Switching method and system for motor of circulating water pump of nuclear power plant

Abstract

Provided are a switching method and system for a motor (170) of a circulating water pump (152) of a nuclear power plant. The method (300) comprises: on the basis of a change of electromagnetic field energy conducted by a first predetermined conductor on an input side of a motor (170) of a circulating water pump (152), determining whether to generate a switching command for the motor (170) (S302); in response to detecting a generated switching command, acquiring a voltage or current waveform of the motor (170) side and a voltage or current waveform of a grid (162) side, the voltage of the motor (170) side being a superposed voltage of a residual voltage of the motor (170) and an induced electromotive force generated by the motor (170) (S304); at least on the basis of comparison between the voltage waveform of the motor (170) side and the voltage waveform of the grid (162) side, determining an action time of the switching command (S306); and, in response to the determined action time being reached, switching to direct power supply from the grid (162) to the motor (170) (S310). Thus, the present invention can accurately determine a time for performing electrical switching on the motor (170) of the circulating water pump (152), thus significantly improving the success rate of switching.

Description

Method and system for switching motors of circulating water pumps in nuclear power plants Technical Field

[0001] The present invention relates generally to the field of nuclear power, and in particular to a method and system for switching electric motors of circulating water pumps of a nuclear power plant. Background Art

[0002] The electric motors driving the circulating water pumps in the tertiary circuits of nuclear power plants are typically very powerful, and the motors and the impellers they drive are often located below a column of water. If the motor's inverter power supply suddenly loses due to a fault, the residual electromagnetic field in the motor causes the motor to continue rotating in its original direction. The water column impacts the impeller and the motor, compromising the motor's safety. If this impact causes the motor to malfunction, it could potentially cause the generators in the secondary circuit of the nuclear power plant to cease generating power, potentially leading to a major accident involving the primary nuclear reactor shutdown. Therefore, it is crucial to promptly identify inverter power supply failures in the circulating water pump motors of nuclear power plants and to quickly perform electrical switching on the motors.

[0003] Conventional methods for switching motor power supply systems are primarily used for connecting large generators to the grid in power plants, such as when closing a power grid. Rapid switching methods for fault handling typically only address a small number of electrical devices with different power sources and are generally not targeted at specific individual devices, such as the motor of a circulating water pump. Therefore, on the one hand, conventional methods for switching motor power supply systems cannot quickly and accurately identify inverter power supply failures in the drive motors of circulating water pumps in nuclear power plants, making them unsuitable for targeted electrical switching of the drive motors of circulating water pumps. On the other hand, conventional methods for switching motor power supply systems typically determine the timing for initiating switching based on the phase angle of the grid-side waveform detected by conventional electrical test instruments (e.g., current transformers and voltage transformers). However, transformers cause the detected waveform to lag 90° relative to the real-time waveform being measured, hindering rapid switching. Furthermore, because the state of the motor after power failure is significantly different from the normal state of the grid, conventional methods for switching motor power supply systems struggle to quickly switch the motors of circulating water pumps in nuclear power plants and can easily lead to switching failures.

[0004] In summary, the traditional method for switching the motor power supply system cannot accurately identify the inverter power supply failure of the drive motor of the circulating water pump in the nuclear power plant, and it is difficult to accurately determine the timing of electrical switching of the motor of the circulating water pump, which leads to switching failure.

[0005] Summary of the Invention

[0006] In response to the above problems, the present invention provides a method and system for the motor of a circulating water pump in a nuclear power plant, which can quickly identify the inverter power supply failure occurring in the motor of the circulating water pump in the nuclear power plant, and accurately determine the timing of electrical switching of the motor of the circulating water pump, thereby significantly improving the success rate of switching.

[0007] According to a first aspect of the present invention, a method for switching the motor of a circulating water pump of a nuclear power plant is provided, wherein the motor is powered via a frequency converter, the method comprising: determining whether to generate a switching instruction for the motor based on a change in electromagnetic field energy conducted by a first predetermined conductor on the input side of the motor of the circulating water pump; acquiring a voltage or current waveform on the motor side and a voltage or current waveform on the grid side in response to detecting the generated switching instruction, wherein the voltage on the motor side is a superimposed voltage of the residual voltage of the motor and the induced electromotive force generated by the motor; determining an action time of the switching instruction based at least on a comparison between the voltage waveform on the motor side and the voltage waveform on the grid side; and switching to direct power supply to the motor by the grid in response to arrival of the determined action time.

[0008] In some embodiments, the change in the electromagnetic field energy conducted by the first predetermined conductor indicates the rate of change of the electromagnetic field energy conducted by the first predetermined conductor over time, and the electromagnetic field energy conducted by the first predetermined conductor is determined based on the electric field strength, magnetic field strength and electromagnetic energy current density conducted by the first predetermined conductor.

[0009] In some embodiments, the electromagnetic field energy change is a vector, and determining whether to generate a switching instruction for the motor includes: calculating the electromagnetic field energy change conducted by the first predetermined conductor; determining whether the calculated electromagnetic field energy change indicates a sudden change in the electromagnetic field energy within the front and rear measuring end volumes of the first predetermined conductor; and if the calculated electromagnetic field energy change indicates a sudden change in the electromagnetic field energy within the front and rear measuring end volumes of the first predetermined conductor, generating a switching instruction for the motor of the circulating water pump of the nuclear power plant.

[0010] In some embodiments, generating a switching instruction for the motor of the circulating water pump of the nuclear power plant includes: in response to determining that the electromagnetic field energy change is a negative value, determining that there is a fault in the power supply of the inverter; and generating a switching instruction for the motor of the circulating water pump of the nuclear power plant.

[0011] In some embodiments, determining whether to generate a switching instruction regarding the motor also includes: if the calculated electromagnetic field energy change indicates that the electromagnetic field energy within the front and rear measuring end volumes of the first predetermined conductor is constant, then there is no need to generate a switching instruction regarding the motor of the circulating water pump of the nuclear power plant.

[0012] In some embodiments, determining the action time of the switching instruction based at least on a comparison of the voltage waveform on the motor side and the voltage waveform on the grid side includes: obtaining a first detection current on the motor side via a first predetermined conductor, one end of the first predetermined conductor being connected between the inverter and the motor, and the other end of the first predetermined conductor being grounded; obtaining a second detection current on the grid side via a second predetermined conductor, one end of the second predetermined conductor being connected between the grid and the inverter, and the other end of the second predetermined conductor being grounded; determining the waveform difference between the voltage waveform on the motor side and the voltage waveform on the grid side based on the first detection current waveform and the second detection current waveform; and determining the action time of the switching instruction based on the determined waveform difference.

[0013] In some embodiments, the method for switching the motor of the circulating water pump of a nuclear power plant also includes: causing the motor under the test condition to be powered off at different voltage amplitudes, so as to record the corresponding time required for the voltage on the motor side to change from the power-off state to a predetermined threshold value, thereby determining the corresponding relationship between the voltage amplitude change and the corresponding time.

[0014] In some embodiments, the method for switching the motor of the circulating water pump of a nuclear power plant also includes: obtaining the voltage or current waveform on the input side of the motor and the voltage or current waveform on the grid side at the moment of the inverter power supply failure; obtaining a prediction result on whether the switching is successful based on the obtained voltage or current waveform on the input side of the motor and the voltage or current waveform on the grid side through a predetermined verification algorithm; if the obtained prediction result indicates that the switching is successful, performing the switching operation based on the determined action time of the switching instruction; and generating an alarm message if the prediction result indicates that the switching is unsuccessful.

[0015] According to a second aspect of the present invention, a system for switching the motor of a circulating water pump of a nuclear power plant is provided, the system comprising: a frequency converter for supplying power to the motor of the circulating water pump of the nuclear power plant, the input side of the frequency converter being connected to the power grid via a second switch; a motor, the input side of the motor being connected to the output side of the frequency converter via a third switch, the input side of the motor being connected to one end of a fourth switch, the other end of the fourth switch being connected to the power grid; a first predetermined conductor being arranged on the input side of the motor, for obtaining a real-time voltage or current waveform on the input side of the motor; and a computing device configured to execute the method of the first aspect.

[0016] In some embodiments, the system for switching the motor of the circulating water pump of the nuclear power plant further includes: a second predetermined conductor, configured on the grid side, for obtaining the real-time voltage or current waveform on the grid side.

[0017] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. It is not intended to identify key features or essential features of the invention, nor is it intended to limit the scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0019] FIG1 shows a schematic diagram of a system 100 in which a circulating water system of a nuclear power plant is located according to an embodiment of the present invention.

[0020] 2 illustrates a schematic diagram of a system for implementing a method for switching a motor of a circulating water pump of a nuclear power plant according to some embodiments of the present invention.

[0021] FIG3 illustrates a flow chart of a method for switching a motor of a circulating water pump of a nuclear power plant according to an embodiment of the present invention.

[0022] FIG4 illustrates a flow chart of a method for determining an action time of a switching instruction according to an embodiment of the present invention.

[0023] FIG5 schematically shows a block diagram of an electronic device suitable for implementing an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided to make the present disclosure more thorough and complete, and to fully convey the scope of the present disclosure to those skilled in the art.

[0025] As used herein, the term "including" and its variations represent open inclusion, i.e., "including but not limited to." Unless otherwise stated, the term "or" means "and / or." The term "based on" means "based at least in part on." The terms "one example embodiment" and "an embodiment" mean "at least one example embodiment." The term "another embodiment" means "at least one additional embodiment." The terms "first," "second," etc. may refer to different or identical objects.

[0026] As described above, the traditional method for switching the motor power supply system cannot accurately identify the inverter power supply failure of the drive motor of the circulating water pump in the nuclear power plant, and it is difficult to accurately determine the timing of electrical switching of the motor of the circulating water pump, which leads to switching failure.

[0027] To at least partially address one or more of the above-mentioned problems and other potential problems, the present invention proposes a method for switching a circulating water system in a nuclear power plant. In the scheme of the present invention, based on the change in electromagnetic field energy conducted by a first predetermined conductor on the motor side of the circulating water pump, the present invention can quickly determine whether a frequency converter power supply failure exists, and thus quickly determine whether to generate a switching instruction for the motor of the circulating water pump in the nuclear power plant. Furthermore, in response to detecting the generated switching instruction, the waveform of the motor-side voltage (which indicates the superimposed voltage of the motor residual voltage and the induced electromotive force generated by the motor) and the waveform of the grid voltage are obtained, and the action time of the switching instruction is determined based on at least a comparison of the waveform of the motor-side voltage and the waveform of the grid voltage. When the action time arrives, the power supply to the motor is switched directly from the grid to the power supply. The present invention can determine the action time of the switching instruction based on the difference in real-time waveforms between the motor side and the grid side when the frequency converter power supply fails, thereby avoiding errors in the calculation of the switching time caused by deformation of the current or voltage waveform of the motor when the frequency converter power supply fails. Therefore, the present invention quickly identifies the inverter power supply failure occurring in the circulating water pump motor in the nuclear power plant and accurately determines the timing of electrical switching of the circulating water pump motor, thereby significantly improving the success rate of switching.

[0028] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments, and they should not be understood as limiting the scope of protection of this application. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0029] FIG1 illustrates a schematic diagram of a circulating water system 100 of a nuclear power plant according to an embodiment of the present invention. System 100 includes a reactor assembly (i.e., primary loop 110), a steam turbine generator system (i.e., secondary loop 130), and a circulating water system (i.e., tertiary loop 150).

[0030] The primary circuit 110 includes, for example, a pressure vessel 112, control rods 114, a pressurizer 116, a steam generator heat exchange line 118, and a first pump 120. The primary circuit 110 is used to allow nuclear fuel to react in the reactor core within the pressure vessel 112, generating heat to heat the primary circuit coolant. The heated coolant, driven by the first pump 120, enters the steam generator heat exchange line 118 to heat the cooling water in the secondary circuit 130. The coolant, having flowed through the steam generator heat exchange line 118, is then returned by the first pump 120 to the reactor core within the pressure vessel 112 for reheating.

[0031] The secondary circuit 130 includes, for example, a steam turbine 132, a condenser 134, a steam generator 136, and a second pump 138. The secondary circuit 130 is used to supply steam, heated and vaporized by the steam generator, to the steam turbine 132, which then drives the turbine generator 140 to generate power. The secondary circuit 130 also supplies cooling water flowing through the steam turbine 132 to the condenser 134, thereby exchanging heat with the circulating water in the tertiary circuit flowing through the condenser 134 and raising the circulating water temperature. The cooling water from the condenser 134 is then returned to the steam generator 136 by the second pump 138.

[0032] Tertiary circuit 150, for example, includes a circulating water pump 152, a condenser heat exchange line 154, a first temperature detection unit, a second temperature detection unit (the first temperature detection unit is located, for example, at the seawater inlet of the circulating water system, and the second temperature detection unit is located, for example, at the seawater outlet of condenser 134, not shown in Figure 1), a motor 170 for driving circulating water pump 152, and a system 190 for switching the motors of the nuclear power plant's circulating water pumps. Tertiary circuit 150 utilizes seawater drawn by circulating water pump 152 to supply condenser 134, thereby cooling the steam in secondary circuit 130 and liquefying it back into condensate. Seawater flowing through condenser 134 is then returned to the sea.

[0033] System 190 for switching motors of circulating water pumps of a nuclear power plant includes, for example, a power grid 162 , a third switch 168 , a frequency converter 166 , a second switch 164 , a fourth switch 172 , a computing device 160 , a first predetermined conductor 180 , and a second predetermined conductor 184 .

[0034] Regarding the power grid 162, it is used to supply power. In some embodiments, the power grid 162 is, for example, a busbar. In some embodiments, the power supply voltage of the power grid 162 is, for example, but not limited to, 6.6 kV or 10 kV.

[0035] The frequency converter 166 is used to supply power to the motor 170 that drives the circulating water pump 152. The input side of the frequency converter 166 is connected to the grid 162 via the second switch 164. The output side of the frequency converter 166 is connected to the motor 170 via the third switch 168.

[0036] Regarding motor 170, it is used to drive the nuclear power plant's circulating water pump 152. The input side of motor 170 is connected to the output side of inverter 166 via third switch 168. The input side of the motor is connected to one end of fourth switch 172, and the other end of fourth switch 172 is connected to the power grid. In some embodiments, the power of motor 170 is, for example, but not limited to, 7200 kW or 6800 kW.

[0037] First conductor 180 is located on the motor 170 side, i.e., on the motor's input side, and is used to obtain a real-time voltage or current waveform at the motor's input side. In some embodiments, first conductor 180 is used to obtain a first detection current at the motor 170 input side. One end of first conductor 180 is connected between the inverter and the motor, and the other end of first conductor 180 is grounded.

[0038] Second predetermined conductor 184 is configured on the grid side and is used to obtain a real-time voltage or current waveform on the grid side. In some embodiments, second predetermined conductor 184 is used to obtain a second detection current on the grid side. One end of second predetermined conductor 184 is connected between grid 162 and input switch 164 of inverter 166, and the other end of second predetermined conductor 184 is grounded.

[0039] Computing device 160 is configured to execute a method for switching the motor of a circulating water pump in a nuclear power plant. Specifically, computing device 160 is configured to determine whether to generate a switching instruction for the motor based on changes in electromagnetic field energy conducted by a first predetermined conductor on the input side of the circulating water pump motor; and if a generated switching instruction is detected, obtain the voltage or current waveform on the motor side and the voltage or current waveform on the grid side. Computing device 160 is further configured to determine an action time for the switching instruction based at least on a comparison of the voltage waveform on the motor side and the voltage waveform on the grid side; and in response to the determined action time being reached, switch to direct power supply to the motor from the grid. In some embodiments, computing device 160 may have one or more processing units, including specialized processing units such as GPUs, FPGAs, and ASICs, as well as general-purpose processing units such as CPUs. Furthermore, one or more virtual machines may also be running on each computing device. In some embodiments, computing device 160 is, for example, a PLC.

[0040] 2 illustrates a schematic diagram of a system 190 for implementing a method for switching a motor of a circulating water pump in a nuclear power plant according to some embodiments of the present invention. System 190 includes: a power grid 162, a first switch 163, a second switch 164, a third switch 168, a frequency converter 166, a fourth switch 172, a computing device 160, a first predetermined conductor 180, a second predetermined conductor 184, and a signal processing circuit 186.

[0041] Inverter 166 also includes an inverter input switch 174, a resistor R connected in parallel with inverter input switch 174, a phase-shifting transformer 176, and a power unit 178. One end of inverter input switch 174 is connected to one end of second switch 164. The other end of inverter input switch 174 is connected to the input of phase-shifting transformer 176. The output of phase-shifting transformer 176 is connected to the input of power unit 178. The output of power unit 178 is connected to one end of third switch 168. The other end of third switch 168 is connected to motor 170.

[0042] In some embodiments, system 190 is deployed in multiple cabinets, for example. These cabinets may include, for example, a variable frequency incoming cabinet, a high-voltage pre-charging cabinet, a phase-shifting transformer cabinet, a power unit cabinet, a control cabinet, an outgoing cabinet, and an industrial frequency cabinet, arranged in sequence. The second switch 164 and the busbar of the power grid 162 are deployed in the variable frequency incoming cabinet. The high-voltage pre-charging cabinet may be configured to include a pre-charging circuit for starting the inverter. The phase-shifting transformer cabinet may contain a phase-shifting transformer 176. The power unit cabinet may contain a power unit 178. The third switch 168 may be deployed in the outgoing cabinet. The fourth switch 172 may be deployed in the industrial frequency cabinet. The control cabinet may contain computing equipment 160, for example.

[0043] Regarding the power supply control method for inverter 166, for example, the computing device 160 first determines whether the first switch 163, the second switch 164, the third switch 168, and the fourth switch 172 are in the disconnected (open) state; whether the first switch 163, the second switch 164, and the third switch 168 are in the ready state, and whether the fourth switch 172 is in the isolated state. If the computing device 160 determines that each of the above states is true, the computing device 160 controls the first switch 163 and the second switch 164 to be connected (closed), thereby activating the inverter's pre-charge circuit. If the inverter pre-charge is successful, the inverter input switch 174 is closed, and the inverter 166 completes the high-voltage power-up. If the computing device 160 determines that the inverter 166 has received status data indicating that the inverter 166 is self-testing ready, it sends a start command to the inverter 166 and causes the third switch 168 to be connected (closed). After the inverter 166 is started, the motor enters the variable frequency speed regulation mode.

[0044] If computing device 160 determines that inverter 166 is faulty or experiencing a power supply failure, computing device 160 determines an actuation time for the switching command based on a comparison of the waveform of the motor-side voltage and the grid voltage. Upon reaching the actuation time, computing device 160 switches fourth switch 172 on (closes) the switch to enable the motor to enter a power frequency operating state. The present invention automatically detects inverter faults or power supply failures based on changes in electromagnetic field energy conducted by a first predetermined conductor on the motor's input side.

[0045] Regarding the method by which the computing device 160 controls the shutdown of the inverter 166, for example, the computing device 160 sends an inverter shutdown command to the inverter 166, causing the inverter 166 to coast to a stop according to a pre-set curve; if the computing device 160 confirms, based on the received detection data, that the inverter 166 is in a stopped state, the third switch 168 and the second switch 164 are opened. Subsequently, the inverter input switch 174 automatically trips based on the electrical interlocking relationship between the inverter input switch and the second switch. The electrical interlocking relationship between the inverter input switch and the second switch includes: the second switch can only be closed when the inverter input switch is in the open state; and if the second switch is in the open state, the inverter input switch automatically trips. Furthermore, an electrical interlocking relationship also exists between the third switch 168 and the fourth switch 172, i.e., the third switch 168 and the fourth switch 172 cannot be closed simultaneously.

[0046] 3 illustrates a flow chart of a method 300 for switching a motor of a circulating water pump of a nuclear power plant according to an embodiment of the present invention. It should be understood that the method 300 may further include additional steps not shown and / or may omit steps shown, and the scope of the present invention is not limited in this respect.

[0047] In step 302 , the computing device 160 determines whether to generate a switching instruction for the motor based on a change in electromagnetic field energy conducted by a first predetermined conductor on an input side of the motor of the circulating water pump.

[0048] Regarding the change in electromagnetic field energy conducted by the first predetermined conductor, it is a vector and has directionality. In the traditional method for switching the motor power supply system, the deviation from the grid current or voltage is generally detected by conventional electrical test instruments (for example, current transformers and voltage transformers), and the detected deviation is usually a scalar. However, the current or voltage on the motor side is a changing waveform, and its change at different positions has directionality. For example, when the waveform passes through 0, it may be about to become a positive value or about to become a negative value. Since the traditional method of detecting current or voltage cannot identify the direction of change, the system needs to wait for a period of time (one or more cycles) to identify the direction of change. The above waiting will cause a lag in the switching action. The present invention uses the electromagnetic field energy change, a directional vector, to identify the fault of the motor variable frequency power supply. Without waiting, the fault of the motor variable frequency power supply can be quickly identified.

[0049] Regarding the first predetermined conductor, one end is connected between the frequency converter and the motor (for example, at the connecting cable between the frequency converter and the motor), and the other end is grounded. It should be understood that if the variable frequency power supply of the motor is normal, the electromagnetic energy transmitted into the first predetermined conductor should be approximately equal to the electromagnetic energy transmitted out of the first predetermined conductor, that is, the change in the electromagnetic field energy conducted by the first predetermined conductor is "0". If the variable frequency power supply of the motor fails, for example, there is electromagnetic energy transmitted into the first predetermined conductor, while the electromagnetic energy transmitted out of the first predetermined conductor is "0", at this time, the change in the electromagnetic field energy conducted by the first predetermined conductor is negative, or indicates a sudden change. Therefore, the present invention can quickly identify the failure of the variable frequency power supply of the motor based on whether the change in the electromagnetic field energy conducted by the first predetermined conductor indicates a sudden change (for example, indicating a negative value), without having to wait for one or more cycles.

[0050] A method for determining whether to generate a switching instruction regarding an electric motor, for example, includes: the computing device 160 calculates the change in electromagnetic field energy conducted by the first predetermined conductor; determines whether the calculated change in electromagnetic field energy indicates a sudden change in the electromagnetic field energy within the front and rear measuring end volumes of the first predetermined conductor; and generates a switching instruction regarding the electric motor of the circulating water pump of the nuclear power plant if the calculated change in electromagnetic field energy indicates a sudden change in the electromagnetic field energy within the front and rear measuring end volumes of the first predetermined conductor.

[0051] Regarding the change in electromagnetic field energy conducted by the first predetermined conductor, it indicates the rate of change of the electromagnetic field energy W of the first predetermined conductor over time t. Regarding the electromagnetic field energy W of the first predetermined conductor, it is determined based on at least the electric field strength, magnetic field strength, and electromagnetic energy flux density of the first predetermined conductor.

[0052] The calculation method of the change in electromagnetic field energy conducted by the first predetermined conductor is described below in conjunction with formulas (1) and (2).

[0053] In the above formulas (1) and (2), E represents the electric field strength. H represents the magnetic field strength. S represents the electromagnetic energy flux density, which is used to indicate the electromagnetic energy passing through a unit area. "×" represents the cross product in vector calculations. represents the Hamiltonian operator. "·" represents the dot product in vector calculations. W represents the electromagnetic field energy in the volume V of the first predetermined conductor. t represents time. V represents the volume of the first predetermined conductor. dV represents the unit volume of the first predetermined conductor. J represents the displacement current density. represents the change in electromagnetic field energy of the first predetermined conductor. It is a vector quantity indicating the rate of change of the electromagnetic field energy W of the first predetermined conductor with time t. dA represents a unit area. A represents an area.

[0054] The following describes a method for calculating the electromagnetic field energy of the volume V of the first predetermined conductor in conjunction with formula (3).

[0055] In the above formula (3), W represents the electromagnetic field energy of the volume V of the first predetermined conductor. V represents the volume of the first predetermined conductor. B represents the magnetic induction intensity. E represents the electric field intensity. D represents the electric flux density. ω represents the electrical angle.

[0056] It should be understood that when there is no inverter power supply failure, the electromagnetic field energy conducted by the first predetermined conductor is substantially constant. If the first predetermined conductor only conducts energy into but not out, it indicates that the electromagnetic field energy conducted by the first predetermined conductor has stopped. At this time, the electromagnetic field energy conducted by the first predetermined conductor changes. Therefore, the computing device 160 can determine that the change in electromagnetic field energy conducted by the first predetermined conductor on the input side of the motor is a negative value, and thus can determine that a power supply failure of the frequency converter occurs.

[0057] In step 304 , if the computing device 160 detects the generated switching instruction, the voltage or current waveform on the motor side and the voltage or current waveform on the grid side are obtained, where the voltage on the motor side is the superimposed voltage of the motor residual voltage and the induced electromotive force generated by the motor.

[0058] The following describes a method for calculating the residual voltage of the motor on the input side of the motor after power failure, using formula (4). The following describes a method for calculating the induced electromotive force on the input side of the motor after power failure, using formula (5).

[0059] In the above formulas (4) and (5), U represents the residual voltage of the motor. ε represents the induced electromotive force on the input side of the motor. S represents the electromagnetic energy flow density. t represents time. l represents length. ν represents wave velocity. U m It should be understood that when the variable frequency power supply is not faulty, the voltage on the motor input side is roughly the same as the grid voltage. When the variable frequency power supply fails, the residual voltage on the motor input side decays.

[0060] The following formula (6) illustrates an expression for the grid voltage.

[0061] In the above formula (6), U N represents the peak value of the grid voltage. t represents time. ω represents the electrical angle (or "angular frequency"), expressed in radians per second. Represents the initial phase, expressed in radians or degrees. U represents the grid voltage.

[0062] At step 306 , the computing device 160 determines an actuation time of the switching command based at least on a comparison of the voltage waveform on the motor side and the voltage waveform on the grid side.

[0063] Regarding the method for determining the action time of a switching instruction, for example, the method includes: the computing device 160 obtains a first detection current on the motor side via a first predetermined conductor, one end of the first predetermined conductor being connected between the inverter and the motor, and the other end of the first predetermined conductor being grounded; obtains a second detection current on the grid side via a second predetermined conductor, one end of the second predetermined conductor being connected between the grid and the inverter, and the other end of the second predetermined conductor being grounded; determines a waveform difference between a voltage waveform on the motor side and a voltage waveform on the grid side based on the first detection current waveform and the second detection current waveform; and determines the action time of the switching instruction based on the determined waveform difference. The method for determining the action time of the switching instruction will be described in detail below in conjunction with FIG. 4 and will not be repeated here.

[0064] At step 308 , the computing device 160 determines whether the action time has arrived. If the computing device 160 determines that the action time has not arrived, it waits at step 306 .

[0065] In step 310 , if the action time determined by the computing device 160 arrives, the grid is switched to directly supplying power to the motor.

[0066] In the above scheme, based on the change in electromagnetic field energy conducted by the first predetermined conductor on the motor side of the circulating water pump, the present invention can quickly determine whether there is a frequency converter power supply failure, and thus can quickly determine whether to generate a switching instruction for the motor of the circulating water pump of the nuclear power plant. In addition, in response to detecting the generated switching instruction, the waveform of the motor side voltage (which indicates the superimposed voltage of the motor residual voltage and the induced electromotive force generated by the motor) and the waveform of the grid voltage are obtained, and the action time of the switching instruction is determined based on at least the comparison of the waveform of the motor side voltage and the waveform of the grid voltage; when the action time arrives, the power supply of the motor is switched directly to the grid. The present invention can determine the action time of the switching instruction based on the difference in real-time waveforms between the motor side and the grid side when the frequency converter power supply fails, and will not cause switching time calculation errors due to deformation of the current or voltage waveform of the motor when the frequency converter power supply fails. Therefore, the present invention quickly identifies the frequency converter power supply failure of the circulating water pump motor in the nuclear power plant and accurately determines the timing of electrical switching of the circulating water pump motor, significantly improving the success rate of switching.

[0067] In some embodiments, method 300 further includes a switching verification method. For example, computing device 160 obtains a voltage or current waveform on the motor input side and a voltage or current waveform on the grid side at the moment of the inverter power supply failure; obtains a prediction result regarding whether the switching is successful based on the obtained voltage or current waveform on the motor input side and the voltage or current waveform on the grid side via a predetermined verification algorithm; if the obtained prediction result indicates that the switching is successful, performs a switching operation based on the determined action time of the switching instruction; and generates an alarm message if the prediction result indicates that the switching is unsuccessful.

[0068] The following examples are used in conjunction with formulas (7) and (8) to illustrate the verification algorithm. It should be understood that the predetermined verification algorithm may also be other algorithms.

[0069] In the above formulas (7) and (8), u represents the line voltage. x is the length of the line. t represents time. z c represents the wave impedance, In the formula, L represents the inductance of the segment line, C represents the capacitance of the segment line. v represents the wave velocity, It represents the forward-traveling wave or the positive-traveling wave. Its physical meaning is that as time increases, the forward-traveling wave moves away from the fault point in the positive direction. stands for counter-traveling wave or reverse traveling wave, Indicates that u2 is a variable Specifically, in the above formula (7) Indicates that u1 is a variable The function is defined as hour, hour, There is a value. Assume that at t = t1, the voltage value of point x1 on the line is u a , when time changes from t1 to t2, it has the same voltage value u a The point x2 must have This indicates that the voltage value u a The point is that the forward current wave moves away from the fault point in the positive direction at the wave velocity v. The above formula (8) corresponds to the line voltage in formula (7) divided by the wave impedance to represent the forward current wave and the reverse current wave. i represents the current.

[0070] By adopting the above-mentioned means, the present invention can further improve the reliability of automatically switching the motor from variable frequency power supply to industrial frequency power supply.

[0071] Figure 4 illustrates a flow chart of a method 400 for determining an action time of a switching instruction according to an embodiment of the present invention. It should be understood that the method 400 may further include additional steps not shown and / or may omit steps shown, and the scope of the present invention is not limited in this respect.

[0072] In step 402 , the computing device 160 obtains a first detection current on the motor side via a first predetermined conductor, where one end of the first predetermined conductor is connected between the inverter and the motor, and the other end of the first predetermined conductor is grounded.

[0073] In some embodiments, the first predetermined conductor is, for example, a resistor with a resistance exceeding a predetermined value. In some embodiments, as shown in Figure 2, one end of the first predetermined conductor 180 is connected to the end of the third switch 168 proximal to the motor 170, and the other end of the first predetermined conductor 180 is grounded. Through the first predetermined conductor, the signal processing circuit 186 of the present invention can obtain a first detection current. It should be understood that the first detection current can reflect the characteristics of the motor-side voltage waveform in real time, unlike traditional transformer detection methods, which cause the detection signal waveform to lag relative to the real-time motor-side voltage waveform. In some embodiments, the first predetermined conductor is a resistor with a large resistance, thereby reducing the current flowing through the first predetermined conductor to a small value. A first additional conductor is then extended from the middle of the first predetermined conductor, with the other end of the first additional conductor grounded, thereby obtaining an even smaller first detection current. The magnitude and waveform of the first detection current are then detected using an electromagnetic chip. It should be understood that the waveform of the motor-side voltage can be derived based on the waveform of the first detection current.

[0074] In step 404 , the computing device 160 obtains a second detection current on the grid side via a second predetermined conductor, where one end of the second predetermined conductor is connected between the grid and the inverter, and the other end of the second predetermined conductor is grounded.

[0075] Regarding the second predetermined conductor, it is, for example, also a resistor whose resistance exceeds a predetermined value. In some embodiments, as shown in FIG2 , one end of the second predetermined conductor 184 is connected to the end of the first switch 163 close to the power grid 162, and the other end of the second predetermined conductor 184 is grounded. Through the second predetermined conductor, the signal processing circuit can obtain a second detection current. The second detection current can reflect the characteristics of the grid-side voltage waveform in real time. In some embodiments, the second predetermined conductor can be made into a resistor with a large resistance value, so that the current flowing through the second predetermined conductor is a small current. Then, a second additional conductor is led out from the middle of the second predetermined conductor, so that the other end of the second additional conductor is grounded, thereby obtaining a smaller second detection current. Then, the magnitude and waveform of the second detection current are detected using an electromagnetic chip. Similarly, based on the waveform of the second detection current, the waveform of the grid-side voltage can be obtained.

[0076] At step 406 , the computing device 160 determines a waveform difference between the voltage waveform on the motor side and the voltage waveform on the grid side based on the first detected current waveform and the second detected current waveform.

[0077] The waveform difference is, for example, the phase difference between the peak values ​​of the two waveforms. In some embodiments, the waveform difference may also be the amplitude difference between the two waveforms. For example, computing device 160 determines the phase difference between the peak values ​​of the motor input voltage and the grid voltage waveforms by graphically comparing the waveforms.

[0078] Since the waveform of the first detection current (or the voltage on the motor input side) reflects the real-time full waveform of the current (or voltage) on the motor side, and the waveform of the second detection current (or the grid voltage waveform) reflects the real-time full waveform of the current (or voltage) on the grid side, the computing device 160 can directly determine the waveform difference between the first detection current waveform and the second detection current waveform, such as the phase difference between the peaks, or the amplitude difference.

[0079] In step 408 , the computing device 160 determines an action time of the switching instruction based on the determined waveform difference.

[0080] Regarding the method for determining the action time of the switching instruction, it includes, for example: if the computing device 160 determines that the waveform difference is less than or equal to a predetermined difference threshold, determining the switching timing; and determining the action time of the switching instruction based on the correspondence between the voltage and voltage amplitude changes on the input side of the motor at the moment of the inverter power supply failure and the corresponding time.

[0081] For example, the computing device 160 determines that the waveform of the first detection current will reach its peak after 0.5ms, and the waveform of the second detection current will reach its peak after 0.3ms, and the waveform difference between the two peaks is less than or equal to a predetermined difference threshold; then the computing device 160 will determine the action time of the switching instruction based on the voltage value on the motor side at the moment of the inverter power supply failure and the corresponding relationship between the predetermined voltage amplitude change and the corresponding time.

[0082] Regarding the method for determining the correspondence between the voltage amplitude change and the corresponding time, for example, it includes: de-energizing the motor under test conditions at different voltage amplitudes to record the corresponding time required for the motor-side voltage to change from the time of de-energization to a predetermined threshold, thereby determining the correspondence between the voltage amplitude change and the corresponding time. For example, if the time difference between the motor-side voltage reaching the peak value when the motor is de-energized at the current voltage value is 5 ms, and the corresponding mechanical operation time of the fourth switch is 80 ms, the computing device 160 will determine the actuation time of the switching instruction based on the 5 ms time difference to the peak value and the 80 ms mechanical operation time of the fourth switch.

[0083] It should be understood that the traditional method of determining the switching time in the motor grid-connected scenario is, for example, to perform grid-connected switching based on the time point of the predetermined phase difference (for example, 30°) before the waveform reaches the highest peak. However, in the case of a power failure of the inverter power supply of the motor of the nuclear power plant circulating water pump, the amplitude of the current or voltage waveform on the motor side decays very quickly and is not a theoretical sine waveform, and the corresponding period will also become longer. Therefore, the traditional method of performing grid-connected switching based on the time point of the predetermined phase difference (for example, 30°) before the highest peak in the motor grid-connected scenario is not applicable and will result in significant errors. The present invention determines the switching action time based on the waveform difference between the real-time current waveforms on the grid side and the motor side, and the corresponding relationship between the measured voltage amplitude change and the corresponding time, thereby avoiding the problem of switching failure caused by the deformation of the current or voltage waveform on the motor side due to power failure of the motor due to the power supply failure of the inverter.

[0084] Fig. 5 schematically illustrates a block diagram of an electronic device 500 suitable for implementing an embodiment of the present invention. Electronic device 500 can be for implementing method 300 to 400 shown in Figures 3 to 4. As shown in Figure 5, electronic device 500 includes a central processing unit (i.e., CPU 501), which can perform various appropriate actions and processes according to the computer program instructions stored in a read-only memory (i.e., ROM 502) or the computer program instructions loaded into a random access memory (i.e., RAM 503) from a storage unit 508. In RAM 503, various programs and data required for the operation of electronic device 500 can also be stored. CPU 501, ROM 502 and RAM 503 are connected to each other by bus 504. Input / output interface (i.e., I / O interface 505) is also connected to bus 504.

[0085] Multiple components in the electronic device 500 are connected to the I / O interface 505, including an input unit 506, an output unit 507, and a storage unit 508. The CPU 501 performs the various methods and processes described above, such as methods 300 to 400. For example, in some embodiments, methods 300 to 400 may be implemented as a computer software program stored on a machine-readable medium, such as the storage unit 508. In some embodiments, part or all of the computer program may be loaded and / or installed on the electronic device 500 via the ROM 502 and / or the communication unit 509. When the computer program is loaded into the RAM 503 and executed by the CPU 501, one or more operations of the methods 300 to 400 described above may be performed. Alternatively, in other embodiments, the CPU 501 may be configured to perform one or more actions of methods 300 to 400 by any other appropriate means (e.g., by means of firmware).

[0086] It should be further noted that the present invention may be a method, an apparatus, a system and / or a computer program product. The computer program product may include a computer-readable storage medium carrying computer-readable program instructions for executing various aspects of the present invention.

[0087] Computer-readable storage medium can be a tangible device that can keep and store the instructions used by the instruction execution device.Computer-readable storage medium can be, for example, but not limited to, an electrical storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device or any suitable combination thereof.More specific examples (non-exhaustive list) of computer-readable storage medium include: a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), a static random access memory (SRAM), a portable compact disc read-only memory (CD-ROM), a digital versatile disk (DVD), a memory stick, a floppy disk, a mechanical encoding device, for example, a punch card or a convex structure in a groove having instructions stored thereon, and any suitable combination thereof.Computer-readable storage medium used herein is not interpreted as a transient signal itself, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagated by waveguides or other transmission media (for example, light pulses by fiber optic cables), or electrical signals transmitted by wires.

[0088] The computer-readable program instructions described herein can be downloaded from a computer-readable storage medium to each computing / processing device, or downloaded to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network. The network can include copper transmission cables, fiber optic transmission, wireless transmission, routers, firewalls, switches, gateway computers, and / or edge servers. The network adapter card or network interface in each computing / processing device receives the computer-readable program instructions from the network and forwards the computer-readable program instructions to be stored in the computer-readable storage medium in each computing / processing device.

[0089] The computer program instructions for performing the operation of the present invention can be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk, C++, and conventional procedural programming languages ​​such as "C" language or similar programming languages. The computer readable program instructions can be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer, partially on a remote computer, or completely on a remote computer or server. In the case of a remote computer, the remote computer can be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or can be connected to an external computer (e.g., using an Internet service provider to connect via the Internet). In some embodiments, an electronic circuit, such as a programmable logic circuit, a field programmable gate array (FPGA), or a programmable logic array (PLA), can be personalized by utilizing the state information of the computer readable program instructions, and the electronic circuit can execute the computer readable program instructions, thereby realizing various aspects of the present invention.

[0090] Various aspects of the present invention are described herein with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each block of the flowcharts and / or block diagrams, and the combination of blocks in the flowcharts and / or block diagrams, can be implemented by computer-readable program instructions.

[0091] These computer-readable program instructions can be provided to a processor in a voice interaction device, a general-purpose computer, a special-purpose computer, or a processing unit of another programmable data processing device, thereby producing a machine such that when these instructions are executed by the processing unit of the computer or other programmable data processing device, a device is generated that implements the functions / actions specified in one or more blocks in the flowchart and / or block diagram. These computer-readable program instructions can also be stored in a computer-readable storage medium, where these instructions cause the computer, programmable data processing device, and / or other device to operate in a specific manner. Thus, the computer-readable medium storing the instructions comprises an article of manufacture that includes instructions for implementing various aspects of the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0092] Computer-readable program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device so that a series of operational steps are performed on the computer, other programmable data processing apparatus, or other device to produce a computer-implemented process, thereby causing the instructions executed on the computer, other programmable data processing apparatus, or other device to implement the functions / actions specified in one or more blocks in the flowchart and / or block diagram.

[0093] The flow charts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of the present invention. In this regard, each box in the flow chart or block diagram can represent a part of a module, program segment or instruction, and the part of this module, program segment or instruction contains one or more executable instructions for realizing the logical function of the specification. In some alternative implementations, the functions marked in the box can also occur in a sequence different from that marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flow chart, and the combination of the boxes in the block diagram and / or flow chart can be implemented with a special hardware-based system that performs the function or action of the specification, or can be implemented with a combination of special hardware and computer instructions.

[0094] While various embodiments of the present invention have been described above, the above descriptions are intended to be illustrative, non-exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is selected to best explain the principles of the embodiments, their practical applications, or technological improvements in the marketplace, or to enable others skilled in the art to understand the embodiments disclosed herein.

[0095] The above are merely optional embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for switching a motor of a circulating water pump of a nuclear power plant, wherein the motor is powered via a frequency converter, characterized in that: include: determining whether to generate a switching instruction for the motor based on a change in electromagnetic field energy conducted by a first predetermined conductor on an input side of the motor of the circulating water pump; In response to detecting the generated switching instruction, acquiring a voltage or current waveform on the motor side and a voltage or current waveform on the grid side, wherein the voltage on the motor side is a superimposed voltage of a residual voltage of the motor and an induced electromotive force generated by the motor; determining an actuation time of a switching command based at least on a comparison of a voltage waveform on the motor side and a voltage waveform on the grid side; as well as In response to the determined action time being reached, the electric grid is switched to directly supplying power to the electric motor.

2. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 1, characterized in that: The change in electromagnetic field energy conducted by the first predetermined conductor indicates a rate of change of the electromagnetic field energy conducted by the first predetermined conductor over time, and the electromagnetic field energy conducted by the first predetermined conductor is determined based on the electric field strength, magnetic field strength and electromagnetic energy flux density conducted by the first predetermined conductor.

3. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 1, characterized in that: The electromagnetic field energy change is a vector, and determining whether to generate a switching instruction for the motor includes: calculating a change in electromagnetic field energy conducted by the first predetermined conductor; determining whether the calculated electromagnetic field energy change indicates a sudden change in electromagnetic field energy within the volumes of the front and rear measurement ends of the first predetermined conductor; and If the calculated electromagnetic field energy variation indicates that the electromagnetic field energy within the volume of the front and rear measuring ends of the first predetermined conductor changes suddenly, a switching instruction for the motor of the circulating water pump of the nuclear power plant is generated.

4. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 3, characterized in that: Generating switching instructions for the motors of the circulating water pumps of a nuclear power plant includes: In response to determining that the electromagnetic field energy change is a negative value, determining that there is a fault in the power supply of the frequency converter; and A switching instruction is generated for a motor of a circulating water pump of a nuclear power plant.

5. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 3, characterized in that: Determining whether to generate a switching instruction for the motor further includes: If the calculated electromagnetic field energy variation indicates that the electromagnetic field energy within the volume of the front and rear measuring ends of the first predetermined conductor is constant, there is no need to generate a switching instruction for the motor of the circulating water pump of the nuclear power plant.

6. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 1, characterized in that: At least based on the comparison between the voltage waveform on the motor side and the voltage waveform on the grid side, determining the action time of the switching instruction includes: Obtaining a first detection current on the motor side via a first predetermined conductor, wherein one end of the first predetermined conductor is connected between the frequency converter and the motor, and the other end of the first predetermined conductor is grounded; Obtaining a second detection current on the grid side via a second predetermined conductor, wherein one end of the second predetermined conductor is connected between the grid and the frequency converter, and the other end of the second predetermined conductor is grounded; Determining a waveform difference between a voltage waveform on the motor side and a voltage waveform on the grid side based on the first detection current waveform and the second detection current waveform; and Based on the determined waveform difference, the action time of the switching instruction is determined.

7. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 6, characterized in that: Also includes: The motor under the test condition is powered off at different voltage amplitudes, so as to record the corresponding time required for the voltage on the motor side to change from the power off to the predetermined threshold, thereby determining the voltage amplitude. The correspondence between value changes and corresponding time.

8. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 7, characterized in that: Determining the action time of the switching instruction based on the determined waveform difference includes: In response to determining that the waveform difference is less than or equal to a predetermined difference threshold, determining a switching timing; and Based on the corresponding relationship between the voltage and voltage amplitude change at the input side of the motor at the time of the inverter power supply failure and the corresponding time, the action time of the switching instruction is determined.

9. The method for switching the motor of the circulating water pump of a nuclear power plant according to claim 1, characterized in that: Also includes: Obtaining the voltage or current waveform on the input side of the motor and the voltage or current waveform on the grid side at the moment of inverter power supply failure; Obtaining a prediction result on whether the switching is successful based on the obtained voltage or current waveform on the input side of the motor and the voltage or current waveform on the grid side via a predetermined verification algorithm; If the obtained prediction result indicates that the switching is successful, performing the switching operation based on the determined action time of the switching instruction; as well as If the prediction result indicates that the switching is unsuccessful, an alarm message is generated.

10. A system for switching the motor of a circulating water pump of a nuclear power plant, characterized in that: include: A frequency converter, used to supply power to the motor of the circulating water pump of the nuclear power plant, the input side of the frequency converter being connected to the power grid via a second switch; The motor, the input side of the motor is connected to the output side of the frequency converter via the third switch, the input side of the motor is connected to one end of the fourth switch, and the other end of the fourth switch is connected to the power grid; A first predetermined conductor is arranged at the input side of the motor and is used to obtain a real-time voltage or current waveform at the input side of the motor; as well as A computing device configured to execute the method for switching a motor of a circulating water pump of a nuclear power plant as claimed in any one of claims 1 to 9.

11. The system for switching the motor of the circulating water pump of a nuclear power plant according to claim 10, characterized in that: Also includes: The second predetermined conductor is configured on the grid side and is used to obtain the real-time voltage or current waveform on the grid side.

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