮特性的差异,在不同工况下对风电场内机组动力学响应进行仿真计算。通过时域分析与箱线图分析,对风电场内各位置处机组在风、浪、尾流联合作用下的塔基载荷进行对比研究。结果表明：在相同工况下,Spar式风电场内机组风轮与平台位移值、塔基载荷在来流方向上最大;在中低风速下,风电场内机组塔基载荷相差较大;高风速时,塔基载荷相近;随着风速的增大,漂浮式机组塔基载荷呈先增大后减小的规律。     

低速冲击载荷下的风电叶片刚度退化规律

该文主要研究低速冲击载荷下叶片的刚度退化规律.首先用相邻2个时段风速的线性增量来定义风速突变量并获得低速冲击载荷,然后通过实验获得低速冲击载荷下的损伤规律,最后基于实测风速对疲劳试验结果进行修正,并对服役1年内的叶片刚度退化量进行分析并与实测记录进行对比.结果表明:考虑低速冲击损伤时,疲劳试验结果更准确且在役叶片刚度退...     

基于可靠性指标LOLP的风电场容量可信度的研究

介绍了基于可靠性指标LOLP的风电场容量可信度计算方法,同时给出了用于风电场可靠性计算的两种模型———发电机模型和负的负荷模型。利用不同的模型,结合实际算例,得出了一系列的计算结果,并对可能影响风电场容量可信度的一些相关因素作了灵敏度分析。     

Contributions to wind farm power estimation considering wind direction‐dependent wake effects

This paper presents a contribution to wind farm ouput power estimation. The calculation for a single wind turbine involves the use of the power coefficient or, more directly, the power curve data sheet. Thus, if the wind speed value is given, a simple calculation or search in the data sheet will provide the generated power as a result. However, a wind farm generally comprises more than one wind turbine, which means the estimation of power generated by the wind farm as a function of the wind speed is a more complex process that depends on several factors, including the important issue of wind direction. While the concept of a wind turbine power curve for a single wind turbine is clear, it is more subject to discussion when applied to a whole wind farm. This paper provides a simplified method for the estimation of wind farm power, based on the use of an equivalent wake effect coefficient. Copyright © 2016 John Wiley & Sons, Ltd.     

State‐space representation of the wind flow model in wind farms

A dynamic model for the wind flow in wind farms is developed in this paper. The model is based on the spatial discretization of the linearized Navier–Stokes equation combined with the vortex cylinder theory. The spatial discretization of the model is performed using the finite difference method, which provides the state‐space form of the dynamic wind farm model. The model provides an approximation of the behavior of the flow in the wind farm and obtains the wind speed in the vicinity of each wind turbine. Afterwards, the model is validated using measurement data of Energy research Center of the Netherlands’ Wind turbine Test site in Wieringermeer in the Netherlands and by employing the outcomes of two other wind flow models. The end goal of this work is to present the wind farm flow model by ordinary differential equations, to be applied in wind farm control algorithms along with load and power optimizations. Copyright © 2013 John Wiley & Sons, Ltd.     

Field test validation of Flex5, MSC.Adams,alaska/Wind and SIMPACK for load calculations on wind turbines

Load calculation is a very important part in the development of wind turbines. Prototype testing over the whole product life cycle is not possible. Accurate load calculations are necessary to ensure that the wind turbine withstands the loads during the expected lifetime. During the last 20years, Flex5 developed at the Danish Technical University has been used as standard tool for load calculation. Ongoing development leads to a more detailed simulation of wind turbines. A lot of general purpose multibody programs are available providing packages for load calculation of wind turbines. Within this contribution, the multibody codes Flex5, MSC.Adams, alaska/Wind and SIMPACK are compared with measurements on a prototype of a 2.05MW wind turbine developed by W2E Wind to Energy. The aim of this work is not to set one simulation package as reference but to validate all simulation packages by measurements on a physical wind turbine. A statistical and dynamical evaluation of simulation results and measurements by means of maximum, minimum, mean value, standard deviation and rainflow matrix has been performed to compare the simulation packages. The comparison of the values of wind turbine behaviour such as generated electrical power or rotor speed shows a good agreement between simulations and measurements. This could be expected because of the use of the same controller software as used on the physical wind turbine. Considering the interface loads of the wind turbine, differences occur between the simulation packages caused by different kinds of modelling. Copyright © 2015 John Wiley & Sons, Ltd.     

Model of wind shear conditional on turbulence and its impact on wind turbine loads

We analyse high‐frequency wind velocity measurements from two test stations over a period of several years and at heights ranging from 60 to 200 m, with the objective to validate wind shear predictions as used in load simulations for wind turbine design. A validated wind shear model is thereby proposed for flat terrain and that can significantly decrease the uncertainty associated with fatigue load predictions for wind turbines with large rotors. An essential contribution is the conditioning of wind shear on the 90% quantile of wind turbulence, such that the appropriate magnitude of the design fatigue load is achieved. The proposed wind shear model based on the wind measurements is thereby probabilistic in definition, with shear jointly distributed with wind turbulence. A simplified model for the wind shear exponent is further derived from the full stochastic model. The fatigue loads over different turbine components are evaluated under the full wind measurements, using the developed wind shear model and with standard wind conditions prescribed in the IEC 61400‐1 ed. 3. The results display the effect of the Wöhler exponent and reveal that under moderate turbulence, the effect of wind shear is most pronounced on the blade flap loads. It is further shown that under moderate wind turbulence, the wind shear exponents may be over‐specified in the design standards, and a reduction of wind shear exponent based on the present measurements can contribute to reduced fatigue damage equivalent loads on turbine blades. Although the influence of wind shear on extreme loads was found to be negligible, the IEC 61400‐1 wind shear definition was found to result in non‐conservative estimates of the 50 year extreme blade deflection toward the tower, especially under extreme turbulence conditions. Copyright © 2014 John Wiley & Sons, Ltd.     

大型风力发电机组塔架顶端的水平位移的计算

计算大型风力发电机组的整体稳定性和动态特性的关键是要计算出机组顶端的水平位移,由于大型风力发电机组结构通常比较复杂,塔架均采用变截面形式,各截面的刚度并非常数,因此使计算过程变得复杂、繁琐,以变截面塔架结构为例,根据刚度相等的条件,推导出变截面塔架结构在横向力、弯矩及均布载荷作用下对应的当量惯性矩的计算公式,从而可简便地求出其顶端的水平位移。     

风切变和塔影效应对风力机变桨距控制的影响分析

随着单台风力机功率的不断增大,变桨距控制对于风力机起动、制动性能的改善和对输出功率的稳定作用不断显现。单台风力机功率的不断增大也导致了塔架的增高和风轮直径的增大,风切变和塔影效应对风轮旋转平面风速分布产生的差异也不断变大。为了验证风速差异对变桨距控制的影响,建立了考虑风切变、塔影效应的风速模型以及基于叶素理论的风力机模型。采用1.5 MW风力机的数据进行研究,仿真验证表明,在集中变桨时,即使参考风速稳定,风速分布的差异也会使实际的风轮输出转矩产生脉动,桨距角产生周期性脉动,从而导致输出功率产生脉动,影响电能质量,同时叶片上产生不平衡的弯矩,增加了叶片的疲劳载荷,缩短了叶片的寿命。大型风力机应采用独立变桨技术来解决这些问题。     

不同海况及伺服系统作用下10 MW单桩式风力机地震易损性研究

为探究不同海况及伺服系统下单桩式近海风力机的地震易损性,以DTU 10 MW风力机为研究对象,建立风浪相关的地震-湍流风-波浪多物理场模型,研究其在变速变桨伺服系统下的动力特性,基于增量动力分析方法评估其地震易损性。结果表明：变速变桨伺服系统可有效缓解风力机高风速下无地震作用时的塔顶振动;当风轮在大推力下,较小的波浪载荷一定程度上可降低风力机塔顶振动及塔底弯矩;随地震动强度增加,风力机各临界损伤状态失效概率逐渐增加;风力机地震易损性主要由地震动强度决定,波浪载荷与湍流风载荷对风力机地震易损性影响较小。     

Predictive control of an experimental wind turbine using preview wind speed measurements

The development of a more reliable method of measuring the wind field upstream of a turbine (light detection and ranging) has enabled the implementation of feedforward‐related control strategies to enhance the control performance of wind turbines. By incorporating wind speed measurements, the controller is able to anticipate upon future events and thereby improve structural load mitigation and power regulation of the wind turbine. This work aims to experimentally verify the benefits of using predictive and feedforward‐based control strategies over industry standard control solutions. To achieve this, both a feedforward and a model predictive control strategy are presented, which have been validated on an experimental wind turbine in a wind tunnel. Both the model predictive controller and feedforward algorithm have shown superior performance over a baseline controller in terms of rotor speed regulation under wind speed disturbances. The experiment confirmed that a phase advantage in the control input of the predictive controller led to this performance increase. It has also been found that knowledge of just the current wind speed can already significantly increase the control performance. Copyright © 2014 John Wiley & Sons, Ltd.