OpenFast Controller Modelling

Dear All,

I am rather new to OpenFast. Currently I am working on a OpenFast model of a wind turbine similar to the AOC 15/50 which is used in the OpenFast r-tests. Currently I am working on the controller of the model but I am unsure about the right approach.

ServoDyn offers different possibilities for the controller. With the variable speed control and simple generator model I did not get the desired results yet.

A different option I tried is the Bladed-style DLL with the DISCON controller. I tried adapting the NREL 5MW Discon controller to the much smaller wind turbine model by making adjustments within the Fortran code and compiling a new dll file. So far I did not receive stable result in the pitch controller with the Bladed-style DLL. I am also not sure if this approach of making adjustments within in the Fortran code is the common approach to work with the Bladed-style DLL controller.

The available data of the generator I would like to model is very simple with 2 linear non-zero segments. Above the rated generator speed the pitch control sets in to limit the generator speed. Is there a common work flow for the modeling of the generator and controller with OpenFast?

Best regards,
Fabian

Dear Fabian,

How confident are you that your data sheet is representing the true torque-speed relationship of the generator? Does the generator really have two linear regions, or is this just a coarse representation of a quadratic relationship?

Since the NREL 5-MW baseline wind turbine and controller were released, NREL has developed ROSCO that provides a much more easily adoptable and more industry-representative baseline wind turbine controller: GitHub - NREL/ROSCO: A Reference Open Source Controller for Wind Turbines. We typically recommend using ROSCO to implement wind turbine controllers, but perhaps the controller you are trying to represent is more basic than that provided in ROSCO?

Best regards,