Turbulence and Shear Normalisation of Wind Turbine Power Curve

Measured wind turbine power curves are significantly influenced by the turbulence intensity. A large part of this effect is due to the averaging of the power curve measurement data over 10-minute periods. This makes a comparison of measured power curves with guaranteed power curves difficult. In addition, the effect limits the applicability of guaranteed power curves for wind resource assessments, as the site specific turbulence intensity may differ from the reference turbulence intensity of the guaranteed power curve. An easy to handle approach for the normalisation of wind turbine power curve data to a reference turbulence intensity has been developed and suggested to the maintenance team of the standard IEC 61400-12-1 [1] for the inclusion in the next revision of the standard [2]. The model allows also adjusting a power curve given for a reference turbulence intensity to a site specific turbulence intensity, e.g. for the purpose of wind resource assessments. The method can further be applied for: ● check of plausibility of power curves ● evaluation of potential for optimisation of wind turbine power performance ● estimation of effect of limitation of power output, e.g. due to noise reduced operation or grid curtailment ● estimation of effect of an increase of rated power Apart of the turbulence intensity, also the wind shear has a significant influence on wind turbine power curves. Thus, also a simple approach for normalising power curves to a reference wind shear has been developed and suggested for the improvement of the standard IEC 61400-12-1.