3. ROSCO Examples

Methods for reading turbine models, generating the control parameters of a DISCON.IN: file, and running aeroelastic simulations to test controllers Reading Turbine Models ———————- Control parameters depend on the turbine model. The rosco.toolbox uses OpenFAST inputs and an additional .yaml formatted file to set up a turbine object in python. Several OpenFAST inputs are located in Test_Cases/. The controller tuning .yaml are located in Tune_Cases/. A detailed description of the ROSCO control inputs and tuning .yaml are provided in The DISCON.IN file and ROSCO_Toolbox tuning .yaml, respectively.

  • 01_turbine_model.py loads an OpenFAST turbine model and displays a summary of its information

ROSCO requires the power and thrust coefficients for tuning control inputs and running the extended Kalman filter wind speed estimator.

  • 02_ccblade.py runs cc-blade, a blade element momentum solver from WISDEM, to generate a \(C_p\) surface.

The Cp_Cq_Ct.txt (or similar) file contains the rotor performance tables that are necessary to run the ROSCO controller. This file can be located wherever you desire, just be sure to point to it properly with the PerfFileName parameter in DISCON.IN.

3.1. Tuning Controllers and Generating DISCON.IN

The ROSCO turbine object, which contains turbine information required for controller tuning, along with control parameters in the tuning yaml and the \(C_p\) surface are used to generate control parameters and DISCON.IN files. To tune the PI gains of the torque control, set omega_vs and zeta_vs in the yaml. Similarly, set omega_pc and zeta_pc to tune the PI pitch controller; gain scheduling is automatically handled using turbine information. Generally omega_* increases the responsiveness of the controller, reducing generator speed variations, but an also increases loading on the turbine. zeta_* changes the damping of the controller and is generally less important of a tuning parameter, but could also help with loading. The default parameters in Tune_Cases/ are known to work well with the turbines in this repository.

  • 03_tune_controller.py loads a turbine and tunes the PI control gains

  • 04_simple_sim.py tunes a controller and runs a simple simualtion (not using OpenFAST)

  • 05_openfast_sim.py loads a turbine, tunes a controller, and runs an OpenFAST simulation

Each of these examples generates a DISCON.IN file, which is an input to libdiscon.*. When running the controller in OpenFAST, DISCON.IN must be appropriately named using the DLL_FileName parameter in ServoDyn.

OpenFAST can be installed from source or in a conda environment using:

conda install -c conda-forge openfast

ROSCO can implement peak shaving (or thrust clipping) by changing the minimum pitch angle based on the estimated wind speed:

  • 06_peak_shaving.py loads a turbine and tunes a controller with peak shaving.

By setting the ps_percent value in the tuning yaml, the minimum pitch versus wind speed table changes and is updated in the DISCON.IN file.

ROSCO also contains a method for distributed aerodynamic control (e.g., via trailing edge flaps):

  • 09_distributed_aero.py tunes a controller for distributed aerodynamic control

The ROSCO toolbox also contains methods for working with OpenFAST linear models * 10_linear_params.py exports a file of the parameters used for the simplified linear models used to tune ROSCO * 11_robust_tuning.py shows how linear models generated using OpenFAST can be used to tune controllers with robust stability properties. * 12_tune_ipc.py shows the tuning procedure for IPC

3.2. Running OpenFAST Simulations

To run an aeroelastic simulation with ROSCO, the ROSCO input (DISCON.IN) must point to a properly formatted Cp_Cq_Ct.txt file using the PerfFileName parameter. If called from OpenFAST, the main OpenFAST input points to the ServoDyn input, which points to the DISCON.IN file and the libdiscon.* dynamic library.

For example in Test_Cases/NREL-5MW:

  • NREL-5MW.fst has "NRELOffshrBsline5MW_Onshore_ServoDyn.dat" as the ServoFile input

  • NRELOffshrBsline5MW_Onshore_ServoDyn.dat has "../../ROSCO/build/libdiscon.dylib" as the DLL_FileName input and "DISCON.IN" as the DLL_InFile input. Note that these file paths are relative to the path of the main fast input (NREL-5MW.fst)

  • DISCON.IN has "Cp_Ct_Cq.NREL5MW.txt" as the PerfFileName input

The rosco.toolbox has methods for running OpenFAST (and other) binary executables using system calls, as well as post-processing tools in ofTools/.

Several example scripts are set up to quickly simulate ROSCO with OpenFAST:

  • 05_openfast_sim.py loads a turbine, tunes a controller, and runs an OpenFAST simulation

  • 07_openfast_outputs.py loads the OpenFAST output files and plots the results

  • 08_run_turbsim.py runs TurbSim, for generating turbulent wind inputs

  • 14_open_loop_control.py runs an OpenFAST simulation with ROSCO providing open loop control inputs

3.3. Testing ROSCO

The rosco.toolbox also contains tools for testing ROSCO in IEC design load cases (DLCs), located in ROSCO_testing/. The script run_Testing.py allows the user to set up their own set of tests. By setting testtype, the user can run a variety of tests:

  • lite, which runs DLC 1.1 simulations at 5 wind speed from cut-in to cut-out, in 330 second simulations

  • heavy, which runs DLC 1.3 from cut-in to cut-out in 2 m/s steps and 2 seeds for each, in 630 seconds, as well as DLC 1.4 simulations

  • binary-comp, where the user can compare libdiscon.* dynamic libraries (compiled ROSCO source code), with either a lite or heavy set of simulations

  • discon-comp, where the user can compare DISCON.IN controller tunings (and the complied ROSCO source is constant)

Setting the turbine2test allows the user to test either the IEA-15MW with the UMaine floating semisubmersible or the NREL-5MW reference onshore turbine.