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。     

基于改进最小方差法的风电机组变桨距控制

针对额定风速以上风电机组变桨距控制问题,提出了一种基于改进最小方差法的风电机组变桨距控制策略。该方法将延长预测步长思想,时变砺设计和柔化控制作用相结合,能够在突变过程初期,限制控制幅度,在控制后期能够加快收敛速度。同时与递推最小二乘辨识方法结合,用于额定风速以上风电机组变桨距控制系统。通过算例仿真表明,与传统的最小方差控制和PI控制方法相比,该方法能够使得系统响应迅速,在额定风速以上快速改变桨距角,保证了风电机组恒功率输出运行。     

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.     

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.     

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 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.     

基于神经元PID的风力发电机组独立变桨控制

针对传统统一变桨距控制策略存在的不足,基于风力机空气动力学原理,提出了基于神经元PID的独立变桨距控制策略,将测量的桨叶根部My方向载荷通过神经元PID控制算出d、q轴的桨距角,经反Park变换得到3个桨叶的附加桨距角,将其与统一变桨距角相加作为独立桨距角的设定值。并借助Fast软件平台以2MW变速变桨风力发电机组为例,仿真比较了独立变桨距控制策略与统一变桨距控制策略。结果表明,独立变桨距控制策略能有效保证在额定转速下机组输出功率稳定,且能有效降低风力发电机组各零部件的疲劳载荷。     

Optimal blade pitch control with realistic preview wind measurements

In above‐rated wind speeds, the goal of a wind turbine blade pitch controller is to regulate rotor speed while minimizing structural loads and pitch actuation. This controller is typically feedback only, relying on a generator speed measurement, and sometimes strain gages and accelerometers. A preview measurement of the incoming wind speed (from a turbine‐mounted lidar, for example) allows the addition of feedforward control, which enables improved performance compared with feedback‐only control. The performance improvement depends both on the amount of preview time available in the wind speed measurement and the coherence between the wind measurement and the wind that is actually experienced by the turbine. We show how to design a collective‐pitch optimal controller that takes both of these factors into account. Simulation results show significant improvement compared with baseline controllers and are well correlated with linear model‐based results. Linear model‐based results show the benefit of preview measurements for various preview times and measurement coherences. Copyright © 2016 John Wiley & Sons, Ltd.     

Simulating Feedback Linearization control of wind turbines using high‐order models

As wind turbines are becoming larger, wind turbine control must now encompass load control objectives as well as power and speed control to achieve a low cost of energy. Due to the inherent non‐linearities in a wind turbine system, the use of non‐linear model‐based controllers has the potential to increase control performance. A non‐linear feedback linearization controller with an Extended Kalman Filter is successfully used to control a FAST model of the controls advanced research turbine with active blade, tower and drive‐train dynamics in above rated wind conditions. The controller exhibits reductions in low speed shaft fatigue damage equivalent loads, power regulation and speed regulation when compared to a Gain Scheduled Proportional Integral controller, designed for speed regulation alone. The feedback linearization controller shows better rotor speed regulation than a Linear Quadratic Regulator (LQR) at close to rated wind speeds, but poorer rotor speed regulation at higher wind speeds. This is due to modeling inaccuracies and the addition of unmodeled dynamics during simulation. Similar performance between the feedback linearization controller and the LQR in reducing drive‐train fatigue damage and power regulation is observed. Improvements in control performance may be achieved through increasing the accuracy of the non‐linear model used for controller design. Copyright © 2009 John Wiley & Sons, Ltd.     

The Design of closed loop controllers for wind turbines

This article reviews the design of algorithms for wind turbine pitch control and also for generator torque control in the case of variable speed turbines. Some recent and possible future developments are discussed. Although pitch control is used primarily to limit power in high winds, it also has a significant effect on various loads. Particularly as turbines become larger, there is increasing interest in designing controllers to mitigate loads as far as possible. Torque control in variable speed turbines is used primarily to maximize energy capture below rated wind speed and to limit the torque above rated. Once again there are opportunities for designing these controllers so as to mitigate certain loads. In addition to improving the design of the control algorithms, it is also possible to use additional sensors to help the controller to achieve its objectives more effectively. The use of additional actuators in the form of individual pitch controllers for each blade is also discussed. It is important to be able to quantify the benefits of any new controller. Although computer simulations are useful, field trials are also vital. The variability of the real wind means that particular care is needed in the design of the trials. Copyright © 2001 John Wiley & Sons, Ltd.     

Modelling–based approach for digital control design for nonlinear WECS in the power system

The case has been established that the wind power plant must be treated as an integral part of the electric system, thereby constituting the wind energy conversion system. Recent advancement in size and technology of wind turbines requires sophisticated control systems to effectively optimize energy conversion and enhance grid integration. As a first step toward controller design, modelling has become a prerequisite. This paper explores controller design based on modelling the wind speed as a stochastic process, and the wind turbine as a multi‐mass system with a soft shaft linking the turbine with the doubly fed induction generator. A control strategy incorporating a linear quadratic Gaussian (LQG) that relies on state estimation for full‐state feedback is proposed to augment a linear controller for generator torque control. The control objectives are to reduce stresses on the drivetrain and to ensure operation geared toward optimal power conversion. This study focuses on above‐rated wind speeds, and the LQG's main purpose is to add damping to the drivetrain, thereby minimizing cyclic fatigue, while a pitch control mechanism prevents rotor overspeed, thereby maintaining rated power. Simulations show the efficacy of the proposed paradigm in meeting the control objectives. Copyright © 2009 John Wiley & Sons, Ltd.     

风力发电机组的自适应转矩控制及载荷优化

针对变速变桨风力发电机组(variable speed variable pitch,VSVP)如何在低风速时最大限度捕获风能以及在额定风速以上降低传动链载荷进行研究。低风速时在研究了传统风能追踪控制策略的基础上,文中提出通过改变最优增益系数来追踪最佳风能利用系数的自适应转矩控制策略。同时针对风力发电机组传动链的扭转振动,提出了基于发电机转速反馈滤波的转矩纹波控制方式。以2MW变速变桨风力发电机组为验证对象,基于Blade软件平台对所采用的控制策略进行仿真研究。结果表明：所提出的自适应转矩控制策略能够更好的追踪最大功率点,同时采用转矩纹波能够降低传动链载荷     

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.     

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.     

Variable structure strategy to avoid amplitude and rate saturation in pitch control of a wind turbine

This work proposes the application of a recent compensation technique for input constraints avoidance to the pitch control of a wind turbine. The pitch angle actuators commonly present a hard limit on their rate of change together with the natural amplitude saturation, and a dynamics during their unconstrained operation that can be modeled as a first-order linear system. This dynamic behavior of the pitch actuator requires a particular design of the compensation method, which is based on variable structure systems to avoid both amplitude and rate input saturation by means of an auxiliary loop. The developed methodology reduces the pitch actuator activity necessary to regulate the generated power around its nominal value when facing sudden wind gusts. Another interesting feature of the proposal is that it allows the operator to fix conservative bounds for the actuator speed operation in order to increment the structural robustness of the wind turbine and to extend in this way the service life of the energy system. The effectiveness of the proposed strategy is evaluated by simulation results in an autonomous wind energy conversion system for water pumping with a brushless double feed induction generator (BDFIG).     

基于激光雷达的风力机分离测风独立变桨控制策略

在基于叶片根部载荷的PID独立变桨控制的基础上,引入激光雷达并提出优化的独立变桨控制方法.利用激光雷达可重建风力机前方风场信息的特点,对风力机前方风速进行提前测量.提出并使用统一风演化模型对所测数据进行二次处理,得到更贴近实际的叶轮中心风速,进一步使用所提出的分离测风方法对叶根载荷进行提前计算,根据载荷的计算值进行独立...     

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。     

MPC framework for constrained wind turbine individual pitch control

The reduction of structural loads is becoming an important objective for the wind turbine control system due to the ever‐increasing specifications/demands on wind turbine rated power and related growth of turbine dimensions. Among various control algorithms that have been researched in recent years, the individual pitch control has demonstrated its effectiveness in wind turbine load reduction. Since the individual pitch control, like other load reduction algorithms, requires higher levels of actuator activity, one must take actuator constraints into account when designing the controller. This paper presents a method for the inclusion of such constraints into a predictive wind turbine controller. It is shown that the direct inclusion of constraints would result in a control problem that is nonconvex and difficult to solve. Therefore, a modification of the constraints is proposed that ensures the convexity of the control problem. Simulation results show that the developed predictive control algorithm achieves individual pitch control objectives while satisfying all imposed constraints.     

Real-time rotor effective wind speed estimation based on actuator disc theory: Design and full-scale experimental validation

The use of state estimation techniques offers a means of inferring rotor effective wind speed from standard measurements of wind turbines. Typical wind speed estimators rely upon a pre-computed quasi-steady aerodynamic mapping, which describes the relationship between pitch angle and tip-speed ratio and the power coefficient. In practice, the static mapping does not capture the influence of turbine structural dynamics and atmospheric turbulence, inevitably resulting in poor performance of the wind speed estimation. In addition, the turbine aerodynamic properties might not be easily accessible. Thus, this paper presents a rotor effective wind speed estimation method that obviates the requirement for prior knowledge of turbine power coefficients. Specifically, the proposed method exploits a simple actuator disc model, where the aerodynamic power and thrust coefficients can be characterized in terms of axial induction factors. Based on this insight and standard turbine measurements, real-time estimation of rotor effective wind speed and axial induction factors can then be achieved using a simplified turbine drive-train model and an extended Kalman filter. In addition, the actuator disc model can be updated easily over time by calibrating solely two correction factors. Thus, the proposed algorithm presents an alternative for estimating the rotor effective wind speed, which is valuable for numerous applications, for example, LiDAR-assisted control and coherence studies.