Abstract: A pump system using multiple reciprocating positive displacement pumps which phase shift is controlled by a phase shift controller. The phase shift controller uses a virtual master pump inside the phase shift controller which is used as a phase reference against which the phase shifts of the individual pumps is calculated. The phase shift controller adjusts the speed reference set-point for the variable speed drives of the individual pumps such that a desired phase shift is obtained and maintained. The operation of multiple reciprocating pumps using phase shift control can significantly reduce the pressure pulsation levels in the pump system. The use of a virtual master pump eliminates master slave scheduling and increases system reliability and availability as the operating of the phase control is not depending on the reliability of a real master pump.