Decoupling Control For Sub- And Transcritical Operation Of Co2 Refrigeration Cycles

In this paper a well-established decoupling control method is used for the sub- and transcritical operation of CO2 refrigeration cycles. Three inputs can be controlled with single loop PI control. The couplings between the two remaining system in- and outputs are online characterized as first-order time delay (FOTD) elements. A demonstrated ruleset allows the transformation of the FOTD parameters from one operating point to another. This ruleset is developed based on a physical Modelica model which characterizes the nonlinear system behavior. Finally, decoupling can be achieved for every operating point with only one identification process.