synchronous generator sudden load change effects

I am investigating the reactions of an 850 KVA synchronous generator to sudden load changes. The synchronous generator is 400 V and 6 poles. When I apply 680 kW as mechanical power and 680 kW as load and then remove this load, I want to draw the sudden acceleration graph of the rotor, but this works in the model I created. The simulation is 10 seconds and I completely remove the load in the 3rd second. I am not sure about the values ​​such as the moment of inertia of the generator. The motor slows down when it should be accelerating, I cannot make sense of this. I need help.

Answer 1

[Sabin]

Without the model and all the parameters used in simulation it is not easy to point exactly to the root cause. However, this seems to be parameterization problem. Double check the Breaker resistance and snubber resistance and the machine parameterization.