JP4435056B2 - Power supply device for recirculation pump and control method thereof - Google Patents

Description

  The present invention relates to a power supply device for an electric motor that drives a recirculation pump that recirculates a reactor coolant of a boiling water reactor and a control method thereof, and more particularly, to a variable voltage variable frequency power supply device and a control method thereof.

  In a general boiling water reactor, the reactor output is controlled by changing the circulation amount of the coolant in the reactor pressure vessel by the reactor coolant recirculation system. The reactor coolant recirculation system includes a recirculation pump, a recirculation pump drive power supply device, a recirculation flow rate control device, and the like.

  The recirculation pump is connected to the reactor pressure vessel via a loop pipe. The speed of the recirculation pump is controlled by controlling the electric motor by increasing / decreasing the output of the recirculation pump drive power supply apparatus according to the speed request signal transmitted from the recirculation flow rate control apparatus. Thereby, the circulation amount of the coolant in the reactor pressure vessel is changed, and the reactor output is controlled.

  One method for controlling the rotational speed of the recirculation pump is to use a variable voltage variable frequency power supply device as a drive power supply device for the recirculation pump and control the power supply voltage and the power supply frequency.

  A conventional variable voltage variable frequency power supply device for a recirculation pump includes a semiconductor power conversion circuit and a speed control device. The semiconductor power conversion circuit includes a semiconductor power forward conversion circuit that converts three-phase alternating current received from the in-house power supply system into direct current, and a semiconductor power reverse conversion circuit that converts direct current into alternating current having an arbitrary frequency.

  Then, according to the speed request signal from the recirculation flow rate control device, control is performed so that the ratio between the output voltage and the output frequency of the semiconductor power inverse conversion circuit becomes constant. Thereby, the variable speed control of the electric motor that drives the recirculation pump is performed, and the speed control of the recirculation pump is performed. The operation of the recirculation pump and the motor is linked.

  In the variable voltage variable frequency power supply device, it is considered that an overcurrent is generated in the semiconductor power conversion circuit when a semiconductor element constituting the semiconductor power conversion circuit is in a short circuit state due to a single failure. At this time, when the speed control device detects a semiconductor element failure signal indicating the occurrence of overcurrent, the speed control device stops the semiconductor element control signal for the semiconductor power conversion circuit and stops the variable voltage variable frequency power supply device. Therefore, the recirculation pump is stopped. As a result, other elements and the motor are protected.

  In addition, when performing maintenance inspection on the semiconductor power conversion circuit, it is necessary to stop the variable voltage variable frequency power supply device because maintenance inspection cannot be performed in a state where a voltage is applied to the semiconductor power conversion circuit. Therefore, the recirculation pump is also stopped when performing maintenance and inspection of the semiconductor power conversion circuit.

The above reactor coolant recirculation system usually consists of two systems, each having a recirculation pump. Even if one of the recirculation pumps is stopped due to the stoppage of the motor for driving the recirculation pump due to a single failure of the semiconductor element of the variable voltage variable frequency power supply device or maintenance of the semiconductor power conversion circuit, the remaining One unit will continue to operate. Thereby, the coolant circulation amount may be reduced depending on conditions, but the coolant in the reactor pressure vessel can be circulated.
US Pat. No. 5,625,545

  However, when one recirculation pump is stopped, the coolant circulation in the loop pipe on the side where the recirculation pump is stopped stops, so that the coolant temperature in the loop pipe decreases, and the reactor pressure vessel The difference with temperature increases. This temperature difference increases thermal fatigue in the vicinity of the connection between the reactor pressure vessel and the loop piping, which adversely affects the plant life.

  Moreover, when one recirculation pump stops, when the amount of coolant circulation in the core decreases, the reactor output decreases.

  Therefore, it is desired that the recirculation pump does not stop. However, the conventional variable voltage variable frequency power supply device for the recirculation pump is a power supply device when a semiconductor element single failure of the semiconductor power conversion circuit occurs or when a maintenance check of the semiconductor power conversion circuit is performed. Stopped and the recirculation pump stopped.

  In the technique disclosed in Patent Document 1, in order to prevent a device stop due to a single failure of a semiconductor element, a semiconductor power reverse conversion circuit is provided in series redundancy, and a circuit that bypasses each semiconductor power reverse conversion circuit is provided. Provide a switch. Thus, when a single failure of the semiconductor element occurs, the semiconductor power reverse conversion circuit including the failed element is switched to bypass, and the operation of the power supply device is continued. However, in the technique of this Patent Document 1, the variable voltage variable frequency power supply device for the recirculation pump is stopped when the failure portion is repaired even if the motor for driving the recirculation pump does not stop when the single failure of the semiconductor element occurs. The recirculation pump will stop.

  An object of the present invention is to enable repair of a faulty part or maintenance of a semiconductor power conversion circuit without stopping the recirculation pump when a single failure of the power supply for the recirculation pump occurs or during maintenance and inspection of the power supply. There is.

  To achieve the above object, a recirculation pump power supply according to the present invention is a recirculation pump power supply that supplies AC power to an electric motor that drives a recirculation pump of a boiling water reactor. A first bank having an AC / DC forward converter and a DC / AC reverse converter connected in series with each other, and outputting an alternating current having a voltage and frequency different from the inputted alternating voltage and frequency; And an AC / DC forward converter and a DC / AC reverse converter connected in series to each other, and outputs an alternating current having a voltage and frequency different from the inputted alternating current voltage and frequency, to the first bank. A second bank connected in parallel; a speed controller for controlling the speed of the motor by controlling the first and second banks; and electrically in series with each of the first and second banks Connection And the speed control device, when only the first bank is in a non-operating state. The operation of the entire first and second banks is temporarily stopped to cause the recirculation pump to idle, and during the idling of the recirculation pump, the shutoff mechanism connected to the first bank causes the first The first bank is disconnected, and after the first bank is disconnected during the idling of the recirculation pump, only the second bank is restarted when the speed of the electric motor reaches a predetermined speed. The speed of the motor is controlled only by the bank, and the speed of the motor is controlled only by the second bank, and then the first bank is restarted and the motor is controlled by the entire first and second banks. Control the speed of A it shall, characterized in that.

  The recirculation pump power supply control method according to the present invention is a recirculation pump power supply control method for controlling a recirculation pump power supply that supplies AC power to an electric motor that drives a recirculation pump of a boiling water reactor. The power supply for the recirculation pump has an AC / DC forward converter and a DC / AC reverse converter electrically connected in series with each other, and has a voltage and frequency different from the input AC voltage and frequency. A first bank that outputs alternating current, and an alternating current / direct current forward converter and an alternating current / direct current inverter that are electrically connected in series with each other, and a voltage and frequency that are different from the input alternating current voltage and frequency A second bank connected in parallel to the first bank, a speed control device for controlling the speed of the electric motor by controlling the first and second banks, and the first bank And A shut-off mechanism electrically connected in series to each of the second banks and capable of electrically connecting and disconnecting the first and second banks individually, and the power supply control method for the recirculation pump includes: An idling process for temporarily stopping the operation of the entire first and second banks and idling the recirculation pump when only the first bank is in an inoperative state; In the first bank separating step of separating the first bank by the shut-off mechanism connected to the first bank, and during the idling step after the first bank separating step, the speed of the electric motor is A second bank operation step of restarting only the second bank when the predetermined speed is reached and controlling the speed of the electric motor only by the second bank; and after the second bank operation step. The first Wherein the restarting the bank having a recovery operation step of controlling the speed of the motor by the overall first and second banks.

  According to the present invention, when a single failure occurs in the power supply device for the recirculation pump or when the power supply device is inspected and repaired, it is possible to repair the faulty part or perform maintenance and inspection of the semiconductor power conversion circuit without stopping the recirculation pump. .

  A first embodiment of a power supply device for a recirculation pump and its control device according to the present invention will be described with reference to FIGS.

  The boiling water reactor controls the reactor output by changing the circulation amount of the coolant in the reactor pressure vessel 1 shown in FIG. 1 by the reactor coolant recirculation system. As shown in FIG. 1, the reactor coolant recirculation system includes a recirculation pump 2, a recirculation pump drive power supply device 7, and a recirculation flow rate control device 4.

  The recirculation pump 2 is driven by a drive motor 15 and is connected to the reactor pressure vessel 1 via a loop pipe 5. The speed of the recirculation pump 2 is controlled by increasing / decreasing the output of the recirculation pump drive power supply device 7 according to the speed request signal 6 transmitted from the recirculation flow rate control device 4 and controlling the electric motor 15. Thereby, the circulation amount of the coolant in the reactor pressure vessel 1 is changed, and the reactor output is controlled.

  In order to control the recirculation pump 2, a variable voltage variable frequency power supply device is used as the drive power supply device 7 for the recirculation pump, the power supply voltage and the power supply frequency are controlled, and the recirculation pump speed is controlled.

  As shown in FIG. 1, this reactor coolant recirculation system is usually composed of two systems, each having a recirculation pump 2. Even if one of the recirculation pumps 2 is temporarily stopped due to failure of the variable voltage variable frequency power supply device 7 or maintenance inspection, the remaining one can continue to operate. Thereby, the coolant circulation amount may be reduced depending on conditions, but the coolant in the reactor pressure vessel 1 can be circulated.

  As shown in FIG. 2, the recirculation pump power supply device 7 includes two banks of semiconductor power conversion circuits 16 and 17 and a speed control device 12 which are parallel to each other. Each of the banks 16 and 17 of the semiconductor power conversion circuit converts the three-phase alternating current received from the in-house power supply system 8 into direct current, and converts the direct current obtained thereby into alternating current of an arbitrary frequency. And a semiconductor power reverse conversion circuit 10. In addition, an electrical cutoff mechanism 18 such as a circuit breaker or a semiconductor switch is connected in series to each of the banks 16 and 17.

  The semiconductor power conversion circuits 16 and 17 are controlled according to the speed request signal 6 from the recirculation flow rate control device 4 so that the ratio between the output voltage and the output frequency is constant. Thereby, the speed of the electric motor 15 that drives the recirculation pump 2 is controlled.

  The banks 16 and 17 of the semiconductor power conversion circuit are static voltage type inverter devices, and include a semiconductor power forward conversion circuit 9 and a semiconductor power reverse conversion circuit 10. As a result, the AC power from the in-house power supply system 8 is converted into DC power, and then converted into AC power having an appropriate voltage and frequency and supplied to the motor 15. Then, the speed control device 12 controls the banks 16 and 17 to generate a voltage and a frequency according to the speed request signal 6 from the recirculation flow rate control device 4 (FIG. 1).

  If a single semiconductor element failure occurs in the first bank 16 during operation of the variable voltage variable frequency power supply device 7, the speed control device 12 receives the semiconductor element failure signal 13. When performing maintenance and inspection of the bank 16, a semiconductor element control signal stop command is received. Thus, the semiconductor element control signal 14 is stopped from being output to the banks 16 and 17, and the variable voltage variable frequency power supply device 7 is stopped. At this time, the recirculation pump enters a free-run state due to inertia and gradually decelerates.

  A current detection device 30 is provided for each bank in the variable voltage variable frequency power supply device 7 for determining a single failure of the semiconductor element. These current detection devices 30 may detect either input current or output current to each bank. FIG. 2 shows an example in which the input current is detected. If the input current or output current exceeds a limit value in a single bank as compared with a preset limit value of input current or output current, it is determined that an abnormality has occurred in the semiconductor element in the bank. Note that when a normal semiconductor element fails, the element is short-circuited, and an excessive current flows, so that the failure can be detected. It is also possible to determine the occurrence of an abnormality of the element by the fact that the current flowing through the element is too small.

  For example, when a single failure of the semiconductor element occurs in the first bank 16 or when maintenance of the first bank 16 is performed, the speed control device 12 performs the semiconductor element control signal 14 for each bank 16, 17. And the variable voltage variable frequency power supply device 7 is stopped. At the same time, the cutoff signal 19 is sent to the electrical cutoff mechanism 18 provided before and after the first bank 16 including the faulty element or subject to maintenance and inspection, thereby operating the electrical cutoff mechanism 18. As a result, the first bank 16 is separated from the circuit.

  In the variable voltage variable frequency power supply device 7, when the first bank 16 including the faulty element or the object of maintenance inspection is disconnected from the circuit and operated only by the second bank 17 not including the faulty element or not the object of maintenance inspection. Then, the semiconductor element control signal 14 for the second bank 17 is once stopped, and the recirculation pump 2 is free-runned. Then, when the recirculation pump speed detected by the speed detection device (not shown) reaches a speed suitable for operation only in the second bank 17, the second bank 17 corresponds to the speed. The semiconductor element control signal 20 is output again. By operating the recirculation pump 2 at a reduced speed, the reactor recirculation pump 2 is not stopped.

  Here, an operation example of the first embodiment of the power supply device for the recirculation pump will be described with reference to the time change of the pump speed (that is, the motor speed) shown in FIG.

  First, the first and second banks operate to perform normal operation. At time t1, a failure occurs in the first bank 16, and an excessive current is detected by the current detection device 30 in the first bank 16. At time t2, the operation of both banks 16 and 17 is stopped by the command from the speed control device 12 based on the overcurrent signal, and the electric motor 15 starts free run. Further, the failed first bank 16 is electrically disconnected. Thereafter, the operation of the second bank 17 is resumed at the time t3 when the rotation speed of the electric motor 15 is reduced to a speed at which the operation of the single bank is possible, and the single bank operation is started. During the single operation by the second bank 17, the first bank 16 which is the object of failure repair and is electrically disconnected is repaired.

  Thereafter, when the failure repair of the first bank 16 is completed, the operation of the second bank 17 is stopped again at time t4, and a temporary free run is started again. Then, at the time t5 when the rotation is reduced to a speed that can be synchronized with both banks 16, 17, the first and second banks 16, 17 are turned on again, and then the rotational speed is gradually increased by the operation of both banks. To do. And it returns to rated operation again at time t6.

  Note that it is possible to arbitrarily design what percentage of the rated speed of the electric motor 15 can be obtained in the single bank operation. For example, it can be designed so that a rotation speed of 100% of the rated rotation of the electric motor 15 can be obtained in a single bank operation. The example of FIG. 3 is designed to obtain a speed of 70% in a single bank operation.

  Next, another operation example of the first embodiment will be described with reference to FIG. In this example, the process is the same as that in FIG. 3 until immediately before time t4 in FIG. In the case of FIG. 4, when the failure repair of the first bank 16 is completed during the single bank operation by the second bank 17, a free run is not performed by stopping the operation of the second bank 17 again (time t4). While continuing to operate the second bank 17, at time t7, the first bank 16 is turned on again to start the two-bank operation. In this case, in order to achieve synchronization, the voltage of the first bank 16 is gradually increased from zero. In this case, the rated operation is resumed again at time t8.

  In the description of FIG. 3 and FIG. 4, it is assumed that a failure occurs in the first bank 16. However, when the first bank 16 is separated in order to check the first bank 16 in a planned manner, Time t2 becomes simultaneous. The subsequent steps are the same as those in FIG.

  According to the present embodiment, even when a single failure of the semiconductor element in the first bank 16 or a maintenance check on the first bank 16 that may cause the variable voltage variable frequency power supply device 7 to stop is performed. One bank 16 can be electrically disconnected, and only the second bank 17 that does not include a faulty element or is not subject to maintenance inspection can be operated.

  As a result, the recirculation pump can be continuously operated with the speed maintained or reduced without stopping the variable frequency power supply device 7. By avoiding the stoppage of the recirculation pump, it is possible to maintain the circulation of the coolant in the loop piping even if the flow rate is reduced, maintaining the temperature of the coolant in the loop piping, and the loop piping and reactor pressure. It is possible to suppress an increase in thermal fatigue in the vicinity of the connection portion with the container.

  In addition, the capacity | capacitance of each bank is made larger than 50%, and the fall of the reactor power at the time of single bank operation can also be suppressed. Furthermore, it is also possible to design redundancy so that each bank can operate at the rated speed of the recirculation pump.

  When a single failure of a semiconductor element occurs, or when maintenance inspection of a bank is performed, the variable voltage variable frequency power supply device 7 is continuously operated only in the bank 17 that does not include the failure element or is not subject to maintenance inspection. The bank 16 that is included or that is the object of maintenance inspection can be removed from the variable voltage variable frequency power supply device 7.

  Next, a second embodiment of the power supply device for the recirculation pump according to the present invention will be described with reference to FIG. Here, overlapping description of parts common to the first embodiment is omitted.

  As shown in the block circuit configuration diagram of FIG. 5, in the recirculation pump power supply device 7, the connecting portion 21 between the variable voltage variable frequency power supply device 7 and the parallel banks 16 and 17 of the semiconductor power conversion circuit The structure is detachable easily. As a result, it is possible to simplify the replacement work of the bank 16 for repairing the failure or performing maintenance and to shorten the time required for the restoration.

It is a typical equipment block diagram of the reactor coolant recirculation system of the boiling water reactor which concerns on this invention. 1 is a block diagram of a first embodiment of a power supply device for a recirculation pump according to the present invention. It is a time chart which shows typically the change of the pump speed in the operation example of 1st Embodiment of the power supply device for recirculation pumps which concerns on this invention. It is a time chart which shows typically the change of the pump speed in the other operation example of 1st Embodiment of the power supply device for recirculation pumps which concerns on this invention. It is a block diagram of 2nd Embodiment of the power supply apparatus for recirculation pumps which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Recirculation pump, 4 ... Recirculation flow control device, 5 ... Loop piping, 6 ... Speed request signal, 7 ... Power supply device for recirculation pumps, 8 ... In-house power supply system, 9 ... Semiconductor Power forward conversion circuit, 10 ... Semiconductor power reverse conversion circuit, 11 ... Semiconductor power conversion circuit, 12 ... Speed controller, 13, 14 ... Semiconductor element failure signal, 14 ... Semiconductor element control signal, 15 ... Electric motor, 16 ... First Bank (semiconductor power conversion circuit), 17 ... second bank (semiconductor power conversion circuit) 18 ... electrical cut-off mechanism, 19 ... cut-off signal, 20 ... control signal to second bank, 21 ... connecting section, 30 ... Current detector Boiling water reactor reactor coolant

Claims (12)

In the power supply for the recirculation pump that supplies AC power to the electric motor that drives the recirculation pump of the boiling water reactor,
A first bank having an AC / DC forward converter and a DC / AC reverse converter electrically connected in series with each other, and outputting an alternating current having a voltage and frequency different from the input alternating voltage and frequency; ,
An AC / DC forward converter and a DC / AC reverse converter electrically connected in series to each other, and outputs an alternating current having a voltage and frequency different from the input alternating voltage and frequency; A second bank connected in parallel to the bank;
A speed controller for controlling the speed of the electric motor by controlling the first and second banks;
A shut-off mechanism electrically connected in series to each of the first and second banks and capable of electrically interrupting the first and second banks individually;
Have
The speed control device includes:
When only the first bank is in a non-operating state, the operation of the entire first and second banks is temporarily stopped to idle the recirculation pump,
During the idling of the recirculation pump, the first bank is separated by the shut-off mechanism connected to the first bank,
After the first bank is disconnected during idling of the recirculation pump, when the speed of the electric motor reaches a predetermined speed, only the second bank is restarted, and the electric motor is driven only by the second bank. Control the speed of
After controlling the speed of the electric motor only by the second bank, the first bank is restarted and the speed of the electric motor is controlled by the entire first and second banks.
A power supply device for a recirculation pump.   2. The power supply device for a recirculation pump according to claim 1, wherein the predetermined speed is a speed at which the speed of the electric motor can be controlled only by the second bank.   The speed control device controls the output voltage of the first bank to gradually increase from a zero state when restarting the first bank. Item 3. The power supply device for the recirculation pump according to Item 1 or 2.   The speed controller operates the second bank after controlling the speed of the electric motor only by the second bank and before controlling the speed of the electric motor by the entire first and second banks. Is temporarily stopped, the recirculation pump is idling again, and then the first and second banks are restarted simultaneously while the recirculation pump is idling. The power supply device for a recirculation pump according to claim 1 or 2. A current detector for detecting a current of each of the first and second banks;
When the current of one of the first or second bank detected by the current detector deviates from a predetermined range, the speed control device may change the first or second bank depending on the position of the current detector. To determine which is inactive,
The power supply device for recirculation pumps according to any one of claims 1 to 4.   The said 1st and 2nd bank has the electric power supply capability which respectively exceeds 50% of the electric power required for the rated operation of the said motor, The one of Claim 1 thru | or 5 characterized by the above-mentioned. Power supply for recirculation pump.   The power supply device for a recirculation pump according to any one of claims 1 to 6, further comprising a connecting portion capable of mechanically connecting and disconnecting the first and second banks individually. In a power control method for a recirculation pump that controls a power supply for a recirculation pump that supplies AC power to an electric motor that drives a recirculation pump of a boiling water reactor,
The power supply for the recirculation pump is:
A first bank having an AC / DC forward converter and a DC / AC reverse converter electrically connected in series with each other, and outputting an alternating current having a voltage and frequency different from the input alternating voltage and frequency; ,
An AC / DC forward converter and a DC / AC reverse converter electrically connected in series to each other, and outputs an alternating current having a voltage and frequency different from the input alternating voltage and frequency; A second bank connected in parallel to the bank;
A speed controller for controlling the speed of the electric motor by controlling the first and second banks;
A shut-off mechanism electrically connected in series to each of the first and second banks and capable of electrically interrupting the first and second banks individually;
Have
The recirculation pump power control method includes:
When only the first bank is in an inoperative state, an idling step of temporarily stopping the operation of the entire first and second banks and idling the recirculation pump;
A first bank separating step of separating the first bank by the blocking mechanism connected to the first bank in the middle of the idling step;
When the speed of the electric motor reaches a predetermined speed during the idling process after the first bank disconnecting process, only the second bank is restarted and the electric motor is operated only by the second bank. A second bank operation process for controlling the speed of
After the second bank operation step, a recovery operation step of restarting the first bank and controlling the speed of the electric motor by the entire first and second banks;
A power supply control method for a recirculation pump, comprising:   The power supply control method for a recirculation pump according to claim 8, wherein the predetermined speed is a speed at which the speed of the electric motor can be controlled only by the second bank.   The recirculation pump power supply according to claim 8 or 9, wherein the recovery operation step is controlled so that the output voltage of the first bank gradually increases from a zero state. Control method. A second idling step of temporarily stopping the operation of the second bank and idling the recirculation pump after the second bank operation step and before the recovery operation step;
The recovery operation step restarts the first and second banks simultaneously;
The power supply control method for recirculation pumps of Claim 8 or 9 characterized by these. Detecting respective currents of the first and second banks;
When one of the detected currents of the first or second bank deviates from a predetermined range, it is determined whether the first or second bank is in an inoperative state according to the position of the current detector. thing,
The power supply control method for a recirculation pump according to any one of claims 8 to 11.

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