Innovative methods for wind turbine power curve upgrade assessment

Wind turbine power curve upgrades have recently been attracting considerable investment in the operation of wind farms and noticeable attention in the wind energy literature. Due to the non-stationary conditions to which wind turbines are subjected, the most consistent strategy for quantifying the production improvement from the installation of an upgrade is comparing, after at least some months of operation, the post-upgrade production against a model of the pre-upgrade production under the same conditions. Formulating adequate models for the power of the upgraded wind turbines is in general non-trivial and it can be difficult to achieve the precision that wind turbine practitioners typically require for the production assessment. In the present work, a multivariate linear method for selecting the most appropriate input for modeling a given output is presented and applied to a test case. The test case is a multi-megawatt wind turbine owned by Renvico, on whose blades vortex generators and passive flow control devices have been installed. Applying the proposed method, it is possible to compute with precision the production improvement in the first five months of post-upgrade operation (purely aerodynamic upgrade) and in the subsequent three months (aerodynamic and control upgrade). It is therefore possible to appreciate the different contributions to the production enhancement from the aerodynamic and control improvement. A non-upgraded wind turbine from the same wind farm is also studied and the precision of the results inspires the use of the proposed method for performance control and monitoring in general.