An FMI-based co-simulation framework for simulations of wave energy converter systems

A wave energy converter (WEC) comprises many components with distinct functions. The whole WEC system is complicated, as each component is also a complex subsystem. It is challenging to properly model and couple these subsystems to achieve a global simulation of the whole system. This study proposes an FMI-based co-simulation framework to tackle this challenge. Through the use of a co-simulation technique requiring minimal programming effort, a suite of numerical solvers serving for modelling various WEC components is coupled to create a comprehensive system model for a single WEC unit. The modules of the Ansys software, Aqwa and Rigid Dynamics, are employed to model hydrodynamic loads and motion responses. Simulink is utilized to model the power take-off (PTO) system and then integrate all models into a global simulation. The capability and accuracy of the FMI-based co-simulation framework are validated against an experimental heave decay test and verified by cross-comparing a numerical model built in SESAM. Furthermore, the framework is expanded to encompass the modelling of a large-scale wave park that includes multiple WEC units. Based on a novel WEC concept called NoviOcean, two study cases of a single unit and an 18-unit wave park are investigated. Buoy motions and power performance under several regular and irregular sea states are analysed. The hydrodynamic interactions between the units are evaluated quantitatively regarding the power performance. It is found that the interactions improve the power performance, with a maximum increase of up to 36%.