A control method for water supply recirculation regulating valve

Abstract

The present invention relates to the technical field of boiler control, and discloses a control method for a feedwater recirculation regulating valve, including the following aspects: (1) recirculation operation process, when the pressure exceeds a certain set value, the minimum flow valve opens; when the pressure is lower than a certain set value, the minimum flow valve closes; (2) system optimization and regulation, the feedwater pump minimum flow control system only works in the feedwater pump startup and low load stages; (3) intelligent feedforward optimization of the recirculation gate, adding feedforward control, and constructing precise intelligent feedforward according to typical operating test data and unit operation data; (4) automatic optimization of the recirculation gate; (5) optimization of feedwater recirculation protection logic. Compared with the prior art, the advantages are: by optimizing the control strategy and adjusting the parameters of the steam pump recirculation regulating valve, the steam pump flow and the boiler feedwater flow can be effectively controlled within the required deviation range in the low load stage of the unit, thereby improving the safety and stability of the unit in the deep peak regulation stage.

Description

Technical Field

[0001] The invention relates to the technical field of boiler control, and in particular to a control method for a feedwater recirculation regulating valve. Background Art

[0002] With the upgrading of my country's power industry structure and the rapid development of renewable energy, thermal power units will assume the functional role of deep peak regulation of the power grid, with flexible adjustment from low load to medium and high load as its main operating mode, and frequent low-load operating conditions put forward higher requirements for machine and boiler equipment and control systems. Conventional feedwater control logic sets the minimum flow protection system for feedwater to ensure the safe operation of the feedwater pump under low load. The system includes recirculation pipes, feedwater flow recirculation valves, electric stop valves before and after recirculation regulation, differential pressure transmitters and process controllers, among which the minimum flow recirculation valve is the most critical equipment. During the low-load operation of the unit, if the actual feedwater flow of the boiler continues to decrease, when the outlet flow of the feedwater pump is lower than the minimum flow recirculation valve opening limit, the recirculation valve will automatically open, bypassing part of the feedwater back to the deaerator, thereby increasing the working medium flow through the feedwater pump, avoiding overheating and cavitation of the feedwater pump, and reducing the operating damage of the pump body.

[0003] Under deep peak load regulation conditions, the unit load frequently reaches the load point below 30% Pe, and the low flow rate of the feedwater pump continues to exist, causing the protection of the minimum flow recirculation valve to frequently operate, resulting in large fluctuations in the feedwater flow and serious wear of the minimum flow valve.

[0004] (1) Conventional recirculation valve control strategy cannot adapt to deep peak load operation

[0005] The conventional protection logic for the minimum flow of the water feed pump adopts the basic PID control method, and the manually set fixed value is used as the flow control target. When the outlet flow of the water feed pump is less than the set value, the opening of the recirculation valve increases to increase the inlet flow of the water feed pump; when the actual flow is higher than the set value, the recirculation valve is closed through the PID pullback effect. However, under long-term low-load operation, the water feed pump often works near the minimum flow. The overshoot phenomenon in the PID control process will frequently trigger the switch of the minimum flow valve, which is not conducive to the stable operation of the water supply system and the safe operation of the water feed pump.

[0006] (2) The minimum flow recirculation valve of the water supply pump is prone to wear.

[0007] The minimum flow recirculation valve is installed between the outlet of the water pump and the deaerator water tank. The pressure difference between the inlet and outlet of the valve is about 20Mpa, and it always works under high pressure difference. Therefore, the working fluid after the valve throttling is prone to flash evaporation and cavitation, especially under low load, the valve is very easy to wear during frequent opening. In actual operation, it should be considered to avoid the recirculation valve working at a small opening, otherwise it will seriously accelerate the wear of the equipment and sacrifice the equipment life.

[0008] (3) Intensify the disturbance of water supply control circuit under low load

[0009] Under deep peak load operation, for the purpose of minimum flow valve protection, the minimum opening limit of the feedwater recirculation valve can be set and the valve dead zone can be set to directly cross the small opening range of excessive throttling. However, due to the weak stability of the unit under low load, when the recirculation valve is instantly opened or closed, the sudden change of the feedwater flow will inevitably bring control disturbances to the water supply system, and even cause system oscillation and divergence.

[0010] Intelligent feedforward optimization of the recirculation gate. Most of the water recirculation valve controls are open-loop control systems. There is only a positive output effect between the controller valve and the controlled valve opening. There is no feedback signal involved in the implementation. The controller only controls based on signals that directly or indirectly reflect the disturbance input. This control mode has a certain lag and cannot timely feedback deviations and perform control adjustments. Summary of the invention

[0011] The technical problem to be solved by the present invention is to overcome the above technical difficulties and provide a control method for a water supply recirculation regulating valve.

[0012] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0013] A control method for a water supply recirculation regulating valve comprises the following aspects:

[0014] (1) Recycling operation process;

[0015] (2) System optimization and adjustment;

[0016] (3) Intelligent feed-forward optimization of recirculation gate;

[0017] (4) Automatic optimization of recirculation gate;

[0018] (5) Optimization of water recirculation protection logic.

[0019] As an improvement, recirculation operation is used: when the operating conditions require the boiler load to be reduced, the corresponding required feedwater pump output is reduced. If the load continues to decrease, the flow output of the feedwater pump may be lower than the minimum allowable flow, that is, 25%-30%. At this time, the minimum flow valve is opened in time to return a part of the high-pressure water from the pump outlet to the deaerator; the system where the valve is located is called the recirculation system, which is used for general boiler feedwater pumps. The pump outlet pressure is used to control the system. A pressure switch is installed on the pump outlet main pipe. When the pressure exceeds a certain set value, the minimum flow valve opens; when the pressure is lower than a certain set value, the minimum flow valve closes; recirculation is used to allow the feedwater pump to pass enough water, and the excess feedwater returns to the deaerator tank.

[0020] As an improvement, the system is optimized and regulated: because the minimum flow control system of the feedwater pump is usually a single-loop regulation system, the flow measurement generally adopts two-out-of-one method; the minimum flow control system of the feedwater pump only works during the startup and low-load stages of the feedwater pump; as long as the boiler feedwater flow is greater than the minimum flow setting, the feedwater recirculation regulating valve is closed; the minimum flow regulating valve is designed to act in the opposite direction, that is, when the control system outputs 0%, the valve is fully open; when the output is 100%, the valve is fully closed; the change of valve opening from fully open to fully closed or fully closed to fully open will cause a large disturbance in the feedwater flow, posing a safety hazard to the safe operation of related equipment in the plant, so the opening of the regulating valve and the corresponding change speed are optimized and regulated.

[0021] As an improvement, the intelligent feedforward optimization of the recirculation gate is carried out: feedforward control is added, and a multi-broken line function precise intelligent feedforward is constructed according to typical operating condition test data and unit operation data. The disturbance signal X at the input end of the control object is accepted. Once a disturbance occurs, the controller can produce a control action U on the controlled object according to the predetermined control law to offset the influence of the disturbance X on the controlled quantity Y.

[0022] As an improvement, the recirculation door is automatically optimized: by adding feedback adjustment control, it is combined into a composite control system; according to the deviation between the regulated quantity and its specified value, through continuous feedback and control, the recirculation door opening under various load and pressure conditions is accurately calculated to ensure the safety of the pump group and the stability of the water supply flow;

[0023] Change the water recirculation gate to an automatic adjustment gate, add feedforward + PID adjustment automatic logic, optimize and adjust PID automatic parameters, and ensure that the automatic adjustment quality of the water recirculation gate can be fast and accurate; PID adjustment is mainly used to eliminate control deviation in the control loop, and at the same time, reversely suppress the feedforward control effect to accelerate control convergence; PID adjustment controller has the characteristics of three control effects: P, I, and D; P control ensures the stability of the process; I control ensures that the control result is the same; D control compensates for the delay and habituation of the control object; adjust the various parameters of the PID controller to match the dynamic characteristics of the controlled process to meet the performance indicators of the production process for the control system;

[0024] The adjustment parameters are selected and adjusted according to the load increase and decrease conditions and the deviation between the actual flow and the set value. During the load increase process, as the steam pump speed increases, the actual flow gradually exceeds the set value. In this process, the integral effect is gradually reduced to prevent the integral from overshooting, so as to smoothly close the recirculation valve to full closure. At the same time, the proportional strength is weakened to prevent valve oscillation caused by the proportional effect after the integral is weakened. During the load reduction process, the steam pump flow gradually decreases. When the steam pump flow is still higher than the set value within a certain range, a weaker proportional and integral effect is used to gradually open the recirculation valve through the feedforward effect and the opening rate limit. As the steam pump flow decreases, the integral and proportional effects are gradually strengthened, and they cooperate with the feedforward and rate limit to prevent overshoot while converging quickly. After the steam pump flow reaches the set value, the strength relationship between the proportion and the integral is matched, the advantages of PID regulation are brought into play, the control deviation is reduced, the normal rate is maintained, and the PID regulation is avoided due to the rate limit. After the steam pump flow further decreases to below the set value, the PID regulation effect is further strengthened and the limiting rate is accelerated to prevent the recirculation valve from overrunning and opening due to a too fast decrease in flow.

[0025] As an improvement, the water supply recirculation protection logic is optimized: the water supply recirculation automatic protection logic is added, the recirculation automatic start and stop conditions are determined, the protection logic is automatically exited, and the flow valve control logic maintains 100% execution control of the valve program control for a long time. When adjustment is required, the logic program immediately executes the corresponding control to keep the valve's single adjustment opening no more than 5%-10%, so that the water supply flow is output stably; when the flow is stable within the set value range, the logic control program resumes and maintains the tracking state, performs real-time detection, and performs optimization and adjustment when necessary. At the same time, the manual and automatic disturbance-free switching logic is guaranteed to ensure the automatic and safe cutting of the water supply recirculation.

[0026] The advantages of the present invention over the prior art are that by optimizing the control strategy and adjusting the parameters of the steam pump recirculation regulating valve, the steam pump flow and the boiler feed water flow can be effectively controlled within the required deviation range during the low load stage of the unit, thereby improving the safety and stability of the unit's operation during the deep peak regulation stage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the composite control system of the present invention.

[0028] Figure 2 It is a schematic diagram of the feedforward control of the present invention.

[0029] Figure 1 Feedforward control. To address the control drawback of hysteresis, this patent adopts the method of adding feedforward control. According to the typical operating test data and unit operation data, a multi-broken line function precise intelligent feedforward is constructed to receive the disturbance signal X at the input end of the control object. Once a disturbance occurs, the controller can generate a control action U on the controlled object according to the predetermined control law to offset the influence of the disturbance X on the controlled quantity Y.

[0030] Figure 2 The block diagram of the composite control system. Automatic optimization of the recirculation gate When the control quantity of the disturbance is appropriate, it is possible to offset the influence of the disturbance in time, and reduce the influence of the disturbance on the controlled quantity. Since there is no feedback of the controlled quantity, it cannot be completely guaranteed that the valve opening meets the requirements after the control is executed, but it is very effective and desirable to control by means of disturbance compensation. By adding feedback adjustment control, it can be combined into a composite control system. According to the deviation between the controlled quantity and its specified value, through continuous feedback and control, the recirculation gate opening under various load and pressure conditions can be accurately calculated to ensure the safety of the pump group and the stability of the water supply flow. DETAILED DESCRIPTION

[0031] In the description of the present invention, unless otherwise specified, "plurality" means two or more. In addition, the term "include" and any variations thereof are intended to cover non-exclusive inclusions.

[0032] Under the premise of protecting the safety of low-load operation of the water supply pump, the opening rate and opening curve of the water supply recirculation valve are limited to avoid low-opening operation of the water supply recirculation valve and reduce the wear of the water supply recirculation valve; and at the moment when the water supply recirculation valve is opened or closed, the water supply system is fed-forward compensated for the water volume to reduce the control disturbance of the water supply system caused by the large movement of the water supply recirculation valve under low load, thereby achieving the comprehensive goals of safety, energy saving and improved control stability of the water supply system under low load.

[0033] In view of this control drawback, feedforward control is added. According to typical operating test data and unit operation data, a multi-broken line function precise intelligent feedforward is constructed to accept the disturbance signal X at the input end of the control object. Once a disturbance occurs, the controller can produce a control action U on the controlled object according to the predetermined control law to offset the influence of the disturbance X on the controlled quantity Y. The feedwater recirculation gate is changed to an automatic adjustment gate, and the feedforward + PID adjustment automatic logic is added. The PID automatic parameters are optimized and set to ensure that the automatic adjustment quality of the feedwater recirculation gate can be fast and accurate.

[0034] This project targets large-scale new energy grid-connected converter cluster systems, focuses on achieving highly intelligent stand-alone machines, and conducts in-depth research in order to realize technical solutions for smart, efficient, and reliable grid-connected consumption of new energy.

[0035] Adopt PID+flow feedforward joint control, use the valve opening corresponding to a certain flow intensity as the adjustment feedforward to ensure the timeliness and rapidity of valve opening; use the PID integral link to eliminate the deviation, suppress the feedforward, accelerate the control convergence and eliminate the deviation. Add feedback adjustment control and combine it into a composite control system. According to the deviation between the controlled quantity and its specified value, through continuous feedback and control, accurately calculate the recirculation door opening under various load and pressure conditions to ensure the safety of the pump group and the stability of the water supply flow. The feedforward action is divided into two working conditions: open and closed. A fast circuit is used when opening, and a slow circuit is used when closing to reduce the adjustment oscillation caused by the feedforward action.

[0036] The PID link adopts variable parameter control to perform bidirectional variable parameter control on the PID proportional and integral action according to the deviation between the steam pump flow setting value and the measured value. When the steam pump flow is greater than the set value, the proportional action is appropriately weakened, and the integral action is mainly weakened to prevent the regulating valve from closing too much due to the excessive integral action when the deviation is large, thereby causing the steam pump flow to be too low; when the steam pump flow drops to a certain range close to the set value, the proportional and integral regulation effects are gradually strengthened to prevent the recirculation valve from opening too slowly due to the weak regulation effect, causing the steam pump flow to drop too low.

[0037] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0038] A control method for a water supply recirculation regulating valve;

[0039] (1) Recycling operation process

[0040] When the operating conditions require the boiler load to be reduced, the corresponding required feedwater pump output will decrease. If the load continues to decrease, the flow output of the feedwater pump may be lower than the minimum allowable flow (25%-30%). At this time, it is necessary to open the minimum flow valve in time to return part of the high-pressure water from the pump outlet to the deaerator to ensure the safe operation of the feedwater pump.

[0041] The system where this valve is located is called a recirculation system. It is used for general boiler feed water pumps, which are controlled by the outlet pressure of the pump. A pressure switch is installed on the outlet pipe of the pump. When the pressure exceeds a certain set value, the minimum flow valve opens; when the pressure is lower than a certain set value, the minimum flow valve closes. Recirculation can allow the feed water pump to pass sufficient water, and the excess feed water returns to the deaerator water tank, which can ensure the working conditions of the feed water pump and enable it to operate safely.

[0042] (2) System optimization and adjustment

[0043] Because the minimum flow control system of the feedwater pump is usually a single-loop regulation system, the flow measurement is generally one-out-of-two. The minimum flow control system of the feedwater pump only works during the start-up and low-load stages of the feedwater pump; as long as the boiler feedwater flow is greater than the minimum flow setting, the feedwater recirculation regulating valve will be closed. The minimum flow regulating valve is usually designed to act in the opposite direction, that is, when the control system outputs 0%, the valve is fully open; when the output is 100%, the valve is fully closed. The change in valve opening from fully open to fully closed (valve opening 0%-100%) or fully closed to fully open will cause a large disturbance in the feedwater flow, causing safety hazards to the safe operation of related equipment in the plant. In order to avoid this situation and ensure the stable output regulation of the feedwater flow, the opening of the regulating valve and the corresponding change speed will be optimized and adjusted.

[0044] (3) Intelligent feed-forward optimization of recirculation gate

[0045] Most of the water recirculation valve controls are open-loop control systems. There is only a positive output effect between the controller valve and the opening of the controlled valve, and there is no feedback signal involved. The controller only controls based on signals that directly or indirectly reflect the disturbance input. This control mode has a certain lag and cannot provide timely feedback on deviations or perform control adjustments.

[0046] To address this control drawback, we adopt feedforward control, build a multi-broken line function precise intelligent feedforward based on typical operating test data and unit operation data, and accept the disturbance signal X at the input end of the control object. Once a disturbance occurs, the controller can produce a control action U on the controlled object according to the predetermined control law to offset the influence of the disturbance X on the controlled quantity Y. Figure 1 shown.

[0047] (4) Automatic optimization of recirculation gate

[0048] When the control amount of the disturbance is appropriate, it is possible to offset the influence of the disturbance in time, and reduce the influence of the disturbance on the controlled quantity. Since there is no feedback of the controlled quantity, it is not possible to completely guarantee that the valve opening meets the requirements after the control is executed, but it is very effective and desirable to control by means of disturbance compensation. By adding feedback regulation control, it is combined into a composite control system, such as Figure 2 According to the deviation between the controlled quantity and its specified value, through continuous feedback and control, the recirculation door opening under various load and pressure conditions is accurately calculated to ensure the safety of the pump group and the stability of the water supply flow.

[0049] Change the water recirculation gate to an automatic adjustment gate, add feedforward + PID adjustment automatic logic, optimize and adjust PID automatic parameters, and ensure that the automatic adjustment quality of the water recirculation gate can be fast and accurate. PID adjustment is mainly used to eliminate control deviations in the control loop, while reversely suppressing the feedforward control effect and accelerating control convergence. The PID adjustment controller has the characteristics of three control effects: P, I, and D. P control ensures the stability of the process; I control ensures that the control results are the same; D control compensates for the delay and habituation of the control object. Since the dynamic characteristics of the controlled process are different, only by adjusting the various parameters of the PID controller to match the dynamic characteristics of the controlled process can the performance indicators of the control system for the production process be met.

[0050] The adjustment parameters are selected and adjusted according to the load increase and decrease conditions and the deviation between the actual flow and the set value. During the load increase process, as the steam pump speed increases, the actual flow gradually exceeds the set value. In this process, the integral effect is gradually reduced to prevent the integral from overshooting, so as to smoothly close the recirculation valve to full closure; at the same time, the proportional strength is weakened to prevent valve oscillation caused by the proportional effect after the integral is weakened. During the load reduction process, the steam pump flow gradually decreases. When the steam pump flow is still higher than the set value within a certain range, a weaker proportional and integral effect is used to gradually open the recirculation valve through the feedforward effect and the opening rate limit. As the steam pump flow decreases, the integral and proportional effects are gradually strengthened, and they cooperate with the feedforward and rate limit to prevent overshoot while converging quickly; after the steam pump flow reaches the set value, the strength relationship between the proportion and the integral is matched, the advantages of PID regulation are brought into play, the control deviation is reduced, the normal rate is maintained, and the PID regulation is avoided due to the rate limit; after the steam pump flow further decreases to below the set value, the PID regulation effect is further strengthened and the limiting rate is accelerated to prevent the recirculation valve from overrunning and opening due to the rapid decrease in flow.

[0051] (5) Optimization of water recirculation protection logic

[0052] Increase the automatic protection logic for water supply recirculation, determine the automatic start and stop conditions for recirculation, automatically exit the protection logic, and the flow valve control logic maintains 100% execution control of the valve program control. When adjustment is required, the logic program immediately executes the corresponding control to keep the single adjustment opening of the valve no more than 5%-10%, so that the water supply flow is output stably; when the flow is stable within the set value range, the logic control program resumes and maintains the tracking state, performs real-time detection, and performs optimization and adjustment when necessary. At the same time, the manual and automatic disturbance-free switching logic is guaranteed to ensure the automatic and safe cutting of water supply recirculation.

[0053] The present invention and its embodiments are described above, and such description is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. In short, if ordinary technicians in the field are inspired by it, without departing from the purpose of the invention, they can design a structure and embodiment similar to the technical solution without creativity, which should belong to the protection scope of the present invention.

Claims

1. A control method for a water supply recirculation regulating valve, characterized in that: Including the following aspects: (1) Recycling operation process; (2) System optimization and adjustment; (3) Intelligent feed-forward optimization of recirculation gate; (4) Automatic optimization of recirculation gate; (5) Optimization of water recirculation protection logic.

2. A control method for a water supply recirculation regulating valve according to claim 1, characterized in that: Recirculation operation: When the operating conditions require the boiler load to be reduced, the corresponding required feedwater pump output will decrease. If the load continues to decrease, the flow output of the feedwater pump may be lower than the minimum allowable flow, that is, 25%-30%. At this time, open the minimum flow valve in time to return part of the high-pressure water from the pump outlet to the deaerator; The system where this valve is located is called a recirculation system. It is used for general boiler feed water pumps, which are controlled by the pump's outlet pressure. A pressure switch is installed on the pump's outlet main pipe. When the pressure exceeds a certain set value, the minimum flow valve opens; when the pressure is lower than a certain set value, the minimum flow valve closes. Recirculation is used to allow the feed water pump to pass sufficient water, and the excess feed water returns to the deaerator tank.

3. A control method for a water supply recirculation regulating valve according to claim 2, characterized in that: Optimization and adjustment of the system: Because the minimum flow control system of the feedwater pump is usually a single-loop regulation system, the flow measurement generally adopts two-out-of-one method; the minimum flow control system of the feedwater pump only works during the start-up and low-load stages of the feedwater pump; as long as the boiler feedwater flow is greater than the minimum flow setting, the feedwater recirculation regulating valve will be closed; the minimum flow regulating valve is designed to act in the opposite direction, that is, when the control system outputs 0%, the valve is fully open; when the output is 100%, the valve is fully closed; the change of valve opening from fully open to fully closed or fully closed to fully open will cause a large disturbance in the feedwater flow, posing a safety hazard to the safe operation of related equipment in the plant, so the opening of the regulating valve and the corresponding change speed are optimized and adjusted.

4. A control method for a water supply recirculation regulating valve according to claim 3, characterized in that: Recirculation gate intelligent feed-forward optimization: Add feedforward control, build a multi-broken line function precise intelligent feedforward according to typical operating test data and unit operation data, accept the disturbance signal X at the input end of the control object, once a disturbance occurs, the controller can produce a control action U on the controlled object according to the predetermined control law to offset the influence of the disturbance X on the controlled quantity Y.

5. A control method for a water supply recirculation regulating valve according to claim 4, characterized in that: Automatic optimization of recirculation gate: By adding feedback regulation control, it is combined into a composite control system; according to the deviation between the regulated quantity and its specified value, through continuous feedback and control, the recirculation door opening under various load and pressure conditions is accurately calculated to ensure the safety of the pump group and the stability of the water supply flow; Change the water recirculation gate to an automatic adjustment gate, add feedforward + PID adjustment automatic logic, optimize and adjust PID automatic parameters, and ensure that the automatic adjustment quality of the water recirculation gate can be fast and accurate; PID adjustment is mainly used to eliminate control deviation in the control loop, and at the same time, reversely suppress the feedforward control effect to accelerate control convergence; PID adjustment controller has the characteristics of three control effects: P, I, and D; P control ensures the stability of the process; I control ensures that the control result is the same; D control compensates for the delay and habituation of the control object; adjust the various parameters of the PID controller to match the dynamic characteristics of the controlled process to meet the performance indicators of the production process for the control system; The adjustment parameters are selected and adjusted according to the load increase and decrease conditions and the deviation between the actual flow and the set value. During the load increase process, as the steam pump speed increases, the actual flow gradually exceeds the set value. In this process, the integral effect is gradually reduced to prevent the integral from overshooting, so as to smoothly close the recirculation valve to full closure. At the same time, the proportional strength is weakened to prevent valve oscillation caused by the proportional effect after the integral is weakened. During the load reduction process, the steam pump flow gradually decreases. When the steam pump flow is still higher than the set value within a certain range, a weaker proportional and integral effect is used to gradually open the recirculation valve through the feedforward effect and the opening rate limit. As the steam pump flow decreases, the integral and proportional effects are gradually strengthened, and they cooperate with the feedforward and rate limit to prevent overshoot while converging quickly. After the steam pump flow reaches the set value, the strength relationship between the proportion and the integral is matched, the advantages of PID regulation are brought into play, the control deviation is reduced, the normal rate is maintained, and the PID regulation is avoided due to the rate limit. After the steam pump flow further decreases to below the set value, the PID regulation effect is further strengthened and the limiting rate is accelerated to prevent the recirculation valve from overrunning and opening due to a too fast decrease in flow.

6. A control method for a water supply recirculation regulating valve according to claim 5, characterized in that: Feedwater recirculation protection logic optimization: Increase the automatic protection logic for water supply recirculation, determine the automatic start and stop conditions for recirculation, automatically exit the protection logic, and the flow valve control logic maintains 100% execution control of the valve program control. When adjustment is required, the logic program immediately executes the corresponding control to keep the single adjustment opening of the valve no more than 5%-10%, so that the water supply flow is output stably; when the flow is stable within the set value range, the logic control program resumes and maintains the tracking state, performs real-time detection, and performs optimization and adjustment when necessary. At the same time, the manual and automatic disturbance-free switching logic is guaranteed to ensure the automatic and safe cutting of water supply recirculation.

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