The model has time-varying line and load disturbances modeled as step functions that will
interfere with the frequency response estimation. To hold these disturbances constant
during the simulation, click More Options. Then, in the Options for frequency response
estimation dialog box, on the Time Varying Sources tab, click Find and add time
varying source blocks automatically.To estimate and plot the frequency response, on the Estimation tab, click Bode.7 PID Controller Tuning