Impact of Canonical Perturbations in the Inflow on Wind Turbine Loads

Abstract

The turbulent velocity field in the atmospheric boundary layer creates inflow fluctuations at a wide range of spatial and temporal scales that must be considered for resilient turbine design. This study is focused on separately characterizing the wind turbine’s response to canonical spatial or temporal oscillations in the inflow with only one wavelength or frequency. Temporal fluctuations in the inflow produce a response that is up to an order of magnitude greater than that of purely spatial fluctuations. The response to spatial oscillations in the inflow is also highly dependent on the alignment of the spatial waveform in the inflow to the rotor hub (i.e. phase angle). Different phase angles produced up to a factor of 30 difference in load variations. The integrated wind turbine loads show the largest response to spatial oscillations at wavelengths around 100-140m which is approximately four times the response at the chord scales. Structural deformations largely dampen the response to spatial oscillations in the inflow while increasing the response to temporal fluctuations near the blade rotation frequency. The wind turbine control system also amplifies the load response to temporal oscillations near the blade rotation frequency.