Control Structure Selection for Vapor Compression Refrigeration Cycle - Intelligent Computing for Sustainable Energy and Environment - page 483

Fig. 2. The disturbance. It shows the changes of actual external environment temper-
ature during 24 hours from 2 pm to 2 pm of the next day in Singapore
Fig. 3. The superheat of evaporator. It shows the superheat outputs of the three con-
trollers due to the change in the disturbance.
In the three MPC controllers, weights of 1 are placed on the evaporator pressure
and superheat, and rate weights of 0.1 and 0.01 are placed on rpm and expan-
sion valve, respectively. Moreover, rate weights of 0.001 are placed on the ˙ m c−ai
in 3I3O MPC controller, and rate weights of 0.01 are placed on the ˙ m c−ai and
˙ m e−ai in 4I4O MPC controller. A control interval of 1 seconds are used, with
a control horizon of 15 intervals and a prediction horizon of 50 intervals. The
results for disturbance rejection for different model control structures are shown
in figure 3 and figure 4.
Figure 3 and 4 show the comparison of superheat and evaporator pressure
among the three controllers, where the 3I3O controller has better performance in