Multi-objective control of large scale floating offshore wind turbines using structural-hydrodynamic compensators and estimators

Wind turbine energy production is an exciting field that is rapidly growing. This rapid growth opened the doors to designing more complex turbine structures. Controlling such complex structures is challenging. Not only that, but the harsh environment the wind turbine is subject to adds more to the challenge. Wind turbines are now being deployed offshore for the potential of more power production. Floating Wind Turbines (FWTs) suffer the most environmental and structural challenges compared to onshore and fixed foundation offshore turbines. As an FWT is not fixed to the ground, excessive platform motion can lead to instability if not addressed in the control design.

This work investigates robust and optimal control methods on onshore and FWTs. The developed controllers’ main objective is to reduce power fluctuation and floating platform motion by accounting for important characteristics in the control design models. Such characteristics are low frequency modes (blade motion and filters) in the case of onshore wind turbines, and floating platform Degrees-OfFreedom (DOFs) and hydrodynamic state estimates in the case of FWTs.

The work tests the designed controllers on simulation models of 5MW, 10MW, and the 15MW FWT. Controller testing was via turbulent wind and irregular wave disturbances, i.e., realistic conditions. The results presented in this Thesis were compared with previous work in the literature and showed enhanced performance for power production and platform motion reduction. Findings discussed in this Thesis were published in two Elsevier Renewable Energy journal papers.