风切变和塔影效应对风力机变桨距控制的影响分析

The analysis of the pitch control of wind turbine by the influences of wind shear and tower shadow

随着单台风力机功率的不断增大,变桨距控制对于风力机起动、制动性能的改善和对输出功率的稳定作用不断显现。单台风力机功率的不断增大也导致了塔架的增高和风轮直径的增大,风切变和塔影效应对风轮旋转平面风速分布产生的差异也不断变大。为了验证风速差异对变桨距控制的影响,建立了考虑风切变、塔影效应的风速模型以及基于叶素理论的风力机模型。采用1.5 MW风力机的数据进行研究,仿真验证表明,在集中变桨时,即使参考风速稳定,风速分布的差异也会使实际的风轮输出转矩产生脉动,桨距角产生周期性脉动,从而导致输出功率产生脉动,影响电能质量,同时叶片上产生不平衡的弯矩,增加了叶片的疲劳载荷,缩短了叶片的寿命。大型风力机应采用独立变桨技术来解决这些问题。

With the power of a single wind turbine increasing, the effect of the pitch control for the improvement of the wind turbine starting/braking performance and stabilizing the output power are continuously showed. It also causes the higher wind tower and the longer diameter of the wind wheel. The difference of the wind speed distribution is bigger. This paper build the model of wind based on wind shear and tower shadow and the model of the wind wheel based on blade element theory. It proves the pulsation of the output power, the torque, the speed and also the pitch angle caused by wind shear and tower shadow. The pulsation also causes the unbalanced load on the blade which reduced the life of the blade. So the individual pitch control is necessary for the large wind turbines to reduce above-mentioned problems.