大规模集中接入条件下风电涉网特性分析

结合当前新能源迅猛发展的现状,分析了双馈风力发电机组的基本原理,利用simulink模型仿真分析了大规模集中接入条件下风电运行特性及风险,并最终提出了"风机低电压穿越改造"、"开放风电机组无功调节能力"两相项关键措施。仿真结果表明,文中提出的技术措施可为大规模集中接入条件下,风电及电网的安全稳定运行供借鉴。     

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.     

Sustainability assessment of wind turbines using fuzzy logic

Renewable energy systems provide opportunities for developing methods to evaluate their sustainability claims, inclusive of their life cycles, and to rank them based on their broader impact. In this paper, a fuzzy-logic-based method is proposed to evaluate and rank wind turbines as sustainable systems handling wind energy, in terms of renewability and environmental friendliness. Implementation of the proposed method is demonstrated in two steps: First, major factors defining life cycle and sustainability characteristics of wind turbines are identified. These factors are: Capital Cost, Greenhouse Gas Emission, and wind turbine Energy Efficiency. Nevertheless, the method allows expansion to include other factors, which may later be deemed as critical to the evaluation process. Second, a fuzzy-logic-based model is built and tested using hypothetical data to prove the concept. As a result, the relatively best sustainability is decided on a single dimension scale. The proposed method produced reliable results in terms of ordinally ranking the sustainability of wind turbines, but with interdependencies based on the entire group of wind turbine cases being examined. The proposed method formulates a satisfactory stepping stone on the way to establish a unified method and process to rank wind turbines based on sustainability.     

A novel method for reliability and risk evaluation of wind energy conversion systems considering wind speed correlation

This paper investigates an analytical approach for the reliability modeling of doubly fed induction generator (DFIG) wind turbines. At present, to the best of the authors’ knowledge, wind speed and wind turbine generator outage have not been addressed simultaneously. In this paper, a novel methodology based on the Weibull- Markov method is proposed for evaluating the probabilistic reliability of the bulk electric power systems, including DFIG wind turbines, considering wind speed and wind turbine generator outage. The proposed model is presented in terms of appropriate wind speed modeling as well as capacity outage probability table (COPT), considering component failures of the wind turbine generators. Based on the proposed method, the COPT of the wind farm has been developed and utilized on the IEEE RBTS to estimate the well-known reliability and sensitive indices. The simulation results reveal the importance of inclusion of wind turbine generator outage as well as wind speed in the reliability assessment of the wind farms. Moreover, the proposed method reduces the complexity of using analytical methods and provides an accurate reliability model for the wind turbines. Furthermore, several case studies are considered to demonstrate the effectiveness of the proposed method in practical applications.     

Difference between grid connections of large-scale wind power and conventional synchronous generation

In China, regions with abundant wind energy resources are generally located at the end of power grids. The power grid architecture in these regions is typically not sufficiently strong, and the energy structure is relatively simple. Thus, connecting large-capacity wind power units complicates the peak load regulation and stable operation of the power grids in these regions. Most wind turbines use power electronic converter technology, which affects the safety and stability of the power grid differently compared with conventional synchronous generators. Furthermore, fluctuations in wind power cause fluctuations in the output of wind farms, making it difficult to create and implement suitable power generation plans for wind farms. The generation technology and grid connection scheme for wind power and conventional thermal power generation differ considerably. Moreover, the active and reactive power control abilities of wind turbines are weaker than those of thermal power units, necessitating additional equipment to control wind turbines. Hence, to address the aforementioned issues with large-scale wind power generation, this study analyzes the differences between the grid connection and collection strategies for wind power bases and thermal power plants. Based on this analysis, the differences in the power control modes of wind power and thermal power are further investigated. Finally, the stability of different control modes is analyzed through simulation. The findings can be beneficial for the planning and development of large-scale wind power generation farms.     

Wind farms connected to weak grids in India

This article describes the mutual influence between the wind turbines and the power quality in the Indian power systems. The Indian power systems are weak in general and the wind energy development has been very fast and concentrated in a few rural areas where the existing transmission and distribution grids are very weak. Therefore the mutual influence between wind turbines and power quality is particularly strong in India. The wind farms influence power quality aspects such as steady state voltage, power factor, flicker and harmonic and interharmonic distortion. The power quality of the grid influences the power performance and safety of the wind turbines and the lifetime of mechanical and electrical components. The findings presented are general for wind farms connected to weak grids, but the Indian case is pronounced concerning weakness of grid as well as wind energy penetration level. Copyright © 2001 John Wiley & Sons, Ltd.     

基于网格-坐标化遗传算法的风电场布局优化

采用Jensen尾流模型来描述风电机组间尾流的干扰效应。首先基于网格化的改进遗传算法获得风电机组的数量和布局初始位置,再通过坐标化遗传算法对风电机组位置进行进一步调整优化,从而提高单位成本的发电量。根据所提出的方法,在3种不同的风场（定风向定风速、定风速变风向和变风速变风向）下,针对2 km×2 km的标准风场区域进行风电机组布局优化,再将其应用到不规则的实际案例,对比分析表明所提出的方法能有效提高发电量。     

Dynamic models of wind farms with fixed speed wind turbines

The increasing wind power penetration on power systems requires the development of adequate wind farms models for representing the dynamic behaviour of wind farms on power systems. The behaviour of a wind farm can be represented by a detailed model including the modelling of all wind turbines and the wind farm electrical network. But this detailed model presents a high order model if a wind farm with high number of wind turbines is modelled and therefore the simulation time is long. The development of equivalent wind farm models enables the model order and the computation time to be reduced when the impact of wind farms on power systems is studied. In this paper, equivalent models of wind farms with fixed speed wind turbines are proposed by aggregating wind turbines into an equivalent wind turbine that operates on an equivalent wind farm electrical network. Two equivalent wind turbines have been developed: one for aggregated wind turbines with similar winds, and another for aggregated wind turbines under any incoming wind, even with different incoming winds.The proposed equivalent models provide high accuracy for representing the dynamic response of wind farm on power system simulations with an important reduction of model order and simulation time compare to that of the complete wind farm modelled by the detailed model.     

基于随机组合赋权模糊评价的风电机组健康状态评估

由于健康指标权重随机性会导致风电机组状态评估灵敏度降低,提出一种评估风电机组健康状态的随机组合赋权模糊评价方法。首先,通过相关性、方差、偏度等多角度分析风电场采集与监视控制系统（SCADA）数据,结合IEC61400-1标准建立机组健康状态评估指标架构,并基于随机因子优化组合权重得到赋权公式,提高评估指标层权重的准确性。其次,为充分覆盖评估指标数据劣化度,基于岭型分布函数建立健康指标劣化隶属度计算函数。结合随机组合权重和隶属度函数,构建风电机组健康状态模糊综合评价数学模型。通过分层评估风电机组健康状态指标架构,得到机组健康等级并实现故障预警。最后,对大连驼山风电场多台机组进行评估试验,结果表明：该文方法能准确评估出风电机组健康状态等级,相比组合赋权云模型方法,灵敏度提高了1.85%。     

基于风电机组状态的超短期海上风电功率预测

提出一种基于风电机组状态的超短期海上风电功率预测模型。首先,综合考虑海上环境因素以及风电机组部件间的相互作用建立指标的预测模型,以长短期记忆神经网络的预测误差作为监测指标的动态劣化度;然后采用模糊综合评价法对风电机组的运行状态进行评估,依据评估结果对风电机组历史运行数据进行划分;最后根据分类后历史运行数据建立基于机组状态的超短期风电功率预测模型。结合国内某海上风电场实例数据进行分析,算例结果表明所提方法可有效提高风电功率预测精度。     

Nonlinear system identification for model-based condition monitoring of wind turbines

This paper proposes a data driven model-based condition monitoring scheme that is applied to wind turbines. The scheme is based upon a non-linear data-based modelling approach in which the model parameters vary as functions of the system variables. The model structure and parameters are identified directly from the input and output data of the process. The proposed method is demonstrated with data obtained from a simulation of a grid-connected wind turbine where it is used to detect grid and power electronic faults. The method is evaluated further with SCADA data obtained from an operational wind farm where it is employed to identify gearbox and generator faults. In contrast to artificial intelligence methods, such as artificial neural network-based models, the method employed in this paper provides a parametrically efficient representation of non-linear processes. Consequently, it is relatively straightforward to implement the proposed model-based method on-line using a field-programmable gate array.     

Wind farm layout optimization using area dimensions and definite point selection techniques

Wind turbines are the biggest rotating machines on earth, operating in the lowest part of the earth boundary layer. Designing the layout scheme of wind farms is a challenging job to researchers, as there are many design objectives and constraints due to the multiple wake phenomena. This paper proposes an area rotation method to find the optimum dimensions of the wind farm shape, where maximum area could face the free stream velocity. Afterwards, a novel method called Definite Point Selection (DPS) is developed to place the turbines in order to operate at maximum, while providing obligatory space between adjacent turbines for operation safety. This method can be used to identify the zero wake effect points at wind farm. The result from this study shows that the proposed method is more effective to increase the overall power of a wind farm than the previous methods. Also, the power output of the wind farm by using combined area rotation and DPS methods was increased even when using the same number of wind turbines.     

Design and implementation of wind energy system in Saudi Arabia

This paper introduces an accurate procedure to choose the best site from many sites and suitable wind turbines for these sites depending on the minimum price of kWh generated (Energy Cost Figure (ECF)) from wind energy system. In this paper a new proposed computer program has been introduced to perform all the calculations and optimization required to accurately design the wind energy system and matching between sites and wind turbines. Some of cost calculations of energy methods have been introduced and compared to choose the most suitable method. The data for five sites in Saudi Arabia and hundred wind turbines have been used to choose the best site and the optimum wind turbine for each site. These sites are Yanbo, Dhahran, Dhulom, Riyadh, and Qaisumah. One hundred wind turbines have been used to choose the best one for each site. This program is built in a generic form which allows it to be used with unlimited number of sites and wind turbines in all over the world. The program is written by using Visual Fortran and it is verified with simple calculation in Excel. The paper showed that the best site is Dhahran and the suitable wind turbine for this site is KMW-ERNO with 5.85 Cents/kWh. The worst site to install wind energy system is Riyadh with minimum price of kWh of 12.81 Cents/kWh in case of using GE Energy 2 wind turbine.     

Prediction of seismic loadings on wind turbine support structures by response spectrum method considering equivalent modal damping of support structures and reliability level

In this study, a new damping correction factor is proposed to provide an accurate design response spectrum for megawatt (MW) class wind turbines. The predicted response spectra show good agreement with those by time history analysis (THA). An equivalent modal damping of wind turbine support structures is then proposed for response spectrum method (RSM) based on the modal decomposition method for non‐classically damped structures. Seismic loadings on wind turbine towers and footings by RSM with the proposed damping correction factor and equivalent modal damping are also investigated and compared with those by THA. Finally, a quantile value between 0.5 and 0.85 in the damping correction factor is calibrated to ensure the same reliability level as evaluated by THA currently used for estimation of seismic loadings on support structures.     

Dynamic model of wind energy conversion systems with PMSG-based variable-speed wind turbines for power system studies

In order to study the impact of a wind farm on the dynamics of the power system, a significant issue is to develop appropriate equivalent models that allow characterizing the dynamics of all individual wind turbine generators (WTGs) composing the park. In this sense, with the advance of power electronics, direct-driven permanent magnet synchronous generators (PMSGs) have drawn increased interest to wind turbine manufacturers due to their advantages over other variable-speed WTGs. These include the possibility of multi-pole design with a gearless construction that offers slow speed operation and reduced maintenance since no brushes are used, elimination of the excitation system, full controllability for maximum wind power extraction and grid interface, and easiness in accomplishing fault-ride through and grid support. In this way, this paper presents a comprehensive dynamic equivalent model of a wind farm with direct-driven PMSG wind turbines using full-scale converters and its control scheme. The proposed simplified modelling is developed using the state-space averaging technique and is implemented in the MATLAB/Simulink environment. The dynamic performance of the wind farm and its impact on the power system operation is evaluated using the phasor simulation method.     

A new approach to optimise placement of wind turbines using particle swarm optimisation

In the present study, particle swarm optimisation has been used to resolve the placement of wind turbines in a wind park giving maximum power and efficiency with minimum number of turbines. Unlike past approaches where each plot was subdivided into smaller square grids at the centre of which a turbine can be placed, the present study does not require division of the plot. Thus, a turbine now has more flexibility to be placed anywhere outside a radius of 200 m of each other yielding better results. The case of unidirectional uniform wind is considered in this study. Along with the optimal layout, fitness value, total power output, efficiency and number of turbines have also been reported. Comparison with results of earlier study and possible explanation is also provided.     

Large‐eddy simulation of turbulent flow past wind turbines/farms: the Virtual Wind Simulator (VWiS)

A large‐eddy simulation framework, dubbed as the Virtual Wind Simulator (VWiS), for simulating turbulent flow over wind turbines and wind farms in complex terrain is developed and validated. The wind turbines are parameterized using the actuator line model. The complex terrain is represented by the curvilinear immersed boundary method. The predictive capability of the present method is evaluated by simulating two available wind tunnel experimental cases: the flow over a stand‐alone turbine and an aligned wind turbine array. Systematic grid refinement studies are carried out, for both single turbine and multi‐turbine array cases, and the accuracy of the computed results is assessed through detailed comparisons with wind tunnel experiments. The model is further applied to simulate the flow over an operational utility‐scale wind farm. The inflow velocities for this case are interpolated from a mesoscale simulation using a Weather Research and Forecasting (WRF) model with and without adding synthetic turbulence to the WRF‐computed velocity fields. Improvements on power predictions are obtained when synthetic turbulence is added at the inlet. Finally the VWiS is applied to simulate a yet undeveloped wind farm at a complex terrain site where wind resource measurements have already been obtained. Good agreement with field measurements is obtained in terms of the time‐averaged streamwise velocity profiles. To demonstrate the ability of the model to simulate the interactions of terrain‐induced turbulence with wind turbines, eight hypothetical turbines are placed in this area. The computed extracted power underscores the significant effect of site‐specific topography on turbine performance. Copyright © 2014 John Wiley & Sons, Ltd.     

基于加装叶尖小翼风电机组发电量提升试验研究

针对老旧风电场由于风电机组风轮和风资源未能很好匹配等原因导致的发电量不理想问题,提出一种基于加装叶尖小翼风电机组发电量提升方法,该方法在增加叶片扫掠面积的同时有效改善叶片的气动性能。通过加装叶尖小翼增加叶尖部分切向力,增加主轴扭矩从而提高风轮吸收功率,达到提升发电量的目的。基于风电场实际试验数据对提功增效效果进行分析,结果表明所提方法在满足安全性的前提下可有效提高机组输出功率,提升发电量。同时该方法成本低,展现了良好的性价比。     

某风电场风力发电机组故障诊断

为了准确判断风电机组的运行状态及故障,提出了基于常规分析—振动幅值分析—波形频谱分析的故障诊断流程,阐述了针对风电机组的幅值分析方法和波形频谱分析方法,并通过对某机组异响的根源探究实例,准确地诊断出机组异响来源于齿轮箱太阳轮,可为风电机组故障诊断技术提供依据。     

基于风向预测的新型偏航控制方法

提出一种基于风向预测的新型控制方案,该控制方案涉及一种新颖的控制结构,包含风向预测模型和新型偏航控制。在上述控制结构下,利用基于自回归综合移动平均线的卡尔曼滤波模型来预测风向,同时提出一种基于有限控制集的模型预测控制方法。为证明所提方案的可行性和优越性,开发一种新型偏航控制器并用工业数据进行仿真测试,然后将其性能与工业偏航控制器相比,结果表明新型偏航控制器具有更小的偏航误差,因此增加了最大风力获取能力。