JPH05142390A - Water supply control device - Google Patents

Abstract

PURPOSE:To provide a water supply control device which compensates influence affected by reverse response, and is less changed in water level even in single element control at the time of low output. CONSTITUTION:Water level deviation signals 14 and vapor pressure signals 12 are inputted into a water supply control device 5, change in vapor pressure is arrested by a change rate computing element and a monitor circuit. When it is judged that fluctuation in water level is in appearance, a water supply compensating circuit 7 outputting water supply compensating signals 15, and a PI operating circuit 9 restraining the output of the PI operating circuit based on the aforesaid compensating circuit 15, are provided. By this constitution, fluctuation in water level in appearance caused by fluctuation in vapor pressure is detected, the water level of a vapor generator can thereby be stably controlled in order to restrain unnecessary change in water supply flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water supply control for controlling a water level of a steam generator to a desired value in a power plant having a steam generator, such as a nuclear power plant of an advanced converter (ATR) type. Regarding the equipment, especially the water supply flow rate
The present invention relates to a water level control method for a steam generator in a low output region where the steam flow rate is very small and it is difficult to measure the value accurately.

[0002]

2. Description of the Related Art In a power plant having a steam generator, particularly in a nuclear power plant, a water supply controller controls a water level of the steam generator to be constant, and a pressure controller controls a steam pressure to be constant. The above-mentioned water supply control is usually performed by a three-element signal of the water level, the water supply flow rate, and the steam flow rate. However, when the reactor output is low, the accuracy of the flow rate measurement is poor, so it is performed by the single-element control using only the water level signal. Generally, PI control is performed by a three-element signal or a single-element signal, but "Development of a fuzzy control system for a new conversion reactor Fugen power plant feedwater control system" (kinetic combustion technique No. 76 19
There is also an example in which fuzzy control is applied as shown in 90.12).

[0003]

In the above prior art, in the case of PI control by a single element signal, since the water supply control valve responds in an attempt to adjust the water supply flow rate after the water level of the steam generator changes, the water level changes. There is a tendency for some fluctuations to occur before the settling occurs, and for the settling time to be long.

Further, a feature of the new-type converter having a steam generator independent of the nuclear reactor is that when the steam pressure fluctuates due to fluctuations in the reactor output, the void ratio in the steam generator changes, and the apparent water level changes. There is a phenomenon that changes greatly. This response behaves in the opposite direction, for example, the apparent water level temporarily rises when the water supply flow rate should originally be increased, so the water supply control device moves the water supply control valve to reduce the water supply flow rate. However, there is a problem of so-called reverse response, such as increasing water level fluctuations.

In particular, when the reactor is started and stopped, the reactor output must be changed, and there are many factors that change the steam pressure, such as opening and closing operations of various valves, and the effect of the reverse response cannot be ignored. ..

Maintaining the water level of the steam generator at a constant level means maintaining a balance between the steam flow rate and the feed water flow rate in terms of safety in that the amount of water that is the coolant of the reactor is secured in excess of the required amount. It is also a very important function in terms of maintaining mass balance and energy balance in the reactor / steam generator, and maintaining the system in a stable state.The water supply control system is the most important control system in a nuclear power plant. Is becoming

An object of the present invention is to provide a water supply control device that compensates for the influence of the above-mentioned reverse response and has little water level fluctuation even in single element control at low output.

[0008]

In order to achieve the above object, in a conventional single element PI controller, a deviation signal between a water level signal of a steam generator and a water level set value, and a steam pressure signal of the steam generator. When the input is input and it is determined that there is an apparent water level change due to a sudden change in steam pressure, a circuit for outputting a signal for temporarily interrupting the PI calculation is added.

[0009]

When the steam pressure suddenly drops, the void rate in the steam generator temporarily increases, and the apparent water level rises.
This phenomenon is detected when the rate of change of the steam pressure signal is negatively large and the water level deviation signal is negatively large, and it is possible to prevent the fluctuation from increasing by interrupting the PI calculation for an appropriate period. .. When the steam pressure that was temporarily reduced by the function of the pressure control system returned to its original value, the steam flow rate
The water level will change according to the balance of the water supply flow rate,
The water supply control device adjusts the water supply flow rate based on the water level deviation signal.

On the contrary, when the steam pressure rises, it is detected that the rate of change of the steam pressure signal is positively large and the water level deviation signal is positively large, and the same operation as described above is performed. It is possible to suppress the fluctuation of the water level.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block configuration of water supply control having a water supply compensating circuit 7.
The case of I control is shown. That is, the water level detector 3 is installed in the steam generator 1, and the water level signal 11 detected here is detected.
Is input to the water supply control device 5. In the water supply control device 5,
The difference between the water level set value 13 and the water level signal 11 is calculated by the subtractor 6, and this water level deviation signal 14 is input to the PI calculation circuit 9. In the PI calculation circuit 9, the water level deviation signal 14
By calculating PI with, the water supply control valve opening command signal 1
Calculate 6. With the above operation, the water supply control valve 2 is controlled to keep the water level of the steam generator 1 constant. Further, by using the steam pressure signal 12 detected by the steam pressure detector 4 provided in the steam generator 1 and the water level deviation signal 14, the apparent fluctuation of the water level signal 11 due to the change of the void rate is detected, and the water supply compensation is performed. By adding the water supply compensating circuit 7 for outputting the signal 15 to the PI calculation circuit 9, the water level of the steam generator 1 is stably controlled.

Next, referring to FIGS. 2 and 3, the water supply compensation circuit 7
The operation of the PI calculation circuit 9 will be described.

First, FIG. 4 shows a behavior model of a steam generator water level in a nuclear power plant having a steam generator such as a new converter. In FIG. 4, the case where the reactor power is increased stepwise is shown as an example. When the reactor output is increased stepwise, the pressure control system operates so as to increase the steam flow rate accordingly, so the steam pressure temporarily decreases.
When the steam pressure decreases, the void rate in the steam generator increases, so the water level apparently increases. Then, the water supply control device works to reduce the water supply flow rate. However, as shown in the graph of water supply / steam flow rate in Fig. 4, originally, the water supply flow rate should be increased in accordance with the increase in the steam flow rate. The water level goes down. If the feed water flow rate is controlled simply by PI calculation without any compensation, the shaded water feed flow rate portion in the graph of water feed / steam flow rate in FIG. Since the operation is the reverse of the above, the drop in water level becomes large and it takes time to settle.

The operation of the water supply compensating circuit 7 provided to solve this problem will be described with reference to FIG. The water supply compensation circuit 7 is roughly divided into a portion (water level deviation negative monitor 71, water level deviation positive monitor 72) that detects that the water level deviation signal 11 is far from 0, and the rate of change of the steam pressure signal 12 is large from 0. The part that detects the deviation (steam pressure change rate calculator 73, pressure change rate negative monitor 74, pressure change rate positive monitor 75) and the water level deviation signal 11 are negative, and the pressure change rate is negative. At the time, or when the water level deviation signal 11 deviates to the positive side and the pressure change rate deviates to the positive side, it is composed of a portion (AND circuits 80 and 81, OR circuit 82) which outputs the water supply compensation signal 15. Taking the case of FIG. 4 as an example, the pressure change rate signal calculated by the steam pressure change rate calculator 73 initially changes negative as shown in FIG. 4, and exceeds the set value of −PR at time T _P. The output of the negative pressure change rate monitor 74 becomes "1", and the output of the flip-flop circuit 78 also becomes "1". On the other hand, the water level of the steam generator rises due to the change in the void rate, the water level deviation signal 11 exceeds the set value -LE at time T _S , and the output of the water level deviation negative monitor 71 becomes "1". As a result, the water supply compensation signal 15 becomes "1", and the decrease of the water supply flow rate is prevented.

In the case of FIG. 4, the timing for resetting the water supply compensation signal 15 is the water level deviation signal 11
Is the time T _E at which the value becomes equal to or greater than the set value −LE, but when the fluctuation of the water level is not due to the change of the void ratio but due to the disruption of the mass balance of the water supply / steam flow rate, the water level deviation signal 11 is Since it may take time to return to the set value -LE or more, it is detected by the small pressure change rate monitor 76 that the steam pressure change rate signal has become a small value near 0, and the time delay pickup circuit 77 is detected. By resetting the flip-flop circuit 78 after a lapse of a certain period of time, the period during which the reduction of the water supply flow rate is limited can be limited, and the control is prevented from becoming uncontrollable.

The case of FIG. 4 deals with the case where the water level temporarily rises, but when the steam pressure rises and the water level temporarily drops, the water level deviation positive monitor 72 and the steam pressure change rate positive monitor are also shown. 75, the flip-flop circuit 79 operates in the same manner as described above, and the water supply compensation signal 15 is output.

Finally, FIG. 3 shows a circuit for limiting the decrease (increase) of the feed water flow rate. In the PI calculation circuit 9, the water level deviation signal 14 is normally input to the PI calculator 91, and the output thereof is output as the water supply control valve opening command signal 16, but when the water supply compensation signal 15 is "1". In this case, by outputting the output of the analog memory circuit 92 as the water supply control valve opening command signal 16, the output of the PI calculator 91 immediately before the water supply compensation signal 15 becomes "1" is held.

FIG. 5 shows another embodiment of the PI calculation circuit 9. In the circuit of FIG. 5, the calculation of the PI calculator 91 is not interrupted, but a bias is temporarily applied to the input signal (water level deviation signal 14) of the PI calculator 91 to obtain the water supply control valve opening command signal. The reverse operation of 16 is prevented. That is, when the water supply increase compensation signal 80a is "1", the adder 96 adds the positive compensation signal from the signal generator 94 to the water level deviation signal 14a.
In addition, or the water supply reduction compensation signal 81a
Is “1”, the negative compensating signal of the signal generator 95 is added to cause the apparent water level fluctuation to the PI calculator 91.
Can be prevented from being typed into.

According to the present embodiment, it is possible to detect an apparent fluctuation in the water level caused by a change in the void rate due to a fluctuation in the vapor pressure, and suppress an unnecessary fluctuation in the feed water flow rate.

[0021]

According to the present invention, the apparent water level fluctuation caused by the change in the void rate in the steam generator due to the fluctuation of the steam pressure is detected, and the supply water flow rate is controlled in the opposite direction from the apparent water level fluctuation. Since the desired movement can be suppressed, the water level can be stably maintained even in the single element PI control.

[Brief description of drawings]

FIG. 1 is a block diagram of a water supply control device.

FIG. 2 is a block diagram of a water supply compensation circuit.

FIG. 3 is a block diagram of a PI calculation circuit.

FIG. 4 is a diagram illustrating the behavior of the steam generator water level.

FIG. 5 is a diagram showing another embodiment of the PI calculation circuit.

[Explanation of Codes] 1 ... Steam generator, 2 ... Water supply control valve, 3 ... Water level detector, 4
... Steam pressure detector, 5 ... Water supply control device, 6 ... Subtractor, 7
... water supply compensation circuit, 9 ... PI operation circuit, 11 ... water level signal,
12 ... Steam pressure signal, 13 ... Water level set value, 14 ... Water level deviation signal, 15 ... Water supply compensation signal, 16 ... Water supply control valve opening command signal, 71 ... Water level deviation negative monitor, 72 ... Water level deviation positive monitor, 73 ... Steam pressure change rate calculator, 74 ... Pressure change rate negative monitor, 75 ... Pressure change rate positive monitor, 76 ... Pressure change rate small monitor, 77 ... Time delay pickup circuit,
78, 79 ... Flip-flop circuit, 80, 81 ... AN
D circuit, 80a ... Water supply increase compensation signal, 81a ... Water supply decrease compensation signal, 82 ... OR circuit, 91 ... PI calculator, 92 ... Analog memory circuit, 93 ... Signal switcher, 94, 95 ... Signal generator, 96 ... Adder.

Claims (1)

[Claims] 1. A power generator having a steam generator that heats water into steam, a water supply control device that controls a flow rate of feed water flowing into the steam generator, and a pressure control device that controls a flow rate of steam flowing out of the steam generator. In the plant, the water supply is characterized by controlling the water level of the steam generator to a desired value by temporarily changing the water level set point of the water supply control device based on the steam pressure signal of the steam generator. Control device.