Pros/Cons of voltage control methods

[Damianj]

Hi,

I have the following voltage control problem for which I'd appreciate any opinions from other members in the group:

We have a power network consisting of 10 x 42.5MVA gas turbine generators (GTGs) which are distributed over four separate substations such that at there are three GTGs installed on the first, three on the second, two on the third and two on the fourth. Each substation has a common 33kV bus and the substations are tied together via a 132kV bus so that power flow from one substation to another is possible (via 132/33 transformers) if there is more load on a substation than the local generation can supply. (The 132k bus is NOT connected to a utility grid.)

My problem is that there does not appear to be obvious solution to controlling the voltage on the system and it is difficult to determine whether the system will really behave as predicted in the modelling software.

It appears that setting all generators to voltage control mode and allowing them to control the local 33kV bus to within 0.99 and 1.01pu whilst also allowing the local 33/132kV transformer to maintain the 33kV voltage at 1pu (but setting its relay bandwidth to +/- 1.5% so that it should not conflict with the generator voltage control) appears to maintain the 33kV and 132kV voltages to +/- 5% for a wide variety of loads / generator combinations.

Other options I'm looking at include using the two generators on the 4th substation to control the 132kV busbar voltage but then setting all other generators to run on voltage control as described above. If either of these generators are out of service then the system would switch to the mode described in the previous paragraph.

Any opinions on similar systems and experience of problems with the methods described above would be much appreciated!

Damian

 

[Rodmcm]

You do not say whether there is auto tap control on the 33kV/132 step up transformers. Assuming that there is then I would use one set of generators to hold the 132kV ( with suitable safegaurds on the 33kV bus, and let the transformers tapchange to hold the 33kV on the other busses. By scada you can always monitor the other busses and change the 132kBV voltage if the other transfomers are getting to the limits of their tap range.The other generators can then just run to the 33kV busses. As well as this I would use the same set doing the voltage control to do the frequency control.

If you think about it this is haw any island state is run

 

[mplsscooter]

Hi
I have run into simmilar fluctuations on a lot smaller system 6 500kw spread out over some distance, we had to add capacitors at some distribution points and reactance at others seem we were fighting some harmonics uder certain load conditions