Add documentation for the use of WHOC and ROSCO as FAST.Farm supercontrollers

Author: Abhineet Gupta

docs/source/user/fast.farm/Introduction.rst

@@ -373,6 +373,32 @@ FAST.Farm and OpenFAST can be read with standard open-source
 visualization packages such as `ParaView <http://www.paraview.org/>`__
 or `VisIt <https://wci.llnl.gov/simulation/computer-codes/visit/>`__.
 
+Turbine controller and super controller
+---------------------------------------
+
+FAST.Farm does not include modules for individual turbine controllers
+or farm-level controller (super controllers) and relies on
+separately compiled routines for them.
+FAST.Farm defers to the OpenFAST model of individual turbine for turbine controller.
+The controller is specified in the ServoDyn module of OpenFAST.
+OpenFAST allows for the use of bladed-style controllers in DLL format.
+Tools like `Reference Open Source Controller` (`ROSCO <https://github.com/NREL/ROSCO>`_)
+can be used to design and integrate turbine controller in DLL format.
+
+Farm-level super controller can be designed and implemented using external tools.
+`Wind-Hybrid-Open-Controller` (`WHOC <https://github.com/NREL/wind-hybrid-open-controller>`_) tool
+provides for rapid design of common farm-level controllers such as wake steering
+control, spatial filtering/consensus and active power control etc.
+WHOC includes examples the design of a wake steering controller and implementation on
+a small farm using FAST.Farm.
+The `Reference Open Source Controller` (`ROSCO <https://github.com/NREL/ROSCO>`_)
+also has wind farm control capability.
+It gives user low-level access to various turbine measurements and offsets, and
+enables implementation of user-written, python-based controllers.
+ROSCO also includes examples demonstrating the implementation of a farm-level
+controller in FAST.Farm.
+
+
 FAST.Farm Parallelization
 -------------------------
 

docs/source/user/fast.farm/ModelGuidance.rst

@@ -931,15 +931,6 @@ simulations for the NREL 5MW turbine
 ( :cite:`ff-Doubrawa18_1`), but these can be overwritten by the
 user.
 
-.. _FF:sec:SupCon:
-
-Farm Level Control
-------------------
-
-FAST.Farm does not include a module for farm level control.
-Users are advised to utilize the wind farm control capability of 
-the `Reference Open Source Controller` (`ROSCO <https://github.com/NREL/ROSCO>`_)
-to implement farm level controller.
 
 Commonly Encountered Errors
 ---------------------------