三浮体式海上风电基础结构响应研究

采用SESAM软件包对一种三浮桶式海上风电基础结构进行了运动响应计算。采用GeniE模块建立了该三浮桶海上风电基础结构的结构模型和水动力模型,并在HydroD模块中进行了组合载荷以及运动响应的计算,对其水动力特性进行了分析。在其中的波浪载荷计算过程中,采用基于三维水动力理论的设计波方法。     

导管架式一体化风机在冰载荷作用下的耦合响应研究

海上风电是世界上发展最快的可再生能源之一.寒区蕴藏着丰富的风能资源,设计和建造用于结冰海域的风电结构的关键要求是其应具备一定的抗冰性能.本文研究了全耦合导管架式海上风力发电机在冰载荷作用下的结构动态响应;在数值仿真软件FAST中建立了一体化风机数值模型,该模型包含其空气动力属性、水动力属性、机械属性和结构弹性属性;研究了导管架风机基础的直立桩腿和加装了抗冰锥体后的桩腿的抗冰性能差异;并计算分析了不同冰厚和冰速对于风机动态响应的影响.结果表明:海冰厚度越大,导管架底座的结构响应和振荡幅度越大;海冰速度越大,其结构响应和振荡频率越快;导管架桩腿在安装抗冰锥体后的结构响应和振荡幅度明显降低.本文还计算分析得到了抗冰性能最佳的锥体角度.     

大型海上风电机组扭振瞬态响应计算研究

针对波动性的空气扭转载荷会严重影响风电机组传动系统中关键部件使用寿命的问题,以某5MW海上直驱型风电机组传动系统为研究对象,建立了模拟真实风的风剪切、塔影效应、湍流效应的气动载荷模型,归纳了风电机组扭振分析的计算流程,结合简化的风电机组双质量模型得到了传动系统在不同风载荷模型作用下的瞬态扭振响应特性。结果表明:风剪切—塔影效应对于风电机组的瞬态扭振响应影响较小,而湍流风效应对风电机组的扭振响应较大。     

海上风电机组齿轮箱进口油温异常预测

由于海上风电机组齿轮箱要长期承受无规律的变向变载荷的风力作用以及强阵风的冲击,为保证风电机组可靠运行,对齿轮箱进口油温进行异常预测。结合风电机组SCADA运行数据提出了一种基于SVM-RFECV算法和BP神经网络的风电机组齿轮箱进口油温异常预测方法。首先完成数据的预处理,然后利用SVM-RFECV算法计算不同变量的重要度,并选择平均交叉验证均方误差的最小变量组成最优特征,最后利用选取的最优特征数据建立的BP神经网络的预测模型,实现对风电机组齿轮箱进口油温异常预警。通过海上某风电场现场实际SCADA数据对模型进行验证,结果表明提出的方法能有效实现对风电机组齿轮箱进口油温异常预测。     

海上风电系统地基刚度敏感性分析

文章基于Bladed软件建立了包括海上风电机组-支撑结构-地基基础的一体化结构模型，以某5 MW机组的单桩基础为例，对海上风电机组系统进行了一体化荷载计算，并系统地开展了地基刚度敏感性分析。计算结果表明：结构自振频率随着地基刚度的提高而增大，且在无波浪作用时，结构在泥面处的荷载呈现随地基刚度增大而减小的趋势；当有波浪作用时，结构在泥面处的荷载受到风、波浪作用的综合影响，当波浪频率接近基频时，结构所受荷载显著增大。因此，设计时应充分考虑地基刚度取值准确性问题。     

大型海上风电机组整机涡激仿真

随着海上风电机组朝着大型化发展,塔筒高度和叶片长度都显著增加,并且海洋风比陆地风的湍流度更小,这些因素使得大型海上风电机组在吊装或停机状态下频繁出现涡激振动现象。涡激振动增大了风电机组发生强度失效以及疲劳寿命降低的风险。为研究大型海上风电机组整机涡激振动的机理,文章采用仿真方法对某大型海上机组实际发生的涡激振动现象进行复现和分析：首先对风电机组进行流场分析,然后提取流场分析得到的时序载荷,施加到风电机组有限元模型上,进行瞬态分析,从而实现流固耦合仿真。仿真结果表明：风电机组的涡激振动是一种流固耦合现象,主要原因是,在特定风况条件下,气流在塔筒和叶片的壁面处形成周期性脱落的漩涡,对壁面产生周期性的反向载荷。当载荷频率与机组振动的固有频率接近时,使机组发生共振。文章通过仿真方法揭示了大型海上风电机组发生涡激振动的机理,对提出风电机组涡激振动防治策略具有参考意义。     

后市场更换叶片对机组载荷及发电性能的影响

为发掘现役风电场的风电潜能,提升整场的发电量,降低风力发电机全生命周期的每度电成本。选取某风场安装单机容量为2 MW机组作为研究对象,对其进行了后市场叶片增长仿真分析。通过Bladed软件对改造风电机组开展了数值仿真,简要的分析了风机发电量和整机载荷的变化情况,论证了该方案的可行性和工程意义,为陆上及海上固定式风电机组后市场更换叶片方案提供参考。     

海上风机支撑结构的时域和频域疲劳对比研究

对海上风机支撑结构进行动力响应分析,求出结构危险节点的载荷谱和功率谱密度函数,结合疲劳损伤模型和Dirlik概率模型,分别在时域和频域内对支撑结构进行疲劳寿命分析。由于时域法计算疲劳寿命需进行应力循环计数,这一过程需处理的数据庞大,耗时长。频域法省去应力循环计数,代之以概率密度函数,可相对准确、快速地计算结构的疲劳寿命。分析结果表明,采用Dirlik概率模型的频域分析法能较准确地反映海上风机支撑结构在随机载荷作用下的疲劳损伤情况,计算结果误差在可接受范围内。     

海上风机支撑结构的时域和频域疲劳对比研究

对海上风机支撑结构进行动力响应分析,求出结构危险节点的载荷谱和功率谱密度函数,结合疲劳损伤模型和Dirlik概率模型,分别在时域和频域内对支撑结构进行疲劳寿命分析.由于时域法计算疲劳寿命需进行应力循环计数,这一过程需处理的数据庞大,耗时长.频域法省去应力循环计数,代之以概率密度函数,可相对准确、快速地计算结构的疲劳寿命.分析结果表明,采用Dirlik概率模型的频域分析法能较准确地反映海上风机支撑结构在随机载荷作用下的疲劳损伤情况,计算结果误差在可接受范围内.     

绞车轴瓦应力对附加载荷的响应机理分析

自升式风电安装船是海洋风电安装工程中的重要装备,摩擦绞车升降装置与桩腿、船体构成了自升安装船独立的升降系统。在升降装置的作用下,绞车提供牵引力完成放桩、升船等动作。海上作业过程中环境载荷的不确定性会使作业过程绞车升降系统受附加工作载荷,从而导致工作绞车容易发生故障,给作业系统的安全、稳定运行带来巨大的隐患。本课题从海洋38#风电安装船的外部作用环境和实船绞车轴瓦的失效情况出发,基于支撑桩腿、船体与海洋环境间的相互作用机理,分别分析了绞车轴瓦应力对冲击和振动的响应关系,并采用柔性体有限元仿真和刚体动力学仿真分析的方法,分析了绞车作业过程中的附加工作载荷。同时根据分析结果绘制了响应关系坐标图,进一步研究了工作过程中绞车附加载荷与绞车滚筒支撑轴瓦失效的机理关系。     

海上风力发电浮式基础的研究进展及关键技术问题

水深大于50m的海域,风速稳定、风切变小,具有风力发电的独特优势,该海域风力发电装备需要采用浮式基础,因此研究适用于海上风力发电的浮式基础结构,对海上风力发电的产业化具有重要的意义。近年来国外开展了各种新颖浮式基础结构基础形式和工作原理的研究,针对浮式基础承受的风机运转载荷和海洋环境载荷的特点,系统分析海上风机浮式基础涉及到的关键技术问题和风险因素,对风机浮式基础设计具有参考价值。     

冰区海上风电基础的抗冰性能分析

海上风电基础属于典型的柔性结构。由于冰与柔性抗冰结构相互作用的复杂性,长期以来尚未形成基于动冰力响应分析的结构设计。结构抗冰设计中大都是从极端荷载出发,只考虑最大静冰力或最大倾覆力矩。基于对渤海辽东湾柔性抗冰结构的多年监测,发现强烈的冰激振动引起柔性结构的风险性要远大于极端静冰荷载下结构的整体安全问题。为了明确冰区风电基础结构的抗冰性能及抗冰设计的合理性,文章结合基于多年现场冰与结构作用观测及冰荷载的研究成果,明确该类柔性结构与海冰作用形式及其动力特性;提出了柔性抗冰结构设计中应考虑的主要失效模式及评价方法。最后,以渤海某典型风电基础为例,对其抗冰性能进行评价。该文的研究可为寒区风电基础的抗冰设计及安全保障提供合理依据。     

半潜型浮式风机运动特征及系泊系统的研究

近年来海上浮式风机的研究备受关注,安全可靠的系泊系统将保证风机在风、浪、流等复杂环境荷载作用下稳定运行,准确合理地描述风机运动将为评估风机发电效率提供支持。以半潜型浮式风机的系泊系统为研究对象,基于经典悬链线理论,采用准静态分析法提出一套系泊系统的设计方法。通过坐标变换,得到风轮真实的俯仰运动用于计算风机的动力效应及评定其发电效率。采用动力法分析了系泊系统锚链的导缆孔位置、预张力大小、锚链间夹角等参数对风机系统发电效率、浮式平台运动性能和系泊锚链张力的影响,得到了浮式平台迎风面俯仰倾角、水平偏移及锚链张力随参数的变化规律,为半潜型浮式风机系泊系统的设计提供了参考。     

半潜浮式风机的动力响应分析

OC4半潜浮式风机综合性能较好，但其浮式基础结构质量和结构复杂性使其建造成本高昂，而WindFloat半潜浮式风机浮式基础具有结构简单、建造成本低和减摇效果好等优点，但是适应水深较小且只适合特定海域。结合OC4和WindFloat半潜浮式风机浮式基础的结构特点，针对200 m水深环境设计OC4-WindFloat半潜浮式风机基础。基于叶素理论、莫里森公式和势流理论，通过有限元软件对OC4-WindFloat半潜浮式风机的固有周期及风浪联合作用下的动态响应进行耦合分析，并与OC4半潜浮式风机结果进行对比研究。结果显示，OC4-WindFloat半潜浮式风机固有周期及动态响应均满足相关规定，且具有比OC4更低的建造成本，相比WindFloat可适用更深的海域。研究结果对于浮式基础型式研究有一定的指导意义。     

Dynamic ice loads for offshore wind support structure design

For offshore wind farms which are planned in sub-arctic regions like the Baltic Sea and Bohai Bay, support structure design has to account for load effects from dynamic ice-structure interaction. There is relatively high uncertainty related to dynamic ice loads as little to no load- and response data of offshore wind turbines exposed to drifting ice exists. In the present study the potential for the development of ice-induced vibrations for an offshore wind turbine on monopile foundation is experimentally investigated. The experiments aimed to reproduce at scale the interaction of an idling and operational 14 MW turbine with ice representative of 50-year return period Southern Baltic Sea conditions. A real-time hybrid test setup was used to allow the incorporation of the specific modal properties of an offshore wind turbine at the ice action point, as well as virtual wind loading. The experiments showed that all known regimes of ice-induced vibrations develop depending on the magnitude of the ice drift speed. At low speed this is intermittent crushing and at intermediate speeds is ‘frequency lock-in’ in the second global bending mode of the turbine. For high ice speeds continuous brittle crushing was found. A new finding is the development of an interaction regime with a strongly amplified non-harmonic first-mode response of the structure, combined with higher modes after moments of global ice failure. The regime develops between speeds where intermittent crushing and frequency lock-in in the second global bending mode develop. The development of this regime can be related to the specific modal properties of the wind turbine, for which the second and third global bending mode can be easily excited at the ice action point. Preliminary numerical simulations with a phenomenological ice model coupled to a full wind turbine model show that intermittent crushing and the new regime result in the largest bending moments for a large part of the support structure. Frequency lock-in and continuous brittle crushing result in significantly smaller bending moments throughout the structure.     

An object-oriented method for fully coupled analysis of floating offshore wind turbines through mapping of aerodynamic coefficients

This work presents a novel object-oriented approach to model the fully-coupled dynamic response of floating offshore wind turbines (FOWTs). The key features offered by the method are the following: 1) its structure naturally allows for easy implementation of arbitrary platform geometries and platform/rotor configurations, 2) the analysis time is significantly faster than that of standard codes and results are accurate in situations where rotor dynamic contribution is negligible, and 3) an extremely flexible modeling environment is offered by the object-oriented nature of Modelica. Moreover, the current modeling facility used for the code development is open source and is naturally suitable for code sharing. In the present method, the aerodynamic model computes the aerodynamic loads through the mapping of steady-state aerodynamic coefficients. This modeling approach can be placed at the intersection between simplified aerodynamic methods, such as TDHMill, and full beam element/momentum-based aerodynamic methods. Aerodynamic loads obtained from the coefficients mapping are composed of a concentrated thrust and a concentrated torque. The thrust acts at the hub, while the torque is applied at the rotor low-speed shaft of a simplified rigid rotor equation of motion (EoM) used to emulate the rotor response. The aerodynamic coefficients are computed in FAST for a baseline 5 MW wind turbine. A standard rotor-collective blade-pitch control model is implemented. The system is assumed to be rigid. Linear hydrodynamics is employed to compute hydrodynamic loads. The industry-standard numerical-panel code Sesam-Wadam (DNV-GL) is used to preprocess the frequency-domain hydrodynamic problem. Validation of the code considers a standard spar-buoy platform, based on the Offshore Code Comparison Collaboration (OC3-Hywind). The dynamic response is tested in terms of free-decay response, Response Amplitude Operator (RAO), and the time histories and power spectral densities (PSDs) of several load cases including irregular waves and turbulent wind. The resulting model is benchmarked against well-known code-to-code comparisons and a good agreement is obtained.     

Model test investigation of a spar floating wind turbine

Several floating wind turbine designs whose hull designs reflect those used in offshore petroleum industry have emerged as leading candidates for the future development of offshore wind farms. This article presents the research findings from a model basin test program that investigated the dynamic response of a 1:50 scale model OC3 spar floating wind turbine concept designed for a water depth of 200 m. In this study the rotor was allowed to rotate freely with the wind speed and this approach eliminated some of the undesirable effects of controlling wind turbine rotational speed that were observed in earlier studies. The quality of the wind field developed by an array of fans was investigated as to its uniformity and turbulence intensity. Additional calibration tests were performed to characterize various components that included establishing the baseline wind turbine tower frequencies, stiffness of the delta type mooring system and free decay response behaviour. The assembled system was then studied under a sequence of wind and irregular wave scenarios to reveal the nature of the coupled response behaviour. The wind loads were found to have an obvious influence on the surge, heave and pitch behaviour of the spar wind turbine system. It was observed from the experimental measurements that bending moment at the top of the support tower is dominated by the 1P oscillation component and somewhat influenced by the incoming wave. Further it was determined that the axial rotor thrust and tower-top shear force have similar dynamic characteristics both dominated by tower’s first mode of vibration under wind-only condition while dominated by the incident wave field when experiencing wind-wave loading. The tensions measured in the mooring lines resulting from either wave or wind-wave excitations were influenced by the surge/pitch and heave couplings and the wind loads were found to have a clear influence on the dynamic responses of the mooring system.     

Semi-submersible wind turbine hull shape design for a favorable system response behavior

Floating offshore wind turbines are a novel technology, which has reached, with the first wind farm in operation, an advanced state of development. The question of how floating wind systems can be optimized to operate smoothly in harsh wind and wave conditions is the subject of the present work. An integrated optimization was conducted, where the hull shape of a semi-submersible, as well as the wind turbine controller were varied with the goal of finding a cost-efficient design, which does not respond to wind and wave excitations, resulting in small structural fatigue and extreme loads.The optimum design was found to have a remarkably low tower-base fatigue load response and small rotor fore-aft amplitudes. Further investigations showed that the reason for the good dynamic behavior is a particularly favorable response to first-order wave loads: The floating wind turbine rotates in pitch-direction about a point close to the rotor hub and the rotor fore-aft motion is almost unaffected by the wave excitation. As a result, the power production and the blade loads are not influenced by the waves. A comparable effect was so far known for Tension Leg Platforms but not for semi-submersible wind turbines. The methodology builds on a low-order simulation model, coupled to a parametric panel code model, a detailed viscous drag model and an individually tuned blade pitch controller. The results are confirmed by the higher-fidelity model FAST. A new indicator to express the optimal behavior through a single design criterion has been developed.     

海上风机在三种风载荷作用下的疲劳分析方法研究

文章提出一种基于等效疲劳载荷的快速有效的结构优化设计方法,首先通过bladed模拟得到时域下的风载荷,然后通过雨流计数法则和等效损伤理论得到相应的疲劳载荷谱和等效疲劳载荷,接着以导管架式海上风机为例,利用AN-SYS对其进行三维建模,选取三种典型管节点和两种非管节点,基于热点应力法计算了其在三种风疲劳载荷作用下的疲劳损伤,通过比较三种载荷作用下的疲劳损伤结果,验证了等效疲劳载荷的可靠性.接着又计算了各等效疲劳载荷分量单独作用下的海上风机焊接节点的疲劳损伤,得出各疲劳载荷分量对疲劳总损伤的贡献,可以为设计者提供更好的载荷设计依据.相比于传统的时域疲劳分析方法和疲劳载荷谱方法,等效疲劳载荷方法更加方便有效.     

预应力混凝土风机结构在环境载荷与5兆瓦负载下的三维分析模拟（英文）

A concrete gravity base structure may not be suitable for offshore weak soil because of its heavy weight. Therefore, a conceptual model for a concrete offshore wind turbine structure suitable for weak soils is proposed. The proposed model is composed of a prestressed concrete(PSC) supported by a pile foundation. For a three-dimensional analysis of the large concrete structure, wave pressures based on the diffraction wave theory are developed using a three-dimensional solid finite element method. Static and dynamic analyses were performed to achieve the conceptual model of a PSC structure subjected to ocean environmental loads and a 5-MW turbine load on southwest coast in Korea. From the analysis, the maximum displacement and stresses of the proposed model did not exceed the allowable values from design standard, and the first mode of natural frequency of the structure was in a safe range to avoid resonance. The proposed model has enough structural stability to withstand external loads, and it is expected to be used in locations suitable for concrete gravity structures.