Auto Disturbance Rejection Control for a Variable Speed Refrigeration System

For the problem of coupling in the variable speed refrigeration system, this paper proposes a dynamic feed forward decoupling control method Based on active disturbance rejection control (ADRC). Influence of the compressor frequency was regarded as disturbance of superheat control system, the variable speed compressor and electronic expansion valve ADRC controllers were designed. Comparison between the ADRC temperature control and traditional PI temperature control was made. Compared with PI control, the ADRC control is more stable and accurate in regulating chamber temperature although its speed is slightly slow. Simulation result shows that the overshoot of the superheat declines from 22.7% to 5.15% when the influence of the variation of the compressor frequency is compensated with decoupling ADRC control.