Hybrid damper with stroke amplification for damping of offshore wind turbines

The magnitude of tower vibrations of offshore wind turbines is a key design driver for the feasibility of the monopile support structure. A novel control concept for the damping of these tower vibrations is proposed, where viscous‐type hybrid dampers are installed at the bottom of the wind turbine tower. The proposed hybrid damper consists of a passive viscous dashpot placed in series with a load cell and an active actuator. By integrated force feedback control of the actuator motion, the associated displacement amplitude over the viscous damper can be increased compared with the passive viscous case, hereby significantly increasing the feasibility of viscous dampers acting at the bottom of the wind turbine tower. To avoid drift in the actuator displacement, a filtered time integration of the measured force signal is introduced. Numerical examples demonstrate that the filtered time integration control leads to performance similar to that of passive viscous damping and substantial amplification of the damper deformation without actuator drift. Copyright © 2016 John Wiley & Sons, Ltd.     

Passive control of wind turbine vibrations including blade/tower interaction and rotationally sampled turbulence

This paper investigates the use of a passive control device, namely, a tuned mass damper (TMD), for the mitigation of vibrations due to the along‐wind forced vibration response of a simplified wind turbine. The wind turbine assembly consists of three rotating uniform rotor blades connected to the top of a flexible uniform annular tower, constituting a multi‐body dynamic system. First, the free vibration properties of the tower and rotating blades are each obtained separately using a discrete parameter approach, with those of the tower including the presence of a rigid mass at the top, representing the nacelle, and those of the blade including the effects of centrifugal stiffening due to blade rotation and self‐weight. Drag‐based loading is assumed to act on the rotating blades, in which the phenomenon of rotationally sampled wind turbulence is included. Blade response time histories are obtained using the mode acceleration method, allowing base shear forces due to flapping motion for the three blades to be calculated. The resultant base shear is imparted into the top of the tower. Wind drag loading on the tower is also considered, and includes Davenport‐type spatial coherence information. The tower/nacelle is then coupled with the rotating blades by combining their equations of motion. A TMD is placed at the top of the tower, and when added to the formulation, a Fourier transform approach allows for the solution of the displacement at the top of the tower under compatibility of response conditions. An inverse Fourier transform of this frequency domain response yields the response time history of the coupled blades/tower/damper system. A numerical example is included to qualitatively investigate the influence of the damper. Copyright © 2007 John Wiley & Sons, Ltd.     

Damping of edgewise vibration in wind turbine blades by means of circular liquid dampers

This paper proposes a new type of passive vibration control damper for controlling edgewise vibrations of wind turbine blades. The damper is a variant of the liquid column damper and is termed as a circular liquid column damper (CLCD). Rotating wind turbine blades generally experience a large centrifugal acceleration. This centrifugal acceleration makes the use of this kind of oscillatory liquid damper feasible with a small mass ratio to effectively suppress edgewise vibrations. A reduced 2‐DOF non‐linear model is used for tuning the CLCD attached to a rotating wind turbine blade, ignoring the coupling between the blade and the tower. The performance of the damper is evaluated under various rotational speeds of the rotor. A special case in which the rotational speed is so small that the gravity dominates the motion of the liquid is also investigated. Further, the legitimacy of the decoupled optimization is verified by incorporating the optimized damper into a more sophisticated 13‐DOF aeroelastic wind turbine model with due consideration to the coupled blade‐tower‐drivetrain vibrations of the wind turbine as well as a pitch controller. The numerical results from the illustrations on a 5 and a 10MW wind turbine machine indicate that the CLCD at an optimal tuning can effectively suppress the dynamic response of wind turbine blades. Copyright © 2015 John Wiley & Sons, Ltd.     

柱状漂浮式风力机结构振动控制

针对柱状漂浮式风力机的结构振动控制展开研究。首先为进行调谐质量阻尼器(TMD)参数的优化,对风力机模型进行简化,并对简化模型中的未知参数进行估计;随后,基于简化模型分别使用公式法和遗传算法对TMD参数进行优化,并通过比较塔顶前后位移的标准偏差确定最终的优化方法;最后,为评估TMD对风力机振动控制的影响,构建风力机的联合仿真模型,并在3种典型工况下进行仿真分析。仿真结果表明,所设计的TMD可以很好地降低漂浮式风力机的载荷以及位移,有效抑制塔顶振动加速度与系泊缆绳有效张力,同时可有效降低额定风速以上时电功率输出的标准偏差,使电功率输出更加稳定。     

基于TMD的风力机塔筒振动控制研究

针对风力机塔筒在风振效应下振动过大的问题,该文基于调谐质量阻尼器(TMD)开展对风力机塔筒的减振控制研究。以某大型2 MW风力机塔筒为研究对象,基于ANSYS建立柔性的风力机塔筒有限元模型,并基于Kaimal谱和模态脉动曳力功率谱模拟得到脉动风速时程和风载时程曲线。为取得较好的TMD减振控制效果,根据Den Hartog法得到TMD的最优频率比和阻尼比。为分析TMD对塔筒结构强度的影响及其TMD的振动控制效果,对风力机塔筒进行静力学和风载作用下的动力响应仿真分析。研究结果表明:TMD对塔筒的静强度影响较小,相比于将TMD放置于塔筒内部,将TMD放置于塔顶机舱内能更有效地减小塔筒在风振效应下的位移峰值、标准偏差以及瞬态应力峰值,其抑制率分别达到63.51%、63.38%和59.74%。     

随机风浪作用下漂浮式风力机MTMD振动控制研究

基于多体动力学理论,通过二次开发,基于FAST-SC建立漂浮式风力机-多重调谐质量阻尼器（MTMD）耦合振动控制模型FAST-SC-MTMD。以驳船式海上风力机为研究对象,基于线性调频优化方法完成布置于机舱和平台位置的TMD参数设计。以漂浮式风力机结构运动响应控制率为评价指标,研究在随机荷载激励下将TMD和MTMD应用于在驳船式风力机的减振效果。研究发现,采用机舱和平台同时布置MTMD的减振控制策略,可有效降低驳船式风力机塔基荷载和运动响应。     

基于TMD的海上漂浮式风力机稳定性研究

海上漂浮式风力机的稳定性研究已逐渐成为风电研究的重点与热点。以NREL(国家可再生能源实验室)5 MW风力机及ITI Barge平台为研究对象,建立海上漂浮式风力机整机模型,通过配置TMD(调谐质量阻尼器),研究其对环境载荷作用下的海上漂浮式风力机稳定性的控制效果。结果表明:TMD对漂浮式风力机塔架和平台的运动响应有明显的抑制效果,在TMD控制下,漂浮式风力机塔顶左右位移最大值降低近50%,稳定性提高38%;对漂浮式风力机平台的横摇及横荡运动控制效果较明显,平台横荡稳定性提高18%,横摇稳定性提高41%。     

Vibration suppression of a floating hydrostatic wind turbine model using bidirectional tuned liquid column mass damper

We propose to mitigate the barge pitch and roll motions of floating hydrostatic wind turbine (HWT) by combining the advantages of the bidirectional tuned liquid column damper (BTLCD) and the tuned mass damper (TMD). This is achieved by enabling the container of the BTLCD to move freely, connecting it to the main structure through springs and dampers, creating what we call a bidirectional tuned liquid column mass damper (BTLCMD). The BTLCMD is made by the hydraulic reservoir of the HWT, saving costs by avoiding the addition of extra mass and fluids. The HWT simulation model is obtained by replacing the geared drivetrain of the NREL 5‐MW barge wind turbine model with a hydrostatic transmission drivetrain. The dynamics of the BTLCMD are then incorporated into the HWT. Two simplified mathematical models, describing the barge pitch and roll motions of the HWT‐BTLCMD coupled system, are used to obtain the optimal parameters of the BTLCMD. Simulation results demonstrate that the BTLCMD is very effective in mitigating the barge pitch motion, barge roll motion, and the tower base load. The BTLCMD also largely outperforms the BTLCD in suppressing barge motions.     

基于SMA阻尼器控制的鼓型塔风振响应分析

以某220kV输电线路的风致振动为例,研究了基于SMA阻尼器的鼓型塔振动控制方案和控制效果。先应用有限元软件ANSYS建立鼓型塔的有限元模型,采用线性自回归滤波器法模拟随机脉动风荷载的时程样本,再应用能量法计算所需阻尼器数量,根据SMA阻尼器的工作原理和鼓型塔的结构特点,设计了3种阻尼器布置方案进行结构风致振动瞬态响应仿真,提取各方案控制点位移、加速度时间历程进行比较分析。结果表明,安装SMA阻尼器后,对塔顶位移、加速度的最大减振率分别为37.8%、75.4%,方案3为最优布置方案,可见将SMA阻尼器应用于输电塔振动控制效果较好,合理设计阻尼器布置方案能使阻尼器发挥最大耗能功能,获得最好控制效果。     

An investigation on the impacts of passive and semiactive structural control on a fixed bottom and a floating offshore wind turbine

The application of structural control to offshore wind turbines (OWTs) using tuned mass dampers (TMDs) has shown to be effective in reducing the system loads. The parameters of a magnetorheological (MR) damper modeled by the Bouc‐Wen model are modified to utilize it as a damping device of the TMD. Rather than showcasing the intricate design policy, this research focuses on the availability of the MR damper model on TMDs and its significance on structural control. The impact of passive and semiactive (S‐A) TMDs applied to both fixed bottom and floating OWTs is evaluated under the fatigue limit state (FLS) and the ultimate limit state (ULS). Different S‐A control logics based on the ground hook (GH) control policy are implemented, and the frequency response of each algorithm is investigated. It is shown that the performance of each algorithm varies according to the load conditions such as a normal operation and an extreme case. Fully coupled time domain simulations are conducted through a newly developed simulation tool, integrated into FASTv8. Compared with the passive TMD, it is shown that the S‐A TMD results in higher load reductions with smaller strokes under both the FLS and the ULS conditions. The S‐A TMD using displacement‐based GH control is capable of reducing the fore‐aft and side‐to‐side damage equivalent loads for the monopile by approximately 12% and 64%, respectively. The ultimate loadings at the tower base for the floating substructure are reduced by 9% with the S‐A TMD followed by inverse velocity‐based GH control (IVB‐GH).     

基于粘滞阻尼器的单桩式海上风力机结构振动控制

为探究湍流风与地震联合作用下单桩式海上风力机的结构动力学响应与振动控制,以单桩式NREL 5 MW海上风力机为研究对象,采用有限元法建立三维壳模型并基于二次开发将体等效线性模型集成于ABAQUS中,通过附加粘滞阻尼器对地震诱导风力机振动进行控制。结果表明:粘滞阻尼器能够大幅降低地震导致的风力机塔顶振动,但对湍流风引起的塔顶振动控制效果并不明显;粘滞阻尼器也能缓解因地震造成的支撑结构上Von-Mises应力集中现象且在粘滞阻尼器安装位置效果最好;粘滞阻尼器能够显著降低风力机桩基部分所受剪力最大值,而对弯矩的控制效果则在风力机支撑结构部分效果最明显。     

Passive structural control of offshore wind turbines

The application of control techniques to offshore wind turbines has the potential to significantly improve the structural response of these systems. A new simulation tool is developed that can be utilized to model passive, semi‐active and active structural control systems in wind turbines. Two independent, single degree of freedom (DOF) tuned mass‐ damper (TMD) devices are incorporated into a modified version of the aero‐elastic code FAST (Fatigue, Aerodynamics, Structures and Turbulence). The TMDs are located in the nacelle of the turbine model, with one TMD translating in the fore‐aft direction, and the other in the side‐side direction. The equations of motion of the TMDs are incorporated into the source code of FAST, yielding a more realistic system for modeling structural control in wind turbines than has previously been modeled. The stiffness, damping and commanded force of each TMD are controllable through the FAST‐Simulink interface, and so idealizations of semi‐active and active control approaches can be implemented. A parametric study is performed to determine the optimal parameters of a passive single DOF, fore‐aft, TMD system in both a barge‐type and monopile support structure. The wind turbine models equipped with TMDs are then simulated and the performance of these new systems is evaluated. The results indicate that passive control approaches can be used to improve the structural response of offshore wind turbines. The results also demonstrate the potential for active control approaches. Copyright © 2010 John Wiley & Sons, Ltd.     

单桩海上风力机风致振动变阻尼控制研究

风致振动是大型风力机发生破坏性事故的主要原因.为探究半主动控制在近海单桩风力机风致振动控制中的应用效果,基于ABAQUS有限元软件二次开发了风力机半主动控制模块,以单桩式NREL5 MW海上风力机为研究对象,通过磁流变阻尼器对Bang-Bang控制、改进Bang-Bang控制及Lyapunov控制3种半主动控制算法在单...     

海上风机塔架和单桩一体化试验设计方法

  目的  国内海上风电项目的业主在招主机标时,对风机厂商提供的基础顶载荷和塔架质量提出要求,在招设计标时很少对设计院提供的基础质量提出要求;详细设计阶段时风机厂商和设计院分别对塔架和基础进行设计,因此通常难以得到塔架和基础总质量最小的全局最优设计。  方法  提出了海上风机塔架和单桩一体化试验设计方法,通过对某海上风电项目进行试验设计得到多个不同塔架构型、塔底和单桩直径的设计方案,并通过载荷计算、塔架和单桩设计迭代优化得到相应的基础顶载荷、塔架质量和单桩质量等结果。  结果  研究表明:基础顶载荷或塔架质量最小的方案不是塔架和单桩总质量最小的方案。通过试验设计方法可以给出单桩和塔架总质量最小的最优设计。  结论  研究成果表明,在设计中采用一体化试验设计方法寻找塔架和单桩总质量最小的全局最优设计是降低海上风电度电成本的有效方法。业主将制定塔架和基础总造价最小的招标规则,要求采用一体化试验设计方案找到全局最优设计。     

Vibration suppression for monopile and spar‐buoy offshore wind turbines using the structure‐immittance approach

Offshore wind turbines have the potential to capture the high‐quality wind resource. However, the significant wind and wave excitations may result in excessive vibrations and decreased reliability. To reduce vibrations, passive structural control devices, such as the tuned mass damper (TMD), have been used. To further enhance the vibration suppression capability, inerter‐based absorbers (IBAs) have been studied using the structure‐based approach, that is, proposing specific stiffness‐damping‐inertance elements layouts for investigation. Such an approach has a critical limitation of being only able to cover specific IBA layouts, leaving numerous beneficial configurations not identified. This paper adopts the newly introduced structure‐immittance approach, which is able to cover all network layout possibilities with a predetermined number of elements. Linear monopile and spar‐buoy turbine models are first established for optimisation. Results show that the performance improvements can be up to 6.5% and 7.3% with four and six elements, respectively, compared with the TMD. Moreover, a complete set of beneficial IBA layouts with explicit element types and numbers have been obtained, which is essential for next‐step real‐life applications. In order to verify the effectiveness of the identified absorbers with OpenFAST, an approach has been established to integrate any IBA transfer functions. It has been shown that the performance benefits preserve under both the fatigue limit state (FLS) and the ultimate limit state (ULS). Furthermore, results show that the mass component of the optimum IBAs can be reduced by up to 25.1% (7,486 kg) to achieve the same performance as the TMD.     

动力总成动力吸振器特性研究

采用合适的动力吸振器对汽车动力总成的弯曲共振有较好的抑制作用,动力总成工况复杂,吸振器选择不合理反而可能适得其反。通过对动力总成吸振器进行试验研究,分析了动力总成吸振器的温度特性和激励特性,并应用于动力吸振器设计,成功解决了某车型由于动力总成弯曲共振导致的车内振动噪声大的问题。     

钢-混凝土组合式风力发电塔架地震响应分析

钢-混凝土组合式风力发电塔架上部为钢塔筒,下部为混凝土塔筒,高度方向具有较大的质量和刚度突变,其在地震作用下的响应和传统单管式钢塔架显著不同.利用ABAQUS对同一风电场的2.0 MW单管式钢塔架和组合式塔架建立精细化模型,选取3种场地条件,采用振型分解反应谱法计算2种塔架的地震响应并进行对比.针对3种场地条件,选取相...     

Passive vibration control of an offshore floating hydrostatic wind turbine model

We propose to make use of the hydraulic reservoir of a floating barge hydrostatic wind turbine (HWT) to suppress the pitch and roll motions of the barge by making the reservoir into a shape of an annular rectangular to serve as a bidirectional tuned liquid column damper (BTLCD). This means that we have made a barge‐motion damper with negligible extra costs as an HWT needs a reservoir for fluid storage anyway. The barge HWT simulation model is transformed from the NREL (National Renewable Energy Laboratory) 5‐MW geared equipped ITI Energy barge wind turbine model within the FAST (fatigue, aerodynamics, structures, and turbulence) code by replacing its drivetrain with a hydrostatic transmission drivetrain and incorporating the coupled dynamics of the barge‐reservoir system. We use 2 simplified turbine‐reservoir models to optimize the parameters of the BTLCD reservoir, which describe the pitch and roll motions of the turbine‐reservoir system, respectively. Simulation results based on the transformed NREL 5‐MW barge HWT model show that the optimal BTLCD reservoir is very effective in mitigating pitch and roll motions of the barge under realistic wind and wave excitations, which reduces the tower load and improves the power quality.     

High‐fidelity linear time‐invariant model of a smart rotor with adaptive trailing edge flaps

A high‐fidelity linear time‐invariant model of the aero‐servo‐elastic response of a wind turbine with trailing‐edge flaps is presented and used for systematic tuning of an individual flap controller. The model includes the quasi‐steady aerodynamic effects of trailing‐edge flaps on wind turbine blades and is integrated in the linear aeroelastic code HAWCStab2. The dynamic response predicted by the linear model is validated against non‐linear simulations, and the quasi‐steady assumption does not cause any significant response bias for flap deflection with frequencies up to 2–3 Hz. The linear aero‐servo‐elastic model support the design, systematic tuning and model synthesis of smart rotor control systems. As an example application, the gains of an individual flap controller are tuned using the Ziegler–Nichols method for the full‐order poles. The flap controller is based on feedback of inverse Coleman transformed and low‐pass filtered flapwise blade root moments to the cyclic flap angles through two proportional‐integral controllers. The load alleviation potential of the active flap control, anticipated by the frequency response of the linear closed‐loop model, is also confirmed by non‐linear time simulations. The simulations report reductions of lifetime fatigue damage up to 17% at the blade root and up to 4% at the tower bottom. Copyright © 2016 John Wiley & Sons, Ltd.     

Evaluation of pressure coefficients and estimation of air flow rates in buildings employing wind towers

Wind pressure coefficients at various openings of a wind tower were determined by testing a scale model of the building in a boundary layer wind tunnel. Wind towers (or Baud-Geers) are structures which have been employed in Iran and neighbouring countries for natural ventilation and passive cooling. Tests were conducted on an isolated tower, the tower and adjoining house, and the tower and house surrounded by a courtyard. The wind pressure coefficients at the tower and house openings were determined at various wind angles for two types of terrain: suburban and open country. The air flow rates were then estimated from a knowledge of the wind pressure coefficients at the building apertures. It was concluded that the presence of a courtyard around the structure and the angle of incidence of the wind influence the rate and the direction of air flowing from the tower to the house. If leeward openings of the tower can be closed (for example, by automatic dampers) restricting the air leaving these apertures, the air flow rate from the tower to the house can be greatly increased. The results of this investigation are believed to provide assistance to architects and engineers in the design of wind towers for desired ventilation rates in buildings.