波浪对海上大型风力机筒形塔架的影响

文章利用梁单元对海上风力机筒形塔架进行有限元建模,并建立了塔架动力学运动方程。阐述了海上风力机塔架所受Kaimal湍流风模型和Pierson-Moskowitz波浪谱模型,并对风载荷、波浪载荷和海流载荷进行了详细分析。基于某6.0 MW海上大型风力机塔架的动力响应计算,分析了极限和疲劳工况下波浪对塔架顶端振动位移和塔底载荷的影响程度,为海上风力机筒形塔架设计提供了参考。     

水平轴风力机筒型塔架动态响应分析

为获得水平轴风力机塔架在时变载荷作用下的动态响应,将塔架简化成悬臂梁,利用二结点梁单元进行离散化建模,分析了塔架弯曲振动固有动力特性。在建立塔架结构动力学运动方程、计算塔架所受时变载荷的基础上,运用线性加速度法和模态叠加原理对风力机塔架的动态响应进行计算,编制了相应的计算机程序。以某1.0MW风力机塔架为例,获得了风力机在湍流风运行条件下塔架在仿真时间内的位移、速度和加速度,并与"GHBladed"软件的计算结果进行了比较,表明计算模型是可行的。     

大型风力机地震动力响应研究

为研究地震载荷与风载荷联合作用下的大型风力机结构动力学响应,本文研究分别以Wind PACT 1.5 MW和NREL 5 MW风力机为研究对象,采用EI Centro 6.9级地震为输入激励,通过改进版的开源软件FAST(风电载荷仿真软件)计算风力机在正常运行、紧急停机和一直停机3种运行方式下的塔顶振动和塔架结构荷载情况,结果表明:地震载荷极大加剧了塔顶振动,机舱加速度峰值增大2倍以上。紧急停机操作可减小塔尖位移,一定程度上可以保护风力机结构安全。地震载荷主要增大了塔架一阶固有频率及其二倍频的振动。6.9级地震与额定风载荷联合作用下,NREL 5MW风力机塔基弯矩设计需求为159 MN·m,略大于极限风载荷作用。说明地震常发地区,塔架结构强度设计必须考虑地震载荷作用。     

海冰作用下近海桩柱式风力机动力学响应研究

高纬度低温海域海平面存在大量运动状态的海冰,位于此处的近海桩柱式风力机容易受到不规则的海冰载荷作用,风力机平台、塔架和叶片等结构部件的动力学响应均受其影响.为定性及定量分析海冰载荷对叶片和塔架的结构动力学响应的影响程度,以NREL5 MW近海4桩柱式风力机为研究对象,耦合风载荷、波浪载荷及海冰载荷,通过Kane方法建立风力机动力学模型,其中海冰载荷通过冰力函数定义.对比分析了在IEC Lock in冰力函数、Mttnen海冰模型和无海冰作用三种工况下叶片和塔架的结构动力学响应,结果表明:海冰载荷使塔顶位移增加,在Mttnen海冰模型作用下塔顶位移增加了24.1%,在IEC Lock in模型作用下则增加了16%;两种海冰模型均不同程度地使叶片挥舞振动的频率增大,其中在Mttnen海冰模型中变化更加剧烈,这极大地增加了叶片的疲劳载荷.     

基于流固耦合的风力机塔筒动态特性分析

塔筒动态特性分析对风力发电机的振动设计起着关键作用。文章以1.5 MW风力发电机塔筒为研究对象,将叶片旋转和随机风载荷作为载荷输入条件,建立风力机塔筒叶片旋转载荷模型、流固耦合风载荷模型、结构动力学方程,分析计算得到随机载荷下叶片旋转和风载共同作用时,风力机塔筒动态特性评估方法。     

高风速及风突变对风力机柔性部件振动特性研究

风力机运行在复杂多变的自然环境之中,风是影响风力机气动特性和振动特性的最直接因素,高风速及风速突变将诱发风力机更强的气动载荷。为探究风力机柔性部件在高风速及突变湍流风作用下的振动特性,以NREL(美国国家能源部可再生能源实验室)实测数据为湍流风数据源,并添加相干结构描述风速突变,以NREL 1.5 MW近海桩柱式风力机为样机,建立基于Kane方法的风力机结构动力学模型,并使用假设模态离散化方法对其进行柔性化,而后将该模型与风场和气动力模型一起组成气-弹相互耦合系统动力学模型,分别研究了风力机叶片和塔架的结构动力学响应。结果表明:相干结构的添加可使基础湍流风具有更大的风突变以及更高的湍流强度;额定风速附近,叶尖位移体现为挥舞,切出风速附近,叶尖位移同时体现为挥舞和摆振;相干结构的添加使得叶片和塔架振动加速度成倍增加。     

异步冰载荷作用下风力机动力学响应分析

为研究与结构接触表面不平整浮冰导致的冰激振动对风力机影响,建立风力机Kane多体动力学模型,采用异步Matlock模型模拟冰激振动,由Kaimal风速谱、指数风廓线模型和空间相干模型模拟来流风场,结合叶素动力学计算风力机非定常气动载荷,分析湍流风载荷和异步冰激振动模型作用下塔架动力学响应。研究结果表明：异步Matlock模型冰载荷峰值低于同步模型;塔顶前后位移受冰激振动影响较侧向更为显著,幅值和标准差均大幅提高;冰激振动导致塔顶前后位置破碎频率及其靠近叶片2阶挥舞频率倍频处幅值大幅提高,且异步Matlock增幅小于同步模型;异步Matlock模型对塔顶侧向位移影响较小。     

风波联合作用下的风力机塔架疲劳特性分析

研究了海上风力机圆筒型塔架在随机风载荷和波浪载荷作用下的动力响应数值分析方法;建立了基于Palmgren Miner线性累积损伤法则的混泥土塔架安全寿命估计方法.应用线性波理论仿真非规则的海浪,分析作用在圆筒型塔架上的波浪载荷.通过坐标变换,将二维线性波理论扩展为三维线性波理论,建立了波浪力的分析计算模型;用有限元数值分析方法,求解了塔架在风波联合作用下的位移、速度、加速度以及应力响应等;用雨流计数法统计循环参量,将工作循环应力水平等寿命转换成对称循环下疲劳载荷谱,分析了变幅载荷谱下塔架的疲劳损伤及疲劳寿命.算例表明:该文的工作为海上风力机系统气动弹性分析、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.     

地震及湍流风联合作用下的大型海上风力机结构动力学响应

为研究DTU 10MW近海桩柱式风力机塔架在地震激励下的动力学响应,基于p-y曲线法建立单桩基础与土壤的耦合模型,通过有限元软件ANSYS建立风力机塔架的有限元模型,分析不同速度湍流风和不同强度地震时塔架的瞬态动力学响应。结果表明:仅风载荷作用时,额定风速作用下塔架动力学响应明显高于切出风速;地震与风联合作用时,塔顶位移动态响应剧烈,但无明显规律;塔架加速度响应最大值位置约为四分之三塔高处,塔顶剪应力响应与地震持续时间有关。     

基于ABAQUS地震激励下风力机结构损伤分析

高耸的风力机塔架结构属于典型的顶部附有大集中质量的细长柔性体的力学结构,相比传统建筑结构差异性较大,极易受到地震载荷影响。基于有限元分析软件ABAQUS建立风力机塔架、基础平台和土体模型,通过FAST导出风轮非定常推力,作用在塔顶机舱,土体底部施加地震加速度时间序列,进行风力机结构模态分析、稳定性分析和动力学响应分析。研究表明：塔架主要的运动形式为摇摆运动和弯曲振动;塔架一阶固有频率为0.290 Hz,大于风轮的额定旋转频率0.202 Hz,因此叶片旋转不会引起风力机塔架发生共振;风载荷作用下,塔架发生横向屈曲,屈曲位置位于塔架底部且随模态阶数增大而逐渐向上发展,屈曲因子较大;地震载荷作用下,塔架发生纵向屈曲,屈曲位置同样位于塔架底部且随模态阶数增大而逐渐向上发展,较风载荷发生屈曲区域相对更大,屈曲因子相对较小。     

Hybrid wind/PV/diesel system experiences

The past ten years have seen significant developments in the design, analysis and installation of hybrid (wind/PV/diesel) power systems. This paper presents a summary of recent progress on this subject in the United States with emphasis on the analytical and experimental work carried out at the University of Massachusetts. Topics discussed here include: 1) System configuration and hardware, 2) Modeling and design tools, and 3) Recent applications.     

An investigation of building/wind interaction

The interaction between buildings and their external environment is ultimately reflected on human comfort. A locally-built wind tunnel was designed, tested and utilized with different measuring facilities to obtain the pressure contours on the surfaces of the model at different wind speeds and directions. A smoke tunnel visualization technique was used to illustrate the separation, reattachment and wake spread around the building models. ANSYS FLOTRAN CFD computer package which utilizes the finite element approach, was also used to analyze the flow around building models as velocity and pressure contours. Comparison between results obtained showed good agreement.     

Power control of a solar/wind generation system without wind measurement: a passivity/sliding mode approach

This paper deals with the control of the output power of a solar/wind stand-alone system. The control system regulates the generation of the wind subsystem in order to satisfy, jointly with the photovoltaic generation subsystem, the load and battery charge power demand. The controller is designed using a theoretical framework that unifies passivity and sliding mode techniques. The resultant control law does not need wind measurement and only relies on rotational speed and current measurements. An analysis of the acceleration estimate error is carried out and a countermeasure to compensate its effects is proposed. Finally, the performance of the controller is assessed through computer simulation, using a comprehensive nonlinear model of the plant.     

Footprints in the wind?: Environmental impacts of wind power development

Although wind power plants have relatively little impact on the environment compared with other conventional power plants, there have been some concerns. Paul Magoha, Kenya takes a closer look at the environmental impact of wind power development and the significance of any current areas of concern.     

Computer-aided design of PV/wind hybrid system

A complete set of match calculation methods for optimum sizing of PV/wind hybrid system is presented. In this method, the more accurate and practical mathematic models for characterizing PV module, wind generator and battery are adopted; combining with hourly measured meteorologic data and load data, the performance of a PV/wind hybrid system is determined on a hourly basis; by fixing the capacity of wind generators, the whole year’s LPSP (loss of power supply probability) values of PV/wind hybrid systems with different capacity of PV array and battery bank are calculated, then the trade-off curve between battery bank and PV array capacity is drawn for the given LPSP value; the optimum configuration which can meet the energy demand with the minimum cost can be found by drawing a tangent to the trade-off curve with the slope representing the relationship between cost of PV module and that of the battery. According to this match calculation method, a set of match calculation programs for optimum sizing of PV/wind hybrid systems have been developed. Applying these match calculation programs to an assumed PV/wind hybrid system to be installed at Waglan island of Hong Kong, the optimum configuration and its hourly, daily, monthly and yearly performances are given.     

Modeling of hybrid photovoltaic/wind/fuel cells power system

In this paper, identification and modeling of a hybrid photovoltaic/wind/fuel cells power system is presented. This system comprises also a battery storage supplying a load via an inverter. The identification of each subsystem has been made and then the proposed system is modeled and simulated under Matlab/Simulink Package. The power control of the hybrid system is introduced by using LabVIEW Software. The mathematical model topology and its power management of the global system with battery bank system are significant contributions of our work. The proposed control strategy has been experimentally implanted and practical results are compared to those obtained by simulation under the same metrological conditions, showing the effectiveness of the proposed hybrid system.     

Environmental/economic power dispatch with wind power

Economic environmental dispatch (EED) is a significant optimization problem in electric power system. With more wide spread use of wind power, it is necessary to include wind energy conversion system (WECS) in the EED problem. This paper presents a model to solve the EED problem incorporating wind power. In addition to the classic EED factors, the factors accounting for overestimation and underestimation of available wind power in both economic and environmental aspects are also considered. In order to obtain some quantitative results, the uncertain characteristic of available wind power and the performance of WECS are determined on the basis of the statistical characteristic of wind speed. The optimization problem is numerically solved by a scenario involving two conventional generators and two wind-powered generators. The results demonstrate that the allocation of system generation capacity may be influenced by multipliers related to the cost for overestimation and underestimation of available wind power, and by the multiplier related to the emissions for underestimation of available wind power. Nevertheless, the multiplier related to the emissions for overestimation of available wind power has little impact on the allocation. Taking account of economic factors, environmental factors and impacts of wind power penetration, the proposed EED model is beneficial to finding the right balance between radical and conservative strategy for wind power development.     

Techno-economical optimization of hybrid pv/wind/battery system using Neuro-Fuzzy

High cost of renewable energy systems has led to its slow adoption in many countries. Hence, it is vital to select an appropriate size of the system in order to reduce the cost and excess energy produced as well as to maximize the available resources. The sizing of hybrid system must satisfy the LPSP (Loss of Power Supply Probability) which determines the ability of the system to meet the load requirements. Once the lowest configurations are determined, the cost of the system must then be taken into consideration to determine the system with the lowest cost. The optimization methodology proposed in this paper uses the ANFIS (Adaptive Neuro-Fuzzy Inference System) to model the PV and wind sources. The algorithm developed is compared to HOMER (Hybrid Optimization Model for Electric Renewables) and HOGA (Hybrid Optimization by Genetic Algorithms) software and the results demonstrate an accuracy of 96% for PV and wind. The optimized system is simulated in PSCAD/EMTDC and the results show that low excess energy is achieved. The optimized system is also able to supply power to the load without any renewable sources for a longer period, while conforming to the desired LPSP.