Performance map control of centrifugal pumps

An Organic Rankine Cycle (ORC) system comprising:

• a pump for pumping a working medium to a heat exchanger of the ORC system, the heat exchanger evaporating the working medium, and
• a device for controlling the pump during pumping of the working medium the device comprising:
• a first pressure meter for measuring a condensation pressure of the working medium upstream of the pump at a location between a condenser of the ORC system and the pump;
• a second pressure meter for measuring a live steam pressure of the working medium downstream of the pump at a location between the heat exchanger and an expander of the ORC system;
• and
• a control unit for fixing a setpoint value of a flow rate of the pump;
• for determining a setpoint value of a rotational speed of the pump from an inverted pump performance map stored in a memory, the inverted performance map of the pump being a relation between a differential pressure across the pump and a rotational speed of the pump for a particular flow rate of the pump, wherein the fixed setpoint value of the flow rate and a difference between the a live steam pressure and the condensation pressure are incorporated into the inverted performance map as input values;
• and for setting the flow rate of the pump to the setpoint value of the flow rate,
• wherein an influence of fluctuations of the difference between the live steam pressure and the condensation pressure on the flow rate is compensated by determining the setpoint value of the rotational speed of the pump and setting the rotational speed of the pump to the setpoint value, thereby stabilizing process parameters including at least one selected from the group consisting of (i) the live steam pressure, and (ii) a live steam temperature.