Design of Reference Control System

The analyses in the previous section show that the Super FR qualitatively has the same basic plant dynamics as the Super LWR although the change in the main steam temperature is larger. Thus, the same plant control system as that of the Super LWR is designed and tuned here as the basis of improvements. 

The gain AT in the pressure control system, described as (4.9) and (4.10), is tuned as 0.396 so that the overshoot is minimized against the 1 % stepwise increase in the pressure setpoint. The main steam temperature is controlled by regulating the feedwater flow rate. The equation for the feedwater controller is written again because it is the basis for the improvement in the next section. 

The rate of change in m is limited to 20%/s. The proportional gain and the integral gain are determined as 13.5 and 0.0, respectively, so that the overshoot is minimized against the stepwise increase in setpoint of the main steam temperature by 4°C. 

The reactor power is controlled by the CRs. The speed of the CRs is in proportion to the deviation of the reactor power from the setpoint when the deviation is below a certain value b. When the deviation is larger than b, the CRs keep the maximum speed 1.9 cm/s this is the same as for PWRs. The value of b is determined as 0.7 so that the settling time and the undershoots of both the reactor power and main steam temperature are reasonable against the 5% stepwise decrease in the setpoint of the reactor power. 

In order to clarify the characteristics of the reference control system, the plant dynamics is analyzed with the designed control system against the 10% stepwise decrease in the setpoint of the reactor power. The results are shown in Fig. 7.71 [31]. The pressure control system and the power control system work well. However, the change in the main steam temperature is still considerable. 

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