适用于双馈风机的并网电压波动与 闪变检测系统的研究

风电因电能质量问题影响使其发展受到制约,电压波动及闪变是其中之一。使用目前的闪变仪对风电机组并网引起电压闪变进行检测,发现在检测低频段波动引起的闪变时误差较大,而这也是风电并网产生闪变的主要频段。因此,如何使低频段检测误差减小是该文研究的意义。根据IEC标准,在Matlab平台建立数字闪变检测系统仿真模型,并利用双线性方法求得系统的参数。针对上述情况,分析其误差产生的原因,通过对检测的瞬时闪变视感度S（t）引入参数校正以减小低频检测误差,使其满足风电并网闪变值检测的要求。最后将修正系数后的检测系统运用在一个双馈风力发电系统实例中,证明该风电场满足我国电压闪变值要求。     

考虑风资源影响的风电场电压波动和闪变评估

风电并网后引起的电压波动和闪变水平可能超出国家有关标准,造成严重的电能质量问题,因此,在风电并网之前需对这两者进行评估。采用了一种新的评估方法。区别于国际电工标准(IEC61400-21)中电压波动与闪变的评估,此方法考虑了风电场的风资源情况对这2个指标的影响。对风电场在不同出力下由阵风引起系统的电压波动进行计算,并用IEC闪变仪计算短时间闪变值Pst。用所提方法和IEC标准对我国某一新建的风电场进行评估。结果表明,所提方法不仅能有效地进行电压波动与闪变评估,而且能更好地考虑风速变化对风电场带来的潜在影响。     

分布式发电引起的电压波动和闪变

从并网分布式发电（DG）的输出功率波动出发。分析了分布式发电引起电网电压波动和闪变的主要原因。随后提出了基于潮流计算的闪变预测算法，用于识别闪变值最大的母线。基于matlab／simulink的电磁暂态仿真被用来准确计算电压波动和闪变。最后给出了一个算例，分析了机组爬坡和退出以及机组功率波动时的闪变情况。仿真结果显示，逆变型分布式电源引入的电压闪变很小，异步发电机的功率波动是造成电网电压闪变的主要原因。     

基于Matlab/Simulink的风力发电机组电压波动与闪变仿真分析

风力发电机组连接到电网之后产生闪变,这会影响风力发电系统的稳定性。文章根据国际电工委员会标准,通过Matlab/Simulink采用统计排序法,对风力发电机组电压波动与闪变进行仿真分析。仿真结果表明:文章设计的闪变测量系统可以验证所设计各滤波器的准确性;对于两种形状的电压波动信号,正弦波信号和矩形波信号,可以得到瞬时闪变觉察度的值均为1以及短时间闪变值P_(st)的仿真值,与理论值进行对比,测量误差均未超过5%,符合IEC标准的要求,。     

风力发电机组电压波动与闪变分析研究

风力发电机组与中压电网连接,中压电网通常连接有其它波动性负荷,在被测风力发电机组输出端可能引起显著的电压波动,电网特性决定了风力发电机组产生电压波动的程度。为了避免电网实际电压波动对测量点闪变的直接影响,文章在研究了标准推荐的闪变值计算方法基础上,分别计算直驱永磁型风力发电机组和双馈异步型风力发电机组的闪变值,分析风力发电机组闪变值的影响因素。对比虚拟电网计算闪变值和理想电压条件下测量闪变值,验证虚拟电网方法的有效性。     

基于Hilbert-Huang变换的风电场闪变

随着风电场装机容量的增大,风电并网所带来的电压偏差、谐波污染、电压波动和闪变等电能质量问题日益严重,因此,需要对其进行评估和治理,而评估和治理的前提是参数的准确检测。将一种新的非平稳信号处理方法,即Hilbert-Huang变换用于风电场闪变的分析。该方法可以从频域和时域同时对信号进行分析,能够准确检测出非平稳电压闪变信号的时间、频率和幅值信息。仿真分析结果表明了该方法分析风电场闪变的有效性。     

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。     

炼钢电弧炉引起的电压波动闪变及其抑制措施

本文叙述炼钢电弧炉引起的电压波动、闪变模式、限值和通常采取的抑制措施。文中详细地介绍了国际电工委员会和各国（包括我国）标准有关电压波动、闪变限值规定。在抑制措施中，提出了我国近年来采用ＳＶＣ（静止型无功功率补偿装置）来改善闪变中一些值得注意的问题，并例举了不少交流电弧炉闪变抑制的测定。     

数字式电压闪变测试仪研制成功

一种用于监测电网电压闪变的专用测量仪器—VF—9101型数字式电压闪变测试仪日前已由陕西机械学院和西北电业管理局联合研制成功,并通过陕西省科技成果鉴定。有关专家认为VF-9101型数字式电压闪变测试仪设计合理,性能齐全,测试数据可靠,具有80年代国际水平,填补国内空白。这项仪器的研制成功,实现了闪变测试仪的国产化,可以替代进口,节省外汇,对推动国标GB12326-90《电能质量 电压允许波动和闪变》的实施,对改善我国电能质量具有重要的实际意义。     

交流电弧炉的电压闪变及计算

炼钢交流电弧炉在冶炼过程中会对输配电网络产生较大的冲击,使得电压波动及闪变.以“电压闪变”为研究对象,着重分析其电气特性,并对其进行工程计算,从而对电压波动与闪变有一个较完整的认识,并应用于实际工程设计及设备制造中.     

A frequency domain approach to wind turbines for flicker analysis

Wind turbines may have an important impact on power quality. Flicker is a more serious issue for fixed-speed wind turbines because these turbines produce electric power following the variations of the incident wind. During continuous operation, wind variations will result in power fluctuations and consequently in voltage fluctuations. It is necessary to evaluate wind turbines flicker emission level, and traditionally time domain simulations have been used to perform the analysis. This paper presents a complete frequency domain model to study flicker produced during wind turbines continuous operation. The model includes a realistic wind speed model as observed by the wind turbine and also a frequency domain induction generator model is presented. The frequency domain model has been compared with a time domain model. The frequency domain approach, as shown in the paper, may be very useful for flicker analysis in electric networks.     

Assessment of flicker limits compliance for wind energy conversion system in the frequency domain

Fixed-speed wind turbines produce voltage flicker during switching operations and they also produce flicker during continuous operation. In order to avoid power quality problems to consumers, it would be important to predict flicker emission from wind turbines at a certain site previously to installation. This paper focuses on a method to perform a fast flicker analysis caused by grid-connected fixed-speed wind turbines in continuous operation. The method has been developed completely in the frequency domain, including wind turbines. This method predicts the P_st value for each node system. Applying this method there would be no need to perform measurements in every node, which would be nearly impossible or to simulate the whole model in the time domain, demanding an enormous computational effort and storage capacity. The performance of the frequency domain method is applied to analyze different wind energy generation scenarios to assess their influence in a real power system.     

太阳能烟囱发电和海水淡化综合系统的初步研究

提出了太阳能烟囱海水淡化及热风发电综合系统。以天津地区的气候条件为准,估算出此系统每平方米集热棚面积可年产1.0kWh的电量和0.74t的淡水。对建立的小型冷凝实验验证系统中的冷空气风速、冷凝水产量及温度场进行了测量,给出了高浓度不凝气体—水蒸气间壁冷凝换热的水蒸气冷凝速率模型和理论风速计算公式,用来关联不凝气体浓度、温度等对冷凝换热的影响,为将来综合系统的优化提供理论依据。并根据实验数据对冷凝系统进行了初步设计。     

Analysis of mechanical power fluctuations in asynchronous WECs

In recent years, wind energy has become an important part of electrical power generation in some countries. Some problems such as small voltage variations and flicker can be caused by wind turbines and wind farms, when wind speed variations produce mechanical power fluctuations. The consequence is that speed changes in the turbine rotor are produced, which lead to variations in their currents and voltages. The purpose of this paper is to study the relationship between fluctuations of mechanical power, rotor speed and currents as a function of their frequencies, in order to establish the models that should be used to analyse slow voltage variations and flicker problems. Simulations are carried out using a dynamic model of the induction machine and assuming sinusoidal waveforms for the fluctuations of the mechanical power     

Flicker Mitigation by Active Power Control of Variable-Speed Wind Turbines With Full-Scale Back-to-Back Power Converters

Grid-connected wind turbines are fluctuating power sources that may produce flicker during continuous operation. This paper presents a simulation model of a megawatt-level variable-speed wind turbine with a full-scale back-to-back power converter developed in the simulation tool of PSCAD/EMTDC. Flicker emission of this system is investigated. Reactive power compensation is mostly adopted for flicker mitigation. However, the flicker mitigation technique shows its limits, when the grid impedance angle is low in some distribution networks. A new method of flicker mitigation by controlling active power is proposed. It smoothes the 3p active power oscillations from wind shear and tower shadow effects of the wind turbine by varying the dc-link voltage of the full-scale converter. Simulation results show that damping the 3p active power oscillation by using the flicker mitigation controller is an effective means for flicker mitigation of variable-speed wind turbines with full-scale back-to-back power converters during continuous operation.      

风机并网对电能质量影响因子研究

为了给电网控制策略提供可靠的参考依据,对电网在接入风机后电能质量的变化进行了详尽的分析。风机作为电源同时也作为非线性负载接入配电网中使得电能质量的分析更加复杂。首先对国标中着重介绍的稳态电能质量：电压偏差,三相不平衡度,谐波以及电压波动进行理论介绍,然后在Matlab／Simulink上建立了配电系统与风机并网的模型,得到风机对电能质量不同方面的影响程度,最后采用先进电力电子设备为平稳电压电流输出提供一定的方法,并进行验证。研究结果表明,电力谐波和电压波动闪变是风机对电网的最主要的影响因素。     

Flicker study on variable speed wind turbines with doubly fed induction generators

Grid connected wind turbines may produce flicker during continuous operation. This paper presents a simulation model of a MW-level variable speed wind turbine with a doubly fed induction generator developed in the simulation tool of PSCAD/EMTDC. Flicker emission of variable speed wind turbines with doubly fed induction generators is investigated during continuous operation, and the dependence of flicker emission on mean wind speed, wind turbulence intensity, short circuit capacity of grid and grid impedance angle are analyzed. A comparison is done with the fixed speed wind turbine, which leads to a conclusion that the factors mentioned above have different influences on flicker emission compared with that in the case of the fixed speed wind turbine. Flicker mitigation is realized by output reactive power control of the variable speed wind turbine with doubly fed induction generator. Simulation results show the wind turbine output reactive power control provides an effective means for flicker mitigation regardless of mean wind speed, turbulence intensity and short circuit capacity ratio.     

Wind turbine angular frequency analysis by means of computer vision techniques

The turbine synchronization phenomenon is of great interest in order to estimate the flicker produced by a wind farm. This paper proposes an initial approach to analyze the appearance of this phenomenon by the use of various image processing techniques: a method to automatically calculate the angular frequency of an unknown number of wind turbines from a video. The recorded video images were obtained at the Manzanal wind farm, province of León (Spain).     

Modeling and experimental verification of grid interaction of a DFIG wind turbine

The response of the doubly fed induction generator (DFIG) wind turbine system to grid disturbances is simulated and verified experimentally. The results are compared to the response that a fixed-speed wind turbine would have given. A voltage sag to 80% (80% remaining voltage) is handled very well, which is not the case for a fixed-speed wind turbine. A second-order model for prediction of the response of DFIG wind turbines is derived, and its simulated performance is successfully verified experimentally. The power quality impact by the DFIG wind turbine system is measured and evaluated. Steady-state impact, such as flicker emission, reactive power, and harmonic emission, is measured and analyzed. It is found that the flicker emission is very low, the reactive power is close to zero in the whole operating range, and the current THD is always lower than 5%.