AGC variable load control method for thermal power unit

Abstract

The present application relates to the field of power generation control technology of thermal power generating units, and particularly relates to a kind of AGC variable load control method of thermal power generating unit, by predicting future wall temperature and generating continuous flexible correction coefficient according to its deviation from safety limit, dynamically adjusting variable load rate, changing the traditional over-temperature limit after hard removal mode into early active intervention based on prediction trend, reducing speed in advance before wall temperature approaches limit, so as to effectively inhibit wall temperature peak, avoid lagging over-temperature pipe explosion; at the same time, the continuous change of correction coefficient eliminates load step, makes main steam pressure and steam temperature transition smooth, improves AGC assessment index, reduces unit oscillation and manual intervention. In this way, full-speed response when safety margin is sufficient, flexible speed reduction when margin is tight, achieving the best balance of safety and speed, and only need to add logic module in DCS, engineering is simple, and economic benefit is remarkable.

Description

Technical Field

[0001] This invention relates to the field of thermal power unit power generation control technology, and in particular to an AGC variable load control method for thermal power units. Background Technology

[0002] As the mainstay of power grid peak shaving and frequency regulation, the performance of automatic generation control (AGC) of thermal power units directly affects the safe and stable operation of the power grid. In AGC mode, units need to respond frequently and quickly to grid load commands. The typical way existing coordinated control systems (CCS) handle AGC commands is to generate a smooth target trajectory from the target load command issued by the grid through a ramp limiter, and then adjust the load at a fixed rate or segmented fixed rates. Simultaneously, for the problem of wall temperature overheating of heated surfaces (such as screen-type superheaters and high-temperature reheaters), protection logic based on real-time temperature thresholds is commonly used; that is, when the measured wall temperature exceeds the alarm value, an alarm is triggered or the load increase command is hard-locked.

[0003] However, the aforementioned existing technologies have the following drawbacks in practical applications: First, due to the significant thermal inertia and pure hysteresis between the boiler combustion system and the heating surface, when the wall temperature alarm is triggered, even if fuel supply is immediately stopped, the tube wall temperature will continue to rise due to thermal inertia, leading to the failure of "post-event control" and easily causing tube rupture accidents. Second, hard interlocking logic can cause a sudden change in load command, resulting in significant fluctuations in key parameters such as main steam pressure and temperature, worsening AGC performance indicators (such as Kp), and even inducing unit oscillations. Third, the fixed variable load rate cannot be dynamically adjusted according to the real-time approach speed of the wall temperature. When the safety margin is sufficient, the response is too slow, while when the margin is insufficient, the response is too fast, leading to overheating, and the safety margin cannot be fully utilized. Fourth, the protection logics for various safety constraints such as wall temperature, steam temperature, and water level are independent, lacking a unified "safety gating" and rate coordination mechanism, which easily leads to control conflicts. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a method for AGC variable load control of thermal power units.

[0005] In a first aspect, embodiments of the present invention provide an AGC (Automatic Guided Control) method for variable load control of thermal power units, the method comprising: Real-time acquisition of thermal power unit operating data, including at least heating surface wall temperature, fuel quantity, and actual load; Input the running data into the preset wall temperature thermal inertia prediction model to calculate the predicted wall temperature value; A flexible correction coefficient is generated based on the prediction margin between the predicted wall temperature and the preset safety limit. The operating status of AGC load commands is determined based on the flexibility correction coefficient; the operating status includes normal status, speed limit status, freeze status, and rollback status. If the load change rate is in normal or speed-limited state, the required load change rate of the power grid is multiplied by the flexibility correction coefficient to obtain the actual load change rate. Based on the actual load change rate, the target load command is speed-limited to generate an AGC output command. If the system is frozen, the AGC output command will remain at its current value. If in rollback mode, the AGC output command will be rolled back in the direction of load reduction at a preset rollback rate.

[0006] In conjunction with the first aspect, the steps of inputting operational data into a preset wall temperature thermal inertia prediction model and calculating the predicted wall temperature value include: Calculate the product of the current wall temperature change rate and the preset prediction step size to obtain the extrapolated increment of the wall temperature under the current trend; The extrapolated increment is added to the current wall temperature to obtain the estimated wall temperature value under the continued trend. Based on the fuel change rate sequence within a set historical time period, calculate the contribution value of the hysteresis effect of fuel change rate on wall temperature; The predicted wall temperature is obtained by adding the current wall temperature, the extrapolated increment, and the lag effect contribution of the fuel change rate.

[0007] In conjunction with the first aspect, the step of calculating the contribution of the hysteretic effect of fuel change rate on wall temperature based on the fuel change rate sequence over a set historical period includes: For each moment in the fuel change rate sequence, a weighting coefficient is assigned to the fuel change rate that decays exponentially with time backtracking. The decay rate of the weighting coefficient is determined by the metal thermal inertia time constant. The fuel change rate at each time step is multiplied by its corresponding weighting coefficient, and then the results are accumulated and integrated within the backtracking integration window to obtain the integral result. The product of the integral result and the fuel-wall temperature sensitivity coefficient yields the contribution of the fuel change rate to the wall temperature through the thermal inertia hysteresis.

[0008] In conjunction with the first aspect, the step of generating a flexible correction coefficient based on the prediction margin between the predicted wall temperature and the preset safety limit includes: Calculate the difference between the safe limit for wall temperature and the predicted value for wall temperature, and use the difference as the prediction margin; The flexibility correction coefficient is determined based on the comparison between the prediction margin and the safety buffer threshold.

[0009] In conjunction with the first aspect, the steps for determining the flexibility correction coefficient based on the comparison between the prediction margin and the safety buffer threshold include: If the prediction margin is greater than or equal to the safety buffer threshold, the flexibility correction factor is set to 1. If the prediction margin is between 0 and the safety buffer threshold, a flexibility correction coefficient is calculated based on the prediction margin and the safety buffer threshold. If the prediction margin is less than or equal to 0, the flexibility correction factor is set to 0.

[0010] In conjunction with the first aspect, the steps for calculating the flexibility correction coefficient based on the prediction margin and safety buffer threshold include: Calculate the quotient of the prediction margin and the safety buffer threshold; Calculate the power function of the quotient to obtain the flexible correction coefficient; In a power function, the exponent is a real number greater than 0.

[0011] In conjunction with the first aspect, the target load command is rate-limited based on the actual variable load rate, generating an AGC output command, including: Input the target load command and the actual load change rate into the ramp limiter; The ramp limiter uses the actual load rate as the upper limit of the change per unit time to limit the target load command, and generates and outputs the AGC output command after the speed limit.

[0012] In conjunction with the first aspect, the operating status of the AGC load command is determined based on the flexibility correction coefficient, including: When the flexible correction coefficient is greater than or equal to the first threshold, it enters the normal state; When the flexible correction coefficient is between the second threshold and the first threshold, the speed limit state is entered. When the flexibility correction coefficient is less than or equal to the second threshold, it enters a frozen state or a rollback state.

[0013] In conjunction with the first aspect, when the flexibility correction coefficient is less than or equal to the second threshold, the system enters a frozen state or a rollback state, including: If the duration for which the flexible correction coefficient is less than or equal to the second threshold does not exceed the preset holding time, the system enters a frozen state. If the duration for which the flexible correction coefficient is less than or equal to the second threshold exceeds the preset holding time, or if the predicted wall temperature reaches or exceeds the preset wall temperature safety limit, the system enters a rollback state.

[0014] In conjunction with the first aspect, the method also includes: The prediction deviation of the wall temperature is calculated in real time. The prediction deviation is the difference between the current wall temperature and the current wall temperature value predicted at the previous prediction step. Determine if the unit is in an active period of variable load. If the absolute value of the fuel change rate is greater than the preset threshold and the sensor signal is normal, then start parameter update. The recursive least squares method is used to assign decreasing weights to historical data with an exponential forgetting factor, and the fuel-wall temperature sensitivity coefficient and metal thermal inertia time constant are updated online. The updated fuel-wall temperature sensitivity coefficient and metal thermal inertia time constant are smoothed by first-order low-pass filtering and physical boundary hard limiting is applied to keep them within a preset reasonable constant range. The predicted wall temperature is iteratively updated based on the smoothed and limited fuel-wall temperature sensitivity coefficient and the metal thermal inertia time constant.

[0015] The embodiments of this invention bring the following beneficial effects: This application provides an AGC (Automatic Generation Control) method for variable load in thermal power units. By predicting future wall temperatures and generating continuous flexible correction coefficients based on the degree of deviation from safety limits, the variable load rate is dynamically adjusted. This transforms the traditional hard shut-off method after exceeding temperature limits into proactive intervention based on predicted trends. Speed ​​is reduced in advance before the wall temperature approaches the limit, effectively suppressing peak wall temperatures and avoiding delayed overheating and pipe rupture. Simultaneously, the continuous change of the correction coefficient eliminates load abrupt changes, ensuring smooth transitions in main steam pressure and temperature, improving AGC performance indicators, and reducing unit oscillations and manual intervention. Thus, full-speed response is achieved when safety margins are sufficient, while flexible speed reduction is implemented when margins are tight, achieving an optimal balance between safety and speed. Furthermore, only a logic module needs to be added to the DCS, simplifying the engineering and resulting in significant economic benefits.

[0016] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention are realized and obtained in accordance with the structures particularly pointed out in the description, claims and drawings.

[0017] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0019] Figure 1 This invention provides an AGC (Automatic Guided Control) method for variable load control of thermal power units. Figure 2 This is a schematic diagram of the electronic device structure provided in an embodiment of the present invention.

[0020] Figure label: 130 - Processor, 131 - Memory, 132 - Bus, 133 - Communication interface. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] To facilitate understanding of this embodiment, the technical terms used in this application will be briefly introduced below.

[0023] AGC (Automatic Generation Control): Load regulation instructions issued by the power grid dispatch center to thermal power units. The units must track the target load at a specified rate to maintain the stability of the power grid frequency.

[0024] CCS (Coordination and Control System): The core control loop of the unit, responsible for coordinating the energy balance between the boiler and the turbine, executing AGC commands, and maintaining key parameters such as main steam pressure.

[0025] State machine: A logic module used to switch the execution mode of AGC instructions under different operating conditions. It includes four states: normal, speed limit, freeze, and rollback. The state switching is based on the flexibility correction coefficient and prediction margin.

[0026] main steam pressure The steam pressure at the turbine inlet reflects the energy balance between the boiler and the turbine. Deviations from the set value will limit the rate of load change to prevent pressure over-limit.

[0027] Steam temperature: including main steam temperature and reheat steam temperature. Monitor and predict its trends to prevent overheating and damage to the heating surfaces.

[0028] Steam drum water level: A critical safety parameter for steam drum boilers. In case of abnormal water level, stability is ensured through speed limiting or freeze commands.

[0029] Desuperheating water valve position: This valve opening is used to regulate the steam temperature. When the valve position approaches saturation, it indicates that the load change rate is too fast and the rate needs to be reduced in time.

[0030] After introducing the technical terms used in this application, the application scenarios and design concepts of the embodiments of this application will be briefly described below.

[0031] The existing AGC variable load uses a fixed rate, and the wall temperature protection is based on a real-time threshold. Due to the thermal inertia and hysteresis of the combustion and heating surfaces, the wall temperature continues to rise inertia when the alarm is triggered, leading to the risk of overheating afterward; hard interlocking causes command step disturbances, insufficient utilization of safety margins, and poor coordination of multiple constraints.

[0032] Based on this, this application provides an AGC variable load control method for thermal power units.

[0033] Example 1 This application provides a method for AGC (Automatic Load Control) variable load control of thermal power units, combined with... Figure 1 As shown, the method includes: S110 collects real-time operating data of thermal power units, including at least the wall temperature of the heating surface, fuel quantity, and actual load.

[0034] S120: Input the running data into the preset wall temperature thermal inertia prediction model to calculate the predicted wall temperature value.

[0035] S130 generates a flexible correction coefficient based on the prediction margin between the predicted wall temperature and the preset safety limit.

[0036] S140, determine the operating status of AGC load command based on the flexibility correction coefficient; the operating status includes normal status, speed limit status, freeze status and rollback status.

[0037] S150, if in normal or speed-limited state, multiply the load change rate required by the power grid by the flexibility correction coefficient to obtain the actual load change rate, and perform speed-limiting processing on the target load command based on the actual load change rate to generate AGC output command.

[0038] S160, if in a frozen state, keep the AGC output command at its current value.

[0039] S170, if in the rollback state, the AGC output command will be rolled back in the direction of load reduction at a preset rollback rate.

[0040] This application's embodiments predict future wall temperatures and generate continuous flexible correction coefficients based on the degree to which these temperatures deviate from safety limits. This dynamically adjusts the load rate, transforming the traditional rigid shut-off method after exceeding temperature limits into proactive intervention based on predicted trends. The rate is reduced before the wall temperature approaches the limit, effectively suppressing peak wall temperatures and preventing delayed overheating and pipe bursts. Simultaneously, the continuous change in the correction coefficient eliminates load abrupt changes, ensuring smooth transitions in main steam pressure and temperature, improving AGC performance indicators, and reducing unit oscillations and manual intervention. This method achieves a full-speed response when safety margins are sufficient and a flexible rate reduction when margins are tight, achieving an optimal balance between safety and speed. Furthermore, it only requires adding a logic module to the DCS, simplifying engineering and offering significant economic benefits.

[0041] In step S110 of this embodiment, operating parameters closely related to the unit's load change process are collected in real time at a sampling frequency no less than the system control cycle (typically 1 second or less). These operating parameters include: the wall temperature of the heated surface. T (take the maximum value) Total fuel quantity M, load , main steam pressure Steam temperature, steam drum water level, and desuperheating water valve position, etc.

[0042] To avoid the influence of single-point deviations, in this embodiment, after obtaining the wall temperature T of the heating surface corresponding to multiple measuring points of each key heating surface (such as the screen-type superheater and the high-temperature reheater), all heating surface wall temperatures are taken. T The maximum value in is used as the current wall temperature. Tact .

[0043] Total fuel quantity M It directly reflects the trend of heat changes entering the furnace.

[0044] load The actual active power of the generating unit (unit: MW) is a key parameter reflecting the current output level of the unit. Real-time load data collection is required. As the target and feedback values ​​for variable load control, the deviation between the calculated values ​​and AGC commands is used; it can also serve as one of multiple safety constraints, assisting in determining whether to limit the rate of load change when the load is too high or too low (for example, wall temperatures are more likely to exceed limits in high-load areas, so the correction factor can be appropriately tightened). Furthermore, the load... It is also used as an auxiliary judgment for online adaptive correction (such as distinguishing between steady-state and dynamic conditions) to ensure more accurate model parameter updates.

[0045] In conjunction with the first aspect, step S120 includes: S121, calculate the product of the current wall temperature change rate and the preset prediction step size to obtain the extrapolated increment of the wall temperature under the current trend.

[0046] Among them, the current wall temperature change rate The measured wall temperature value collected in step S110 is calculated in real time using numerical difference (such as backward difference), reflecting the instantaneous direction and rate of change of the pipe wall temperature within the most recent sampling period. Prediction step size. It is a time parameter pre-tuned based on the thermal inertia characteristics of the boiler's heating surface (usually 3–10 seconds, depending on the metal's heat storage capacity and heat transfer delay). This product... This represents the incremental value that the wall temperature will reach by linear extrapolation along the current trend, assuming no additional heat disturbance (i.e., the amount of fuel remains constant).

[0047] S122, the extrapolated increment is added to the current wall temperature to obtain the estimated wall temperature value under the current trend.

[0048] pass This establishes a pure trend extrapolation baseline, representing the natural wall temperature change resulting solely from heat storage release or thermal inertia if boiler combustion conditions are stable (e.g., constant fuel quantity). This baseline does not yet account for additional heat shocks caused by changes in fuel quantity, and therefore requires further correction.

[0049] S123, calculate the contribution value of the hysteresis effect of fuel change rate on wall temperature based on the fuel change rate sequence within the set historical time period.

[0050] Specifically, the fuel change rate within a past backtracking integration window (e.g., 30–60 seconds) is selected. Data, based on the metal thermal inertia time constant Perform an exponential decay weighted integral, then multiply by the fuel-wall temperature sensitivity coefficient. This yields the additional wall temperature increase on the heated surface resulting from fuel changes through the thermal inertia hysteresis process.

[0051] The formula for continuous calculation is:

[0052] In practical distributed control systems, this continuous integral is often discretized into a first-order inertial plus pure time-delay differential recursive form to reduce computational load and adapt to a fixed sampling period. This time-delay contribution characterizes the delay and cumulative effect of heat transfer from the furnace to the tube wall after a change in fuel quantity, in order to avoid ex-post control failure.

[0053] S124 adds up the current wall temperature, the extrapolated increment, and the lag effect contribution of the fuel change rate to obtain the predicted wall temperature value.

[0054] The final predicted wall temperature is calculated using the following formula:

[0055] in, This is the predicted wall temperature value.

[0056] This summation operation organically combines the current actual temperature, short-term linear extrapolation trend, and long-term fuel hysteresis effects. It captures both the direction of change in the current thermal state and considers the cumulative temperature rise effect that will appear after the historical fuel quantity disturbance is delayed by thermal inertia. The wall temperature prediction value obtained in this way can be used to calculate the safety margin in subsequent steps, thereby generating a flexible correction coefficient to achieve advance dynamic adjustment of the load rate, avoiding the drawback of traditional threshold protection alarms being uncontrollable.

[0057] In conjunction with the first aspect, step S123 includes: S1231 assigns a weighting coefficient to the fuel change rate at each moment in the fuel change rate sequence, which decays exponentially with time backtracking. The decay rate of the weighting coefficient is determined by the metal thermal inertia time constant.

[0058] The fuel change rate data within a backtracking integration window (e.g., 30-60 seconds) are arranged chronologically. Fuel change rates further back in time are assigned lower weights, while those closer to the present are assigned higher weights. The weighting coefficients vary with the backtracking time. The increase follows an exponential law Attenuation, in which This is the time constant of the metal's thermal inertia, reflecting the rate of heat storage and transfer within the pipe wall metal. A larger value indicates a lower rate of heat transfer. This indicates high thermal inertia, meaning the effects of historical fuel changes last longer; smaller inertia... This indicates a rapid heat response, with recent fuel changes dominating. This exponential weighting method closely matches the actual temperature response characteristics of the heated surface (the impulse response of a first-order inertial system), and more accurately reflects the hysteresis nature of the thermodynamic system than simple arithmetic averages or rectangular window integrals.

[0059] S1232: Multiply the fuel change rate at each moment by its corresponding weighting coefficient, and then perform cumulative integration within the backtracking integration window to obtain the integration result.

[0060] For each discrete sampling point within the window, the fuel change rate is multiplied by the corresponding exponential decay weighting coefficient, and then the product of all sampling points is summed (integrated in the continuous domain). This summation operation is equivalent to performing a weighted moving average on the historical fuel change rate sequence, with the weighting curve exhibiting an exponential decay shape. Integration result. This value represents the cumulative equivalent heat of historical fuel fluctuations at the current moment, taking into account thermal inertia delay. A larger value indicates a greater recent increase in fuel supply and a stronger additional heat transfer to the heated surface.

[0061] S1233, by multiplying the integral result with the fuel-wall temperature sensitivity coefficient, we obtain the contribution of the fuel change rate to the wall temperature through the thermal inertia hysteresis link.

[0062] Fuel-wall temperature sensitivity coefficient It is a scaling factor that converts the unitless weighted integral result (or equivalent heat accumulation) into the actual wall temperature increment (unit: °C). The value is affected by boiler design, heating surface material, and current load point, and can be obtained through theoretical calculation or online identification. Final contribution value. It is directly superimposed on the trend extrapolation baseline value obtained in step S122, thus forming the complete wall temperature prediction value in step S124.

[0063] In conjunction with the first aspect, step S130 includes: S131, calculate the difference between the wall temperature safety limit and the predicted wall temperature, and use the difference as the prediction margin.

[0064] Wall temperature safety limit It is an alarm threshold set according to the allowable temperature of the heated surface metal material or the operating procedures (for example, the safe limit for the wall temperature of a certain superheater is 550℃).

[0065] The forecast margin is calculated using the following formula:

[0066] in, To predict margin.

[0067] Forecast margin Characterizing the future under the current operating state and prediction model. How much margin is left between the wall temperature and the safety limit after seconds?

[0068] when A larger value indicates that there is still sufficient safety margin in the heat load; when When the value is close to zero or even negative, it indicates that the wall temperature is about to exceed or has already exceeded the safety limit if no measures are taken. This prediction margin is the direct basis for the generation of subsequent coefficients. It quantifies the abstract risk of overheating into a difference with a clear engineering unit (unit: °C), which facilitates the setting of graded control strategies.

[0069] S132, Based on the comparison between prediction margin and safety buffer threshold, determine the flexibility correction coefficient.

[0070] Subsequently, the prediction margin is compared with the safety buffer threshold, and based on the comparison result, it is transformed into a flexible correction coefficient with a value range of [0,1] that varies continuously. This is used for subsequent dynamic adjustment of the variable load rate.

[0071] In conjunction with the first aspect, step S132 includes: S1321, if the prediction margin is greater than or equal to the safety buffer threshold, the flexibility correction coefficient is set to 1.

[0072] when This means that the predicted wall temperature is at least [missing information] away from the safe limit. The margin is sufficient (e.g., a safety buffer threshold of 10°C means the predicted wall temperature is at least 10°C below the limit). At this point, the heat load safety margin is deemed adequate, and even operating at the maximum load rate required by the power grid, overheating will not occur in the short term. Therefore, the flexibility correction factor is... or Setting it directly to 1 makes the actual load change rate... This means that the response speed requirements of AGC are fully met. Among them, This refers to the previous load change rate.

[0073] S1322, If the prediction margin is between 0 and the safety buffer threshold, calculate the flexibility correction coefficient based on the prediction margin and the safety buffer threshold.

[0074] when At that time, the predicted wall temperature had already entered the buffer warning zone, only a few seconds away from the safe limit. The system has a limited margin. If the load is still changed at full rate at this point, the wall temperature is highly likely to exceed the limit due to thermal inertia. Therefore, a flexibility correction factor between 0 and 1 needs to be calculated based on the specific margin value. or Should follow The rate decreases nonlinearly to achieve a tighter margin and a stronger rate limit.

[0075] S1323, if the prediction margin is less than or equal to 0, the flexibility correction factor is 0.

[0076] when At that time, it means the predicted wall temperature value The wall temperature has reached or even exceeded the safety limit. ,Right now ≥ If the load-changing operation in the direction of increasing load is not stopped immediately, the actual wall temperature will rise further due to thermal inertia, which could very likely trigger an over-temperature alarm or even a tube rupture accident. Therefore, the flexibility correction coefficient should be adjusted accordingly. or Setting it directly to 0 makes the actual load change rate... This means forcibly freezing the command output for the current load increase direction (or processing it according to the rollback strategy), thereby preventing the wall temperature from continuing to deteriorate. This value corresponds to the danger zone in the segmentation rules and is the last line of defense for the protection logic, ensuring the safety of the unit's heated surfaces.

[0077] In conjunction with the first aspect, step S1322 includes: S13221, calculate the quotient of prediction margin and safety buffer threshold.

[0078] First, calculate the ratio:

[0079] because Strictly between 0 and Between, therefore The value range is (0,1).

[0080] The ratio The prediction margin, which has specific engineering units (°C), is normalized to a dimensionless relative quantity, reflecting the proportion of the current margin to the safety buffer: when the margin approaches the safety buffer threshold, Approaching 1; when the margin approaches 0, Approaching 0.

[0081] S13222, calculate the power function of the quotient to obtain the flexible correction coefficient; where the power exponent in the power function is a real number greater than 0.

[0082] Normalized ratio To perform exponentiation, i.e.:

[0083] in, It is a real number greater than 0.

[0084] In practical applications, by selecting different The value allows for flexible adjustment of the sensitivity of the correction factor to the decrease in margin: when When the relationship is linear, the correction factor decreases proportionally to the margin; when... When the value is greater than 1 (e.g., 2 or 3), the function curve is concave, especially when the margin is large. or The descent is relatively slow (preserving a certain response speed), and the margin approaches zero. or The nonlinear characteristic of rapidly approaching 0 (achieving rapid braking) better meets the engineering requirements of minimizing speed limits in safe and ample areas and rapidly decelerating in dangerous and critical areas.

[0085] The power exponent can be adjusted on-site based on the characteristics of the boiler's heating surface and operating experience, with the preferred method being... or Calculated or This is the flexibility correction coefficient under this condition, which is directly used for the subsequent calculation of the actual variable load rate.

[0086] As can be seen, in this embodiment,

[0087] And on Perform saturation and image stabilization processing: .

[0088] Simultaneously set the hysteresis (e.g.) (Enter / exit the buffer zone at a temperature difference of 2~5℃) to avoid coefficient fluctuations.

[0089] Subsequently, the flexible correction coefficient With the load change rate required by the power grid Multiply by this to obtain the actual allowable rate of load change for the unit. .

[0090] In conjunction with the first aspect, step S150 involves rate limiting of the target load command based on the actual variable load rate to generate an AGC output command, specifically including: S151 inputs the target load command and the actual load change rate into the ramp limiter.

[0091] S152, the ramp limiter uses the actual load change rate as the upper limit of the change per unit time to limit the target load command, and generates and outputs the AGC output command after the speed limit.

[0092] Specifically, the AGC target instructions issued by the power grid will be... and the actual variable load rate obtained in step S140 Simultaneously, the ramp limiter (Ramp) function block is fed in. , is the dynamic rate after safety margin weighting, where This is a flexible correction factor. This refers to the initial load change rate required by the power grid. The ramp limiter is a standard functional module widely used in distributed control systems. Its function is to constrain the rate of change of the input signal, ensuring that the output signal changes smoothly at the set rate, thus preventing sudden changes in commands from impacting the actuators.

[0093] ramp limiter receiver and Afterwards, As the maximum allowable value of the output change per unit time (i.e., the upper limit of the rate of increase or decrease), for Perform speed limiting and generate the AGC output command after speed limiting. Within each sampling period, compare the current output value. With target input value The difference between them, if the absolute value of the difference is greater than (in (where the sampling period is), then with The slope approximates the target value; if the difference is within the allowable range, it directly follows the target value. When Follow When the slope is reduced, the rate of change of the output of the ramp limiter slows down synchronously, making The changes are more gradual. This dynamic speed limiting mechanism ensures that even if the grid requires a rapid change in load, the actual commands executed by the unit will not exceed the maximum rate allowed by the safety margin, thus fundamentally avoiding overheating of the heating surface caused by a sudden increase in load.

[0094] It should be further noted that, in the load reduction direction, the load reduction can be executed at the grid-required rate or the preset safe load reduction rate; while in the backoff state, it will be executed at the preset backoff rate. Execution is performed in the direction of load reduction. This ramp limiter achieves [the desired effect]. arrive The smooth mapping ultimately translates the continuous adjustment of the flexible correction coefficient into a smooth change in the AGC command. In conjunction with the first aspect, step S140 includes: S141, when the flexible correction coefficient is greater than or equal to the first threshold, the system enters the normal state.

[0095] Preset first threshold (For example This threshold corresponds to a boundary with sufficient safety margin. When or ≥ When the predicted wall temperature is far from the safe limit, it indicates that there is no risk of overheating during the current load change process. At this time, the state machine enters the normal state, and the unit operates at the actual load change rate described in step S150. (at this time (The actual rate is close to the grid's required rate) It normally tracks the AGC target load command to fully meet the grid regulation performance requirements.

[0096] S142, when the flexible correction coefficient is between the second threshold and the first threshold, the speed limiting state is entered.

[0097] Preset first threshold (For example ), and satisfy At this point, it indicates that the predicted wall temperature has entered the buffer warning zone, with insufficient safety margin but not yet reaching the critical danger level. The state machine then enters the speed-limiting state, and the unit continues to operate according to... Tracing instructions, but because The actual load change rate is lower than the grid's required rate, achieving speed reduction tracking. Under these conditions, as the margin decreases, from Gradually down to The load rate decreases synchronously and continuously, thereby preserving the unit's regulation capacity to the greatest extent possible under the premise of safety.

[0098] S143, when the flexibility correction coefficient is less than or equal to the second threshold, enter the frozen state or the rollback state.

[0099] In conjunction with the first aspect, step S143 includes: S1431, if the duration for which the flexible correction coefficient is less than or equal to the second threshold does not exceed the preset holding time, the system enters the frozen state.

[0100] S1432, if the duration for which the flexible correction coefficient is less than or equal to the second threshold exceeds the preset holding time, or if the predicted wall temperature reaches or exceeds the preset wall temperature safety limit, the system enters the retreat state.

[0101] when This indicates that the prediction margin has dropped to an extremely low level, and the wall temperature is approaching or has already approached the safety limit. At this point, the state machine enters either a frozen state or a rollback state depending on the specific circumstances. Specifically: when However, if the duration is short and the predicted wall temperature has not exceeded the limit, the system will first enter the freeze state, keep the AGC output command at the current value, block the further increase of the load command, and buy time for the pipe wall to dissipate heat. when The duration exceeds the preset holding time (e.g., 10~30s), or when the predicted wall temperature has reached or exceeded the safety limit, it enters the rollback state at a preset rollback rate. Actively reverse the AGC output command in the direction of load reduction to release the heat stored in the heated surface and avoid over-temperature accidents (see subsequent steps S160 and S170 for specific switching conditions of freezing and reversal).

[0102] Through the threshold comparison and state division in steps S141 to S143 above, step S140 will continuously adjust the flexible correction coefficient. This is mapped to discrete operating states, forming a progressively advancing safety protection chain of normal operation, rate limiting, and freeze rollback. The states can be linked according to... Real-time dynamic switching, with hysteresis ranges set at all switching boundaries to avoid [further issues]. Frequent state transitions caused by fluctuations around the threshold ensure the stability of the control system operation.

[0103] In step S160, the frozen state is when the flexibility correction coefficient is... Drop to the second threshold The following is a protection action triggered when the AGC command is in the load-increasing direction. In this state, the system forcibly reduces the output of the ramp limiter. It remains at the current value (i.e., the rate of change is zero) and no longer responds to any changes in the direction of load increase.

[0104] The core function of this state is to immediately block further increases in load commands when the forecast margin has dropped to an extremely low level (the predicted wall temperature is approaching the safety limit), thus allowing time for heat dissipation from the pipe wall metal and preventing delayed overheating due to thermal inertia. It should be noted that the freeze state only blocks actions in the direction of load increase, while the direction of load reduction is unrestricted. If the grid issues a load reduction command, the unit can still respond normally to facilitate rapid reduction of the heat load. The duration of the freeze state... Determined by the recovery status: if rebounded to (Exit threshold, and) If ), then exit the frozen state and resume normal or speed-limited tracking; if The duration exceeds the preset holding time If the predicted wall temperature deteriorates further to the point of reaching or exceeding the safety limit, the state machine will upgrade from the frozen state to the rollback state and execute an active load reduction operation.

[0105] In S170, the rollback state is the most powerful protective action in the entire safety chain, typically triggered when the frozen state cannot effectively curb the rising wall temperature. Triggering conditions include: 1. If The duration exceeds the preset holding time (e.g., 10~30s), indicating that even with a freeze order, the wall temperature remains at a dangerous level due to thermal inertia or continuous disturbance; 2. The predicted wall temperature has reached or exceeded the safety limit. This indicates that an overheating event is predicted to occur or has already occurred.

[0106] When any of the above conditions are met, the state machine enters a rollback state at a preset rollback rate. The AGC output command is proactively and gradually rolled back towards load reduction. This proactively reduces fuel input and unit load, fundamentally reducing furnace heat load and releasing excess heat stored in the heating surfaces, thereby effectively curbing further increases in wall temperature. The rollback process continues until the wall temperature prediction margin returns to a safe level (e.g., ...). To set a threshold for exiting rollback, a hysteresis is typically set, such as... When the condition is met, the state machine exits the rollback state and enters the normal or speed-limiting state. The rollback state is the last line of defense against delayed overheating and pipe bursting due to thermal inertia. Compared with the traditional passive alarm waiting strategy, its active load reduction strategy has the advantage of risk prevention and control.

[0107] To ensure stable transitions between the aforementioned frozen and rollback states of the state machine, and to avoid [further issues]... Small fluctuations near the boundary can cause frequent state transitions. This invention introduces a hysteresis interval within the state transition boundary. For example, the threshold for entering the frozen state is... The threshold for exiting the frozen state is set, and the difference between the two constitutes the hysteresis interval. This hysteresis setting effectively avoids frequent state machine switching caused by measurement noise or small parameter fluctuations, ensuring the smoothness of AGC output commands and the working life of the actuator.

[0108] Secondly, embodiments of this application provide an electronic device, combined with Figure 2As shown, the electronic device includes a memory 131 and a processor 130. The memory 131 stores a computer program, and the processor 130 runs the computer program to make the electronic device perform the above-described method.

[0109] Furthermore, combined Figure 2 The electronic device shown also includes a bus 132 and a communication interface 133, with the processor 130, the communication interface 133 and the memory 131 connected via the bus 132.

[0110] The memory 131 may include high-speed random access memory (RAM) and may also include non-volatile memory, such as at least one disk storage device. Communication between this system network element and at least one other network element is achieved through at least one communication interface 133 (which can be wired or wireless), such as the Internet, wide area network, local area network, metropolitan area network, etc. The bus 132 may be an ISA bus, PCI bus, or EISA bus, etc. The bus can be divided into address bus, data bus, control bus, etc. For ease of illustration, only a single bidirectional arrow is used in the figure, but this does not indicate that there is only one bus or one type of bus.

[0111] Processor 130 may be an integrated circuit chip with signal processing capabilities. In implementation, each step of the above method can be completed by the integrated logic circuitry in the hardware of processor 130 or by instructions in software form. Processor 130 may be a general-purpose processor, including a Central Processing Unit (CPU), a Network Processor (NP), etc.; it may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field-Programmable Gate Array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the methods, steps, and logic block diagrams disclosed in the embodiments of this invention. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the methods disclosed in the embodiments of this invention can be directly manifested as execution by a hardware decoding processor, or execution by a combination of hardware and software modules in the decoding processor. The software module can reside in a mature storage medium in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, or registers. This storage medium is located in memory 131, and processor 130 reads the information in memory 131 and, in conjunction with its hardware, completes the steps of the method described in the foregoing embodiments.

[0112] Thirdly, embodiments of this application provide a readable storage medium storing computer program instructions, which are read and executed by a processor to perform the above-described method.

[0113] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working process of the system and apparatus described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0114] Furthermore, in the description of the embodiments of the present invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the present invention based on the specific circumstances.

[0115] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, essentially, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0116] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0117] Finally, it should be noted that the above embodiments are merely specific implementations of the present invention, used to illustrate the technical solutions of the present invention, and not to limit it. The scope of protection of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments within the technical scope disclosed in the present invention, or make equivalent substitutions for some of the technical features; and these modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for AGC (Automatic Guided Control) variable load control of thermal power units, characterized in that, The method includes: Real-time acquisition of operating data of thermal power units, including at least heating surface wall temperature, fuel quantity, and actual load; The operating data is input into a preset wall temperature thermal inertia prediction model to calculate the predicted wall temperature value; A flexible correction coefficient is generated based on the prediction margin between the predicted wall temperature and the preset safety limit. The operating status of the AGC load command is determined based on the flexibility correction coefficient; the operating status includes normal status, speed limit status, freeze status, and rollback status. If the system is in the normal state or the speed-limited state, the required load change rate of the power grid is multiplied by the flexibility correction coefficient to obtain the actual load change rate. Based on the actual load change rate, the target load command is speed-limited to generate an AGC output command. If the system is in the frozen state, the AGC output command will remain at its current value. If the system is in the rollback state, the AGC output command will be rolled back in the direction of load reduction at a preset rollback rate.

2. The method according to claim 1, characterized in that, The steps of inputting the operating data into a preset wall temperature thermal inertia prediction model and calculating the predicted wall temperature include: Calculate the product of the current wall temperature change rate and the preset prediction step size to obtain the extrapolated increment of the wall temperature under the current trend; The extrapolated increment is added to the current wall temperature to obtain the estimated wall temperature value under the current trend. Based on the fuel change rate sequence within a set historical time period, calculate the contribution value of the hysteresis effect of fuel change rate on wall temperature. The predicted wall temperature is obtained by adding the current wall temperature, the extrapolated increment, and the hysteresis contribution of the fuel change rate.

3. The method according to claim 2, characterized in that, The steps for calculating the contribution of the hysteretic effect of fuel change rate on wall temperature based on the fuel change rate sequence over a set historical period include: For each moment in the fuel change rate sequence, a weighting coefficient is assigned to the fuel change rate that decays exponentially with time backtracking. The decay rate of the weighting coefficient is determined by the metal thermal inertia time constant. The fuel change rate at each time moment is multiplied by its corresponding weighting coefficient, and then the result is accumulated and integrated within the backtracking integration window to obtain the integral result. The product of the integral result and the fuel-wall temperature sensitivity coefficient is used to obtain the contribution of the fuel change rate to the wall temperature through the thermal inertia hysteresis link.

4. The method according to claim 1, characterized in that, The step of generating a flexible correction coefficient based on the prediction margin between the predicted wall temperature and the preset safety limit includes: Calculate the difference between the wall temperature safety limit and the predicted wall temperature, and use the difference as the prediction margin; The flexibility correction coefficient is determined based on the comparison between the prediction margin and the safety buffer threshold.

5. The method according to claim 4, characterized in that, The step of determining the flexibility correction coefficient based on the comparison between the prediction margin and the safety buffer threshold includes: If the prediction margin is greater than or equal to the safety buffer threshold, the flexibility correction coefficient is set to 1; If the prediction margin is between 0 and the safety buffer threshold, the flexibility correction coefficient is calculated based on the prediction margin and the safety buffer threshold. If the prediction margin is less than or equal to 0, the flexibility correction coefficient is 0.

6. The method according to claim 5, characterized in that, The step of calculating the flexibility correction coefficient based on the prediction margin and the safety buffer threshold includes: Calculate the quotient of the prediction margin and the safety buffer threshold; Calculate the power function of the quotient to obtain the flexible correction coefficient; Wherein, the exponent in the power function is a real number greater than 0.

7. The method according to claim 1, characterized in that, Based on the actual variable load rate, the target load command is rate-limited to generate an AGC output command, including: Input the target load command and the actual variable load rate into the ramp limiter; The ramp limiter uses the actual load rate as the upper limit of the change per unit time to limit the target load command, and generates and outputs the AGC output command after the speed limit.

8. The method according to claim 1, characterized in that, Determining the operating status of AGC load commands based on the aforementioned flexibility correction coefficient includes: When the flexible correction coefficient is greater than or equal to the first threshold, it enters the normal state; When the flexible correction coefficient is between the second threshold and the first threshold, the speed limiting state is entered; When the flexibility correction coefficient is less than or equal to the second threshold, the system enters the frozen state or the rollback state.

9. The method according to claim 8, characterized in that, When the flexibility correction coefficient is less than or equal to the second threshold, the system enters the frozen state or the rollback state, including: If the duration for which the flexibility correction coefficient is less than or equal to the second threshold does not exceed the preset holding time, the system enters the frozen state. If the duration for which the flexibility correction coefficient is less than or equal to the second threshold exceeds the preset holding time, or if the predicted wall temperature reaches or exceeds the wall temperature safety limit, the system enters the rollback state.

10. The method according to claim 1, characterized in that, Also includes: The prediction deviation of the wall temperature is calculated in real time. The prediction deviation is the difference between the current wall temperature and the current wall temperature value predicted at the previous prediction step time. Determine if the unit is in an active period of variable load. If the absolute value of the fuel change rate is greater than the preset threshold and the sensor signal is normal, then start parameter update. The recursive least squares method is used to assign decreasing weights to historical data with an exponential forgetting factor, and the fuel-wall temperature sensitivity coefficient and metal thermal inertia time constant are updated online. The updated fuel-wall temperature sensitivity coefficient and metal thermal inertia time constant are smoothed by first-order low-pass filtering and physical boundary hard limiting is applied to keep them within a preset reasonable constant range. The predicted wall temperature is iteratively updated based on the smoothed and limited fuel-wall temperature sensitivity coefficient and the metal thermal inertia time constant.

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