JPH0648082B2 - Reactor water supply controller - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a reactor feedwater control device for controlling a feedwater pump of a reactor to keep a water level of the reactor constant.

[Technical background of the invention] Generally, in boiling water reactors, the reactor standard water level necessary for stable operation of the reactor is defined, and in any operating state of the reactor, this reactor standard water level is set. The deviation of the reactor water level from the water level must be within the allowable range. Should the reactor water level deviate from this allowable range, the reactor power must be reduced or the reactor must be shut down, and maintaining the reactor water level at the standard value is extremely It's important. on the other hand,
The reactor water level tends to fluctuate constantly because the steam flow rate from the reactor to the turbine changes depending on the reactor output. There must be. It is a reactor water supply control device provided for this purpose, usually, by changing the rotational speed of the reactor water supply pump, or by changing the opening of the flow rate adjustment valve provided at the outlet of the reactor water supply pump, Controls the flow rate of feed water fed into the reactor.

FIG. 4 shows an example thereof, 1 is a reactor, 22 is a water supply pump for sending water into the reactor, and 3 is a flow rate adjustment provided at the outlet of the water supply pump 2 for adjusting the water supply flow rate. Valve 4 is a water level setting device that gives a water level reference signal, 5 is a water level detector that detects the reactor water level, and 6 is a water level reference signal L ₁ from the water level setting device 4 and a water level signal L ₂ from the water level detector 5.
, A first calculator for calculating the water level deviation signal L ₃
7 is a water level controller which inputs the water level deviation signal L ₃ and calculates the flow rate command signal L ₄ , 8 is a flow rate detector which detects the flow rate of the water supply pump, 9 is a pump flow rate signal L ₅ from the flow rate detector 8 and Input the flow rate controller output signal L ₇ , select the flow rate controller output signal L ₇ when the pump flow rate is low, and select the pump flow rate signal L ₅ when the pump flow rate is not low and output the selection signal L ₈ . The switching contact, 10 receives the flow rate command signal L ₄ and the switching contact output signal L ₈ from the water level controller 7, and the flow rate deviation signal L
Second calculator for calculating a _6, 11 enter the flow rate difference signal L _6, a flow controller for driving the flow control valve 3, to calculate the flow controller output signal L _7.

FIG. 5 is a block diagram showing the operation of the above configuration,
G ₁ (S) is a transfer function representing the water level controller 7, G ₂ (S) is a transfer function representing the flow rate controller 11, G ₃ (S) is a transfer function representing the flow rate adjusting valve 3, and G ₄ (S) Is a transfer function representing the reactor 1. At this time, if the pump flow rate is not low (that is, the switching contact 9 is selecting the pump flow rate signal L ₅ ), the water level reference signal L
The transfer characteristic from ₁ (S) to the flow control deviation signal L ₆ (S) is expressed by the following equation.

Normally, the water level controller 7 is a proportional gain, and the flow rate adjustment valve 3 is a 0 type Since the reactor 1 is represented by the integrability and the flow controller 11 usually includes the integral element, Next, for the step change in L ₁ (S), by using the final value theorem Laplace transform, the steady value of L ₆ becomes _{L 6 = 0 ...... (3)} . Therefore, the flow rate command signal L ₄ and the pump flow rate signal L ₅ match, and the flow rate of the water supply pump 2 is controlled by the water level controller 7. However, when the water supply pump 2 is stopped, the flow rate signal L ₅ =
0, which does not match the flow rate command signal L ₄ , resulting in L ₆ ≠ 0 (4). That is, since the flow rate controller 11 includes the integrator, the flow rate controller 11 is saturated by the above equation (4), and the opening degree of the flow rate adjusting valve 3 is always in the fully open state.

On the other hand, in a general nuclear power plant, a plurality of water supply pumps are installed, and normal water supply control is performed using some of them (for example, two out of four). The remaining water supply pumps are for backup use and are normally stopped, but if there is a possibility that the reactor water level will deviate from the allowable range and drop sharply due to a failure of the service water supply pump, it will be automatically started. And is designed to provide water. However, as described above, when the flow rate controller 11 is saturated when the pump is stopped, the flow rate of the automatically started water supply pump is 100% or a value close to it, and the constant time until the saturation of the flow rate controller 11 is eliminated, It will flow in an uncontrolled state, and on the contrary, it will become supercharged water, and the reactor water level will rise rapidly and deviate from the allowable range.

Therefore, the switching contact 9 is provided so as not to saturate the flow rate controller 11 even when the water supply pump 2 is stopped. Transfer characteristic in the case of pump flow-low flow command signal L ₄ for switching contact 9 has selected the flow controller output signal L ₇ to flow controller output signal L ₇ is Becomes Therefore, from the final value theorem of the Laplace transform and Eq. (2), L ₇ = L ₄ (5) in the steady state, the flow controller 11 does not saturate even when the feed pump is stopped, and the flow control The device output signal L ₇ will be maintained at the same value as the flow rate command signal L ₄ .

[Problems of background art] However, this is a characteristic in a steady state,
As shown in FIG. 6, when the switching contact 9 is switched, unless the flow rate controller output signal L ₇ and the pump flow rate signal L ₅ are the same, the flow rate deviation signal L ₆ depends on whether the pump flow rate is low or low. L ₄ -L ₅ and L ₄ -L ₇ , respectively,
A bump is generated in the flow rate deviation signal L ₆ . This is the switching contact 9
This is because the flow rate controller output signal L ₇ and the pump flow rate signal L ₅ are switched by. If there is a deviation between them, the deviation is output as a variation through the flow rate controller 11, and the flow rate controller output A bump is generated on the signal L ₇ .

On the other hand, the flow rate controller output signal L ₇ and the pump flow rate signal L ₅ are
The characteristics between the opening degree / flow rate of the flow rate control adjustment valve 3 have non-linearity and therefore do not usually match. Therefore, in the conventional configuration, when switching the switching contact 9, a bump is always generated, and the flow rate of water supplied to the reactor fluctuates. As a result, the reactor water level fluctuates,
There was a risk that the deviation from the reactor standard water level would deviate from the allowable range.

[Object of the Invention] It is an object of the present invention to provide a stable reactor feedwater control device by eliminating the fluctuation of the reactor water level by switching the pump flow signal and the output of the flow controller to bumpless. .

SUMMARY OF THE INVENTION Accordingly the present invention, the first computing unit for calculating a deviation level signal L ₃ of the reference water level signal L ₁ of the reactor and the detection level signal L ₁ 6
And a water level controller 7 for calculating a command flow rate signal L ₄ for the reactor feed water pump 2 in accordance with the deviation water level signal L ₃ output from the first calculator 6, the command flow rate signal L ₄ and the feedback signal L Deviation from ₈ Second flow rate signal L ₆ is calculated
A calculator 10 and a flow controller 11 for calculating a flow control signal L ₇ for controlling the flow of the reactor feedwater pump 2 according to the deviation flow signal L ₆ output from the second calculator 10.
And when the flow rate of the reactor feedwater pump 2 is “low”, the flow rate control signal L ₇ output from the flow rate controller 11 is
When the flow rate of the reactor feed water pump 2 is “not low”, the detection flow rate signal L ₅ of the reactor feed water pump 2 is selected and is output as the feedback signal L ₈ to the second computing unit 10. In a reactor water supply control device including a third arithmetic unit 12 for calculating a deviation L ₉ between a flow control signal L ₇ output from the flow controller 11 and a detected flow signal L ₅ of the reactor feed water pump 2. And only when the reactor feedwater pump flow rate changes from "low" to "not low" or "not low" to "low".
It is characterized in that a correction circuit 14 for correcting the output L ₃ of the above-mentioned to a signal which converges to 0 after a predetermined time and adding it to the second arithmetic unit 10 is provided.

[Embodiment of the Invention] Hereinafter, the present invention will be described based on an embodiment shown in FIG. FIG. 1 is a block diagram of a reactor water supply control device showing an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 4 indicate the same or corresponding parts, and the difference from FIG. 4 is that pump flow rate signal L ₅ + flow rate controller output signal L ₇ −switching contact output signal L ₈ × 2. The point that the third arithmetic unit 12 for calculating 6) is provided, and the third arithmetic unit 12
Of the output signal L ₃ from the first delay circuit 14 via the contact 13 and the output signal L ₁₀ of the first delay circuit 14 as a correction signal to the second computing unit 10 via the contact 15. That is the point.

FIG. 2 shows the movements of the contacts 13 and 15. In the steady state, the contact 13 is closed and the contact 15 is open.
The contact 13 is open and the contact 15 is closed for a certain time (t ₁ ) from when the pump operates (that is, when the pump flow changes from "low" to "not low" or to "not low" to "low"). Becomes Therefore, in the steady state, the flow rate deviation signal L ₆ input to the flow rate controller 11 is the same as that shown in FIG. 4, and the control operation is the same. On the other hand, after the switching contact 9 has been operated for a certain time
At (t ₁ ), since the output signal L ₁₀ of the first-order lag circuit 14 is input to the second adder 10 via the contact point 15, the second-lag circuit output signal L ₁₀ is added to the flow rate deviation signal L _6. become.

FIG. 3 shows the primary delay circuit output signal L ₁₀ and the flow rate deviation signal L _10.
It is a characteristic view which shows the change of ₆ . When the pump flow rate is “low” in the steady state, L ₆ = L ₄ −L ₇ (7), and from the equation (6), L ₁₀ = L ₅ + L ₇ −L ₇ × 2 = L ₅ has become a -L ₇ ...... (8). Thus, the pump flow rate becomes "low" → "no low", immediately after the switching contact 9 is operated, the contact 15 _{closed, L 6 = L 4 -L 5} + L 10 = L 4 -L 5 + L 5 -L ₇ = L ₄ -L ₇ (9), the flow rate deviation signal L ₆ does not change and no bump occurs.

On the other hand, since the contact 13 is opened after the switching contact 9 operates, L ₁₀ gradually approaches 0 with a constant time constant (T).
Therefore, if t ₁ is made sufficiently large, the flow rate deviation signal L ₆ becomes L ₆ = L ₄ −L ₅ + L ₁₀ = L ₄ −L ₅ (10), then the contact 13 is closed and the contact 15 is closed. It is opened and becomes similar to the configuration example shown in FIG. Above is a low pump flow rate →
Although "when not low" has been described, the same operation is performed in the opposite case.

That is, when the pump flow rate is not “low”, L ₆ = L ₄ −L ₅ (11) Further, the output signal L ₁₀ of the first-order delay circuit 14 is L ₁₀ = L ₅ + L ₇ −L ₅ × 2 = L ₇ −L ₅ (12) Next, when the pump flow rate is “not low” → “low” and immediately after the switching contact 9 operates, L ₆ = L ₄ −L ₇ + L ₁₀ = L ₄ -L ₇ + L ₇ -L ₅ = L ₄ -L ₅ (13), the flow rate deviation signal L ₆ does not change and no bump occurs. After that, L ₁₀ gradually falls to 0, whereby the flow rate deviation signal L ₆ settles to L ₆ = L ₄ −L ₇ + L ₁₀ = L ₄ −L ₇ (14), and the bumpless “L ₄ from -L _5, "" L ₄ -
L ₇ ”.

By the way, although the time constant T of the first-order lag circuit 14 is set to a constant value in the embodiment described above, the larger the time constant T is, the more gradually the change of the flow rate deviation signal L ₆ is made. Therefore, it is preferable in controlling the reactor water level when the switching contact 9 is operated. However, if the time constant T is large, the above (8)
The calculation of equation (13) is also delayed, and the pump flow rate L ₅
Is fluctuating, L ₁₀ is not always L ₁₀ = L ₇ −L ₅
Alternatively, L ₁₀ = L ₅ −L ₇ will not be satisfied. Therefore, in such a case, it is not possible to completely prevent bumping when the switching contact 9 is operated. Therefore, in order to solve this problem, the time constant T of the first-order delay circuit 14 may be made variable. That is, By setting T ₁ to be small and T ₂ to be large, the above problem can be solved.

In this case, if T is changed, t ₁ must also be changed, so there is a problem that the setting change of t ₁ becomes complicated, but this is a means of confirming the first-order lag circuit output signal L ₁₀ by a comparator. Solvable. That is, | L ₁₀ | <ε (ε is a small positive value) A comparator is provided to detect that (16), and after the switching contact 9 operates, the contact 13 is opened until the comparator operates and the contact 13 is opened. 15 is closed. In this way, t
_{Since 1} is automatically determined by T, the above problem is solved.

As is clear from the description of the above embodiment, the signal L ₁₀ applied to the second arithmetic unit 10 may be a signal that gradually converges to 0. Therefore, the circuit 14 is not necessarily limited to the temporary delay circuit. , Gradually reduce the output of the lamp circuit, etc.
It is clear that any correction circuit may be used as long as it is a circuit that narrows down to.

As described above, according to the present invention, when the pump flow rate changes, the first-order lag circuit output signal is added as a correction signal to the flow rate deviation signal for a certain period of time, so feedback to the flow rate controller is performed. The pump flow rate signal and the flow rate controller output signal can be switched to bumpless, the reactor feed water flow rate does not fluctuate, and the reactor water level is controlled stably.

[Brief description of drawings]

FIG. 1 is a block diagram of a reactor water supply control device showing an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of FIG. 1, FIG. 3 is a first characteristic diagram, and FIG. 5 is a block diagram of FIG. 4 is a block diagram of FIG. 4, and FIG. 6 is a characteristic diagram of FIG. 1 ... Reactor, 2 ... Water pump, 3 ... Flow control valve,
4 ... Water level setter, 5 ... Water level detector, 6 ... First calculator, 7 ... Water level controller, 8 ... Flow rate detector, 9 ... Switching contact, 10 ... Second calculation Device, 11 ... Flow controller, 12 ...
… Third calculator, 13 …… Contact, 14 …… First-order delay circuit, 15
……contact.

Claims (1)

[Claims] 1. A first calculator for calculating a deviation water level signal between a reference water level signal and a detected water level signal of a nuclear reactor, and a command to a reactor feed water pump according to the deviation water level signal output from the first arithmetic unit. A water level controller that calculates a flow rate signal, a second calculator that calculates a deviation flow rate signal between the command flow rate signal and a feedback signal, and the reactor feedwater according to the deviation flow rate signal output from the second calculator A flow rate controller for calculating a flow rate control signal for controlling the flow rate of the pump, and a flow rate control signal output from the flow rate controller when the flow rate of the reactor feed water pump is “low”, When the flow rate is not “low”, in a reactor water supply control device including a switching circuit that selects the detected flow rate signal of the reactor water supply pump and outputs it as the feedback signal to the second computing unit, A third calculator for calculating a deviation between a flow rate control signal output from the flow rate controller and a detected flow rate signal of the reactor feedwater pump, and the reactor feedwater pump flow rate from "low" to "not low" or " An atom characterized by providing a correction circuit for correcting the output of the third arithmetic unit to a signal that converges to 0 after a predetermined time only when changing from "not low" to "low" and adding the signal to the second arithmetic unit. Reactor water supply control device.