Effect of nonlinear hydrostatic stiffness on response of floating wind turbine

Abstract

The booming demand for wind energy has pushed the offshore wind turbine into much deeper water. At water depth greater than 60 m the floating wind turbines are considered to be the most economical and feasible alternative to that of the fixed supported offshore wind turbines. The stability of floating platform is one of the major challenges and is primarily achieved through mooring lines and hydrostatic buoyancy of the platform. Based on the assumption of the small displacement of the platform, in most of the studies, the hydrostatic stiffness is considered to vary linearly with the platform position. The present study is focused on the effect of nonlinear hydrostatic stiffness on the response of floating wind turbine. The floating wind turbine is modeled as a multi-body system and the equation of motion is obtained from the principle of conservation of momentum. The effect of hydrostatic nonlinearity is demonstrated through the analysis of OC3-Hywind floating wind turbine model. In the case of small motion, the response for the linear and nonlinear cases is identical. However, for large displacement, the effect of hydrostatic nonlinearity was found to be more pronounced.