Open loop wind turbine emulator

A new wind turbine emulator (WTE) is presented, which is able to simulate the turbine power curves without using a closed loop control system. The state of the art emulators use DC or AC motors, closed loop controlled by processors with the turbine power curves recorded. The presented emulator has a DC voltage source, a power resistor and a DC motor with independent excitation. The motor power curve has a shape similar to a wind turbine power curve for a given wind speed; the wind speed variations can be emulated by the variations of the DC voltage source. The open loop emulator is completely different and new, because it works in open loop and does not require the presence of a processor.The following elements are included: the theoretical foundations of the emulator, the emulator power curves adjustment procedure to simulate a commercial wind turbine and the experimental tests.     

离网型户用风力发电机性能测试系统的开发

本文为离网型户用风力发电机虚拟仪器性能测试系统的研制 ,利用NI公司推出的软件LabVIEW及相关配套硬件设备 ,设计了风力机基本性能参数的测试系统。通过对风力发电机输出电流、输出电压、大气温度、大气压力、风速等实验数据的分析和处理 ,得到风力发电机输出特性曲线 ,从而为评估和改进风力发电机的性能提供依据     

Development of a comprehensive MPPT for grid‐connected wind turbine driven PMSG

This paper proposes a comprehensive MPPT method by which extraction of maximum power from wind turbine and its subsequent transfer through various power stages and final delivery to the connected grid are realized. In the proposed system, the operation of the wind turbine at its maximum efficiency point is maintained by control of grid‐tied inverter such that the shaft speed of the generator is set to result the desired optimum tip speed ratio of the turbine. The proposed comprehensive MPPT estimates the required DC link voltage for each wind speed using a unified system model, uses a loss factor to account for the system losses, and then controls the inverter to push the WT extracted maximum power into the grid. The comprehensive MPPT is developed and is validated in MATLAB/Simulink platform in a wide range of operating wind speed. The results ascertain that the wind turbine is made to operate at its maximum efficiency point for all wind speeds below the rated one.     

分流导叶垂直轴风力机气动性能研究

为提高垂直轴风力机气动性能,提出一种随相位角变化而改变相对夹角的分流导叶结构。以NACA0021为基础翼型,采用计算流体力学方法对分流导叶作用下垂直轴风力机风能利用系数、单叶片瞬时转矩、压力系数及速度场进行数值分析。结果表明：静态和动态分流导叶均可提高垂直轴风力机气动性能,且动态分流导叶提升效果更为显著;相较于静态分流导叶,动态分流导叶垂直轴风力机在尖速比为2.33时风能利用系数最高可提升23%,在尖速比为2.03时静态分流导叶垂直轴风力机较原始垂直轴风力机风能利用系数提高37%;分流导叶也可使最佳尖速比前移,稳定叶片转矩波动,提升垂直轴风力机的运行稳定性。     

Condition monitoring of spar‐type floating wind turbine drivetrain using statistical fault diagnosis

Operation and maintenance costs are significant for large‐scale wind turbines and particularly so for offshore. A well‐organized operation and maintenance strategy is vital to ensure the reliability, availability, and cost‐effectiveness of a system. The ability to detect, isolate, estimate, and perform prognoses on component degradation could become essential to reduce unplanned maintenance and downtime. Failures in gearbox components are in focus since they account for a large share of wind turbine downtime. This study considers detection and estimation of wear in the downwind main‐shaft bearing of a 5‐MW spar‐type floating turbine. Using a high‐fidelity gearbox model, we show how the downwind main bearing and nacelle axial accelerations can be used to evaluate the condition of the bearing. The paper shows how relative acceleration can be evaluated using statistical change‐detection methods to perform a reliable estimation of wear of the bearing. It is shown in the paper that the amplitude distribution of the residual accelerations follows a t‐distribution and a change‐detection test is designed for the specific changes we observe when the main bearing becomes worn. The generalized likelihood ratio test is extended to fit the particular distribution encountered in this problem, and closed‐form expressions are derived for shape and scale parameter estimation, which are indicators for wear and extent of wear in the bearing. The results in this paper show how the proposed approach can detect and estimate wear in the bearing according to desired probabilities of detection and false alarm.     

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。     

Lightning attachment characteristic of wind turbine generator: Experimental investigation and prediction method based on simulations

As the height of wind turbine increases, the lightning strike accident has become a non-negligible issue. In this paper, the lightning attachment characteristic of a 2-MW wind turbine generator (WTG) is investigated using a model with a reduced scale of 100. The WTG model is equipped with receptors on the blades and a lightning rod on the nacelle, both serving as its external lightning protection system (LPS). The high-voltage electrode, which delivers a lightning impulse voltage from a Marx generator, is used to simulate the final stage of downward negative lightning strikes from 29 coming-leader positions. The experimental results indicate that lightning leaders from either front directions or side directions could be intercepted effectively by LPS, whereas the back-direction lightning could not. Moreover, with the increase of striking distance, the capture ratio for the insulation part of blade decreases. Electric field intensity distribution simulations for the full-scale WTG model, using conditions similar to their experimental counterparts, are conducted and compared with the lightning attachment distribution. Based on classical electro-geometrical model, a simulative method is proposed to predict the lightning attachment distribution of WTG. Our results indicate that it is feasible with this method to produce a satisfactory approximation to the experimentally obtained lightning attachment distribution.     

Performance of PI controller for control of active and reactive power in DFIG operating in a grid-connected variable speed wind energy conversion system

Due to several factors, wind energy becomes an essential type of electricity generation. The share of this type of energy in the network is becoming increasingly important. The objective of this work is to present the modeling and control strategy of a grid connected wind power generation scheme using a doubly fed induction generator (DFIG) driven by the rotor. This paper is to present the complete modeling and simulation of a wind turbine driven DFIG in the second mode of operating (the wind turbine pitch control is deactivated). It will introduce the vector control, which makes it possible to control independently the active and reactive power exchanged between the stator of the generator and the grid, based on vector control concept (with stator flux or voltage orientation) with classical PI controllers. Various simulation tests are conducted to observe the system behavior and evaluate the performance of the control for some optimization criteria (energy efficiency and the robustness of the control). It is also interesting to play on the quality of electric power by controlling the reactive power exchanged with the grid, which will facilitate making a local correction of power factor.     

Performance and near wake measurements of a model horizontal axis wind turbine

The performance characteristics and the near wake of a model wind turbine were investigated experimentally. The model tested is a three‐bladed horizontal axis type wind turbine with an upstream rotor of 0.90 m diameter. The performance measurements were conducted at various yaw angles, a freestream speed of about 10 m s ^?1, and the tip speed ratio was varied from 0.5 to 12. The time‐averaged streamwise velocity field in the near wake of the turbine was measured at different tip speed ratios and downstream locations. As expected, it was found that power and thrust coefficients decrease with increasing yaw angle. The power loss is about 3% when the yaw angle is less than 10° and increases to more than 30% when the yaw angle is greater than 30°. The velocity distribution in the near wake was found to be strongly influenced by the tip speed ratio and the yaw angle. At the optimum tip speed ratio, the axial velocity was almost uniform within the midsection of the rotor wake, whereas two strong peaks are observed for high tip speed ratios when the yaw angle is 0°. As the yaw angle increases, the wake width was found to be reduced and skewed towards the yawed direction. With increasing downstream distance, the wake velocity field was observed to depend on the tip speed ratio and more pronounced at high tip speed ratio. Copyright © 2011 John Wiley & Sons, Ltd.     

Modeling and control of a permanent magnet synchronous generator dedicated to standalone wind energy conversion system

The interest for the use of renewable energies has increased, because of the increasing concerns of the environmental problems. Among renewable energies, wind energy is now widely used. Wind turbines based on an asynchronous generator with a wound rotor present the inconvenience of requiring a system of rings and brooms and a multiplier, inferring significant costs of maintenance. To limit these inconveniences, certain manufacturers developed wind turbines based on synchronous machines with large number of pairs of poles coupled directly with the turbine, avoiding using the multiplier. If the generator is equipped with permanent magnets, the system of rings and brooms is eliminated. The control of the permanent magnet synchronous generator (PMSG) can be affected with the implementation of various techniques of control. This paper presented a new approach mainly based on the control strategy of power production system based on the PMSG. In fact, a mathematical model that simulates the Matlab chain was established with the introduction of control techniques, such as direct control of the torque (DTC) to control the load side converter (LSC), the control of the speed of the turbine and the DC-bus voltage ensured by PI regulators. To show the performance of the correctors used, some simulation results of the system were presented and analyzed.     

Prediction of wind turbine generator failure using two‐stage cluster‐classification methodology

Reducing wind turbine downtime through innovations surrounding asset management has the potential to greatly influence the levelised cost of energy (LCoE) for large wind farm developments. Focusing on generator bearing failure and vibration data, this paper presents a two‐stage methodology to predict failure within 1 to 2 months of occurrence. Results are obtained by building up a database of failures and training machine learning algorithms to classify the bearing as healthy or unhealthy. This is achieved by first using clustering techniques to produce subpopulations of data based on operating conditions, which this paper demonstrates can greatly influence the ability to diagnose a fault. Secondly, this work classifies individual clusters as healthy or unhealthy from vibration‐based condition monitoring systems by applying order analysis techniques to extract features. Using the methodology explained in the report, an accuracy of up to 81.6% correct failure prediction was achieved.     

残差灰色风速预测最大风能追踪策略研究

该文引入灰色预测理论,用以往时刻的风速信息预测下一控制时刻的风速,并用残差修正方法来提高预测精度。根据该预测风速的大小来确定下一时刻最优功率点搜索的起始风电机组转速,再利用变步长转速扰动的最大风能追踪策略(爬山法)找到最优功率点。仿真表明,残差灰色风速预测方法具有很好的预测效果,有效缩小了最优功率点的搜索区间,缩短了搜索时间,提高了机组的运行效率。     

Reliable and lightning‐safe monitoring of wind turbine rotor blades using optically powered sensors

Blade condition monitoring systems with fiber‐optic sensors attract much attention because they are resistant to lightning strikes, a major issue with increasing blade lengths. However, fiber‐optic sensor systems are more complex and more expensive than their electronic counterparts. We describe a new blade condition monitoring system, which combines the lightning safety of optical fibers with the reliability and cost‐effectiveness of electronic sensors. The optical fibers transport data from the blades to the hub, and in addition, they provide the electrical power for operating the sensor units in the blades. To achieve full protection against lightning‐induced electromagnetic fields, an appropriate shielding of the sensor units is required. We present results on the reliability of a newly developed prototype based on optically powered sensors. In a field trial, the unit monitored successfully the blade vibrations of a 1.5 MW wind turbine for a period of 23 months. Copyright © 2016 John Wiley & Sons, Ltd.     

Dynamic characteristics and improved MPPT control of PV generator

This paper presents a mathematical model of photovoltaic (PV) module and gives a strategy to calculate online the maximum power point (MPP). The variation of series and shunt resistor are taken into account in the model and are dynamically identified using the Newton-Raphson algorithm. The effectiveness of the proposed model is verified by laboratory experiments obtained by implementing the model on the dSPACE DS1104 board.     

适合于风力发电系统的电压跌落发生器

为满足在故障情况下的风力发电机控制策略的研究需要,给出了一种电压跌落发生器的拓扑结构,PC机与单片机通过串行通信来实现对电压跌落模式和跌落时间的控制.试验表明,该设备可以实现国外昂贵的电压跌落发生器的基本功能.     

永磁直驱风力发电系统MPPT控制的研究

文章首先介绍了风力机模型。然后介绍了一种改进型的变步长爬山算法,通过该算法改变直驱风力发电系统三重交错并联Boost变换电路的占空比,从而实现最大功率跟踪,获取最大风能。最后,利用MATLAB/SIMULINK建立直驱永磁风力发电系统仿真模型并进行研究。试验结果表明,改进型变步长爬山算法比传统爬山算法能更快跟踪最大功率点,控制系统具有较好的控制精度和稳定性。     

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.     

A novel method for obtaining virtual inertial response of DFIG‐based wind turbines

This paper investigates virtual inertia control of doubly fed induction generator (DFIG)‐based wind turbines to provide dynamic frequency support in the event of sudden power change. The relationships among DFIGs' virtual inertia, rotor speed and network frequency variation are analysed, and a novel virtual inertia control strategy is proposed. The proposed control strategy shifts the maximum power point tracking (MPPT) curve to the virtual inertia control curves according to the frequency deviation so as to release the ‘hidden’ kinetic energy and provide dynamic frequency support to the grid. The calculation of the virtual inertia and its control curves are also presented. Compared with a PD regulator‐based inertial controller, the proposed virtual inertia control scheme not only provides fast inertial response in the event of sudden power change but also achieves a smoother recovery to the MPPT operation. A four‐machine system with 30% of wind penetration is simulated to validate the proposed control strategy. Simulation results show that DFIG‐based wind farms can provide rapid response to the frequency deviation using the proposed control strategy. Therefore, the dynamic frequency response of the power grid with high wind power penetration can be significantly improved. Copyright © 2015 John Wiley & Sons, Ltd.     

A fuzzy control strategy for power smoothing and grid dynamic response enrichment of a grid‐connected wind energy conversion system

This paper concentrates on the output power smoothing and the grid dynamic response enhancement of a grid‐interactive MW‐class permanent magnet synchronous generator‐based wind energy conversion system (WECS). A simple fuzzy controller method is applied to improve the overall performance of the WECS. The proposed method can retrieve the storing kinetic energy from the inertia of a wind turbine, perfectly. As a result, it can ensure a proficient power smoothing of the variable speed WECS. On the other hand, the grid side inverter is controlled by the fuzzy controller. This approach can reduce the fluctuation of DC link voltage and can deliver a smooth power to the power grid. The proposed method is compared with two other methods such as the maximum power point tracking control method and the without fuzzy controller method. A simple shunt circuit also includes in the DC link circuit. Therefore, during the system fault condition, the WECS can perform a stable operation. Effectiveness of the proposed method is verified by numerical simulations. Copyright © 2013 John Wiley & Sons, Ltd.     

小型风电系统MPPT模糊／PID控制仿真研究

根据最大功率点跟踪的基本原理及常用风力发电控制系统的特点,提出了一种模糊／PID双模控制。具有在线参数调整的自适应占空比扰动法,该方法同步精度高,动态响应快,能迅速调整发电机与负载之间的功率匹配,减少最大功率点的振荡,使风力机以最佳叶尖速比运行。通过仿真实验表明,采用模糊／PID控制电路,能够快速准确的跟踪风力发电系统的最大功率点,改善最大功率点的振荡,减少能量损失,提高能量转换效率。