Experimental Study on a Control Method for Air-conditioning System Integrated with Small-scale ON/OFF Controlled Chiller

Abstract

On/off controlled chiller is wildly used for small-scale air-conditioning (AC) system. For many existing systems, the chiller may be switched on and off frequently, which speeds up the wear and aging of the chiller and introduces significant disturbances on the space temperature control. This paper presents an experimental study on a control method which combines a set-point reset technique with a bilinear control technique. The set-point reset technique is adopted to reduce the on/off frequency of the chiller, and the bilinear control is used to track the space temperature set-point. The control method was realized in a building automation system (BAS) and applied to a test rig. The experimental results show that the set-point reset technique can reduce the chiller on/off frequency obviously. The bilinear control can achieve more robust space temperature control while comparing with conventional PI control. This proposed control method has the potential to be used in the existing on/off chiller integrated AC systems with the small chilled water volume. It is able to reduce the on/off frequency of the chiller efficiently and guarantee the robustness of the space temperature control simultaneously from the control role.