Hello.
Normally CCPP has 1+1+1, 2+2+1 and 3+3+1 in one block.
I would like to know the maximum number of gas turbines in one block.
Now I consider 2 blocks with 4+1+1 or one block with 7+7+2.
Are there any problems in case of these configurations?
 

Two GTs to One STG is common arrangement that I have come across.
If a station has only three GTGs, I have also seen all the three GTGs to one STG.
Cost, Space, Reliability, Environment wtc. are the factors that govern the decision I guess.

The answer to the question is dependent upon how much and how often you plan to operate this plant at part load vs. full load.  Where I have seen the 3 X 1 on 1 used was to give the ability to operate at lower loads at higher efficiency and faster dispatch.  You have to look at the partial load efficiency curves of each type of turbine and determine what fits your system demands the best.  If you are going to run flat out all the time, then the lowest capital cost governs.  If you are going to run at partial or varying loads, then efficiency is going to be an important consideration.

rmw