## 5 Simulation Experiment and Result Analysis
### Simulation Experiment
At this time, a step disturbance of 0.5 is added to interference channel 3 when the simulation reaches 200 s. The simulation effect is shown in Figure 11.  
When a disturbance occurs in the three channels of hot fluid flow, hot fluid inlet temperature, and refrigerant flow, the output of the control system in the simulation is 200 s, as shown in Figure 12.  
From Figure 9 to Figure 12, dynamic performance indexes of the control effect of the two control schemes when each model is matched can be obtained, and their index values are shown in Table 3.  
From Figure 9 to Figure 12, it can be seen that when interference occurs in each interference channel, the feedforward control scheme proposed in this paper can always well compensate for the influence of disturbance on the system, and the interference can be  
Figure 11: Simulation curve of system output under temperature disturbance at the refrigerant inlet. Figure 8:0 The output curve of the system is disturbed by three inputs simultaneously. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Item** & **Rise Time (s)** & **Adjustment Time (s)** & **Overshoot (\%)** \\ \hline PID-PID & 26.30 & 105.40 & 26.90 \\ IPFC-PID & 36.00 & 54.60 & 4.60 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Dynamic performance index. suppressed in advance by feedforward control before the deviation of heat exchanger outlet temperature is caused. At the same time, when the input of three kinds of heat exchangers is disturbed at the same time, the control scheme responds quickly and can make the system restore stability quickly; the adjustment time is short, and the overshoot is small, showing the control scheme's better adaptive ability. Because part of the parameter calculation is omitted when calculating the feedforward controller parameters of the thermal fluid outlet temperature to the controlled object channel, the system deviation is more obvious when the thermal fluid outlet temperature is interfered with than the other two channels, but under the auxiliary control of IPFC as the main controller, the system can still be restored to stability. In addition, it can be seen from the data in Table 3 that the control effect of the IPFC controller proposed in this paper is stronger than that of the PID controller. Compared with the PID controller, the adjustment time and overshoot of the proposed control scheme are significantly reduced, and the adjustment time is shortened by 50.8 s. The overshoot is reduced by 22.3%, and the control effect is good. Interference channel model mismatch  
In the actual industrial field, the controlled object may be affected by different situations, and the situation of model mismatch occurs. To test the control ability of the scheme under the condition of model mismatch, the adjustment parameters of the master and slave controllers and the parameters of the feedforward controller remain unchanged; the parameters of the disturbance channel are changed; and the same disturbance as the model matching is added to observe the control effect. In this case, the transfer function of the main disturbance, namely the hot fluid flow to the outlet temperature channel, is: \(G_{PD1}(s)=\frac{-1.35}{107s^{2}+23s+1}e^{-5.14s}\), The transfer function of the inlet temperature of hot fluid to the outlet temperature channel is: \(G_{PD2}(s)=\frac{0.6}{40s+1}\). The transfer function of the temperature channel at the refrigerant inlet is: \(G_{PD3}(s)=\frac{0.5}{112s^{2}+27s+1}e^{-5.14s}\). When the model is mismatched, only when the hot fluid flow fluctuates, a step disturbance of 0.5 is added to interference channel 1. The simulation effect is shown in Figure 13.  
When the model is mismatched, only the temperature of the hot fluid inlet fluctuates. At this time, a 0.5 step disturbance is added to interference channel 2 when the simulation reaches 200 s, and the simulation effect is shown in Figure 14.  
Figure 13: Simulation curve of system output under thermal fluid flow disturbance with model mismatch.