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Speed Governor (K) of GAST2A initialized out of limits

asked 2017-08-23 03:32:35 -0500

ffl gravatar image

I'm trying to resolve this initial condition suspect because the flat run plots that I obtained is not flat at all. The subject unit achieves a new operating point after 1 s. Please note that I haven't applied any fault/disturbance. Here is the info:

Initial Condition Suspect

94202 -1.6832 -0.10000 GAST2A K
94203 1.2961 0.88196E-01 GAST2A K+1
94207 1.4184 -3.1806 GAST2A K+5
94214 2.5922 0.0000 GAST2A K+12

The power flow conditions of the machine were as follows: Pgen = 13.7862 Pmax = 36.1 Pmin = 0.0 Qgen = 12.3348 Qmax = 15.43 Qmin = -11.76 MVAbase = 46.5

The Dynamic Data are as follows: 'GAST2A' 2 25.0 0.0 0.05 1.0
0.02 0.1 40.0 0.25 1.5
-0.1 0.01 0.77 1.0 0.05
1.0 0.4 0.0 0.2 0.8
15.0 2.5 450.0 3.3 700.0
550.0 0.23 1.3 0.5 1020.0
0.23 1020.0

Could anyone suggest possible error debugging? Thank you.

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answered 2017-09-05 15:01:02 -0500

perolofl gravatar image

Unfortunately the MAX and MIN limits are not in pu on turbine rating, even if the manual wrongly says that. There are many errors in the manual!

With Pgen=13.7862 MW the speed governor signal (STATE K) is initialised to -0.1842. With your MIN-limit of -0.1 there is a violation of MIN limit and initial conditions suspect for STATE K, K+1 and K+12. State K+5 is normally causing initial conditions suspect but that can be ignored.

With load flow data Pmax=36.1 MW and Pmin=0 MW and your GAST2A parameters you must choose MIN = -0.5285 and MAX = 0.37313 for the speed governor limits in model GAST2A. Please note that the MIN-value is negative, corresponding to a generator power of 0 MW.

I have assumed that Rsource is zero for the generator so there are no generator losses to be considered.

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Hi, Please be informed that I set the MIN value of the GAST2A model to -1.0 and I got a flat response of the generator associated with this model although the K+5 suspect is still present. I have performed calculations too but I would like to know how the values above were calculated. Thank you.

ffl gravatar imageffl ( 2017-09-12 08:04:25 -0500 )edit

Have you tested the values I am proposing above? The values are calculated as follows: MAX=((Pmax/Trate - af2)/bf2 - K6)/K3, MIN=((Pmin/Trate - af2)/bf2 - K6)/K3

perolofl gravatar imageperolofl ( 2017-09-12 15:56:21 -0500 )edit

Please note that it is important to set both limits properly. With too wide limits the generator may give too much spinning reserve at large frequency deviations. E.g. much more than 100% power at under-frequency.

perolofl gravatar imageperolofl ( 2017-09-12 15:59:30 -0500 )edit

Hi perolofl, I don't tested it yet. The utility accepted the change in MIN to -1.0 but as you mentioned, I'm already thinking of the effect of large difference in limits.

ffl gravatar imageffl ( 2017-09-12 23:48:02 -0500 )edit

Hi https://psspy.org/psse-help-forum/users/38710/perolofl/, May I know how did you arrive with the formula above? If the manual says wrong, then my calculations made before based on the manual is also wrong.

ffl gravatar imageffl ( 2017-09-14 03:19:44 -0500 )edit
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answered 2017-09-03 17:48:09 -0500

zezo510 gravatar image

The highlighted values below are the Max and Min governor limits in pu (on the turbine MW rating).

'GAST2A' 2 25.0 0.0 0.05 1.0 0.02 0.1 40.0 0.25 1.5 -0.1 0.01 0.77 1.0 0.05 1.0 0.4 0.0 0.2 0.8 15.0 2.5 450.0 3.3 700.0 550.0 0.23 1.3 0.5 1020.0 0.23 1020.0

Therefore, I would think that it's not possible to set them outside the range (0,1)

Try setting them as follows:

MAX = (Pmax/turbine rating)

MIN = (Pmin/turbine rating)

Note: the turbine rating to be taken in the calculation is the one entered in your dynamic model (40 MW in your case).

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Asked: 2017-08-23 03:32:35 -0500

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Last updated: Sep 05 '17