Cannot get a proper frequency response in the power system simulation

I have been working on a power system simulation which incoporates 3x300MW generators connected to the grid in simulink. I want a certain frequency response by varying the governer parameters. the system doest seem to stabilize frequency at the constant value of 50Hz. I tried implementing a constant voltage source as a swing generator but it overcompensates so i cannot identify my frequency response as i need and the governer parameters also do not seem to work. i tried implementing a swing generator using synchronous machine block which gave favourable response but didnt settle the frequency at 50Hz.

I also wanted my grid system to function in droop mode while my generators function at a active power set point. but it doesnt seem possible due to the above scenario.

i have attached my file also.