Experiences with object-oriented and equation based modeling of a floating support structure for wind turbines in Modelica

A floating substructure for wind turbines is modeled using the object-oriented modeling language Modelica in a coupled simulation environment. The equation-based modeling facilitates the implementation for engineers due to declarative model descriptions and acausal formulations. Predefined components from the Modelica Standard Library are used to represent several parts of a wind turbine. Especially the MultiBody library combined with the graphical editing feature is a powerful method to model the rigid body motions of a floating structure as shown herein. This paper illustrates how the resulting nonlinear differential-algebraic equation system can be implemented and solved in a convenient way. Different solvers can be easily tested to detect the solver with the best performance, without changing the code of the model. The developed model of the floating substructure has been verified with results of the Offshore Code Comparison Collaboration (OC3)-project and the results show good agreement.