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.     

风力发电机大风限速保护方法的研究

小型风力发电机面临的最大难题是其可靠性问题,即大风时的限速保护问题.从能量守恒的角度分析了利用风轮与发电机的功率匹配特性实现风力发电机限速保护的可行性.另外,设计了2台风轮与发电机具有不同匹配特性的300 W/26 V风力发电机,为了使其具有可比性,使用了同样型号的发电机.通过实验测试了风轮的机械输出特性、发电机在输出电压不同时的功率特性和整机的功率输出,实验结果表明,风速12 m/s以下时2台风力机输出功率基本相同,风速12 m/s以上时其中1台随着风速的增加功率不断增加,而另外1台随着风速的增加输出功率不再上升,甚至有点下降,与大风机功率特性相似.     

小功率风力充电控制器

介绍了一种小功率风力充电控制器。相对于传统的基于Boost变换器的充电方式,该控制器有效地降低了损耗,能更加充分地利用风能;在风速较低时,通过Boost斩波器将整流输出电压升至一定值,再送至后级电路;当风速较高时,切断Boost电路,将整流输出电压直接送到后级给蓄电池充电。经过300 W风力充电系统的实验,验证了其设计的正确性。     

低风速离网型风力发电机的叶片设计

根据内蒙古四子王旗某地2007年逐月平均风速表选取设计风速为6 m/s,根据某型号300 W交流永磁发电机的输出功率特性,利用Matlab编写的叶片优化设计程序,设计了300 W水平轴风力发电机叶片.通过风轮与发电机的匹配,调整叶片参数,使之在小风时具有较高的风能利用系数,提高风力机的效率,在大风时具有较低的风能利用系数,从而达到大风时限速保护的目的.     

升力型垂直轴风机的功率计算及功率输出特性的分析

借助Matlab软件的叶片受力情况对一个升力型垂直轴风机进行了仿真,利用仿真结果分析了实例的运行功率、转速和风速的关系,以及风力发电机与叶片匹配的情况。分析结果表明该升力型垂直轴风机的风能利用率较高,结构简单,适应性较强。     

基于有效风速估计的永磁直驱风力发电系统鲁棒控制研究

由于风力发电系统中的风速传感器存在测量误差,且风速测量值与施加在风机叶片上的有效风速不同,直接导致风力发电系统对风能利用率的降低。因此本文提出了一种基于滑模观测器的风机叶片风速有效值估计方法,在满足李雅普诺夫不等式的基础上设计了滑模观测器,从中提取出风力发电机转速和机械转矩的估计值。通过在线查表得到风机叶片上有效风速的估计值,将该估计值用于修正基于风速传感器的风力发电系统最大功率跟踪控制。仿真结果表明所提方法可有效提升风力发电系统对风能的利用率,具有一定的工程意义。     

1kW伞形风力发电机的设计与试验研究

功率调节是风力发电的关键技术之一,是保证风力发电机长期安全稳定运行的重要条件。伞形风力发电机是一种带有伞形功率调节机构的下风向风力发电机,叶片可做伞形收放动作。当风速超过额定风速时,伞形风力发电机可通过自身的调节机构,改变叶片的收缩角,使风轮扫掠面积减小,从而控制风力发电机功率输出,保证风力发电机的输出功率在额定值附近。后期试验证明,伞形风力发电机对功率输出有较好的调节作用。伞形风力发电机结构相对简单,对多变性天气适应能力较强,有广阔的应用前景。     

FD12-30 kW直驱永磁离网/并网型风力发电机组

介绍了FD12-30 kW直驱永磁离网/并网型风力发电机组的技术特点和性能参数.在3～25 m/s风速下,该机可连续发电运行,随着风速上升,发电机功率也提高,当风速达到11.5m/s以上时,风力发电机组输出功率为30 kW,最大输出功率为33 kW.文章着重阐述了其自动控制系统和使用操作.     

可扩展工作风速范围的风力发电机

针对现有小型风力发电机的有效发电时长短、可利用风速范围小的问题,提出一种可扩展工作风速范围的风力发电机.此风力发电机采用下风式结构辅以导流机舱罩聚风,轮毂与发电机轴采用发条柔性连接,风轮锥角可调.基于以上结构设计,实现降低切入风速提高切出风速,从而延长发电时间,提高风能利用率和设备利用率,增加发电量.文中以型号为FD2.2-300W小型风力发电机为例,进行技术参数的计算和对比,得出切出风速由20m/s提高到22m/s.该装置可作为现有小型风力发电机的升级替代产品.     

风力发电机风速放大器的研究与优化设计

研究设计了一种适用于风力发电机的风速放大器,该装置具有显著的聚风和提高风速作用。小于3m/s的风从进口端进入,经过聚风增速,在安装涡轮叶片的出口端可获得较大的风速,使风力发电机能够在风速较低的条件下正常启动和运行,提高单位面积风能利用率。文章以额定功率为1 k W的风力发电机组的风速放大器为例,对设计参数(倾斜角α,长度L,进口直径D)、出口端风速分布及变化规律、风速放大效果进行了研究和Fluent仿真优化。研究结果表明:风速放大器最高可提高风速5.32倍;在风速为0.56 m/s的条件下,风机即可启动;在风速为2 m/s时,风机可在额定功率下运行。     

Transient and dynamic control of a variable speed wind turbine with synchronous generator

In this article, a controller for dynamic and transient control of a variable speed wind turbine with a full‐scale converter‐connected high‐speed synchronous generator is presented. First, the phenomenon of drive train oscillations in wind turbines with full‐scale converter‐connected generators is discussed. Based on this discussion, a controller is presented that dampens these oscillations without impacting on the power that the wind turbine injects into the grid. Since wind turbines are increasingly demanded to take over power system stabilizing and control tasks, the presented wind turbine design is further enhanced to support the grid in transient grid events. A controller is designed that allows the wind turbine to ride through transient grid faults. Since such faults often cause power system oscillations, another controller is added that enables the turbine to participate in the damping of such oscillations. It is concluded that the controllers presented keep the wind turbine stable under any operating conditions, and that they are capable of adding substantial damping to the power system. Copyright © 2007 John Wiley & Sons, Ltd.     

风力发电液力机械调速装置系统动态特性研究

为实现2 MW风电机组的高效传动,通过实验方法测得导叶可调式双涡轮液力变矩器输出特性曲线,计算得到不同开度下涡轮力矩与涡轮转速的三次项系数关系式,推导风力发电液力调速系统行星轮系的数学模型,设计了模糊自整定PID控制器的控制系统,并对风电机组进行了动态仿真和实验对比研究。结果表明:数值计算功率数值均大于实验值,风速小于5 m/s时绝对误差较小,风速大于5 m/s时进入正常发电工况,最大误差为7%。     

Optimal gain-scheduled control of fixed-speed active stall wind turbines

For a smooth integration of large wind farms into the utility grids, the individual wind turbines must be able to achieve various power control objectives. In this context, the authors focus their attention on the control of fixed-speed active stall wind turbines. This sort of turbine includes a pitch servomechanism to induce stall on the blades, thereby having control on the output power. The authors develop a methodology to design optimal gain-scheduled pitch controllers valid for the whole operating region of the wind turbine. The proposed solution uses concepts of linear parameter-varying system theory. In addition to providing a formal framework for the control design, this theory guarantees stability and performance. Further, because of the similarities with Hαcontrol, the tools developed for the controller design are very familiar to the control community. The main features of the proposed controller are assessed by means of numerical simulations obtained for realistic wind speed profiles and power production demands.     

A novel line drop secondary voltage control algorithm for variable speed wind turbines

This paper addresses the design and implementation of the line drop secondary voltage control (LDSVC) for the doubly fed induction generator‐wind turbine (DFIG‐WT) complemented with reactive power allocation algorithm to achieve more efficient voltage regulation, reactive power compensation and to enhance the transient stability margin of the electric power system. The LDSVC is used to generate the local voltage reference, providing an improvement for overall voltage profile. The paper presents the influence of the integration of variable speed wind turbines‐based doubly fed induction generator (DFIG) while employing LDSVC for increasing the transient stability margin. This paper proposes an improved voltage control scheme, based on a secondary voltage controller complemented with an automatic gain controller (AGC). The scheme is applied to a wind energy system incorporating DFIG‐based wind turbines. The controller structure is developed and the performance of the self‐tuning AGC scheme is developed and analysed. The proposed controller is tested in response to system contingencies for different short circuit ratios. The performance of the secondary voltage control without and with AGC is verified. The influence of the AGC in improving the transient response and damping of voltage oscillations is verified. Copyright © 2010 John Wiley & Sons, Ltd.     

Flicker study on variable speed wind turbines with doubly fed induction generators

Grid connected wind turbines may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbine with a doubly fed induction generator developed in the simulation tool of PSCAD/EMTDC. Flicker emission of variable speed wind turbines with doubly fed induction generators is investigated during continuous operation, and the dependence of flicker emission on mean wind speed, wind turbulence intensity, short circuit capacity of grid and grid impedance angle are analyzed. A comparison is done with the fixed speed wind turbine, which leads to a conclusion that the factors mentioned above have different influences on flicker emission compared with that in the case of the fixed speed wind turbine. Flicker mitigation is realized by output reactive power control of the variable speed wind turbine with doubly fed induction generator. Simulation results show the wind turbine output reactive power control provides an effective means for flicker mitigation regardless of mean wind speed, turbulence intensity and short circuit capacity ratio.     

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.     

Intelligent approach to maximum power point tracking control strategy for variable-speed wind turbine generation system

To achieve maximum power point tracking (MPPT) for wind power generation systems, the rotational speed of wind turbines should be adjusted in real time according to wind speed. In this paper, a Wilcoxon radial basis function network (WRBFN) with hill-climb searching (HCS) MPPT strategy is proposed for a permanent magnet synchronous generator (PMSG) with a variable-speed wind turbine. A high-performance online training WRBFN using a back-propagation learning algorithm with modified particle swarm optimization (MPSO) regulating controller is designed for a PMSG. The MPSO is adopted in this study to adapt to the learning rates in the back-propagation process of the WRBFN to improve the learning capability. The MPPT strategy locates the system operation points along the maximum power curves based on the dc-link voltage of the inverter, thus avoiding the generator speed detection.     

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.     

基于风电机组无功裕度预测的风电场无功分层控制策略

针对风电电压波动的问题,文章基于风电机组无功裕度预测,提出了一种风电场无功分层控制策略。该策略首先以并网点电压偏差和线路有功损耗最小为目标,使用二次规划算法在线实时求解最优并网电压,进而求解风电场无功参考值;其次,采用EWT-LSSVM预测算法进行风电功率预测,并提出预测功率校正方法实时修正预测功率,精确求解风电机组的无功裕度预测值;最后,以风电机组的出口电压波动最小和预测无功裕度最大为无功分配依据,实现风电场的无功电压闭环控制。仿真结果表明,所提控制策略能够提高风电功率预测的精确性和时效性,降低了风电机组出口电压波动性,同时为风电场预留出充足的无功裕度。