Limitation of duty cicle of PWM range

YOU have to limit the range, and you almost certainly will want to do so inside the PID. If you're using the standard Arduino PID, there is a call to set the min and max limits. If not, then you simply need to add that, and add a check to the periodic compute function that restricts the output to the desired range, and clips it if it exceeds the range.

Regards,
Ray L.