Dear Bishal

I have performed so many power flow studies using DIgSILENT, PowerWorld, NEPLAN, EasyPower software and I have used one slack-swing bus and if isolated subsystems occured programs automaticaly chose swinging bus for them. I do not use ETAP so don't know why it fores  8 to 11 PV busbars to forse them from PV to swing nodes?? Maybe some ETAP user can  help you.

Srete

Dear Srete Sir,

I used PowerWorld too but for small grid and for predefined IEEE buses only and i got good enough results. Currently, i am trying to simulate much vague and undefined network ( approximately 100 bus network of 132 kV gradient.). so, i opted for ETAP but it is giving me quite a headache.

Will keep you updated. Thanks and regards.

Your question is quite odd. Only one bus serves as the reference (swing) bus. Period. The thing is, you probably have more than one generator connected to the swing bus. After the PF converges, the program calculates P, Q in the swing bus, and shares them among all the generators in the swing bus. Try to increase the P and Q limits of the generators in the swing bus and see what happens.

Dear Pedro sir,

  I admit it is quite peculiar.  Ligically,  it makes no sense.  There must be some error in my simulation which i haven't   been able to rectify as of yet.  Thanks for ur help. 

Further more,  as i try to simulate the grid network with largest generator bus as swing bus and all other generator buses as voltage controlled bus,  the largest generator is highly overloaded  and other  generators donot inject power at all.  Instead,  the load angle or delta at those generator bus during operating conditions becomes negative and thus the generators themselves act as power sink instead of source.  

I find this quite abnormal and yet irritating as i am not able to rectify it yet.  Any help in this regard  would be great. 

Regards. 

Dear Srete sir and Pedro sir.

Happy to inform you that i finally got the solution. Thanks for your help. Load flow is converging, grid is acting perfectly normal and i got my answer.

regards,

Bishal

So, what was the problem?

Dear Pedro Sir,

I later on realized that it was because of HVDC link between different regions of my test grid which might have caused slight frequency variation and thus necessity of multiple slack bus.

For now, i am not considering HVDC link anymore for simplifying my network. May be at later stage and thus one slack bus would suffice.

Regards,

Bishal

Hi Mr. Gautham,

Yes. That is what i realized for now. i wish to continue and will keep you updated.

Regards 

Dear Bishal

If you have HVDC link and during the power flow software need to split system in two parts and automaticaly chose another generator as a slack bus in isolated, both subsystems. Some software do that automaticaly ??

Dear Srete sir, 

Thanks for the suggestion.  As far as the automatic  slack bus selection by software is concerned,  i am not sure how effective and real world that can be as i am more familiar with Power world and ETAP only.  Both seems to do just fine. I personally  prefer ETAP  because of its reliability and better recognization throughout.   Will keep you updated. 

Regards. 

Those of you that don't (never) use ETAP,

can confuse ETAP users even more

ETAP's definition of "Swing" generator is DIFFERENT from your traditional understanding of "Slack bus" (on per system for calculation purposes)

Basically Setting A generator to "Swing mode" just means it's an flexible(output/input/entrance/exit )

If everything converges, it wouldn't matter which are set to swing

If you have overflow or underflow, that the SWIng Generators will  output the flow

Think of POKING holes in an overflowing water ballon (SWING),

Yes you can poke more than 1 hole!

This is a horrible analogy