A method, system, equipment, and medium for preventing backflow of steam in a steam-driven feedwater pump.

Abstract

This invention discloses a method, system, equipment, and medium for preventing backflow control in steam-driven feedwater pumps, belonging to the field of steam-driven feedwater pump control technology for thermal power generating units. The method includes: when any low-pressure steam source abnormality condition is met, controlling the high-pressure regulating valve to overshoot and open to a pre-set initial opening degree; when the high-pressure regulating valve completes its overshoot opening, controlling the high-pressure and low-pressure regulating valves to jointly perform speed regulation following the overall regulating valve command output by the speed closed-loop controller; during the joint speed regulation process, when the low-pressure steam source pressure is greater than the pressure of the upstream connected steam source, receiving a manual exit command, and controlling the high-pressure regulating valve to close gradually at a pre-set controlled exit rate until fully closed, thus restoring the steam-driven feedwater pump to a single low-pressure steam source regulation state. This invention achieves rapid intervention and uninterrupted exit of the high-pressure steam source through software logic when the check valve hardware defense fails, effectively preventing low feedwater flow protection actions caused by backflow.

Description

Technical Field

[0001] This invention relates to the field of steam-driven feedwater pump control technology for thermal power generating units, specifically to a method, system, equipment, and medium for preventing backflow control of steam-driven feedwater pumps. Background Technology

[0002] In thermal power generating units, the steam-driven feedwater pump is equipped with a low-pressure regulating valve that uses the fourth-stage extraction steam as its steam source and a high-pressure regulating valve that uses cold reheat steam as its steam source. During normal operation, only the low-pressure regulating valve regulates the speed. When the unit is under low load conditions or during rapid load reduction, the pressure of the fourth-stage extraction steam drops rapidly. When the pressure of the fourth-stage extraction steam approaches the deaerator pressure, the check valve between the fourth-stage extraction steam and the deaerator cannot close effectively because the pressure difference between the two ends approaches zero. The wet steam in the deaerator flows back into the low-pressure steam inlet pipe of the steam-driven feedwater pump along the extraction steam pipe, causing the low-pressure steam inlet temperature to drop sharply. The steam-driven feedwater pump's work capacity is insufficient, the feedwater flow rate decreases, and in severe cases, the low feedwater flow protection action is triggered, causing the unit to shut down.

[0003] Existing technology relies on non-return valves as the only hardware defense against backflow. When the pressure difference between the fourth-stage extraction steam and the deaerator approaches zero, there is a physical closing blind zone, which cannot effectively prevent backflow. It also lacks control measures to quickly intervene when the non-return valve fails. Summary of the Invention

[0004] In view of the above-mentioned problems, the present invention provides a method, system, equipment and medium for preventing backflow control of steam-driven feedwater pumps.

[0005] Therefore, the technical problem solved by this invention is that under low load or rapid load reduction conditions of the unit, the non-return valve cannot be effectively closed because the pressure difference between the two ends approaches zero, and the wet steam in the deaerator flows back into the low-pressure steam inlet pipe of the steam-driven feedwater pump, resulting in insufficient work capacity of the steam-driven feedwater pump and reduced feedwater flow. The existing non-return valve hardware defense line cannot effectively prevent backflow under the above conditions.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for preventing backflow of steam in a steam-driven feedwater pump, comprising, Based on the multi-path operating parameters of the low-pressure steam inlet side, multiple low-pressure steam source abnormal state judgment conditions are determined respectively. When any one of the multiple low-pressure steam source abnormal state judgment conditions is met, the high-pressure regulating valve is controlled to overshoot and open to the preset initial opening degree. When the high-pressure regulating valve completes the override opening, the high-pressure regulating valve and the low-pressure regulating valve are controlled to jointly perform joint speed regulation in accordance with the regulating valve general command output by the speed closed-loop controller; During the combined speed regulation process, when the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source of the low-pressure steam source, a manual exit command is received, and the high-pressure regulating valve is controlled to close gradually at a preset controlled exit rate until it is fully closed, so that the steam-driven feedwater pump returns to the single low-pressure steam source regulation state.

[0007] As a preferred embodiment of the steam-driven feedwater pump anti-backflow control method of the present invention, the abnormal state determination conditions of the plurality of low-pressure steam sources include: The low-pressure steam source abnormal state determination condition is met when the number of measuring points whose temperature change rate exceeds the preset change rate threshold reaches the preset number threshold. When the measured value of the low-pressure steam inlet temperature is less than the preset lower limit threshold, the condition for determining the abnormal state of the low-pressure steam source is met. When the unit load is less than the preset load threshold and the low-pressure regulating valve opening is greater than the preset opening threshold, the low-pressure steam source abnormal state determination condition is met.

[0008] In a preferred embodiment of the steam-driven feedwater pump anti-backflow control method described in this invention, the determination of the pre-set initial opening degree includes: Collect historical pressure data of high-pressure steam source and low-pressure steam source under various operating conditions, and calculate the pressure ratio between high-pressure steam source and low-pressure steam source based on the historical pressure data; Based on the pressure ratio, the compensation opening of the high-pressure regulating valve under the maximum opening condition of the low-pressure regulating valve is calculated, and the compensation opening is used as the initial opening.

[0009] As a preferred embodiment of the anti-backflow control method for a steam-driven feedwater pump according to the present invention, the combined speed regulation includes: The speed closed-loop controller adjusts the general command of the regulating valve based on the deviation between the speed of the steam-driven feedwater pump and the preset speed setting value, and drives the high-pressure regulating valve and the low-pressure regulating valve to perform deviation correction opening adjustment; The speed closed-loop controller performs feedforward compensation on the total command of the regulating valve based on the water supply flow command, and drives the high-pressure regulating valve and the low-pressure regulating valve to perform feedforward compensation opening adjustment.

[0010] As a preferred embodiment of the steam-driven feedwater pump anti-backflow control method of the present invention, wherein: the pre-set controlled exit rate is controlled by a logic selector tracking loop, and the controlled exit rate is determined based on the target exit time of the high-pressure regulating valve from the initial opening to full closure; When the manual exit command is received, the logic selector tracking loop controls the opening command of the high-voltage regulating valve to decrease at the controlled exit rate until the high-voltage regulating valve is closed completely.

[0011] As a preferred embodiment of the steam-driven feedwater pump anti-backflow control method of the present invention, wherein: when the unit load is greater than the preset input load threshold, the judgment of the multiple low-pressure steam source abnormal state judgment conditions is executed; When the manual exit command is received, the judgment of the multiple low-pressure steam source abnormal state determination conditions is stopped.

[0012] As a preferred embodiment of the steam-driven feedwater pump anti-backflow control method of the present invention, the determination that the low-pressure steam source pressure is greater than the pressure of the upstream connected steam source of the low-pressure steam source includes: Obtain the pressure of the low-pressure steam source and the pressure of the steam source connected upstream of the low-pressure steam source; When the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source, the manual exit command can be received.

[0013] This invention provides a backflow prevention control system for a steam-driven feedwater pump.

[0014] To solve the above technical problems, the present invention provides the following technical solution: a steam-driven feedwater pump anti-backflow control system, comprising: a parameter acquisition module, used to acquire multiple operating parameters on the low-pressure steam inlet side of the steam-driven feedwater pump, and output the multiple operating parameters to an abnormal state judgment module; An abnormal state judgment module is connected to the parameter acquisition module and is used to judge multiple low-pressure steam source abnormal state judgment conditions based on the multi-channel operating parameters. When any one of the low-pressure steam source abnormal state judgment conditions is met, a trigger signal is output to the override control module. The override control module is connected to the abnormal state judgment module. After receiving the trigger signal, it controls the high-voltage regulating valve to override open to a preset initial opening degree, and outputs a cut-in signal to the joint regulation module after the high-voltage regulating valve completes the override opening. The joint adjustment module is connected to the override control module and the speed closed-loop controller. After receiving the cut-in signal, it controls the high-pressure regulating valve and the low-pressure regulating valve to jointly perform joint speed adjustment in accordance with the regulating valve general command output by the speed closed-loop controller. The controlled exit module, connected to the joint regulation module, is used to receive a manual exit command during the joint speed regulation process when the low-pressure steam source pressure is greater than the pressure of the upstream connected steam source of the low-pressure steam source, and control the opening command of the high-pressure regulating valve to decrease to full closure at a preset controlled exit rate. The commissioning / decommissioning management module is connected to the abnormal state judgment module. It is used to control the abnormal state judgment module to perform the judgment when the unit load is greater than the preset commissioning load threshold, and to control the abnormal state judgment module to stop the judgment when the manual decommissioning command is received.

[0015] The present invention provides a computer device, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the steam-driven feedwater pump anti-backflow control method.

[0016] The present invention provides a computer-readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the steps of the aforementioned method for preventing backflow control of a steam-driven feedwater pump.

[0017] The beneficial effects of this invention are as follows: Based on the multi-dimensional abnormal state judgment conditions of multiple operating parameters on the low-pressure steam inlet side, this invention enables the rapid override intervention of the high-pressure regulating valve when the non-return valve hardware defense fails, effectively preventing the steam-driven feedwater pump from triggering low feedwater flow protection action due to insufficient work capacity caused by backflow of low-pressure steam source.

[0018] This invention employs a logic OR triggering architecture consisting of a three-out-of-two criterion for temperature change rate, a lower limit criterion for absolute temperature value, and a combined criterion for load opening. The three criteria cover reverse steam conditions at different rates and stages. The three-out-of-two logic effectively eliminates false tripping caused by single-point faults, improving the reliability of reverse steam triggering.

[0019] This invention determines the initial opening degree of the override based on the pressure ratio of high and low pressure steam sources. After the high pressure regulating valve is over-over-opened, a back pressure is established in the low pressure steam inlet pipeline, which physically blocks the continuous entry of back steam into the deaerator. At the same time, it quickly replenishes the amount of steam required for the steam-driven feedwater pump to do work, ensuring a stable feedwater flow rate.

[0020] This invention controls the high-pressure regulating valve to gradually close at a pre-set controlled exit rate by tracking the logic selector circuit. The low-pressure regulating valve gradually compensates for the steam quantity during the exit process. The total command of the regulating valve is continuously output before and after exit, so as to achieve the uninterrupted exit of the high-pressure steam source and avoid speed disturbance during the exit process. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 The above is a flowchart of an anti-backflow control method for a steam-driven feedwater pump provided in one embodiment of the present invention.

[0023] Figure 2 The most recent MFT curve of the unit caused by steam backflow in a steam-driven feedwater pump anti-backflow control method provided in an embodiment of the present invention.

[0024] Figure 3 This is a soft logic diagram for an anti-backflow control method for a steam-driven feedwater pump, provided as an embodiment of the present invention. Detailed Implementation

[0025] To make the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present invention.

[0026] Example 1, referring to Figure 1 This is one embodiment of the present invention, which provides a method for preventing backflow of steam in a steam-driven feedwater pump, comprising: S1. Based on the multi-path operating parameters of the low-pressure steam inlet side, determine multiple low-pressure steam source abnormal state judgment conditions respectively. When any one of the multiple low-pressure steam source abnormal state judgment conditions is met, control the high-pressure regulating valve to overshoot and open to the preset initial opening degree.

[0027] In some embodiments, the steam-driven feedwater pump is equipped with a low-pressure regulating valve that uses four-stage extraction steam as its steam source and a high-pressure regulating valve that uses cold reheat steam as its steam source. Under normal operating conditions, the speed of the steam-driven feedwater pump is regulated only by the low-pressure regulating valve, while the high-pressure regulating valve remains closed.

[0028] Understandably, when the unit is operating at a low load of less than 460MW or during a rapid load reduction process, the pressure of the fourth-stage extraction steam drops rapidly as the main steam regulating valve closes. When the pressure of the fourth-stage extraction steam approaches the saturated steam pressure of the deaerator, the check valve between the fourth-stage extraction steam and the deaerator cannot close effectively because the pressure difference between the two ends approaches zero. The saturated wet steam in the deaerator flows backward along the extraction steam pipeline into the low-pressure steam inlet pipeline of the steam-driven feedwater pump, causing the low-pressure steam inlet temperature to drop sharply. The steam-driven feedwater pump has insufficient power, the feedwater flow rate is reduced, and in severe cases, the low feedwater flow protection action is triggered.

[0029] It should be noted that water may accumulate in the four extraction steam pipes and the auxiliary steam commissioning steam pipes during unit operation. When the unit rapidly reduces load, the water in these pipes may flow back into the low-pressure steam inlet pipe of the steam-driven feedwater pump along with the backflowing steam, exacerbating the abnormal drop in low-pressure steam inlet temperature. To reduce the risk of this water backflow, the water-accumulating sections of the four extraction steam pipes and the auxiliary steam commissioning steam pipes should be drained regularly during unit operation.

[0030] Step S1 involves continuous monitoring of multiple operating parameters on the low-pressure steam inlet side and logical judgment based on multiple low-pressure steam source abnormality determination conditions to enable rapid intervention of the high-pressure steam source when the non-return valve hardware defense fails.

[0031] The determination of multiple low-pressure steam source abnormal state conditions in step S1 includes steps S11 to S13, wherein: S11. Calculate the low-pressure steam inlet temperature change rate of each measuring point based on the measured values ​​of multiple low-pressure steam inlet temperature measuring points. When the number of measuring points whose temperature change rate exceeds the preset change rate threshold reaches the preset number threshold, the low-pressure steam source abnormal state judgment condition is established.

[0032] In some embodiments, three independent measuring points are set up for the low-pressure steam inlet temperature, respectively located at different positions in the low-pressure steam inlet pipeline. The three measuring points independently collect the low-pressure steam inlet temperature signal. The MEH controller calculates the low-pressure steam inlet temperature change rate of each measuring point based on the measured low-pressure steam inlet temperature values ​​of the three measuring points within a preset sampling period, according to the ratio of the temperature change of each measuring point to the sampling period. The preset sampling period is set to 1 second, that is, the MEH controller collects the measured low-pressure steam inlet temperature value of each measuring point every 1 second, and the low-pressure steam inlet temperature change rate of each measuring point is obtained by dividing the temperature difference between two adjacent measurements by the sampling period of 1 second.

[0033] Furthermore, the preset rate of change threshold is determined based on statistical analysis of historical operating data. Through the collection and statistical analysis of historical data of daily operation of the unit, the rate of change of low-pressure steam inlet temperature under normal large load fluctuation conditions does not exceed 0.6℃ / s, while the rate of change of low-pressure steam inlet temperature can reach 0.8℃ / s or more when deaerator backflow occurs.

[0034] Based on the above statistical laws, the preset change rate threshold is set to 0.8℃ / s, so that the temperature change rate judgment in step S11 can effectively distinguish between normal load increase / decrease conditions and reverse steam conditions, and avoid the anti-reverse steam control function from being frequently triggered falsely under normal conditions.

[0035] Furthermore, the preset quantity threshold adopts a two-out-of-three logic design, that is, when the number of measurement points among the three low-pressure steam inlet temperature measurement points that meet the condition of temperature change rate exceeding the preset change rate threshold of 0.8℃ / s reaches two or more, the judgment condition in step S11 is met, and the judgment condition of the low-pressure steam source abnormal state is met.

[0036] It is understandable that the design basis for adopting the three-out-of-two logic is that a single measurement point may be falsely triggered due to faults such as signal drift, short circuit or open circuit. The three-out-of-two logic can effectively eliminate false triggering caused by single-point faults while ensuring the reliability of abnormal state detection, thereby improving the reliability of the low-pressure steam source abnormal state judgment condition triggering in step S11.

[0037] It should be noted that when there are fewer than two valid measuring points among the three low-pressure steam inlet temperature measuring points, the two-out-of-three judgment in step S11 cannot output a valid signal, and the judgment condition of step S11 is not met. However, the absolute temperature value judgment in step S12 and the load opening combination judgment in step S13 remain valid and can still trigger the low-pressure steam source abnormal state judgment condition to ensure that the anti-backflow control function is not completely ineffective under the condition of measuring point failure.

[0038] S12. When the measured value of the low-pressure steam inlet temperature is less than the preset lower limit threshold, the condition for determining the abnormal state of the low-pressure steam source is met.

[0039] In some embodiments, the measured value of the low-pressure steam inlet temperature in step S12 is taken from the measured value of the effective measuring point among the above three low-pressure steam inlet temperature measuring points.

[0040] Furthermore, the preset lower temperature threshold is determined based on statistical analysis of historical operating data and is set to 280℃. When the measured value of the low-pressure steam inlet temperature at any valid measuring point is less than 280℃, the judgment condition in step S12 is met, and the judgment condition for the abnormal state of the low-pressure steam source is met.

[0041] It is understandable that the absolute temperature value judgment in step S12 and the temperature change rate judgment in step S11 represent different stages of the same low-pressure steam source backflow physical process. Step S11 captures the rapid dynamic decrease in low-pressure steam inlet temperature at the initial stage of backflow, while step S12 captures backflow conditions where the temperature drop rate does not exceed the preset change rate threshold of 0.8℃ / s but lasts for a long time and the low-pressure steam inlet temperature has dropped below 280℃. The two complement each other and cover backflow processes with different rates.

[0042] S13. When the unit load is less than the preset load threshold and the low-pressure regulating valve opening is greater than the preset opening threshold, the low-pressure steam source abnormal state determination condition is met.

[0043] In some embodiments, the preset load threshold and the preset opening threshold in step S13 are both determined based on statistical analysis of historical operating data.

[0044] Furthermore, through the collection and statistical analysis of historical daily operation data of the unit, under low-load conditions where the unit load is less than 460MW, the opening degree of the low-pressure regulating valve in normal operation does not exceed 57%. Based on the above statistical rules, the preset load threshold mentioned in step S13 is set to 460MW, and the preset opening degree threshold is set to 57.5%.

[0045] Furthermore, when the unit load is less than 460MW and the low-pressure control valve opening is greater than 57.5%, the judgment condition in step S13 is met, and the judgment condition for the abnormal state of the low-pressure steam source is met. The load condition and the opening condition in step S13 are logically ANDed, and both must be satisfied simultaneously to avoid false triggering caused by the low-pressure control valve opening being too large due to the steam-driven feedwater pump operating at full output under normal operating conditions when the unit load is greater than 460MW.

[0046] It is understandable that the load opening combination judgment in step S13 captures the early working condition of reverse steam when the output of the low-pressure steam source is insufficient but the low-pressure steam inlet temperature has not dropped significantly. Together with step S11 and step S12, it constitutes a multi-dimensional abnormal state detection system covering the entire reverse steam process.

[0047] It should be noted that the judgment conditions in steps S11, S12, and S13 are logically ORed. When any judgment condition in any step is met, the trigger condition of any one of the multiple low-pressure steam source abnormal state judgment conditions in step S1 is met, thereby controlling the high-pressure regulating valve to overshoot and open to the preset initial opening degree.

[0048] In some embodiments, determining the preset initial opening degree in step S1 includes steps S14 to S15, wherein: S14. Collect historical pressure data of high-pressure steam source and low-pressure steam source under various operating conditions, and calculate the pressure ratio between high-pressure steam source and low-pressure steam source based on the historical pressure data.

[0049] In some embodiments, by statistically analyzing the historical pressure data of cold resteam pressure and fourth-stage extraction steam pressure under various operating conditions of the unit, the pressure ratio between cold resteam pressure and fourth-stage extraction steam pressure under each operating condition is stable at 5:1, which can be used as a fixed calculation basis for calculating the compensation opening in step S15.

[0050] S15. Based on the pressure ratio, calculate the compensation opening of the high-pressure regulating valve under the maximum opening condition of the low-pressure regulating valve, and use the compensation opening as the initial opening.

[0051] In some embodiments, based on the 5:1 ratio of cold reheat steam to fourth-stage extraction steam pressure obtained in step S14, under the same steam flow demand, the required opening of the high-pressure control valve is one-fifth of the opening of the low-pressure control valve. Based on the above conversion relationship, when the low-pressure control valve is operating at its maximum opening, the corresponding compensation opening of the high-pressure control valve is converted to 20%.

[0052] Furthermore, the 20% compensation opening is pre-programmed into the MEH controller as the initial opening setpoint in step S1. When the trigger condition in step S1 is met, the MEH controller directly outputs a 20% override opening command to the high-pressure regulating valve without going through the speed closed-loop controller calculation, ensuring that the high-pressure regulating valve responds quickly after triggering.

[0053] Understandably, after the high-pressure regulating valve opens to its initial opening, cold reheat steam enters the low-pressure steam inlet pipe, quickly replenishing the steam required for the steam-driven feedwater pump to perform its work. At the same time, the high-pressure cold reheat steam establishes back pressure in the low-pressure steam inlet pipe, physically preventing the wet steam in the deaerator from continuing to flow back into the low-pressure steam inlet pipe along the extraction pipe, thus inhibiting the further expansion of backflow.

[0054] In some embodiments, step S1 further includes steps S16 to S17, wherein: S16. When the unit load is greater than the preset input load threshold, the judgment of the multiple low-pressure steam source abnormal state judgment conditions shall be executed.

[0055] In some embodiments, the preset load threshold in step S16 is set to 300MW, corresponding to the stable operating condition of the unit under normal load after startup.

[0056] Furthermore, the operating conditions of the steam-driven feedwater pump change frequently during the unit startup process, and the low-pressure steam inlet parameters fluctuate significantly. To avoid the false triggering of the judgment conditions in steps S11 to S13 during the startup process due to fluctuations in operating conditions, the judgments in steps S11 to S13 are not executed before the unit load exceeds 300MW.

[0057] Furthermore, once the unit load exceeds 300MW and the operating conditions are stable, the operator manually switches the anti-backflow control function to the active state on the MEH operation screen. The judgments in steps S11 to S13 are then executed, and this operation is written into the start-up operation ticket as a standard operating procedure.

[0058] S17. When the manual exit command is received, the judgment of the multiple low-pressure steam source abnormal state determination conditions is stopped.

[0059] In some embodiments, step S17 is connected to the action of receiving the manual exit command in step S3. When the operator confirms in step S3 that the low-pressure steam source pressure is greater than the pressure of the upstream connected steam source of the low-pressure steam source and issues a manual exit command, step S17 simultaneously stops judging the judgment conditions of steps S11 to S13.

[0060] It is understandable that step S17 stops judging the judgment condition at the time the exit command is issued, so as to prevent the high-voltage regulating valve from repeatedly triggering the override opening action during the controlled exit process of step S3 because the judgment conditions of steps S11 to S13 are met again, and ensure that the controlled exit process of the high-voltage regulating valve in step S3 is not disturbed.

[0061] S2. When the high-pressure regulating valve completes the override opening, the high-pressure regulating valve and the low-pressure regulating valve are controlled to jointly perform joint speed regulation in accordance with the regulating valve general command output by the speed closed-loop controller.

[0062] In some embodiments, after the high-pressure regulating valve corresponding to the pre-cured initial opening of 20% in step S15 is overridden, the MEH controller switches the high-pressure regulating valve into a control mode that follows the regulating valve general command output by the speed closed-loop controller. The high-pressure regulating valve and the low-pressure regulating valve jointly perform joint speed regulation following the regulating valve general command output by the speed closed-loop controller.

[0063] It is understandable that in the combined speed regulation stage of step S2, both the high-pressure regulating valve and the low-pressure regulating valve use the general regulating valve command as a unified input. The speed closed-loop controller works continuously and drives the two regulating valves in a unified manner through the general regulating valve command to achieve stable control of the steam-driven feedwater pump speed.

[0064] The combined speed adjustment in step S2 includes steps S21 to S22, wherein: S21. The speed closed-loop controller adjusts the general command of the regulating valve based on the deviation between the speed of the steam-driven feedwater pump and the preset speed setting value, and drives the high-pressure regulating valve and the low-pressure regulating valve to perform deviation correction opening adjustment.

[0065] In some embodiments, the speed measurement module continuously acquires the speed signal of the steam-driven feedwater pump, and the speed closed-loop controller in the MEH controller compares the speed signal with a preset speed setpoint to calculate the speed deviation.

[0066] Furthermore, the speed setpoint is determined by converting the feedwater flow command. Based on the linear correspondence between the speed of the steam-driven feedwater pump and the feedwater flow, the feedwater flow command is converted into the corresponding target speed value as the speed setpoint. The linear correspondence is based on the design parameter calibration of the speed and feedwater flow under rated operating conditions of the steam-driven feedwater pump, and is pre-fixed in the MEH controller. By controlling the speed of the steam-driven feedwater pump to stabilize at the speed setpoint, precise control of the feedwater pump output is achieved.

[0067] Furthermore, the speed closed-loop controller adjusts the output value of the overall control valve command based on the speed deviation. When the speed of the steam-driven feedwater pump is less than the speed setpoint, the speed closed-loop controller increases the overall control valve command, driving the high-pressure and low-pressure control valves to synchronously increase their openings; when the speed of the steam-driven feedwater pump is greater than the speed setpoint, the speed closed-loop controller decreases the overall control valve command, driving the high-pressure and low-pressure control valves to synchronously decrease their openings, causing the speed of the steam-driven feedwater pump to converge towards the speed setpoint.

[0068] Understandably, in step S21, the high-pressure regulating valve and the low-pressure regulating valve jointly respond to the speed deviation and perform deviation correction opening adjustment. Compared with the adjustment of the low-pressure regulating valve alone, the total effective steam regulation capability of the two regulating valves is stronger. When the low-pressure steam inlet has insufficient work capacity under the reverse steam condition, the coordinated intervention of the high-pressure regulating valve effectively makes up for the loss of work capacity of the low-pressure steam source, so that the speed closed-loop controller can maintain the stable speed of the steam-driven feedwater pump.

[0069] S22. The speed closed-loop controller performs feedforward compensation on the total command of the regulating valve based on the water flow command, and drives the high-pressure regulating valve and the low-pressure regulating valve to perform feedforward compensation opening adjustment.

[0070] In some embodiments, the feedwater flow command is directly input as a feedforward signal to the speed closed-loop controller in the MEH controller. The speed closed-loop controller maps the feedwater flow command to a corresponding feedforward compensation amount through a pre-calibrated feedforward compensation function. The feedforward compensation function is calibrated based on the steady-state correspondence between the feedwater flow command and the total valve command and is pre-programmed into the MEH controller. The feedforward compensation amount is superimposed on the total valve command obtained from the speed deviation correction in step S21 to form a total valve command output value including feedforward compensation, which drives the high-pressure valve and the low-pressure valve to perform feedforward compensation opening adjustment.

[0071] Furthermore, the introduction of feedforward compensation in step S22 is based on the fact that the speed closed-loop controller is a feedback control mechanism, and its adjustment action depends on the generation of speed deviation, resulting in an inherent lag in response to changes in feedwater flow demand. By using the feedwater flow command as a feedforward signal to directly correct the overall control valve command, the high-pressure and low-pressure control valves can respond to changes in the feedwater flow command in advance before the speed deviation is formed, compensating for the lag in feedback control and improving the dynamic response speed of the joint speed regulation.

[0072] It is understandable that steps S21 and S22 are executed synchronously within the speed closed-loop controller. The feedback correction based on speed deviation in step S21 and the feedforward compensation based on feedwater flow command in step S22 work together to the overall control command of the control valve, forming a composite control strategy that combines feedback and feedforward. This drives the high-pressure control valve and the low-pressure control valve to perform joint speed regulation, thereby achieving stable speed control of the steam-driven feedwater pump under the combined steam supply conditions of high and low pressure dual steam sources.

[0073] It should be noted that in the combined speed regulation stage of step S2, the temperature of the four-stage extraction steam is about 350℃, the temperature of the cold reheat steam is about 300℃, and the temperature difference between the two steam sources is within 50℃, which meets the design specifications of the steam-driven feedwater pump manufacturer. The combined supply of high and low pressure dual steam sources does not pose a threat to the safe operation of the steam-driven feedwater pump.

[0074] S3. During the combined speed regulation process, when the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source of the low-pressure steam source, a manual exit command is received, and the high-pressure regulating valve is controlled to close gradually at a preset controlled exit rate until it is fully closed, so that the steam-driven feedwater pump returns to the single low-pressure steam source regulation state.

[0075] In some embodiments, step S3 is performed during the continuous operation of the combined speed regulation state established in step S2. After the combined speed regulation of the high-pressure regulating valve and the low-pressure regulating valve intervenes in step S2, the instantaneous fluctuation of the steam-driven feedwater pump speed converges to within ±30 r / min, and the feedwater flow rate returns to normal and follows the load command regulation.

[0076] It is understandable that the prerequisite for the exit operation in step S3 is that the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source of the low-pressure steam source. This condition indicates that the pressure of the fourth stage extraction steam has been restored to the normal state of being greater than the pressure of the deaerator, the reverse steam driving force of the deaerator to the low-pressure steam inlet pipeline is eliminated, and the low-pressure steam source has the ability to independently undertake the speed regulation of the steam-driven feedwater pump.

[0077] In some embodiments, the determination and execution of the pre-set controlled exit rate in step S3 includes steps S31 to S32, wherein: S31. The preset controlled exit rate is controlled by a logic selector tracking loop, and the controlled exit rate is determined based on the target exit time from the initial opening of the high-voltage regulating valve to full closure.

[0078] In some embodiments, the logic selector tracking loop in the MEH controller is responsible for controlling the rate of change of the high-voltage control valve opening command. The controlled exit rate is predetermined based on the target exit time required for the high-voltage control valve to close from its initial opening of 20% to full closure.

[0079] Furthermore, the target withdrawal time is determined based on the matching relationship between the low-pressure regulating valve opening compensation rate and the high-pressure regulating valve withdrawal rate. The low-pressure regulating valve opening compensation rate is determined by the response characteristics of the speed closed-loop controller. Under normal operating conditions of the steam-driven feedwater pump, the maximum opening compensation rate of the low-pressure regulating valve driven by the speed closed-loop controller is not less than 0.5% / s. Based on the aforementioned low-pressure regulating valve opening compensation rate, the high-pressure regulating valve withdrawal rate must be less than or equal to 0.5% / s to ensure that the low-pressure regulating valve can promptly compensate for the reduced steam volume caused by the high-pressure regulating valve withdrawal, and the instantaneous fluctuation of the steam-driven feedwater pump speed during the withdrawal process does not exceed ±30 r / min.

[0080] Furthermore, based on the above matching relationship, the controlled exit rate is set to 0.1% / s, the ratio of the low-pressure regulating valve opening compensation rate to the high-pressure regulating valve exit rate is 5:1, and the high-pressure regulating valve exit rate meets the matching requirement of being less than the low-pressure regulating valve opening compensation rate. The high-pressure regulating valve opening command decreases from the initial opening of 20% at a rate of 0.1% / s, and the target exit time for the high-pressure regulating valve from the initial opening to full closure is approximately 200s. The controlled exit rate of 0.1% / s is pre-programmed into the logic selector tracking loop of the MEH controller as the execution parameter for the controlled exit of the high-pressure regulating valve in step S32.

[0081] S32. When the manual exit command is received, the logic selector tracking circuit controls the opening command of the high-voltage regulating valve to decrease at the controlled exit rate until the high-voltage regulating valve is reduced to fully closed.

[0082] In some embodiments, after the MEH controller receives the manual exit command issued by the operator in step S34, the logic selector tracking loop is activated to control the high-voltage valve opening command to decrease from the current opening position at a controlled exit rate of 0.1% / s.

[0083] Furthermore, during the decreasing process of the high-pressure regulating valve opening command, the low-pressure regulating valve continuously follows the overall regulating valve command output by the speed closed-loop controller to perform speed regulation, gradually compensating for the reduced cold reheat steam supply caused by the high-pressure regulating valve exiting. The speed closed-loop controller continues to operate during the exit process, uniformly driving both regulating valves through the overall regulating valve command to ensure that the instantaneous fluctuation of the steam-driven feedwater pump speed does not exceed ±30 r / min during the exit process.

[0084] Furthermore, when the high-pressure regulating valve opening command decreases to zero, the logic selector tracking circuit stops outputting, the high-pressure regulating valve completely exits regulation, the steam-driven feedwater pump returns to a single low-pressure steam source regulation state, and the low-pressure regulating valve independently follows the regulating valve's overall command to perform speed regulation. Step S3 is then completed.

[0085] Understandably, the controlled exit rate of 0.1% / s in step S32 makes the high-pressure control valve exit process take about 200s. During the approximately 200s exit process, the low-pressure control valve gradually compensates for the reduced steam volume caused by the exit of the high-pressure control valve. The speed closed-loop controller does not need to be reinitialized, and the total control valve command is continuously output before and after exit, realizing a seamless switching of the high-pressure steam source exit process.

[0086] In some embodiments, the determination that the low-pressure steam source pressure is greater than the pressure of the upstream connected steam source in step S3 includes steps S33 to S34, wherein: S33. Obtain the pressure of the low-pressure steam source and the pressure of the steam source connected upstream of the low-pressure steam source.

[0087] In some embodiments, the MEH controller continuously collects the measured values ​​of the pressure measuring points of the four extraction steam pipelines as the low-pressure steam source pressure, and continuously collects the measured values ​​of the deaerator pressure measuring points as the pressure of the upstream connected steam source of the low-pressure steam source. The above two pressure measurement values ​​are displayed in real time on the MEH operation screen for continuous monitoring by operators.

[0088] Furthermore, during the combined speed regulation phase in step S2, the operators continuously observe the changing trends of the two pressure measurement values ​​on the MEH operation screen. Once the four-stage extraction steam pressure measurement values ​​rise back to above the deaerator pressure measurement values, it is confirmed that the low-pressure steam source reverse steam driving force has been eliminated.

[0089] S34. When the pressure of the low-pressure steam source is greater than the pressure of the steam source connected upstream of the low-pressure steam source, the manual exit command can be received.

[0090] In some embodiments, after the operator confirms on the MEH operation screen that the measured value of the four-stage extraction steam pressure is greater than the measured value of the deaerator pressure in step S34, the operator simultaneously confirms that the instantaneous fluctuation of the steam-driven feedwater pump speed does not exceed ±30 r / min, and that the feedwater flow rate and feedwater pressure stably follow the load command. After the above conditions are met, the operator manually issues an exit command on the MEH operation screen.

[0091] It is understandable that the issuance of the manual exit command in step S34 depends on the operator's active confirmation operation on the MEH operation screen, rather than being automatically triggered by the MEH controller. This ensures that the exit operation is performed after the operator determines that the low-pressure steam source has fully recovered to normal, thus avoiding the situation where the low-pressure steam source is insufficient in output again due to improper exit timing.

[0092] It should be noted that the execution of steps S33 and S34 is connected with step S17. After the manual exit command is received, step S17 simultaneously stops judging the judgment conditions of steps S11 to S13 to prevent the high-voltage regulating valve from repeatedly triggering the override opening action during the controlled exit process of step S32 due to the judgment conditions of steps S11 to S13 being met again, thus ensuring that the controlled exit process of the high-voltage regulating valve in step S32 is not disturbed.

[0093] Example 2, refer to Figure 2 and Figure 3 This invention provides a method for preventing backflow of steam in a steam-driven feedwater pump, and scientific demonstration is conducted through experiments to verify the beneficial effects of the invention.

[0094] Reference Figure 2 , Figure 2 This is a historical trend curve of Unit #3's low feedwater flow protection action caused by deaerator backflow. It records the changing trends of parameters such as the main unit's high pressure control valve command, the small unit's inlet steam temperature, the steam-driven feedwater pump speed, the low pressure control valve command and feedback, the high pressure control valve command, and the steam-driven feedwater pump inlet flow during the accident.

[0095] Figure 2 At the time of the accident, the unit load was 350MW, and the unit was in automatic power generation control mode. During the rapid load reduction process, the main turbine high-pressure control valve command continuously closed to increase the main steam pressure to the sliding pressure curve set value. The fourth-stage extraction steam pressure dropped rapidly as the main turbine high-pressure control valve command closed. When the fourth-stage extraction steam pressure approached the deaerator pressure, the check valve between the fourth-stage extraction steam and the deaerator could not be effectively closed due to the pressure difference between the two ends approaching zero. Unsaturated wet steam in the deaerator flowed back into the low-pressure steam inlet pipe of the steam-driven feedwater pump along the extraction steam pipe. At the same time, water accumulated in the fourth-stage extraction steam pipe flowed back into the low-pressure steam inlet pipe along with the backflowing steam, aggravating the abnormal drop in low-pressure steam inlet temperature. The rate of change of low-pressure steam inlet temperature exceeded the preset rate of change threshold of 0.8℃ / s, which met the judgment condition described in step S11.

[0096] Depend on Figure 2 The steam inlet temperature curve of the small and medium-sized turbines shows that the low-pressure steam inlet temperature drops sharply in a short period of time, indicating insufficient work capacity of the steam-driven feedwater pump. Even with the low-pressure regulating valve continuously opened to its maximum opening, it still could not maintain the set speed, and the feedwater pump speed continued to decrease. From... Figure 2 As can be seen from the high-pressure regulating valve command curve, without the intervention of the anti-backflow control method described in steps S1 to S3, the high-pressure regulating valve command approaches zero throughout the entire process. The high-pressure steam source does not participate in the regulation, and the single low-pressure steam source regulation method cannot cope with the above-mentioned backflow condition. The inlet flow of the steam-driven feedwater pump drops sharply to zero as the speed decreases, eventually triggering the low feedwater flow protection action.

[0097] Reference Figure 3 , Figure 3 The following is a logic diagram of the implementation of the anti-backflow control method described in steps S1 to S3 in the DCS system.

[0098] S1. Based on the multi-path operating parameters of the low-pressure steam inlet side, determine multiple low-pressure steam source abnormal state judgment conditions respectively. When any one of the multiple low-pressure steam source abnormal state judgment conditions is met, control the high-pressure regulating valve to overshoot and open to the preset initial opening degree.

[0099] Reference Figure 3 In step S11, the three independent temperature measuring points respectively collect the low-pressure steam inlet temperature signal. Each of the three measuring points calculates the low-pressure steam inlet temperature change rate within a preset sampling period of 1 second. The temperature change rate calculation results of the three measuring points are used to perform a two-out-of-three judgment. When the number of measuring points that meet the temperature change rate exceeding the preset change rate threshold of 0.8℃ / s reaches two or more, the judgment condition in step S11 is met, and a temperature rate judgment abnormal signal is output.

[0100] Reference Figure 3 In step S12, the absolute value judgment of the inlet steam temperature continuously receives the low-pressure inlet steam temperature measurement value of the effective temperature measurement point. When the low-pressure inlet steam temperature measurement value of any effective measurement point is less than the preset lower limit threshold of 280°C, the judgment condition in step S12 is met, and an abnormal inlet steam temperature signal is output.

[0101] Reference Figure 3 In step S13, the load opening combination judgment continuously receives the unit load signal and the low-pressure regulating valve opening signal. When the unit load is less than the preset load threshold of 460MW and the low-pressure regulating valve opening is greater than the preset opening threshold of 57.5%, the judgment condition in step S13 is met, and the low-pressure regulating valve opening abnormal signal under low load is output.

[0102] Reference Figure 3 The three signals output in steps S11, S12, and S13 are subjected to a logical OR operation. When any one of the signals is true, under the premise that the anti-backflow control function described in step S16 is in the active state and the unit load is greater than the preset active load threshold of 300MW, the high-pressure regulating valve is triggered to override and open to the initial opening degree of 20% as described in step S15.

[0103] Reference Figure 3 The anti-backflow control function described in step S16 is maintained in the active state by the set-reset logic. After the operator manually issues the activation command on the MEH operation screen, the set-reset logic is set, locking the active state. The set-reset logic is reset and the active state is released after the operator manually issues the exit command. The judgment condition described in step S17 is then stopped.

[0104] S2. When the high-pressure regulating valve completes the override opening, the high-pressure regulating valve and the low-pressure regulating valve are controlled to jointly perform joint speed regulation in accordance with the regulating valve general command output by the speed closed-loop controller.

[0105] Reference Figure 3 After the high-pressure regulating valve completes the overshoot opening to the initial opening degree of 20% as described in step S2, the switching logic in the DCS system switches the high-pressure regulating valve from the overshoot opening command to the control mode of following the regulating valve general command output by the speed closed-loop controller. The high-pressure regulating valve and the low-pressure regulating valve jointly follow the regulating valve general command to perform the joint speed regulation described in steps S21 and S22.

[0106] Reference Figure 3 The feedforward compensation of the water flow command mentioned in step S22 is achieved by a pre-calibrated feedforward compensation function. The water flow command is input to the feedforward compensation function as a feedforward signal. The feedforward compensation function is calibrated based on the steady-state correspondence between the water flow command and the total valve command. It is pre-fixed in the MEH controller. The feedforward compensation amount is superimposed on the total valve command obtained by the speed deviation correction in step S21 to form a total valve command output value containing feedforward compensation, which drives the high-pressure valve and the low-pressure valve to perform feedforward compensation opening adjustment.

[0107] The hot-state test was conducted under stable operating conditions of 280MW load for Unit #3. The test conditions were as follows: the #3A steam-driven feedwater pump was operated by auxiliary steam; after the #3B steam-driven feedwater pump was spun to 2800rpm by the fourth-stage extraction steam, a thorough condensate draining operation was performed on the fourth-stage extraction steam and cold reheat steam pipelines; the manual condensate drain valve from the high-pressure regulating valve of the #3B steam-driven feedwater pump to the low-pressure inlet steam was kept open to reduce the risk of water backflow in the fourth-stage extraction steam pipeline; the electric valve at the outlet of the #3B steam-driven feedwater pump was kept closed, and the recirculation regulating valve was fully open to ensure that the feedwater flow during the test was entirely through the recirculation regulating valve and did not affect the unit's feedwater flow.

[0108] After the above test conditions are met, the #3B steam-driven feedwater pump is revved to 4500 rpm at a revving rate of 150 rpm / min. The thermal control personnel confirm that the judgment conditions of steps S11 to S13 of the #3B steam-driven feedwater pump are not met. After confirming that the triggering condition for the intervention of the high-pressure regulating valve is not met, the operators switch the anti-backflow control function to the active state on the MEH operation screen to meet the preset active load threshold of 300MW described in step S16.

[0109] The thermal control personnel force the judgment conditions of steps S11 to S13 to be true in the DCS system, triggering the high-pressure regulating valve to overshoot to the initial opening degree of 20% as described in step S1. The opening position of the high-pressure regulating valve is calculated and determined by the regulating valve general command output by the speed closed-loop controller, corresponding to the overshoot opening degree command of the initial opening degree of 20% as described in step S15.

[0110] After the high-pressure regulating valve overrides, the switching logic in the DCS system switches the high-pressure regulating valve into a control mode that follows the overall regulating valve command. The high-pressure and low-pressure regulating valves then jointly follow the overall regulating valve command into the joint speed regulation stage described in step S2. After the high-pressure regulating valve intervenes, the speed of the steam-driven feedwater pump briefly increases due to the rapid replenishment of high-pressure cold reheat steam. Subsequently, the speed closed-loop controller, based on the speed deviation adjustment regulating valve command described in step S21, drives the high-pressure and low-pressure regulating valves to synchronously reduce their openings. The speed of the steam-driven feedwater pump decreases and eventually converges to a stable value near the setpoint. The time from speed change to stability and the actions of the high- and low-pressure regulating valves during the above regulation process are recorded. It is confirmed that the instantaneous speed fluctuation converges to within ±30 r / min, and the deviation correction opening adjustment described in step S21 and the feedforward compensation opening adjustment described in step S22 are executed in synergy, resulting in stable joint regulation of the high- and low-pressure regulating valves.

[0111] After completing the above adjustment verification, the speed setting value of the #3B steam-driven feedwater pump was adjusted to 5000 rpm and 4000 rpm in sequence. The combined adjustment performance described in steps S21 and S22 was verified respectively. The adjustment time from setting to stabilization of speed under each working condition was recorded to confirm that the combined adjustment of high and low gates is stable and the instantaneous fluctuation of speed does not exceed ±30 r / min.

[0112] S3. During the combined speed regulation process, when the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source of the low-pressure steam source, a manual exit command is received, and the high-pressure regulating valve is controlled to close gradually at a preset controlled exit rate until it is fully closed, so that the steam-driven feedwater pump returns to the single low-pressure steam source regulation state.

[0113] Under the stable operating condition of 4000 rpm, perform the pressure acquisition described in step S33, confirm on the MEH operation screen that the measured value of the four-stage extraction steam pressure is greater than the measured value of the deaerator pressure, and simultaneously confirm that the instantaneous fluctuation of the steam-driven feedwater pump speed does not exceed ±30 r / min, and that the feedwater flow rate and feedwater pressure stably follow the load command, thus meeting the exit prerequisite conditions described in step S34.

[0114] After the above exit prerequisites are met, the operator manually issues an exit command on the MEH operation screen. After the MEH controller receives the manual exit command, step S17 synchronously stops the judgment of the judgment conditions in steps S11 to S13. The logic selector tracking loop described in step S31 is activated, and the high-voltage regulating valve opening command is controlled to decrease from the current opening position at a controlled exit rate of 0.1% / s, and the controlled exit process described in step S32 is executed.

[0115] Record the instantaneous fluctuation range of the steam-driven feedwater pump at 4000 rpm during the controlled exit of the high-pressure control valve, and confirm that the instantaneous speed fluctuation during the controlled exit does not exceed ±30 r / min. When the opening command of the high-pressure control valve decreases to zero, the steam-driven feedwater pump returns to the single low-pressure steam source regulation state, and the low-pressure control valve independently follows the overall control valve command to perform speed regulation. Step S3 is then completed.

[0116] After the test, based on the time it takes for the speed to stabilize, the high and low valve operation, and the instantaneous speed fluctuation range during the controlled exit process recorded during the test, the rationality of the parameter settings, such as the preset change rate threshold of 0.8℃ / s in step S11, the preset load threshold of 460MW and the preset opening threshold of 57.5% in step S13, the initial opening of 20% in step S15, and the controlled exit rate of 0.1% / s in step S31, is evaluated. Based on the evaluation results, the above parameters are adjusted accordingly to match the parameter settings of the anti-backflow control method with the actual operating conditions of the unit.

[0117] The above hot-state test verification results show that, under the actual operating conditions of Unit #3, the anti-backflow control method described in steps S1 to S3 has a rapid response to the intervention of the high-pressure regulating valve, stable combined high-pressure and low-pressure valve speed regulation, and instantaneous speed fluctuation during the controlled exit process does not exceed ±30 r / min. Figure 2 The comparison with the accident condition without high-pressure steam source intervention verifies the effectiveness of the anti-backflow control method described in steps S1 to S3.

[0118] Example 3 is an embodiment of the present invention, which provides a steam-driven feedwater pump anti-backflow control system, including: The parameter acquisition module is used to acquire multiple operating parameters on the low-pressure steam inlet side of the steam-driven feedwater pump and output the multiple operating parameters to the abnormal state judgment module. An abnormal state judgment module is connected to the parameter acquisition module and is used to judge multiple low-pressure steam source abnormal state judgment conditions based on the multi-channel operating parameters. When any one of the low-pressure steam source abnormal state judgment conditions is met, a trigger signal is output to the override control module. The override control module is connected to the abnormal state judgment module. After receiving the trigger signal, it controls the high-voltage regulating valve to override open to a preset initial opening degree, and outputs a cut-in signal to the joint regulation module after the high-voltage regulating valve completes the override opening. The joint adjustment module is connected to the override control module and the speed closed-loop controller. After receiving the cut-in signal, it controls the high-pressure regulating valve and the low-pressure regulating valve to jointly perform joint speed adjustment in accordance with the regulating valve general command output by the speed closed-loop controller. The controlled exit module, connected to the joint regulation module, is used to receive a manual exit command when the low-pressure steam source pressure is greater than the pressure of the upstream connected steam source during the joint speed regulation process. The controlled exit rate is used to control the opening command of the high-pressure regulating valve to decrease to full closure, so that the steam-driven feedwater pump returns to the single low-pressure steam source regulation state. The commissioning / decommissioning management module is connected to the abnormal state judgment module. It is used to control the abnormal state judgment module to perform the judgment when the unit load is greater than the preset commissioning load threshold, and to control the abnormal state judgment module to stop the judgment when the manual decommissioning command is received.

[0119] This embodiment also provides an electronic device applicable to a steam-driven feedwater pump anti-backflow control method, comprising: a memory and a processor; the memory is used to store computer-executable instructions, and the processor is used to execute the computer-executable instructions to implement the steam-driven feedwater pump anti-backflow control method proposed in the above embodiment.

[0120] This embodiment also provides a storage medium storing a computer program that, when executed by a processor, implements a steam-driven feedwater pump anti-backflow control method as proposed in the above embodiment.

[0121] The storage medium proposed in this embodiment and the method for preventing backflow control of a steam-driven feedwater pump proposed in the above embodiments belong to the same inventive concept. Technical details not described in detail in this embodiment can be found in the above embodiments, and this embodiment has the same beneficial effects as the above embodiments.

[0122] Based on the above description of the implementation methods, those skilled in the art can clearly understand that the present invention can be implemented using software and necessary general-purpose hardware, and of course, it can also be implemented using hardware, but in many cases the former is a better implementation method. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a computer-readable storage medium, such as a computer floppy disk, read-only memory (ROM), random access memory (RAM), flash memory, hard disk, or optical disk, etc., including several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods of the various embodiments of the present invention.

[0123] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for preventing backflow of steam in a steam-driven feedwater pump, characterized in that, include: Based on the multi-path operating parameters of the low-pressure steam inlet side, multiple low-pressure steam source abnormal state judgment conditions are determined respectively. When any one of the multiple low-pressure steam source abnormal state judgment conditions is met, the high-pressure regulating valve is controlled to overshoot and open to the preset initial opening degree. When the high-pressure regulating valve completes the override opening, the high-pressure regulating valve and the low-pressure regulating valve are controlled to jointly perform joint speed regulation in accordance with the regulating valve general command output by the speed closed-loop controller; During the combined speed regulation process, when the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source of the low-pressure steam source, a manual exit command is received, and the high-pressure regulating valve is controlled to close gradually at a preset controlled exit rate until it is fully closed, so that the steam-driven feedwater pump returns to the single low-pressure steam source regulation state.

2. The method for preventing backflow of steam in a steam-driven feedwater pump as described in claim 1, characterized in that, The conditions for determining the abnormal state of the multiple low-pressure steam sources include: The low-pressure steam source abnormal state determination condition is met when the number of measuring points whose temperature change rate exceeds the preset change rate threshold reaches the preset number threshold. When the measured value of the low-pressure steam inlet temperature is less than the preset lower limit threshold, the condition for determining the abnormal state of the low-pressure steam source is met. When the unit load is less than the preset load threshold and the low-pressure regulating valve opening is greater than the preset opening threshold, the low-pressure steam source abnormal state determination condition is met.

3. The method for preventing backflow of steam in a steam-driven feedwater pump as described in claim 2, characterized in that, The determination of the preset initial opening degree includes: Collect historical pressure data of high-pressure steam source and low-pressure steam source under various operating conditions, and calculate the pressure ratio between high-pressure steam source and low-pressure steam source based on the historical pressure data; Based on the pressure ratio, the compensation opening of the high-pressure regulating valve under the maximum opening condition of the low-pressure regulating valve is calculated, and the compensation opening is used as the initial opening.

4. The method for preventing backflow of steam in a steam-driven feedwater pump as described in claim 3, characterized in that, The combined speed regulation includes: The speed closed-loop controller adjusts the general command of the regulating valve based on the deviation between the speed of the steam-driven feedwater pump and the preset speed setting value, and drives the high-pressure regulating valve and the low-pressure regulating valve to perform deviation correction opening adjustment; The speed closed-loop controller performs feedforward compensation on the total command of the regulating valve based on the water supply flow command, and drives the high-pressure regulating valve and the low-pressure regulating valve to perform feedforward compensation opening adjustment.

5. The method for preventing backflow of steam in a steam-driven feedwater pump as described in claim 4, characterized in that, The pre-set controlled exit rate is controlled by a logic selector tracking loop, and the controlled exit rate is determined based on the target exit time of the high-voltage regulating valve from the initial opening to full closure; When the manual exit command is received, the logic selector tracking loop controls the opening command of the high-voltage regulating valve to decrease at the controlled exit rate until the high-voltage regulating valve is closed completely.

6. The method for preventing backflow of steam in a steam-driven feedwater pump as described in claim 5, characterized in that, When the unit load exceeds the preset load threshold, the judgment of the multiple low-pressure steam source abnormal state determination conditions is executed. When the manual exit command is received, the judgment of the multiple low-pressure steam source abnormal state determination conditions is stopped.

7. The method for preventing backflow of steam in a steam-driven feedwater pump as described in claim 6, characterized in that, The determination that the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source includes: Obtain the pressure of the low-pressure steam source and the pressure of the steam source connected upstream of the low-pressure steam source; When the pressure of the low-pressure steam source is greater than the pressure of the upstream connected steam source, the manual exit command can be received.

8. A steam-driven feedwater pump anti-backflow control system, employing the steam-driven feedwater pump anti-backflow control method as described in any one of claims 1 to 7, characterized in that, include: The parameter acquisition module is used to acquire multiple operating parameters on the low-pressure steam inlet side of the steam-driven feedwater pump and output the multiple operating parameters to the abnormal state judgment module. An abnormal state judgment module is connected to the parameter acquisition module and is used to judge multiple low-pressure steam source abnormal state judgment conditions based on the multi-channel operating parameters. When any one of the low-pressure steam source abnormal state judgment conditions is met, a trigger signal is output to the override control module. The override control module is connected to the abnormal state judgment module. After receiving the trigger signal, it controls the high-voltage regulating valve to override open to a preset initial opening degree, and outputs a cut-in signal to the joint regulation module after the high-voltage regulating valve completes the override opening. The joint adjustment module is connected to the override control module and the speed closed-loop controller. After receiving the cut-in signal, it controls the high-pressure regulating valve and the low-pressure regulating valve to jointly perform joint speed adjustment in accordance with the regulating valve general command output by the speed closed-loop controller. The controlled exit module, connected to the joint regulation module, is used to receive a manual exit command during the joint speed regulation process when the low-pressure steam source pressure is greater than the pressure of the upstream connected steam source of the low-pressure steam source, and control the opening command of the high-pressure regulating valve to decrease to full closure at a preset controlled exit rate. The commissioning / decommissioning management module is connected to the abnormal state judgment module. It is used to control the abnormal state judgment module to perform the judgment when the unit load is greater than the preset commissioning load threshold, and to control the abnormal state judgment module to stop the judgment when the manual decommissioning command is received.

9. A computer device comprising a memory and a processor, wherein the memory stores a computer program, characterized in that, When the processor executes the computer program, it implements the steps of the steam-driven feedwater pump anti-backflow control method according to any one of claims 1 to 7.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the steps of the anti-backflow control method for a steam-driven feedwater pump according to any one of claims 1 to 7.

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