Wind speed time series characterization by Hilbert transform

Predictions of wind energy potential in a given region are based on on‐location observations. The time series of these observations would later be analysed and modelled either by a probability density function (pdf) such as a Weibull curve to represent the data or recently by soft computing techniques, such as neural networks (NNs). In this paper, discrete Hilbert transform has been applied to characterize the wind sample data measured on ?zmir Institute of Technology campus area which is located in Urla, ?zmir, Turkey, in March 2001 and 2002. By applying discrete Hilbert transform filter, the instantaneous amplitude, phase and frequency are found, and characterization of wind speed is accomplished. Authors have also tried to estimate the hourly wind data using daily sequence by Hilbert transform technique. Results are varying. Copyright © 2005 John Wiley & Sons, Ltd.     

Improved synthetic wind speed generation using modified Mycielski approach

In this paper, novel approaches for wind speed data generation using Mycielski algorithm are developed and presented. To show the accuracy of developed approaches, we used three‐year collected wind speed data belonging to deliberately selected two different regions of Turkey (Izmir and Kayseri) to generate artificial wind speed data. The data belonging to the first two years are used for training, whereas the remaining one‐year data are used for testing and accuracy comparison purposes. The concept of distinct synthetic data production with correlation‐wise and distribution‐wise similar statistical properties constitutes the main idea of the proposed methods for a successful artificial wind speed generation. Generated data are compared with test data for both regions in the sense of basic statistics, Weibull distribution parameters, transition probabilities, spectral densities, and autocorrelation functions; and are also compared with the data generated by the classical first‐order Markov chains method. Results indicate that the accuracy and realistic behavior of the proposed method is superior to the classical method in the literature. Comparisons and results are discussed in detail. Copyright © 2011 John Wiley & Sons, Ltd.     

Copula-based joint distribution analysis of wind speed and wind direction: Wind energy development for Hong Kong

Accurate and reliable assessment of wind energy potential has important implication to the wind energy industry. Most previous studies on wind energy assessment focused solely on wind speed, whereas the dependence of wind energy on wind direction was much less considered and documented. In this paper, a copula-based method is proposed to better characterize the direction-related wind energy potential at six typical sites in Hong Kong. The joint probability density function (JPDF) of wind speed and wind direction is constructed by a series of copula models. It shows that Frank copula has the best performance to fit the JPDF at hilltop and offshore sites while Gumbel copula outperforms other models at urban sites. The derived JPDFs are applied to estimate the direction-related wind power density at the considered sites. The obtained maximum direction-related wind energy density varies from 41.3 W/m² at an urban site to 507.9 W/m² at a hilltop site. These outcomes are expected to facilitate accurate micro-site selection of wind turbines, thereby improving the economic benefits of wind farms in Hong Kong. Meanwhile, the developed copula-based method provides useful references for further investigations regarding direction-related wind energy assessments at various terrain regions. Notably, the proposed copula-based method can also be applied to characterize the direction-related wind energy potential somewhere other than Hong Kong.     

Validation of fixed speed wind turbine dynamic models with measured data

Power system dynamics studies involving fixed-speed wind turbines normally use a wind turbine model consisting of two lumped masses, an elastic coupling and a induction generator model which neglects stator transients. However, validations of this model with measured data are rarely reported in the literature. This paper validates the model using a recorded case obtained in a fixed speed, stall regulated 180 kW wind turbine through a voltage dip. The work analyses the performance of the reduced order induction generator model which neglects stator transients, compared to the detailed induction generator model. It also includes a study of the convenience of representing mechanical damping in the drive train, and an evaluation of the single mass mechanical model.     

Wind energy potential evaluation for power generation in selected districts of Jharkhand

This study evaluated the availability of wind energy for electricity production at different locations, i.e., Ranchi, Jamshedpur, Devghar, Lohardaga, and Chaibasa, in Jharkhand, India. Due to the rapidly rising demand for power in Jharkhand, there is a requirement of an alternative renewable source of energy to lower the dependence on its limited fossil fuel resources. The studied locations were found to be unsuitable for wind to electricity generation on a large scale at 10 m height above the ground. However, small-scale wind turbines can be used to extract energy from low-speed wind, preferably at a height above 10 m from the ground.     

内蒙古地区风资源评估与风场特征风速的推导

对内蒙古二十四个地区的风能资源进行评估,得到风谱图.首先提出了利用WAsP软件对1998年至2008年期间内蒙古二十四地区的风资源资料中的基础进行分析;然后利用风速威布尔分布函数和风力发电机组输出功率的威布尔的概率密度函数,求两个函数的极值,推导出切入风速和额定风速的公式.最后以内蒙古六个地区为例,计算不同风资源条件下的切入风速和额定风速.     

Comparison of simulators for variable‐speed wind turbine transient analysis

This paper presents a comparison of three variable‐speed wind turbine simulators used for a 2 MW wind turbine short‐term transient behaviour study during a symmetrical network disturbance. The simulator with doubly fed induction generator (DFIG) analytical model, the simulator with a finite element method (FEM) DFIG model and the wind turbine simulator with an analytical model of DFIG are compared. The comparison of the simulation results shows the influence of the different modelling approaches on the short‐term transient simulation accuracy. Copyright © 2005 John Wiley & Sons, Ltd.     

我国风力发电发展现状和问题分析

能源危机的日趋严重,优化能源结构、发展清洁环保的可再生能源迫在眉睫。风能是一种清洁环保的可再生能源,随着国家政策的支持和风力发电技术的不断发展,风力发电越来越得到人们的重视,并将在新能源发电中扮演重要的角色。概述了我国风能资源的储量和分布,介绍了近年来我国风力发电的总体情况、各省(自治区)风力发电的发展概况以及我国风电企业的发展现状,最后指出了我国风力发电目前出现的一些问题,并进行了分析。     

风电场风切变指数研究

根据山东某风电场实测资料,对风电场逐月、逐时、不同风速下的风切变指数进行研究并探究风切变指数不同取值对风电场轮毂高度处风资源的影响。在分析轮毂高度风资源时,建议采用高差较小的高度处风速根据综合风切变指数进行推导。     

风电场风速预测模型研究

介绍了两种风电场风速预测模型,分别是BP神经网络模型和小波-BP神经网络组合模型。BP神经网络模型是风速预测中常用的模型之一,小波技术和BP神经网络结合,即为组合模型。小波技术将风速时间序列按时间和频率两个方向展开,体现了各成分对预测值贡献率的不同。将BP神经网络模型和小波-BP神经网络组合模型分别应用到我国朱日和风电场的逐时风速预测中,从预测结果对比得出组合模型更适合该风电场的逐时风速预测。     

浅谈变速恒频双馈风力发电机

阐述了双馈风力发电机实现变速恒频的工作原理,讨论了双馈电机的运行状态,推导了双馈电机功率传输方式与转差率的关系,指出了变速恒频风力发电系统的优点是拓宽了风速的可利用范围,对提高风电场发电能力具有重要意义。     

Modelling and control of synchronous generators for wide‐range variable‐speed wind turbines

The modelling and control of a wide‐range variable speed wind turbine based on a synchronous generator are presented. Two different methods to control the operation of the synchronous generator are investigated, i.e. load angle control and instantaneous vector control. The dynamic performance characteristics of these control strategies are evaluated and compared using three model representations of the generator: a non‐reduced order model including both stator and rotor transients, a reduced order model with stator transients neglected, and a steady‐state model that neglects generator electrical dynamics. Assessment on the performance of grid‐side controller is shown during network fault and frequency variation. A simplified wind turbine model representation is also developed and proposed for large‐scale power system studies. Simulation results in Matlab/Simulink are presented and discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Wind speed forecast model for wind farm based on a hybrid machine learning algorithm

This paper presents a new strategy for wind speed forecasting based on a hybrid machine learning algorithm, composed of a data filtering technique based on wavelet transform (WT) and a soft computing model based on the fuzzy ARTMAP (FA) network. The prediction capability of the proposed hybrid WT+FA model is demonstrated by an extensive comparison with some other existing wind speed forecasting methods. The results show a significant improvement in forecasting error through the application of a proposed hybrid WT+FA model. The proposed wind speed forecasting strategy is applied to real data acquired from the North Cape wind farm located in PEI, Canada.     

Wind energy–hydrogen storage hybrid power generation

In this theoretical investigation, a hybrid power generation system utilizing wind energy and hydrogen storage is presented. Firstly, the available wind energy is determined, which is followed by evaluating the efficiency of the wind energy conversion system. A revised model of windmill is proposed from which wind power density and electric power output are determined. When the load demand is less than the output of the generation, the excess electric power is relayed to the electrolytic cell where it is used to electrolyze the de‐ionized water. Hydrogen thus produced can be stored as hydrogen compressed gas or liquid. Once the hydrogen is stored in an appropriate high‐pressure vessel, it can be used in a combustion engine, fuel cell, or burned in a water‐cooled burner to produce a very high‐quality steam for space heating, or to drive a turbine to generate electric power. It can also be combined with organic materials to produce synthetic fuels. The conclusion is that the system produces no harmful waste and depletes no resources. Note that this system also works well with a solar collector instead of a windmill. Copyright © 2001 John Wiley & Sons, Ltd.     

基于多任务学习的风速实时预测方法

准确的秒级风速实时预测能够提高风电机组的运行状况和控制品质,为电网做出最优调度决策提供辅助信息.目前风速实时预测时间分辨率通常为分钟级,且在小数据集的情况下模型泛化能力弱.文章以时间分辨率为5s的风速序列为研究对象,提出了基于多任务学习的风速实时预测方法.该方法结合了变分模态分解方法和长短期记忆神经网络.首先,通过变分...     

风电场50年一遇安全风速计算方法的对比分析

利用耿贝尔Ⅰ型极值概率法和MeteodynWT软件(CFD模型),结合气象站与风电场的风速关系,推算了不同复杂程度的风电场轮毂高度处50年一遇的安全风速,并将计算结果进行对比分析。分析结果显示:2种方法计算得到的风电场极大风速存在一定的差别;对于平坦地区,耿贝尔Ⅰ型极值概率法计算得到的极大风速与MeteodynWT推算结果相差较小,但对于一些复杂地区,2种方法计算得到的极大风速结果相差很大。     

Stochastic generation of hourly mean wind speed data

Use of wind speed data is of great importance in civil engineering, especially in structural and coastal engineering applications. Synthetic data generation techniques are used in practice for cases where long wind speed data are required. In this study, a new wind speed data generation scheme based upon wavelet transformation is introduced and compared to the existing wind speed generation methods namely normal and Weibull distributed independent random numbers, the first- and second-order autoregressive models, and the first-order Markov chain. Results propose the wavelet-based approach as a wind speed data generation scheme to alternate the existing methods.     

Comparative study of speed estimators with highly noisy measurement signals for Wind Energy Generation Systems

This paper presents a comparative study of several speed estimators to implement a sensorless speed control loop in Wind Energy Generation Systems driven by power factor correction three-phase boost rectifiers. This rectifier topology reduces the low frequency harmonics contents of the generator currents and, consequently, the generator power factor approaches unity whereas undesired vibrations of the mechanical system decrease. For implementation of the speed estimators, the compared techniques start from the measurement of electrical variables like currents and voltages, which contain low frequency harmonics of the fundamental frequency of the wind generator, as well as switching frequency components due to the boost rectifier. In this noisy environment it has been analyzed the performance of the following estimation techniques: Synchronous Reference Frame Phase Locked Loop, speed reconstruction by measuring the dc current and voltage of the rectifier and speed estimation by means of both an Extended Kalman Filter and a Linear Kalman Filter.     

变速恒频风力发电系统风速短期预测方法研究

采用现有方法预测短期变速恒频风力发电系统的风速时,因未分析风力机的运行特性而导致无法准确预测系统的输出无功功率、输出有功功率和短期风速,且预测结果的平均绝对误差和均方误差大,为此提出变速恒频风力发电系统风速的预测方法。首先对风力机的运行特性进行分析,然后采用支持向量机回归算法构建风速预测模型,最后利用风速预测模型完成变速恒频风力发电系统风速的短期预测。实验结果表明,所提方法可准确地预测系统的输出无功功率、输出有功功率和短期风速,且预测结果的平均绝对误差和均方误差小,验证了所提方法的整体有效性。