I am trying to change the exciter (which is built in block diagram) into the exciter model in library (AC1A exciter model), and after changing, the whole network became unstable. The exciter part is shown below. it was supposed to have better performance for the AC1A exciter, is it because the parameters of the AC1A has not been changed to the suitable parameters? Based on the initial values, the exciter AC1A is for output power of 120MW, and in my case, the synchronous machine should only produce 6MW.
Thank you very much.