Control methods and control systems for the steam pressure at the inlet of high-temperature gas-cooled reactor turbines

Abstract

This invention proposes a method and control system for controlling the steam pressure before the turbine of a high-temperature gas-cooled reactor, belonging to the field of high-temperature gas-cooled reactor automatic control technology. The control method includes: generating an open-loop control command when one of the reactors experiences an emergency shutdown and rapid unloading operation; superimposing the open-loop control command with a closed-loop control command from the pressure controller to form a general valve control command for the turbine; and adjusting the turbine valve opening in advance according to the general valve control command. This invention's control method combines rapid coarse adjustment with fine-grained closed-loop automatic adjustment, ensuring that the steam pressure before the turbine is maintained near the pressure setpoint, reducing large fluctuations in steam pressure, and thus ensuring the safe and stable operation of the unit.

Description

Technical Field

[0001] This invention belongs to the field of automatic control technology for high-temperature gas-cooled reactors, specifically relating to a method and control system for controlling the steam pressure at the turbine inlet of a high-temperature gas-cooled reactor. Background Technology

[0002] Pressurized water reactor (PWR) nuclear power plants employ a reactor-following-machine control mode. The steam pressure before the turbine operates in a sliding pressure mode, without separate steam pressure control; the steam pressure changes with the unit's load. High-temperature reactors (HTWRs) use a turbine-following-reactor control mode, where the reactor controls the unit's power output, and the turbine controls the steam pressure before the turbine. The turbine control system (DEH) pressure controller achieves constant steam pressure operation before the turbine, and the generator output power varies with the reactor power. HTWRs are dual-module configurations, with two reactors supporting one turbine. Both evaporators are direct-flow type with very small energy storage. During startup, the evaporator outlet steam pressure is controlled by the separator inlet regulating valve of the reactor start-up / shutdown system; during power operation, the pressure is maintained stable by the turbine bypass valve. Steam is supplied via a main pipe. During dual-power operation, the two evaporators are directly connected to the turbine via the main steam pipe. Changes in the steam pressure before the turbine are directly reflected in the evaporator outlet pressure. Drastic changes in the evaporator outlet pressure are very harmful to the operation of the evaporator. Therefore, it is necessary to ensure the stability of the steam pressure before the turbine under any operating conditions.

[0003] Under normal operating conditions, the steam pressure change at the turbine inlet is smaller than that under transient operating conditions. After the pressure control mode is activated, the turbine control valve regulates the steam pressure according to the closed-loop control output of the pressure controller.

[0004] When both reactors are operating at full power, an emergency shutdown of one reactor occurs, known as a rapid unloading operation. During this transient condition, the turbine steam flow rate suddenly decreases. The feedback control of the pressure controller struggles to cope with the sudden change in turbine inlet steam pressure. Stabilizing the turbine inlet steam pressure near the setpoint, and if the deviation between the actual pressure and the setpoint exceeds 50% of the rated pressure, closed-loop automatic steam pressure control becomes impossible. This leads to turbine valve oscillation and unstable generator load. The stability of the turbine inlet steam pressure is also crucial for the safe operation of the evaporator and is an essential condition for the stable operation of the high-temperature reactor. Therefore, solving the problem of turbine inlet steam pressure control under transient conditions is critical. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art, and to provide a method and control system for controlling the steam pressure at the front end of a high-temperature gas-cooled reactor turbine.

[0006] In one aspect, the present invention provides a method for controlling the steam pressure at the inlet of a high-temperature gas-cooled reactor turbine, the method comprising:

[0007] When one of the reactors experiences an emergency shutdown and rapid unloading operation, an open-loop control command is generated;

[0008] The open-loop control command is superimposed with the closed-loop control command of the pressure controller to form the general control command for the turbine valves;

[0009] Adjust the turbine valve opening in advance according to the general control valve command.

[0010] Optionally, the open-loop control command includes:

[0011] Obtain the actual deviation between the actual steam pressure in front of the steam turbine and the pressure setpoint;

[0012] When the actual deviation is less than or equal to the preset deviation, the expected reduction in the opening of the turbine control valve is determined based on the actual deviation, thus forming an open-loop control command.

[0013] Optionally, the turbine control valve opening degree corresponds to the percentage of steam flow.

[0014] Optionally, the open-loop control command further includes:

[0015] Corrections are made to the actual deviation between the turbine control valve opening performance and the steam flow rate at the turbine inlet of the high-temperature gas-cooled reactor.

[0016] Optionally, the control method further includes:

[0017] The open-loop control command decreases as the actual deviation decreases, and when the open-loop control command is less than the preset command, the open-loop control is disconnected after a delay.

[0018] Optionally, the open-loop control command is a percentage of steam flow, and the preset command is 0.5.

[0019] Optionally, when the actual deviation is greater than the preset deviation, the pressure controller exits closed-loop control.

[0020] In another aspect, the present invention provides a control system for the steam pressure at the inlet of a high-temperature gas-cooled reactor turbine, the control system comprising:

[0021] The open-loop control command generation unit is used to generate open-loop control commands when one of the reactors experiences an emergency shutdown and rapid unloading operation.

[0022] The overall control valve command generation unit is used to superimpose the open-loop control command with the output command of the pressure controller to form the overall control valve command of the turbine valve;

[0023] The valve opening adjustment unit adjusts the turbine valve opening in advance according to the general control valve command.

[0024] Optionally, the open-loop control command forming unit is specifically used for:

[0025] Obtain the actual deviation between the actual steam pressure in front of the steam turbine and the pressure setpoint;

[0026] When the actual deviation is less than or equal to the preset deviation, the expected reduction in the opening of the turbine control valve is determined based on the actual deviation, thus forming an open-loop control command.

[0027] Optionally, the control system further includes an open-loop control cutoff unit, used to delay and cut off the open-loop control when the open-loop control command is less than a preset command.

[0028] This invention proposes a method and control system for controlling the steam pressure before the turbine of a high-temperature gas-cooled reactor. The control method includes: generating an open-loop control command when one of the reactors experiences an emergency shutdown and rapid unloading operation; superimposing the open-loop control command with a closed-loop control command from the pressure controller to form a general valve control command for the turbine; and adjusting the turbine valve opening in advance according to the general valve control command. This invention's control method combines rapid coarse adjustment with fine-grained closed-loop automatic adjustment, ensuring that the steam pressure before the turbine is maintained near the pressure setpoint, reducing large fluctuations in steam pressure, and thus ensuring the safe and stable operation of the unit. Attached Figure Description

[0029] Figure 1 This is a flowchart illustrating a method for controlling the steam pressure at the inlet of a high-temperature gas-cooled reactor turbine according to an embodiment of the present invention.

[0030] Figure 2 This is a block diagram illustrating the steam pressure control principle of the machine front according to another embodiment of the present invention;

[0031] Figure 3 This is a diagram showing the steam pressure control of the turbine during the rapid unloading operation according to another embodiment of the present invention;

[0032] Figure 4 This is a diagram showing the steam pressure control at the machine front under normal operating conditions according to another embodiment of the present invention;

[0033] Figure 5 This is a schematic diagram of the control system for the steam pressure at the turbine inlet of a high-temperature gas-cooled reactor, according to another embodiment of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the protection scope of the present invention.

[0035] It should be noted that during the instantaneous operation of dual-reactor power, when a rapid unloading action occurs during an emergency shutdown of one reactor, the corresponding evaporator isolation valve closes and the outlet isolation valve closes with a delay. Since the evaporator does not store energy, the water inside the evaporator evaporates quickly after the isolation valve at the evaporator inlet closes, causing significant fluctuations in the main steam header and the steam pressure before the turbine, with the steam header pressure dropping rapidly. To address this, in this embodiment, an open-loop control loop is added to maintain stable steam header pressure. This loop works in conjunction with the closed-loop automatic control of the pressure controller to generate a general control valve command, enabling early and rapid action on the turbine valves. The control process of the turbine valves based on the open-loop control loop and the pressure controller will be described below.

[0036] like Figures 1 to 4 As shown, one aspect of the present invention provides a method S100 for controlling the steam pressure before a high-temperature gas-cooled reactor turbine, comprising steps S110 to S130:

[0037] S110: When one of the reactors experiences an emergency shutdown and rapid unloading operation, an open-loop control command is generated.

[0038] Specifically, such as Figure 2 Zhihe Figure 3 As shown, during dual-reactor operation, when a reactor experiences an emergency shutdown and rapid unloading operation, it is necessary to calculate the actual deviation between the actual steam pressure in front of the turbine and the pressure setpoint. If the actual deviation is less than the preset deviation, the actual deviation is converted into the turbine control valve opening to form an open-loop control command.

[0039] In this embodiment, the open-loop control command is equivalent to feedforward control. It is converted into a command for the valve opening that should be reduced through the logic of the open-loop control loop. This command is not processed by the PID controller and is quickly output to the valve, so that the turbine valve closes quickly in advance. After the valve is activated, the actual deviation between the actual pressure of the main steam and the pressure set value is reduced.

[0040] It should be noted that, in this embodiment, the control method is applicable to both dual-module (dual-reactor) and multi-module (multi-reactor) high-temperature reactor units for turbine inlet steam pressure control. For example, when there are two reactors, the pressure setpoint is the rated pressure of 13.24 MPa. When one reactor is shut down in an emergency, the steam flow rate is reduced by up to 50%. Therefore, the actual steam pressure in the following steps deviates from the preset pressure setpoint by 50%, i.e., 6.6 MPa. Of course, when there are multiple reactors, the preset deviation needs to be determined based on the actual number of reactors and the pressure setpoint. Those skilled in the art can set it according to actual needs, and no specific limitation is made.

[0041] Specifically, taking a dual-reactor reactor as an example, the process of forming open-loop control commands is as follows: Figure 3 As shown, the pressure setpoint is 13.24 MPa, and the preset deviation is 6.6 MPa. This 6.6 MPa represents the maximum deviation between the turbine inlet steam pressure and the pressure setpoint. When a fast unloading action occurs in one of the reactors, an open-loop control command is triggered. The actual steam pressure inlet of the turbine is subtracted from the pressure setpoint to obtain the actual deviation. This actual deviation is then divided by 6.6 MPa and multiplied by 100% to obtain the valve opening. This valve opening is then superimposed on the AV output value of the pressure controller. Specifically, when the actual deviation reaches 6.6 MPa, the open-loop output must reach its maximum value to bring the turbine inlet steam pressure back to the setpoint. The ultimate limit of the open-loop output reaching its maximum value is valve closure. In other words, when the actual deviation equals 6.6 MPa, the turbine valve needs to be closed rapidly in advance; when the actual deviation is less than 6.6 MPa, the turbine valve opening is reduced in advance. That is, the valve closure amplitude is increased according to the magnitude of the actual deviation to reduce the fluctuation of the turbine inlet steam pressure.

[0042] For further information, please continue to refer to [link / reference]. Figure 3 The open-loop control command mentioned above is the percentage of steam flow rate in front of the turbine. When there are two reactors and one reactor is shut down, the flow rate can be reduced by up to 50%. Therefore, the open-loop control command is limited by 50%. Thus, the preset command is set to 0.5.

[0043] It should be understood that you should continue to refer to [this information]. Figure 3 During the open-loop control process described above, the pressure controller is always in automatic control mode. Under the combined action of the switch control and the closed-loop control of the pressure controller, the actual deviation between the steam pressure before the machine and the set value gradually decreases. At this time, the open-loop control command also decreases. When the open-loop control command is less than 0.5, the open-loop control is cut off after a 5s delay, and the DEH control mode is only in the closed-loop control of the pressure controller.

[0044] Furthermore, please continue to refer to... Figure 3In the open-loop control process, it is also necessary to correct the deviation between the actual performance of the turbine control valve and the high-temperature reactor steam flow. K is the correction coefficient, which needs to be determined through debugging to improve the accuracy of valve regulation.

[0045] Furthermore, please continue to refer to... Figure 3 ODIP is a conversion function between the percentage of steam flow command and the percentage of valve opening command. In other words, there is a corresponding relationship between the percentage of steam flow and the valve opening. This conversion function can convert the steam flow command into the total valve command to control the opening of the turbine valves.

[0046] Furthermore, please continue to refer to... Figure 3 The trigger has two inputs: a set input (S) and a reset input (R), and one output (Q). When a fast unloading action occurs in one of the reactors, S is 1, and Q is 1 (DM01 is true). The selection function block SEL selects the output open-loop control command. This open-loop control command is then superimposed on the output value of the pressure controller and converted into a general control command via a conversion function. When the open-loop control command is less than 0.5, after a 5-second delay, the reset input R = 1, S = 0, and Q = 0. At this point, the selection function block SEL no longer selects the output open-loop control command. In other words, after the trigger's reset input R takes effect, the open-loop control command has been reduced to a small value, having virtually no impact on the pressure controller. At this point, the pressure controller then performs closed-loop automatic adjustment based on the actual steam pressure at the reactor inlet, achieving a smooth transition in the control mode.

[0047] S120: The open-loop control command is superimposed with the closed-loop control command of the pressure controller to form the general control command for the turbine valves.

[0048] Specifically, such as Figure 3 As shown, when a reactor experiences a rapid unloading operation, the open-loop control command generated in step S110 is directly superimposed on the AV output value of the pressure controller to form a general control command, which adjusts the turbine valve opening. In other words, when the actual deviation is less than the preset deviation, the pressure controller is in automatic control mode, and the valve control command tracks the AV output value of the pressure controller.

[0049] In this embodiment, the rapid coarse adjustment of open-loop control and the fine closed-loop regulation work together to ensure that the steam pressure in front of the turbine is maintained near the pressure setpoint, thereby reducing large fluctuations in steam pressure and ensuring the safe and stable operation of the unit.

[0050] It should be noted that when the actual deviation and the preset deviation gradually decrease and the open-loop control command is less than 0.5, the open-loop control command is cut off. At this time, the DEH control mode is only in the closed-loop control of the pressure controller, and the control process is the same as the steam pressure control principle before the machine under normal operating conditions described below.

[0051] In this embodiment, after the open-loop control command is withdrawn, the control mode is jointly controlled by the open-loop control command and the closed-loop control command. After switching to closed-loop automatic control by the pressure controller alone, the total control command of the turbine valve can be switched without disturbance, thereby improving the control efficiency of the turbine valve opening.

[0052] It should be understood that during the operation of both reactors at full power, if an emergency shutdown of one reactor occurs, the DEH pressure controller remains in closed-loop automatic control mode. This closed-loop control utilizes feedback control principles. When the steam pressure at the turbine inlet deviates from the pressure setpoint, the actual change in deviation is calculated by the pressure controller's proportional and integral operations to output a closed-loop control valve command. The opening and closing of the valve restores the steam pressure to the setpoint, thus stabilizing the steam pressure at the turbine inlet. Of course, except for the instantaneous condition of a reactor undergoing rapid unloading, this pressure controller also remains in closed-loop automatic control mode under normal operating conditions.

[0053] Specifically, the principle of steam pressure control before the machine under normal operating conditions is as follows: Figure 4 As shown, the pressure setpoint of the pressure controller is SP, and the actual steam pressure before the turbine is PV. The actual deviation is calculated based on the SP and PV values. The change in the actual deviation is output as a valve command through proportional and integral calculations of the pressure controller.

[0054] Furthermore, such as Figure 4 As shown, the pressure controller can also switch the control mode according to the magnitude of the actual deviation and the preset deviation (50% of the pressure setpoint). For example, when the actual deviation is less than the preset deviation, the pressure controller is in automatic control mode; when the actual deviation is greater than the preset deviation, the pressure controller exits automatic control mode, and the DEH control mode switches from automatic control to manual control (valve control mode). In manual mode, the AV output value of the pressure controller tracks the valve control command. In other words, when the actual deviation is too large, the control program needs to be exited, and the operator needs to manually adjust the valve.

[0055] S130. Adjust the turbine valve opening in advance according to the general control valve instruction.

[0056] It should be understood that the valve opening needs to be determined based on the percentage of steam flow in front of the turbine. When the actual deviation is small, the percentage of steam flow is also small, and the valve opening only needs to be reduced according to the percentage of steam flow to bring the steam pressure in front of the turbine back to the pressure set value. When the actual deviation reaches the maximum value, the percentage of steam flow reaches the maximum value, and the valve needs to be closed to reduce the fluctuation of the steam pressure in front of the turbine and reduce the deviation between the steam pressure in front of the turbine and the pressure set value.

[0057] Specifically, when the actual deviation is less than the preset deviation, the turbine valve opening is reduced in advance according to the general control valve command; when the actual deviation is equal to the preset deviation, the turbine valve is closed quickly in advance according to the general control valve command.

[0058] In this embodiment, the turbine inlet steam pressure is controlled under normal operating conditions by closed-loop regulation of the pressure controller. After a rapid unloading operation, both open-loop control and closed-loop regulation of the pressure controller work together to maintain stable turbine inlet steam pressure. Once the steam pressure stabilizes, the open-loop control can be disengaged without disturbance, and the steam pressure is maintained solely by the closed-loop control of the DEH pressure controller. This control method satisfies the requirements for stable turbine inlet steam pressure under both normal high-temperature reactor operating conditions and transient rapid unloading operations, while also ensuring stable evaporator outlet pressure and extending the evaporator's service life.

[0059] like Figure 5 As shown, another aspect of the present invention proposes a control system 200 for the steam pressure at the turbine inlet of a high-temperature gas-cooled reactor, comprising: an open-loop control command forming unit 210, used to form an open-loop control command when one of the reactors experiences an emergency shutdown and rapid unloading operation; a total valve command forming unit 220, used to superimpose the open-loop control command with the output command of the pressure controller to form a total valve command for the turbine valves; and a valve opening adjustment unit 230, used to adjust the turbine valve opening in advance according to the total valve command.

[0060] In this embodiment, during dual-reactor operation, when a transient situation of emergency shutdown of one reactor occurs, the above-mentioned control system can cause the turbine control valves to act in advance and quickly, reducing large fluctuations in steam pressure and ensuring the safe and stable operation of the reactor unit.

[0061] Specifically, combined Figures 2 to 5 As shown, the open-loop control command generation unit is specifically used to: obtain the actual deviation between the actual steam pressure in front of the turbine and the pressure setpoint; when the actual deviation is less than or equal to the preset deviation, determine the expected reduction in the turbine control valve opening based on the actual deviation, and generate an open-loop control command.

[0062] It should be noted that the process of forming the above open-loop control commands is described in the previous text and will not be repeated here.

[0063] Furthermore, in this embodiment, the control system 200 further includes an open-loop control cutoff unit 240, which is used to delay the cutoff of open-loop control when the open-loop control command is less than a preset command.

[0064] It should be noted that during the above open-loop control process, the pressure controller is always in automatic control mode. Under the combined action of the switch control and the closed-loop control of the pressure controller, the actual deviation between the steam pressure before the turbine and the set value gradually decreases. At this time, the open-loop control command also decreases. When the open-loop control command is less than 0.5, the open-loop control switching unit will delay and cut off the open-loop control of the turbine valves. At this time, the pressure controller will then perform closed-loop automatic adjustment according to the actual steam pressure before the turbine. That is to say, when the steam pressure before the turbine returns to normal, the control mode will be switched to the closed-loop automatic control mode controlled by the pressure controller.

[0065] It should be further noted that the closed-loop automatic control process of the turbine valves by the pressure controller is also described above.

[0066] Furthermore, in this embodiment, the control system also includes a control mode switching unit, which switches the automatic control mode to the manual control mode when the actual deviation is greater than the preset deviation.

[0067] Specifically, when the actual deviation between the steam pressure at the machine and the pressure setpoint exceeds 50% of the pressure setpoint, the pressure controller exits automatic control mode, and the DEH control mode switches from automatic to manual control (valve control mode). In manual mode, the AV output value of the pressure controller tracks the valve control command. In other words, when the actual deviation is too large, the control system needs to be shut down, and the operator must manually adjust the valve.

[0068] It should be further noted that the system embodiments described in this invention are merely illustrative. For example, the division of the units can be a logical functional division, and there may be other division methods in actual implementation. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed.

[0069] This invention proposes a method and control system for controlling the steam pressure before the turbine of a high-temperature gas-cooled reactor, which has the following advantages: The control method of this invention combines rapid coarse adjustment of the open-loop control loop with fine closed-loop adjustment of the pressure controller to ensure that the steam pressure before the turbine is maintained near the pressure setpoint. This ensures the equipment safety and temperature operation of the reactor unit, meeting the stable steam pressure requirements before the turbine under normal operating conditions and transient conditions during rapid unloading of the high-temperature reactor. It also ensures stable evaporator outlet pressure, extending the service life of the evaporator. Furthermore, when the control mode changes, turbine valve commands can be switched seamlessly, improving the control efficiency of the turbine valves.

[0070] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method of controlling the pressure of the steam in front of the turbine of a high-temperature gas-cooled reactor, characterized in that, The control method includes: When one of the reactors experiences an emergency shutdown and rapid unloading operation, the actual deviation between the actual steam pressure at the turbine inlet and the pressure setpoint is obtained. When the actual deviation is less than or equal to the preset deviation, the expected reduction in the opening of the turbine control valve is determined based on the actual deviation, thus forming an open-loop control command. The open-loop control command is superimposed with the closed-loop control command of the pressure controller to form the total control command of the turbine control valve. The closed-loop control command utilizes the feedback control principle. When the steam pressure in front of the turbine deviates from the pressure setpoint, the actual change in deviation is calculated by the proportional and integral operations of the pressure controller to output the closed-loop control command. The opening and closing of the control valve causes the steam pressure to return to the setpoint, thereby stabilizing the steam pressure in front of the turbine. Adjust the turbine control valve opening in advance according to the general control valve command.

2. The control method according to claim 1, characterized in that, The turbine control valve opening is correlated with the percentage of steam flow.

3. The control method according to claim 2, characterized in that, The open-loop control command also includes: Corrections are made to the actual deviation between the turbine control valve opening performance and the steam flow rate at the turbine inlet of the high-temperature gas-cooled reactor.

4. The control method according to claim 3, characterized in that, The control method further includes: The open-loop control command decreases as the actual deviation decreases, and when the open-loop control command is less than the preset command, the open-loop control is disconnected after a delay.

5. The control method according to claim 4, characterized in that, The open-loop control command is a percentage of steam flow, and the preset command is 0.

5.

6. The control method according to claim 1, characterized in that, When the actual deviation exceeds the preset deviation, the pressure controller exits closed-loop control.

7. A control system for the steam pressure at the inlet of a high-temperature gas-cooled reactor turbine, characterized in that, The control system includes: The open-loop control command generation unit is used to obtain the actual deviation between the actual steam pressure in front of the turbine and the pressure setpoint when one of the reactors experiences an emergency shutdown and rapid unloading operation. When the actual deviation is less than or equal to the preset deviation, the expected reduction in the opening of the turbine control valve is determined based on the actual deviation, thus forming an open-loop control command. The main control valve command generation unit is used to superimpose the open-loop control command and the closed-loop control command of the pressure controller to form the main control valve command of the turbine. The closed-loop control command utilizes the feedback control principle. When the steam pressure in front of the turbine deviates from the pressure setpoint, the actual change in deviation is calculated by the proportional and integral operations of the pressure controller to output the closed-loop control valve command. The opening and closing of the control valve causes the steam pressure to return to the setpoint, thereby stabilizing the steam pressure in front of the turbine. The valve opening adjustment unit adjusts the turbine valve opening in advance according to the general control valve command.

8. The control system according to claim 7, characterized in that, The control system further includes an open-loop control cutoff unit, used to delay and cut off the open-loop control when the open-loop control command is less than a preset command.

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