the following error. "LowerSaturationLimit <= InitialCon​ditionForI​ntegrator <= UpperSaturationLimit"

I want to change the transformer secondary voltage from 208v to 380v, but I get the error message

"Lower saturation limit <= Integrator initial condition <= Upper saturation limit"

This is the result of limited output of the pid block.

So I turned off the output limit.

The results from the scope showed large fluctuations in voltage, current, and frequency.

Is it the right way to change the secondary side of the transformer to 380v just by unlocking the output limit?

Answer 1

[Angelo Yeo]

The issue stems from the change of behavior of initial condition of integrator and its output saturation limits. See the version history of PID Controller block at Continuous-time or discrete-time PID controller - Simulink (mathworks.com)

To quote:

R2022b: Issues error when integrator and filter initial conditions lie outside saturation limits

The block now issues an error when the integrator or filter initial condition value lies outside the output saturation limits. In previous releases, the block did not issue an error when these initial conditions had such values. If this change impacts your model, update the PID integrator or filter initial condition values such that they are within the output saturation limits.

Now, if you want to set an integrator initial condition that is outside the bounds of the output saturation limits, you can make the integrator initial condition external, and pass along the desired value for the initial condition to the PID Controller via a constant block.