Effect of Coherence Function on Rotational Fourier Spectrum of Wind Turbine

In order to consider the rotational effect of rotor and determine the exact loads of wind turbine generator system, rotational Fourier spectrum was deduced, and the physical nature of the rotational Fourier spectrum was indicated. Importance of coherence function to the rotational Fourier spectrum was analyzed according to physical nature, as well as the parameter sensitivity analysis of decay factor. The result shows that there is a sharp dip of rotational Fourier spectrum at the integer multiple rotational frequencies with Davenport exponential coherence function while it's eliminated with coherence function supplied by IEC international standard. The rotational Fourier spectrum energy removes to the high frequency bands, the amplitudes of peak at the integer multiple rotational frequencies are increased with decay factor increased, which results in rotational effect more obvious.