Simulation of Thunderstorm Downbursts and Associated Wind Turbine Loads

This study is focused on simulation of thunderstorm downbursts and associated wind turbine loads. We first present a thunderstorm downburst model, in which the wind field is assumed to result from the summation of an analytical mean field and stochastic turbulence. The structure and evolution of the downburst wind field based on the analytical model are discussed. Loads are generated using stochastic simulation of the aeroelastic response for a model of a utility-scale 5-MW turbine. With the help of a few assumptions, particularly regarding control strategies, we address the chief influences of wind velocity fields associated with downbursts—namely, large wind speeds and large, rapid wind direction changes—by considering different storm scenarios and studying associated turbine loads. These scenarios include, first, an illustrative case to understand details related to the turbine response simulation; this is followed by a study involving a different storm touchdown location relative to the turbine as well as a critical case where a shutdown sequence is included. Results show that the availability of and assumptions in wind turbine control systems during a downburst clearly influence overall system response. Control system choices can significantly mitigate turbine loads during downbursts. Results also show that different storm touchdown locations result in distinct characteristics in inflow wind fields and, hence, in contrasting turbine response.