V/F closed loop control of 3-phase Induction Motor

I want to design a closed loop speed control of V/F control for three phase induction motor in MATLAB.I stuck at a point that after T=2.2(Simulation Time) at Tm=0(Torque to motor), the system becomes too much unstable and the speed starts to decrease drastically. Also if the load is change, the instant(T) of starting unstability changes.I know the unstability is due to the PI controller but, i didn't find any clue to fix it, so i want help in designing it's closed loop part.

Answer 1

[Sabin]

The PI integrator is too aggressive. Reducing the integral gain will fix the problem in this case. As there is an integrator in the plant, we don’t need too much integral action in the control. For this model using Ki=0.1 will run smootly.