A switching control strategy for vapor compression refrigeration systems

A novel switching control strategy for small-capacity (<1 kW) vapor compression refrigerators is put forward aiming at keeping the system running continuously at the desired setpoint condition by acting concurrently on the compressor speed and expansion valve opening. The controller was designed based on switching control rules obtained from a multiple Lyapunov function approach that guarantees an asymptotic convergence of the system states to a desired steady-state condition. Tailored experiments for system identification and controller evaluation (e.g., reference tracking, disturbance rejection, energy performance) were carried out using a purpose-built refrigeration facility. The switching controller has shown to be able to drive the system toward the reference rapidly, and also to reject the imposed disturbances satisfactorily. Energy performance comparisons considering the proposed controller and a classical dual-SISO approach are also reported and discussed.