The OneWind Modelica Library for Floating Offshore Wind Turbine Simulations with Flexible Structures

Abstract

Floating offshore wind turbines are getting more and more into the focus of interest, as industries aim for larger turbines and deeper water areas. Fully coupled analyses of those highly complex systems are challenging. In this paper, the hierarchical programming structure in Modelica is used to model a fully flexible floating wind turbine system. The single components, as well as special difficulties that have to be dealt with during modeling, are addressed. On basis of a reference floating offshore wind turbine, the implemented fully flexible model is compared with its rigid equivalent, as well as results from code-to-code comparisons of free-decay simulations. The findings are satisfactory and confirm the theoretical assumptions. In addition, further applications of the created model are shown.

Development and Verification of an Aero-Hydro-Servo-Elastic Coupled Model of Dynamics for FOWT, Based on the MoWiT Library

“…Within the OC3 project, the floating spar-buoy wind turbine system from phase IV, as described in Section 2, was modeled by the project participants in different codes and tools for wind turbine system simulation, as introduced in Section 1, to be compared and verified within the study [7]. For the same purpose of code verification and to add one more result to the cross-code comparison, the OC3 FOWT is implemented in the modeling language Modelica, using the MoWiT library for fully-coupled aero-hydro-servo-elastic dynamic simulation of wind turbine systems, developed at Fraunhofer IWES [25][26][27]. In the following, first (Section 3.1), this library and the modeling environment is introduced briefly to point out the advantages and capabilities of this tool.…”

“…This structure also allows fast and easy exchange of single components to model different wind turbine technologies, turbine or support structure designs, control strategies, or site and environmental conditions. Furthermore, as MoWiT is under development by Fraunhofer IWES, code modifications, optimizations, and enhancements are always possible [19,[25][26][27]. As presented in Figure 4, a FOWT, such as the OC3 spar-buoy system shown as well in Figure 5, consists of six main components, of which two are for the environmental parameters.…”

Larger MW-Class Floater Designs Without Upscaling?: A Direct Optimization Approach

“…The buoyancy force and righting moment are calculated in time-domain depending on the actual local surface elevation and the current position of the FOWT system. [5][6][7]…”

“…3, using Dymola as simulation engine. The modeling happens component-based as explained in [5], meaning that the entire system is split up into separate models for the support structure -comprising tower, floater, and mooring lines -, the nacelle with drivetrain and generator, the rotor -covering the blades and the hub -, the operating control, as well as two environmental models for wind and waves, including currents. In a separate study [8] the model of the spar-buoy FOWT is verified, using the code-to-code comparisons within the OC3 phase IV project [9].…”

Python-Modelica Framework for Automated Simulation and Optimization

“…This component-based structure of the MoWiT library simplifies the adaption and modification of a wind turbine model because single components can easily be exchanged or customized. (Leimeister and Thomas, 2017;Thomas et al, 2014;Strobel et al, 2011) Even if MoWiT can model the non-linear system behavior, a large number of simulations are required for the design of an optimized wind turbine system. For this purpose a Python-Modelica framework is developed for automated execution of simulations and optimization tasks.…”