风力提水机可变行程之实现途径

描述了可变行程风力提水机与普通风力提水机相比的优点,探讨了可变行程的具体实现及控制方法,指出了可变行程风力提水存在的一些问题及今后的改进方向。     

风力提水机变行程的电液控制

在分析传统的变行程风力提水机控制系统的基础上，提出了一种基于LabVIWE的电液方式控制变行程的方案，并进行了软、硬件设计，对于该类电液控制系统的设计具有一定的参考价值。     

风力提水机性能的改进

在同样叶轮直径,同样运行条件下可对变行程与不变行程风力提水机进行了对比实验,实验结果表明,在低风速度下,可变行程风力提水机的性能与不变行风力提水机相比差别不大;但在高风速下,可变行程风力提水机具有提水量大,效率高,泵运行转速稳定等优点,极具开发利用价值。     

变行程风力提水技术

研究了以变行程技术实现机械式风力提水机风轮与活塞泵在宽风速范围的高效匹配问题.文章对变行程风力提水技术的基本原理进行了分析;提出了风轮与活塞泵最佳匹配时行程随风速变化的关系式;研究了变行程提水机组的工作特性;采用瑞利分布对机组投运后的出力进行了预测.研究结果表明,变行程技术对改善风力提水机组的工作特性有明显效果.     

The starting behaviour of a small horizontal-axis wind turbine

This paper presents selected results taken from an extensive investigation of the starting performance of a small horizontal-axis wind turbine. Starting was observed for blade pitch angles varying between 0 and 35° in 5° increments. At 0°, the angle for maximum power, the turbine’s 5 m diameter blades produce 5 kW at a wind speed of 10 m/s. At this pitch, starting is characterised by a long “idling period” in which the blade’s angular velocity increased only slowly because of the very high angles of attack. As the pitch angle increased, the idling period decreased. At all pitch angles, the measurements of angular velocity are compared with those obtained from a numerical integration of the equation for angular acceleration. The aerodynamic torque was obtained from a quasi-steady blade element analysis and the resistive torque of the drive train and generator was subtracted to determine the net torque accelerating the blades. The agreement between predicted and measured angular velocity was generally good and improved as the pitch angle increased.     

Estimating daily wind speed under climate change

A semi-empirical downscaling approach is presented to estimate spatial and temporal statistical properties of local daily mean wind speed under global climate change. The present semi-empirical downscaling method consists of two elements. Since general circulation models (GCMs) are able to reproduce the features of the present atmospheric general circulation quite correctly, the first element represents the large-scale circulation of the atmosphere. The second element is a link between local wind speed and large-scale circulation pattern (CP). The linkage is expressed by a stochastic model conditioned on CP types. Parameters of the linkage model are estimated using observed data series; then this model is utilized with GCM-generated CP type data corresponding to a 2 × CO₂ scenario. Under the climate of Nebraska the lognormal distribution is the best two-parameter distribution to describe daily mean wind speed. The space-time variability of wind speed is described by a transformed multivariate autoregressive (AR) process, and the linkage between local wind and large-scale circulation is expressed as a conditional AR process, i.e. the autoregressive parameters depend on the actual daily CP type. The basic tendency of change under 2 × CO₂ climate is a considerable increase of wind speed from the beginning of summer to the end of winter and a somewhat smaller wind decrease in spring.     

Observations of the starting behaviour of a small horizontalaxis wind turbine

This paper describes observations of the starting performance of a small horizontal-axis wind turbine in the context of a simple, quasi-steady analysis of the complex aerodynamics dominated by unsteadiness, high angles of attack, and low Reynolds number. Soon after they begin rotating, the blades can generate unexpectedly high torque. At the same time, the nondimensional pitch rate and reduced frequency are too small to suggest a significant increase of the torque through the effects of unsteadiness. The torque then decreases due to inappropriate blade angles of attack. This leads to a substantial “idle time” at both high and low wind speed, in which the rotating blades are accelerating only slowly and the angles of attack are slowly decreasing. When the angles are reduced to those giving high lift: drag ratios, the blades accelerate rapidly to complete the starting sequence by producing significant amounts of power. At low wind speeds, about 4 m/s, a gust is apparently required to complete the starting sequence.     

沿海滩涂风力提水节能效果初探

通过对盐城市沿海两县(市)风力资源的调查和整理,探讨了沿海滩涂利用风力提水的节能效果,提出了建议。     

FS-3.5型风力发电提水机

与传统的风力提水机械不同，FS-3．5型风力发电提水机是由风力发电机、控制器、直流潜水电泵3大部件组成的提水系统。介绍了FS-3．5型风力发电提水机结构特点、工作特性及性能指标，对其进行了技术经济分析，探讨了该机组的应用前景。     

水深与水面风力对湖水源热泵系统性能的影响

为了研究水深与水面风力对湖水源热泵系统性能的影响,建立了垂向一维湖泊水温模型。根据株洲的典型气象年逐时气象参数,对4,8,5.6 m水深时的全年垂向水温分布进行了逐时模拟。模拟结果表明,由于水面风力的混合作用,水体应达到一定的水深,才会出现温度分层现象。如果株洲的湖水深度不小于5.6 m,夏季可以从底层取到温度较低的水,热泵机组的制冷性能优于带冷却塔的冷水机组;而且,冬季取水温度在4℃以上,能够保证在冬季大部分时间内热泵系统的正常制热运行。文章得出的结论也适用于与株洲气候类似的地区。     

Electric power generation based on variable speed wind turbine under load disturbance

This study was interested in the management of an energy production unit. A variable speed wind turbine (VSWT) was used as a principal source and a supercapacitor (SC) module was used as an energy storage system. Both were connected through a direct current bus. This unit was supplying a three-phase load using an inverter and an inductor and capacitor filter. In order to regulate the direct current bus voltage, the SC storage state was controlled by using a buck-boost converter according to load instructions and wind speed fluctuations. Then, a resonant controller was established to avoid any disturbances and to control the alternating line-to-line voltages of the load which may be unbalanced. This study has shown that the stability of the three-phase voltage source depends on the direct current bus power management and also on the line-to-line voltage control. Simulation results are presented to validate the efficiency of the control strategies used.     

Dynamic wind turbine output power reduction under varying wind speed conditions due to inertia

The inertia of wind turbines causes a reduction in their output power due to their inability to operate at the turbine maximum co‐efficient of performance point under dynamic wind conditions. In this paper, this dynamic power reduction is studied analytically and using simulations, assuming that a steady‐state optimal torque control strategy is used. The concepts of the natural and actual turbine time‐constant are introduced, and typical values for these parameters are examined. It is shown that for the typical turbine co‐efficient of performance curve used, the average turbine speed can be assumed to be determined by the average wind speed. With this assumption, analytical expressions for the power reduction with infinite and then finite turbine inertia are determined for sine‐wave wind speed variations. The results are then generalized for arbitrary wind speed profiles. A numerical wind turbine system simulation model is used to validate the analytical results for step and sine‐wave wind speed variations. Finally, it is used with real wind speed data to compare with the analytical predictions. Copyright © 2012 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.     

考虑风速相关性的风电接入能力分析

同一地区的风电场一般建立在相互接近的地理位置上,因此其风速往往呈现出一定的相关性。采用Copula函数建立多风电场的风速相关性模型,继而生成具有相关性的风速分布样本空间。考虑风速的随机性与相关性,应用机会约束规划理论,在满足系统安全可靠运行的前提下,以系统可接入的风电机组装机容量最大化作为优化目标,建立了计算风电穿透功率极限的概率最优潮流模型,并采用一种基于随机模拟技术的粒子群优化算法进行求解。以IEEE30节点测试系统为算例,分析风速相关性、风电场接入点和机会约束置信水平对风电接入能力的影响,结果验证了所提模型与算法的合理性与可行性。