Page 314 - Distributed model predictive control for plant-wide systems

288 Distributed Model Predictive Control for Plant-Wide Systems

Table 13.3 Dynamic parameters of refrigerators
under air conditioning operation
Electric refrigerators Time Delay
in the air-mode constant time
power (kW) (min) (min)

2150 3.0 2.5
3900 4.0 5.0
6329 5.0 7.5

simulation period, the input cooling water temperature of each electric refrigerator is stable
◦
and constant. The input cooling water temperature of air-mode electric refrigerator is 32 C,
◦
and in the ice mode it is 30 C. The maximum volume of ice storage tank is 50,000 kWh and
the lower limit is set to 5000 kWh.The time constant of first-order model for the ice storage
tank is 2 min. The average price of the ice storage is 0.0576 RMB/kWh according to the full
power of an electric refrigerator based on the valley electricity price.
First, to testify the economic effect of the upper level optimization, this chapter chooses
a normal schedule strategy as a comparison, which makes ice in the ice storage tank during
the price valley and use electric refrigerator to supply cooling during the normal price and the
peak price. The start order is the same as the size of the electric refrigerator power.
The predictive load curve and the price of two strategies are shown in Figures 13.3 and 13.4,
respectively. The total cost of the upper economic optimization strategy is 3970 Yuan in 6 h,
and the comparison is 4053 RMB. The proposed strategy saves about 2% of the total money
8000

6000

Predictive load(kW) 4000

2000

0
5:00 6:00 7:00 8:00 9:00 10:00 11:00
Time
Figure 13.3 Load forecasting curve