Synchronization and desynchronizing control schemes for supermarket refrigeration systems

A supermarket refrigeration system is a hybrid system with switched nonlinear dynamics and discrete-valued input variables such as opening/closing of valves and start/stop of compressors. Practical and simulation studies have shown that the use of distributed hysteresis controllers to operate the valves leads to synchronization, meaning that the opening and closing actions of the valves coincide. Consequently, the compressor periodically has to work hard resulting in low efficiency, inferior control performance and a high wear on the compressor. In this paper we propose two control schemes of low complexity for desynchronizing the valve operations while improving performance. Simulation results indicate the potential increase in efficiency and reduction in wear comparing with traditional control schemes.