Design of a wind turbine pitch angle controller for power system stabilisation

The design of a PID pitch angle controller for a fixed speed active-stall wind turbine, using the root locus method is described in this paper. The purpose of this controller is to enable an active-stall wind turbine to perform power system stabilisation. For the purpose of controller design, the transfer function of the wind turbine is derived from the wind turbine's step response. The performance of this controller is tested by simulation, where the wind turbine model with its pitch angle controller is connected to a power system model. The power system model employed here is a realistic model of the North European power system. A short circuit fault on a busbar close to the wind turbine generator is simulated, and the dynamic responses of the system with and without the power system stabilisation of the wind turbines are presented. Simulations show that in most operating points the pitch controller can effectively contribute to power system stabilisation.     

大型风力发电机组独立变桨多目标控制

为限制大型风力发电机组在高风速时的功率输出和风力机气动载荷,首先,采用PID控制,设计独立变桨距功率和扭矩外环控制;其次,引入不依赖于系统数学模型的无模型控制,设计桨叶挥舞弯矩内环控制;最后,以外环控制输出桨距角为参考量,内环无模型控制期望桨距角为反馈量,利用PID控制,给出3个桨叶桨距角最终参考值。利用Matlab/Simulink仿真软件,搭建了3 MW风电机组仿真平台,仿真结果表明,所设计的独立变桨距多目标控制,能够完成在高风速时保持风力机组输出功率恒定、平衡3个桨叶所受扭矩以及兼顾3个桨叶所受挥舞弯矩的多目标控制任务。     

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.     

分散式风力发电机组的电压控制

风电的分散式开发不同于大规模开发和分布式开发,由于分散风电靠近负荷中心,直接接入配电网,且不加装无功补偿调节装置SVC,配网中较大的电压波动给分散风电的并网运行带来影响。文章讨论了配网对分散风电的电压控制特点和要求,结合风电机组无功控制能力,并推导出满足配网电压调节要求的风电机组无功控制范围和对机组设备的要求。     

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.     

Sensor comparison study for load alleviating wind turbine pitch control

As the size of wind turbines increases, the load alleviating capabilities of the turbine controller are becoming increasingly important. Load alleviating control schemes have traditionally been based on feedback from load sensor; however, recent developments of measurement technologies have enabled control on the basis of preview measurements of the inflow acquired using, e.g., light detection and ranging. The potential of alleviating load variations that are caused by mean wind speed changes through feed‐forward control have been demonstrated through both experiments and simulations in several studies, whereas the potential of preview control for alleviating the load variations caused by azimuth dependent inflow variations is less described. Individual or cyclic pitch is required to alleviate azimuth dependent load variations and is traditionally applied through feedback control of the blade root loads. In many existing studies, the performance of an advanced controller is compared with the performance of a simpler controller. In this study, the effect of three measurement types on the load alleviating performance of the same cyclic pitch control design is studied. By using a baseline cyclic pitch controller as test bench, the effect of the different measurement types on the controller performance can be assessed independent of control design. The three measurement types that are considered in this study are as follows: blade root out‐of‐plane bending moment, on‐blade measurements of angle of attack and relative velocity at a radial position of the blades, and upstream inflow measurements from a spinner mounted light detection and ranging (LiDAR) sensor that enables preview of the incoming flow field. The results show that for stationary inflow conditions, the three different measurement types yield similar load reductions, but for varying inflow conditions, the LiDAR sensor‐based controller yields larger load reductions than the two others. The results also show that the performance of the LiDAR sensor‐based controller is very sensitive to uncertainties relating to the inflow estimation. Copyright © 2013 John Wiley & Sons, Ltd.     

变速变桨风力发电机组的优化控制

提出了大型变速变桨风力发电机组在不同控制阶段的优化控制策略。在低风速时,采用自适应转矩控制方式,实现机组的变速运行,追踪最佳风能利用系数。在额定风速以上时,为了解决传统桨距控制方式系统超调量大的问题,提出了一种新型气动转矩观测器,并将气动转矩与发电机转矩偏差输入控制器。通过Bladed外部控制器模块编程并进行仿真,结果表明,所提出的控制策略能够更好地追踪最大功率点,并改善桨距控制效果,稳定功率输出。     

Determining wind turbine power curves based on operating conditions

The relation between wind speed and electrical power—the power curve—is essential in the design, management and power forecasting of a wind farm. The power curve is the main characteristic of a wind turbine, and a procedure is presented for its determination, after the wind turbine is installed and in operation. The procedure is based on both computational and statistical techniques, in situ measurements, nacelle anemometry and operational data. This can be an alternative or a complement to procedures fully based on field measurements as in the International Electrotechnical Commission standards, reducing the time and costs of such practices. The impact of a more accurate power curve was measured in terms of the prediction error of a wind power forecasting system over 1 year of operation, whereby the methodology for numerical site calibration was presented and the concepts of ideal power curve and nacelle power curve introduced. The validation was based on data from wind turbines installed at a wind farm in complex topography, in Portugal, providing a real test of the technique presented here. The contribution of the power curve to the wind power forecasting uncertainty was found to be from 10% to 15% of the root mean square error. Copyright © 2013 John Wiley & Sons, Ltd.     

基于额定风速以上的风力机变桨控制研究

变桨控制系统是变速变桨风力发电机组的重要组成部分,它不仅关系到大型MW级风力发电机组的安全运行,而且能控制风力发电机组,使其吸收更多的风能。文章基于2.0 MW变速变桨风力发电系统,采用PI控制策略,提出了增益调度控制算法,计算了PI增益随风速变化而变化的数值。通过调用线性化结果文件,设计了风力发电机组控制器回路,得出了满意的响应结果。最后基于GL规范,在湍流风的情况下对关键零部件是否加控制策略所得到的载荷进行了对比,结果显示关键零部件的载荷有显著降低,满足控制策略设计的要求。     

风力发电系统权系数独立变桨距矢量控制

风电系统具有多变量、非线性以及不确定等特点,为了减小叶片不平衡载荷造成的机组疲劳和振动,在2 MW风力发电系统中采用了基于权系数的独立变桨距矢量控制。在MATLAB软件中建立机组的数学模型,与统一变桨距系统的控制效果进行比较,通过仿真验证了权系数独立变桨距矢量控制方案的合理性和优越性。     

A variable speed wind turbine power control

To optimize the power in a wind turbine, the speed of the turbine should be able to vary with the wind speed. A simple control scheme is proposed that will allow an induction motor to run a turbine at its maximum power coefficient. The control uses a standard V/Hz converter and controls the frequency to achieve the desired power at a given turbine speed     

Output power control for large wind power penetration in small power system

Nowadays, wind turbine generator (WTG) is increasingly required to provide control capabilities regarding output power. Under this scenario, this paper proposes an output power control of WTG using pitch angle control connected to small power systems. By means of the proposed method, output power control of WTG considering states of power system becomes possible, and in general both conflicting objectives of output power leveling and acquisition power increase are achieved. In this control approach, WTG is given output power command by fuzzy reasoning which has three inputs for average wind speed, variance of wind speed, and absolute average of frequency deviation. Since fuzzy reasoning is used, it is possible to define output power command corresponding to wind speed condition and changing capacity of power system momentarily. Moreover, high performance pitch angle control based on output power command is achieved by generalized predictive control (GPC). The simulation results by using actual detailed model for wind power system show the effectiveness of the proposed method.     

Robust pitch controller for output power levelling of variable-speed variable-pitch wind turbine generator systems

A robust pitch (RP) controller for variable-speed variable-pitch wind turbine generator systems (VSVPWTGS) is presented. The controller can not only level the wind energy conversion but also be applicable in a wide wind speed region even subject to large parametric or non-parametric disturbances. VSVP-WTGS consists of multi-subsystems with different time scales. The dominant `slow? dynamics are non-affine and high nonlinear. By considering `fast? subsystems as perturbations to the `slow? one, the dynamics of VSVP-WTGS can be represented by a nominal model and an error one. The RP controller is composed of a nominal inverse-system controller and a robust compensator. With the nominal inverse-system controller, the nominal closed-loop system can track its reference dynamics. With the robust compensator, turbine parameter uncertainties and non-parametric perturbations are tolerated. The performance of the RP controller is confirmed through theoretical analyses and computer simulations. Results show that RP controller can operate in a wider wind speed region robustly compared with a proportional-integral-derivative controller. Compared with other nonlinear controllers, the RP controller is simpler and can be more easily extended to other kinds of WTGS.     

New strategy of pitch angle control for energy management of a wind farm

In this paper, we are interested in a Wind Energy Conversion System (WECS) based on a Permanent Magnetic Synchronous Generator (PMSG). The studied WECS is made by the association of three aerogenerators. The objective of this work is to investigate a new strategy of pitch angle control to ensure a balance between the produced energy and the demanded one by the loads. The control strategy of the wind farm is composed of two parts: a local control according to the characteristics of each wind turbine « Pitch control » to protect the turbines against mechanical failure in the event of wind gust and a global control according to the total power demand and the available wind power. This strategy leads to achieving power objectives (active and reactive power targets) and system constraints.     

风切变和塔影效应对风力机变桨距控制的影响分析

随着单台风力机功率的不断增大,变桨距控制对于风力机起动、制动性能的改善和对输出功率的稳定作用不断显现。单台风力机功率的不断增大也导致了塔架的增高和风轮直径的增大,风切变和塔影效应对风轮旋转平面风速分布产生的差异也不断变大。为了验证风速差异对变桨距控制的影响,建立了考虑风切变、塔影效应的风速模型以及基于叶素理论的风力机模型。采用1.5 MW风力机的数据进行研究,仿真验证表明,在集中变桨时,即使参考风速稳定,风速分布的差异也会使实际的风轮输出转矩产生脉动,桨距角产生周期性脉动,从而导致输出功率产生脉动,影响电能质量,同时叶片上产生不平衡的弯矩,增加了叶片的疲劳载荷,缩短了叶片的寿命。大型风力机应采用独立变桨技术来解决这些问题。     

基于有限时间控制的风电机组恒功率控制

针对风力机组的恒功率控制问题,提出了一种基于有限时间控制的方法,分别设计浆距角和转速控制器。通过调节桨距角,使风电场有功功率输出在有限时间内收敛到给定值;转速控制器对发电机的d,q轴电压Ud和Uq的控制,实现转矩响应和转速在有限时间内收敛到期望值。有限时间控制器可实现机组有功功率输出在有限时间内收敛到给定值。仿真结果表明,设计的控制方法是有效的。     

小型风力发电机的功率控制方法

将风力发电机叶片的功率一转速特性曲线划分为峰前、峰值和峰后3个区域.根据在各种风速下风力发电机叶片与电机的功率匹配特性,提出一种小型风力发电机的功率控制新方法;通过300 W/24 V风力发电机的设计和测试,验证了此功率控制方法的正确性和可行性.     

基于人工蜂群-RBF-PID的风力机液压变桨距控制系统设计

风力机液压马达变桨距系统存在高阶多耦合、不确定、非线性、难以控制的问题。为实现桨距角跟踪控制,文章通过动力学分析建立液压马达变桨距系统的数学模型,确定系统特性。根据液压马达变桨距系统原理,采用SimHydraulics建立液压马达变桨距系统仿真模型,设计基于人工蜂群算法结合RBF神经网络的PID控制器,并且采用自适应矩估计算法代替梯度下降法对PID参数进行在线优化。仿真结果表明,采用文章算法,系统响应快,桨距角跟踪精度高。     

Output control by hill-climbing method for a small scale wind power generating system

In this paper, a control method with which it is possible to extract wind energy effectively, even when the system characteristic is unknown, is suggested. With this control method, it is possible to follow the quasi-maximum output only by measurements of the load terminal voltage and current, which are relatively simple to measure with high accuracy. The hill-climbing method, among adaptive control methods, was adopted. For the purpose of confirming the effectiveness of this method, investigation by simulation using a model of a small-scale windmill generating system with a resistive load was conducted.     

Output power dispatch control for a wind farm in a small power system

Nowadays, a wind turbine generator (WTG) is required to provide control capabilities as the output power of WTG fluctuates. Under this scenario, this paper proposes an output power control method of a wind farm (WF) connected to a small power system using pitch angle control. In this control approach, the WF output power control is achieved by two control levels: central and local. In the central control, the WF output power command is determined by considering the frequency deviations and wind speeds using a fuzzy function. Then, the local output power commands for each of the WTGs are based on the proposed dispatch control. In the proposed dispatch control, the output commands of each WTG are determined by considering wind conditions for each of the WTGs. The simulation results by using an actual detailed model for the wind power system show the effectiveness of the proposed method. Copyright © 2010 John Wiley & Sons, Ltd.