A simplified model for the dynamic analysis and power generation of a floating offshore wind turbine

Introduction Floating offshore wind turbines are a promising solution that has been under development in recent years. With lower constraints to water depths and soil conditions, floating substructures enable to harness the... [ view full abstract ]

Introduction

Floating offshore wind turbines are a promising solution that has been under development in recent years. With lower constraints to water depths and soil conditions, floating substructures enable to harness the abundant wind resources of deep waters and thus allow countries that lack shallow waters to develop offshore wind power. The objective of this paper is to develop a numerical model that allows capturing the main motions and response of a floating offshore wind turbine to wind and wave loads.

Methods

The floating wind turbine modeled in this study is the OC3-Hywind concept, which was chosen for the availability of data, the geometric simplicity and the relevance of the concept on the market. The model is developed using MATLAB and is tested for stability, natural frequencies and response to different external loads. The equation of motion is solved and a rigid body approach was used to model the system. The hydrodynamic forces are computed by using the Morison equation. A number of different load cases are used to test and validate the developed model. The specific behavior of the floating wind turbine is considered in the computation of the power output by reducing the inflow wind velocity by the platform pitch angle. The power performance of the floating offshore wind turbine is analyzed and compared to a bottom-fixed offshore wind turbine.

Results and Discussion

The objective was to develop a simplified model for a floating offshore wind turbine and to obtain the response of the dynamic behavior of this system. The model was built using MATLAB and the response of the system was evaluated and compared with results obtained by FAST in the OC3 project. It has been shown that the main motions and system's dynamics are captured by the simpler model with a comparable accuracy. Furthermore, the power production of the floating offshore wind turbine was computed and the performance discussed.