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I am facing this problem, it may appear that I am asking an answer for homework, but it is not.

I am studying load frequency control, and it was given a series of problems like this: Frequency control porlblem

The solution is quite easy, however the new output of one of the units is greater than the max output, in this case, unit 3 new output is 157MW. I asked to my professor how should I approach the question if this issue appears, He said it should be obvious and I should think about it.

Then...I am thinking and thinking and thinkig, and I can not see a solution different from taking the excess from unit 3 and give it to unit 4 for example, however, i am sure it is not easy like that and it must have a mathematical explanation and more important, an important concept i am missing.

Could you help me understand what I am missing here? thanks

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In this case, if we neglect the frequency dependency of the demand, all generators are going to be loaded with their rated power as the deficit in power (70) is equal to the left margin of G2, G3 and G4. However, to get more accurate results, we should take that dependency into account.

Mathematically it can be solved as follows, as soon as you get G3 power (156.51 MW) you can set its power to nominal power (150 MW) and redistribute the (6.51 MW) between the G2 and G4. This can be done by following the same procedure of losing the 70 MW. I got the following numbers PG2=199.753 MW and PG4=297.037 MW.

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  • \$\begingroup\$ Perfect! Got the concept and the same numbers here, you saved me \$\endgroup\$ Oct 6 '17 at 6:48

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