Swing type generator in system modeling
Swing type generator in system modeling
(OP)
Hi all:
why is it that only one "swing" type generator can be in the model?
why is it that only one "swing" type generator can be in the model?
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Swing type generator in system modeling
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Swing type generator in system modelingSwing type generator in system modeling(OP)
Hi all:
why is it that only one "swing" type generator can be in the model? Red Flag SubmittedThank you for helping keep Eng-Tips Forums free from inappropriate posts. Reply To This ThreadPosting in the Eng-Tips forums is a member-only feature.Click Here to join Eng-Tips and talk with other members! |
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RE: Swing type generator in system modeling
The software I use (EasyPower) allows any number of swing sources for power flow analysis. There can be convergence issues, but normally it's fixable. Swing sources can be specified with a specific power angle.
RE: Swing type generator in system modeling
RE: Swing type generator in system modeling
But how does swing type gen translate to the "real" world?
I understand most of generators will be PV type or schedulled power ?
RE: Swing type generator in system modeling
RE: Swing type generator in system modeling
In the real world, the theoretical connection with no voltage change is not possible.
RE: Swing type generator in system modeling
In the real world, where you have local generators in parallel with a power grid, the utility sources function essentially as swing buses (within reason), providing whatever power and vars are required or absorbing any excess from the local generators.
RE: Swing type generator in system modeling
DanDel - thank you, but are you saying we model different types of gens just for mathematical calculation (they don't exist in reality?)
dpc:
So, I understand "spinning reserve" generation is to make up for lack of generation (usualy gas turbines, for fast demand changes), and every generator "type" with voltage regulator (AVR)can "consume" excess of VAR's to their machine limitations, not just swing type gens. Is "swing" generator (IEEE says biggest gen in utility studies or utility source for industrial study) strogest source of scheduled generation or the one who deliver less or more Watts/VARs quickly enough when needed?. So is it fair to say that this is not strongest source but one with quickest
dS/dt?
Thanks everyone.
RE: Swing type generator in system modeling
Unless you can model the entirety of your system, all generators and all loads, you will have to make some compromises and you have to know when you are close enough.
The utility connection that always gets modeled as a swing bus isn't really, load will change the voltage, but not by much and not enough to make worth the complication of modeling those affects. Part of engineering is knowing when you are close enough to the answer. If you have line models that get you to within a percent or two of the correct phase impedance (never mind your zero sequence impedance) then getting the contributions from each source nailed down to the 1/10 of a percent is false precision and a waste of time because you are now at 1/10% +/- 2%; whoopee!
If your maximum load change is small compared to the system feeding it, you can treat the source as a swing source with instantaneous response, not exactly true but close enough. On the other hand, if you are modeling 1.8MW of load being fed from two 1MW generators you will need to see all the system effects. If the software places the generator impedance after the voltage control point (the right place for fault studies but the wrong place for load flow) you may have to adjust the voltage of your swing source to overcome the voltage drop of its internal impedance.
I'd start any study with all sources as swing, but with a rated capacity, and see where the numbers fall compared to how you think the system is going to operate. If the result is close to how it should be, then you might find it could operate with reasonable stability. If you have to use PV and PQ sources to force significant changes in load flow you might want to reexamine your expectations or your model.
Yeah, if you've got local generation running in parallel with the utility and the operating mode is fixed watt and var output go ahead and model it that way; but any source that has some freedom of operation should start out as a swing source and then be modified if/as needed.
RE: Swing type generator in system modeling
A 'swing' bus is the bus in the system model whose voltage does not change. This is necessary for the calculation (it is usually the Utility connection bus).
In ETAP, you can also model a generator as 'Voltage Control', 'VAR Control', PF Control', etc., based on the software (SKM has SB, PV, & PQ options). But you must have at least one swing bus in any case. Making the generator anything but a swing bus, the generator voltage will change during the analyses.
Aren't you talking about a computer model?
RE: Swing type generator in system modeling