Closed-loop system identification of Alstom 3MW wind turbine

Abstract

Control algorithms for wind turbines are traditionally designed on the basis of (linearized) dynamic models. On the accuracy of such models depends hence the performance of the control, and validating the dynamic models is an essential requirement for achieving the optimum design. The aim of this work is to identify, at different wind speeds, the dynamic model of a wind turbine in operation. Experimental modal analysis (EMA) is the selected technique for system identification, and band-limited pseudo-random binary excitation signals (PRBS) are summed to the controlled inputs of the wind turbine system. The method is applied to the Alstom Eco100 3MW wind turbine. Fairly good match is found in frequency and damping ratio for a frequency range up to 1 Hz. The time domain validation indicates in all cases reasonable model quality. The frequency domain comparison carried out for selected wind speeds shows close overlap around the first tower fore-aft and side-to-side frequencies, even though some discrepancies are found at first drive train frequencies.