考虑调压裕度的风电场无功电压控制策略北大核心CSCD

针对风电场并网带来的电压稳定问题,文章提出了考虑调压裕度的无功电压控制策略。采用分层控制技术,首先通过无功整定层计算风电场无功输出参考值;其次在无功分配层考虑无功补偿装置与风电机组自身的调压裕度,选择相应的无功补偿方法,优先选用风电场配置的无功补偿装置进行无功调节。若补偿装置无法满足电压稳定要求,则根据各风电机组的运行状态,将无功补偿值按照无功容量比例算法进行分配,风电机组的网侧变流器采用自适应下垂控制以实现最大无功容量补偿。若无功缺额依然存在,需要对风电机组进行减载控制以实现对电网电压的无功支撑;最后,通过PSCAD/EMTDC仿真平台对所提策略的有效性进行了验证。     

大规模风电集中接入弱电网后的无功电压紧急控制初探

针对大规模风电集中接入弱电网后的地区电网无功电压控制问题,归纳了风电机组大规模脱网事故集中暴露的问题及事后改进情况,提出了暂态电压偏移越限是风电机组具备故障穿越能力后仍然会不同程度脱网的重要原因,分析了暂态电压偏移的机理,探讨了抑制暂态电压偏移越限的无功电压紧急控制措施。     

基于改进网侧控制策略的半直驱风电系统FFRT研究

[目的]为改进半直驱风电系统的故障电压穿越（Flexible Fault Ride Through, FFRT）能力,提出采用电网故障时无功优先的改进网侧控制策略。[方法]在分析传统网侧控制策略的基础上,根据最新的故障电压穿越能力测试规程在传统网侧控制加入无功优先控制,在电网暂态故障期间优先向电网注入无功电流支撑电网电压恢复。根据改进网侧控制策略,对电网深度跌落和升高时采用卸荷电路结合改进网侧控制策略实现了风电机组的FFRT仿真运行,结合某项目6 MW半直驱风电机组,采用移动故障电压穿越测试设备进行故障电压现场测试。[结果]测试和仿真结果表明,改进网侧控制策略可提升半直驱风电系统的FFRT运行,无功电流稳定控制。[结论]改进网侧控制策略可在多种对称低电压/高电压故障工况和不对称高电压故障工况下优先向电网注入对应的稳定无功电流,有利于辅助电网电压恢复和提升半直驱风电系统的FFRT能力。     

风电机组集群协同电压控制方法

大规模风电并网后,为维持并网点电压稳定,需要实时调节每个风电机组的无功输出功率。传统集中式方法系统维度高,而分散式方法收敛速度慢。文章提出一种面向并网点电压稳定的风电机组集群协同控制方法。首先,在每个风电机组子集群中设置边缘计算装置,负责更新子集群内机组的无功输出功率以及对子集群内控制模型的降阶;然后,云端控制中心以并网点电压波动最小化为目标,更新每个子集的总无功功率输出参考值,同时更新过程考虑了信息交互过程中通信延时的影响;最后,仿真结果表明,与传统方法相比,所提方法的发电机组无功功率响应速度得到了大幅度提升。     

风电机组并网过程对电网的影响

论述了风电机组并网过程对电网电压造成的影响,对变速恒频风电机组和定桨失速风电机组的并网特性做了分析,提出在弱电网条件下在风电场安装静止无功补偿器的必要性。     

低风速分散式风电并入配电网的双层电压优化模型

从规划和运行2个角度出发,提出一种针对低风速风电机组并入配电网的双层电压优化模型。上层模型计及低风速的波动性、负荷的随机性与用户行为特性,求解以网损、电压偏差、电压稳定性指标和分散式风电总投资为目标函数的多目标规划问题,同时利用Q-V曲线法获得静止无功补偿器(SVC)的最佳接入位置;下层模型建立基于模糊逻辑的低风速风电机组与SVC协调调压的无功控制策略。最后通过仿真验证所提方法不仅能够实现电压优化控制,而且能显著改善配电网的整体电压分布。     

千万千瓦级风光并网系统电压无功研究

为了保证大规模风光电源接入条件下西北电网的运行安全,对河西千万千瓦级风光电源接入情况下的系统电压波动及其相应的无功调节进行了研究。针对新能源机组出力由零到最大出力变化时带来的系统电压波动,讨论了静止无功补偿器(static var compensator,SVC)的安装容量及装设位置,以抑制系统母线电压波动。针对受扰系统在故障切除后的恢复过程出现高电压引起的风电机组大规模脱网问题,改变系统动态无功补偿装置控制参数及新能源机组无功控制方式,探讨了动态无功补偿装置控制参数及新能源机组无功控制方式对新能源机组脱网的影响,并对系统的动态无功补偿装置的配置及机组无功控制方式提出合理建议。     

基于风电机组无功响应速度的风电场闪变研究

针对风电机组无功响应速度对风电场并网点电压闪变的影响,从风力发电机组特性出发,基于DIg SILENT建立了含风电机组的电网仿真模型,研究风速波动时风机无功响应速度对风电场并网点电压波动与闪变的影响。算例结果表明:风电机组无功响应速度对并网点电压闪变的影响程度与系统短路容量密切相关,加快风电机组无功响应速度能有效抑制风电场并网点的电压闪变。     

基于变功率因数的分散式风电场优化运行策略

提出一种考虑负荷类型和风电机组无功极限的分散式风电场优化运行策略。建立基于静态电压特性的典型负荷通用模型;挖掘分散式风电机组无功能力,采用机端并联电容器平衡并提高双馈感应发电机无功调节能力;分析风电机组功率因数对配电网各节点电压、有功和无功网损影响规律;在此基础上,提出基于改进萤火虫算法的分散式风电场最优功率因数运行方法。基于IEEE-33节点模型进行仿真计算,结果表明:分散式风电场小范围功率因数优化调节可有效减小配电网网损,提高电压稳定性。     

基于安全电压的双馈风电机组高电压穿越判别方法

基于双馈风电机组的动态无功支持能力,在电网电压骤升时协调控制网侧变流器和发电机定子输出的无功功率,维持直流侧母线电压的安全稳定运行。根据DFIG直流侧电容的高电压穿越安全要求,定义了电网电压骤升时双馈风力发电机组接入电压的安全电压。然后基于安全电压给出了DFIG在电网电压骤升时能否实现高电压穿越的判断依据,并给出了其高电压穿越时的无功协调输出策略。仿真结果验证了所提的方法。     

风 风能 风力发电——21世纪新型清洁能源

一风的一般属性１风的形成风是人们非常熟悉的一种自然现象，人人都能感觉到它的存在。春风和煦，给万物带来生机；夏风吹拂，使人心旷神怡；秋风送爽，带来丰收的喜悦；冬风呼啸，迎来漫天飞雪。那么风是怎样形成的呢？众所周知，人类生活的地球表面被大气所包围，来自太阳的辐射不断传送到地球表面，因太阳辐射受热情况不同，地球表面各处的气温不同。在影响气压高低的因素中，气温起着最重要的作用。温度高的地区空气受热上升，气压减小；温度低的地方，空气下降，气压增大，于是产生了气压差。和水往低处流一样，空气也从气压高处向气压…     

风电场风电机组的接地设计

较系统地介绍了风电场风电机组对接地电阻的要求、接地设计思路及方法,并提供实际工程中接地网布置图实例作为参考。     

Evaluation of wind farm efficiency and wind turbine wakes at the Nysted offshore wind farm

Here, we quantify relationships between wind farm efficiency and wind speed, direction, turbulence and atmospheric stability using power output from the large offshore wind farm at Nysted in Denmark. Wake losses are, as expected, most strongly related to wind speed variations through the turbine thrust coefficient; with direction, atmospheric stability and turbulence as important second order effects. While the wind farm efficiency is highly dependent on the distribution of wind speeds and wind direction, it is shown that the impact of turbine spacing on wake losses and turbine efficiency can be quantified, albeit with relatively large uncertainty due to stochastic effects in the data. There is evidence of the ‘deep array effect’ in that wake losses in the centre of the wind farm are under‐estimated by the wind farm model WAsP, although overall efficiency of the wind farm is well predicted due to compensating edge effects. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamic wind estimation based control for small wind turbines

We introduce a novel scheme for small wind turbines that gives dynamic estimation of wind speed from rotor angular velocity measurements. The estimation proceeds in two different dynamic observers, one giving a valid estimate for higher Tip Speed Ratios (TSRs) and which we call the Upper Wind Estimator (UWE) and the other called the Lower Wind Estimator (LWE) valid for lower TSRs. The meaning of “higher” and “lower”, and the precise regions of validity, are quantified. We further propose a coordinated control scheme using the UWE. Simulations are presented showing closed-loop performance of the turbine and the estimators both in the optimal TSR regulation condition, and the dynamic power-shedding condition caused by a wind gust. An analytic analysis of closed-loop stability and of the convergence and bias properties of the estimator is provided. Empirical data showing performance on a real turbine is also presented.     

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。     

适用于特殊风区的风电机组塔架的再设计

由于IECⅠ级机型性能不能满足超Ⅰ类风区的要求,因此以IECⅠ级机型塔架的结构为基础,对其进行了再设计,并利用有限元方法,对再设计后的塔架的静强度、模态、稳定性进行了分析。分析结果表明:再设计后的塔架的强度、固有频率和刚度均满足要求;以满足强度、频率特性和刚度为约束条件,以减轻重量、降低成本为目标的塔架的再设计是可靠的。     

Simulation of hourly wind speed and array wind power

Statistical summaries of wind speed are sufficient to compute many characteristics of turbine-generated power, such as the mean, variance and reliability of various power levels. However, a wind speed time series is necessary to produce a sequence of power values as used for investigating load matching and storage requirements. Since a long historical record of wind speed may not be available at a wind turbine candidate site, it is desirable to be able to generate a simulated numerical sequence of hourly wind speed values. Two such approximate procedures are developed in this paper. One procedure generates sequential wind speed values at a site based on the Weibull parameters of hourly wind speed and the lag-one autocorrelation of hourly wind speed values. Comparison with historical data at a site is made. The second procedure generates sequential hourly wind power values for a regional array of wind turbines. It utilizes the typical site wind characteristics, the spatial and lag-one cross correlation and autocorrelation of hourly wind speed values and an equivalent linearized relationship between array average wind speed and array power. Comparison with results for six different wind turbines in three different regional arrays indicates good agreement for wind power histograms, autocorrelation function and mean persistence.     

Characterization of wind speed data according to wind direction

Knowledge of the wind speed distribution and the most frequent wind directions is important when choosing wind turbines and when locating them. For this reason wind evaluation and characterization are important when forecasting output power. The data used here were collected from eleven meteorological stations distributed in Navarre, Spain. We obtained data for the period extending from 1992 to 1995, with each datum encompassing 10 minutes of time. Wind speed data of each station were gathered in eight directional sectors, each one extended over 45 degrees according to the direction from which the wind blows. The stations were grouped in two blocks: those under the influence of the Ebro valley and those in mountainous areas. For each group the Weibull parameters were estimated, (according to the Weibull probability paper because the Weibull distribution gives the best fit in this region). Kurtosis and skewness coefficients were estimated as well. The Weibull parameters, especially the scale parameter c, depend strongly on the direction considered, and both Weibull parameters show an increasing trend as the direction considered moves to the more dominant direction, while both kurtosis and skewness show a corresponding decreasing trend.     

A new formulation for rotor equivalent wind speed for wind resource assessment and wind power forecasting

The spurt of growth in the wind energy industry has led to the development of many new technologies to study this energy resource and improve the efficiency of wind turbines. One of the key factors in wind farm characterization is the prediction of power output of the wind farm that is a strong function of the turbulence in the wind speed and direction. A new formulation for calculating the expected power from a wind turbine in the presence of wind shear, turbulence, directional shear and direction fluctuations is presented. It is observed that wind shear, directional shear and direction fluctuations reduce the power producing capability, while turbulent intensity increases it. However, there is a complicated superposition of these effects that alters the characteristics of the power estimate that indicates the need for the new formulation. Data from two field experiments is used to estimate the wind power using the new formulation, and results are compared to previous formulations. Comparison of the estimates of available power from the new formulation is not compared to actual power outputs and will be a subject of future work. © 2015 The Authors. Wind Energy published by John Wiley & Sons, Ltd.     

Convertible wind energy based on predicted wind speed at hub-height

Support vector machine is proposed to find wind speed at higher heights using measurements at lower heights. The mean absolute percentage error between measured and the estimated wind speed at height 40 m is found to be satisfactory. After validation at 40 m, the model was used to calculate the wind speed at hub heights up to 100 m. Annual energy yield was found to be increasing with hub height and, hence, accurate estimation of wind speed at heights becomes essential for realistic wind energy assessment. Furthermore, the plant capacity factor was found to be increasing approximately 1% for each 10-m increase in hub height.