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在高海拔地区,空气密度降低使风的能量密度降低。为了捕捉尽可能多的风能,一个方法是增大风轮的扫风面积,即增加叶片的长度;另一个方法则是对风力机的控制,尤其是对风及桨距角的变化进行调整。风力机叶片在设计时桨距角为0°,即在设计点,其功率系数C_P为最佳值。而在非设计点,0°桨距角下的CP则并非最佳值。本文针对传统变速变桨控制的水平风力机的桨距角进行优化,在额定风速前的每个风速下保证其C_P都是最佳值,以提高整体发电量。选取某款1.5 MW 42 m叶片进行对比计算,得到最优桨距角变化曲线,并用拟合得到桨距角变化曲线。并分别取3000 m和4000 m海拔高度处空气密度进行优化前后功率曲线及理论年发电量(AEP)的计算,结果显示,在额定前的CP提高最多,且海拔越高,空气密度越低,桨距角优化的效果越明显。本文仅考虑了气动方面效率的提高,该桨距角控制方式对于风机叶片极限载荷和疲劳载荷的影响还需要进一步探索。
At high altitudes, the reduction in air density reduces the energy density of the wind. One way to capture as much wind energy as possible is to increase the swept area of the wind wheel, ie to increase the length of the blade. Another approach is to control the wind turbine, especially the wind and pitch angle. Wind turbine blades in the design pitch angle of 0 °, that is, at the design point, the power coefficient C_P is the best value. At non-design points, the CP at 0 ° pitch is not optimal. In this paper, the pitch angle of a horizontal wind turbine with conventional variable pitch control is optimized, and its C_P is guaranteed to be the best value for every wind speed before the rated wind speed to improve the overall power generation. Select a section of 1.5 MW 42 m blade for comparison and calculation, the optimal pitch angle curve was obtained and the pitch curve was obtained by fitting. The air density before and after optimization at 3000m and 4000m respectively was used to calculate the power curve and the theoretical annual power generation (AEP). The results showed that CP increased most before rated, and the higher the altitude, the lower the air density, The effect of pitch angle optimization is more obvious. In this paper, only the aerodynamic efficiency is considered. The effect of the pitch angle control method on the ultimate load and fatigue load of the fan blades needs to be further explored.