Operation and coordinated control of fixed and variable speed wind farms

This paper will describe the possibilities of coordinated control and management for different wind farm concepts to guarantee that operational set points of active and reactive power, specified by the Spanish transmission system operator (TSO), are reached. This coordinated control has been designed and implemented by a hierarchical and robust control structured from a central control level to each wind farm control board and finally to an individual wind turbine level. This article will demonstrate that both technologies, fixed and variable speed based wind farms can contribute to power and voltage control. In particular, this paper will deal with the use of under-load tap changing transformers in the point of common coupling of the wind farm with the grid, and the reactive power compensation by means of convectional mechanical switched capacitors enhancing the integration of the fixed speed wind farms in the power system.     

Offshore wind energy in the world context

The interest for the exploitation of the offshore wind energy is growing in Europe, where man land use is very high resulting in strong limitation to the installation of onshore wind farms. The today offshore operating wind power is 12 MW, with two wind farms in Denmark and one in Netherlands; it starts to be significant (0.6%) in terms of the onshore power, 2000 MW in Europe.In the world the onshore installed wind power is exceeding 4000 MW, but not so much up to now has been done on the offshore area outside Europe.The European four years experience on the prototypical offshore wind farms looks significantly promising and suggests to promote a similar approach in many densely populated coastal countries in the world with high electricity demand.Results of studies are presented on the offshore wind potential in the European countries and of the tentative evaluation for the Mediterranean basin, and the seas of USA and China. A review is made of the offshore applications, particularly for the Nothern European seas.Economy and environmental trends are illustrated in parallel to those of maturing offshore technology. It is suggested to prepare an action plan to promote the development of the offshore applications in the world context.     

Offshore wind energy prospects

In last two years offshore wind energy is becoming a focal point of national and non national organizations particularly after the limitations of fossil fuel consumption, adopted by many developed countries after Kyoto conference at the end of 1997 on global climate change. North Europe is particularly interested in offshore for the limited land areas still available, due to the intensive use of its territory and its today high wind capacity. Really the total wind capacity in Europe could increase from the 1997 value of 4450 MW up to 40 000 MW within 2010, according the White Paper 1997 of the European Commission; a significant percentage (25%) could be sited offshore up to 10 000 MW, because of close saturation of the land sites at that time. World wind capacity could increase from the 1997 value of 7200 MW up to 60 000 MW within 2010 with a good percentage (20%) offshore 12 000 MW. In last seven years wind capacity is shallow waters of coastal areas has reached 34 MW. Five wind farms are functioning in the internal seas of Netherlands, Denmark, Sweden; however such siting is mostly to be considered as semi-offshore condition. Wind farms in real offshore sites, open seas with waves and water depth over 10 m, are now proposed in North Sea at 10–20 km off the coasts of Netherland, Denmark using large size wind turbine (1–2 MW). In 1997 an offshore proposal was supported in Netherland by Greenpeace after the OWEMES '97 seminar, held in Italy on offshore wind in the spring 1997. A review is presented in the paper of the European offshore wind programs with trends in technology, economics and siting effects.     

Modelling wind farms for grid disturbance studies

This paper analyses the simplest representation of generators on wind turbine modelling, giving the accuracy required in power system disturbance studies. The order of the generator model and the numerical integration methods employed are compared.To avoid the use of a detailed model of a wind farm, several aggregated models can be found in the literature. This paper analyses the influence of the wind farm internal network in the accuracy of the results and proposes a new equivalent model to represent the dynamic response of wind farms. The proposed aggregated model considers a weighted average where the transported power is used as weighting factor in order to ameliorate the accuracy on grid disturbance simulations.     

Extraction of synoptic pressure patterns for long-term wind speed estimation in wind farms using evolutionary computing

In this paper we present an evolutionary approach for the problem of discovering pressure patterns under a quality measure related to wind speed and direction. This clustering problem is specially interesting for companies involving in the management of wind farms, since it can be useful for analysis of results of the wind farm in a given period and also for long-term wind speed prediction. The proposed evolutionary algorithm is based on a specific encoding of the problem, which uses a dimensional reduction of the problem. With this special encoding, the required centroids are evolved together with some other parameters of the algorithm. We define a specific crossover operator and two different mutations in order to improve the evolutionary search of the proposed approach. In the experimental part of the paper, we test the performance of our approach in a real problem of pressure pattern extraction in the Iberian Peninsula, using a wind speed and direction series in a wind farm in the center of Spain. We compare the performance of the proposed evolutionary algorithm with that of an existing weather types (WT) purely meteorological approach, and we show that the proposed evolutionary approach is able to obtain better results than the WT approach.     

海上风力发电进展

近年来风力发电工业发展迅速，海上风能以其突出的优势受到重视。本文对近年来国外几种典型的海上风能资源评估方法做出述评，简要叙述了国外海上风电技术发展与应用的现状，分析了海上风能利用的经济性，并介绍了一些主要国家进一步发展海上风电的计划。     

Aggregated dynamic model for wind farms with doubly fed induction generator wind turbines

As a result of increasing wind farms penetration in power systems, the wind farms begin to influence power system, and thus the modelling of wind farms has become an interesting research topic. Nowadays, doubly fed induction generator based on wind turbine is the most widely used technology for wind farms due to its main advantages such as high-energy efficiency and controllability, and improved power quality. When the impact of a wind farm on power systems is studied, the behavior of the wind farm at the point common coupling to grid can be represented by an equivalent model derived from the aggregation of wind turbines into an equivalent wind turbine, instead of the complete model including the modelling of all the wind turbines. In this paper, a new equivalent model of wind farms with doubly fed induction generator wind turbines is proposed to represent the collective response of the wind farm by one single equivalent wind turbine, even although the aggregated wind turbines operate receiving different incoming winds. The effectiveness of the equivalent model to represent the collective response of the wind farm is demonstrated by comparing the simulation results of equivalent and complete models both during normal operation and grid disturbances.     

基于NWP/CFD嵌套的复杂地形风场模拟研究

为解决复杂地形边界层风场模拟的边界条件问题,结合中尺度数值天气预报(NWP)和小尺度计算流体动力学(CFD)技术,提出一种基于NWP/CFD嵌套的降尺度风场模拟方法.该方法依据NWP低分辨率输出结果,建立目标区域来流边界数据库,并结合反距加权插值获得CFD边界精细格点信息.以沿海地区2处复杂地形为对象,重现目标区域内的...     

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 development in west of Romania

The paper attempts the assessment of a part of design and erection activities in wind energy field, in western Romania, from Electromontaj S.A. one new 100 % private company.So I shall refer to achievements of construction and erection:First the 3 MW demonstrative wind farm in Banat Mountain, and second the programmes for erection of experimental small wind turbines for operation in isolated settlements, in the power range 0,5–10 KW, and erection PV/Wind Turbines/Battery Systems, in small villages where are many lonely houses, who haven't electricity, for first time in our country.     

动态风工况下复杂地形风电场流场多尺度仿真

首先在秒级风速数据的基础上构建动态风速函数模拟真实风速工况,同时基于高程数据构建某真实复杂地形的三维结构图。基于格子玻尔兹曼方法并结合自适应格子排布,对复杂地形风电场非定常流场进行数值计算,得到该风电场的风资源分布。之后在典型位置布置2台2 MW风力发电机,考虑真实风力机叶片的动态旋转计算风力机及真实复杂地形在动态风工况下的流场。研究实际复杂地形和动态风速下风电场的风速分布及尾流结构演变规律。结果表明：该方法可实现对复杂地形在动态来流风速作用下的风资源分布预测,并考虑风力机小尺度尾流结构实现对真实风电场流场的多尺度仿真。     

Assessing the suitability of wind speed probabilty distribution functions based on wind power density

Three functions have so far predominantly been used for fitting the measured wind speed probability distribution in a given location over a certain period of time, typically monthly or yearly. In the literature, it is common to fit these functions to compare which one fits the measured distribution best in a particular location. During this comparison process, parameters on which the suitability of the fit is judged are required. The parameters that are mostly used are the mean wind speed or the total wind energy output (primary parameters). It is, however, shown in the present study that one cannot judge the suitability of the functions based on the primary parameters alone. Additional parameters (secondary parameters) that complete the primary parameters are required to have a complete assessment of the fit, such as the discrepancy between the measured and fitted distributions, both for the wind speed and wind energy (that is the standard deviation of wind speed and wind energy distributions). Therefore, the secondary statistical parameters have to be known as well as the primary ones to make a judgement about the suitability of the distribution functions analysed. The primary and secondary parameters are calculated from the 12-month of measured hourly wind speed data and detailed analyses of wind speed distributions are undertaken in the present article.     

Transient stability of a fixed speed wind farm

A typical fixed speed wind farm connected to a simple grid is modelled. Using this model, a three-phase fault is applied close to the wind farm, and cleared by disconnecting the affected line. The effect of several electric, mechanical and operational parameters on the critical fault-clearing time of this base case is evaluated and discussed. The studied parameters are the short-circuit power at the connection bus, the reactive power compensation, the distance to the fault, the rotor inertia, the hub-generator resonant frequency, the wind speed and the power output. For each parameter, the relationship between its value and the critical fault-clearing time is shown graphically. The results help to understand the transient stability phenomena in fixed speed wind farms, and could help to design fixed speed wind farms attending to transient stability requirements.     

几何约束条件下海上风电场布局优化方法研究

考虑实际工程需求,开发一种几何约束条件下海上风电场智能布局优化方法。该方法使用Gaussian模型计算风力机尾流区的速度亏损,并以最大化风电场年发电量为目标采用差分进化算法进行优化,可满足海上风电场布局时的各类几何约束。利用该方法分别在3行、4行、7行几何约束下对中国某海上风电场的风力机排布方式进行优化。结果显示,相比于原始布局方案,在考虑海缆铺设成本增加的情况下布局优化方案可提升风电场年发电量2.13%～2.64%。进一步分析表明,布局优化过程中可行解数量的设置需综合考虑智能算法寻优难度的影响。     

基于SVM方法的风电场短期风速预测

针对基于支持向量机的风电场短期风速预测进行研究．选择了不同的输入向量（历史风速时间序列,历史风速和温度．历史风速、温度和风向,历史风速、温度和时间）作为输入进行误差对比分析。实测数据及分析结果表明,采用历史风度和温度的二输入模型,预测效果最佳,为风速的短期预测和发电量预测提供了较好的参考价值。     

基于正交化的混合式平台漂浮式风电场平台动态响应研究

为研究混合式平台漂浮式风电场平台动态响应,分别建立基于Spar和Barge平台的漂浮式风力机整机模型,采用链接悬链线和固定悬链线将其链接以建立2×2阵列漂浮式风电场。采用叶素动量理论计算风载荷,通过辐射/绕射理论求解波浪载荷,采用水动力学软件AQWA研究风波载荷作用下漂浮式风电场平台的动态响应。针对Spar和Barge平台尺度大小不同导致系泊系统不对称引起的Spar平台横摇和艏摇响应较大问题,提出"依照尺度最大平台正交布置链接悬链线"的漂浮式风电场系泊系统布置准则。为验证所提出的系泊系统布置准则的可行性,对比研究系泊系统正交化前后漂浮式风电场平台的动态响应。结果表明,在极限海况下,系泊系统的正交化布置可减小Spar平台横荡响应,但一定程度会增加纵荡响应;而系泊系统正交化与否对漂浮式风电场平台垂荡、纵摇响应和机舱加速度影响较小。此外,正交化布置的系泊系统可显著减小Spar平台横摇和艏摇响应、Barge平台艏摇响应,而Barge平台横摇响应几乎不受影响。     

基于正交化的混合式平台漂浮式风电场平台动态响应研究

为研究混合式平台漂浮式风电场平台动态响应,分别建立基于Spar和Barge平台的漂浮式风力机整机模型,采用链接悬链线和固定悬链线将其链接以建立2×2阵列漂浮式风电场。采用叶素动量理论计算风载荷,通过辐射/绕射理论求解波浪载荷,采用水动力学软件AQWA研究风波载荷作用下漂浮式风电场平台的动态响应。针对Spar和Barge平台尺度大小不同导致系泊系统不对称引起的Spar平台横摇和艏摇响应较大问题,提出"依照尺度最大平台正交布置链接悬链线"的漂浮式风电场系泊系统布置准则。为验证所提出的系泊系统布置准则的可行性,对比研究系泊系统正交化前后漂浮式风电场平台的动态响应。结果表明,在极限海况下,系泊系统的正交化布置可减小Spar平台横荡响应,但一定程度会增加纵荡响应;而系泊系统正交化与否对漂浮式风电场平台垂荡、纵摇响应和机舱加速度影响较小。此外,正交化布置的系泊系统可显著减小Spar平台横摇和艏摇响应、Barge平台艏摇响应,而Barge平台横摇响应几乎不受影响。