# Adding primary reserve limits to dynamic model using HYGOV

Hello,

I have a model which works nicely but need to add limits to primary reserves for frequency response. The model uses HYGOV for primary response. Have tried to use GMAX, PGEN and MBASE to set the reserve limit.

My thoughts so far: Reduction of GMAX will reduce the amount of primary reserves available, as turbine inflow limits are regulated.

Calculation example: If PGEN = 900 MW, and MBASE = 1200 MW, there is 300 MW of reserves available for primary response as primary reserves at the generator until. Setting GMAX = 0.75 means that the maximum gate opening at the turbine is 1200 MW * 0.75 = 900 MW, meaning that the turbine or PMECH may only reach 900 MW, implying 0 primary reserves. GMAX = 0.8 would mean a maximum output of 960 MW, meaning 960 - 900 = 60 MW as primary reserves.

This does not work as intended. I get a lower PMECH than what my calculations here show. Where am I mistaken? How do I add primary reserve limits?

In the end I need to cap primary reserves at 1800 MW for the system. I assume this can be done by adjusting GMAX individually at all HYGOVs in the system for a given operating state.

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In HYGOV the governor position p.u. value differ from the generator power p.u. value due to qNL and At parameters.

Calculate Gmax in the following way:

Gmax = Pmax/(Mbase*At) + qNL


For example if At = 1.2 and qNL = 0.08:

Gmax = 900/(1200*1.2) + 0.08 = 0.705

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Thank you for your response. Did you mean Pgen instead of Pmax in the first formula? I thought Pmax was not used in dynamic simulations other than for p.u. values. Also (of lower importance), do you recall in which reference this formula is given?

( 2018-11-01 09:49:46 -0500 )edit

Nevermind! Tested it. If I want to have 60 MW as reserves at the given generator, I input Pmax = 960 in the formula you gave and otherwise use Mbase and HYGOV settings in the formula. Thanks a lot!

( 2018-11-01 10:11:33 -0500 )edit

Yes, Pmax is here the maximum Pmech limit in MW. I have no reference for the formula, I found it out myself many years ago...

( 2018-11-01 10:29:23 -0500 )edit