Mixed H2/H∞ control design for wind turbine system with pole placement constraints

This paper deals with the problem of mixed H2/H∞ control for an offshore floating wind turbine system. Firstly, we consider the modeling of a wind turbine system with collective pitch control scheme and the interaction with drive train dynamics and tower motions. The scenario is for the above rated wind speed conditions, where the goal is to keep the rotor rotational speed at its rated value while mitigating oscillations in the drive train and tower. Secondly, we present an effective technique to design a dynamic output-feedback mixed H2/H∞ controller with pole placement constraints using a linear matrix inequality (LMI) approach. Pole placement constraints are implemented in order to improve the closed loop system response. Finally, a model obtained from the wind turbine simulation software FAST is used to illustrate the effectiveness of the proposed design technique.