A gas turbine fuel flow control method, system and computer readable storage medium thereof

Abstract

The application discloses a gas turbine fuel flow control method and system and a computer readable storage medium, and belongs to the technical field of gas turbine control, and comprises three steps of system control mode, determination of a fuel instruction and distribution of the fuel instruction, wherein the system control mode comprises a rotating speed and load control mode, a BPT control mode, an ITET control mode, a CDP control mode, a maximum fuel limitation mode, a speed-up stage control mode, an ACU control mode and a DCU control mode, so that the gas turbine can be safely and stably operated under preset working conditions under different working conditions, and the application has the advantages of safety, self-adaptation, high efficiency and the like.

Description

Technical Field

[0001] This invention belongs to the field of gas turbine control technology, specifically relating to a gas turbine fuel flow control method and system, and a computer-readable storage medium. Background Technology

[0002] Gas turbines and their combined cycle units have rapidly emerged and gained widespread application worldwide since the 1980s. Gas turbines and their combined cycles, using oil and natural gas as fuel, offer a series of advantages, including high overall cycle efficiency, minimal environmental pollution, good peak-shaving performance, and short construction periods, making them the development direction for thermal power systems. Currently, the control modes for gas turbines after grid connection are generally limited to speed control, load control, and temperature control. However, due to the instability of combustion, the operating conditions of gas turbines are inherently complex and variable. A single control mode may lead to reduced unit efficiency and increased combustion instability under certain operating conditions, potentially causing extreme conditions such as surge and overheating of hot components. Therefore, it is essential to develop different control strategies for different operating conditions of gas turbines.

[0003] In the prior art, invention patent CN102953835A discloses a stable operation control device and method for gas turbines. This device includes a start-up control module, a speed control module, a speed-load control module, an acceleration control module, a temperature control module, and a load shedding control module. It also includes a maximum limit module, a minimum limit module, a minimum value selector, and a maximum value selector. The control method employs a minimum value selector to design the main control system, achieving stable control of the gas turbine operation process. This can shorten the gas turbine joint commissioning time and reduce the commissioning costs incurred for the control system. In addition, invention patent CN111963323A discloses a fuel control method during the acceleration process of a gas turbine. This method, by controlling the fuel input method and rate during acceleration, enables the gas turbine to accelerate smoothly. Simultaneously, it accelerates as quickly as possible through speed ranges with high vibration or unstable combustion to avoid these ranges, thereby reducing pressure fluctuations in the control system, increasing the stability of the control system, and ensuring the safe, reliable, and stable operation of the gas turbine.

[0004] It is evident that existing patents have provided control schemes to achieve stable operation of gas turbine systems during the commissioning and speed-up phases of gas turbines. However, there is a lack of corresponding control methods for the stable operation of gas turbines under different operating conditions and operating modes. Therefore, this invention was developed. Summary of the Invention

[0005] The purpose of this invention is to provide a fuel flow control method for gas turbines. This method enables the gas turbine to operate safely and stably under different operating conditions, achieving the desired results under preset operating conditions. It offers advantages such as safety, adaptability, and high efficiency. To this end, this invention also provides a system for implementing this gas turbine fuel flow control method and its computer-readable storage medium, filling the gap in the prior art regarding the stable operation of gas turbines under complex and changing operating conditions.

[0006] This invention is achieved through the following technical solution: a gas turbine fuel flow control method, comprising the following steps: S1. System Mode Control: It should include at least the following control modes: Speed ​​and load control mode: Controls the unit's speed and target load to keep the unit's speed at the rated speed before and after grid connection, and controls the total fuel flow by controlling the gas turbine's load after grid connection; BPT control mode: controls the blade passage temperature to obtain the amount of fuel required by the system; ITET control mode: controls the gas turbine inlet temperature to obtain the amount of fuel required by the system; CDP control mode: Controls the compressor outlet pressure to obtain the amount of fuel required by the system; Maximum fuel limit mode: Set the maximum fuel setting value to obtain the corresponding required amount of fuel; Acceleration phase control mode: Controls gas turbine ignition and smooth acceleration to obtain the required amount of fuel; ACU control mode: fuel upper limit control, the fuel quantity is obtained based on the compressor outlet pressure and its corresponding fuel curve; DCU control mode: fuel lower limit control, where the fuel quantity is obtained based on the compressor outlet pressure and its corresponding fuel curve. S2. Determination of the fuel directive: The system compares the fuel quantities obtained from the speed and load control mode, BPT control mode, ITET control mode, CDP control mode, and maximum fuel limit mode, and takes the minimum value. This minimum value is then compared with the fuel quantities obtained from the acceleration phase control mode and ACU control mode, and the minimum value is taken. Finally, this minimum value is compared with the fuel quantity obtained from the DCU control mode, and the maximum value is taken. This maximum value is the final fuel command output by the system. S3. Assignment of fuel orders: The fuel command is proportionally distributed to the various control valves of the unit. Based on the valve CV curve set in the system, the gas flow rate is converted into the actual valve opening degree. Finally, the opening degree command is sent to each valve to achieve control of the gas flow rate.

[0007] The speed and load control modes include: during the full-speed no-load phase before the unit is connected to the grid, the speed of the unit is controlled and stabilized within the required range through the speed control loop; after the unit is connected to the grid, the total fuel flow is controlled using the load control mode.

[0008] The load control modes include: In manual load increase mode, the load setting in the gas turbine closed-loop control loop is set, and the accumulator is used to obtain the offset amount corresponding to the speed setting. Then, the gas turbine fuel is adjusted through differential regulation.

[0009] Automatic load increase mode: By setting the target load of the gas turbine, the load control loop of the control system enables the gas turbine to automatically increase or decrease its load.

[0010] In the manual load increase mode, the fuel adjustment range cannot be lower than the minimum load fuel value, and cannot exceed the upper limit fuel value.

[0011] In the automatic load increase mode, when the set target load of the gas turbine is greater than the feedback real-time load, the gas turbine is automatically increased; when the set target load of the gas turbine is less than the feedback real-time load, the gas turbine is automatically reduced.

[0012] A gas turbine fuel flow control system includes at least the following control modules: System control modules include: a speed and load control module to control the unit's speed and target load, ensuring the unit's speed remains at its rated speed before and after grid connection, and controlling the total fuel flow by controlling the gas turbine load after grid connection; a BPT control module to control blade passage temperature; an IET control module to control the gas turbine inlet temperature; a CDP control module to control the compressor outlet pressure; a maximum fuel limit module to set the maximum fuel setpoint; a ramp-up control module to control gas turbine ignition and smooth ramp-up; an ACU control module for controlling the upper fuel limit; and a DCU control module for controlling the lower fuel limit. Fuel Calculation Module: Calculates the amount of fuel required by the system under the control of the BPT control module, IITET control module, CDP control module, maximum fuel limit module, acceleration phase control module, ACU control module, and DCU control module. Analysis module: Compares the fuel quantities obtained from the speed and load control mode, BPT control mode, IET control mode, CDP control mode, and maximum fuel limit mode, and takes the minimum value. This minimum value is then compared with the fuel quantities obtained from the acceleration phase control mode and ACU control mode, and the minimum value is taken. Finally, this minimum value is compared with the fuel quantities obtained from the DCU control mode, and the maximum value is taken to obtain the final fuel command output by the system. Fuel distribution module: Distributes fuel commands proportionally to the various control valves of the unit. Based on the valve CV curve set in the system, it converts the gas flow rate into the actual valve opening degree and finally sends the opening degree specification to each valve to achieve control of the gas flow rate.

[0013] A computer-readable storage medium storing a computer program that, when executed by a processor, implements the gas turbine fuel flow control method described above.

[0014] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) This invention adopts a combination of multiple control modes, including: speed and load control modes, namely speed control mode and load control mode, which are switched by whether or not they are connected to the grid. Among them, the speed control mode can quickly stabilize the unit speed at the rated speed under load shedding or rapid load reduction conditions, so as to avoid overspeed, flameout and other situations. The BPT control mode can control and limit the blade passage temperature to protect the gas turbine exhaust section and exhaust section support ribs and other equipment. The turbine inlet temperature control mode can control and limit the turbine inlet temperature to protect the gas turbine high-temperature components from overheating. The CDP control mode (combustion chamber shell pressure control mode) can control and limit the compressor outlet pressure to avoid compressor surge, stall and other abnormal conditions. The maximum fuel limit mode can control and limit the fuel input to avoid the gas turbine high-temperature components from overheating. The maximum and minimum fuel limit modes can control and limit the fuel input to avoid the gas turbine high-temperature components from overheating or unit flameout. By combining the above-mentioned special control methods, it is possible to control the gas turbine to operate safely and stably according to the preset operating conditions, while protecting the gas turbine from some extreme operating conditions and avoiding unnecessary damage to the gas turbine under extreme conditions.

[0015] (2) This invention uses a combination of small-selection control logic and large-selection control logic to determine the fuel command. First, the small-selection control logic is used to obtain the minimum fuel quantity parameter from the speed and load control mode (total fuel flow), BPT control mode, IET control mode, CDP control mode, and maximum fuel limit mode to determine the operating range of the gas turbine under the current operating conditions. This can be used to avoid overheating of the gas turbine's hot components or overspeed of the unit. Second, the small-selection control logic is used again to obtain the minimum fuel quantity from the above minimum parameters and the fuel quantity of the acceleration stage control mode and ACU control mode, so that the acceleration can be stopped if a mode involving protection is triggered during the unit's acceleration process. Finally, the large-selection control logic is used to obtain the maximum fuel quantity from the above minimum fuel quantity and the fuel quantity of the DCU control mode. This can ensure that the gas turbine operates normally under the current operating conditions without causing the unit to shut down. This is used as the final fuel command for output and control, so as to achieve safe and stable operation of the gas turbine. Attached Figure Description

[0016] Figure 1 This is a system control block diagram of the gas turbine fuel flow rate according to the present invention.

[0017] Figure 2 This is a partial control block diagram (a) of the fuel flow of the gas turbine described in this invention.

[0018] Figure 3 This is a partial control block diagram (II) of the gas turbine fuel flow rate described in this invention.

[0019] Figure 4 This is a partial control block diagram (III) of the gas turbine fuel flow described in this invention. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto.

[0021] Example 1: This embodiment relates to a method for controlling the fuel flow rate of a gas turbine.

[0022] See Figure 1 As shown, it mainly includes speed and load control mode, BPT control mode, IET control mode, CDP control mode, maximum fuel limit mode, speed-up stage control mode, ACU control mode and DCU control mode. Each mode obtains the final fuel command by sequentially passing through small selection block A, small selection block B and large selection block A, and then distributes it to each control valve for output, so as to achieve safe and stable operation of gas turbine fuel flow.

[0023] In actual operation, the control methods of each mode can be summarized as follows: Mode 1: Speed ​​and load control mode.

[0024] Figure 2 The diagram shown is a control block diagram under the speed and load control mode. In this mode, the difference between the set speed and the actual speed is used to calculate the required fuel quantity through the proportional calculation function block. The set speed can be manually set within the range of 5000 to 6000 rpm.

[0025] The speed and load control modes include speed control mode and load control mode. The resulting fuel quantity is input 5 of the small selection block A. The speed control mode and load control mode are switched by whether or not grid connection is enabled. It should be noted that the speed and load control modes described in this embodiment do not directly participate in the small selection as two control modes. The load control mode essentially calculates the difference between the load setting and the actual load, and then adds it to the speed adjustment command setting through an accumulator. The actual final fuel quantity is still controlled by the speed control loop. Therefore, speed control and load control can be switched directly and seamlessly, and the mode change will not affect the current fuel quantity.

[0026] Before the generator is connected to the grid, in speed control mode, the difference between the set speed command and the actual speed is calculated, and a comparator determines whether the set speed value or the actual speed value is larger. After comparison, the difference is added to the speed regulation command at a certain rate (rpm / s) by an accumulator. After grid connection, the gas turbine is put into load control mode. In load control mode, the difference between the load command and the actual load is added to the set speed command by an accumulator, and finally, the fuel quantity is controlled through the speed control loop.

[0027] Specifically, in speed control mode, before the unit is connected to the grid, the control system raises the gas turbine speed to the set target speed of 5300 rpm through a speed-up program, entering speed control mode. After entering speed control mode, the unit automatically sets the target rated speed of 5928 rpm and automatically increases the speed to the rated speed. The speed control mode uses a step-by-step accumulation method to control the fuel quantity. When the set speed is greater than the actual speed, the total fuel quantity will be increased by one fuel component according to the speed command adjustment rate; when the set speed is less than the actual speed, the total fuel quantity will be decreased by one fuel component.

[0028] After the unit is connected to the grid, load control mode can be activated. In load control mode, the system converts the load setting into a superimposed component of the speed setting, and controls the total fuel flow through the speed control loop. This load control is used to control the gas turbine's load. After grid connection is complete, the control system will add a fuel step (approximately 7MW of fuel) to the current fuel quantity, bringing the gas turbine to its initial load (5% of rated load). Starting from this initial load, operators can select different modes to increase the gas turbine's load. There are two main load increase modes for the gas turbine, as follows: (1) First method: Manual load increase When manually increasing the load on the gas turbine, operators can set the load setting in the gas turbine's closed-loop control circuit and obtain the corresponding speed setting offset through an accumulator. Then, through differential adjustment, the gas turbine's fuel supply can be directly adjusted, allowing for rapid load increases and decreases. In manual control mode, the control system needs to limit the fuel adjustment range; the minimum fuel level cannot be lower than the minimum load fuel value, and the maximum cannot exceed the upper fuel limit value.

[0029] (2) Second type: Automatic load increase When the system selects the automatic load increase mode, operators can automatically increase or decrease the load on the gas turbine by setting the target load and utilizing the load control loop of the control system. The load increase rate has two levels: the first is the normal load increase mode with a rate of 3 MW / min, and the second is the rapid load increase mode with a rate of 6 MW / min. The two loading rates can be switched at any time via a button.

[0030] When the target load set by the gas turbine is greater than the real-time feedback load, the gas turbine load increase mode is triggered.

[0031] When the target load of the gas turbine is less than the real-time feedback load, the gas turbine load reduction mode is triggered. The minimum load setting of the gas turbine is 3.6MW (configurable).

[0032] Mode 2: BPT (Blade Passage Temperature) control mode, where the resulting fuel quantity is input 1 of small selection block A. (Reference) Figure 3 As shown, in this mode, the difference between the set temperature of the BPT temperature control mode and the actual BPT temperature is used to obtain the difference. Then, the required amount of fuel is calculated through the PI calculation function block. The set temperature of the BPT temperature control mode is 600℃.

[0033] Mode 3: IITET (Turbine Inlet Temperature) control mode, the resulting fuel quantity is input 2 of small selector block A. (Reference) Figure 3As shown, in this mode, the difference between the turbine inlet temperature set by the turbine inlet temperature control mode and the calculated current turbine inlet temperature is obtained. The required amount of fuel is then calculated through the PI calculation function block, where the turbine inlet temperature control mode set temperature is 1332℃.

[0034] Mode 4: CDP (Compressor Outlet Pressure) control mode, the resulting fuel quantity is input 3 of small selector block A. (Reference) Figure 3 As shown, in this mode, the difference between the compressor outlet pressure setpoint and the actual CDP pressure is used to obtain the difference, and then the required fuel quantity is calculated through the PI calculation function block, where the CDP setpoint is 1900 kPa.

[0035] Mode 5: Maximum fuel limit mode, the resulting fuel amount is input 4 from small selection block A. (Reference) Figure 3 As shown, in this mode, a maximum fuel setting value will be set, which is 125MW.

[0036] Mode 6: Acceleration phase control mode, the resulting fuel quantity is input 2 of small selection block B. (Reference) Figure 4 As shown, in this mode, the fuel quantity will be ignited and accelerated according to the preset fuel curve, and finally enter the speed control mode.

[0037] Mode 7: ACU (Fuel Upper Limit) control mode, the resulting fuel quantity is input 3 from small selection block B. (Reference) Figure 4 As shown, in this mode, the fuel quantity will be obtained based on the current CDP and the corresponding ACU fuel curve, as shown in Table 1 below.

[0038] Table 1 ACU fuel curve Mode 8: DCU (Fuel Lower Limit) control mode, the resulting fuel quantity is input 2 of the large block A. (Reference) Figure 4 As shown, in this mode, the fuel quantity will be obtained based on the current CDP and the corresponding DCU fuel curve, as shown in Table 2 below.

[0039] Table 2 DCU Fuel Curve Note: CDP: Compressor outlet pressure, in kPaA; CSO: Upper limit of fuel quantity / lower limit of fuel quantity, in MW.

[0040] To obtain the fuel command, the fuel quantities obtained from modes 1, 2, 3, 4, and 5 are compared, and the minimum value is taken. This minimum value is then compared with the fuel quantities obtained from modes 6 and 7, and the minimum value is taken. This minimum value is then compared with the fuel quantity obtained from mode 8, and the maximum value is taken. This maximum value is the final fuel command output by the system.

[0041] The final fuel command is subject to a fuel rate variation limit of 5 MW / s. This fuel command is then distributed proportionally to the main A fuel control valve, main B fuel control valve, and standby fuel control valve. The system then converts the gas flow rate into the actual valve opening based on the pre-defined valve CV curves, and finally sends the opening specification to each valve to control the gas flow rate.

[0042] In the process of controlling the gas flow, the manufacturer provides the valve characteristic curve (CV curve), which can be listed in Tables 3, 4 and 5 below.

[0043] Table 3 CV curves of the shift flow control valve Table 4 CV curve of main A flow control valve Table 5 CV curve of main B flow control valve Example 2: This embodiment relates to a gas turbine fuel flow control system.

[0044] System control modules include: a speed and load control module to control the unit's speed and target load, ensuring the unit's speed remains at its rated speed before and after grid connection, and controlling the total fuel flow by controlling the gas turbine load after grid connection; a BPT control module to control blade passage temperature; an IET control module to control the gas turbine inlet temperature; a CDP control module to control the compressor outlet pressure; a maximum fuel limit module to set the maximum fuel setpoint; a ramp-up control module to control gas turbine ignition and smooth ramp-up; an ACU control module for controlling the upper fuel limit; and a DCU control module for controlling the lower fuel limit. Fuel Calculation Module: Calculates the amount of fuel required by the system under the control of the BPT control module, IITET control module, CDP control module, maximum fuel limit module, acceleration phase control module, ACU control module, and DCU control module. The analysis module (small selection block A, small selection block B, and large selection block A) compares the fuel quantities obtained from the load control mode, BPT control mode, IITET control mode, CDP control mode, and maximum fuel limit mode, and takes the minimum value. This minimum value is then compared with the fuel quantities obtained from the acceleration phase control mode and ACU control mode, and the maximum value is taken. Finally, this maximum value is compared with the fuel quantities obtained from the DCU control mode, and the minimum value is taken. This results in the final fuel command output by the system. Fuel distribution module: Distributes fuel commands proportionally to the various control valves of the unit. Based on the valve CV curve set in the system, it converts the gas flow rate into the actual valve opening degree and finally sends the opening degree specification to each valve to achieve control of the gas flow rate.

[0045] Example 3: This embodiment relates to a computer-readable storage medium for implementing fuel flow control in a gas turbine.

[0046] The computer-readable storage medium stores a computer program that, when executed by a processor, implements the gas turbine fuel flow control method described in Example 1.

[0047] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for controlling fuel flow in a gas turbine, characterized in that: Includes the following steps: S1. System Mode Control: It should include at least the following control modes: Speed ​​and load control mode: Controls the unit's speed and target load to keep the unit's speed at the rated speed before and after grid connection, and controls the total fuel flow by controlling the gas turbine's load after grid connection; BPT control mode: controls the blade passage temperature to obtain the amount of fuel required by the system; ITET control mode: controls the gas turbine inlet temperature to obtain the amount of fuel required by the system; CDP control mode: Controls the compressor outlet pressure to obtain the amount of fuel required by the system; Maximum fuel limit mode: Set the maximum fuel setting value to obtain the corresponding required amount of fuel; Acceleration phase control mode: Controls gas turbine ignition and smooth acceleration to obtain the required amount of fuel; ACU control mode: fuel upper limit control, the fuel quantity is obtained based on the compressor outlet pressure and its corresponding fuel curve; DCU control mode: fuel lower limit control, where the fuel quantity is obtained based on the compressor outlet pressure and its corresponding fuel curve. S2. Determination of the fuel directive: The system compares the fuel quantities obtained from the speed and load control mode, BPT control mode, ITET control mode, CDP control mode, and maximum fuel limit mode, and takes the minimum value. This minimum value is then compared with the fuel quantities obtained from the acceleration phase control mode and ACU control mode, and the minimum value is taken. Finally, this minimum value is compared with the fuel quantity obtained from the DCU control mode, and the maximum value is taken. This maximum value is the final fuel command output by the system. S3. Assignment of fuel orders: The fuel command is proportionally distributed to the various control valves of the unit. Based on the valve CV curve set in the system, the gas flow rate is converted into the actual valve opening degree. Finally, the opening degree command is sent to each valve to achieve control of the gas flow rate.

2. The gas turbine fuel flow control method according to claim 1, characterized in that: The speed and load control modes include: during the full-speed no-load phase before the unit is connected to the grid, the speed of the unit is controlled and stabilized within the required range through the speed control loop; after the unit is connected to the grid, the total fuel flow is controlled using the load control mode.

3. The gas turbine fuel flow control method according to claim 2, characterized in that: The load control modes include: In manual load increase mode, the load setting in the gas turbine closed-loop control loop is set, and the accumulator is used to obtain the offset amount corresponding to the speed setting. Then, the fuel of the gas turbine is adjusted through differential regulation. In automatic load increase mode, the target load of the gas turbine is set, and the load control loop of the control system is used to make the gas turbine automatically increase or decrease the load.

4. The gas turbine fuel flow control method according to claim 3, characterized in that: In the manual load increase mode, the fuel adjustment range cannot be lower than the minimum load fuel value, and cannot exceed the upper limit fuel value.

5. The gas turbine fuel flow control method according to claim 3, characterized in that: In the automatic load increase mode, when the set target load of the gas turbine is greater than the feedback real-time load, the gas turbine is automatically increased; when the set target load of the gas turbine is less than the feedback real-time load, the gas turbine is automatically reduced.

6. A gas turbine fuel flow control system, characterized in that: It should include at least the following control modules: System control module: Speed ​​and load control module, used to control the unit's speed and target load, so that the unit's speed is controlled at the rated speed before and after grid connection, and after the unit is connected to the grid, the total fuel flow is controlled by controlling the gas turbine load; The BPT control module controls the blade passage temperature; the IET control module controls the gas turbine inlet temperature; the CDP control module controls the compressor outlet pressure; the maximum fuel limit module sets the maximum fuel setpoint; the acceleration phase control module controls gas turbine ignition and smooth acceleration; the ACU control module controls the upper fuel limit; and the DCU control module controls the lower fuel limit. Fuel Calculation Module: Calculates the amount of fuel required by the system under the control of the BPT control module, IITET control module, CDP control module, maximum fuel limit module, acceleration phase control module, ACU control module, and DCU control module. Analysis module: Compares the fuel quantities obtained from the speed and load control mode, BPT control mode, IET control mode, CDP control mode, and maximum fuel limit mode, and takes the minimum value. This minimum value is then compared with the fuel quantities obtained from the acceleration phase control mode and ACU control mode, and the minimum value is taken. Finally, this minimum value is compared with the fuel quantities obtained from the DCU control mode, and the maximum value is taken to obtain the final fuel command output by the system. Fuel distribution module: Distributes fuel commands proportionally to the various control valves of the unit. Based on the valve CV curve set in the system, it converts the gas flow rate into the actual valve opening degree and finally sends the opening degree specification to each valve to achieve control of the gas flow rate.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program that, when executed by a processor, implements the gas turbine fuel flow control method as described in any one of claims 1 to 5.

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