Modelling of ST in CCGT mode for FR testing

asked 2019-09-10 01:50:08 -0500

KS gravatar image

Has anyone got any idea how a ST generator is modelled while in CCGT mode for FR testing? Most of the FR will be provided by GTs but need to see the ST generator response too. I have ST generator dynamic parameters and can assume for excitation system but I am not sure how to represent the governor model and parameters?

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If the CCGT is multi shaft unit, ST being in sliding pressure control it will simply follow the o/p of GTs , is there any way to represent this in PSSE for simulations?

KS gravatar imageKS ( 2019-09-10 03:26:20 -0500 )edit

If the steam turbine is sliding pressure control, as you said it will follow the gas turbine. Which means that the ST doesn't operate in speed or frequency control mode. So no governor model is required. If you want to have a governor model, use GGOV1 with high deadband

txc gravatar imagetxc ( 2019-09-10 08:39:58 -0500 )edit

Thanks@txc. I did the simulation as suggested. Whether I use a governor with high deadband or don't use the governor for ST, the ST loading is almost constant to its initial loading. GT loading changes according to the droop settings. Is this is a correct response?

KS gravatar imageKS ( 2019-09-10 09:20:05 -0500 )edit

Yes I agree. Here is what i think: Generally in a combined cycle plant, the ST operates in inlet pressure control. This is till the gas turbine has reached like 60 to 70% of its max capacity. Only time the ST responds to frequency is during start or shut down

txc gravatar imagetxc ( 2019-09-10 11:57:34 -0500 )edit

Thus the ST should be modeled with no governor or a governor with high deadband

txc gravatar imagetxc ( 2019-09-10 11:58:09 -0500 )edit