Automatic valve switching control method and control system for ARE system in nuclear power plant

Abstract

This invention discloses an automatic valve switching control method for an ARE (Automatic Auxiliary Water Supply) system in a nuclear power plant. The ARE system is used for switching between the auxiliary feedwater subsystem and the main feedwater system to control the steam generator water level. It includes a main valve, a small valve, a minimum valve, and a water level controller. The automatic valve switching control method includes the following steps: S1, monitoring and determining whether the operating parameters of the nuclear power plant meet the switching conditions; when the operating parameters meet the switching conditions, outputting a trigger signal; S2, determining whether the small valve and the minimum valve are in normal condition; if so, outputting a valve switching command according to the trigger signal to control the small valve and the minimum valve to perform the corresponding operation. A control system for implementing the above-mentioned automatic valve switching control method is also disclosed. The above-mentioned automatic valve switching control method and control system solve the problems of low automation, long switching time and occupation of overhaul period, high risk of human error, and untimely response in the switching of small and minimum valves in the ARE system.

Description

Technical Field

[0001] This invention relates to the field of nuclear power plant water circuit control technology, and in particular to an automatic valve switching control method and control system for a nuclear power plant ARE system. Background Technology

[0002] In EPR (European Pressurized Reactor) nuclear power units and the Hualong One unit, the ARE (Feedwater Control System) is responsible for supplying water to the steam generator and precisely controlling the water level to ensure unit power and nuclear safety. Depending on the reactor power level, feedwater is controlled through different types of regulating valves. Large valves are used for high-power control, small valves for medium- and low-power conditions and normal operation regulation, and minimal valves for precise water replenishment during low-power conditions, reactor start-up and shutdown processes, and accident conditions. During transient processes such as unit start-up and shutdown or auxiliary plant switching, the feedwater path needs to be switched between small and minimal valves.

[0003] Currently, in the ARE systems of EPR and Hualong One units, the switching between small and minimal valves mainly relies on manual operation. Specifically, when a nuclear power plant experiences a transient situation involving a loss of plant power and a switch to auxiliary transformer power (i.e., a plant-auxiliary switching situation), the main feedwater system (APA) trips due to power failure. At this time, the auxiliary feedwater system (AAD) needs to be activated, and the water supply path should automatically switch from the ARE small valve to the ARE minimal valve. However, the existing control logic has a design flaw involving a 2-second pulse and opening interlock, which prevents the switching from being completed automatically and requires manual judgment and intervention. During the up and down cycles of unit start-up and shutdown, the operator needs to perform valve switching operations at a specific power platform based on power changes. The steps include: confirming that the conditions are met, manually and gradually closing the small valve, manually and gradually opening the minimal valve, and adjusting the minimal valve opening to the target value. The aforementioned switching relies entirely on manual operation, resulting in low automation. Each manual switch takes approximately one hour, directly impacting the critical path of the overhaul, consuming overhaul time, and causing power generation losses. Furthermore, the manual operation involves numerous steps and complex condition judgments, making operators prone to errors under high-voltage transients, thus posing a high risk of human error. During auxiliary plant switching operations, delays in manual judgment and operation, and untimely responses, may lead to excessively low SG (steam generator) water levels, resulting in cooling failure. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention provides an automatic valve switching control method and control system for a nuclear power plant's ARE system. This system solves the problems of low automation, long switching time and time commitment during major overhauls, high risk of human error, and low SG water level due to untimely response when switching between small and very small valves in the ARE system.

[0005] An automatic valve switching control method for a nuclear power plant ARE system, wherein the ARE system is used to switch between the auxiliary feedwater subsystem and the main feedwater system to control the steam generator water level, and the ARE system includes a large valve, a small valve, a minimum valve, and a water level controller; the automatic valve switching control method includes the following steps: S1. Monitor and determine whether the operating parameters of the nuclear power plant meet the switching conditions, and output a trigger signal when the operating parameters meet the switching conditions; S2. Determine whether the small valve and the mini valve are in normal condition. If so, output a valve switching command according to the trigger signal to control the small valve and the mini valve to perform the corresponding operation.

[0006] In one embodiment, the operating parameters include plant auxiliary switching signals, reactor power level, and steam generator water level.

[0007] In one embodiment, step S1, when the operating condition parameters meet the switching conditions, outputs a trigger signal, including: When the operating parameters are detected to meet the first switching condition, a positive trigger signal is output to switch the small valve to the minimum valve. When the operating parameters are detected to meet the second switching condition, a reverse trigger signal is output to switch the minimum valve to the minimum valve.

[0008] In one embodiment, the first switching condition includes detecting a plant auxiliary switching signal or a unit power drop to a preset threshold signal; the second switching condition includes detecting a unit power rebound to above a preset threshold signal or receiving a manually issued reverse switching command.

[0009] In one embodiment, in step S2, when the positive trigger signal is received, the command path between the water level controller and the small valve is cut off, and the small valve is forcibly closed according to the valve positive switching command generated by the positive trigger signal, so that the water level controller adjusts the opening of the small valve. Upon receiving the reverse trigger signal, the valve reverse switching command generated by the reverse trigger signal is used to close the miniature valve, thereby causing the water level controller to adjust the opening degree of the miniature valve.

[0010] In one embodiment, after the valve forward switching command is executed, a locking signal is output to keep the small valve closed.

[0011] In one embodiment, the forced closure of the small valve includes: closing the small valve at a preset ramp rate.

[0012] In one embodiment, upon receiving the positive trigger signal, it is checked whether the miniature valve is in an available state and whether the pump of the auxiliary water supply subsystem is in operation. If so, the command path between the water level controller and the miniature valve is cut off, and the miniature valve is forcibly closed according to the valve positive switching command generated by the positive trigger signal, so that the water level controller adjusts the opening of the miniature valve. If not, an alarm is output or a waiting condition is met or manual confirmation is required.

[0013] In one embodiment, the small valve and the miniature valve have a higher priority in executing the valve switching command than in executing the command issued by the water level controller.

[0014] This invention also discloses a control system for implementing the above-mentioned automatic valve switching control method for a nuclear power plant ARE system. The nuclear power plant ARE system is used to switch between the auxiliary feedwater subsystem and the main feedwater system to control the steam generator water level. The nuclear power plant ARE system includes a large valve, a small valve, a minimum valve, and a water level controller. The control system includes: The operating condition identification module is used to monitor and determine whether the operating condition parameters of the nuclear power plant meet the switching conditions, and outputs a trigger signal when the operating condition parameters meet the switching conditions. The instruction switching module is used to determine whether the small valve and the mini valve are in normal state. If so, it outputs a valve switching instruction according to the trigger signal. The valve command output module is used to control the small valve and the mini valve to perform corresponding operations according to the valve switching command.

[0015] The automatic valve switching control method and control system of the nuclear power plant ARE system implementing this invention sets up an automatic identification and switching control logic independent of the water level controller. When the operating parameters are found to meet the switching conditions, a trigger signal is generated. After checking the availability of the small valve and the minimum valve, the small valve and the minimum valve are controlled to perform corresponding operations. This can solve the problem that during the transient switching of auxiliary equipment, the water level controller outputs a full-open command for the small valve due to the drop in the steam generator water level, which leads to the failure of automatic switching between the small valve and the minimum valve. It replaces manual operation, improves the automation level of the small valve and the minimum valve switching in the ARE system, shortens the judgment and switching operation time, reduces the risk of human error and reduces the occupation of the overhaul period, and can respond to the problem of the steam generator water level drop in a timely manner to ensure the cooling effect. Attached Figure Description

[0016] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort. In the drawings: Figure 1 This is a flowchart of an automatic valve switching control method for a nuclear power plant ARE system according to an embodiment of the present invention; Figure 2 This is a control logic diagram for judging operating parameters in one embodiment of the present invention; Figure 3 This is a control logic diagram for switching instruction output in one embodiment of the present invention; Figure 4 This is a control logic diagram of the large valve operating in one embodiment of the present invention; Figure 5 This is a control logic diagram of the small valve operating in one embodiment of the present invention; Figure 6 This is a control logic diagram of the minimum valve operation in one embodiment of the present invention. Detailed Implementation

[0017] To provide a clearer understanding of the technical features, objectives, and effects of this invention, specific embodiments are now described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "front," "rear," "upper," "lower," "left," "right," "longitudinal," "horizontal," "vertical," "horizontal," "top," "bottom," "inner," "outer," "head," and "tail" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing this technical solution and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on this invention.

[0018] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "linking," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0019] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will understand that the invention can be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods are omitted so as not to obscure the description of the invention with unnecessary detail.

[0020] Example 1 This invention discloses an automatic valve switching control method for an ARE (Automatic Feedwater System) in a nuclear power plant, used for switching between small and minimal valves in the ARE system, particularly for switching between small and minimal valves in the feedwater path during transient processes such as unit start-up / shutdown or auxiliary system switching. The ARE system used in this automatic valve switching control method is employed to switch between the auxiliary feedwater subsystem and the main feedwater system to control the steam generator water level. The ARE system includes large valves, small valves, minimal valves, and a water level controller. Additionally, the ARE system also includes a large valve controller, a small valve controller, and a minimal valve controller that correspond one-to-one with the large valves, small valves, and minimal valves. When there are no normal operating conditions such as unit start-up or shutdown or plant auxiliary switching, the water level controller controls the valve controllers (i.e., large valve controller, small valve controller, and minimum valve controller) to adjust the opening of each valve (i.e., large valve, small valve, and minimum valve) so that the water level of the steam generator is stable within the preset range. When there is a plant auxiliary switching condition that requires switching the small valve and minimum valve or a change in unit power, the main feedwater subsystem trips due to power failure. Water needs to be supplied to the secondary side of the steam generator through the auxiliary feedwater subsystem to remove the core decay heat and prevent the core from overheating and being damaged.

[0021] Please see Figure 1 The automatic valve switching control method in this embodiment includes the following steps: S1. Monitor and determine whether the operating parameters of the nuclear power plant meet the switching conditions, and output a trigger signal when the operating parameters meet the switching conditions.

[0022] In this embodiment, the operating parameters include the auxiliary power plant switching signal, reactor power level, and steam generator water level. The auxiliary power plant switching signal refers to the signal generated when the nuclear power plant loses its auxiliary power and switches to auxiliary power supply. This signal originates from the differential or overcurrent signal generated by the protection action of the auxiliary power plant transformer (station service transformer), or from a manually input switching command during testing or maintenance. The reactor power level is the unit's power value, and the steam generator water level reflects the current cooling conditions of the nuclear power unit. By monitoring these operating parameters, the operating conditions requiring a switchover can be automatically identified.

[0023] In step S1, when the operating parameters meet the switching conditions, a trigger signal is output, including: When the operating parameters are detected to meet the first switching condition, a positive trigger signal is output to switch the small valve to the minimum valve. When the operating parameters are detected to meet the second switching condition, a reverse trigger signal is output to switch the minimum valve to the minimum valve.

[0024] In this embodiment, the first switching condition includes detecting a plant auxiliary switching signal (condition A) or a unit power drop to a preset threshold signal (condition B). Detecting a plant auxiliary switching signal includes detecting a bus voltage switch or a circuit breaker status change; a unit power drop to a preset threshold signal, such as a unit power drop below 4% of rated power, can be determined as unit start-up / shutdown or plant auxiliary switching. When either condition A or condition B is met, the automatic switching process is triggered, generating a valve forward switching command. It should be noted that in practical applications, when a trigger command manually input by the operator is received, the switching process can also be entered manually. This allows for manual entry into the switching process by retaining a manual interface as a backup, ensuring that even if the system malfunctions or it is difficult to obtain plant auxiliary switching signals and unit power signals, the switching process can still be manually forced. The second switching condition includes detecting a unit power rebound to above a preset threshold or receiving a manually issued reverse switching command.

[0025] S2. Determine whether the small valve and the mini valve are in normal condition. If so, output a valve switching command according to the trigger signal to control the small valve and the mini valve to perform the corresponding operation.

[0026] In this embodiment, before executing the valve switching command, it is determined whether the small valve and the mini valve are in a normal state, which provides a prerequisite for the subsequent valve switching operation and avoids sending the command when the mini valve and the mini valve are in an abnormal state, which would cause the system switching to fail.

[0027] In step S2, when a positive trigger signal is received, the command path between the water level controller and the small valve is cut off, and the small valve is forcibly closed according to the valve forward switching command generated by the positive trigger signal, so that the water level controller adjusts the opening of the miniature valve; when a reverse trigger signal is received, the miniature valve is closed according to the valve reverse switching command generated by the reverse trigger signal, so that the water level controller adjusts the opening of the small valve.

[0028] When a positive trigger signal is generated, the system meets the first switching condition. Before switching, since the valve controllers corresponding to each valve are controlled by the water level controller, in order to switch between the small valve and the mini valve, the instruction path between the small valve controller and the water level controller must first be cut off. That is, the water level controller's command to open the small valve is blocked, the water level controller interference is blocked, and logical conflicts are prevented so as to force the control of the small valve.

[0029] In this embodiment, upon receiving a positive trigger signal, it checks whether the miniature valve is available and whether the pump in the auxiliary feedwater subsystem is running. If so, the command path between the water level controller and the miniature valve is cut off, and the miniature valve is forcibly closed according to the valve forward switching command generated by the positive trigger signal, causing the water level controller to adjust the opening of the miniature valve. If not, an alarm is output, or a waiting condition is met or manual confirmation is required, so that the forward switching process can proceed when the miniature valve is available and the auxiliary feedwater subsystem is running. In other words, detecting the availability of the miniature valve and the running status of the auxiliary feedwater subsystem are prerequisites for issuing valve forward switching commands to the valve controllers of each valve. If these prerequisites are not met, a forced switch cannot be performed. In this embodiment, by detecting the availability of the miniature valve and the running status of the auxiliary feedwater subsystem, it can be determined whether the system configuration meets the requirements for transferring feedwater circuit control from the miniature valve to the miniature valve, avoiding the problem of low steam generator water level caused by the miniature valve being unavailable or the auxiliary feedwater subsystem not running when transferring feedwater circuit control to the miniature valve. In addition, when detecting the operating status of the auxiliary water supply subsystem, it is also determined that the auxiliary water supply subsystem is operating within the safe characteristic range to prevent overflow tripping.

[0030] When executing the valve forward switching command, the control modes of the large and small valves are switched to "forced automatic" mode. At this time, a forced shut-off command is output to the small valve controller, causing it to close the small valve. Simultaneously, a forced shut-off command is output to the large valve controller, causing it to close the large valve. Thus, under this condition, the water supply circuit can only be controlled via the minimum valve. The ultimate goal of closing the large and small valves is to achieve a 0% opening degree, meaning both valves are fully closed. Forced shut-off of the small valve includes closing it at a preset ramp rate, thus preventing a sudden drop in flow within the water supply circuit and achieving a smooth switching process.

[0031] Furthermore, in this embodiment, a seamless switching module interface is used to control the small valve controller, enabling the small valve controller to close the small valve at a preset ramp rate. This ensures that the steam generator liquid level does not experience drastic disturbances during the switching process, achieving a smooth transition. In this embodiment, during the forced closure of the small valve, a command is simultaneously output to the minimum valve controller, switching the minimum valve control mode from standby or manual to automatic adjustment. This allows the minimum valve controller to receive commands from the water level controller and automatically adjust the opening of the minimum valve according to the deviation of the steam generator water level to maintain a stable water level in the steam generator.

[0032] After the valve forward switching command is executed, a locking signal is output to keep the small valve closed. Thus, following this forward switching process, the feedwater circuit is continuously controlled by the minimum valve until the system operating parameters change, allowing for independent feedwater control via the minimum valve during plant auxiliary system switching or unit start-up / shutdown conditions. In this condition, water replenishment is implemented through the minimum valve path, ensuring the pumps in the auxiliary feedwater subsystem operate within safe operating ranges and preventing over-flow tripping. In this embodiment, using a status signal instead of a pulse signal to maintain the small valve's switching state avoids failure issues.

[0033] When the operating parameters meet the second switching condition, check whether the small valve is in normal condition. If the small valve is in normal condition, execute the valve reverse switching command. For example, when the unit power is detected to rise to more than 4% of the rated power, or when the operator manually issues a reverse switching command, a valve reverse switching command is generated. The valve action controlled by the valve reverse switching command is opposite to the valve action controlled by the valve forward switching command. That is, when receiving the valve reverse switching command, the small valve controller receives the control signal from the water level controller and controls the small valve to enter the automatic control process. At the same time, it gradually closes the mini valve, so that the mini valve switches back to the standby state.

[0034] In this embodiment, the priority of the valve switching command executed by the small valve and the mini valve is higher than the priority of the command issued by the water level controller. Thus, as long as the valve controller receives a valve switching command, it executes the corresponding valve control action according to the command. By identifying factory auxiliary switching and low-power operating conditions as independent operating conditions that trigger the small valve to switch to the mini valve, and designing a dedicated automatic switching logic based on these independent operating conditions, unintended coupling can be avoided, switching reliability can be improved, and decoupling from the normal water level regulation logic can be achieved.

[0035] It should be noted that, in this embodiment, the nuclear power plant ARE system includes a PID water level regulation loop and a valve switching control loop. The large valve controller, small valve controller, minimum valve controller, water level controller, and water level detector for detecting the steam generator together form the PID water level regulation loop to accurately control the steam generator water level under normal operating conditions (i.e., without auxiliary plant switching or unit power reduction). The control process of the valve switching control loop is executed by the automatic valve switching control method of the nuclear power plant ARE system in this embodiment. The implementation of this automatic valve switching control method is independent of the PID water level regulation loop, which can detect the system operating conditions in real time and realize the switching between the small valve and the minimum valve when abnormal operating conditions (auxiliary plant switching and unit power reduction) occur.

[0036] The following combination Figures 1-6 This section describes the control process of the automatic valve switching control method in the ARE system of a nuclear power plant in a specific example.

[0037] Specifically, a trigger signal is generated when either the operator's automatic switching request or the signal indicating that the unit power is less than 4% of the rated power is triggered. Figure 2 The diagram shows a PICS trigger (Process Information and Control System Trigger Signal). PICS triggering has two directions: one is a small valve switching to a minimum valve, and the other is a minimum valve switching to a small valve. That is, a PICS trigger is generated when both the first and second switching conditions are met. Under normal conditions for the minimum valve, small valve, and large valve, both "Signal Plant Auxiliary Switching" and "PICS Trigger (Small Valve Switching to Minimum Valve)" signals are allowed to be sent to downstream modules or systems; or, depending on the content of the PICS trigger (small valve switching to minimum valve or minimum valve switching to small valve), it is sent to downstream modules or systems. Figure 3 The '&' in the code represents an AND gate in logic. It outputs 1 only if both input conditions are met; otherwise, it outputs 0. (See also...) Figure 4 If "Signal switched to minimum valve" is 1, then the Y terminal of the main valve controller is taken from 0% of the X1 terminal, and the XD signal is taken from the Y terminal, so XD is 0%, meaning the main valve is closed. (XD represents the regulation signal received by the main valve, fAMd indicates forced automatic control; if there is a plant auxiliary switching signal, the main valve will be forced to switch to automatic control). Please refer to [link / reference]. Figure 5If switching from the minimum valve to the minimum valve, the "Signal Switch to Minimum Valve" becomes 1. The Y terminal of switching module 2 is taken from X2 (50%), and the XD terminal of the minimum valve's valve control module receives a 50% opening (a pulse signal, maintained for 1 second). After 1 second, the XD terminal receives the X1 terminal signals from the two upstream switching modules, which represent the required opening for water level regulation of the steam generator. This is because the minimum valve regulation lags; during switching, a preset opening is given to the minimum valve first, and then the system regulation is responded to. If switching from the minimum valve to the minimum valve, the "Signal Switch to Minimum Valve" becomes 1. The Y terminal of switching module 1 is taken from X2 (0%), and the Y terminal of switching module 2 is taken from X1. That is, the XD terminal of the minimum valve controller receives a 0% opening to control the minimum valve to close. Please refer to [link to relevant documentation]. Figure 6 When the auxiliary signal is triggered, according to Figure 3 The logic triggers signal auxiliary switching (short pulse) and signal cut-to-minimum valve (long pulse), causing... Figure 6 The Y value of the switching module 4 is X2 (80%), which means the minimum valve opening is 80%. After the pulse, the minimum valve opening is taken from the water level requirement of SG (steam generator). In other words, when the small valve switches to the minimum valve, the initial opening of the minimum valve is 80%, and the subsequent opening is determined by the water level requirement of the steam generator.

[0038] Compared with existing manual switching methods, the automatic valve switching control method of the nuclear power plant ARE system in this embodiment has the following advantages: 1) Manual switching relies on human judgment and operation; this solution eliminates the risk of human error and improves the level of automation through automatic system identification and execution. 2) Manual switching requires judgment, operation, and confirmation, and the switching time is about 1 hour; this solution is executed automatically and only takes a few seconds to tens of seconds to complete the switching, shortening the critical path of major overhaul and increasing power generation revenue. 3) The manual switching method relies on the operator's timely judgment under high pressure transients when responding to plant auxiliary switching; this solution is automatically executed immediately after the signal is triggered, and its timely response can prevent the evaporator water level from being too low. 4) Existing automatic logic fails due to timing conflicts; this solution uses dedicated switching logic to operate independently, without interference, fundamentally solving the automatic failure problem. 5) Manual switching mode lacks automatic protection and poses a risk of overflow. This solution precisely controls the flow rate through a minimal valve path to prevent overload tripping of the auxiliary feedwater subsystem pumps, ensuring automatic, timely, and reliable activation of the auxiliary feedwater subsystem during plant auxiliary switching conditions, guaranteeing the removal of residual heat from the reactor core, and improving safety. 6) Manual switching is cumbersome and requires multiple people to coordinate; this solution can be put into operation with one click or triggered fully automatically, which can reduce the workload of operators and is in line with the trend of digital operation of nuclear power plants. 7) The manual switching method can only be verified through actual working conditions; the dedicated logic module of this solution can be simulated and tested offline, which is convenient for verification and maintenance.

[0039] Example 2 This invention also discloses a control system for implementing the above-mentioned automatic valve switching control method of the ARE system in a nuclear power plant. The ARE system is used to switch between the auxiliary feedwater subsystem and the main feedwater system to control the steam generator water level. The ARE system includes large valves, small valves, minimal valves, and water level controllers, as well as large valve controllers, small valve controllers, and minimal valve controllers that control the large valves, small valves, and minimal valves one-to-one. Under normal operating conditions such as unit start-up / shutdown or auxiliary system switching, the water level controller controls each valve controller (i.e., large valve controller, small valve controller, minimal valve controller) to adjust the opening of each valve (i.e., large valve, small valve, minimal valve) to keep the steam generator water level stable within a preset range. When an auxiliary system switching condition requiring switching of small valves and minimal valves occurs, the main feedwater subsystem trips due to power failure, and water needs to be supplied to the secondary side of the steam generator through the auxiliary feedwater subsystem to remove core decay heat and prevent core overheating damage.

[0040] The automatic valve switching control system of the ARE system in a nuclear power plant includes an operating condition identification module, a command switching module, and a valve command output module. The operating condition identification module monitors and determines whether the operating condition parameters of the nuclear power plant meet the switching conditions, and outputs a trigger signal when the operating condition parameters meet the switching conditions. The command switching module determines whether the small valve and the mini valve are in normal condition. If so, it outputs a valve switching command according to the trigger signal. The valve command output module controls the small valve and the mini valve to perform corresponding operations according to the valve switching command, so as to control the opening degree of the corresponding valve. It should be noted that, in this embodiment, the nuclear power plant ARE system includes a PID water level regulation loop and a valve switching control loop. The large valve controller, small valve controller, minimum valve controller, water level controller, and water level detector for monitoring the steam generator together form the PID water level regulation loop to accurately control the steam generator water level under normal operating conditions (i.e., without auxiliary plant switching or unit power reduction). The operating condition identification module, command switching module, and valve command output module together form the automatic valve switching control system of the nuclear power plant ARE system, that is, the valve switching control loop. In other words, the automatic valve switching control system of the nuclear power plant ARE system in this embodiment is part of the nuclear power plant ARE system. This valve switching control loop is independent of the PID water level regulation loop, can detect system operating conditions in real time, and realizes the switching between the small valve and the minimum valve when abnormal operating conditions (auxiliary plant switching and unit power reduction) occur.

[0041] In this embodiment, the operating parameters include the auxiliary power plant switching signal, reactor power level, and steam generator water level. The auxiliary power plant switching signal refers to the signal generated when the nuclear power plant loses its auxiliary power and switches to auxiliary power supply. This signal originates from the differential or overcurrent signal generated by the protection action of the auxiliary power plant transformer (station service transformer), or from a manually input switching command during testing or maintenance. The reactor power level is the unit's power value, and the steam generator water level reflects the current cooling conditions of the nuclear power unit. By monitoring these operating parameters, the operating conditions requiring a switchover can be automatically identified.

[0042] The switching conditions include a first switching condition and a second switching condition. The first switching condition includes detecting a plant auxiliary switching signal (condition A) or a unit power drop to a preset threshold signal (condition B). Detecting a plant auxiliary switching signal includes detecting a bus voltage switch or a circuit breaker status change; a unit power drop to a preset threshold signal, such as a unit power drop below 4% of rated power, can be identified as unit start-up / shutdown or plant auxiliary switching. When either condition A or condition B is met, the automatic switching process is triggered, generating a valve forward switching command. It should be noted that in practical applications, when a trigger command manually input by the operator is received, the switching process can also be entered manually. This allows for manual entry into the switching process by retaining a manual interface as a backup, ensuring that the switching process can still be manually forced in case of system failure or difficulty in obtaining plant auxiliary switching signals and unit power signals. The second switching condition includes detecting a unit power rebound to above a preset threshold or receiving a manually issued reverse switching command.

[0043] When the operating parameters meet the first switching condition, a positive trigger signal is output to cut off the command path between the water level controller and the small valve. Based on the valve positive switching command generated by the positive trigger signal, the small valve is forcibly closed, causing the water level controller to adjust the opening of the minimum valve. When the valve positive switching command is generated, the system meets the first switching condition. Before switching, since the valve controllers corresponding to each valve are controlled by the water level controller, in order to achieve the switching between the small valve and the minimum valve, it is necessary to first cut off the command path between the small valve controller and the water level controller. This means shielding the water level controller from issuing commands to open the small valve, shielding the water level controller from interference, preventing logical conflicts, and thus forcibly controlling the small valve.

[0044] The disconnection of the command path between the water level controller and the small valve is executed by the command switching module. Before disconnecting the command path, the command switching module checks whether the small valve is available and whether the pumps of the auxiliary water supply subsystem are running. If the small valve is available and the pumps of the auxiliary water supply subsystem are running, the command switching module disconnects the command path between the water level controller and the small valve. Otherwise, an alarm is output, or a waiting condition is met or manual confirmation is required, so that the switching process can proceed only when the small valve is available and the auxiliary water supply subsystem is running. In other words, the detection of the availability of the small valve and the running status of the auxiliary water supply subsystem are prerequisites for issuing positive valve switching commands to the valve controllers of each valve. If these prerequisites are not met, a forced switching cannot be performed. In this embodiment, by detecting the availability of the minimum valve and the operating status of the auxiliary feedwater subsystem, it can be determined whether the system configuration meets the requirements for transferring feedwater circuit control from the minimum valve to the minimum valve. This avoids the problem of excessively low steam generator water level caused by the minimum valve being unavailable or the auxiliary feedwater subsystem not operating when transferring feedwater circuit control to the minimum valve. In addition, when detecting the operating status of the auxiliary feedwater subsystem, it is also determined that the auxiliary feedwater subsystem is operating within the safe characteristic range to prevent over-flow tripping.

[0045] When executing a forward valve switching command, the valve command output module switches the control mode of both the large and small valves to "forced automatic" mode. At this time, it outputs a forced shut-off command to the small valve controller, causing the small valve controller to close the small valve. Simultaneously, it outputs a forced shut-off command to the large valve controller, causing the large valve controller to close the large valve. This ensures that under this condition, the feedwater circuit can only be controlled via the minimum valve. The ultimate goal of closing both the large and small valves is to achieve a 0% opening degree, meaning both valves are fully closed. Forced shut-off of the small valve according to the forward valve switching command includes closing the small valve at a preset ramp rate. This avoids a sudden drop in flow rate within the feedwater circuit, achieving a smooth switching process. Furthermore, in this embodiment, a smooth switching module interface is used to control the small valve controller, enabling it to close the small valve at a preset ramp rate, ensuring that the steam generator level does not experience drastic disturbances during the switching process, achieving a smooth transition.

[0046] In this embodiment, during the forced closure of the small valve, a command is simultaneously output to the miniature valve controller to switch the miniature valve control mode from standby or manual to automatic adjustment. This allows the miniature valve controller to receive the command from the water level controller and automatically adjust the opening of the miniature valve according to the deviation of the steam generator water level to maintain the stability of the steam generator water level.

[0047] It should be noted that after the valve forward switching command is executed, a locking signal is output to keep the small valve closed. This ensures that the feedwater circuit is continuously controlled by the minimum valve after the switching process until the system operating parameters change, allowing for independent feedwater control via the minimum valve during plant auxiliary switching or unit start-up / shutdown conditions. In this case, water replenishment is implemented through the minimum valve path, ensuring that the pumps in the auxiliary feedwater subsystem operate within safe operating ranges and preventing over-flow tripping. In this embodiment, using a status signal instead of a pulse signal to maintain the switching state of the small valve avoids failure issues.

[0048] When the operating condition identification module detects that the operating condition parameters meet the second switching condition, it generates a reverse trigger signal. The command switching module checks whether the small valve is in a normal state, and if so, outputs a valve reverse switching command. The valve command output module receives the valve reverse switching command and closes the mini valve, causing the water level controller to adjust the opening of the small valve. For example, when the unit power is detected to have risen to more than 4% of the rated power, or when the operator manually issues a reverse switching command, a valve reverse switching command is generated. The valve action controlled by this valve reverse switching command is the opposite of the valve action controlled by the valve forward switching command. That is, upon receiving the valve reverse switching command, the small valve controller receives the control signal from the water level controller, controls the small valve to enter the automatic control process, and simultaneously gradually closes the mini valve, causing the mini valve to switch back to standby mode.

[0049] In this embodiment, the priority of the valve controller executing valve switching commands is higher than the priority of executing commands issued by the water level controller. Thus, as long as the valve controller receives a valve switching command, it executes the corresponding valve control according to the command. By identifying factory auxiliary switching and low-power operating conditions as independent operating conditions that trigger the switching of small valves to extremely small valves, and designing dedicated automatic switching logic based on these independent operating conditions, unintended coupling can be avoided, switching reliability can be improved, and decoupling from normal water level regulation logic can be achieved.

[0050] The operation process of the automatic valve switching control system of the nuclear power plant ARE system in this embodiment is the same as that in Embodiment 1. Figures 1-6 The control process of the automatic valve switching control method shown is exactly the same, and can be found in the relevant description of Embodiment 1, which will not be repeated here.

[0051] The automatic valve switching control method and control system of the nuclear power plant ARE system implementing this invention sets up an automatic identification and switching control logic independent of the water level controller. When the operating parameters are found to meet the switching conditions, a trigger signal is generated. After checking the availability of the small valve and the minimum valve, the small valve and the minimum valve are controlled to perform corresponding operations. This can solve the problem that during the transient switching of auxiliary equipment, the water level controller outputs a full-open command for the small valve due to the drop in the steam generator water level, which leads to the failure of automatic switching between the small valve and the minimum valve. It replaces manual operation, improves the automation level of the small valve and the minimum valve switching in the ARE system, shortens the judgment and switching operation time, reduces the risk of human error and reduces the occupation of the overhaul period, and can respond to the problem of the steam generator water level drop in a timely manner to ensure the cooling effect.

[0052] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. An automatic valve switching control method for a nuclear power plant ARE system, wherein the nuclear power plant ARE system is used to switch between the auxiliary feedwater subsystem and the main feedwater system to control the steam generator water level, and the nuclear power plant ARE system includes a large valve, a small valve, a minimum valve, and a water level controller; characterized in that, The automatic valve switching control method includes the following steps: S1. Monitor and determine whether the operating parameters of the nuclear power plant meet the switching conditions, and output a trigger signal when the operating parameters meet the switching conditions; S2. Determine whether the small valve and the mini valve are in normal condition. If so, output a valve switching command according to the trigger signal to control the small valve and the mini valve to perform the corresponding operation.

2. The automatic valve switching control method according to claim 1, characterized in that, The operating parameters include plant auxiliary switching signals, reactor power level, and steam generator water level.

3. The automatic valve switching control method according to claim 2, characterized in that, In step S1, when the operating parameters meet the switching conditions, a trigger signal is output, including: When the operating parameters are detected to meet the first switching condition, a positive trigger signal is output to switch the small valve to the minimum valve. When the operating parameters are detected to meet the second switching condition, a reverse trigger signal is output to switch the minimum valve to the minimum valve.

4. The automatic valve switching control method according to claim 3, characterized in that, The first switching condition includes detecting a plant auxiliary switching signal or a unit power drop to a preset threshold signal; the second switching condition includes detecting a unit power rebound to above a preset threshold signal or receiving a manually issued reverse switching command.

5. The automatic valve switching control method according to claim 3, characterized in that, In step S2, upon receiving the positive trigger signal, the command path between the water level controller and the small valve is cut off, and the small valve is forcibly closed according to the valve positive switching command generated by the positive trigger signal, so that the water level controller adjusts the opening of the minimum valve. Upon receiving the reverse trigger signal, the valve reverse switching command generated by the reverse trigger signal is used to close the miniature valve, thereby causing the water level controller to adjust the opening degree of the miniature valve.

6. The automatic valve switching control method according to claim 5, characterized in that, After the valve forward switching command is executed, a locking signal is output to keep the small valve closed.

7. The automatic valve switching control method according to claim 5, characterized in that, The forced closure of the small valve includes: closing the small valve at a preset ramp rate.

8. The automatic valve switching control method according to claim 5, characterized in that, Upon receiving the positive trigger signal, check whether the miniature valve is in an available state and whether the pump of the auxiliary water supply subsystem is in operation. If so, cut off the command path between the water level controller and the miniature valve, and forcibly close the miniature valve according to the valve positive switching command generated by the positive trigger signal, so that the water level controller adjusts the opening of the miniature valve. If not, output an alarm or wait for the condition to be met or for manual confirmation.

9. The automatic valve switching control method according to claim 1, characterized in that, The priority of the small valve and the miniature valve in executing the valve switching command is higher than the priority of executing the command issued by the water level controller.

10. A control system for implementing the automatic valve switching control method of the nuclear power plant ARE system according to any one of claims 1-9, wherein the nuclear power plant ARE system is used to realize the switching between the auxiliary feedwater subsystem and the main feedwater system to control the steam generator water level, and the nuclear power plant ARE system includes a large valve, a small valve, a minimum valve, and a water level controller, characterized in that, The control system includes: The operating condition identification module is used to monitor and determine whether the operating condition parameters of the nuclear power plant meet the switching conditions, and outputs a trigger signal when the operating condition parameters meet the switching conditions. The instruction switching module is used to determine whether the small valve and the mini valve are in normal state. If so, it outputs a valve switching instruction according to the trigger signal. The valve command output module is used to control the small valve and the mini valve to perform corresponding operations according to the valve switching command.

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