A gas-steam combined cycle unit agc optimization control method and system

Abstract

Embodiments of the present disclosure provide a gas-steam combined cycle unit AGC optimization control method and system. The method comprises: obtaining a power grid AGC load instruction and an actual load and speed; limiting the power grid instruction and the speed to obtain a reference instruction; calculating the difference between the reference instruction and the actual steam turbine load to obtain a preliminary gas turbine load instruction; determining the load regulation direction and the primary frequency modulation state of the current unit through a hysteresis comparator with a dead zone, and calculating the upper and lower limits of the gas turbine load instruction in real time; limiting the amplitude of the preliminary gas turbine load instruction according to the upper and lower limits to obtain a target gas turbine load instruction and output the target gas turbine load instruction to a gas turbine control system. Embodiments of the present disclosure solve the problem of frequent switching of load increase / decrease state and low AGC response rate of the gas turbine under small range and high frequency AGC instructions due to frequent intersection of the instructions and the actual load, ensure that the gas turbine maintains continuous one-way action during regulation, and significantly improve the response performance of the unit AGC load instruction.

Description

Technical Field

[0001] The embodiments disclosed herein belong to the field of gas turbine control technology, specifically relating to an AGC optimization control method and system for a gas-steam combined cycle unit. Background Technology

[0002] Automatic generation control (AGC) is a key technology in power systems. Grid dispatching issues AGC load commands to power plants within a region, adjusting the generation load of each plant / unit to ensure a balance between power consumption and generation. Power plants, in turn, must promptly adjust their output in response to the AGC load commands issued by the grid. The grid rewards or assesses power plants based on their AGC load command response. With the increasing proportion of renewable energy installed capacity, the frequency of grid AGC load command changes has significantly increased due to the indirectness and volatility of renewable energy generation, posing a challenge to the load regulation capabilities of power plants. Gas-steam combined cycle units, characterized by rapid load change rates, undertake more load regulation tasks in the power system. They receive grid AGC load commands with smaller amplitudes and faster frequency changes, thus requiring higher AGC response capabilities.

[0003] Traditional gas-steam combined cycle units respond to AGC load commands via a gas turbine (hereinafter referred to as the gas turbine), while the steam turbine (hereinafter referred to as the steam turbine) has its main control valve fully open and does not actively adjust the unit load. This is especially true when the grid AGC load command changes rapidly, as the adjustment time is very short and the steam turbine load remains almost unchanged. Generally, the DCS (distributed control system) coordinates and calculates the gas turbine load command and transmits it to the gas turbine TCS (turbine control system). Specifically, the difference between the grid AGC load command and the actual steam turbine load is used as the gas turbine load command. The TCS determines the relationship between the gas turbine load command and the actual gas turbine load and adjusts the unit output accordingly—increasing the load, maintaining the load, or decreasing the load—to match the grid AGC load command.

[0004] However, traditional control methods cannot adapt to the characteristics of current AGC load commands, which vary within a small range and at high frequency. Taking load increase as an example, the gas turbine load command obtained by subtracting the actual steam turbine load from the grid AGC load command is not much different from the actual gas turbine load. Affected by load fluctuations and primary frequency regulation, the gas turbine cannot guarantee that the gas turbine load command is greater than the actual gas turbine load at every moment when increasing the load. The gas turbine switches back and forth between three states: increasing load, decreasing load, and maintaining constant load. The rate of load increase is greatly limited, resulting in poor AGC performance and being subject to grid assessment, causing economic losses. Summary of the Invention

[0005] The embodiments disclosed herein aim to at least solve one of the technical problems existing in the prior art, and provide an AGC optimization control method and system for gas-steam combined cycle units.

[0006] One aspect of this disclosure provides an AGC (Automatic Generative Control) optimization control method for a gas-steam combined cycle unit, the method comprising: Obtain the grid AGC load command, actual combined cycle unit load, actual steam turbine load, actual gas turbine load, and actual gas turbine speed; The power grid AGC load command is subjected to amplitude and speed limiting processing to obtain the baseline AGC load command; The difference between the baseline AGC load command and the actual steam turbine load is calculated to obtain the preliminary gas turbine load command; The load adjustment direction and primary frequency regulation status of the current unit are determined by a hysteresis comparator with dead zone, and the upper and lower limits of the gas turbine load command are calculated in real time. Based on the upper and lower limits of the gas turbine load command, the initial gas turbine load command is subjected to amplitude limiting processing to obtain and output the target gas turbine load command to the gas turbine control system.

[0007] Furthermore, the step of determining the current load adjustment direction of the unit through a hysteresis comparator with dead time includes: The reference AGC load command is filtered to obtain the AGC load command filtered value, the actual combined cycle unit load is filtered to obtain the actual unit load filtered value, and the first deviation between the AGC load command filtered value and the actual unit load filtered value is calculated. The first deviation is input to the first hysteresis comparator. When the first deviation exceeds the first upper limit threshold, the first hysteresis comparator outputs a signal that the unit needs to increase its load. When the first deviation is lower than the first lower limit threshold, the first hysteresis comparator outputs a signal that the unit needs to decrease its load.

[0008] Furthermore, the step of determining the primary frequency modulation state using a hysteresis comparator with dead time includes: Calculate the second deviation between the actual gas turbine speed and the standard speed; The second deviation is input to the second hysteresis comparator. When the second deviation exceeds the upper limit threshold of the second deviation, the second hysteresis comparator outputs a primary frequency modulation load reduction signal; when the second deviation is lower than the lower limit threshold of the second deviation, the second hysteresis comparator outputs a primary frequency modulation load increase signal.

[0009] Furthermore, the real-time calculation of the upper and lower limits of the gas turbine load command includes: When the first hysteresis comparator outputs a signal indicating that the unit needs to increase its load and the second hysteresis comparator does not output a primary frequency regulation load reduction signal, the lower limit of the gas turbine load command is calculated using the following formula:

[0010] In the formula, This is the lower limit of the gas turbine load command. This represents the actual gas turbine load. This is the frequency modulation value. This is the first margin value.

[0011] Furthermore, the step of limiting the initial gas turbine load command based on the upper and lower limits of the gas turbine load command includes: The initial gas turbine load command is limited by taking the maximum value based on the lower limit of the gas turbine load command.

[0012] Furthermore, the real-time calculation of the upper and lower limits of the gas turbine load command includes: When the first hysteresis comparator outputs a signal indicating that the unit needs to reduce load and the second hysteresis comparator does not output a primary frequency regulation load increase signal, the upper limit of the gas turbine load command is calculated using the following formula:

[0013] In the formula, This is the upper limit of the gas turbine load command. This represents the actual gas turbine load. This is the frequency modulation value. This is the second margin value.

[0014] Furthermore, the step of limiting the initial gas turbine load command based on the upper and lower limits of the gas turbine load command includes: The initial gas turbine load command is limited by taking the smaller value based on the upper limit of the gas turbine load command.

[0015] Furthermore, the method also includes: When the first hysteresis comparator outputs the unit load increase signal and the second hysteresis comparator outputs the primary frequency regulation load decrease signal, or when the first hysteresis comparator outputs the unit load decrease signal and the second hysteresis comparator outputs the primary frequency regulation load increase signal, the target gas turbine load command is maintained as the initial gas turbine load command at the last moment before the conflict.

[0016] Furthermore, the process of limiting and speeding the power grid AGC load command includes: The limiting range is determined based on the upper and lower limits of the AGC load command, and the AGC load command of the power grid is limited. The power grid AGC load command is speed-limited based on the unit rate limit value.

[0017] Another aspect of this disclosure provides an AGC optimization control system for a gas-steam combined cycle unit, the system comprising: The data acquisition module is used to acquire the grid AGC load command, actual combined cycle unit load, actual steam turbine load, actual gas turbine load, and actual gas turbine speed. The reference instruction module is used to perform amplitude and speed limiting processing on the power grid AGC load instruction to obtain the reference AGC load instruction. The preliminary gas turbine command module is used to calculate the difference between the baseline AGC load command and the actual turbine load to obtain the preliminary gas turbine load command; The hysteresis comparison module is used to determine the current load adjustment direction and primary frequency regulation status of the unit through a hysteresis comparator with dead time, and to calculate the upper and lower limits of the gas turbine load command in real time. The target instruction module is used to limit the initial gas turbine load instruction based on the upper and lower limits of the gas turbine load instruction, and to obtain and output the target gas turbine load instruction to the gas turbine control system.

[0018] This disclosure discloses an AGC optimization control method and system for a gas-steam combined cycle unit. This method effectively solves the problems encountered by gas-steam combined cycle units under traditional control modes when responding to AGC commands on a small scale and at high frequency. These problems stem from the frequent and unpredictable switching between load increases, decreases, and load holding states, resulting in limited overall load change rate, poor AGC response performance, and grid assessment. The method ensures continuous unidirectional operation of the gas turbine during AGC regulation, significantly improving the unit's AGC response rate and overall regulation performance. This brings significant direct economic benefits to the power plant and enhances the stability and flexibility of the power grid. Attached Figure Description

[0019] Figure 1 This is a schematic flowchart of an AGC optimization control method for a gas-steam combined cycle unit according to an embodiment of the present disclosure; Figure 2 This is a control logic block diagram of an AGC optimization control method for a gas-steam combined cycle unit according to an embodiment of the present disclosure; Figure 3 This is a schematic diagram of the structure of an AGC optimization control system for a gas-steam combined cycle unit according to another embodiment of the present disclosure. Detailed Implementation

[0020] The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, and not all of them. Based on the embodiments of this disclosure, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this disclosure.

[0021] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details are provided in the following description to give a thorough understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced without one or more of the specific details, or other methods, components, apparatuses, steps, etc., can be employed. In other instances, well-known methods, apparatuses, implementations, or operations are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0022] The flowcharts shown in the accompanying drawings are merely illustrative and do not necessarily include all content and operations / steps, nor do they necessarily have to be performed in the described order. For example, some operations / steps can be broken down, while others can be combined or partially combined; therefore, the actual execution order may change depending on the specific circumstances.

[0023] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various components, these components should not be limited by these terms. These terms are used to distinguish one component from another. Therefore, the first component discussed below may be referred to as the second component without departing from the teachings of this disclosure. As used in this disclosure, the term "and / or" includes all combinations of any and more of the associated listed items.

[0024] Those skilled in the art will understand that the accompanying drawings are merely schematic diagrams of exemplary embodiments, and the modules or processes in the drawings are not necessarily necessary for implementing this disclosure, and therefore cannot be used to limit the scope of protection of this disclosure.

[0025] like Figure 1 As shown, one embodiment of this disclosure provides an AGC optimization control method for a gas-steam combined cycle unit, the method comprising: Step S1: Obtain the grid AGC load command, actual combined cycle unit load, actual steam turbine load, actual gas turbine load, and actual gas turbine speed.

[0026] Specifically, a dedicated AGC receiving server is deployed to receive AGC load settings from the power grid dispatch center (or the next higher-level AGC master station system) in real time through standard protocols of the power dispatch data network (such as IEC60870-5-104, IEC 61850, etc.) to obtain power grid AGC load instructions.

[0027] Obtain the actual combined cycle unit load from the DCS. P Actual gas turbine load P GT Actual gas turbine speed SPEED and actual turbine load P ST The actual steam turbine load can also be calculated in real time by subtracting the gas turbine load from the total load.

[0028] Step S2: Limit and speed the power grid AGC load command to obtain the baseline AGC load command.

[0029] Specifically, the limiting process ensures that the given AGC command remains within the adjustable range for safe and economical unit operation, preventing the unit from exceeding its capacity due to abnormal dispatch commands or communication errors. When the grid issues an AGC load command, it first passes through a maximum value module and a minimum value module, based on the upper limit of the AGC load command. AGCMAX and lower limit AGCMIN Determine the limiting range and restrict the power grid AGC load command to [ AGCMIN , AGCMAX Within the range. AGCMAX and AGCMIN The value is determined by the characteristics of the generator set, with an upper limit. AGCMAX Typically, the maximum adjustable output of the unit is taken, taking into account factors such as the upper limit of gas turbine output, the limitations of waste heat boiler and steam turbine under high load; lower limit value AGCMIN Typically, the minimum stable output or minimum technical output of the unit is used, which must ensure stable combustion under low load, normal operation of the denitrification system, and safe operation of the turbine. The upper and lower limits can be fixed or dynamically adjusted based on factors such as ambient temperature and equipment health. AGCMAX =460MW, AGCMIN =20MW.

[0030] Speed ​​limiting is used to restrict the rate of change of AGC load commands, ensuring it does not exceed the maximum allowable load change rate of the unit equipment. This is crucial for protecting thermal components from thermal shock and ensuring the unit's lifespan. The grid AGC load command, after being amplitude-limited, passes through a speed limiting module to restrict its rate of change to a unit rate limit determined by unit characteristics (such as the maximum acceptable main fuel valve change rate of the gas turbine, temperature difference limits of thermal aisle components, operating procedures, etc.). V (like V=20MW / min).

[0031] After the power grid AGC load command is limited in amplitude and speed, a baseline AGC load command is obtained. AGCL .

[0032] Step S3: Calculate the difference between the baseline AGC load command and the actual steam turbine load to obtain the preliminary gas turbine load command.

[0033] Specifically, the baseline AGC load command AGCL With actual turbine load P ST By performing the difference, a preliminary gas turbine load command is obtained. SP GT0 = AGCL P ST .

[0034] Step S4: Determine the current load adjustment direction and primary frequency regulation status of the unit using a hysteresis comparator with dead zone, and calculate the upper and lower limits of the gas turbine load command in real time.

[0035] Specifically, firstly, the baseline AGC load command... AGCL Perform first-order inertial filtering to obtain the AGC load command filtered value. AGCLF The filtering time constant needs to be set reasonably based on the typical fluctuation period of the power grid AGC command and the unit's response capability to smooth out high-frequency small fluctuations in the command without affecting the tracking of the effective command trend; at the same time, it should be adjusted according to the actual combined cycle unit load. P Perform first-order inertial filtering with the same or similar time constants to obtain the actual load filtering value of the unit. PF .calculate AGCLF and PF The difference is denoted as the first deviation. P _ ERR = AGCLF PF This represents the deviation between the smoothed AGC target command and the unit's current response. Filtering before difference calculation prevents signal fluctuations from causing subsequent hysteresis comparators to misjudge the unit's load change status.

[0036] Subsequently, a load-direction hysteresis comparator (denoted as the first hysteresis comparator) is used to determine whether the unit needs to increase or decrease load to track AGC commands. The hysteresis comparator is set with positive and negative direction thresholds and hysteresis. The first deviation... P _ ERR Input the first hysteresis comparator, when P _ ERR > P _ ERR _H When the first deviation upper limit threshold is reached, the comparator H terminal is set, and the "unit needs to increase load" signal is output until... P _ ERR < P _ ERR _ H-P _ ERR_DB (Dead zone), the comparator H terminal only returns to 0; when P _ ERR < P _ ERR _ L When the first deviation lower limit threshold is reached, the comparator L terminal is set, and a "unit needs to reduce load" signal is output until... P _ ERR > P _ ERR _ L+ P _ ERR_DB Only after the comparator's L terminal returns to 0. First deviation upper limit threshold. P _ ERR _ H First deviation lower limit threshold P _ ERR _ L and dead zones P _ ERR_DB The settings need to take into account the unit's load measurement error, command resolution, and the allowable error band to avoid frequent switching near the target value.

[0037] Subsequently, to avoid conflicts between AGC commands and primary frequency regulation requirements, which could lead to performance evaluation of the primary frequency regulation, it is necessary to identify such conflict states. The actual gas turbine speed must then be calculated. SPEED Compared with standard speed SPEED_NOM The difference (e.g., 3000 r / min) is denoted as the second deviation. SPEED_ERR = SPEED SPEED_NOM The second deviation SPEED_ERR Input a primary frequency modulation directional hysteresis comparator (denoted as the second hysteresis comparator). When the first hysteresis comparator outputs a "unit needs to increase load" signal, if... SPEED_ERR ≯ SPEED_ERR_H (Second deviation upper limit threshold), indicating that the grid frequency is not high, and it is determined that the primary frequency regulation demand does not conflict with the current AGC load command change direction; if SPEED_ERR > SPEED_ERR_H (Second deviation upper limit threshold) indicates that the grid frequency is too high, requiring the generating units to reduce output. In this case, it is determined that the primary frequency regulation demand conflicts with the current AGC load command change direction. AGC_HOLD The signal is 1. When the first hysteresis comparator outputs a "unit needs to reduce load" signal, if... SPEED_ERR < SPEED_ERR_LThe frequency regulation requirement conflicts with the current AGC load command change direction. AGC_HOLD The signal will also become 1.

[0038] Finally, based on the above judgment, upper and lower limits were calculated to ensure that the gas turbine load command can cover the primary frequency regulation amount, with a certain margin. SPEED_ERR Calculate the required primary frequency regulation based on the unit's speed inequality. PFR The functional relationship is shown below:

[0039] The function expression shown is for illustrative purposes only. In actual applications, it needs to be determined based on the characteristics of the generating unit and local power grid policies.

[0040] When the first hysteresis comparator outputs the "unit needs to increase load" signal and the second hysteresis comparator does not output a need for primary frequency regulation to reduce load, the lower limit of the gas turbine load command is calculated using the following formula:

[0041] In the formula, This is the lower limit of the gas turbine load command. This represents the actual gas turbine load. This is the frequency modulation value. This is the first margin value (e.g., 0.5). First margin value It is the minimum instruction increment to ensure the gas turbine can continuously increase its load. This value must be positive and take into account the tracking accuracy of the control system, the stability of the change trend, and the minimum safety margin to avoid frequent switching.

[0042] When the first hysteresis comparator outputs the "unit needs to reduce load" signal and the second hysteresis comparator does not output a need for primary frequency regulation to increase load, the upper limit of the gas turbine load command is calculated using the following formula:

[0043] In the formula, This is the upper limit of the gas turbine load command. This represents the actual gas turbine load. This is the frequency modulation value. This is the second margin value (e.g., 0.5). Second margin value It is the minimum command reduction to ensure the continuous load reduction of the gas turbine, and it is also a positive constant.

[0044] It should be noted that, and The appropriate gas turbine load command should be received by the gas turbine control system (TCS) through unit testing to continuously maintain load increase / decrease actions while avoiding excessive overshoot of the unit load. All parameters such as dead zone, hysteresis, threshold, and filter time constant of all hysteresis comparators should be configured in the control system for fine-tuning and optimization based on specific unit performance and control objectives.

[0045] Step S5: Based on the upper and lower limits of the gas turbine load command, the initial gas turbine load command is subjected to amplitude limiting processing to obtain and output the target gas turbine load command to the gas turbine control system.

[0046] Specifically, when the unit's load change direction does not conflict with the primary frequency regulation direction, and "the unit needs to increase load," the target gas turbine load command... SP GT The generation logic is as follows: SP GT = MAX( SP GT0 , SPGTMIN_CAL ),make sure SP GT Not lower than a lower limit (at which point the upper limit can be set to 999MW or the upper limit of the unit load command). AGCMAX= 460MW (no restrictions on current gas turbine load command, specific requirements not specified), even if small fluctuations in gas turbine load or grid frequency cause... SP GT0 With primary frequency modulation PFR The sum is occasionally slightly lower than the current actual gas turbine load. P GT The above logic can also force... SP GT Upgraded to SPGTMIN_CAL At this point, we have:

[0047] This allows the TCS to continuously identify clear "unit load increase" signals and continuously increase the load, avoiding frequent switching between "increase / maintain / decrease" states.

[0048] When the unit's load change direction does not conflict with the primary frequency regulation direction, and "the unit needs to reduce load," the target gas turbine load command... SP GT The generation logic is as follows: SP GT = MIN( SP GT0 , SPGTMAX_CAL ),make sure SP GT Not exceeding an upper limit (in which case the lower limit can be set to 0MW or the lower limit of the unit load command). AGCMIN=20MW (no restrictions on current gas turbine load command, specific requirements not specified), even if small fluctuations in gas turbine load or grid frequency cause... SP GT0 With primary frequency modulation PFR The sum is occasionally slightly higher than the current actual gas turbine load. P GT The above logic can also force... SP GT Reduce to SPGTMAX_CAL At this point, we have:

[0049] This allows the TCS to continuously identify clear "unit load reduction" signals and continuously reduce the load, avoiding frequent switching between "up / maintain / reduce" states.

[0050] When the direction of load change of the unit conflicts with the direction of primary frequency regulation, the primary frequency regulation demand should generally be given priority. AGCL The rate of change is limited to 0, its value will no longer change, and no limiting is performed. The initial gas turbine load command is directly output as the target gas turbine load command, i.e. SP GT = SP GT0 .

[0051] In addition, when the unit load deviation P_ERR When the load is within the steady-state dead zone, no load increase / decrease adjustment is needed to maintain the current load condition. In this case, the limiting function automatically deactivates. SP GT Keep as SP GT0 .

[0052] Finally, the target gas turbine load command will be... SP GT The TCS of the gas turbine is transmitted through a pre-set secure, high-speed, and low-latency communication link, which can typically be hardwired (4-20mA or ±10V analog signal) or a high-speed real-time industrial network (such as hard real-time Ethernet).

[0053] This step transforms the decision-making logic into a target gas turbine load command that can reliably, smoothly, and continuously enable the gas turbine to perform unidirectional load changes without the steam turbine making active small-range adjustments. This fundamentally solves the problem of frequent switching between load increase, decrease, and hold states when the gas turbine is subjected to small-range, high-frequency load changes under traditional methods, and significantly improves the AGC response index of combined cycle units.

[0054] The above process can be handled by, for example Figure 2 The control logic block diagram shown in the figure illustrates this. TIndicates the filter time constant. T 1 indicates the load on the unit. P The filtering time constant, T 2 indicates the reference AGC load command. AGCL The filtering time constant, s represents the Laplace operator, and FX represents the primary frequency modulation amount calculated from the speed deviation. PFR The function module.

[0055] This disclosure discloses an optimized AGC control method for gas-steam combined cycle units, which effectively solves the problems of repeated switching between load increase, decrease, and hold states of the gas turbine when responding to AGC load change commands in a small-range, high-frequency manner under traditional control modes. This is caused by the frequent interleaving and uncertain direction of the gas turbine load command and the actual gas turbine load, resulting in limited overall load change rate, deteriorated AGC response performance, and grid assessment. The method ensures that the gas turbine maintains a continuous unidirectional movement trend during AGC regulation, thereby significantly improving the unit's AGC response rate and regulation performance, bringing significant direct economic benefits to the power plant, and enhancing the stability and flexibility of the power grid.

[0056] like Figure 3 As shown, another embodiment of this disclosure provides an AGC optimization control system for a gas-steam combined cycle unit, the system comprising: Data acquisition module 310 is used to acquire grid AGC load commands, actual combined cycle unit load, actual steam turbine load, actual gas turbine load, and actual gas turbine speed; The reference instruction module 320 is used to perform amplitude and speed limiting processing on the power grid AGC load instruction to obtain the reference AGC load instruction; The preliminary gas turbine command module 330 is used to calculate the difference between the baseline AGC load command and the actual turbine load to obtain the preliminary gas turbine load command; Hysteresis Comparison Module 340 is used to determine the current load adjustment direction and primary frequency regulation status of the unit through a hysteresis comparator with dead time, and to calculate the upper and lower limits of the gas turbine load command in real time. The target instruction module 350 is used to limit the initial gas turbine load instruction based on the upper and lower limits of the gas turbine load instruction, and to obtain and output the target gas turbine load instruction to the gas turbine control system.

[0057] Specifically, the AGC optimization control system for a gas-steam combined cycle unit according to an embodiment of this disclosure is used to implement the AGC optimization control method for a gas-steam combined cycle unit described in the above embodiments. The specific implementation process has been described in detail in the above embodiments and will not be repeated here.

[0058] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for optimized AGC control of a gas-steam combined cycle unit, characterized in that, The method includes: Obtain the grid AGC load command, actual combined cycle unit load, actual steam turbine load, actual gas turbine load, and actual gas turbine speed; The power grid AGC load command is subjected to amplitude and speed limiting processing to obtain the baseline AGC load command; The difference between the baseline AGC load command and the actual steam turbine load is calculated to obtain the preliminary gas turbine load command; The load adjustment direction and primary frequency regulation status of the current unit are determined by a hysteresis comparator with dead zone, and the upper and lower limits of the gas turbine load command are calculated in real time. Based on the upper and lower limits of the gas turbine load command, the initial gas turbine load command is subjected to amplitude limiting processing to obtain and output the target gas turbine load command to the gas turbine control system.

2. The AGC optimization control method for gas-steam combined cycle units according to claim 1, characterized in that, The method of determining the current load adjustment direction of the unit through a hysteresis comparator with dead zone includes: The reference AGC load command is filtered to obtain the AGC load command filtered value, the actual combined cycle unit load is filtered to obtain the actual unit load filtered value, and the first deviation between the AGC load command filtered value and the actual unit load filtered value is calculated. The first deviation is input to the first hysteresis comparator. When the first deviation exceeds the first upper limit threshold, the first hysteresis comparator outputs a signal that the unit needs to increase its load. When the first deviation is lower than the first lower limit threshold, the first hysteresis comparator outputs a signal that the unit needs to decrease its load.

3. The AGC optimization control method for gas-steam combined cycle units according to claim 2, characterized in that, The determination of the primary frequency modulation state using a hysteresis comparator with dead time includes: Calculate the second deviation between the actual gas turbine speed and the standard speed; The second deviation is input to the second hysteresis comparator. When the second deviation exceeds the upper limit threshold of the second deviation, the second hysteresis comparator outputs a primary frequency modulation load reduction signal; when the second deviation is lower than the lower limit threshold of the second deviation, the second hysteresis comparator outputs a primary frequency modulation load increase signal.

4. The AGC optimization control method for gas-steam combined cycle units according to claim 3, characterized in that, The real-time calculation of the upper and lower limits of the gas turbine load command includes: When the first hysteresis comparator outputs a signal indicating that the unit needs to increase its load and the second hysteresis comparator does not output a primary frequency regulation load reduction signal, the lower limit of the gas turbine load command is calculated using the following formula: In the formula, This is the lower limit of the gas turbine load command. This represents the actual gas turbine load. This is the frequency modulation value. This is the first margin value.

5. The AGC optimization control method for gas-steam combined cycle units according to claim 4, characterized in that, The step of limiting the initial gas turbine load command based on the upper and lower limits of the gas turbine load command includes: The initial gas turbine load command is limited by taking the maximum value based on the lower limit of the gas turbine load command.

6. The AGC optimization control method for gas-steam combined cycle units according to claim 3, characterized in that, The real-time calculation of the upper and lower limits of the gas turbine load command includes: When the first hysteresis comparator outputs a signal indicating that the unit needs to reduce load and the second hysteresis comparator does not output a primary frequency regulation load increase signal, the upper limit of the gas turbine load command is calculated using the following formula: In the formula, This is the upper limit of the gas turbine load command. This represents the actual gas turbine load. This is the frequency modulation value. This is the second margin value.

7. The AGC optimization control method for gas-steam combined cycle units according to claim 6, characterized in that, The step of limiting the initial gas turbine load command based on the upper and lower limits of the gas turbine load command includes: The initial gas turbine load command is limited by taking the smaller value based on the upper limit of the gas turbine load command.

8. The AGC optimization control method for gas-steam combined cycle units according to claim 3, characterized in that, The method further includes: When the first hysteresis comparator outputs the unit load increase signal and the second hysteresis comparator outputs the primary frequency regulation load decrease signal, or when the first hysteresis comparator outputs the unit load decrease signal and the second hysteresis comparator outputs the primary frequency regulation load increase signal, the target gas turbine load command is maintained as the initial gas turbine load command at the last moment before the conflict.

9. The AGC optimization control method for a gas-steam combined cycle unit according to any one of claims 1 to 8, characterized in that, The process of limiting and speeding the power grid AGC load command includes: The limiting range is determined based on the upper and lower limits of the AGC load command, and the AGC load command of the power grid is limited. The power grid AGC load command is speed-limited based on the unit rate limit value.

10. An AGC optimization control system for a gas-steam combined cycle unit, characterized in that, The system includes: The data acquisition module is used to acquire the grid AGC load command, actual combined cycle unit load, actual steam turbine load, actual gas turbine load, and actual gas turbine speed. The reference instruction module is used to perform amplitude and speed limiting processing on the power grid AGC load instruction to obtain the reference AGC load instruction. The preliminary gas turbine command module is used to calculate the difference between the baseline AGC load command and the actual turbine load to obtain the preliminary gas turbine load command; The hysteresis comparison module is used to determine the current load adjustment direction and primary frequency regulation status of the unit through a hysteresis comparator with dead time, and to calculate the upper and lower limits of the gas turbine load command in real time. The target instruction module is used to limit the initial gas turbine load instruction based on the upper and lower limits of the gas turbine load instruction, and to obtain and output the target gas turbine load instruction to the gas turbine control system.

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