De-Synchronization Control Of The Supermarket Refrigeration System

In recent years, the energy-saving technologies are advocated, and how to improve the utilization rate of the equipment, and prolong the service life of the equipment has become an important issue. The supermarket refrigeration system has undertaken most tasks in the multiple cold chain retail terminals. The supermarket refrigeration system is mainly composed of the compressor rack, the condenser unit and multiple independent display cases. The temperature in the display case is typically maintained by the hysteresis controller. Practice has shown that the temperature change in each display case tends to coincident easily which leads to the suction pressure oscillating in a wide range and causes the valves and compressors switching frequently. That is so-called the synchronization phenomenon. The synchronization phenomenon increases the system energy consumption increase, and adds more wear on the compressor rack, and thus reduces the compressors’ service life. Therefore, on the basis of ensuring the storage foods’ quality, solving the system synchronization problem is meaningful to improve the energy efficiency and prolong the service life of the refrigeration system. Main contents of the paper are described as follows:Firstly, the paper describes the refrigeration principle of the general refrigeration system. And mathematical models are built to describe parts of the refrigeration system, such as the display cases, the evaporators etc; further, the method of establishing a refrigeration system model in the matlab/simulink environment is described. A simulation platform of supermarket refrigeration is built which includes the GUI interface, the supermarket refrigeration system and three performance indexes, which measure the storage quality, the serve life and the energy consumption of the compressors, respectively. The numbers of the display case and the compressor in the platform can be modified to meet the simulation demand. This platform can be used in the simulation of the large-scale refrigeration system.Secondly, two low complexity solutions for the de-synchronization algorithm are studied on the simulation platform, and a small refrigeration system is built to validate the change of the corresponding performance indexes whenever the system in synchronous state or de-synchronous state. The simulation proves that the work condition is better when the system runs in de-synchronization state. Further, these two methods are applied into the larger refrigeration system; the simulation result shows that they are effective to solve the synchronization problem in the large-scale refrigeration system. The result verifies the de-synchronization ability of these two methods.At last, on the basis of previous research and analysis of the dynamics of the supermarket refrigeration system, we propose that the thermal load of the surrounding air is an important factor which can influence behaviors of the system. By adopting different values in the display cases through adjusting air speeds of the air curtains, the system operates in the de-synchronization situation and achieves better storage quality and longer service life of the compressors.