Coordinated Rotor-Side Control Strategy for Doubly-FedWind Turbine under Symmetrical and Asymmetrical Grid Faults

In order to solve the problems of rotor overvoltage,overcurrent and DC side voltage rise caused by grid voltage drops,a coordinated control strategy based on symmetrical and asymmetrical low voltage ride through of rotor side converter of the doubly-fed generator is proposed.When the power grid voltage drops symmetrically,the generator approximate equation under steady-state conditions is no longer applicable.Considering the dynamic process of stator current excitation,according to the change of stator flux and the depth of voltage drop,the system can dynamically provide reactive power support for parallel nodes and suppress the rise of DC side voltage and rotor over-current.When the grid voltage drops asymmetrically,the positive and negative sequence components are separated in the rotating coordinate system.The doubly fed generator model is established to suppress the rotor positive sequence current and negative sequence current respectively.At the same time,the output voltage limit of the converter is discussed,and the reference value is adjusted within the allowable output voltage range.In order to adapt to the occurrence of different types of power grid faults and complex operating conditions,a fast switching module of fault type detection and rotor control mode is designed to detect the type of power grid faults and voltage drop depth in real time and switch the rotor side control mode dynamically.Finally,the simulation model of the doubly fed wind turbine is constructed in Matlab/Simulink.The simulation results verify that the proposed control strategy can improve the low-voltage ride through performance of the system when dealing with the symmetrical and asymmetric voltage drop of the power grid and identify the power grid fault type and provide the correct control strategy.

Validation of the Actuator Line Model for Simulating Flows past Yawed Wind Turbine Rotors

The Actuator Line/Navier-Stokes model is validated against wind tunnel measurements for flows past the yawed MEXICO rotor and past the yawed NREL Phase VI rotor. The MEXICO rotor is operated at a rotational speed of 424 rpm, a pitch angle of ?2.3。, wind speeds of 10, 15, 24 m/s and yaw angles of 15。, 30。 and 45。. The computed loads as well as the velocity field behind the yawed MEXICO rotor are compared to the detailed pressure and PIV measurements which were carried out in the EU funded MEXICO project. For the NREL Phase VI rotor, computations were carried out at a rotational speed of 90.2 rpm, a pitch angle of 3。, a wind speed of 5 m/s and yaw angles of 10。and 30。. The computed loads are compared to the loads measured from pressure measurement.

The Finite-Element Modeling of Dynamic Motions of a Constraint Wind Turbine and the System Diagnosis for the Safety Control

The aim of this paper is to present a finite element modeling of the dynamic motion of a turbine rotor and its controller design with the mass unbalance under a crack on a rotating shaft. This process is an advanced method to the mathematical description of a system including an influence of a mass unbalance and a crack on the rotor shaft. As the first step, the shaft is physically modeled with a finite element method and the dynamic mathematical model is derived by using the Hamilton principle;thus, the system is represented by various subsystems. The equation of motion of a shaft with a mass unbalance and a crack is established by adapting the local mass unbalance and stiffness change through breathing and gaping from the existence of a crack. This is a reference system for the given system. Based on a fictitious model for transient behavior induced from vibration phenomena measured at the bearings, an elementary estimator is designed for the safety control and detection of a mass unbalance on the shaft. Using the state estimator, a bank of an estimator is established to get the diagnosis and the system data for a controller.

Computational Fluid Dynamics Analysis of Multi-Bladed Horizontal Axis Wind Turbine Rotor

The principal objective of this work was to investigate the 3D flow field around a multi-bladed horizontal axis wind turbine (HAWT) rotor and to investigate its performance characteristics. The aerodynamic performance of this novel rotor design was evaluated by means of a Computational Fluid Dynamics commercial package. The Reynolds Averaged Navier-Stokes (RANS) equations were selected to model the physics of the incompressible Newtonian fluid around the blades. The Shear Stress Transport (SST) k-ω turbulence model was chosen for the assessment of the 3D flow behavior as it had widely used in other HAWT studies. The pressure-based simulation was done on a model representing one-ninth of the rotor using a 40-degree periodicity in a single moving reference frame system. Analyzing the wake flow behavior over a wide range of wind speeds provided a clear vision of this novel rotor configuration. From the analysis, it was determined that the flow becomes accelerated in outer wake region downstream of the rotor and by placing a multi-bladed rotor with a larger diameter behind the forward rotor resulted in an acceleration of this wake flow which resulted in an increase the overall power output of the wind machine.

Numerical Analysis of Horizontal-Axis Wind Turbine Characteristics in Yawed Conditions

Computational fluid dynamics (CFD) modeling and experiments have both advantages and disadvantages. Doing both can be complementary, and we can expect more effective understanding of the phenomenon. It is useful to utilize CFD as an efficient tool for the turbomachinery and can complement uncertain experimental results. However the CFD simulation takes a long time for a design in generally. It is need to reduce the calculation time for many design condi- tions. In this paper, it is attempted to obtain the more accurate characteristics of a wind turbine in yawed flow condi- tions for a short time, using a few grid points. It is discussed for the reliability of the experimental results and the CFD results.

A Summary Study of Wind Turbine with Related Control

One specific issue associated with the wind turbine is how to manage and adjust the rotor speed and pitch angle in the turbine with the wind increasing to achieve the maximum power extraction from the wind. The aim of this paper is to provide a summary study of the impact of related controls and operating strategies on the wind turbine which mean how parameters affect the wind turbine operation. The software of “GH bladed” produced by GL Garrad Hassan will be used to model wind turbine and to perform the analysis. Following two strategies, control of rotor speed and control of blade pitch angle, are applied to the model of the wind turbine to see how output power are adjusted and optimized. The final part proposes the operating strategy of the wind turbine to understand the running procedure of wind turbine inside.

Design and Analysis of Different Types of Rotors for Pico-Turbine

Small-scale vertical axis wind turbine (VAWT) rotor is developed for use in areas lacking adequate energy infrastructure. The materials and methods of construction are selected to minimize cost as much as possible. The paper describes the design of different kinds of vertical axis wind turbine rotors having different number of blades and twist angle. The aim of the work is to study the influence of the different designs on rotational speed and power of rotor in different wind speed.

Criterion of aerodynamic performance of large-scale offshore horizontal axis wind turbines

With the background of offshore wind energy projects,this paper studies aerodynamic performance and geometric characteristics of large capacity wind turbine rotors(1 to 10 MW) ,and the main characteristic parameters such as the rated wind speed,blade tip speed,and rotor solidity. We show that the essential criterion of a highperformance wind turbine is a highest possible annual usable energy pattern factor and a smallest possible dimension,capturing the maximum wind energy and producing the maximum annual power. The influence of the above-mentioned three parameters on the pattern factor and rotor geometry of wind turbine operated in China's offshore meteorological environment is investigated. The variation patterns of aerodynamic and geometric parameters are obtained,analyzed,and compared with each other. The present method for aerodynamic analysis and its results can form a basis for evaluating aerodynamic performance of large-scale offshore wind turbine rotors.

计及ROCOF与转子动能的风电机组自适应下垂控制策略

风电机组参与调频可提高风电并网系统的频率稳定性,但现有下垂控制难以兼顾频率响应特性和风机自身运行状态。为此,文中提出一种计及频率变化率(rate of change of frequency,ROCOF)与转子动能的自适应下垂控制策略,充分利用转子动能参与调频,确保风机稳定运行。首先,根据系统频率情况,将ROCOF划分区间,通过分段函数构建下垂系数与ROCOF的耦合函数,确保风电机组在扰动初期释放更多能量,提高风机对频率的支撑能力,减缓频率跌落速度。然后,引入转速影响因子,根据风机自身运行状态调整下垂系数,防止风机转子失速,避免频率二次跌落。最后,在MATLAB/Simulink平台上搭建风火联合系统仿真模型验证了所提控制策略有效性。仿真结果表明所提策略在保证风机转速稳定的同时,能有效利用风机转子动能改善系统频率响应特性。

Investigation of Load Prediction on the Mexico Rotor Using the Technique of Determination of the Angle of Attack

Blade element moment(BEM) is a widely used technique for prediction of wind turbine aerodynamics performance,the reliability of airfoil data is an important factor to improve the prediction accuracy of aerodynamic loads and power using a BEM code.The method of determination of angle of attack on rotor blades developed by SHEN,et al is successfully used to extract airfoil data from experimental characteristics on the MEXICO(Model experiments in controlled conditions) rotor.Detailed surface pressure and particle image velocimetry(PIV) flow fields at different rotor azimuth positions are examined to determine the sectional airfoil data.The present technique uses simultaneously both PIV data and blade pressure data that include the actual flow conditions(for example,tunnel effects),therefore it is more advantageous than other techniques which only use the blade loading(pressure data).The extracted airfoil data are put into a BEM code,and the calculated axial and tangential forces are compared to both computations using BEM with Glauert's and SHEN's tip loss correction models and experimental data.The comparisons show that the present method of determination of angle of attack is correct,and the re-calculated forces have good agreements with the experiment.

基于寻优算法的双馈风机变流器动态运行控制参数辨识

针对运行过程中双馈风机变流器控制参数难以获取的问题,提出了一种基于自适应混沌粒子群算法的转子侧变流器参数辨识方法。首先,基于机组实际运行下可量测电气量时间序列,建立双馈风机变流器控制系统离散化数学模型;然后,根据不同观测电气量下参数的轨迹灵敏度,对辨识难易程度进行分析;最后,利用自适应混沌粒子群算法对变流器PI控制参数进行辨识。仿真实验结果验证了所提出辨识方法的准确性与可行性。

风轮不平衡载荷下超大型风电机组叶片颤振极限研究

以IEA Wind 15 MW参考风电机组为研究对象,基于非线性时域气弹耦合分析工具,研究风剪切、偏航入流、质量不平衡3种不平衡载荷单一或共同作用时,超大型风电机组叶片的颤振极限。结果表明,单一不平衡载荷作用时,风剪切和±15°以内的偏航角会增大临界颤振速度,而质量不平衡会降低临界颤振速度,且质量偏重时颤振速度下降更加明显。3种不平衡载荷共同作用时,临界颤振速度的最大值和最小值都出现在剪切系数为0.3时;最大值总是在偏航角为非负值时取得,最小值在偏航角为-20°时取得;质量不平衡对临界颤振速度的影响与其单一作用时的规律一致。因此,在进行气弹稳定性分析时,应考虑多种风轮不平衡载荷共同作用,尤其是叶片质量偏重和偏航角度为-20°时这种最不利的情况。

串列不等直径水平轴风力机气动性能研究

为研究上游风力机叶轮直径增大和轮毂高度抬升对下游风力机气动性能影响,采用计算流体力学方法对串列水平轴风力机三维流场进行模拟,以揭示上游风力机叶轮尺寸增大和轮毂高度抬升对下游风力机气动性能影响规律。研究结果表明:增大上游风力机叶轮直径,会削减下游临近机组输出功率,增加机组在低频,1倍、2倍、3倍轴频推力脉动,增大机组疲劳载荷;随着风力机间距的增加,增大叶轮直径对12D范围外机组输出功率影响可忽略不计,但机组疲劳载荷在低频和1倍轴频仍有明显的增大。抬高上游机组轮毂高度,机组较近时,可使下游风力机避开一部分尾流,显著提高下游风力机的输出功率,但也会使风力机叶轮在旋转一周过程中产生较大的叶片推力脉动;当风力机间距较远时,抬高塔架高度有利于尾流恢复,进而提高下游机组输出功率,降低机组疲劳载荷。

双馈异步风力发电机转子匝间短路故障振动特性分析

针对双馈异步风力发电机转子匝间短路的故障振动机理尚不明确且无法为故障诊断提供理论依据的问题,开展了双馈异步风力发电机转子匝间短路故障振动特性分析.首先,结合有限元仿真及解析推导,分析转子匝间短路下双馈异步风力发电机的气隙磁密规律,得到转子所受的不平衡磁拉力;然后,考虑转子不平衡磁拉力的情况下构建双馈异步风力发电机转子-轴承系统非线性动力学模型,利用非线性动力学仿真获取转子匝间短路故障下系统的振动仿真信号;最后,在双馈异步风力发电机故障模拟实验台上进行转子匝间短路故障实验,利用实验分析验证非线性动力学仿真结果的有效性.非线性动力学仿真及实验分析结果均表明,转子匝间短路故障下双馈异步风力发电机转子-轴承系统振动信号的频谱存在转频的谐波成分,通过检测转频的谐波分量可诊断双馈异步风力发电机转子匝间短路故障,有效揭示了双馈异步风力发电机转子匝间短路的故障振动机理.

离网型双馈风力发电机组控制策略研究

本研究首先分析了离网型风力发电机组的数学模型,以及转子侧变换器、定子侧变换器的数学模型。然后根据数学模型,在转子侧变换器推导了直接电压矢量控制,其控制目标为定子侧的输出电压的幅值与频率;在定子侧变换器推导了基于定子电压矢量定向的矢量控制,采用电压平方外环、电流内环的双环控制,其控制目标为直流母线电压。为验证该控制策略,搭建了仿真模型,仿真结果显示,该方法能够实现离网型双馈风力发电机组输出稳定的电压。

汽轮发电机转子匝间绝缘的检测方法分析

阐述转子匝间短路故障的分类,探讨匝间短路故障的检测方法,包括非在线检测方法中的直流电阻法、双开口变压器法、单开口变压器法,以及在线检测方法中的环流检测法、探测线圈法、行波法。

考虑RNA运行作用的近海风电结构主动质量阻尼器振动控制研究

由于风电塔上部的风轮-机舱组件(rotor-nacelle assembly, RNA)在运行状态中的非线性控制策略,风电塔顶加速度频响特征复杂,其中风轮3倍转频激励(3P)响应最为突出。考虑一种单自由度等效风电塔模型,通过OpenFAST软件确定RNA运行作用下的结构动力参数与气动荷载,开展了基于线性二次型调节(linear quadratic regulator, LQR)算法的主动质量阻尼器(active mass damper, AMD)对风电塔顶前后向加速度响应的控制研究,以被动调谐质量阻尼器(tuned mass damper, TMD)为对照考察了AMD的减振性能与控制特点。结果表明:在RNA运行作用下,AMD具有比TMD更好的控制表现,其控制作用可一定程度抑制3P频段的响应。

基于改进的信赖域模型管理技术识别风电转子系统不对中载荷

针对求解耗时的风电转子系统不对中载荷识别问题,提出基于改进的信赖域模型管理技术的识别算法。该算法将整个先验分布空间的不对中载荷识别问题转化为一系列信赖域上的近似优化问题,通过区域遗传智能采样技术采集样本,加强径向基函数构建代理模型,再采用遗传算法进行近似优化。通过每个信赖域上的最小目标函数和近似优化结果确定信赖度和下代域的中心、半径,进而不断地缩放、平移信赖域,来保证获得与真实模型一致的不对中载荷。通过四种方法对比表明该方法样本遗传策略,遗传落在下代信赖域空间上的样本,减少实验设计样本个数而提高效率;最小目标函数作为信赖中心调整提高了关键区域代理模型的精度而加快收敛,降低了对代理模型精度的依赖。

双转子风力机气动建模与控制仿真研究

为研究双转子风力机的气动特性和风能利用率,基于NREL 5 MW和WindPACT 1.5 MW风力机转子,搭建了双转子风力机模型,并进行了功率优化控制仿真。首先,建立了双转子风力机的气动、塔影效应、传动链与发电机模型,在Matlab/Simulink中搭建了双转子风力机模型。其次,基于自由涡尾迹法(Free Vortex Wake, FVW)对双转子风力机流场进行了不同风况下的仿真计算。最后,基于模糊控制设计了双转子风力机功率控制策略,并与PID控制策略进行了比较。结果表明:与CFD相比,FVW计算的流场风速相对误差绝对值小于10%,能够快速动态计算双转子风力机的流场分布;对比不同风况,双转子风力机的风能利用率可提高约24%;模糊控制策略在双转子风力机功率动态响应和抑制功率波动方面改善明显。