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Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Sun Jun 09, 2019 4:52 pm
by Boran.Zhao
Hello,

I am currently working on control of the NREL 5MW baseline turbine on a semi-submersible platform. I want to use FAST linearization to get a linearized model for controller design:

dx_dot = A dx + B u + Bv v + Bw w, (1)
where v and w are wind and wave disturbances, respectively.

As far as I know, FAST 7 does not provide the wave disturbance matrix Bw in (1). Can anybody tell me whether the lastest FAST version, e.g. FAST 8 or OpenFAST, has the capability to generate this matrix?

Thank you.

Best
Boran

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Mon Jun 10, 2019 1:04 am
by Jason.Jonkman
Dear Boran,

We have recently added linearization functionality in OpenFAST for floating offshore wind turbines, including linearization of MAP++ and HydroDyn, the latter of which includes the ability to include a wave disturbance in state-space form (in addition to the linearization of wind turbine related modules previously available). See our IOWTC 2018 paper for more information: https://www.nrel.gov/docs/fy19osti/71865.pdf. We presented the verification results at the DeepWind 2019 conference in January (paper still in the publication process). We are currently finalizing the verification results and documentation before the public release.

Best regards,

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Mon Jun 10, 2019 10:04 am
by Boran.Zhao
Dear Dr. Jonkman,

Thank you very much for your quick response. I look forward to the function of wave disturbance matrix generation to be released. Do you have a rough estimate of when the release will happen?

I have another question. I previously used FAST 7 to simulate the NREL 5MW baseline turbine on a submersible platform (https://www.nrel.gov/docs/fy14osti/60601.pdf). I have not started using OpenFAST yet. I just wonder whether the configuration files (.dat, .ipt, .fst) for the turbine and the semi-submersible platform ( used for FAST7) be directly used for OpenFAST?

Thank you.

Best
Boran

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Tue Jun 11, 2019 12:56 am
by Jason.Jonkman
Dear Boran,

The verification work is nearing completion and I expect that we'll release the update to OpenFAST later this summer.

The input files for FAST v7 are not compatible with OpenFAST. However, in the FAST v8 release (https://nwtc.nrel.gov/FAST8), NREL has provided MATLAB-based conversion scripts to convert FAST v7 input files to input files compatible with FAST v8. And there are only a few updates to the input files between FAST v8 and OpenFAST.

Best regards,

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Wed Jun 12, 2019 9:08 am
by Boran.Zhao
Dear Dr. Jonkman,

Thank you very much for your further explanation.

Best
Boran

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Tue Oct 15, 2019 5:08 am
by Zhe.Zhang
Dear Dr. Jonkman,
I want to use the openfast2.0 to realize the TLP type of floating wind turbine linearization, can you give me some information, because I still don't understand the logic of linearization.
Thank you.

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Tue Oct 15, 2019 6:29 am
by Jason.Jonkman
Dear Zhe.Zhang,

The verification work for the new floating wind linearization capability has now been complete, but I don't believe the papers from the DeepWind 2019 conference (to be published in the Energy Procedia journal) have been published yet. While I'm not exactly sure of the reason for the delay, but the linearization functionality has not yet been merged into the dev or master branches of OpenFAST (and so, is not included in OpenFAST v2.0 or v2.1). The new floating wind linearization capability was developed in a fork of OpenFAST and should get merged into OpenFAST dev soon.

Best regards,

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Tue Oct 15, 2019 7:35 am
by Zhe.Zhang
Dear Dr. Jonkman,
Thank you very much for your quick response.Do you mean that I want to achieve linearization of floating wind turbines only with FAST 7?
Thank you.

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Tue Oct 15, 2019 7:40 am
by Jason.Jonkman
Dear Zhe.Zhang,

You can use FAST v7, but the linearization functionality of FAST v7 does not include linearization of the wave-excitation or wave-radiation terms, which are included in the new linearization capability implemented in OpenFAST.

Best regards,

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Mon Oct 21, 2019 8:24 pm
by Zhe.Zhang
Dear Dr. Jonkman,
I used FAST7 to linearize the TLP-type floating wind turbine, but the generator torque is always 0 during the linearization process. Is this normal?

Re: Does linearization provides wave disturbance matrix in the latest FAST?

Posted: Mon Oct 21, 2019 10:16 pm
by Jason.Jonkman
Dear Zhe.Zhang,

When trimming blade-pitch angle (TrimCase = 3) in FAST v7, normally you'd set constant (nonzero) generator torque. The constant generator torque can be set using the VSContrl = 1 option -- see the "Linearization" section of the old FAST User's Guide for more information: https://nwtc.nrel.gov/system/files/FAST.pdf.

Best regards,