Load Flow - How to make supply less than demand? 3

[bahamakyle]

Hi everyone. I'm trying to conduct a load flow study on a power grid. I would like to simulate situations where generation does not meet load demand but this does not seem to be possible. The swing generator always supplies the extra power needed and cancels my efforts. Is there a way for me to do this? Thank you for your help and have a great afternoon!

 

[davidbeach]

Put the swing generator remote, connected through a significant impedance.

 

[magoo2]

What you're trying to do is best handled by a stability program than a load flow. With a shortage of generation, the frequency will drop.

 

[bahamakyle]

Thank you for the replies davidbeach and magoo2. I tried connecting the swing generator through a significant impedance (I don't know what remote means though) but the low flow did not converge. I think you are right magoo2 and I may need to use a stability program. What I'm looking to do is to see the effect on bus voltages of not having enough generation capacity.

 

[dpc]

Typical power flow algorithms must have a swing source. As magoo2 indicated, what you are trying to do probably requires transient analysis.

If you don't have enough generation, the frequency will be a bigger concern than the voltage in most cases.



David Castor

http://www.cvoes.com

 

[bahamakyle]

Thanks dpc, I'll look at transient analysis and see where I can get. Thank you for the help everyone!

 

[tlrols]

You CANT'T do what you are asking in a power flow program. Supply=Demand + losses in a power flow. What will happen is the slack bus generator will have a negative value, in other words it will be a "load" from a real power perspective.

If you want a generation/load imbalance situation to occur you will have to use a time domain simulation. This is transient stability. As previously noted what you are describing as a study scenario will cause frequency to decrease. In fact, if you have no governor action modeled or frequency dependent load model the frequency will decrease all the way to zero! That is what happens when load is greater than generation.

Of course in a real power system that will NOT happen since governors act, AGC acts, people act, load IS frequency dependent, there ARE UFLS relays, etc, etc, etc...