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generator speed calculation

asked 2020-11-10 02:01:48 -0500

dunguyen9003 gravatar image

Hi all, Please help me with this issue. your support is invaluable to me I am studying the swing equation by using Psse. I made a dynamic test for one generator and try to use the result to compare with my calculation. This is the setting for the dynamic simulation: initial power = 0.5, step change = 0.1 (Pe = 0.6) This is the parameters of the target generator 101 'GENROU' 1 10.500 0.48000E-01 0.65000 0.50000E-01 5.7400 0.0000 2.3120 1.7770 0.24500 0.42700 0.18400 0.15700 0.12800 0.28600 /

After running the dynamic simulation on Psse. I try to recalculate the SPEED by using the swing equation on PSCAD. However, the result of mine and the result from Pss/e are different. This issue makes me confused about the swing equation. Could anyone pls help me? This is my calculation: d[deltaSPEED]/dt = (Pm - Pe)/(2 * 5.74)

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How big is the difference? Is it a single generator system? How do you change Pe?

perolofl gravatar imageperolofl ( 2020-11-11 01:45:00 -0500 )edit

I can not share to you the result in here. However, the Pe is the sum of step change and initial power in the dynamic solution. For example. I set up the initial power = 0.5 and step change = 0.1, the Pe = 0.6, cuz when the system is stable Pm = Pe.

dunguyen9003 gravatar imagedunguyen9003 ( 2020-11-25 20:34:40 -0500 )edit

Are you using GSTR/GRUN in PSSE? What is the result in PSSE?

perolofl gravatar imageperolofl ( 2020-11-26 01:43:41 -0500 )edit

Hi Perolofl, would you send me your email? I will show you my calculation via the email. I am using the governor test. Even I used GSTR/GRUN (used the channel to get the SPEED, Pmech, PELEC), the result does not match when I applied the swing equation for each generator.

dunguyen9003 gravatar imagedunguyen9003 ( 2020-11-26 02:40:58 -0500 )edit
perolofl gravatar imageperolofl ( 2020-11-26 03:24:13 -0500 )edit

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answered 2020-11-10 06:16:17 -0500

perolofl gravatar image

updated 2020-11-30 05:02:12 -0500

Have you enabled "Network frequency dependence" in "Dynamic Simulation Options"?


It seems like your results are correct and PSSE is giving wrong result in governor step response simulations.

STRT/RUN will give correct results regarding the swing equation if Network frequency dependence (NETFRQ) is activated. If NETFRQ is not used, the accelerating torque is wrongly calculated at off-nominal speeds, and the results will be too optimistic. It is therefore a good rule to always have NETFRQ activated in dynamic simulation options, even if it makes the dynamic simulation to take longer time.

In the simulation below (using STRT/RUN), the blue curve is with NETFRQ, giving correct results. The green curve is without NETFRQ, leading to wrong result. Please note that there is no network in this simulation and the difference comes from the generator modelling itself. A sudden load increase for a single generator/single bus system is simulated.

image description

Governor step response test with GSTR/GRUN is not using NETFRQ during the step response test (even if NETFRQ is activated in dynamic simulation options!) and thereby the swing equation is wrongly calculated and the results are not correct.

I have reported this bug to Siemens PTI, but they are reluctant to correct GSTR/GRUN, because "that it was a conscious decision by our founding fathers for whatever reasons". At this moment PTI is hesitating to correct the flaw of GSTR/GRUN that has existed in PSSE for around 40 years!

Consequently, governor response tests with GSTR/GRUN are not 100% accurate!

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Ah, yes. However, I did not see any difference

dunguyen9003 gravatar imagedunguyen9003 ( 2020-11-10 18:47:22 -0500 )edit

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Asked: 2020-11-10 02:01:48 -0500

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Last updated: Nov 30 '20