变风载下风力发电机齿轮传动系统动力学特性研究

根据风力发电机齿轮传动系统所处的由随机风速引起的复杂变工况环境,用自回归AR风速模型模拟实际风场的风速,获得了由随机风速引起的时变风载荷;采用集中质量参数法建立了传动系统的纯扭转动力学模型,求得了系统的固有频率和阵型;研究了传动系统在时变风载下的动态特性,求得了各齿轮的振动位移和各齿轮副的动态啮合力,为风力发电机传动系统的动态性能优化和可靠性设计奠定了基础。     

不同工况下风力发电机传动系统动态外载荷计算

综合考虑风轮非定常气动载荷计算模型、传动系统动力学模型、双馈发电机模型和变速变桨距控制模型,建立风力发电机传动系统在不同工况下的动态外载荷计算模型。使用所建立的计算模型对变速变桨距型风力发电机分别在启动、运行和制动时的外载荷进行计算分析,得到增速齿轮箱的输入载荷变化规律及其影响因素。     

变桨距风力发电机额定风速的确定方法

根据风速的Weibull分布特性和变桨距风力发电机的发电特性,构建不同额定风速下风力发电机年发电量计算方法.应用美国可再生能源实验室(NREL)对风力发电成本的研究成果,建立了变桨距风力发电机发电的度电成本数学模型,提出了以度电成本最低为目标的额定风速确定方法,为变桨距风力发电机的额定风速最优选择提供了计算依据.     

风力发电机机舱底座模态及动态载荷分析

风力发电机机舱底座是机舱内最重要的承重部件,承受载荷情况复杂。利用有限元分析软件Samcef field对1.5 MW机舱底座进行了模态分析,提取了前5阶固有频率和前3阶振型。基于Samcef for Wind Turbine(SWT)软件,应用梁单元和超单元进行了高精度风机建模,分析了机舱底座上承受的主要动态载荷,并再次应用有限元方法分析了动态载荷作用下底座上的应力分布和变形。建模和分析方法具有一定的普适性,能够对复杂构件动态载荷进行快速分析。     

1.5MW低风速风力发电机组主传动系统设计及动力学分析

低风速风力发电机组具有广阔的市场前景,其主传动系统的设计和分析是整个风机研发的关键技术之一。通过对风机各种传动系统结构形式的分析、对比和优化,设计了适于1.5 MW低风速风力发电机组的最佳传动方案,即内置式主轴、二级行星加一级平行轴齿轮传动的结构形式。采用多体动力学软件SIMPACK建立了该风机主传动系统的精确模型,找出系统的固有频率及激振源,并进行共振分析;对共振危险点进行时域仿真,根据仿真结果研究振动对风机系统的影响。最后根据系统的动态特性分析结果,验证所设计的主传动系统的可靠性。     

低风速风力发电机轮毂强度与疲劳寿命分析

利用ANSYS有限元软件,对正常运行工况和危险工况下的低风速风力发电机轮毂进行了有限元分析,得到了轮毂的应力分布状况。利用ANSYS的Fatigue模块对轮毂进行了疲劳寿命计算,并进行了强度校核,危险工况下的应力分析表明,轮毂满足强度的要求,安全系数为2.1,轮毂的疲劳寿命为8.8 a。     

英国流行家用风力发电机

目前在英国，家用小型风力发电机已经非常普遍，各大建材商店都有售。而且英国保守党领袖戴维·卡梅伦也宣称要在他家房顶上装一台，成为该技术最有力的支持者。家用风力发电机的工作原理与大型风力发电机一样，只是发电功率较小。一台家用风力发电机一年能够发电约1000kWh，在地形条件好的地方能发电1500kWh。这能够满足普通家庭所需电量的三分之一。风力发电的电量与风速有关，所以一个地区的平均风速是重要因素。     

大型失速型风力发电机动态特性研究

通过分析主动失速型机组的来流风速、气动、机械传动与发电机等部件的机理,建立了机组各主要部件的子系统模型(如气动模型、传动模型、发电机暂态模型、补偿电容模型、电网模型和控制系统模型等),近而得到了全系统的动态非线性模型。通过对机组全系统动态机理模型的数字仿真,得到机组在特定来流工况条件下的动态特性。所建立的模型和仿真结果为今后研究风电场与电网之间的相互影响提供了理论基础。     

单片机直接数字测速在风力发电机中的应用

为使风力发电机安全运行，对风速、叶轮转速和发电机转速测量的准确性和实时性有比较严格的要求。本文阐述了用８０３２单片机实现的适用于风力机控制的实用测速方法。     

可扩展工作风速范围的风力发电机

针对现有小型风力发电机的有效发电时长短、可利用风速范围小的问题,提出一种可扩展工作风速范围的风力发电机.此风力发电机采用下风式结构辅以导流机舱罩聚风,轮毂与发电机轴采用发条柔性连接,风轮锥角可调.基于以上结构设计,实现降低切入风速提高切出风速,从而延长发电时间,提高风能利用率和设备利用率,增加发电量.文中以型号为FD2.2-300W小型风力发电机为例,进行技术参数的计算和对比,得出切出风速由20m/s提高到22m/s.该装置可作为现有小型风力发电机的升级替代产品.     

Atmospheric turbulence and its influence on the alternating loads on wind turbines

Analysis of measurements on atmospheric turbulence with respect to the statistics of velocity increments reveals that the statistics are not Gaussian but highly intermittent. Here, we demonstrate that the higher quantity of extreme events in atmospheric wind fields transfers to alternating loads on the airfoil and on the main shaft in the form of torque fluctuations. For this purpose, alternating loads are discussed with respect to their increment statistics. Our conjecture is that the anomalous wind statistics are responsible for load changes, which may potentially contribute to additional loads and may cause additional fatigue. Our analysis is performed on three different wind field data sets: measured fields, data generated by a standard wind field model and data generated by an alternative model based on continuous time random walks, which grasps the intermittent structure of atmospheric turbulence in a better way. Our findings suggest that fluctuations in the loads might not be reflected properly by the standard wind field models. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamic models of wind farms with fixed speed wind turbines

The increasing wind power penetration on power systems requires the development of adequate wind farms models for representing the dynamic behaviour of wind farms on power systems. The behaviour of a wind farm can be represented by a detailed model including the modelling of all wind turbines and the wind farm electrical network. But this detailed model presents a high order model if a wind farm with high number of wind turbines is modelled and therefore the simulation time is long. The development of equivalent wind farm models enables the model order and the computation time to be reduced when the impact of wind farms on power systems is studied. In this paper, equivalent models of wind farms with fixed speed wind turbines are proposed by aggregating wind turbines into an equivalent wind turbine that operates on an equivalent wind farm electrical network. Two equivalent wind turbines have been developed: one for aggregated wind turbines with similar winds, and another for aggregated wind turbines under any incoming wind, even with different incoming winds.The proposed equivalent models provide high accuracy for representing the dynamic response of wind farm on power system simulations with an important reduction of model order and simulation time compare to that of the complete wind farm modelled by the detailed model.     

Evaluation of internal force superposition on a TLP for wind turbines

The offshore wind resources globally present a great opportunity for green power generation. Both types, fixed and floating foundations, will play a major role in utilizing these resources. The preliminary design of the floating system called GICON^®-Tension Leg Platform (TLP) is meant to provide a solution for harnessing the power of offshore wind at water depths between 20 m and 350 m. In addition a design for water depth up to 700 m is currently under development. The research project is a joint development of private industry and academic institutions. The main partners are ESG GmbH and Technische Universität Freiberg. Currently ongoing research includes the comparison of calculated data with experimental data obtained by wave tank experiments with a scale model at the Maritime Research Institute Netherlands (MARIN) in June 2013. These tests have provided insights regarding the dynamic characteristics of the GICON^®-TLP by analyzing the system's response to different load cases. Furthermore, the results of the scale model tests at MARIN have confirmed that a superposition of the internal forces for wind and wave loads can be assumed for the structural design. This can be traced back to the stiffness of the mooring line system and the innovative mooring line configuration.     

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.     

考虑塔架和叶片动力耦合的随机风载下风机结构动响应分析

考虑叶片和塔架的动力耦合作用,建立了5 MW风机整体结构的有限元模型,计算其在随机风速下的动响应。为分析叶片和塔架的动力耦合对风机结构动响应的影响,计算比较了刚性支撑的叶片、简化的风机和整体风机3种模型在风载下的动响应位移和应力。计算结果表明:由于叶片和塔架的耦合作用,叶片的位移响应最大增加约20%,但是塔架的位移响应最大降低了约60%。文章还分析了叶片旋转过程中方位角对塔架位移响应的影响。在叶片的一个旋转周期内,塔架的响应幅值会有较大的波动,最大响应幅值约为最小响应幅值的3倍。     

Aerodynamic optimization of shrouded wind turbines

An axisymmetric Reynolds averaged Navier–Stokes solver is used along with an actuator disk model for the analysis of shrouded wind turbine flowfields. Following this, an efficient blade design technique that maximizes sectional power production is developed. These two techniques are incorporated into an optimization framework that seeks to design the geometry of the shroud and rotor to extract maximum power under thrust constraints. The optimal solution is also evaluated using a full three‐dimensional Reynolds averaged Navier–Stokes solver, suggesting the viability of the design. The predicted optimal designs yield power augmentations well in excess of the Betz limit, even if the normalization of the power coefficient is performed with respect to the maximum shroud area. Copyright © 2016 John Wiley & Sons, Ltd.     

Service reliability of offshore wind turbines

A probabilistic formulation is proposed to assess the performance of the support structure of offshore wind turbines based on their probability and expected time of exceeding specified drift thresholds. To this end, novel probabilistic models are developed to predict the mean and standard deviation of the drift ratio response of wind turbine support structures operating under day-to-day loads as a function of the wind turbine geometry and material properties, and loading conditions. The proposed models are assessed using a database of virtual experiments generated using detailed three-dimensional (3D) nonlinear finite element (FE) models of a set of representative wind turbine configurations. The developed models are then used in a random vibration formulation to estimate the probability and expected time of exceeding specified drift thresholds. As an example, the probability and expected time of exceeding specified drift thresholds are estimated for a typical offshore wind turbine at different wind speeds. A comparison is made between the results obtained based on the proposed models, those obtained using simulators commonly used in practice and detailed 3D nonlinear FE analyses.     

Sustainability assessment of wind turbines using fuzzy logic

Renewable energy systems provide opportunities for developing methods to evaluate their sustainability claims, inclusive of their life cycles, and to rank them based on their broader impact. In this paper, a fuzzy-logic-based method is proposed to evaluate and rank wind turbines as sustainable systems handling wind energy, in terms of renewability and environmental friendliness. Implementation of the proposed method is demonstrated in two steps: First, major factors defining life cycle and sustainability characteristics of wind turbines are identified. These factors are: Capital Cost, Greenhouse Gas Emission, and wind turbine Energy Efficiency. Nevertheless, the method allows expansion to include other factors, which may later be deemed as critical to the evaluation process. Second, a fuzzy-logic-based model is built and tested using hypothetical data to prove the concept. As a result, the relatively best sustainability is decided on a single dimension scale. The proposed method produced reliable results in terms of ordinally ranking the sustainability of wind turbines, but with interdependencies based on the entire group of wind turbine cases being examined. The proposed method formulates a satisfactory stepping stone on the way to establish a unified method and process to rank wind turbines based on sustainability.     

Unbalanced voltage faults: the impact on structural loads of doubly fed asynchronous generator wind turbines

This paper investigates the impact that unbalanced voltage faults have on wind turbine structural loads. In such cases, electromagnetic torque oscillations occur at two times the supply voltage frequency. The objectives of this work are to quantify wind turbine structural loads induced by unbalanced voltage faults relative to those during normal operation; and to evaluate the potential for reducing structural loads with the control of the generator. The method applied is integrated dynamic analysis. Namely, dynamic analysis with models that consider the most important aeroelastic, electrical, and control dynamics in an integrated simulation environment based on an aeroelastic code (HAWC2) and software for control design (Matlab/Simulink). In the present analysis, 1 Hz equivalent loads are used to compare fatigue loads, whereas maximum–minimum values are used to compare extreme loads. A control concept based on resonant filters demonstrates reduction of the structural loads (shaft torsion and tower top side‐to‐side moment) induced by an unbalanced voltage fault.Copyright © 2013 John Wiley & Sons, Ltd.