Page 307 - Distributed model predictive control for plant-wide systems

Operation Optimization of Multitype Cooling Source System Based on DMPC 281

Equipments’
parameters Power price Economic
optimization
layer
Predictive Economic optimization
load
Sates and set point of very refrigerator

Dynamic
optimization
layer
MPC MPC MPC MPC MPC MPC

Ice storage
CR1 CR2 CR1 DR1 DR2 DR3
tank

Figure 13.2 Control strategy of joint cooling system

or ice-mode electric refrigerator is neglected. The virtual network is the data transmit channel
for MPC subsystems.

13.3.1 Economic Optimization Strategy
13.3.1.1 Economic Models of Conventional and Dual Operating Mode Refrigerators
Each refrigerator has two working states – on and off – so we choose the on–off state Y {0,1} to
describe the electric refrigerator working state for the dual operating mode electric refrigerator
air condition and ice-making condition.
The cooling power is described by the continuous variables. Gordon et al. [142] introduced
the physical model of the centrifugal electric refrigerator and mentioned that the coefficient of
performance (COP) of the centrifugal refrigerator can be presented by a binary function with
the temperature of the input cooling water in the electric refrigerator T and cooling power of
the electric refrigerator P , which is shown as follows:
out
P out
COP = = f(P , T) (13.1)
out
P in
where P is the power consumption of the electric refrigerator. Then, we can get the relation-
in
ship between the power consumption and the cooling power of the electric refrigerator as
P out
P = (13.2)
in
f(P , T)
out
In the real application, relation (13.2) is difficult to use as the specific algorithm to opti-
mize the fractional function. Therefore, we need a new function for the electric refrigerator.