Control of the turbine is performed through one or more DLL’s (Dynamic Link Library). The format for these DLL’s is very general, which means that any possible output sensor normally used for data file output can also be used as a sensor to the DLL. This allows the same DLL format to be used whether a control of a bearing angle, an external force or moment is submitted to the structure. The default controller supplied with code is an open source DLL including a pitchregulated variable speed controller.
External system interface
Another possibility is to connect user specified systems directly to HAWC2 by a so called external system interface. With this interface a set of user specified equations of motion for a dynamic system can be solved together with the equations of motion (EOMs) for the HAWC2 wind turbine model. The external system interacts with the HAWC2 model through a set of constraint equations which describes how the external system degrees of freedom (DOFs) and the HAWC2 DOFs are related. Both the EOMs for the external system and the constraint equations are specified in an external DLL which is then called by the HAWC2 solver during the simulation. In order for HAWC2 to be able to solve the combined EOMs, the external system DLL must return some specific information to HAWC2. Examples of external systems connected to HAWC2 are; dynamic mooring line model, gearbox model and a WAMIT interface.
The Basic DTU Wind Energy controller, which is an open-access controller designed for pitch-regulated variable speed wind turbines, can be accessed at a GitHub repository where current and future releases will be located.
Outputs from the code can be written to result files in either ASCII format or a more compressed binary format. It is also possible to write a special binary output file which can afterwards be used to animate the turbine behavior.