Control strategies for multi-rotor wind turbines

Abstract

This work considers steady-state aspects of multi-rotor wind turbine control. In contrast to most literature on the topic, the underlying multi-rotor model includes the aerodynamic interactions between rotors. The model predicts that these interactions are central for effective control of multi-rotor wind turbines under some conditions. A numerical optimization problem is formulated to find the optimal control solutions, and two adaptations of the maximum power point tracking (MPPT) algorithm for the multi-rotor case are suggested. By employing furling for multi-rotor wind turbines, it is also shown that one can drastically reduce the bending moment of the structure. Other physical effects, such as operation with wind shear and simple failure handling, are also presented using a 23-rotor fixed-pitch multi-rotor wind turbine with a total rated power of 5MW. The results are meant to be an enabling work, showcasing the possibilities and challenges involved in multi-rotor stability analysis and control problems.