Blown up Cases in PSSE 1

[Tinh123]

Hi all,

Any advices in solving blown up case in PSSE? I have been burdened with a very difficult studied case and can't get it solve. Any strategy would be appreciated. Thanks.

 

[wbd]

What exactly is happening? I haven't used PSSE but in Easypower you can set parameters on solution mismatch to determine how close to solve on a Power Flow solution. I assume you are having power flow solution problems. Another issue I had on one of my systems was a phase shift integrity solution failure because of the way this system went through a 3 winding transformer and several other transformations, so I turned that check off.
I know with Easypower Tech Support, I can always send them the model and they can look at it and tell me what's wrong. Can you do that with PSSE?

 

[rbulsara]

What facts do you know? How would anyone else know from reading your post?

So what do you know about the case? What is PSSE?

 

[dpc]

Is this for steady-state power flow or transient analysis?

You can try here:

http://www.pti-us.com/pti/software/psse/user_support.cfm

 

[rbulsara]

ahh..some people can read mind!! LOL.

 

[Tinh123]

Sorry for the confusion. I'm new with PSS/E and looking for a general procedure/strategy in solving blown up case only. I'm sure some of you are well acquainted with the software and would have had experiences in dealing with these difficult cases. What to look for when the case blown up, and potentially, how it may be entangled. Thanks for any help.

 

[tlr7616]

Blown up, or diverged cases in power flow solutions are fairly common. The step by step method for "fixing" these runs like follows:

1. Identify what caused the divergence--i.e. did you add a new line, change a generation pattern, paste in a new sub system, etc. It helps to know where the maximum mismatch is at as well. Are you using divergence control in PSS/E? You should be...

2. Next step is really "playing " with the case, i.e. you sneak up on what is causing the divergent solution. This might mean setting bus angles to the same value when closing a line, chaning the X value to slowly put a line in service, adding temporary VAr support generators to help the case solve, etc. You might also slowly change load or generation output instead of all at once.

3. Always remember that the "slack generator" is in fact a real machine!!!!! Respect its limits--dispatch generation instead of letting the slack bus take all of the initial generation changes, etc

4. Be alert to the fact that divergence can mean a point of voltage collapse as well as simple numerical instability. Performing PV and QV curve analysis will help you see if this is in fact the problem.

5. Ask around at your place of work, an "old timer" will have knowledge of all of the tricks of the trade in helping a load flow solver solve a case.

6. Finally, don't forget that the PTI folks are an excellent resource. If you can send them the case they can help you understand why it isn't solving.

Also, don't forget that GE's PSLF and PowerWorld Simulator are other tools that might solve your case, I use all three and find that (at times) one program will solve a case that others will not. In my experience PowerWorld Simulator probably has the best solver for cases like what you are running into....

 

[Tinh123]

Thanks tlr,

Your help is much appreciated. Got my case working through series of grinding. Thank you.