The electronic expansion valve is regulated by considering the superheat at the outlet of the evaporator as the control object. However

the traditional proportion integration differentiation (PID) control strategy fails to simultaneously consider the dynamic pull-down and steady-state performance of the refrigeration system. In this study

a segmented variable-gain PID scheme involving double feedback of the superheat and compartment temperature deviation is analyzed and compared with the traditional constant-gain PID scheme with single feedback. The results of the environmental test chamber demonstrate that at a constant temperature

the variable-gain PID scheme increased the pull-down rate by 11.8%–49.3%

decreased the overshoot time by 7.1%–57.7%

and reduced the temperature fluctuation to 0.1 ℃. This method also adapted well to variable working conditions at compartment temperatures of ?40

?20

0

and 20 ℃.