LQG control of a 10 MW mass-optimized floating wind turbine

Designing effective control strategies for floating offshore wind turbines (FOWTs) requires holistic consideration of aerodynamics, structural dynamics, and platform design and performance. As floating systems increase in size and complexity, optimization plays a key role in the design and operation of these systems. In this paper, we demonstrate the role of optimization in the design and operation of a floating wind turbine through the design of a reference floating platform for the IEA 10 MW reference wind turbine and an accompanying optimal controller. First, a concrete semi-submersible floating platform for the IEA 10 MW reference turbine is designed via a previously presented optimization tool, meeting key performance criteria while satisfying structural requirements and minimizing structural mass. The system was then simulated in OpenFAST with a state-of-the-art gain-scheduled PI controller from the literature. To further enhance the system performance, a Linear Quadratic Gaussian (LQG) regulator was designed and implemented in OpenFAST. Two different tunings of the LQG controller were investigated to demonstrate how optimization can improve global system performance. The results showed that the optimal controller greatly improved power regulation with minimal to no impact on platform dynamics. Furthermore, it was shown that for a collective pitch control system, limited platform motion regulation can be achieved in extreme conditions at the expense of power regulation.