变桨距风力机叶片的气动优化设计

首先利用Wilson方法进行叶片的外形初步设计,然后以设计攻角作为变量,以额定风速下功率系数最大为优化目标,建立了1 MW变桨距风力机叶片气动外形优化模型,采用遗传算法进行了优化再设计。通过对3叶片1 MW风力机进行的气动性能评价结果表明,优化后的风力机具有更好的气动性能,说明采用该优化方法进行变桨距风力机设计具有明显的优越性。     

直驱风电系统最大功率捕获技术的仿真分析

对直驱风电系统最大功率捕获技术进行了仿真分析.在仿真过程中,通过控制发电机组转速来实现风力机的最佳运行,使功率系数、风力机转速及输出机械功率等参数都能运行在不同风速下的最优值,从而最大限度地捕获风能.当发电机组达到最优运行时,再通过控制整流器使其输出恒定的电压.     

可变偏心距风力机模态特性分析

在水平轴风力机的结构基础上,文章提出了一种具有风轮侧偏功率调节功能的可变偏心距风力机。通过对整机进行模态分析及风洞测试,验证了该风力机在不同来流风速下运行的稳定性。模态分析结果显示:可变偏心距风力机前6阶固有频率均处于共振带之外;摆振为可变偏心距风力机整机的主要振动形式;来流风速对风力机的振动频率影响较小,在不同偏心距工况下,随着来流风速的增大,1阶动频均呈减小趋势,最大降幅为0.14%;风轮转速对风力机的振动频率影响较大,随着转速的升高,风力机的动频会显著升高,当风轮转速为180 r/min时,1阶动频较额定转速工况(450 r/min)相差24%;当风轮转速达到630 r/min时,1阶动频较额定转速工况相差14%;通过增大偏心距可实现对输出功率的有效控制,当来流风速为16 m/s时,右偏100 mm工况下的输出功率为未偏心工况的64%。     

风力机的新型变桨距自抗扰控制系统

采用高速浮点 TMS320F28335(DSP)芯片作为硬件核心控制器,运用自抗扰控制系统算法对风力机桨距角进行精确调整,实现了一种由新型软硬件相结合的风力机变桨距控制系统.结果表明:当风速高于额定风速或者瞬时输出功率大于额定功率时,通过对桨叶桨距角的精确调整,可使输出功率动态维持在额定功率附近.变桨距自抗扰控制系统算法实现简单,具有良好的动态响应特性,能有效保障风力机的安全运行.     

基于混沌优化PID风力发电机组变桨距系统研究

变桨距控制是永磁直驱同步风力发电系统在额定风速以上限制功率输出的主要控制手段,文章基于风力机功率输出特性曲线,分析了永磁直驱风力发电系统变桨距控制在全风况下对应的控制策略。在额定风速以上时利用转速和功率相结合的双闭环变桨距控制系统,并在传统的PID控制器的基础上运用了混沌优化技术,用来减小在额定风速附近引起的输出功率波动及载荷突变的不利影响。通过Matlab仿真软件对混沌优化变桨距进行验证,仿真结果表明该变桨距控制策略响应速度快且鲁棒性强。     

大型直驱永磁风力发电机及其并网运行研究

为了研究大型直驱式永磁风力发电机控制及其并网后在电力系统中的运行,建立了风速模型、发电机模型,对直驱式永磁风力发电机的工作原理进行了研究,对风力发电机接入电网运行进行了分析,并对最大功率跟踪和桨距角控制进行了研究.采用理论分析与计算机仿真方法,给出了仿真结果.结果表明,直驱永磁风力发电机在低于额定风速时可以跟踪最大功率,高于额定风速时可以保持额定功率;直驱式永磁风力机对故障电流无贡献,对电网谐波影响很小,几乎不存在闪变问题,对电网频率稳定性无贡献.     

额定风速附近变速变桨风力发电机组功率优化控制

详细分析导致功率波动和功率损失的原因,提出一种转矩优化控制策略。该转矩优化控制方法结合查表法和非线性PI控制器,在低风速区仅启用查表法以追踪最优功率;额定风速附近及以上时运用非线性PI控制器使转矩输出形成滞环,来抑制额定风速附近的功率波动;采用基于转矩误差及误差变化率的桨距角模糊调节器,实现转矩和变桨控制解耦;给出一种功率平均值限制算法,可抑制阵风时(包括额定风速以下和以上)引起的转速短时过速和功率损失,同时也可减少变桨机构的疲劳载荷。以风力机设计专业软件Bladed为工具,结合C语言编写外部控制器,对风力发电机组转矩及变桨控制策略进行仿真研究,仿真结果表明所提出的优化方案可行。     

小型定桨距风力机卸荷电阻动态无级调节主动失速控制研究

针对小型直驱永磁同步风力发电系统的失速控制问题,提出一种新型的风力机失速控制方法。该方法实现卸荷电阻的动态无级调节,在风速大于额定值小于切除风速时,对卸荷电阻进行动态调节,使系统以恒功率运行;在风速大于切出风速值时,通过控制卸荷电阻实现平稳停机。综合所提出的风力机失速控制方法和额定风速以下的最大功率跟踪控制目标,进一步提出系统统一的控制算法,该方法不仅可实现低风速区的最大功率跟踪控制,且在高风速区实现恒转速和恒功率控制以及切出风速时的停机控制。仿真结果验证了所提新型失速控制方法的正确性与有效性。     

偏航偏差角对风力机轮毂载荷的影响

偏航工况是风力机正常运行中的典型工况,为研究偏航工况下风力机轮毂载荷的特性,文章以某实验型3.0 MW机组为研究对象,通过叶片气动分析和Bladed软件仿真的方法,对不同偏航偏差角下的风力机载荷进行仿真分析,得到了风力机的输出功率及轮毂My和Mz的载荷。研究结果表明：当风力机运行在额定风速以下时,偏航偏差角的存在会降低风力机输出功率;当风力机运行在额定风速以上时,一定范围内的偏航偏差角能维持风力机满功率稳定运行。风力机在不同偏航方向下有不同的载荷表现,相比于负向的偏航偏差角,正向的偏航偏差角会导致更大的风力机轮毂载荷。该研究为大型风力机优化偏航控制及保护提供了参考。     

加装后缘小翼的垂直轴风力机输出特性研究

为了研究H型垂直轴风力机后缘加装小翼的输出特性变化规律,文章以NACA0012翼型叶片为例,采用风洞试验与数值模拟的方法,对加装后缘小翼的风力机进行了研究。模拟结果表明,加装后缘小翼的风力机的单叶片扭矩系数及功率性能要优于未加装小翼的风力机,整体功率较未加装小翼的风力机略有提升。风洞实验结果表明:加装后缘小翼可以提高风力机的最大输出功率,其中径长比对于加装小翼的垂直轴风力机功率提升的影响较大;当转速小于300 r/min时,安装径长比为0.6的后缘小翼的风力机输出功率最高;当转速超过300 r/min时,径长比为0.4的后缘小翼的风力机输出功率最高。     

Optimized linearization of chord and twist angle profiles for fixed-pitch fixed-speed wind turbine blades

The chord and twist angle radial profiles of a fixed-pitch fixed-speed (FPFS) horizontal-axis wind turbine blade are based on a particular design wind speed and design tip speed ratio. Because the tip speed ratio varies with wind speed, the originally optimized chord and twist angle radial profiles for a preliminary blade design through optimum rotor theory do not necessarily provide the highest annual energy production (AEP) for the wind turbine on a specific site with known wind resources. This paper aims to demonstrate a novel optimal blade design method for an FPFS wind turbine through adopting linear radial profiles of the blade chord and twist angle and optimizing the slope of these two lines. The radial profiles of the blade chord and twist angle are linearized on a heuristic basis with fixed values at the blade tip and floating values at the blade root based on the preliminary blade design, and the best solution is determined using the highest AEP for a particular wind speed Weibull distribution as the optimization criteria with constraints of the top limit power output of the wind turbine. The outcomes demonstrate clearly that the proposed blade design optimization method offers a good opportunity for FPFS wind turbine blade design to achieve a better power performance and low manufacturing cost. This approach can be used for any practice of FPFS wind turbine blade design and refurbishment.     

基于FAST和Simulink的海上风力机叶片扭角和弦长优化设计研究

基于粒子群算法编写风力机叶片优化程序,利用Matlab/Simulink接口嵌入到FAST主程序之中实现叶片优化程序与FAST之间的交互,以实现风力机最大发电功率为优化目标,完成风力机叶片气动外形的自动寻优。该方法可考虑实际海况及风力机搭载平台对叶片优化结果的影响,可同时考虑风向分布对优化结果的影响。NREL 5 MW风力机低风速下的优化结果表明,经过优化后的风力机功率提高1.5%。当考虑实际风力机布置海域风向分布情况时,加权优化结果表明风力机最大功率可提高3.8%。     

Testing basic performance of a very small wind turbine designed for multi-purposes

A very small wind turbine system for multi-purposes was developed and its performance was reported in this paper. The rotor diameter of the turbine is 500 mm. The tests of the energy output, turbine speed, power coefficient, and torque of turbine were carried out for a wide rage of free stream velocity. The flow around the wind turbine and the influence of the turbulence were investigated with a particle image velocimetry. Experimentally obtained power coefficient was 0.4 in maximum and 0.36 in the rated running condition, respectively. The tip speed ratio corresponding to the optimum driving condition was 2.7. Comparing with the other commercial turbines, the performance was excellent at a slow turbine speed. By the flow visualization and PIV measurement around the wind turbine, the approaching flow velocity and the accelerated flow field passing the blade tip was obtained. It was confirmed that the actual flow passed through the blades was about 20% slower than the ideal flow. Tip vortex shed from the blade tip was also visualized clearly.     

Wells turbine blade profile optimization for better wave energy capture

Despite the fact that wave energy is available at no cost, it is always desired to harvest the maximum possible amount of this energy. The axial flow air turbines are commonly used with oscillating water column devices as a power take‐off system. The present work introduces a blade profile optimization technique that improves the air turbine performance while considering the complex 3D flow phenomena. This technique produces non‐standard blade profiles from the coordinates of the standard ones. It implements a multi‐objective optimization algorithm in order to define the optimum blade profile. The proposed optimization technique was successfully applied to a biplane Wells turbine in the present work. It produced an optimum blade profile that improves the turbine torque by up to 9.3%, reduces the turbine damping coefficient by 10%, and increases the turbine operating range by 5%. The optimized profile increases the annual average turbine power by up to 3.6% under typical sea conditions. Moreover, new blade profiles were produced from the wind turbine airfoil data and investigated for use with the biplane Wells turbine. The present work showed that two of these profiles could be used with low wave energy seas. Copyright © 2017 John Wiley & Sons, Ltd.     

The concept of a smart wind turbine system

A smart wind turbine concept with variable length blades and an innovative hybrid mechanical-electrical power conversion system was analyzed. The variable length blade concept uses the idea of extending the turbine blades when wind speeds fall below rated level, hence increasing the swept area, and thus maintaining a relatively high power output. It is shown for a typical site, that the annual energy output of such a wind turbine that could double its blade length, could be twice that of a corresponding turbine with fixed length blades. From a cost analysis, it is shown that the concept would be feasible if the cost of the rotor could be kept less than 4.3 times the cost of a standard rotor with fixed length blades. Given the variable length blade turbine system exhibits a more-or-less linear maximum power curve, as opposed to a non-linear curve for the standard turbine, an innovative hybrid mechanical-electrical power conversion system was proposed and tested proving the feasibility of the concept.     

浅析水平轴风力机叶片设计叶尖速比的选择

设计叶尖速比是风力机叶片设计中需要考虑的重要因素,文中分析了叶尖速比对叶片的弦长、载荷、气动性能、整机的功率和发电量等的影响,讨论了设计叶尖速比的选择。并分析得出增大设计叶尖速比,能够减小叶片弦长、载荷、成本,提高气动性能,但会使机组发电量有所下降的结论。     

预弯对10MW级风力机叶片气动特性的影响

为分析预弯处理对10 MW级风力机叶片气动特性的影响,以DTU 10 MW风力机为例,采用CFD数值模拟方法,研究均匀来流不同风速下风力机的输出功率,并与BEM计算结果进行对比。同时,对比分析直叶片和预弯叶片风力机的功率特性、沿展向出力分布、沿展向不同截面翼型的流动特性。研究结果表明,直叶片各截面翼型的压力差较预弯叶片的大,做功能力较强。预弯通过对叶片的三维流动产生扰动,进而影响风力机的输出功率,且主要体现在叶片展向70%~90%的位置。研究成果可为风力机叶片气动性能的设计与优化提供参考。     

The application of passive air jet vortex‐generators to stall suppression on wind turbine blades

An experimental study was performed to assess the feasibility of passive air jet vortex‐generators to the performance enhancement of a domestic scale wind turbine. It has been demonstrated that these simple devices, properly designed and implemented, can provide worthwhile performance benefits for domestic wind turbines of the type investigated in this study. In particular, this study shows that they can increase the maximum output power coefficient, reduce the cut‐in wind speed and improve power output at lower wind speeds while reducing the sensitivity to wind speed unsteadiness. A theoretical performance analysis of a 500 kW stall‐regulated wind turbine, based on blade element momentum theory, indicates that passive air jet vortex‐generators would be capable of recovering some of the power loss because of blade stall, thereby allowing attainment of rated power output at slightly lower average wind speeds. Copyright © 2016 John Wiley & Sons, Ltd.