Smooth transition between controllers for floating wind turbines

Abstract

This paper presents a novel wind turbine control system which gives a smooth power output during transitions between different controllers. The paper presents an implementation of a control system designed for an offshore floating wind turbine using a linear Model Predictive Control approach. The performance is investigated in computer simulations, with emphasis on stability in the tower fore-aft motion and behaviour during transition between controllers. The results clearly demonstrate that the wind turbine using the proposed algorithm for smooth transition indeed exhibits a smooth system behaviour. In comparison to a case with sudden transition, the behaviour is found to be significantly improved. Moreover, tower oscillations are found to be stable, by virtue of the controller prediction horizon exceeding the natural periodicity of the tower oscillations. Smooth system behaviour is important to increase the lifetime of critical parts of the turbine. With increasing turbine sizes such considerations are of increasing importance, making the results obtained in this paper of particular relevance for large wind turbines, both onshore and offshore. © 2012 Published by Elsevier Ltd.