By default, parameter AP/APP.28 is set to a "0" for Process PID. A  s you see below this adds the main frequency reference based on the setting in frq/DRV07. This is more commonly suited for industrial applications that may be running a PID loop with a trim input.

If you are running a fan or pump application with a PID loop it is recommended to set this to "Normal PID", so set to a "1" for Pump n Fan .