红外成像在羽流撞击平板热效应试验中的应用

为了研究发动机羽流撞击平板的热效应,通过在风洞内建立羽流流场,利用红外热像仪测量平板模型的表面温度,进而获得不同推力产生的羽流撞击平板的热流率分布.首先回顾了高空羽流污染及其效应研究所开展的工作,接着介绍了试验研究所使用的高超声速低密度风洞、红外热像仪等主要仪器设备的性能参数以及平板模型的外形特征,其次给出了2 N与10 N推力的试验条件、热流处理方法、试验结果及其讨论.最后研究了推力喷管轴线与平板距离变化对羽流撞击平板的热效应影响.结果表明:发动机喷管轴线与平板的距离不同,羽流撞击产生的高热流率区域的位置与大小也不相同,距离越小,高热流区域越靠近平板前缘,产生的热效应也越强.     

Extreme learning machine approach for sensorless wind speed estimation

Precise predictions of wind speed play important role in determining the feasibility of harnessing wind energy. In fact, reliable wind predictions offer secure and minimal economic risk situation to operators and investors. This paper presents a new model based upon extreme learning machine (ELM) for sensor-less estimation of wind speed based on wind turbine parameters. The inputs for estimating the wind speed are wind turbine power coefficient, blade pitch angle, and rotational speed. In order to validate authors compared prediction of ELM model with the predictions with genetic programming (GP), artificial neural network (ANN) and support vector machine with radial basis kernel function (SVM-RBF). This investigation analyzed the reliability of these computational models using the simulation results and three statistical tests. The three statistical tests includes the Pearson correlation coefficient, coefficient of determination and root-mean-square error. Finally, this study compared predicted wind speeds from each method against actual measurement data. Simulation results, clearly demonstrate that ELM can be utilized effectively in applications of sensor-less wind speed predictions. Concisely, the survey results show that the proposed ELM model is suitable and precise for sensor-less wind speed predictions and has much higher performance than the other approaches examined in this study.     

变速恒频双馈风力发电机的矢量控制研究

由于DFIG（双馈发电机）是高阶多变量,强耦合、非线性的机电系统,传统的控制方法无论是在控制精度上还是在动态性能上,远不能达到要求,为了实现DFIG的高性能控制,应采用磁场定向的矢量变换控制技术。借鉴矢量变换技术对于一般交流电机的控制,把矢遁变换控制技术用于对DFIG的控制,通过建立Matlab／Silnulink模型,和仿真征明矢量控制对DFIG良好的控制性。     

Development, implementation, and testing of fault detection strategies on the National Wind Technology Center’s controls advanced research turbines

The National Renewable Energy Laboratory’s National Wind Technology Center dedicates two 600 kW turbines for advanced control systems research. A fault detection system for both turbines has been developed, analyzed, and improved across years of experiments to protect the turbines as each new controller is tested. Analysis of field data and ongoing fault detection strategy improvements have resulted in a system of sensors, fault definitions, and detection strategies that have thus far been effective at protecting the turbines. In this paper, we document this fault detection system and provide field data illustrating its operation while detecting a range of failures. In some cases, we discuss the refinement process over time as fault detection strategies were improved. The purpose of this article is to share field experience obtained during the development and field testing of the existing fault detection system, and to offer a possible baseline for comparison with more advanced turbine fault detection controllers.     

1993年汛期黄河下游河势遥感调查

利用ＭＥＲＩＤＩＡＮ遥感图象处理系统，通过ＴＭ图象最佳波段组合、线性拉伸放大、密度分割等处理手段，首次在黄河上进行了卫星遥感河势调查，其优势在于：（１）可以弥补目估河势的不足；（２）能够对河势流路、主流线位置、洪漫滩范围及水边线、生产堤、主要滩区洪水进出口门位置、进水和水围村庄等准确定位；（３）可以详细计算各类滩区面积与分布密度。     

Insights in wind turbine drive train dynamics gathered by validating advanced models on a newly developed 13.2 MW dynamically controlled test-rig

Guaranteeing reliable and cost-effective wind turbine drive trains requires expert insights in dynamics during operation. A combination of advanced modeling techniques and detailed measurements are suggested to realize this goal. The flexible multibody modeling technique enables the simulation of dynamic loads on all drive train components. Moreover it facilitates estimation of structural component deformation caused by dynamic loading. This paper gives a detailed overview of the assumptions made in this modeling approach. Furthermore the influence of the different structural component flexibilities is investigated in detail. To gain confidence in the models created, model validation by means of a comparison with measurements is necessary. To overcome issues concerning test repeatability experienced in field testing, test-rig testing is suggested as a valid alternative. In order to be representative, dedicated dynamic load cases, which represent specific dynamic behavior of the gearbox in a wind turbine need to be realized on the test-rig. However a highly dynamic test-rig complying with the specifications was not commercially available. Therefore Hansen developed a high dynamic test-rig with a nominal power of 13.2 MW and a peak power capacity of 16.8 MW. A back-to-back gearbox configuration was used. The complexity of controlling dynamics of the test-rig was solved by identifying dedicated load cases which represent specific wind turbine behavior. This paper describes the development process of the project consisting of four phases. During two phases a scaled set-up was used, which enabled iterative optimization of the complex interaction between the mechanical dynamics and the electrical controller of the test-rig. In the final part of the paper the two previously discussed approaches are combined, as it discusses results from the validation of simulation models using measurements performed on the 13.2 MW test-rig.     

电力电子是风力发电的主要技术

本文回顾风力发电市场，叙述了和传统的电力发电相比，在以后的几年中风能将成为更具竞争力的能源之一。还介绍了固定速度和调整风力发电机以及拓扑结构、不同风力发电系统的比较及控制方案，最后指出风力发电机技术的未来发展趋势是进一步提高功率等级和电力电子技术。     

现代大功率变频器拓扑结构最新进展分析

随着大功率自关断器件和高速微控制芯片的不断发展,大功率电力电子装置的应用越来越广泛,传统的多重化结构由于受到变压器或电抗器尺寸、效率、价格及可靠性的限制,在功率等级提升的问题上遇到了极大的困难。多电平变流器的出现为解决这一问题提供了机会。在大功率电力电子装置中的另一个重要的问题就是大功率器件的工作频率较低,难以应用PW...     

风电机组低压穿越中的电力电子技术(下)

为了降低大规模风电并网对电力系统的影响,世界各国的电网运营商相继制定新的并网准则对并网风电场的输出特性作出严格规定,并网导则中的一项重要内容是要求风电场具有低压穿越(LVRT)能力。电力电子技术是提高风电场低电压穿越能力的重要手段,对于变速风电机组,电力电子设备已成为其标准配置,在低电压穿越过程中起到至关重要的作用;对于定速风电机组,电力电子设备是使其满足并网导则的必要部件。本文以我国并网导则为例,介绍LVRT导则对风电机组输出特性的相关要求:分析电网电压跌落对不同类型风电机组的影响;在此基础上,针对不同类型的风电机组,介绍提高其LVRT能力的电力电子技术,并对LVRT技术中当前存在的问题和未来的发展方向进行了讨论。     

风电场随机时间序列法功率预测的探究

我国能源资源总量相对较少,人均占有率低;能源消费增长较快,能源形势比较严峻;能源结构不合理,可再生能源开发利用不充分。从技术成熟性和经济可行性看,风电在可再生能源中具有最好前景。近十几年来其发电成本已得到大幅下降,风电己具有与传统常规电源发电竞争的潜力。随着我国能源结构的调整,无污染可再生的风电日益得到重视。风电场功率预测一直是风电研究热点和技术必需。