Towards standards in the analysis of wind turbines operating in cold climate – Part A: Power curve modeling and rotor icing detection

Abstract

Analyzing the performance of wind turbines operating in cold climate conditions is a complex matter. The lack of any widely used standards adds to the challenge of comparing turbine performance between and within a wind farm. It proves to be an even bigger issue when alternative operational strategies, including ice protection systems (IPS) are implemented and their performance has to be assessed. Before making any comparison between turbines, it is important to build robust power curve models that are not influenced by secondary factors (e.g. temperature and wind orientation). An accurate power curve model allows to detect more precisely any ice formed on the rotor. This paper details a process that allows to build a simple power curve model while minimizing the influence of temperature and wind direction. The piecewise function used to represent the power curve yields a precise parametric representation while being more robust to outliers. Different tools being used to evaluate the performance of the model are presented. With these tools it was possible to observe that standard air density corrections were not able to completely compensate the effect of temperature on the power output. The analysis also provides comprehensive definitions of the different periods composing an icing event. A simple and efficient ice detection threshold using only the power curve is proposed and validated. Using this threshold, algorithms defining significant production loss periods and icing events are presented. The different tools introduced in this paper can decrease significantly the uncertainty in the available power estimation, which proves to be crucial when comparing the performance of multiple turbines.