Boiler feed water safety protection method and system based on PID and electrode water level double-mode control

Abstract

The present application proposes a boiler feed water safety protection method and system based on PID and electrode water level double-mode control, the method comprising: obtaining the state changes of high water level, normal water level and low water level electrodes, recording the water level events containing electrode number, triggering time and change direction to form a sequence; generating an abnormal evolution state according to the electrode number, triggering time and change direction of each event in the observation section in the sequence; generating a recovery demand state according to the abnormal evolution state; comparing the recovery demand state with the PID feed water output state to generate a protection decision state and executing a protection action. The present application breaks the decision layer of PID regulation and electrode protection, effectively distinguishes short-time disturbance and continuous water loss working conditions, reduces false shutdown, and improves the continuity and safety of boiler operation.

Description

Technical Field

[0001] This invention belongs to the field of industrial automation process control safety technology, and particularly relates to a boiler feedwater safety protection method and system based on PID and electrode water level dual-mode control. Background Technology

[0002] As a core piece of equipment in industrial production, centralized heating, heat supply, and comprehensive energy utilization systems, the operational safety of boilers directly affects production continuity, equipment lifespan, and personnel safety. Among these safety parameters, the boiler drum water level is one of the most critical during boiler operation. Excessively high water levels can lead to decreased steam quality, steam-water bubbling, and malfunctions in downstream steam-using equipment. Conversely, excessively low water levels can cause dry burning of heating surfaces, tube rupture, and severe equipment damage. Therefore, on-site engineering projects typically employ a control method combining automatic feedwater regulation and water level safety protection. Existing boiler feedwater systems generally maintain the boiler drum water level within a set range during normal operation by adjusting the feedwater pump frequency or the opening of the feedwater regulating valve using a PID controller. Simultaneously, alarm or interlock protection is established through high-level, normal-level, low-level, and extreme-level electrodes. When the electrodes detect that the water level has reached the corresponding position, the control system executes actions such as alarm activation, combustion restriction, or boiler shutdown. This type of dual-mode structure, combining continuous PID control with discrete electrode protection, boasts advantages such as mature architecture, controllable cost, and ease of implementation in PLCs or DCS systems. It has been widely applied in gas-fired boilers, biomass boilers, industrial steam boilers, heating station boilers, and energy management systems. However, under conditions of frequent steam load fluctuations, short-term feedwater pump disturbances, fuel calorific value fluctuations, or sudden changes in steam consumption on the heating side, abnormal boiler water levels are often not simple instantaneous exceedances but rather exhibit a distinct formation process. For example, a sudden increase in steam load may result in a short-term false low water level; a short-term drop in feedwater pressure may cause a brief activation of the low water level electrode; and continuous insufficient feedwater may lead to a gradual decline in water level and a prolonged low water level. While all these conditions may ultimately manifest as low water level electrode activation, their risk attributes differ significantly. The former may recover quickly through normal PID water replenishment, while the latter may have exceeded the recoverable range of the feedwater system. Existing electrode protection typically uses only the on / off state at a specific moment, making it difficult to express the relationship between electrode triggering sequence, triggering interval, state duration, and recovery events. Existing PID control primarily focuses on water level deviation and control output, making it difficult to unify the current feedwater output capacity with the electrode protection triggering process for safety judgment. Therefore, in the existing dual-mode control system, a decision gap still exists between the PID control logic and the electrode protection logic, easily leading to premature shutdown of recoverable anomalies and delayed protection actions for continuously worsening anomalies. This is especially problematic in thermal production, energy performance contracting, and continuous boiler operation and maintenance scenarios, where accidental shutdowns affect heating stability, and delayed shutdowns increase equipment safety risks. Therefore, it is necessary to establish a safety protection mechanism based on existing PID feedwater control and electrode water level protection that can identify anomaly evolution using electrode changes, further transform this anomaly evolution into recovery requirements, and then match it with the PID feedwater output state. This would allow boiler feedwater protection actions to maintain the feasibility of the original control system while more accurately distinguishing between short-term recoverable anomalies and persistent unrecoverable anomalies. Summary of the Invention

[0003] This invention discloses a boiler feedwater safety protection method and system based on dual-mode control of PID and electrode water level, in order to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, the first aspect of the present invention provides a boiler feedwater safety protection method based on dual-mode control of PID and electrode water level, comprising:

[0005] Acquire the state changes of high-water-level electrode, normal-water-level electrode and low-water-level electrode, record each state change as a water level event, the water level event includes electrode number, trigger time and state change direction, and arrange the water level events in chronological order to form a water level event sequence;

[0006] A continuous water level event segment is read from the water level event sequence as an observation segment, and an abnormal evolution state is generated based on the electrode number, trigger time and state change direction of each water level event in the observation segment.

[0007] A recovery requirement state is generated based on the abnormal evolution state;

[0008] The recovery demand state is compared with the PID water supply output state to generate a protection decision state, and safety protection actions are executed according to the protection decision state.

[0009] Furthermore, the step of generating an abnormal evolution state based on the electrode number, trigger time, and state change direction of each water level event within the observation segment includes:

[0010] The duration coefficient of each water level event within the observation section is calculated based on the confirmation period;

[0011] The location risk coefficient is obtained by looking up the table based on the electrode number for each water level event;

[0012] The directional coefficient is determined based on the direction of the state change of each water level event, with positive values ​​for water loss events and negative values ​​for recovery events.

[0013] The anomaly evolution state is generated by weighting and combining the duration coefficient, location risk coefficient, and direction coefficient of each water level event within the observation segment.

[0014] Further, the calculation of the duration coefficient of each water level event within the observation period based on the confirmation cycle includes:

[0015] When the triggering time of the first water level event is earlier than the triggering time of the second water level event, the triggering time of the second water level event is taken as the end point of the first water level event, wherein the second water level event is the next water level event immediately following the first water level event within the observation segment;

[0016] When the first water level event is the last water level event within the observation segment, the end time of the observation segment shall be taken as the end point of the first water level event.

[0017] The duration coefficient of the first water level event is obtained by dividing the difference between the duration endpoint and the triggering time by the confirmation period and truncating the result to a preset range.

[0018] Furthermore, the value of the location risk coefficient corresponds to the electrode installation position. The location risk coefficient of the low water level electrode is greater than that of the normal water level electrode, and the location risk coefficient of the normal water level electrode is greater than that of the high water level electrode.

[0019] Further, generating the recovery requirement state based on the abnormal evolution state includes:

[0020] Calculate the difference between the abnormal evolution state of the current observation segment and the abnormal evolution state of the previous observation segment;

[0021] When the difference is positive, the difference is taken as the abnormal growth factor; when the difference is zero or negative, the abnormal growth factor is set to zero.

[0022] The abnormal evolution state is added to the result of multiplying the abnormal growth factor by the growth correction coefficient to generate the recovery demand state.

[0023] Further, the step of comparing the recovery demand state with the PID feedwater output state to generate a protection decision state includes:

[0024] Subtract the recovery demand state from the PID water supply output state to obtain the recovery margin state;

[0025] The protection decision state is generated by averaging the recovery margin state of the current observation segment with the recovery margin state of the previous observation segment.

[0026] Furthermore, the method for obtaining the PID water supply output status includes:

[0027] Read the water pump frequency command and the water regulating valve opening command to form a command ratio value;

[0028] The inverter's operating frequency and valve position execution signal are read back to form the execution ratio value;

[0029] When both the instruction ratio value and the execution ratio value are obtained simultaneously, the lower of the two values ​​is taken as the PID water supply output state.

[0030] Furthermore, the step of performing security protection actions based on the protection decision state includes:

[0031] When the protection decision state remains positive or exceeds the safety margin threshold, the PID automatic control mode is maintained for water replenishment.

[0032] When the protection decision state drops to a preset warning threshold, an alarm is triggered;

[0033] When the protection decision state is continuously below the shutdown threshold and remains below it for a preset time, combustion restriction and shutdown interlock are executed sequentially.

[0034] Furthermore, recording each state change as a water level event includes:

[0035] When the direction of state change of the same electrode remains consistent within the confirmation period, the state change is written into the water level event sequence;

[0036] When the same electrode is repeatedly switched on and off within the confirmation period, it is recorded as an abnormal electrode signal and an alarm or manual confirmation process is initiated.

[0037] A second aspect of the present invention provides a boiler feedwater safety protection system based on PID and electrode water level dual-mode control, comprising:

[0038] The water level event sequence generation module is configured to acquire the state changes of high water level electrode, normal water level electrode and low water level electrode, record each state change as a water level event, the water level event includes electrode number, trigger time and state change direction, and arrange the water level events in chronological order to form a water level event sequence.

[0039] An abnormal evolution state generation module is configured to read a continuous water level event segment from the water level event sequence as an observation segment, and generate an abnormal evolution state based on the electrode number, trigger time, and state change direction of each water level event within the observation segment.

[0040] The recovery requirement state generation module is configured to generate a recovery requirement state based on the abnormal evolution state.

[0041] The safety protection execution module is configured to compare the recovery demand state with the PID water supply output state to generate a protection decision state, and execute safety protection actions according to the protection decision state.

[0042] The beneficial technical effects of the present invention are at least as follows:

[0043] To address the aforementioned issues, this invention provides a boiler feedwater safety protection method and system based on dual-mode control of PID and electrode water level. First, electrode state changes are recorded as a sequence of water level events including electrode number, trigger time, and direction of change, enabling the electrode signals to reflect the formation process of water level anomalies. Second, anomaly evolution states are generated by combining event duration, electrode location risk, and state change direction, quantifying the direction and extent of anomaly development and effectively distinguishing between short-term false water levels, short-term feedwater disturbances, and continuous water loss conditions. Based on this, an anomaly growth factor is introduced to generate a recovery demand state, transforming the anomalous worsening trend into a quantitative water replenishment recovery demand. Finally, the recovery demand state is quantitatively matched with the effective output state of the PID feedwater control to execute protective actions. This method, while maintaining the existing hardware system, significantly reduces unnecessary boiler shutdowns caused by transient anomalies, improves heating stability, and promptly executes safety interlocks when the recovery demand continuously exceeds the feedwater capacity, greatly improving boiler operational continuity and the reliability of low water level protection. Attached Figure Description

[0044] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0045] Figure 1 This is an overall flowchart of a boiler feedwater safety protection method based on dual-mode control of PID and electrode water level, which is at least one embodiment of the present invention.

[0046] Figure 2 This is a schematic diagram illustrating the changing trends of various state values ​​under continuous water loss and deterioration conditions according to at least one embodiment of the present invention.

[0047] Figure 3 This is a structural block diagram of a boiler feedwater safety protection system based on dual-mode control of PID and electrode water level, according to at least one embodiment of the present invention. Detailed Implementation

[0048] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0049] In industrial production, district heating, and comprehensive energy utilization, the safe control of boiler drum water level is a critical task. Excessive water level can lead to decreased steam quality and steam-water bubbling, while insufficient water level can cause serious accidents such as dry burning of heating surfaces and tube rupture.

[0050] Existing boiler feedwater systems generally adopt a dual-mode structure that combines PID continuous regulation and electrode discrete protection. However, there is a decision gap between the PID control logic and the electrode protection logic, which can easily lead to premature shutdown of recoverable anomalies and delayed protection actions due to continuous deterioration.

[0051] To address at least one or more of the aforementioned problems, at least one embodiment of this disclosure designs a boiler feedwater safety protection method and system based on dual-mode control of PID and electrode water level.

[0052] Figure 1 An overall flowchart of a boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to at least one embodiment of the present disclosure is shown.

[0053] In step 101, a water level event sequence is generated.

[0054] During boiler operation, the high-level, normal-level, and low-level electrodes are connected to the PLC input module or DCS acquisition module, respectively, and the electrode detection circuit outputs a conduction or disconnection status. The control system reads the status changes of each electrode and records a water level event when any electrode changes from conduction to disconnection, or from disconnection to conduction. This processing method is an improvement on existing electrode water level protection technology. Existing technology typically only uses the electrode status at a certain moment for alarm or interlocking. This solution further records the sequential relationship of electrode status changes, enabling the electrode signals to reflect the formation process of water level anomalies. Each water level event is represented mathematically as an event sequence as follows:

[0055] ;

[0056] in, Indicates the first Record of each water level event; The electrode number indicating the state change is obtained from the corresponding PLC input point, such as high water level electrode, normal water level electrode, or low water level electrode. This indicates the moment when the electrode state change is acquired by the PLC or DCS, and is recorded by the control system clock; The direction of the state change is indicated by comparing the previous and subsequent states of the electrode detection circuit. A change from conduction to disconnection is recorded as a water loss event, and a change from disconnection to conduction is recorded as a recovery event. This formula originates from the mathematical representation of ordered event records. The improvement in this application lies in expanding the object and time in a typical event record to three items: electrode number, trigger time, and direction of state change, making it specifically applicable to describing boiler electrode water level changes. In the formula, the left side represents a single event record, and the right side represents the content of the same event record composed of the electrode number, trigger time, and direction of change; both represent the same event object.

[0057] In actual data acquisition, the PLC reads the three electrode input points in each scan cycle and compares them with the state saved in the previous scan cycle. When the current state of a certain electrode changes from the state in the previous scan cycle, the control system immediately generates a new state. For example, if the normal water level electrode was on in the previous scan cycle and turned off in the current scan cycle, the system generates an event record. Corresponding to the normal water level electrode, Get the current PLC system time. This is recorded as a water loss event. If the low-level electrode subsequently changes from conductive to disconnected, a new event record is generated. If the normal-level electrode then recovers from disconnected to conductive, a recovery event record is generated. For short fluctuations caused by boiler liquid level fluctuations, the system uses a fixed confirmation period. That is, when the direction of change of the same electrode remains consistent within the confirmation period, it is written into the water level event sequence. This confirmation period is set during the boiler control system commissioning phase. If multiple electrodes change within the same scan period, they are arranged in a fixed order according to their installation positions from high to low or from low to high. This fixed order is set during control program initialization to ensure that the order of events generated under the same operating condition is consistent. If the collected results show a state combination that clearly contradicts the installation order, such as the low-level electrode showing water while the normal-level electrode continuously shows water loss, or the same electrode repeatedly switching on and off within the confirmation period, the control system will not directly treat this combination as a normal water level evolution event. Instead, it will record it as an electrode signal abnormality and enter the alarm or manual confirmation process according to the conservative protection strategy.

[0058] In one set of boiler operation records, the normal water level electrode first changes from conductive to disconnected, followed by the low water level electrode changing from conductive to disconnected. Then, the normal water level electrode returns to conductive, and the low water level electrode also returns to conductive. The control system sequentially forms an event sequence of "normal water level electrode loss of water, low water level electrode loss of water, normal water level electrode recovery, low water level electrode recovery," which typically corresponds to the water level recovery process after a short-term disturbance. In another set of operation records, the normal water level electrode loses water first, followed by the low water level electrode, which remains in a water-loss state. The control system then forms an event sequence of "normal water level electrode loss of water, low water level electrode loss of water, low water level maintained," which corresponds to a continuous decline. Both scenarios trigger the low water level electrode, but the event sequences differ. Subsequent steps can use this difference to determine whether the anomaly is a short-term fluctuation or a continuous deterioration. This step ultimately outputs the water level event sequence. It consists of multiple items arranged in chronological order. The composition retains the complete electrode number, trigger time, and direction of change for use in the next step to generate abnormal evolution states.

[0059] In step 102, an abnormal evolution state is generated.

[0060] Step 102: The water level event sequence output from the previous step As input. Water level event sequence. Records of multiple water level events arranged in chronological order Composition, each Includes electrode number Triggering time and direction of state change The control system reads a continuous water level event record prior to the current moment as the observation segment, and uses the electrode number, trigger time, and state change direction already written in step 101 to generate an abnormal evolution state. In boiler feedwater protection scenarios, the activation of the low-water-level electrode only indicates that the water level has reached the corresponding position, but it cannot determine whether the anomaly is a short-term disturbance, a fluctuation in the drum water level, or a continuous loss of water; while the water level event sequence... The triggering sequence, adjacent triggering intervals, and recovery events included in the data can reflect the formation process of water level anomalies. Therefore, this step combines the event duration, electrode location risk, and direction of state change into a propagable anomaly evolution state, enabling subsequent steps to determine recovery requirements based on this state.

[0061] For water level events within the observation section, the control system calculates the duration coefficient based on the actual duration recorded within the observation section. Suppose the current observation segment contains data arranged in chronological order. Each water level event record is as follows: to The end time of the observation segment is recorded as For the first An event, when Less than When the duration of the event ends, the trigger time of the next event is taken as the end point of the event. ;when equal In this case, the duration of the event is taken as the end of the observation period. Therefore, each event can participate in the calculation of the abnormal evolution state, especially the low water level persistence event or recovery event at the end of the observation period, which can also be retained in the calculation results. (Persistence coefficient) Generate using the following formula:

[0062] ;

[0063] in, Indicates the first The duration coefficient of a water level event within the current observation period; Indicates the first Record of water level events The trigger time in the figure comes from the system time recorded by the PLC or DCS in step 101; Indicates the first The end point of a water level event, when Less than Time to take ,when equal Take the end time of the observation segment ; This indicates the confirmation period set during the commissioning phase of the boiler control system, used to characterize the reference duration for which changes in the primary electrode state are considered to have sustained significance. It should be greater than zero. Since step 101 has already generated the event sequence in chronological order, under normal circumstances... The time difference is non-negative; if the time difference is less than zero due to clock rollback, communication delay, or log entry, the system will record the event as a time anomaly and allocate the corresponding time difference. Zero values ​​are used, and these do not participate in the effective duration weight calculation. This formula originates from a combination of proportional normalization and truncation functions in mathematics. Its original form compares a duration to a reference time and limits the result to a fixed range. This application uses this form between boiler electrode events, converting the event's duration within the observation period into a duration coefficient, thus creating numerical differences between short triggering, rapid recovery, and sustained duration. Both terms used for division in the formula are time records, obtained after proportionalization and truncation. Used as weights in state calculations.

[0064] Duration coefficient After generation, the control system uses the electrode number from the water level event record. The location risk coefficient can be obtained by looking up the table. And according to the direction of state change Obtain the direction coefficient Location risk factor The values ​​are written during control program initialization, corresponding to the electrode installation position and the importance of low water level protection. For example, the low water level electrode is configured with a higher value, the normal water level electrode with a middle value, and the high water level electrode with a lower value. These values ​​use a proportionalized level. During engineering implementation, the low water level electrode can be configured as follows: Normal water level electrode configuration is The high water level electrode is configured as follows Directional coefficient The direction of the state change is directly determined: a water loss event is represented by a positive value, and a recovery event by a negative value. Subsequently, the control system will observe the events within the observation segment. , and Combining to generate anomalous evolutionary states :

[0065] ;

[0066] in, This indicates the current state of the anomaly evolution generated in the observation segment, used to characterize the development direction and degree of water level anomalies within that observation segment; Indicates the first The location risk coefficient corresponding to each water level event is determined by the electrode number in the event record. Obtained from the preset electrode risk table; Indicates the first The direction coefficient corresponding to each water level event is determined by the direction of state change in the event record. Sure; Indicates the first The duration coefficient corresponding to each water level event is calculated using the previous formula; This indicates the number of water level events recorded within the current observation segment. If there are no valid water level events within the observation segment, or if all valid events... If all values ​​are zero, the control system will not perform the weighted average division, but will instead... Maintain the abnormal evolution state of the previous observation segment and output a "no valid event" flag; if there is no previous observation segment, then... Initialize to zero. This formula originates from the weighted average expression in mathematics, where the original form is a weighted summation of multiple observations based on weights. This application modifies this expression for boiler water level protection: the observation is designed as a combination of electrode position risk and event direction, and the weights are designed as event duration coefficients, so that events of low water level loss and continuous maintenance... It has a strong positive impact, and the recovery event has a significant positive effect. A reverse correction is generated due to the short-lived jitter event. Smaller and weaker in impact. The previous formula yielded... As weights in this formula, they form a progressive relationship between the two equations, moving from the quantification of event persistence to the generation of abnormal evolution states. The numerator of this formula... , and All values ​​are proportionalized or graded, and the denominator is the sum of the continuity coefficients. This is a state value, which can be directly used as input for the next step to generate the state required for recovery.

[0067] In a set of boiler operation records, the control program will confirm the cycle. The configuration is set to ten seconds, and the location risk factor of the low water level electrode is... Configured as Risk factor of the location of the normal water level electrode Configured as The risk factor of the location of the high water level electrode Configured as Directional coefficient of water loss event Pick , restore event direction coefficient Pick If the water level event sequence The observation segments are, in sequence, the loss of water at the normal water level electrode, the loss of water at the low water level electrode, the recovery of the normal water level electrode, and the recovery of the low water level electrode. The intervals between adjacent triggers are two seconds, three seconds, and two seconds, respectively. The end time of the observation segment is three seconds after the last recovery event. Therefore, the duration coefficients corresponding to the four events are respectively... , , and After substituting the values ​​into the calculation, the normal water level electrode water loss event is formed. The positive impact of low water level electrode water loss event The positive impact of the normal water level electrode recovery event. The reverse effect, low water level electrode recovery event formation The reverse effect, ultimately obtained A value close to zero corresponds to an abnormal evolutionary state after a short-term fluctuation. If another set of operating records shows sequential loss of water at the normal water level electrode and then at the low water level electrode, and the low water level loss event continues for more than the confirmation period, then both the normal water level event and the low water level event have a positive impact. The low water level loss event, due to its higher location risk coefficient and higher duration coefficient, will... A significant increase corresponds to a continuously deteriorating abnormal evolutionary state. The above calculation process reflects common differences in boiler field operations: both short-term false water levels and persistent water shortages can trigger the low water level electrode, but the former is usually accompanied by a faster recovery event, while the latter is usually characterized by a persistent low water level loss. Therefore, the two differ in... Different results were obtained in the process.

[0068] This step ultimately outputs the abnormal evolution state. This state is determined by a sequence of water level events. Electrode numbering Triggering time and direction of state change The derivation shows that it fully inherits the output of step 101 and converts the discrete electrode triggering process into state values ​​that can describe the direction and extent of water level anomalies. The next step is... This serves as input to further determine the recovery requirements needed to bring the anomaly back to a safe operating range.

[0069] In step 103, a recovery requirement state is generated.

[0070] Step 103: The anomalous evolution state generated in the previous step As input, it is transformed into a quantitative state of recovery demand. This indicates the amount of water replenishment required to pull the current water level back to a safe operating range. The control system reads the abnormal evolution status of the currently observed segment. and the anomalous evolutionary state preserved in the previous observation segment. And calculate the abnormal growth factor. The abnormal growth factor is used to represent the positive increase in abnormal evolutionary states between adjacent observation segments:

[0071] ;

[0072] in, Indicates abnormal growth factor; This represents the abnormal evolution state value of the current observation segment; This represents the abnormal evolution state value of the previous observation segment. This formula originates from the discrete sequence difference analysis method and is used to quantify the state increment between adjacent observation segments. This application uses it for the boiler water level anomaly evolution sequence, retaining only the change in the direction of anomaly enhancement, so that the continuously deteriorating water level anomaly can form an additional increment in the recovery demand. When the recovery demand state is generated for the first time, the control system takes the abnormal evolution state of the previous observation segment as the abnormal evolution state of the current observation segment, so that the initially calculated... It is zero; in subsequent calculations, Take the previously saved observation segment .

[0073] Combined with abnormal growth factors and the current abnormal evolution state The control system generates the recovery requirement state. :

[0074] ;

[0075] in, This indicates the state of demand for restoration; the higher the value, the greater the intensity of water replenishment required to address the current abnormal water level. This represents the abnormal evolution state value of the current observation segment; It is an abnormal growth factor; The growth correction factor, set based on boiler operating experience, is used to amplify the recovery requirements of continuously deteriorating anomalies. For example, it can be taken as [value missing] in high-load boiler operating environments. This formula originates from the feedforward compensation concept in control theory, the original idea being to proactively increase the regulatory effect when state changes intensify. This application uses it to generate recovery demand, mapping both the intensity of the anomaly itself and the trend of its continued intensification to a recovery demand state. In the formula… Used to indicate the basic need for water replenishment and restoration in response to the current anomaly. This is used to represent the increased water demand when the abnormality continues to intensify. Both values ​​are state values, and the calculation result is also a state value. When the calculation result exceeds one, proceed to step 104. Before comparison, a truncation is performed, and the value before truncation is retained as the anomaly strength record, so that... It is on the same scale as the subsequent PID water supply output status.

[0076] In practice, the control system generates data continuously according to the order of the observation segments. For example, in a continuous observation process, the anomalous evolutionary state of the first observation segment. for Because of the initial calculation Remove zeros and restore the required state. for The abnormal evolutionary state of the second observation segment is as follows: The abnormal evolutionary state in the previous observation period was: ,but When the growth correction coefficient Pick At that time, restore the demand state. The abnormal evolutionary state of the third observation segment is as follows: The abnormal evolutionary state in the previous observation period was: ,but To restore demand status This numerical change indicates that when the water level anomaly continues to intensify, the recovery demand increases in tandem with the degree and growth trend of the anomaly; when the anomaly evolution state declines or enters the recovery direction, the anomaly growth factor becomes zero, and the recovery demand decreases with the current degree of anomaly.

[0077] The final output of this step is to restore the required state. This state is the anomalous evolution state output in step 102. and abnormal growth factors between adjacent observation segments The generation process not only preserves the abnormal evolution information formed by the water level event sequence, but also converts the trend of continuous enhancement of the abnormality into a water replenishment recovery demand, which is then used by the next step to match the PID water supply output status and execute safety protection actions.

[0078] In step 104, a safety protection action is performed.

[0079] Step 104: Recovery Request Status Generated in the Previous Step As input, and combined with the current PID feedwater output status Perform safety protection actions. Restore the required state. This reflects the intensity of the current water level anomaly and the quantitative level required for water supply restoration. This indicates that the PID water supply system is currently in an effective output state that can be used to restore the water level. The PLC or DCS reads the feedwater pump frequency command, the inverter operating frequency readback, the feedwater regulating valve opening command, and the valve position execution signal to form a proportional value. During project implementation, when both the command proportional value and the execution proportional value are obtained simultaneously, the lower of the two is taken as the current effective output state, ensuring that this state reflects the actual recovery capability of the feedwater actuator. To quantitatively match the recovery requirement with the actual control capability, the control system first calculates the recovery margin state. :

[0080] ;

[0081] in, This indicates the recovery margin, reflecting the current effective output of the PID feedwater relative to the abnormal recovery requirements. This indicates the current PID water supply output status, which is obtained by proportionalizing the relevant signals of the water supply pump frequency and the water supply valve opening. This indicates the recovery request status generated in step 103. and Both use a scale of zero to one, so they can be directly subtracted; if the feedwater pump frequency readback, valve position execution signal, or communication status is abnormal, the system will... The margin is determined based on the lowest achievable effective execution ratio; if an effective execution ratio cannot be achieved, it is set to zero, triggering an abnormal alarm in the actuator. This formula originates from the control margin calculation method in control engineering, and its original form is used to compare the difference between control capability and control requirements. This application applies it to the boiler feedwater safety protection scenario, quantifying the abnormal evolution and recovery requirements and comparing them with the PID feedwater output state to form a margin value that can be used to execute protective actions. Positive value This indicates that the PID water supply output is higher than the recovery requirement. A zero value indicates that the capacity is close to the demand, while a negative value indicates that the recovery requirement exceeds the current effective output state.

[0082] The control system then generates a protection decision state. This reflects the basis for the execution of protective actions within the current observation segment:

[0083] ;

[0084] in, Indicates the status of the protection decision; This represents the recovery margin status of the currently observed segment; This represents the recovery margin state of the previous observation segment. The formula is derived from the moving average method, used to smooth continuous observations. By averaging the current recovery margin state with the previous observation segment, the protection decision state reflects the continuity of recovery margin changes, allowing protection actions to consider both the current and adjacent states. When generating the protection decision state for the first time, the control system will... Take as the current recovery margin state In the subsequent observation segment, Take the recovery margin state that has been saved in the previous observation segment.

[0085] During implementation, the control system continuously calculates for each observation segment. and and according to The numerical value selects the protection action level. When When the value remains positive or exceeds the set safety margin, the system maintains the PID automatic control mode, while allowing the water pump frequency and valve opening to continue adjusting in the recovery direction to achieve water replenishment; when When the value approaches zero or drops to a preset warning threshold, an audible and visual alarm is triggered, and the operational event is recorded to alert the operator of any abnormal development trend; when When the load remains below the shutdown threshold for a certain period of time, the system sequentially sends limiting commands to the combustion control system to reduce the evaporation load and executes combustion cut-off and shutdown interlocking to ensure safe boiler shutdown. In the embodiment, a certain observation period... In order , , PID water supply output status In order , , ,but In order , , First observation segment Pick Second and third observation segments They are respectively and The system maintains automatic water replenishment. In another set of operation records, In order , , , In order , , ,but In order , , First observation segment Pick Second and third observation segments They are respectively and The control system identifies that the recovery margin is continuously insufficient, triggers an early warning, and ultimately executes a shutdown interlock.

[0086] This step ultimately outputs the protection decision status. And corresponding safety protection actions, including PID water replenishment adjustment, alarm, combustion limitation, and shutdown interlock. This output follows the recovery requirement from step 103. Combined with PID water supply output status This enables the transformation from quantifying recovery needs to specific security protection operations.

[0087] Figure 2 A schematic diagram showing the changing trends of various state values ​​under a continuous dehydration and deterioration condition according to at least one embodiment of the present disclosure is illustrated.

[0088] like Figure 2 As shown, the horizontal axis represents the observation segment number, and the vertical axis represents the state value. In one embodiment, the boiler control system will increase the correction factor. Set as The abnormal evolution state is calculated on a unit of continuous observation segments. Abnormal growth factors , restore demand status PID valid output status , restore margin state and protection decision status The table below presents the calculation results for two types of operating conditions. "Short-term disturbance recovery" corresponds to the rapid recovery process after a short-term loss of water in the electrode, while "continuous water loss and deterioration" corresponds to the process where the low water level event continues to intensify and the PID feedwater output gradually fails to cover the recovery requirements. All state values ​​in the table are on a scale of zero to one. and Negative values ​​are allowed, indicating that the recovery capacity is lower than the recovery requirement.

[0089]

[0090] As can be seen from the table above, under the short-term disturbance recovery condition, from Descending to , Demand remains at zero until it returns to normal. Consequently, it decreases, and Always higher ,therefore and Maintaining a positive value, the control system continues PID automatic water replenishment without triggering the shutdown interlock. Under conditions of continuous water loss and deterioration, from Rise to Positive signals are continuously generated between adjacent observation segments. ,make from Rise to When the 4th observation segment begins Exceed hour, and If the value turns negative, the system first executes an alarm and combustion restriction. If the recovery margin remains insufficient in the fifth observation period, a shutdown interlock is executed. This embodiment illustrates that this method can transform the evolution of electrode water level events into recovery requirements and match them with the effective output state of the PID controller, thereby distinguishing between short-term recoverable disturbances and continuous unrecoverable water loss.

[0091] Figure 3 A structural block diagram of a boiler feedwater safety protection system based on PID and electrode water level dual-mode control according to at least one embodiment of the present disclosure is shown.

[0092] The water level event sequence generation module is configured to acquire the state changes of high water level electrode, normal water level electrode and low water level electrode, record each state change as a water level event, the water level event includes electrode number, trigger time and state change direction, and arrange the water level events in chronological order to form a water level event sequence.

[0093] An abnormal evolution state generation module is configured to read a continuous water level event segment from the water level event sequence as an observation segment, and generate an abnormal evolution state based on the electrode number, trigger time, and state change direction of each water level event within the observation segment.

[0094] The recovery requirement state generation module is configured to generate a recovery requirement state based on the abnormal evolution state.

[0095] The safety protection execution module is configured to compare the recovery demand state with the PID water supply output state to generate a protection decision state, and execute safety protection actions according to the protection decision state.

[0096] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A boiler feedwater safety protection method based on PID and electrode water level dual-mode control, characterized in that, include: Acquire the state changes of high-water-level electrode, normal-water-level electrode and low-water-level electrode, record each state change as a water level event, the water level event includes electrode number, trigger time and state change direction, and arrange the water level events in chronological order to form a water level event sequence; A continuous water level event segment is read from the water level event sequence as an observation segment, and an abnormal evolution state is generated based on the electrode number, trigger time and state change direction of each water level event in the observation segment. A recovery requirement state is generated based on the abnormal evolution state; The recovery demand state is compared with the PID water supply output state to generate a protection decision state, and safety protection actions are executed according to the protection decision state.

2. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 1, characterized in that, The process of generating an abnormal evolution state based on the electrode number, trigger time, and state change direction of each water level event within the observation segment includes: The duration coefficient of each water level event within the observation section is calculated based on the confirmation period; The location risk coefficient is obtained by looking up the table based on the electrode number for each water level event; The directional coefficient is determined based on the direction of the state change of each water level event, with positive values ​​for water loss events and negative values ​​for recovery events. The anomaly evolution state is generated by weighting and combining the duration coefficient, location risk coefficient, and direction coefficient of each water level event within the observation segment.

3. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 2, characterized in that, The calculation of the duration coefficient of each water level event within the observation period based on the confirmation cycle includes: When the triggering time of the first water level event is earlier than the triggering time of the second water level event, the triggering time of the second water level event is taken as the end point of the first water level event, wherein the second water level event is the next water level event immediately following the first water level event within the observation segment; When the first water level event is the last water level event within the observation segment, the end time of the observation segment shall be taken as the end point of the first water level event. The duration coefficient of the first water level event is obtained by dividing the difference between the duration endpoint and the triggering time by the confirmation period and truncating the result to a preset range.

4. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 2, characterized in that, The location risk coefficient corresponds to the electrode installation location. The location risk coefficient of the low water level electrode is greater than that of the normal water level electrode, and the location risk coefficient of the normal water level electrode is greater than that of the high water level electrode.

5. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 1, characterized in that, The step of generating a recovery requirement state based on the abnormal evolution state includes: Calculate the difference between the abnormal evolution state of the current observation segment and the abnormal evolution state of the previous observation segment; When the difference is positive, the difference is taken as the abnormal growth factor; when the difference is zero or negative, the abnormal growth factor is set to zero. The abnormal evolution state is added to the result of multiplying the abnormal growth factor by the growth correction coefficient to generate the recovery demand state.

6. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 1, characterized in that, The step of comparing the recovery demand state with the PID feedwater output state to generate a protection decision state includes: Subtract the recovery demand state from the PID water supply output state to obtain the recovery margin state; The protection decision state is generated by averaging the recovery margin state of the current observation segment with the recovery margin state of the previous observation segment.

7. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 6, characterized in that, The methods for obtaining the PID water supply output status include: Read the water pump frequency command and the water regulating valve opening command to form a command ratio value; The inverter's operating frequency and valve position execution signal are read back to form the execution ratio value; When both the instruction ratio value and the execution ratio value are obtained simultaneously, the lower of the two values ​​is taken as the PID water supply output state.

8. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 6, characterized in that, The step of performing security protection actions based on the protection decision state includes: When the protection decision state remains positive or exceeds the safety margin threshold, the PID automatic control mode is maintained for water replenishment. When the protection decision state drops to a preset warning threshold, an alarm is triggered; When the protection decision state is continuously below the shutdown threshold and remains below it for a preset time, combustion restriction and shutdown interlock are executed sequentially.

9. The boiler feedwater safety protection method based on PID and electrode water level dual-mode control according to claim 1, characterized in that, The process of recording each state change as a water level event includes: When the direction of state change of the same electrode remains consistent within the confirmation period, the state change is written into the water level event sequence; When the same electrode is repeatedly switched on and off within the confirmation period, it is recorded as an abnormal electrode signal and an alarm or manual confirmation process is initiated.

10. A boiler feedwater safety protection system based on PID and electrode water level dual-mode control, characterized in that, include: The water level event sequence generation module is configured to acquire the state changes of high water level electrode, normal water level electrode and low water level electrode, record each state change as a water level event, the water level event includes electrode number, trigger time and state change direction, and arrange the water level events in chronological order to form a water level event sequence. An abnormal evolution state generation module is configured to read a continuous water level event segment from the water level event sequence as an observation segment, and generate an abnormal evolution state based on the electrode number, trigger time, and state change direction of each water level event within the observation segment. The recovery requirement state generation module is configured to generate a recovery requirement state based on the abnormal evolution state. The safety protection execution module is configured to compare the recovery demand state with the PID water supply output state to generate a protection decision state, and execute safety protection actions according to the protection decision state.

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