Feedforward control of capacity and superheat for a variable speed refrigeration system

This paper deals with an independent control method for the refrigeration system based on general PI control law. In the variable speed refrigeration system (VSRS), the capacity and superheat are respectively controlled by inverters and electronic expansion valves for saving energy and improving performance as well. At first, the decoupling model has been proposed to eliminate the interfering loops, and then the transfer functions are obtained from numbers of experimental tests. Once the new PI controller is designed, the system performance is evaluated by numerical simulations as well as extensive experimental works. Finally, it is found that the independent control scheme can guarantee not only precise control performance but also high COP for the VSRS.