PID pump controller for VSD

I'm looking for a PID pump controller that can control VSD for constant pressure in a multiple pumps booster system. The main objective of the booster system is to delivery constant pressure at all time regardless of the demand of flow capacity to be deliver from the booster system. Pump type used are cetrifugal pumps. configuration of the system is with choices of single VSD for multiple pumps and multiple VSD for multiple pumps.

please advise where can i get this type of PID pump controller.