Control method and device adaptive to wide-step change of load instruction of thermal power unit AGC

Abstract

The application discloses a control method suitable for wide-step change of AGC load instruction of a thermal power unit, which comprises the following steps: correcting a unit variable load rate and a variable load feedforward coefficient; correcting a unit water-coal ratio parameter; adding a variable load instruction feedforward dynamic feedforward loop in a fuel main control loop; adding a load instruction change signal in feedforward of a unit primary air pressure control loop; when the unit is put into an AGC mode, an operation mode of first constant pressure, then sliding pressure and then constant pressure is adopted; and optimizing a turbine governing valve response load instruction logic. The method can overcome large-scale change of main parameters after the unit is put into the AGC mode, improve the adjusting speed, adjusting precision and response time of the unit to the AGC load instruction change, and improve evaluation indexes of the unit AGC operation mode under the premise of ensuring safety and stability of the unit. The application further discloses a control device suitable for wide-step change of AGC load instruction of a thermal power unit.

Description

Technical Field

[0001] This invention belongs to the field of thermal power generation technology, and in particular relates to a control method and device adapted to wide-step changes in AGC load commands of thermal power units. Background Technology

[0002] With the increasing demands of the power grid on the Automatic Generation Control (AGC) function of thermal power units, the AGC function plays a crucial role in maintaining power system frequency stability and the economical operation of grid dispatch. Simultaneously, the rapid response of the unit's AGC function can keep the main operating parameters of the unit under relatively stable conditions, which is also conducive to the safe and economical operation of thermal power units. Therefore, the AGC function of thermal power units has become an indispensable technical means in power production. The controlled object of the boiler-turbine coordinated control system of thermal power units has characteristics such as multivariables, strong coupling, nonlinearity, and large delay. The turbine responds quickly to the load, while the boiler is a large inertial component with heat storage capacity. The boiler response is slow, and the turbine relies on valve switching for regulation. The turbine's rapid regulation causes the boiler to lag behind the turbine's pace. The significant difference in the dynamic characteristics of the boiler and turbine leads to a mismatch between external load response and internal parameter stability.

[0003] The unit's coordinated control system responds quickly to changes in AGC load commands while ensuring stable unit parameters and safe operating conditions, and maintains the main steam pressure within a relatively stable range. The coordinated control system regulates unit load and main steam pressure by adjusting boiler combustion and turbine valve openings. Based on the analysis of the boiler and turbine's load response characteristics, improving the unit's load response rate involves two aspects: first, adjusting the turbine valve opening within the allowable range of main steam pressure to utilize the unit's heat storage capacity and improve the initial response rate to AGC load command changes; second, improving the boiler's load response rate and shortening the load response lag time by utilizing the boiler's heat storage capacity to enhance the unit's response rate to AGC commands. Simultaneously, appropriately increasing the overshoot for AGC load command changes helps the unit utilize the boiler's heat storage capacity and stabilize the main steam pressure. However, there are now new requirements for the frequency and magnitude of AGC load command adjustments for thermal power units, and new requirements for the requirements and standards for AGC in operation. This requires the control system characteristics, equipment reliability and sensitivity, and accuracy of the unit to reach a new level, and also raises the requirements for the control accuracy of the main parameters of the unit, such as main steam temperature and main steam pressure. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a control method and device adapted to wide-step changes in AGC load commands of thermal power units. This method can overcome the significant changes in the main parameters of the unit after AGC is put into operation, improve the unit's adjustment rate, adjustment accuracy, and response time to changes in AGC load commands, and enhance the evaluation indicators of the unit's AGC operation mode while ensuring the unit's safety and stability.

[0005] The present invention provides a control method adapted to wide-step changes in AGC load commands of thermal power units, comprising:

[0006] Correct the unit's load change rate and load change feedforward coefficient;

[0007] Correct the water-to-coal ratio parameters of the unit;

[0008] Add a dynamic feedforward loop for variable load commands to the fuel master control loop;

[0009] Add a load command change signal to the feedforward of the primary air pressure control loop of the unit;

[0010] When the unit is put into AGC mode, the operating mode of first stabilizing the pressure, then sliding the pressure, and then stabilizing the pressure is adopted.

[0011] Optimize the logic of the turbine control valve in response to load commands.

[0012] Preferably, in the above-mentioned control method adapted to the wide-step variation of AGC load commands of thermal power units, the corrected unit load variation rate is:

[0013] Increase the unit's load change rate to 7.5MW / min to 8.5MW / min.

[0014] Preferably, in the above-mentioned control method adapted to the wide-step variation of AGC load commands of thermal power units, the variable load feedforward coefficient of the corrected unit is:

[0015] Adjust the variable load feedforward coefficient of the unit to 1.5 to 2.

[0016] Preferably, in the above-mentioned control method adapted to the wide-step variation of AGC load commands for thermal power units, the correction of the unit's water-to-coal ratio parameter includes:

[0017] When the steam temperature at the outlet of the first-stage superheater exceeds the set value, a command to reduce the coal feed rate is issued.

[0018] When the temperature control deviation of the secondary superheater changes, adjust the coal feed rate until the main steam temperature stabilizes.

[0019] Preferably, in the above-mentioned control method adapted to the wide-step variation of AGC load commands in thermal power units, the addition of a dynamic feedforward loop for variable load commands in the fuel main control loop includes:

[0020] When the unit increases or decreases the load, and when the deviation between the unit's AGC command and the actual load is large, the variable load feedforward in the fuel main control circuit is corrected to increase or decrease the boiler coal feed.

[0021] When the unit is in steady state, the feedforward of the fuel main control fails when the unit changes load.

[0022] When the unit pressure pullback loop is locked, the fuel master control feedforward fails, and the fuel master control is regulated by the unit CCS control loop.

[0023] Preferably, in the above-mentioned control method adapted to the wide-step variation of load command in AGC of thermal power units, the addition of a load command change signal to the feedforward of the primary air pressure control loop of the unit is as follows:

[0024] After a load change, the primary air pressure control is given an action that precedes the PID adjustment based on the amount of load change.

[0025] Preferably, in the above-mentioned control method adapted to the wide-step variation of AGC load commands for thermal power units, the operation mode of first stabilizing pressure, then sliding pressure, and then stabilizing pressure when the unit is put into AGC mode includes:

[0026] The unit adopts constant pressure mode when the load range is 30%Pe to 40%Pe;

[0027] When the unit is in the 40%Pe to 80%Pe load range, it adopts sliding pressure operation mode;

[0028] When the unit is in the load range of 80% Pe or above, it adopts constant pressure operation mode.

[0029] Preferably, in the above-mentioned control method adapted to the wide-step variation of AGC load commands in thermal power units, the optimized turbine control valve response logic includes:

[0030] Set the turbine-side inertial environment to first-order inertia.

[0031] Preferably, in the above-mentioned control method adapted to the wide-step variation of AGC load commands in thermal power units, the optimized turbine control valve response logic further includes:

[0032] The allowable pressure fluctuation for adjusting the turbine control valve is ±0.5MPa to ±1MPa.

[0033] The present invention provides a control device adapted to wide-step changes in AGC load commands of thermal power units, comprising:

[0034] The first correction unit is used to correct the unit's load change rate and load change feedforward coefficient.

[0035] The second correction unit is used to correct the water-coal ratio parameters of the unit.

[0036] The first addition unit is used to add a variable load command feedforward dynamic feedforward loop to the fuel main control loop;

[0037] The second addition unit is used to add load command change signals to the feedforward of the primary air pressure control loop of the unit;

[0038] The operation mode adjustment unit is used to adopt the operation mode of first stabilizing pressure, then sliding pressure, and then stabilizing pressure when the unit is put into AGC mode;

[0039] The optimization unit is used to optimize the logic of the turbine control valve in response to load commands.

[0040] As described above, the control method for wide-step changes in AGC load commands of thermal power units provided by this invention, by including correcting the unit's load change rate and load change feedforward coefficient; correcting the unit's water-coal ratio parameter; adding a dynamic feedforward loop for load commands in the fuel main control loop; adding a load command change signal to the feedforward of the unit's primary air pressure control loop; adopting a pressure-suspension-pressure-suspension-pressure-reset operation mode when the unit is in AGC mode; and optimizing the turbine control valve's response logic to load commands, can overcome the large changes in the main parameters of the unit after AGC is activated, improve the unit's adjustment rate, adjustment accuracy, and response time to AGC load command changes, and improve the evaluation indicators of the unit's AGC operation mode while ensuring the unit's safety and stability. The control device for wide-step changes in AGC load commands of thermal power units provided by this invention has the same advantages as the above method. Attached Figure Description

[0041] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0042] Figure 1 This is a schematic diagram of an embodiment of a control method adapted to wide-step changes in AGC load commands of thermal power units provided by the present invention;

[0043] Figure 2 A logic diagram illustrating an example of optimizing the fuel master control feedforward signal;

[0044] Figure 3 A logic diagram illustrating an example of a feedforward signal control strategy for the primary air pressure control loop of a generator unit;

[0045] Figure 4 A logic diagram illustrating an example of determining a "stationary-sliding-stationary" operation mode after AGC is implemented;

[0046] Figure 5 This is a schematic diagram of the turbine-side response to AGC commands control strategy;

[0047] Figure 6 This is a schematic diagram of an embodiment of a control device adapted to wide-step changes in AGC load commands of thermal power units, provided by the present invention. Detailed Implementation

[0048] The core of this invention is to provide a control method and device that adapts to the wide-step variation of AGC load commands in thermal power units. This method can overcome the large changes in the main parameters of the unit after AGC is put into operation, improve the unit's adjustment rate, adjustment accuracy and response time to changes in AGC load commands, and improve the evaluation index of the unit's AGC operation mode while ensuring the unit's safety and stability.

[0049] The technical solutions of the embodiments 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, and 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.

[0050] An implementation example of the control method provided by this invention adapted to wide-step variations in AGC load commands of thermal power units Figure 1 As shown, Figure 1 This is a schematic diagram of an embodiment of a control method adapted to wide-step changes in AGC load commands of thermal power units provided by the present invention. The method may include the following steps:

[0051] S1: Correction of unit load change rate and load change feedforward coefficient;

[0052] It should be noted that the existing load change rate settings for thermal power units are lower than the 1.5% Pe required by regulations, failing to meet the load rate change requirements for AGC (Automatic Generation Control) operation. The main limiting factors include low boiler heat storage and unstable combustion during low load phases, leading to low load change rates; and excessively rapid load change rates during high load phases, which can easily cause high turbine vibration and boiler wall temperature overheating. Given these circumstances, setting the unit to operate at a lower load change rate to achieve stable unit operating conditions and key parameters is insufficient to meet the requirements for AGC operation. Therefore, based on the actual operating conditions of the thermal power unit, AGC tests should be conducted during the load increase phase, increasing the unit's load change rate as much as possible from the original setting to ensure the unit meets the AGC requirements. Furthermore, the variable load feedforward coefficient in the existing turbine main control loop of thermal power units is inappropriate. When the AGC load command arrives, the load command curve experiences a momentary spike, instantaneously releasing some of the boiler's stored heat. Therefore, to eliminate the momentary changes in the load command curve and enhance the sustained effect of boiler heat storage, the variable load feedforward coefficient in the turbine main control loop needs to be appropriately modified based on the actual operating conditions of the unit. Specifically, the preferred modification for the unit's variable load rate is to increase it to 7.5 MW / min to 8.5 MW / min; the preferred modification for the unit's variable load feedforward coefficient is to adjust it to 1.5 to 2.

[0053] S2: Correct the water-coal ratio parameter of the unit;

[0054] Specifically, the preferred methods for correcting the unit's water-coal ratio parameters include: reducing the coal feed rate when the primary superheater outlet steam temperature exceeds the set value; and adjusting the coal feed rate until the main steam temperature stabilizes when the secondary superheater temperature control deviation changes. It should be noted that, to improve the accuracy of main steam temperature regulation in AGC mode, the water-coal system control incorporates adjusting the coal feed rate setpoint through the water-coal ratio to eliminate temperature deviations in the water-coal system. When the primary superheater outlet steam temperature exceeds the set value, the coal feed rate is automatically reduced via logic; when the secondary superheater temperature control deviation changes, the coal feed rate is automatically adjusted via logic until the main steam temperature stabilizes. In the water-coal ratio control loop, if the boiler water-cooled wall temperature exceeds the alarm value, the current coal feed rate will be locked in the control loop and automatically reduced by 3.5t / h based on the current coal feed rate until the boiler water-cooled wall over-temperature alarm is cleared; if the secondary superheater inlet temperature alarm is cleared, the water-coal ratio control quantity will be reduced by -45t / h at a certain rate through the control logic until the secondary superheater inlet temperature alarm is cleared.

[0055] S3: Add a dynamic feedforward loop for variable load commands to the fuel main control loop;

[0056] It should be noted that due to the significant lag inherent in boilers, when the unit increases load following AGC commands, the boiler's heat storage is insufficient to meet the unit's fuel demand. Therefore, when the unit changes load according to AGC commands, a variable load command feedforward signal is added to the fuel main control system. By using unit operating data to obtain the coal feed rate for different load segments, the static feedforward parameter f1(x) of the unit can be obtained. When the unit is in AGC mode, the variable load static feedforward parameter cannot meet the coal feed rate requirements when the unit increases or decreases load. Therefore, based on the characteristics of unit load deviation changes, especially the current irregular wide-step changes in unit AGC commands, the static feedforward system needs to be optimized according to load deviation changes. Based on the characteristics of load change deviations, a variable load command dynamic feedforward loop is added to the fuel main control loop. Specifically, adding a dynamic feedforward loop for variable load commands to the fuel main control loop can preferably include: when the unit increases or decreases load, and when the deviation between the unit's AGC command and the actual load is large, correcting the variable load feedforward in the fuel main control loop by increasing or decreasing the boiler coal feed; when the unit is in steady state, the feedforward for fuel main control due to unit load changes fails; when the unit's pressure pullback loop is locked, the fuel main control feedforward fails, and at this time, fuel main control is regulated by the unit's CCS control loop. A specific example can be found here. Figure 2 , Figure 2 A logic diagram illustrating an example of optimizing the fuel master control feedforward signal, including:

[0057] 21—Unit boiler load command;

[0058] 22—AGC load command;

[0059] 23—Load command rate limiting module;

[0060] 24—Difference between boiler load command and the previous time;

[0061] 25—The difference between the boiler load command and the previous time point corresponds to the fuel master control feedforward;

[0062] 26—Difference between boiler load command and AGC command;

[0063] 27—The difference between the boiler load command and the AGC command corresponds to the fuel master control feedforward;

[0064] 28—AXSEL Analog Selection Block;

[0065] 29—The difference between the boiler load command and the AGC command is greater than 1MW or less than -1MW;

[0066] 210—AXSEL Analog Selection Block;

[0067] 211—Request for main steam pressure control circuit of unit;

[0068] 212-RS flip-flop;

[0069] 213—SUM addition logic block;

[0070] 214—Fuel master control feedforward value.

[0071] The difference between the unit boiler load command 21 and the unit AGC load command 22 is used to calculate the fuel master control feedforward signal by converting the differential pressure of the load command 27 (F(x)) corresponding to the fuel master control feedforward increase / decrease value. Then, the SUM addition logic block 213 adds the fuel master control feedforward value corresponding to the load difference to the original fuel master control feedforward value to obtain the optimized fuel master control feedforward value. In order to maintain the unit main steam pressure, the unit main steam pressure maintenance loop request signal 211 and RS trigger signal 212 are used to reset the feedforward value corresponding to the load command deviation in the fuel master control feedforward signal when the unit pressure maintenance loop requests it.

[0072] S4: Add a load command change signal to the feedforward of the primary air pressure control loop of the unit;

[0073] It should be noted that the preceding steps adjusted the unit's fuel master control feedforward value using the load command change signal, rapidly altering the unit's coal feed rate and boiler combustion to adapt to the load changes. However, the pulverizing process of the unit's pulverizing system requires a certain amount of time. The fuel master control feedforward signal only affects the coal feed rate, merely increasing the rate of actual load change, but not effectively reducing the load response delay. Therefore, adding a load command change signal to the feedforward in the unit's primary air pressure control loop can reduce the time consumed by the unit during the pulverizing process in the pulverizing system. Utilizing the pulverized coal stored in the operating coal mill allows for a rapid response to the unit's load command demands, effectively shortening the pure delay time of the unit's load response. Additionally, the load command change signal can be used to adjust the differential action in the primary air pressure control loop. Appropriately increasing the differential strength can enhance the initial process of load regulation, improving the unit's response rate to load commands in the initial stages of load command changes. Specifically, adding a load command change signal to the feedforward of the primary air pressure control loop of the unit can be preferably done by: after a load change, providing the primary air pressure control with an action that precedes the PID adjustment based on the amount of load change. A concrete example can be found here. Figure 3 , Figure 3 A logic diagram illustrating an example of a feedforward signal control strategy for the primary air pressure control loop of a generator unit, which includes:

[0074] 31—Boiler load command for the unit;

[0075] 32—AGC load command;

[0076] 33—Difference between boiler load command and AGC command;

[0077] 34--The difference between the boiler load command and the AGC command corresponds to the feedforward value of the primary air pressure control loop;

[0078] 35—Original feedforward signal value of the primary air pressure control loop;

[0079] 36--AXSEL Analog Selection Block;

[0080] 37--SUM addition logic block;

[0081] 38 -- Feedforward value of primary air pressure control loop;

[0082] 39—Intensity of the original differential action in the primary air pressure control loop;

[0083] 310—MULT multiplication logic block;

[0084] 311 -- The difference between the boiler load command and the AGC command is greater than 1MW or less than -1MW;

[0085] 312--AXSEL analog selection block;

[0086] 313—Intensity of differential action in primary air pressure control loop.

[0087] The difference between the unit boiler load command 31 and the unit AGC load command 32 is converted into the feedforward signal of the primary air pressure control loop by the feedforward increase / decrease value corresponding to the differential pressure of the load command 34 (F(x)). Then, the feedforward value of the primary air pressure control loop corresponding to the load difference is added to the original feedforward value of the primary air pressure control loop through the SUM addition logic block 37 to obtain the optimized feedforward value of the primary air pressure control loop. This can improve the unit's response rate to the load command in the early stage of load command change. The original differential action strength 39 of the primary air pressure control loop is strengthened by 1.5 times through the MULT multiplication logic block 310. Then, the AXSEL analog quantity selection block 312 is used to select to strengthen the differential action strength of the control loop when there is a deviation of more than 1MW between the unit load command and the AGC load command, so as to achieve the unit's rapid response to the load command in the early stage of load command change.

[0088] S5: When the unit is put into AGC mode, the operating mode of first stabilizing pressure, then sliding pressure, and then stabilizing pressure is adopted;

[0089] It should be noted that, from an energy-saving perspective, some existing units use a "manual sliding pressure operation mode," where operators set the main steam pressure value corresponding to the load based on their experience. This set main steam pressure value is generally lower than the main steam pressure value corresponding to the unit's sliding pressure curve, making it difficult for the unit to achieve ideal performance when AGC (Automatic Gain Control) is activated for load increases. Therefore, when the unit is in AGC operation, the current manual sliding pressure operation mode needs to be changed to seek an ideal sliding pressure curve operation mode. From the perspective of unit equipment reliability, the main steam pressure of the unit changes significantly in sliding pressure operation mode, affecting the internal equipment of the boiler. Therefore, under sliding pressure mode, attention must be paid to the fatigue wear of boiler equipment and the impact on superheater temperature. Taking into account factors such as unit load response, energy saving, and safe operation, a "constant pressure-sliding pressure-constant pressure" operation mode is adopted here when the unit is in AGC mode. Specifically, when the unit is put into AGC mode, the preferred operating mode of first setting pressure, then sliding pressure, and then setting pressure again can include: setting pressure mode when the unit is in the 30% to 40% Pe load range; using sliding pressure mode when the unit is in the 40% to 80% Pe load range; and using setting pressure mode when the unit is in the load range above 80% Pe. A specific example can be found here. Figure 4 , Figure 4 A logic diagram illustrating an example of determining a "stationary-slide-stationary" operation mode after AGC is implemented, which includes:

[0090] 41—Unit load command value;

[0091] 42—Determine if the unit load is greater than 40% Pe and less than 80% Pe;

[0092] 43—Manually engage the unit's sliding pressure operation mode;

[0093] 44-2 Input AND logic block;

[0094] 45—DXSEL switch selection logic block;

[0095] 46—2 input OR logic blocks;

[0096] 47—Activate the unit's sliding pressure operation mode;

[0097] 48—The unit is in AGC operation mode;

[0098] 49—Determine if the unit load is greater than 80% Pe;

[0099] 410—Determine if the unit load is greater than 30% Pe and less than 40% Pe;

[0100] 411-4 Input AND logic block;

[0101] 412--DXSEL switch selection logic block;

[0102] 413—Manually engage the unit's constant pressure operation mode;

[0103] 414--2 Input OR logic block;

[0104] 415 -- Put the unit into constant pressure operation mode.

[0105] After the unit is put into AGC mode, a "constant pressure-sliding pressure-constant pressure" operation control strategy is adopted. The unit load command value is 41. If the unit load is greater than 40% Pe and less than 80% Pe, the unit is put into AGC operation mode 48. The DXSEL switch selection logic block 45 allows the unit to manually enter sliding pressure operation mode 43. Through these logic blocks, the unit is automatically put into sliding pressure operation mode when operating in the load range of greater than 40% Pe and less than 80% Pe, and when the unit is in AGC mode. Similarly, by determining that the unit load is greater than 80% Pe, or greater than 30% Pe and less than 40% Pe, the DXSEL switch selection logic block 412 enables the unit to automatically enter constant pressure operation mode in the load range when the unit is in AGC mode.

[0106] S6: Optimize the logic of the turbine control valve response to load commands.

[0107] It should be noted that since the unit coordinated control system is based on boiler coordination, it adopts a method of accelerating boiler-side regulation and slowing down turbine-side regulation, thereby achieving different response times between the boiler and turbine to load. A proportional-derivative feedforward signal for the load command is added to the boiler side, and a third-order inertial delay element for the load command is added to the turbine side. Furthermore, when the main steam pressure deviation is large, the function of the turbine control valve will be limited by the nonlinearity of the unit. It is evident that the existence of the third-order inertial delay element on the turbine side delays the adjustment effect of the turbine control valve on the unit load command, giving the boiler time to store energy, which is beneficial to the energy supply balance of the unit and ensures the energy supply for load changes. Overall, it plays a good role in unit coordination and parameter stability. However, when this coordinated control system participates in AGC regulation, the turbine-side control valve control cannot receive the load command change signal in a timely manner, and the load response is slightly delayed, failing to keep up with the changes in AGC commands. Therefore, to adapt to the current wide-step adjustment of AGC load commands, optimize the coordinated control system strategy, appropriately adjust the third-order inertial delay on the turbine side, reduce pure delay time and parameter fluctuations, and in the inertial stage, reduce the original third-order inertial environment to first-order inertia. Furthermore, appropriately adjust the allowable pressure fluctuation value of the turbine valve action. This allows the main steam pressure parameter to fluctuate within a certain range during the initial stage of AGC command changes, meeting the requirements at the initial moment of load command changes. In practical applications, attention should also be paid to changes in main steam temperature to avoid large fluctuations in the unit's main parameters. Specifically, optimizing the turbine valve response to load commands can preferably include setting the turbine-side inertial environment to first-order inertia. Additionally, optimizing the turbine valve response to load commands can also preferably include adjusting the allowable pressure fluctuation value of the turbine valve action to ±0.5MPa~±1MPa. A specific example can be found here. Figure 5 , Figure 5 This is a schematic diagram of the turbine-side AGC command response control strategy, which includes:

[0108] 51—Unit load command value;

[0109] 52—Units are put into AGC mode;

[0110] 53—Third-order inertial element;

[0111] 54—AXSEL Analog Selection Block;

[0112] 55—First-order inertial element;

[0113] 56—Turbine-side load command value.

[0114] Here, by using the unit load command value 51, the unit's AGC mode activation 52, the third-order inertial link in the turbine main control 53, the first-order inertial link in the turbine main control 55, and the AXSEL analog selection block 54, the turbine main control's response to the load command is switched from the original third-order inertial link to the first-order inertial link after the unit is put into AGC operation mode. This reduces the pure delay time of the turbine main control to the load command and realizes the rapid response of the turbine main control to the load command.

[0115] This embodiment, through optimization of the control strategy, overcomes the significant changes in key parameters such as main steam temperature, main steam pressure, and turbine valve opening commands caused by the high frequency and wide step size changes of AGC load commands after the unit is put into AGC operation mode. It maintains the key parameters of the unit within the allowable range and improves the unit's adjustment rate, adjustment accuracy, and response time evaluation indicators when AGC load commands are high frequency and wide step size, while ensuring the safe and stable operation of the unit.

[0116] As described above, the embodiments of the control method adapted to the wide-step variation of AGC load commands in thermal power units provided by the present invention, by including correcting the unit's load change rate and load change feedforward coefficient; correcting the unit's water-coal ratio parameter; adding a dynamic feedforward loop for load change commands in the fuel main control loop; adding a load command change signal in the feedforward of the unit's primary air pressure control loop; adopting a first-constant-pressure-then-sliding-pressure-then-constant-pressure operating mode when the unit is put into AGC mode; and optimizing the turbine control valve's response logic to load commands, can overcome the large changes in the main parameters of the unit after AGC is put into operation, improve the unit's adjustment rate, adjustment accuracy, and response time to AGC load command changes, and improve the evaluation index of the unit's AGC operating mode while ensuring the unit's safety and stability.

[0117] An example implementation of a control device provided by the present invention that adapts to wide-step variations in AGC load commands of thermal power units. Figure 6 As shown, Figure 6 This is a schematic diagram of an embodiment of a control device adapted to wide-step changes in AGC load commands of thermal power units provided by the present invention. The device may include:

[0118] The first correction unit 601 is used to correct the unit's load change rate and load change feedforward coefficient.

[0119] The second correction unit 602 is used to correct the water-coal ratio parameter of the unit.

[0120] The first addition unit 603 is used to add a variable load command feedforward dynamic feedforward loop to the fuel main control loop;

[0121] The second addition unit 604 is used to add a load command change signal to the feedforward of the primary air pressure control loop of the unit;

[0122] The operation mode adjustment unit 605 is used to adopt the operation mode of first stabilizing pressure, then sliding pressure, and then stabilizing pressure when the unit is put into AGC mode;

[0123] The optimization unit 606 is used to optimize the logic of the turbine control valve in response to load commands.

[0124] The aforementioned methods and devices, while ensuring the safety and stability of the unit's main parameters, have improved the evaluation indicators of the unit's response to AGC load commands, and have achieved good application results in actual production. Taking a 350MW thermal power unit as an example, after the unit was put into AGC operation mode, the frequency and amplitude of AGC load command changes increased significantly compared to before. In order to improve the unit's response rate to AGC load commands, the unit implemented several optimization measures, including correcting the unit's load change rate and load change feedforward coefficient, correcting the unit's water-coal ratio parameters, optimizing the feedforward signal of the unit's fuel main control, optimizing the feedforward signal of the unit's primary air pressure control, automatically putting the unit into the "constant pressure-sliding pressure-constant pressure" operation mode, and optimizing the turbine control valve's response logic to load commands. After the unit was put into AGC mode, the unit's regulation rate K1, regulation accuracy K2, and response time K3 were all improved compared to before optimization.

[0125] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method adapted to wide-step variations in AGC load commands of thermal power units, characterized in that, include: Correct the unit's load change rate and load change feedforward coefficient; Correct the water-to-coal ratio parameters of the unit; Add a dynamic feedforward loop for variable load commands to the fuel master control loop; Add a load command change signal to the feedforward of the primary air pressure control loop of the unit; When the unit is put into AGC mode, the operating mode of first stabilizing the pressure, then sliding the pressure, and then stabilizing the pressure is adopted. Optimize the logic of the turbine control valve in response to load commands; The corrected unit load change rate is: Increase the unit's load change rate to 7.5 MW / min to 8.5 MW / min; The variable load feedforward coefficient of the modified unit is: Adjust the variable load feedforward coefficient of the unit to 1.5 to 2; The corrected unit water-to-coal ratio parameters include: When the steam temperature at the outlet of the first-stage superheater exceeds the set value, a command to reduce the coal feed rate is issued. When the temperature control deviation of the secondary superheater changes, adjust the coal feed rate until the main steam temperature stabilizes. In the coal-water ratio control loop, if the boiler water-cooled wall temperature exceeds the alarm value, the current coal feed rate is locked in the control loop, and automatically reduced by 3.5 t / h based on the current coal feed rate until the boiler water-cooled wall over-temperature alarm is cleared; if a high inlet temperature alarm for the secondary superheater occurs, the coal-water ratio control quantity is reduced at a certain rate through control logic until the secondary superheater inlet temperature alarm is cleared; the addition of a dynamic feedforward loop for variable load commands in the fuel main control loop includes: When the unit increases or decreases the load, and when the deviation between the unit's AGC command and the actual load is large, the variable load feedforward in the fuel main control circuit is corrected to increase or decrease the boiler coal feed. When the unit is in steady state, the feedforward of the fuel main control fails when the unit changes load. When the unit pressure pullback loop is locked, the fuel master control feedforward fails, and the fuel master control is regulated by the unit CCS control loop.

2. The control method adapted to wide-step changes in AGC load commands of thermal power units according to claim 1, characterized in that, The load command change signal added to the feedforward of the primary air pressure control loop of the unit is: After a load change, the primary air pressure control is given an action that precedes the PID adjustment based on the amount of load change.

3. The control method adapted to wide-step changes in AGC load commands of thermal power units according to claim 2, characterized in that, The operating mode of first stabilizing pressure, then sliding pressure, and then stabilizing pressure when the unit is put into AGC mode includes: The unit adopts constant pressure mode when the load range is 30%Pe to 40%Pe; When the unit is in the 40%Pe to 80%Pe load range, it adopts sliding pressure operation mode; When the unit is operating at a load of 80%Pe or higher, it adopts constant pressure operation mode.

4. The control method adapted to wide-step changes in AGC load commands of thermal power units according to claim 3, characterized in that, The optimized turbine control valve response load command logic includes: Set the turbine-side inertial environment to first-order inertia.

5. The control method adapted to wide-step changes in AGC load commands of thermal power units according to claim 4, characterized in that, The optimized turbine control valve response load command logic also includes: The allowable pressure fluctuation for adjusting the turbine control valve is ±0.5MPa to ±1MPa.

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