Best Way to Control 6 Chiller Pumps: Is VFD Suitable Without Reducing Pump Head?

dears,
i have below question, if anybody knows please help me...
there  are 6 chillers that need 6 pumps. each chiller 1 pump. now for controlling these pumps what is best solution. i consider VFD. is it ok ? or not  "please consider that débit and head of pumps is important for us and do not want to reduce head during operation of chiller"

More information please.  How powerful are these pumps?  What power is available?  Is variable speed needed?   If only on/off operation is needed and AC is available, then VFDs would unnecessarily complicate this.  When you say "Head of pumps" I presume you mean how far up they have to pump their liquid?   When do the pumps need to operate?  If in response to external conditions then a PLC (Programmable logic controller) might make things easier....