...
If the differential pressure across a control valve is maintained constant by means of a DPCV, the control valves authority is theoretically 1 and completely insensitive to hydraulic interactivity. This way the control performance
of the respective control loop might be increased. Via the token you can find 2 examples, in which a DPCV is placed over a control valve. The difference between the two examples is the position of the balance valve in the pressure measurement.
...