JP2000131480A - Reactor recirculation pump control system and its power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the tripping of an RID-ASD as much as possible and to secure the thermal soundness of a fuel even if a bus voltage fluctuates due to a transmission line fault or the like by detecting the behavior of the bus voltage and using a logic for running back the RIP-ASD according to it. SOLUTION: In normal operation, an RIP-ASD controls the speed of a RIP so that reactor output can be subjected to constant control according to a signal from a recirculation flow rate control system 14. When a transmission line 6 is disturbed and the voltage behavior of a bus line 3 occurs, a voltage change rate and the deviation and phase difference of three-phase voltages are detected, a value is outputted to an RIP-ASD speed control device 10 by a bus voltage change monitoring device 9, and switching is made from the control system 14 to the device 10 when a prescribed value or higher is judged, thus controlling the speed of the RIP. More specifically, when a voltage is equal to or more than a set value, neither run-back nor trip is generated in the RIP and an output frequency is reduced to continue operation. When a voltage is equal to or less than the set value and a deviation difference and a phase difference are judged to be within the set value, a signal is outputted from the device 10, the control system is switched, the RIP starts run-back, and a reactor flow rate is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a boiling water nuclear power plant having a plurality of pumps (RIPs) with a built-in pressure vessel, and controlling the rotation speed of the pumps by a static variable frequency power supply (RIP). -ASD), which relates to a method of controlling a pump rotation speed of a plant.

[0002]

2. Description of the Related Art FIG. 2 shows a coolant recirculation pump of a current improved boiling water nuclear power plant and its power supply configuration.

An improved boiling water nuclear power plant (AB)
WR), by controlling the pump rotation speed of an internal pump (RIP) 1 built in the pressure vessel 5,
Reactor power is changed by changing the core flow rate. This 10
The number of rotations of the pumps of the RIPs 1a to 1j is determined by the static variable frequency power supply (RIP-ASD) 2 provided for each pump.
a to 2j. This RIP-ASD 2a-2j
Are 2a and 2b for the bus 3a in the power plant,
2b to 2e are connected to b, 2f and 2g are connected to the bus 3c, and 2i and 2j are connected to the bus 3d.

[0004] In the event that the power of the bus 3 is lost in a state where only the power supply equipment is used, for example, when a lightning strike occurs on the transmission line 6a, the circuit breaker 8a closer to the power plant than the transmission line 6a is connected. When the plant is opened and operation continues,
During the time when a is open, the voltage of the transmission line 6 and the bus 3 temporarily drops to almost zero. On this occasion,
The RIP1 has a short rotation speed half time at the time of power loss, and the RIP-ASD2 also has zero electric inertia. Therefore, the core flow rate decreases sharply, and the reactor output also decreases sharply. As a result, the fuel loaded in the core 4 becomes thermally severe.

[0005] In the ABWR, in order to prevent the above-described accident on the transmission line 6 from affecting the fuel loaded in the core 4, the RIP-AS connected to the busbars 3b and 3d is used.
For D2, MG sets 7a and 7b are provided upstream of RIP-ASD2. As a result, even in the case of a lightning strike as described above, the RIP 1a, 1
Although the pump speeds of b, 1f and 1g decrease sharply,
The rotation speeds of the other six pumps having the MG set 7 can be secured for a certain time or more due to the mechanical inertia of the MG set 7. As a result, the decrease in the core flow rate can be reduced, and the thermal effect on the fuel can be reduced.

[0006] RIP-A connected to MG set 7
FIG. 3 shows a control method for the voltage fluctuation of the transmission line 6 and the behavior of the bus 3 voltage for SD2.

Normally, the voltage of the bus 3 and the RIP-ASD
2 have the same value. RIP-ASD
2 is a device that controls the ratio of voltage and frequency to be constant, but the RIP can continue normal operation even when the bus voltage drops due to starting of auxiliary equipment during normal operation of the plant. As shown, bus 3 assumed during normal operation
Up to the voltage drop A%, the RIP-ASD 2 has a control method in which the voltage is kept constant and the operation can be performed without lowering the frequency (speed). On the other hand, the voltage of the bus 3 is A%
Below, the voltage difference (frequency difference) with RIP-ASD2
If the frequency further increases, maintaining the frequency requested by the control system causes the current to become an overcurrent and cause RIP-A
SD2 may trip overcurrent.

Therefore, from the viewpoint of giving priority to the continuation of operation, control is performed so that the output voltage (frequency) of the RIP-ASD 2 automatically follows the voltage drop of the bus 3 to continue the operation.
Furthermore, when the bus voltage decreases to a voltage B% (a voltage at which the RIP-ASD2 cannot be protected due to an overcurrent) that cannot be continued, the protection of the RIP-ASD2 device is prioritized. , RIP-ASD2 is temporarily stopped.

Therefore, if some kind of accident occurs in the transmission line 6a and, during this time, an event such as the voltage of the bus 3 gradually decreases as shown in FIG. RIP-ASD2 belonging to the buses 3a and 3c that do not
As shown in FIG. 3 (b), the four RIP-ASDs 2a, 2b, 2f, 2g trip once and connect to the trip setting value B% as the voltages of the buses 3a, 3c decrease. The rotation speeds of the RIPs 1a, 1b, 1f, 1g decrease. Thereafter, when the voltage of the bus 3 returns to B% or more, the pump speed is maintained at the current speed.

On the other hand, RIP-ASDs 2c, 2 belonging to buses 3b, 3d having MG sets 7a, 7c
d, 2e, 2h, 2i, 2j are the MG sets 7a, 7b
Due to the mechanical inertia described above, as shown in FIG. 3 (c), there is a time margin for the voltage to drop to the trip set value B%, and during that time, the RIP1 can continue operation without speed fluctuation. Due to the mechanical inertia of the MG set, as shown in FIG. 3D, the power supply of the RIP-ASD2 is kept constant during the period from t2 to t3, and then gradually decreases over the period from t3 to t4. When the power supply of the RIP-ASD2 reaches B%, the RIP-ASD trips, and the rotation speed of the RIP1 decreases rapidly.

However, as described above, in this power supply, the effect of the rapid decrease in the flow rate is small, and the thermal integrity of the fuel is not impaired.

In the power supply configuration shown in FIG.
As one of rationalization plans for R, a power supply configuration shown in FIG. 4 is being studied. In other words, the design of the RIP1 was slightly reviewed from the current level, and the pump rotation speed half-time at the time of power loss was increased by about three times as much as the current value to mitigate the sudden decrease in core flow rate at the time of power loss. This is a configuration in which the MG set, which secures inertia to mitigate the sudden decrease in flow rate, is deleted.
In the case of this method, two MG sets can be deleted, and it can be said that the effect of equipment rationalization is great.

However, when the bus voltage fluctuates, the RIP-ASD
When the control method is the same as that of FIG.
Considering the voltage fluctuation at the point of time, when the RIP inertia is about three times as large as that of the current RIP and the MG set, the reduction of the core flow rate is faster and the effect on the fuel thermal integrity Is big.

That is, in the case of the power supply configuration shown in FIG. 4, when the bus voltage fluctuates, FIG.
As shown in the figure, since 10 RIP-ASD2s trip at the same time and 10 RIP1s stop at the same time, the core flow rate changes abruptly, and the cooling capacity of the reactor sharply decreases. Can be large.

As described above, the event that all the RIPs trip at the same time due to the fluctuation of the system voltage without the generator trip or the turbine trip is caused by the MG.
This is an inevitable problem in a nuclear power plant having a power supply configuration with the set deleted, and some countermeasures are required.

In order to reduce the effect of the rapid decrease in the flow rate, R
If the inertia of IP1 is greatly increased, the axial length of RIP is increased, and the advantage of equipment rationalization by deleting the MG set is lost. Therefore, it is necessary to consider a method for alleviating the thermal effect on the fuel caused by the system fluctuation, which is a problem of the present power supply configuration, without having to make a significant change in the equipment.

Therefore, a method was devised in which the influence of the sudden decrease in the core flow rate was reduced by changing the control method of the RIP-ASD.

[0018]

SUMMARY OF THE INVENTION The object of the present invention is as shown in FIG.
In the power supply configuration in which the MG set is deleted and the RIP having a larger moment of inertia than the current RIP is combined as shown in, the trip of the RIP-ASD is avoided as much as possible even when the bus voltage fluctuates due to a transmission line accident or the like, and the fuel It is an object of the present invention to provide a reactor recirculation pump power supply device that ensures the thermal integrity of a reactor.

[0019]

In the current control method shown in FIGS. 3A to 3E, the logic is to trip the RIP-ASD when the bus voltage falls below a certain value. This is because the current flowing through the RIP-ASD increases in order to maintain the power required to keep the RIP operating. In the present invention, by detecting the behavior of the bus voltage,
By using the logic to run back the RIP-ASD accordingly, the power required for the RIP-ASD can be reduced, and the RIP-ASD can be prevented from tripping for the purpose of equipment protection.

FIG. 5 shows the change in the bus voltage and R
4 shows a change in IP-ASD voltage. As shown in FIG. 5A, when the bus voltage changes at a change rate α% / sec, the change rate is detected, and the control voltage of the RIP-ASD is changed at a larger change rate b1% / sec. Run back (Fig. 5
(b)). As a result, the rotation speed of the RIP decreases, and the RIP
By reducing the power required for the operation, it becomes possible to avoid a trip of the RIP-ASD for the purpose of protecting the equipment (FIG. 5 (c)). If the change rate b1 is a value larger than α, the control voltage of the RIP-ASD can be covered by the bus voltage.

In this method, the bus voltage is RIP-A
When the value falls below the SD trip set value, the RIP is tripped. However, when the trip is performed after the runback, the change width of the core flow rapid decrease due to the trip is smaller than the trip by the normal control method, and the fuel heat is reduced. It is possible to secure sufficient soundness.

As a result, it is possible to avoid as much as possible a trip of all RIP units due to system fluctuation, which is a problem of a nuclear power plant having a power supply configuration in which the MG set is deleted.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. FIG. 6 is a configuration diagram of a recirculation flow pump control device according to one embodiment of the present invention. 6, 1 is a reactor recirculation pump (RIP), 2 is a RIP variable frequency power supply (RIP-ASD), 3 is an in-house power bus, 4 is a reactor core, 5 is a reactor pressure vessel, and 6 is a pump. An electric wire, 9 is a bus voltage change monitoring device, 10 is a RIP-ASD runback control device, and 14 is a recirculation flow control system.

Hereinafter, behaviors of the recirculation control system and the RIP-ASD in this embodiment will be described. During normal operation of the plant, the RIP-ASD 2 controls the RIP according to a signal from the recirculation flow control system 14 so that the reactor output is controlled to be constant.
1 is controlled. However, when some disturbance occurs in the power transmission line 6 and an event such that the voltage of the bus 3 fluctuates occurs, the bus voltage, the rate of change of the bus voltage, and the bus voltage are monitored by the bus voltage change monitoring device 9. The phase difference and the phase difference are detected, and the respective values are output to the RIP-ASD speed controller 10. The RIP-ASD speed controller 10 switches the control of the RIP-ASD 2 from the recirculation control system 14 to the RIP-ASD speed controller 10 when determining that each signal is equal to or greater than a predetermined specified value. After that, the RIP-ASD speed controller 10 controls the rotation speed of the RIP 1 based on the following logic.

FIG. 1 shows an example of the control logic incorporated in the RIP-ASD speed controller 10 according to the present invention. When a change occurs in the bus voltage, a change signal of the bus voltage is received from the bus voltage change monitoring device 9, and when the bus voltage is equal to or more than a predetermined set value a1, runback and trip do not occur in the RIP 1, To continue driving,
The output frequency is reduced to such an extent that an overcurrent trip does not occur, and the rotation speed of the RIP 1 is changed following the change in the output frequency. The run-back mode determination circuit 11 does not output a control system switching signal, and the RIP is connected to the recirculation flow control system 14.
Controlled by a signal from

The bus voltage is equal to or less than a predetermined set value a1, the change rate of the bus voltage is equal to or less than a predetermined change rate set value b1, and the deviation and phase difference of the three-phase voltage of the bus voltage are specified. When it is determined that the value is within the value c1, a control system switching signal is output from the runback mode determination circuit 11 of the RIP-ASD speed control device 10, and the RIP
-Switch the control of ASD2 to a signal by the RIP runback operation instruction circuit. Further, the run-back mode determination circuit 11 outputs an operation command signal to the RIP run-back operation instruction circuit 12. As a result, the RIP run-back operation instruction circuit 12 issues a command to the RIP-ASD 2 to cause the RIP 1 to run back at a speed change rate b1% / sec. Based on this, RIP1 starts runback, and the core flow rate decreases.

Here, a1, b1, c1 and α are values specific to each plant, which are determined in terms of the safety design of the core and the performance of the ASD. In each plant, the specified value of the thermal safety of the core, the set value for equipment protection of the RIP-ASD2, and the required runback rate are different, so an arbitrary set value is determined in advance by a necessary prediction analysis.

Thereafter, the bus voltage change monitoring device 9
When the bus voltage is continuously measured, and it is determined that the bus voltage is equal to or more than the preset set value a2, RIP-ASD2
Keeps the run-back of the RIP until the system voltage fluctuates and becomes more than a1, and keeps the rotation speed of the RIP at a constant value after becoming more than a1. After that, the RIP rotation speed is maintained until the bus voltage becomes a1 or less again, and the RIP1 rotation speed is controlled until the system variation converges.

The bus voltage is monitored by the bus voltage change monitoring device 9. If it is determined that the change rate of the bus voltage is sufficiently small and the system fluctuation has converged, the control of the RIP-ASD 2 is performed by the recirculation flow control system 14. Switch to signal control.

When it is determined that the bus voltage has become equal to or less than the preset set value a2, the runback mode determination circuit 11 of the RIP-ASD speed controller 10 sends an operation command signal to the RIP trip operation instruction device 13. Is output. Based on this, from the viewpoint of equipment protection against overcurrent, the RIP trip operation instruction circuit 13 sends the RIP-ASD2
To the RIP-ASD2.

When it is determined that the rate of change of the bus voltage is equal to or higher than the preset change rate set value b1, it is determined that the bus voltage is instantaneously lost, and it is determined that control of the RIP1 is impossible. , An operation command signal is output from the runback mode determination circuit 11 of the RIP-ASD speed control device 10 to the RIP trip operation instruction device 13. Based on this, the RIP trip operation instruction circuit 13 sends the RIP-AS
A trip operation command signal is output to D2 and RIP-ASD
Trip 2

If the deviation and the phase difference of the three-layer voltage of the bus are determined to be equal to or more than the specified value c1, it is determined that the control of the RIP1 is impossible, and the run-back mode determination circuit of the RIP-ASD speed controller 10 is executed. 11 outputs an operation command signal to the RIP trip operation instruction device 13. Based on this, the RIP trip operation instructing circuit 13 sends the RIP-
A trip operation command signal is output to ASD2 and RIP-A
Trip SD2.

If the rotation speed of the RIP1 is equal to or less than the predetermined controllable minimum rotation speed e1, the RIP-AS
An operation command signal is output from the runback mode determination circuit 11 of the D speed control device 10 to the RIP trip operation instruction device 13. Based on this, a trip operation command signal is output to the RIP-ASD2, and the RIP-ASD2 is tripped.

By using the RIP-ASD control logic, it is possible to control the RIP by using the system voltage which has not been used in the conventional logic, thereby minimizing all RIP trips when the system oscillates. Things become possible.

In addition, in the event of a momentary power failure or a long-time power failure in the power transmission system due to the safety design of the core and the performance of the ASD, it is necessary to control the rotational speed of the RIP using the above-mentioned runback rate. In a certain plant, a battery is connected to an arbitrary number of RIP-ASD2s,
It is conceivable to secure a power supply necessary for controlling the IP-ASD2.

A battery is connected to a predetermined number of RIP-ASDs 2, and the power from the bus is charged during normal operation.

When a system fluctuation or a power failure occurs and the bus voltage decreases rapidly, the change is detected by the bus voltage change monitoring device 9 and the RIP-ASD2 is detected by the switching signal.
Is switched from the bus to the battery 15. afterwards,
According to the change in the bus voltage detected by the bus voltage change monitoring device 9, the RIP-
The control of ASD2 is performed from the recirculation flow control system 14 to RIP-A.
Switch to SD speed control device 10. From the runback mode determination circuit 11 of the RIP-ASD speed controller 10,
An operation command signal is output to the RIP run-back operation instruction device 12 or the RIP trip operation instruction device 13.
Based on this, a runback operation command signal or a trip operation command signal is output to the RIP-ASD2, and the RIP-A
SD2 is run back or tripped according to a predetermined run back rate. Thereafter, when the battery voltage falls below the set value a2, in order to protect the device,
An operation command signal is output from the runback mode determination circuit 11 of the RIP-ASD speed control device 10 to the RIP trip operation instruction device 13. Based on that, RIP-
A trip operation command signal is output to ASD2 and RIP-A
Trip SD2.

When the rotation speed of the RIP 1 is equal to or less than the predetermined minimum rotation speed e 1, the run-back mode determination circuit 11 of the RIP-ASD speed controller 10 determines
An operation command signal is output to the RIP trip operation instruction device 13. Based on this, a trip operation command signal is output to the RIP-ASD2, and the RIP-ASD2 is tripped.

By using this method, even if the bus voltage is instantaneously lost, it is possible to prevent a sharp decrease in the core flow rate and to reduce the thermal effect on the fuel by controlling the rotation speed of the RIP1. Becomes

[0040]

As described above, in a nuclear power plant having a power supply configuration in which the MG set is removed and a RIP having a larger moment of inertia than the current RIP is combined as a reactor recirculation pump as described above, an accident in the power transmission system Even when the bus voltage fluctuation occurs, the trip of the RIP-ASD can be avoided as much as possible by using the voltage of the bus which has not been used conventionally, and the thermal integrity of the fuel can be secured.

[Brief description of the drawings]

FIG. 1 is a logic diagram of RIP-ASD runback when an event such as a fluctuation in bus power occurs.

FIG. 2 is a power supply configuration diagram of a nuclear power plant having an MG set as a reactor recirculation pump power supply configuration.

3 (a) to 3 (e) show RIP-ASD voltage changes and RIPs when a bus power supply changes in a nuclear power plant having an MG set as a reactor recirculation pump power supply configuration.
FIG. 4 is a characteristic diagram comparing a change in rotation speed.

FIG. 4 shows the current R configuration as the reactor recirculation pump power supply configuration.
The power supply block diagram of the nuclear power plant from which the MG set was deleted using RIP with a large inertia compared with IP.

FIGS. 5A to 5C show RIP- according to the present invention.
FIG. 11 is a characteristic diagram comparing a change in RIP-ASD voltage and a change in RIP rotation speed when a bus power supply changes in a nuclear power plant from which an MG set has been deleted when the ASD runback logic is adopted.

FIG. 6 is a power supply configuration diagram showing an example of a reactor recirculation pump power supply configuration according to the present invention.

FIG. 7 is a block diagram showing an example of a configuration diagram of a RIP-ASD control system according to the present invention.

FIG. 8 is a power supply configuration diagram showing an example of a power supply configuration of a reactor recirculation pump with a battery according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reactor recirculation pump (RIP), 2 ... Static variable frequency power supply (RIP-ASD), 3 ... Bus, 4 ... Reactor core, 5 ... Reactor pressure vessel, 6 ... Transmission line, 7 ... MG Set, 8 ... Circuit breaker, 9: Bus voltage change monitoring device, 10 ...
RIP-ASD runback control device, 11: runback mode determination device, 12: RIP runback operation instruction circuit, 13: RIP trip operation instruction circuit, 14: recirculation flow control system, 15: battery.

Claims (7)

[Claims] An MG power supply for a recirculation pump for a nuclear reactor.
A reactor recirculation pump control method that controls the speed of the reactor recirculation pump to an arbitrary value when the bus voltage drops in a nuclear power plant that has a power supply unit with the set removed. 2. The reactor recirculation pump according to claim 1, wherein the in-plant bus voltage and the rate of change of the bus voltage are monitored, and when the voltage and the rate of change of the voltage become specified values, the reactor recirculation pump is controlled in accordance with the rate of change. Reactor recirculation pump control system characterized by reducing the speed at a specified value. 3. The reactor recirculation pump control system according to claim 1, wherein the in-plant bus voltage is monitored, and when the voltage reaches a specified value, the reactor recirculation pump is stopped. 4. A power supply device for a recirculation pump for a reactor, comprising:
A reactor recirculation pump power supply device, comprising a control unit for controlling the speed of a reactor recirculation pump to an arbitrary value when a bus voltage drops, in a nuclear power plant having a power supply device with a set removed. 5. An apparatus according to claim 4, further comprising means for monitoring a local voltage bus voltage and a time change of the bus voltage, wherein when the voltage and the voltage change rate become a specified value, the atomic voltage is changed according to the change rate. A reactor recirculation pump power supply device having a function of reducing the speed of a reactor recirculation pump by a prescribed value. 6. A reactor recirculation system according to claim 4, further comprising means for monitoring the bus voltage in the plant, and having a function of stopping the reactor recirculation pump when the voltage becomes a specified value. Circulation pump power supply. 7. The reactor recirculation pump according to claim 4, further comprising an energy storage device as an auxiliary power supply for the reactor recirculation pump, wherein the reactor recirculation pump is connected to the storage device when the in-plant bus voltage and the rate of change thereof become specified values. A reactor recirculation pump power supply device having a function of reducing the speed of a reactor recirculation pump by a specified value by a power supply from the reactor.