Nonlinear loads impact on synchronous generator stability??? 1

[sykimk]

Hi!

I am really curious about a topic how nonliear loads such as large VSDs, arc furnaces, etc. would impact on power system stability especially for synchronous generator stability.

Sometimes, I have doubt whether it would be really concerned problems from the viewpoint of power system stability related matters.

If there is anyone who can give some brightest idea or advice such as the recommended journal papers or books, it would be highly apprecited.

Thanks in advance again.

 

[electricpete]

I don't think they have much impact on stability in practical systems. I have never seen it mentioned in discussions of power system stability.

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[itsmoked]

electricpete; aren't they rather attenuated after passing by umpteen capacitor banks, and lots of transformers/substations, then down miles of transmission line? Rather like conducted EMI.

 

[electricpete]

Probably so.

I don't pretend to know the technical reason but I took a graduate level course in power system stability and the subject was not mentioned. Also have 3 textbooks on that subject (from the course) sitting in my closet and a quick look didn't show any discussion.

If it were important I think it would've been covered.

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[ccjersey]

This seems to be a concern in situations with the loads in question being a large part of the generator capacity. For example a backup generator feeding a data processing center through a UPS. The older voltage regulators apparently didn't perform very well in this situation.

Jim

 

[bacon4life]

By nonlinear, do you mean loads with harmonics? Or constant current and constant power loads vs constant impedance. It seems like harmonics would be attenuated unless it was an application like Jim suggested.

In the system stability class we did not talk about any effects of nonlinear loads other than how they change the type of loading. Especially for voltage stability analysis using the correct load model would be important. Constant impedance, constant current and constant power loads all affect voltage decay differently.

We talked about the effect of load models on transient and small signal stability, but most of the class was focused on the utility system because loads are so hard to characterize. There is apparently a fair amount of work still going into modeling induction motors-one of the other students was working on a model for single phase motors. By itself each one is small but there are a lot of them connected.

 

[electricpete]

Looking at large interconnected grids, as itsmoked said the harmonics will be filtered both by the series inductance and the parallel capacitance. And typically these loads are small compared to other types of loads on the sytem.

The situation ccjersey mentioned is a different situation. I'm sure harmonics can be important for the case described there. I wouldn't have put that under the category power system stability but maybe that's semantics.

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