基于模糊控制的风电机组独立变桨距控制

在额定风速以上时,通常采用变桨距控制技术调节大型风电机组来稳定其输出功率.由于风力发电系统的数学模型具有高度非线性、多变量、强耦合的特点,风速又具有多变性,因此文章在分析传统的PID变桨距控制技术优缺点的基础上,提出了基于三维模糊自适应PID控制的独立变桨距控制技术,并且引入风速的模糊前馈控制技术.对1 MW风电机组进行仿真,结果表明,在额定风速以上时,该方法不仅能稳定风电机组的输出功率,而且可以减小桨叶的拍打振动.     

风电机组变速与变桨距控制过程中的动力学问题研究

讨论了额定风速以下的变速运行控制和额定风速以上的变桨距控制以及变速与变桨距两种控制策略的相互耦合关系;分析了风电机组主要部件包括叶轮、传动系统、塔架的各阶振动模态以及它们之间的相互影响力;提出了转矩控制对传动系统扭转振动和变桨距控制对塔架前后振动的影响力及控制方案;应用BLADED和MAT- LAB软件对主要控制环节进行设计及参数调整,并对机组的控制效果进行仿真。结果表明,所采用的控制策略和控制算法能够满足控制要求,并能有效地解决动力学问题。     

一种直驱永磁风电机组的减载调频控制策略

文章针对风电并网容量增加导致系统调频能力不足的问题,提出了一种超速和变桨距协调的减载调频控制策略。首先给出了低、中、高3种风速模式的判定方法,然后通过设置初始功率跟踪曲线系数和调节桨距角实现直驱永磁风电机组的减载运行。在频率控制中,优先采用超速控制,当转速达到额定转速时,再启用变桨距控制,并且变桨距控制可分为低、中、高3种风速控制模式。仿真分析表明,基于所提减载调频控制策略,直驱永磁风电机组能在全风速范围预留一定比例的备用容量,实现双向频率控制,并能改善系统频率的暂态和稳态响应。     

基于风轮气动特性的风力机变桨优化控制策略研究

当风速大于额定风速时,风电机组通过控制变桨机构调整桨距角来减小风能捕获,从而使机组的输出功率保持在额定功率附近。变桨系统一般采用PI(比例积分)控制算法,但由于风轮气动转矩与风速、风轮转速、桨距角呈高次复杂非线性关系,单一控制参数的变桨控制器难以满足风电机组在额定风速以上的运行性能要求。为了解决单一变桨控制性能不足的问题,提出一种基于风轮气动特性的风力机变桨优化控制策略,该策略通过测量桨距角当前值来动态调整变桨控制器参数,可有效提升变桨系统随风动作连续性,减小由变桨控制引起的转速与功率波动,削减机组由变桨动作引起的动态载荷。     

改进灰狼优化算法在变桨距自抗扰控制中的应用

风电机组模型的不确定性以及风等外部干扰严重影响风电机组输出功率的稳定性,因此,将自抗扰控制器(ADRC)引入到风电机组变桨距控制中。当风速高于额定风速时,通过自抗扰变桨距控制策略有效调节桨距角,保证风电机组输出功率的稳定性。但ADRC参数繁多,仅靠专家经验进行整定比较困难。因此,文章提出将改进灰狼优化算法应用到ADRC中,完成参数的自寻优整定过程。仿真结果证明,经改进灰狼优化算法进行参数整定后的变桨距自抗扰控制系统能够对桨距角进行精确调整,并将输出功率快速稳定到额定值附近,具有较快的响应速度以及较好的抗扰动能力。     

基于改进共轭梯度优化BP神经网络的风电机组变桨距控制

根据共轭梯度算法和传统BP神经网络的变桨距控制器的原理,针对兆瓦级风电机组变桨距控制设计了一种改进共轭梯度优化BP神经网络的变桨距PID参数自整定控制器,此控制器采用改进共轭梯度法修正BP神经网络的权值和阈值,实现BP神经网络变桨距PID控制器的在线整定。在Matlab/Simulink中仿真,仿真结果表明,采用此变桨距控制器可以在额定风速之上快速响应,在相同风速状况下使发电机桨距角调节命令更加准确,风轮转速更加平稳,输出功率维持在额定功率附近,取得了很好的变桨距控制效果。     

基于LQR方法的风电机组变桨距控制的动态建模与仿真分析

为了获得更好的变桨距控制效果,将扰动校正LQR(Linear Quadratic Regulator)应用到风电机组变桨距控制中,该方法通过设计扰动状态观测器估计出作为扰动量的风速,在输入量中加入一个反馈量来消除风速产生的扰动影响,然后根据LOR控制理论,计算出状态反馈矩阵.建立了风电机组的动态模型,并根据动态模型在Mat-lab7.1/simulink环境下进行了仿真.仿真结果表明,基于扰动校正的LQR控制方法超调小,变桨距执行机构疲劳度小,具有良好的动态性能.该方法易于工程实现,适用于变桨距控制系统.     

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。     

参与电网调频的风电机组线性变参数变桨控制策略

风电机组参与调频时其输出功率的调整将改变风电机组变桨动作的风速范围,同时由于桨距角调节气动功率的灵敏度随风况变化,使得传统PI变桨控制难以适用于风电机组参与调频时的复杂工况,出现风电机组转速振荡问题。提出一种基于线性变参数(Linear Parameter Varying, LPV)系统的风电机组变桨控制方法,对风电机组模型进行线性化,根据风速和桨距角的变化范围进行凸分解,得到其具有四面体结构的LPV模型,通过求解不同平衡点处的线性矩阵不等式(Linear Matrix Inequality, LMI)设计出相应的变桨控制器。仿真结果表明:与传统PI变桨控制相比,LPV变桨控制能有效减小转速的波动,降低低速轴载荷以及减小桨距角的波动程度,验证了该控制策略的有效性和先进性。     

基于LMI的5MW海上风力发电机组载荷控制技术研究

当风速大于额定风速时,通过调节桨距角可以限制输入气动功率和风轮转速,使等效在低速轴上的发电机转速更好地跟踪风轮转速,从而减小低速轴扭矩,实现风机叶片、塔筒和传动链的动态载荷控制。文章基于线性矩阵不等式(Linear Matrix Inequality,LMI)设计多目标鲁棒H_∞/H_2状态反馈变桨距控制器。设计变桨距控制器时充分考虑了海上机组的运行环境,分析了海浪对机组产生的影响,控制目标选取机组的功率和机组的关键部位疲劳载荷,在保证功率稳定输出、减小功率波动同时,减小机组载荷。使用MATLAB和FAST软件进行联合仿真,仿真结果表明新型控制策略可以有效平稳风电机组输出功率并降低机组载荷,实现了优化H_∞/H_2鲁棒控制性能。     

Power regulation in pitch-controlled variable-speed WECS above rated wind speed

In medium to large scale wind energy conversion systems (WECS), the control of the pitch angle of the blades is an usual method for power regulation above rated wind speed. However, limitations of the pitch actuator have a marked influence on the regulation performance. In variable-speed mode, the control of the generator torque is able to reduce the effects of the pitch actuator limitations. Nevertheless, in this case the system is multiple-input multiple-output (MIMO) and then the control design results more complex. In this situation advance control techniques, such as optimal control, are an interesting option for a systematic controller design. This work analyzes variable-pitch power regulation above rated wind speed in the context of optimal control. The analysis is approached from a new point of view in order to establish a clear connection between the choice of the optimization criteria and the compromise between power regulation and pitch actuator limitations.     

Output power leveling of wind turbine Generator for all operating regions by pitch angle control

Wind energy is not constant and windmill output is proportional to the cube of wind speed, which causes the generated power of wind turbine generators (WTGs) to fluctuate. In order to reduce fluctuation, different methods are available to control the pitch angle of blades of windmill. In a previous work, we proposed the pitch angle control using minimum variance control, and output power leveling was achieved. However, it is a controlled output power for only rated wind speed region. This paper presents a control strategy based on average wind speed and standard deviation of wind speed and pitch angle control using a generalized predictive control in all operating regions for a WTG. The simulation results by using actual detailed model for wind power system show the effectiveness of the proposed method.     

大型风力发电机组独立桨叶控制系统

设计出独立桨叶控制系统的机构方案，依据空气动力学分析，提出模糊控制结合以桨叶空间方位角作为主体因素的加权系数的控制策略，建立了系统模型，仿真结果表明，在风速高于额定风速时，作用在桨叶上的负载波动大为减小，输出功率维持在额定功率附近。     

An investigation of variable power collective pitch control for load mitigation of floating offshore wind turbines

This paper investigates the loads on offshore floating wind turbines and a new control method that can be used to reduce these loads. In this variable power collective pitch control method, the rated generator speed, which is the set point that the collective pitch control attempts to drive the actual generator speed towards, is no longer a constant value but instead is a variable that depends on the platform pitch velocity. At a basic physical level, this controller achieves the following: as the rotor of a floating turbine pitches upwind, the controller adjusts so as to extract more energy from the wind by increasing the rated generator speed and thus damps the motion; as the rotor pitches downwind, less energy is extracted because the controller reduces the rated generator speed and again damps the motion. This method is applied to the NREL 5 MW wind turbine model, in above rated conditions where the platform motion is most problematic. The results indicate significant load reductions on key structural components, at the expense of minor increases in power and speed variability. The loads on the blades and tower are investigated more generally, and simple dynamic models are used to gain insight into the behavior of floating wind turbine systems. It is clear that for this particular design, aerodynamic methods for reducing platform motion and tower loads are likely inadequate to allow for a viable design, so new designs or possibly new control degrees of freedom are needed. Copyright © 2012 John Wiley & Sons, Ltd.     

An investigation of variable power collective pitch control for load mitigation of floating offshore wind turbines

This paper investigates the loads on offshore floating wind turbines and a new control method that can be used to reduce these loads. In this variable power collective pitch control method, the rated generator speed, which is the set point that the collective pitch control attempts to drive the actual generator speed towards, is no longer a constant value but instead a variable that depends on the platform pitch velocity. At a basic physical level, this controller achieves the following: as the rotor of a floating turbine pitches upwind, the controller adjusts so as to extract more energy from the wind by increasing the rated generator speed and thus damps the motion; as the rotor pitches downwind, less energy is extracted because the controller reduces the rated generator speed and again damps the motion. This method is applied to the NREL 5 MW wind turbine model, in above‐rated conditions where the platform motion is most problematic. The results indicate significant load reductions on key structural components, at the expense of minor increases in power and speed variability. The loads on the blades and tower are investigated more generally, and simple dynamic models are used to gain insight into the behavior of floating wind turbine systems. It is clear that for this particular design, aerodynamic methods for reducing platform motion and tower loads are likely inadequate to allow for a viable design, and so new designs or possibly new control degrees of freedom are needed. Copyright © 2012 John Wiley & Sons, Ltd.     

风电机组电液比例变桨距技术研究

针对风力机功率控制的重要性,设计了电液比例变桨距执行机构,并结合风力机设计软件Bladed组建成半物理仿真试验台。在此试验台上对提出的分段PID变桨距控制算法以及变速恒频和变桨距切换设定的控制策略进行试验研究。试验结果表明在风速高于额定值时,通过分段PID变桨距控制发电机输出功率稳定性高于常规PID,当风速在额定值左右变化时,变桨距和变速恒频切换正常,满足功率控制和最大风能捕获的要求。     

Model predictive control of a wind turbine using short‐term wind field predictions

As wind turbines become larger and hence more flexible, the design of advanced controllers to mitigate fatigue damage and optimise power capture is becoming increasingly important. The majority of the existing literature focuses on feedback controllers that use measurements from the turbine itself and possibly an estimate or measurement of the current local wind profile. This work investigates a predictive controller that can use short‐term predictions about the approaching wind field to improve performance by compensating for measurement and actuation delays. Simulations are carried out using the FAST aeroelastic design code modelling the NREL 5 MW reference turbine, and controllers are designed for both above rated and below rated wind conditions using model predictive control. Tests are conducted in various wind conditions and with different future wind information available. It is shown that in above rated wind conditions, significant fatigue load reductions are possible compared with a controller that knows only the current wind profile. However, this is very much dependent on the speed of the pitch actuator response and the wind conditions. In below rated wind conditions, the goals of power capture and fatigue load control were considered separately. It was found that power capture could only be improved using wind predictions if the wind speed changed rapidly during the simulation and that fatigue loads were not consistently reduced when wind predictions were available, indicating that wind predictions are of limited benefit in below rated wind conditions. Copyright © 2012 John Wiley & Sons, Ltd.     

Modeling,simulation and control of a wind turbine with a hydraulic transmission system

A complete mathematical model of a hydraulic transmission concept for use in wind turbines is presented. The hydraulic system transfers the power from the nacelle to ground level. The main focus has been to develop a model that takes into account the most important dynamics affecting the wind turbine and the hydraulic transmission system involved, such that the model can be used to analyze the dynamic feasibility of a hydraulic transmission concept. Further, dynamic analysis of a hydraulic transmission system for wind turbines is investigated. The nonlinear dynamic model is developed in MATLAB Simulink. Analytical calculation of natural periods of a linearized model corresponds well with simulations of the overall system. A valve control system is proposed to reduce pressure and power fluctuations at operation both below and above the rated wind speed for the wind turbine. Further, a blade pitch control system based on an aerodynamic power estimator is proposed for operation above the rated wind speed. System simulations for one case below and one case above the rated wind speed show that the dynamic response of the overall system is stable and that the wind turbine variables are within typical ranges for conventional variable speed wind turbines with mechanical transmission. Copyright © 2012 John Wiley & Sons, Ltd.     

风电机组的功率模糊控制系统研究

变桨距风电机组是一个高阶、非线性、强耦合、多变量时变的系统,其控制系统是综合性控制系统。在额定风速以上采用功率反馈的模糊控制策略,通过对桨距角的控制,改变气流对叶片的攻角,使风力机吸收的风能在一个相对的稳定值,从而实现发电机恒功率输出。仿真结果表明,模糊控制方法更具优越性,在风力发电系统中能取得较好的控制效果,系统具有较强的抗扰性和快速性。