变频变压器在风电并网过程中的频率调整研究

变频变压器(variable frequency transformer,VFT)是一种串联型的灵活交流输电系统设备,也是一种新型智能电网设备.在过去几十年里,我国风力发电是增长最快的新兴可再生能源,但是对于风电并网时的电力系统频率稳定问题也引起了广泛的关注.本文介绍了VFT调节频率的基本原理和转子转速控制设计,并在PSCAD/EMDTC中构建了VFT与风电场的仿真互联模型,进行了对风电并网的仿真实验,着重分析了VFT稳定频率和调节频率的作用.结果表明VFT可以在风电并网中显著提高系统的暂态稳定水平,从而提高风电场的发电能力.     

Special report on relationship between wind farms and power grids

The installed capacity of a.large scale wind power plant will be up to a number of hundreds MW, and the wind power is transmitted to load centers through long distance transmission lines with 220 kV, 500 kV, or 750 kV. Therefore, it is necessary not only considering the power transmission line between a wind power plant and the first con- nection node of the power network, but also the power network among the group of those wind power plants in a wind power base, the integration network from the base to the existed grids, as well as the distribution and consumption of the wind power generation by loads. Meanwhile, the impact of wind power stochastic fluctuation on power systems must be studied. In recent years, wind power prediction technology has been studied by the utilities and wind power plants. As a matter of fact, some European countries have used this prediction technology as a tool in national power dispatch centers and wind power companies.     

大型风电场风机最优布置规律研究

采用较完善的风机优化布置计算数学模型,研究了单一风向风况下的风电场风机最优布置的一般性规律,给出了风机布置排数和风机间距的合理取值范围:风电场区域无限制以及风电场沿盛行风向上尺寸较小时,风机横向间距应为2D0～3D0(D0为风轮直径),纵向间距应大于15D0;风电场沿盛行风向上尺寸较大时,可考虑布置3排以上风机,风机纵向间距应为15D0～20D0,风机横向间距应为3D0～5D0;风机优化布置一般可不考虑风速大小的影响.在此基础上,研究了均匀对称风况、1个主导风向风况和多个主导风向风况下的风机最优布置规律,得出了风机最优布置形式与风况特征的规律性基本一致,且风况越复杂,风机最优布置的规律性越弱的结论.     

基于粗糙集和RBF神经网络的风电场短期风速预测模型

结合粗糙集提出了一种RBF神经网络短期风速预测模型。采用粗糙集对预测模型的输入特征空间进行约简,找出对未来预测的风速具有主要影响的因素,以此作为RBF神经网络预测模型的输入变量;在RBF神经网络训练的过程中,采用在线滚动优化策略,将最新的样本加入训练集,从而使预测模型能够跟踪风速的最新变化。将提出的方法用于某风电场的1 h短期风速预测,仿真实验结果表明该方法具有结构简单、预测精度高的优点。     

利用微藻热解成烃制备可再生生物能源进展

微藻热解产物是非常好的可再生生物能源，具有化石能源所不具有的优点：这种能源无污染，可不断再生；微藻生长繁殖迅速，短期内即可获得大量微藻进行热解，进而得到所需要的产物；微藻热解简单行，不需要复杂的仪器设备，因此，利用微藻热解产生可再生生物能源的技术倍受世界各国能源专家的关注，认为该技术是解决目前能源紧张的非常有效的方法。     

基于小波分析法与滚动式时间序列法的风电场风速短期预测优化算法

为实现风电场风速的超前多步高精度预测,提出一种基于小波分析法与滚动式时间序列法混合建模的优化算法。该优化算法引入小波分析法对风电场实测非平稳风速序列进行分解重构计算,将非平稳性原始风速序列转化为多层较平稳分解风速序列,利用对传统时间序列分析法改进后的滚动式时间序列法对各分解层风速序列建立非平稳时序预测模型,并通过模型方程实现超前多步滚动式预测计算。仿真结果表明:该优化算法实现了风速的高精度短期多步预测,将传统时间序列分析法对应超前1步、3步、5步的预测精度分别提高了54.22%,26.44%和19.38%,其预测的平均相对误差分别为1.14%,3.06%和4.41%;优化算法具有较强的细分与自学习能力。     

Perspectives of China’s Wind Energy Development

Wind energy is a kind of clean renewable energy, which is also relatively mature in technology, with largescale development conditions and prospect for the commercialization. The development of wind energy is a systematic project, involving policy, law, technology, economy, society, environment, education and other aspects. The relationship among all the aspects should be well treated and coordinated. This paper has discussed the following relationships which should be well coordinated： relationship between wind resources and wind energy development, relationship between the wind turbine generator system and the components, relationship between wind energy technology and wind energy industry, relationship between off-grid wind power and grid-connected wind power, relationship between wind farm and the power grid, relationship between onshore wind power and offshore wind power, relationship between wind energy and other energies, relationship between technology introduction and self-innovation, relationship among foreign-funded, joint ventured and domestic-funded enterprises and relationship between the government guidance and the market regulation, as well as giving out some suggestions.     

A new method for constructing total energy conservation algorithms

Based on a basic rule for the research on numerical methods which requires that the properties of the original problem should be preserved as much as possible under discretization, a new method for constructing total energy conservation algorithms is presented. By this method, all kinds of implicit schemes with energy conservation laws including many classical conservation schemes can be constructed from a kind of special function. Also, the concrete criterion for judging total energy conservation schemes is given. Numerical tests show that these new schemes are effective.     

基于波数能量谱的海面风向反演算法

为提高应用X波段导航雷达反演海面风向的适用性和精度,针对现有局部梯度法反演海面风向存在无法自动寻找到合适的缩减图像分辨率,导致风向反演结果不稳定的问题,提出基于波数能量谱的海面风向反演算法.首先,应用风场成像特征,将包含风条纹的海面静态特征提取出来;其次,应用二维离散傅里叶变换获得海面静态特征的能量谱;最后,利用风条纹尺度特性,构建波数能量谱带通滤波器,将风条纹能量谱提取出来,从而得到海面风向.通过实验将本文算法、局部梯度法与风向标实测数据比较分析,表明本文算法反演适用性达到99%,反演精度提高了58.97%.     

Assessment of wind energy potential in China

China wind atlas was made by numerical simulation and the wind energy potential in China was calculated. The model system for wind energy resource assessment was set up based on Canadian Wind Energy Simulating Toolkit （WEST） and the simulating method was as follows. First, the weather classes were obtained depend on meteorological data of 30 years. Then, driven by the initial meteorological field produced by each weather class, the meso-scale model ran for the distribution of wind energy resources according each weather class condition one by one. Finally, averaging all the modeling output weighted by the occurrence frequency of each weather class, the annual mean distribution of wind energy resources was worked out. Compared the simulated wind energy potential with other results from several activities and studies for wind energy resource assessment, it is found that the simulated wind energy potential in mainland of China is 3 times that from the second and the third investigations for wind energy resources by CMA, and is similar to the wind energy potential obtained by NREL in Solar and Wind Energy Resource Assessment （SWERA） project. The simulated offshore wind energy potential of China seems smaller than the true value. According to the simulated results of CMA and considering lots of limited factors to wind energy development, the final conclusion can be obtained that the wind energy availability in China is 700 - 1 200 GW, in which 600 - 1 000 GW is in mainland and 100 - 200 GW is on offshore, and wind power will become the important part of energy composition in future.     

双臂机器人避关节极限与避奇异位形优化研究

关节极限及机械手臂的奇异位形的限制,往往导致协调任务失败。通过对冗余双臂机器人的研究,利用冗余手臂的自运动特性并基于梯度投影法及奇异鲁棒性求逆法完成了冗余手臂的避关节极限及避奇异位形的优化。经过优化后获得了最优的关节位形,同时对双臂末端轨迹的误差进行了分析和控制,有效的降低了末端轨迹跟踪误差,使机械手臂的运动性能得到了明显的改善。最后通过仿真验证对比优化前后的结果可知此优化方法的可行性。为冗余双臂机器人协调控制方法的研究提供了条件。     

储能技术在风电并网中的应用研究进展

简要介绍了储能技术的分类与应用范围,指出了大规模风电并网面临的主要问题.针对风电并网带来的系统稳定性、风电机组的低电压穿越、风电穿透功率、电能质量及系统运行经济性等方面的问题,详细阐述了基于储能技术的解决方案,并分析了各方案的优缺点.基于已有的研究成果,结合储能技术的特点,提出了储能技术在风电并网中应用的原则意见.     

扩压式旋风风能系统的数值模拟

扩压式旋风风能系统是一种利用强涡旋流场、类似于旋风分离器的新型风能利用装置，它的进出口都是开路条件，流场比后者更复杂，更难计算．本文直接从 Ｎ－Ｓ方程出发，采用压力－速度修正方法和非均匀交错网格差分格式，模拟３整个旋风塔的强涡流场，结果满意。弄清了系统的流场机制。给出了正确描述这种流场的数字模型和程序软件。这些工作对类似的流场问题（轴对称及强涡旋流动）的研究都有意义。     

低风速风力发电机组造价与度电成本分析

为了提高低风速条件下风力发电机组的经济效益,提出了一种通过合理设计叶片来降低机组度电成本的方法。以相同功率等级、不同叶片长度的3种风力发电机组作为研究对象,在不同风力条件下分别计算各机组的年发电量,利用经验公式对各机组的总成本进行估计。结果表明:机组的度电成本随着平均风速的升高而降低。在平均风速较高的地区,长叶片机组在度电成本上的优势并不明显。而在平均风速较低的地区,机组的年发电量随着叶片的加长而明显增加;尽管总成本有所升高,但度电成本依然得以降低。通过适当减小叶片的最佳叶尖速比、增大风能利用系数也可以降低度电成本。该文还论述了通过合理选择叶片长度、优化翼型以及应用新材料来提高机组经济效益的可行性。     

泥煤对镥的吸附特征

静态条件下泥煤对溶液中Lu3+的吸附率较高,而且吸附速度较快,镥与泥煤能迅速发生表面络合反应达到平衡.pH值和离子强度对低浓度镥吸附动力学影响不大.5个经典动力学方程中Elovich方程能较优地描述泥煤吸附Lu3+的过程.泥煤吸附镥属于放热反应,且吸附过程自发不可逆,吸附焓变、熵变、自由能变均为负值.Freundlich吸附等温方程中的n值大于1,说明镥在泥煤上的吸附以单配位为主,且该吸附容易进行.颗粒泥煤的表面分形维数为2.837 5.     

基于能量偿还时间的小型风力发电机预安装评估

为了避免小型风力发电机安装方案不当所造成的资源浪费,提出了一种从评估到优化的预安装评估方法。首先分别运用静态、动态生命周期评价方法获得风机生命周期输入总能量。其次利用实验数据与概率论法计算出年发电量。然后根据定义公式得出能量偿还时间,对比使用寿命数据,评估风机绿色效益。最后根据评估结果,针对部分影响因素实施改善分析,以改善风机绿色效益。结果表明：动态生命周期评价方法的绿色效益评估结果更准确,且计算得出的偿还时间有所减少;改善策略能够有效提升风机绿色效益,进而提升评估结果。该方法中的评估模式和部分计算方法可在其他新能源发电产品的评估中推广。