Response sensitivity of wind turbines to atmospheric turbulence

Abstract

The dynamic response of wind turbines to atmospheric turbulence is examined. The modeling handles both the wind inputs and the resulting loads using the analysis techniques of random vibration theory and spectral analysis. Presented are typical response results for a small, 8kW wind turbine and a large, 2.5 MW turbine. The turbine system mechanical model employs 5 degrees-of-freedom to represent the lower frequency motions of the system. The rotor is assumed to be rigid and is three bladed for simplicity. The aerodynamic forces are modeled using a simple quasi-static strip theory. The emphasis is placed on this model to identify the key turbulence inputs which are important in wind turbine design. On the basis of results computed for the two turbines modeled, it is determined that the most important turbulence inputs are the longitudinal fluctuations in the direction of the mean wind which act uniformly across the rotor disk (engulfs the rotor disk), and the across the disk gradients of the longitudinal wind fluctuations. Although each of these invokes a different machine response, they are judged to be of equal importance, because they each contribute significantly to the vibration energy of the lower system frequencies. The report presents numerous spectralmore » density plots for the various turbine system responses, and discusses the results in some detail. « less

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