Wind Speed Estimation Based Sensorless Output Maximization Control for a Wind Turbine Driving a DFIG

This paper proposes a wind speed estimation based sensorless maximum wind power tracking control for variable-speed wind turbine generators (WTGs). A specific design of the proposed control algorithm for a wind turbine equipped with a doubly fed induction generator (DFIG) is presented. The aerodynamic characteristics of the wind turbine are approximated by a Gaussian radial basis function network based nonlinear input-output mapping. Based on this nonlinear mapping, the wind speed is estimated from the measured generator electrical output power while taking into account the power losses in the WTG and the dynamics of the WTG shaft system. The estimated wind speed is then used to determine the optimal DFIG rotor speed command for maximum wind power extraction. The DFIG speed controller is suitably designed to effectively damp the low-frequency torsional oscillations. The resulting WTG system delivers maximum electrical power to the grid with high efficiency and high reliability without mechanical anemometers. The validity of the proposed control algorithm is verified by simulation studies on a 3.6MW WTG system. In addition, the effectiveness of the proposed wind speed estimation algorithm is demonstrated by experimental studies on a small emulational WTG system.     

风力发电机组的电气控制

本文综述风力发电机组的电气控制。在简述风力涡轮机特性的基础上,介绍恒速发电和变速发电的特点和应用场合,重点是基于同步发电机的“直接在线”发电和基于绕线异步机的“双馈”发电系统,以及桨叶倾角控制系统。作为对未来的展望,最后介绍一种新型锥形转子风力发电机组的设想。     

基于最佳功率给定的永磁直驱同步风力发电系统控制策略研究

直驱型风力发电系统由于不需要增速箱,在风电场中得到广泛的发展和应用.该文研究了发电机和风机的特性分析,提出了基于最佳功率给定的最大风能控制策略,该方法通过对发电机进行闭环控制,使输出功率按照最优功率曲线进行输出,实现最大风能跟踪.并研究了永磁直驱风电系统的双PWM变流器控制策略;搭建了直驱型风电机组整体模型,该系统能够实现并风能最大功率跟踪及并网控制,仿真验证了控制系统的正确性.     

基于压电材料的钢筋砼-钢组合塔筒损伤监测

钢筋混凝土-钢组合塔筒作为一种新型的风电塔架形式,其混凝土段的开裂对其使用寿命具有重要影响,对其混凝土段的开裂进行监测具有重要意义。该文提出了一种基于压电陶瓷激励的应力波测量的钢筋混凝土塔段的开裂监测方法,以某钢筋混凝土-钢塔筒缩尺模型为对象,以布置在钢筋混凝土塔筒表面的压电陶瓷片为激励器,利用布置在钢筋混凝土塔筒不同高度位置的压电陶瓷片作为传感器,实现在不同水平往复加载下的应力波的测量。对混凝土塔段从裂缝开始出现直至构件最终破坏整个过程各压电陶瓷片的响应进行分析,并定义损伤指标。结果表明,定义的指标不仅可较好反应裂缝实际出现位置,且与加载等级相关,所提出的监测方法可对钢筋混凝土塔段裂缝的发生和发展过程进行有效监测。     

基于信号流图的风力发电机故障诊断

针对风力发电机故障原因复杂,为解决其诊断困难问题。本文利用风力发电机电力系统中故障高发区的故障诊断经验知识,建立了风力发电机多信号流图模型。通过感应器获取实时检测信号数据并作为输入,并结合贝叶斯后验概率算法实现自动化的风力发电机故障诊断。根据风力发电机实时数据诊断表明,该方法能准确诊断出故障源,是一种十分有效的实时故障诊断方法。     

Extending the Life of Gear Box in Wind Generators by Smoothing Transient Torque With STATCOM

Gearboxes for wind turbines must ensure high reliability over a period of 20 years, withstanding cumulative and transient loads. One main challenge to this is represented by electromagnetic torque transients caused by grid faults and disturbances, which will result in significant stresses and fatigue of the gearbox. Possibilities for limiting the torque transients in fixed-speed wind generators have not been previously reported. This paper presents a technique by which the transient torques during recovery after a grid fault can be smoothed in a wind farm with induction generators directly connected to the grid. A model-based control technique using the quasi-stationary equivalent circuit of the system is suggested for controlling the torque with a static synchronous compensator (STATCOM). The basis of the approach consists of controlling the induction generator terminal voltage by the injection/absorption of reactive current using the STATCOM. By controlling the terminal voltage as a function of the generator speed during the recovery process, the electromagnetic torque of the generator is indirectly controlled, in order to reduce the drive train mechanical stresses caused by the characteristics of the induction machine when decelerating through the maximum torque region. The control concept is shown by time-domain simulations, where the smoothing effect of the proposed technique on a wind turbine is seen during the recovery after a three-phase-to-ground-fault condition. The influence of the shaft stiffness in a multimass drive train model is discussed, and the performance of the control concept in the case of parallel connection of several turbines is investigated to discuss the applicability in a wind farm.      

A Review of the State of the Art of Power Electronics for Wind Turbines

This paper reviews the power electronic applications for wind energy systems. Various wind turbine systems with different generators and power electronic converters are described, and different technical features are compared. The electrical topologies of wind farms with different wind turbines are summarized and the possible uses of power electronic converters with wind farms are shown. Finally, the possible methods of using the power electronic technology for improving wind turbine performance in power systems to meet the main grid connection requirements are discussed.      

Low Voltage Ride Through of Wind Farms With Cage Generators: STATCOM Versus SVC

This paper analyzes the extent to which the low voltage ride through (LVRT) capability of wind farms using squirrel cage generators can be enhanced by the use of a STATCOM, compared to the thyristor controlled static var compensator (SVC). The transient stability margin is proposed as the indicator of LVRT capability. A simplified analytical approach based on torque-slip characteristics is first proposed to quantify the effect of the STATCOM and the SVC on the transient stability margin. Results from experiments with a STATCOM and a 7.5 kW induction machine emulating a wind turbine are used to validate the suggested analytical approach. Further verifications based on detailed time-domain simulations are also provided. Calculations, simulations and measurements confirm how the increased STATCOM rating can provide an increased transient stability margin and thus enhanced LVRT capability. Compared to the SVC, the STATCOM gives a larger contribution to the transient margin as indicated by both calculations and simulations. The inaccuracies introduced by neglecting the flux transients in the suggested approach are discussed and found reasonable for an estimation method when considering the simplicity compared to detailed time-domain simulation studies. A method for estimating the required rating of different compensation devices to ensure stability after a fault is suggested based on the same approach.     

A New Architecture for Offshore Wind Farms

Offshore wind farms using HVDC links can be positioned a large distance from shore, opening up new opportunities for wind generation. Conventional approaches using 60 Hz generators and transformers are not appropriate in such applications, as they are heavy and result in expensive and complex installation and maintenance issues. This paper proposes an alternative architecture for such wind farms, using permanent magnet generators, medium frequency transformers and simple power converters to realize a compact and light system. It is possible that in the long term, the proposed approach may prove attractive for land-based wind farms as well.     

A Fuzzy Logical MPPT Control Strategy for PMSG Wind Generation Systems

Making full use of wind power is one of the main purposes of the wind turbine generator control. Conventional hill climbing search (HCS) method can realize the maximum power point tracking (MPPT). However, the step size of HCS method is constant so that it cannot consider both steady-state response and dynamic response. A fuzzy logical control (FLC) algorithm is proposed to solve this problem in this paper, which can track the maximum power point (MPP) quickly and smoothly. To evaluate MPPT algorithms, four performance indices are also proposed in this paper. They are the energy captured by wind turbine, the maximum power-point tracking time when wind speed changes slowly, the fluctuation magnitude of real power during steady state, and the energy captured by wind turbine when wind speed changes fast. Three cases are designed and simulated in MATLAB/Simulink respectively. The comparison of the three MPPT strategies concludes that the proposed fuzzy logical control algorithm is more superior to the conventional HCS algorithms.     

A Secondary Voltage Control Strategy for Transmission Level Interconnection of Wind Generation

This paper addresses implementation issues associated with secondary voltage control in a doubly-fed induction generator based wind farm. The effects of different system parameters on the performance of the control are considered, namely the short circuit ratio of the interconnection and the inherent communication delay between the wind park and the remote bus. In addition, a strategy for allocation reactive power requirements to each of the generators within the wind park is proposed. The system is developed and simulated for a wind park consisting of six wind generators connected to a typical transmission system. The paper proposes an optimal tracking secondary voltage control method developed to achieve effective voltage regulation, enhance the network voltage profile and provide optimal reactive power compensation to the interconnected power system. The performance of the controller is compared with secondary voltage control at one selected bus, primary voltage control and the optimal voltage profile obtained from the optimal power flow analysis. The performance of the controllers is tested for steady state operation and in response to system contingencies, taking into account the impact of communication time delays and short circuit ratio (SCRs). Simulation results are presented to demonstrate the capability of the controllers to provide the desired reactive power compensation and voltage support to the electric power grid.     

基于ZigBee的风电机组振动故障监测系统设计

：针对目前风电机组有线监测系统安装、维护不便和监测点有限等问题,设计了基于ZigBee的风电机组振动故障监测系统,由传感器节点、协调器节点、3G网络和监控中心组成。传感器节点采集机组各部位的振动参数并发送至协调器节点,经过协调器节点处理的信息通过3G网络发送至远程监控中心,此设计提高了系统的可靠性和实时性。测试结果表明系统节点间通信良好,系统工作稳定性高,数据传输实时性好,及时给出报警信息,故障诊断正确率达到95.5%。     

基于单–双高斯模型拟合法的测风激光雷达海上风电机组尾流特征分析

当气流经过风电机组的扫风平面时, 风电机组下风处产生的尾流效应会对风电机组的发电效率、疲劳载荷产 生不同程度的影响。基于相干多普勒测风激光雷达在江苏某海上风电场开展了全天候风场观测实验。由于紧邻风电 机组的尾流垂直截面上风速呈双高斯分布规律, 利用传统单高斯拟合算法存在计算误差较大, 无法反映真实流场风速 变化规律, 提出了一种单–双高斯模型拟合改进算法, 分析了目标风电机组尾流的尾流宽度、风速损失率和尾流长度 等参数特征, 研究结果验证了单–双高斯拟合算法对尾流横向风速拟合的可行性和准确性。     

基于微多普勒特征的风轮机雷达杂波检测

作为一种清洁能源和可再生能源的形式,近年来风能受到了全球各国的普遍关注,风轮机会对其附近的航管监视雷达产生不利影响。风轮机雷达杂波检测技术的研究,对于保障民航飞机的空中交通安全起着重要作用。提出了一种基于风轮机雷达回波微多普勒特征的杂波检测方法,该方法利用风轮机与雷达波束不同位置条件下风轮机杂波的微动特征实现风轮机杂波的检测。对检测出的存在风轮机杂波的距离单元进一步判断是否存在飞机目标,进而只需对存在飞机目标的距离单元进行杂波抑制。仿真结果表明该算法能够实现风轮机雷达杂波的有效检测。      

基于散射中心的风电机叶片散射电场求解

为降低雷达系统的数据处理量及实现风电机实时目标特征识别,必须寻求风电机叶片散射电场的快速求解方法。针对传统电磁求解算法需处理巨量风电机叶片散射电场数据的问题,突破传统以超大电尺寸目标实体为基本单元进行广域空间电磁散射积分计算的思想,提出了一种基于散射中心的风电机叶片散射电场求解方法。基于非衰减指数和散射中心模型,通过距离-多普勒算法构建风电机叶片的雷达逆合成孔径图像,采用CLEAN 算法并结合相关系数提取风电机叶片的散射中心参数集,最终以散射中心产生的散射电场数据等效替代叶片本体的全部散射数据,实现了叶片散射电场的快速求解。以Vestas V82-1.65MW 型风电机为例,以矩量法计算结果为基准,文中所提方法计算准确度为93.20%,数据的压缩比达76.81,计算量的数量级比矩量法降低了106。     

实验室模拟风力机的研究

为了解决实验室风力机的模拟问题,提出了直流电机模拟风力机的方案。同时分析了风力机的运行特性及最佳风能利用原理,采用简单有效的转速、转矩控制,搭建风力机的Matlab仿真模型。该风力机模拟系统应用于变速恒频风力发电系统中,满足了双馈电机在不同状态下运行以及追踪最大风能的变速恒频发电运行等方面研究的需要。     

基于MPPT的变速恒频双馈风力发电系统控制策略

充分利用风能是风力发电控制的主要目的之一,为达此目的,本文基于风力机特性和双馈风力发电机的数学模型,提出了一种不依赖于风速测量来实现双馈风力发电系统最大功率点追踪(MPPT)控制的策略。该策略应用定子磁链定向矢量控制技术,对双馈发电机进行有功功率和无功功率的解耦控制,然后通过对发电机输出有功功率进行控制来间接得到与风速相对应的最佳叶尖速比和最优转速,从而实现最大功率点追踪(MPPT)控制。仿真结果证实了基于该方法,双馈风力发电系统在风速变化过程中能自动寻找并追随最大功率点,且控制相对简单,运行可靠,有较高的实用价值。     

High-Order Sliding-Mode Control of Variable-Speed Wind Turbines

This paper deals with the power generation control in variable-speed wind turbines. These systems have two operation regions which depend on wind turbine tip speed ratio. A high-order sliding-mode control strategy is then proposed to ensure stability in both operation regions and to impose the ideal feedback control solution in spite of model uncertainties. This control strategy presents attractive features such as robustness to parametric uncertainties of the turbine. The proposed sliding-mode control approach has been validated on a 1.5-MW three-blade wind turbine using the National Renewable Energy Laboratory wind turbine simulator FAST (Fatigue, Aerodynamics, Structures, and Turbulence) code. Validation results show that the proposed control strategy is effective in terms of power regulation. Moreover, the sliding-mode approach is arranged so as to produce no chattering in the generated torque that could lead to increased mechanical stress because of strong torque variations.      

Multiterminal LVDC system for optimal acquisition of power inwind-farm using induction generators

Optimal wind-power acquisition requires automatic tracking of the optimum wind-turbine speed for the prevailing wind velocity. As the wind velocity keeps changing with time so the wind-turbine must keep adjusting its speed. In a wind-farm, the wind velocities depend on the locations of the wind-turbines, each of which has its optimal turbine speed at any given time. With an eye to costs, the wind-farm of this paper is conceived as operating with cheap induction generators driven by variable-speed wind-turbines, without the expense of speed governors. This paper shows that the voltage-source converters of low voltage direct current (LVDC) transmission systems (which are now commercially available) can be tailored as speed-sensorless drives of the wind-turbine induction generators, while meeting the objective of optimal wind-power acquisition. The LVDC system aggregates the power of many wind-turbine induction-generator units into a DC grid. Then a DC voltage regulator inverts the collected power into a three-phase AC electric utility grid     

风轮机叶片电磁散射特性的占比分析与解析模型的建立

针对风轮机叶片雷达散射截面积的变化特性,分析了风轮机叶片雷达散射截面积（Radar Cross Section, RCS）对其整体雷达散射特性占比情况,实现对叶片解析模型适用范围的选取。考虑了风轮机叶片旋转平面与雷达视线（Line of Sight, LOS）夹角、叶片材料、叶片几何形状等因素对风轮机散射特性的影响,运用UG软件对风轮机叶片进行三维建模,利用真实叶片与相应简化圆柱叶片电磁散射特性的差异构建高保真的风轮机真实叶片电磁散射特性的解析模型,实现风轮机叶片RCS的快速计算。最后将解析模型计算结果与实测数据进行对比,验证了论文给出的真实叶片电磁散射特性解析模型的有效性。