A fuel control method for a high operating condition sudden load shedding process of a power generation gas turbine

Abstract

The application provides a kind of power generation type gas turbine high operating condition sudden load shedding process fuel control method, belong to gas turbine control technical field, this method includes: obtaining generator trip signal;Continuously monitor the power generation of power generation type gas turbine, when trip signal is valid and power generation is greater than or equal to predetermined load operation, judge that high operating condition sudden load shedding occurs in gas turbine, at this time, exit speed closed loop control mode and execute fuel open loop control mode;In the process of fuel open loop control mode, start executing uniform rate cut oil, at the same time, execute the minimum oil pressure ratio limit curve corresponding minimum fuel supply, select the higher of the fuel supply corresponding to uniform rate cut oil and the minimum fuel supply corresponding to minimum oil pressure ratio limit curve to carry out fuel control;Continuously monitor power turbine speed, when power turbine speed is down-regulated to first predetermined interval, exit fuel open loop control mode;When power turbine speed continues to down-regulate to second predetermined interval, restore normal control.

Description

Technical Field

[0001] This application belongs to the field of gas turbine control technology, and specifically relates to a fuel control method for a generator-type gas turbine during a sudden load unloading process under high operating conditions. Background Technology

[0002] When a generator-type gas turbine operates in isolated grid conditions, such as in ship integrated electric propulsion systems or emergency power generation, generator or electrical load failures can cause circuit breaker tripping. In this situation, the gas turbine instantly loses all load. The most severe scenario is when the generator load system circuit breaker trips while the gas turbine is operating at 100% load, causing the gas turbine to suddenly unload 100% of its load. Due to the delayed change in the gas turbine's state, the power turbine output power may not have time to change during this sudden 100% load unloading. The remaining power turbine rotor power will cause the turbine speed Np to increase rapidly. Without efficient and safe fuel control during this process, at best, the turbine rotor will over-spin, failing to meet the speed regulation requirements of the generator-type gas turbine; at worst, the turbine rotor will spin wildly, damaging the turbine and generator structures.

[0003] There are two main types of fuel control mechanisms for the 100% load shedding process in existing power generation gas turbines: closed-loop speed control and open-loop fuel control. The closed-loop speed control mode uses PID regulation to control fuel quantity based on variables such as the deviation ΔNp (ΔNp = Npgd - Np) between the power turbine speed Np and the setpoint Npgd, and the rate of change of the power turbine speed Np, d(Np) / dt. To adapt to the speed regulation requirements of the gas turbine during the 100% load shedding process, most gas turbines use a higher core engine speed reduction limit rate and dedicated dynamic process PID control parameters after determining that they have entered the 100% load shedding phase. The open-loop fuel control mode is used when the system detects a sudden 100% load reduction. The commonly used open-loop fuel control mode is to rapidly reduce the fuel quantity according to the set fuel quantity function curve (such as Wfg = f(Nghs) curve, Wfg = f(Nghs, W0 curve, where Wfg is the fuel quantity setpoint, Nghs is the core engine converted speed, and W0 is the gas turbine inlet air flow). Once the fuel quantity reaches the target value, it is maintained until the Np speed drops back to the set range, after which the normal Np speed closed-loop control is resumed.

[0004] However, the existing closed-loop speed control mode has the following drawbacks when a generator-type gas turbine suddenly unloads 100% of its load:

[0005] 1) There is an inherent control delay defect. Fuel quantity control occurs after the power turbine speed Np changes. At the beginning of the 100% load unloading process, the overshoot of the power turbine speed Np does not increase significantly. The reduction of fuel quantity mainly comes from the differential control link of the power turbine speed change rate d(Np) / dt. The fuel quantity reduction rate is too small, and the critical opportunity to quickly reduce the fuel quantity and suppress the overshoot of the power turbine speed Np after the 100% load is unloaded is missed. After the power turbine speed Np increases rapidly, the fuel quantity Wfg decreases rapidly in the speed closed-loop control mode, which can easily lead to combustion and flameout problems due to excessive fuel cut-off.

[0006] 2) The PID control value significantly affects the control of fuel quantity Wfg, and it is difficult to find the optimal solution for the PID control value of the dynamic process. Exploring the PID control value of the dynamic process with good matching with the gas turbine through sudden load unloading test will bring huge test costs and test risks.

[0007] Similarly, the existing open-loop control mode for fuel also has the following drawbacks during the sudden unloading of 100% load from a generator-type gas turbine:

[0008] 1) After the gas turbine enters the load shedding transient control process, the fuel quantity is immediately cut off from the current value to the target value in a "cliff-like" manner. Although it will be limited by the fuel supply limit corresponding to the minimum fuel-air ratio limit curve in this process, the instantaneous and significant reduction in fuel quantity will inevitably lead to a sudden and drastic change in the fuel-air ratio in the combustion chamber. This can easily cause combustion shutdown, combustion oscillation and other combustion instability and aerodynamic mismatch phenomena. At best, it will lead to emergency shutdown of the gas turbine. At worst, it will lead to compressor surge, combustion shutdown and deflagration, etc., causing damage to the gas turbine.

[0009] 2) Although the minimum fuel-air ratio limit curve determined by the combustion chamber shutdown test ensures that the minimum amount of fuel is used during the load shedding and operating condition to improve the speed regulation performance of the gas turbine, the fuel-air ratio is close to the combustion shutdown boundary. Therefore, the rapid dynamic changes during the load shedding process of the gas turbine can easily lead to combustion shutdown. Moreover, after the power turbine speed Np enters the downward correction, there is no need to use too small a amount of fuel to make the gas turbine state recover quickly. Instead, it is easy to cause the power turbine speed Np to exceed the downward correction limit.

[0010] 3) The gas turbine load shedding process is a rapid dynamic change process. The W0 test has a certain delay and deviation, which causes the fuel-gas ratio parameter to be distorted. It cannot play a good role in accurately limiting the minimum fuel quantity during the load shedding process by using the minimum fuel-gas ratio. Summary of the Invention

[0011] The purpose of this application is to provide a fuel control method for a high-condition sudden load unloading process of a power generation gas turbine, so as to solve or mitigate at least one of the problems in the prior art.

[0012] The technical solution of this application is: a fuel control method for a generator-type gas turbine during a sudden load unloading process under high operating conditions, comprising:

[0013] Obtain the generator trip signal;

[0014] The generator set of the generator-type gas turbine is continuously monitored during operation. When the generator trip signal is valid and the generator set of the generator-type gas turbine is running at a load greater than or equal to the predetermined load, it is determined that the generator-type gas turbine has experienced a sudden load unloading under high operating conditions. At this time, the generator-type gas turbine exits the closed-loop control mode of the power turbine speed and starts to execute the open-loop control mode of fuel.

[0015] In the open-loop fuel control mode, the start point for fuel cut-off is when the generator trip signal is received. A uniform rate fuel cut-off is initiated, with the fuel quantity during this process being Wf1 = Wf - k * t, where Wf is the fuel quantity at time t0 when the generator trip signal is received, k is the fuel cut-off rate, and t is the duration relative to time t0. Simultaneously, the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve Wfmin = f(Nghs, Pt3) is executed. The higher of the fuel supply quantity Wf1 corresponding to the uniform rate fuel cut-off and the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve is selected for fuel control, where Nghs is the core engine's converted speed, and Pt3 is the compressor outlet total pressure.

[0016] The power turbine speed Np of the generator gas turbine in the open-loop fuel control mode is continuously monitored. When the power turbine speed Np drops back to the first predetermined range, the open-loop fuel control mode is exited and the power turbine speed closed-loop control mode is restored to perform load shedding. When the power turbine speed Np continues to drop back to the second predetermined range, the high-condition sudden load shedding process of the gas turbine is considered to be completed, and the gas turbine returns to normal control.

[0017] In an optional embodiment of this application, an invalid generator trip signal indicates that the generator set of the generator-type gas turbine has not tripped and shed load, while a valid generator trip signal indicates that the generator set of the generator-type gas turbine has tripped and shed load.

[0018] In an optional embodiment of this application, the predetermined load is 70% or more.

[0019] In an optional embodiment of this application, when the generator trip signal is valid and the generator set of the generator-type gas turbine is not running at the predetermined load, the speed closed-loop control mode is maintained to complete the load shedding control of the generator-type gas turbine.

[0020] In an optional embodiment of this application, if the power generation gas turbine is a dual-rotor power generation gas turbine, a venting valve is provided between the high-pressure and low-pressure compressors of the dual-rotor power generation gas turbine. When it is determined that the gas turbine experiences a sudden load unloading under high operating conditions, the venting valve opens to ensure that the operating margin of the low-pressure compressor meets the operating requirements during the sudden load unloading under high operating conditions.

[0021] In an optional embodiment of this application, the oil cutting rate k is selected as 40% to 80% of the fuel quantity of the generator gas turbine under rated operating conditions.

[0022] In an optional embodiment of this application, the process of obtaining the minimum oil pressure ratio limiting curve is as follows: First, obtain the minimum oil-gas ratio corresponding to the combustion chamber shutdown test. Then, convert the relationship between the inlet air flow W0 and the compressor outlet total pressure Pt3 within the full operating range of the gas turbine into the minimum oil pressure ratio of the gas turbine corresponding to the shutdown test. Then, obtain the oil pressure ratio operating envelope obtained from the actual low-condition load shedding test or simulation results of the gas turbine. Finally, obtain the minimum oil pressure ratio limiting curve by combining the oil pressure ratio operating envelope with the safety operating margin.

[0023] In an optional embodiment of this application, the process of determining the minimum oil supply quantity Wfmin corresponding to the minimum oil pressure ratio limit curve is as follows: based on the core machine converted speed Nghs at the current moment, the minimum oil pressure ratio limit value Wfmin / Pt3 at the current moment is interpolated on the minimum oil pressure ratio limit curve, and then the minimum oil supply quantity Wfmin is calculated back based on the total pressure Pt3 at the (high pressure) compressor outlet at the current moment.

[0024] In an optional embodiment of this application, a minimum fuel supply boundary value Wfbv is set during the fuel open-loop control mode. The fuel supply quantity Wf1 corresponding to uniform rate fuel cutting or the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve is not lower than the minimum fuel supply boundary value Wfbv during the fuel control process.

[0025] In an optional embodiment of this application, the first predetermined interval is less than or equal to 103% Npgd, and the second predetermined interval is less than or equal to 101% Npgd, where Npgd is the set speed of the power turbine.

[0026] The fuel control method of this application has the following advantages:

[0027] 1) When a power generation gas turbine experiences a sudden load shedding (or load rejection) under high operating conditions and switches to open-loop fuel control mode, a relatively fast and uniform fuel cut-off rate can be used to achieve precise following of the fuel regulation device, thus achieving a good match between the fuel control law and the fuel regulation system. This avoids the problems of combustion shutdown, combustion oscillation, and compressor stall caused by the large deviation in actual fuel supply due to the "cliff-like" fuel cut-off process in the existing technology, which is caused by the large instantaneous change in fuel quantity. This improves the operational safety of the gas turbine during the sudden load shedding process under high operating conditions and achieves a reasonable balance between good speed regulation performance and stable operation of the gas turbine.

[0028] 2) Compared with the minimum oil-gas ratio limiting curve in the existing technology, the minimum oil pressure ratio limiting curve adopts the total pressure parameter Pt3 of the compressor outlet with high dynamic sensitivity, and discards the gas turbine inlet air flow parameter W0, which will have obvious delay and distortion during the rapid change of gas turbine state. Therefore, it is more suitable for the rapid change of gas turbine state such as high-condition sudden load unloading (or high-condition load shedding), and the fuel quantity control is more accurate and scientific.

[0029] 3) The minimum oil pressure ratio limiting curve is formulated based on the minimum oil-air ratio limiting curve determined by the combustion chamber quench test, with a certain safety margin, to avoid the problem that the minimum oil-air ratio limiting curve in the existing technology is set close to the combustion quench boundary, which is easy to cause combustion quench. Attached Figure Description

[0030] To more clearly illustrate the technical solutions provided in this application, the accompanying drawings will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application.

[0031] Figure 1 This is a schematic diagram of the fuel control method of this application.

[0032] Figure 2 This is a schematic diagram of the minimum oil pressure ratio limiting curve according to an embodiment of this application.

[0033] Figure 3 This is a schematic diagram of the minimum oil pressure ratio change during a sudden unloading of 100% load according to an embodiment of this application.

[0034] Figure 4 This is a schematic diagram illustrating the change in fuel quantity during a sudden unloading of 100% load according to an embodiment of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings.

[0036] To avoid the problems of the minimum fuel-air ratio limit curve being close to the combustion shutdown boundary and easily leading to combustion shutdown, and the significant distortion of the gas turbine inlet air flow W0 in the fuel-air ratio during the dynamic process when a generator-type gas turbine suddenly unloads 100% (or experiences high-condition load shedding), this application proposes a highly efficient and safe fuel control method for generator-type gas turbines during high-condition load shedding. This method can fully tap the dynamic performance potential of the gas turbine, achieve good speed regulation performance indicators for the gas turbine, and ensure the safe operation of the gas turbine generator set during high-condition load shedding.

[0037] like Figure 1 As shown, the fuel control method for a high-condition sudden load unloading process of a power generation gas turbine (or simply gas turbine) according to this application includes the following steps:

[0038] S100: Obtain the generator trip signal. If the generator trip signal is invalid, it indicates that the gas turbine generator set has not tripped and shed load. If the generator trip signal is valid, it indicates that the gas turbine generator set has tripped and shed load. Based on the generator trip signal, it can be determined in a timely and accurate manner whether the gas turbine generator set has tripped and shed load.

[0039] S200 continuously monitors the power generation of the gas turbine generator set during operation to determine the operating load when the gas turbine generator set trips. When the generator trip signal is valid and the gas turbine generator set is running at the predetermined load, it is determined that the generator gas turbine has experienced a sudden load unloading under high operating conditions. At this time, the generator gas turbine is controlled to immediately exit the closed-loop control mode of the power turbine speed and start executing the fuel open-loop control mode.

[0040] When the generator trip signal is valid and the gas turbine generator set is not operating at the predetermined load, the current power turbine speed-maintaining closed-loop control mode can be used to complete the load shedding control of the current generator-type gas turbine.

[0041] In some embodiments of this application, the predetermined load described above is typically 70% or more.

[0042] In some embodiments of this application, for a dual-rotor power generation gas turbine, a vent valve can be installed between the high-pressure and low-pressure compressors. When it is determined that the gas turbine is experiencing a sudden load unloading under high operating conditions, the vent valve is opened in a timely manner to ensure that the operating margin of the low-pressure compressor meets the operating requirements during the sudden load unloading process under high operating conditions. At the same time, opening the vent valve can also reduce the output torque of the power turbine rotor, thereby improving the speed regulation performance.

[0043] In S300, during the open-loop fuel control mode, the start point for fuel cut-off is when the generator trip signal is received. A uniform rate fuel cut-off is initiated, with the fuel quantity during this process being Wf1 = Wf - k*t, where Wf is the fuel quantity at time t0 when the generator trip signal is received, k is the fuel cut-off rate, and t is the duration relative to time t0. Simultaneously, the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve Wfmin = f(Nghs, Pt3) is executed. The higher of the fuel supply quantity Wf1 corresponding to the uniform rate fuel cut-off and the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve is selected for fuel control. That is, when Wf1 corresponding to the uniform rate fuel cut-off by the gas turbine control system at a certain moment (e.g., time t1) is less than or equal to the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio at the current moment, the open-loop fuel control mode uses minimum fuel pressure ratio control.

[0044] In a preferred embodiment of this application, the fuel cut-off rate k is generally 40% to 80% of the rated fuel quantity of the gas turbine. For example, if the rated fuel quantity of the gas turbine is Wfr = 5000 L / h, then the fuel cut-off rate k can be set between (2000 and 4000) L / h / s, and can be specifically determined based on the speed regulation performance requirements, the dynamic characteristics of the gas turbine, and the simulation calculation results.

[0045] like Figure 2 The diagram shown is a schematic of the minimum oil pressure ratio limiting curve according to an embodiment of this application. The method for obtaining the minimum oil pressure ratio limiting curve includes the following process: First, the minimum oil-gas ratio corresponding to the combustion chamber shutdown test is obtained. Then, based on the relationship between the inlet air flow W0 and the total outlet pressure Pt3 of the (high-pressure) compressor within the full operating range of the gas turbine (which can be combined with the steady-state results, transient results, and simulation calculation results of the gas turbine, etc.), it is converted into the minimum oil pressure ratio of the gas turbine corresponding to the shutdown test (dashed curve). Then, based on the oil pressure ratio operating envelope (dotted curve) obtained from the actual low-condition load shedding test or simulation results of the gas turbine, and combined with a certain safety operating margin, the minimum oil pressure ratio limiting curve (solid curve) is obtained.

[0046] The method for determining the minimum oil supply Wfmin through the minimum oil pressure ratio limit curve is as follows: based on the core engine converted speed Nghs at the current moment, interpolate the minimum oil pressure ratio limit value Wfmin / Pt3 at the current moment on the minimum oil pressure ratio limit curve, and then calculate the minimum oil supply Wfmin based on the total pressure Pt3 at the (high pressure) compressor outlet at the current moment.

[0047] In a preferred embodiment of this application, a minimum fuel supply boundary value Wfbv is set during fuel control using either the fuel supply quantity Wf1 corresponding to a uniform rate fuel cut or the minimum fuel supply quantity Wfmin corresponding to a minimum fuel pressure ratio limit curve. The fuel quantity at any given time must not be lower than the minimum fuel supply boundary value Wfbv. Specifically, when the minimum fuel supply quantity Wfmin corresponding to a minimum fuel pressure ratio limit curve or the fuel quantity Wf1 during a uniform rate fuel cut process at a certain time t2 is less than or equal to the minimum fuel supply boundary value Wfbv, the fuel quantity is executed according to the minimum fuel supply boundary value Wfbv to ensure that the fuel quantity during the sudden unloading of 100% load meets the minimum limit requirements and fully ensures stable combustion.

[0048] S400 continuously monitors the power turbine speed Np of the gas turbine in the open-loop fuel control mode. When the power turbine speed Np drops back to a predetermined range at a certain moment t3 (e.g., Np≤Npgd+3%Npgd), it exits the open-loop fuel control mode and resumes the closed-loop power turbine speed control mode to shed load. When the power turbine speed Np continues to drop back to a value closer to the power turbine speed setpoint Npgd (e.g., Np≤Npgd+1%Npgd), it is considered that the gas turbine has completed the process of suddenly unloading 100% load, and the gas turbine returns to normal control.

[0049] like Figure 3 The diagram shows the change of fuel control mode on the minimum fuel pressure ratio limit curve during a sudden load unloading process of a gas turbine under high operating conditions. Figure 4 The diagram shows the fuel quantity change curve during the sudden unloading process of a gas turbine under high operating conditions. In this application, a minimum oil pressure ratio limiting curve with a certain safety margin is used to limit the minimum fuel quantity during the sudden unloading process under high operating conditions. The minimum oil pressure ratio uses the (high pressure) compressor outlet total pressure parameter Pt3, which has high dynamic sensitivity and high correlation with the gas turbine inlet air flow W0. This can not only accurately represent the oil-gas ratio value with the oil pressure ratio parameter, but also avoid parameter distortion, and ultimately achieve real-time and precise control of the fuel quantity.

[0050] The fuel control method of this application has the following advantages:

[0051] 1) When a power generation gas turbine experiences a sudden load shedding (or load rejection) under high operating conditions and switches to open-loop fuel control mode, a relatively fast and uniform fuel cut-off rate can be used to achieve precise following of the fuel regulation device, thus achieving a good match between the fuel control law and the fuel regulation system. This avoids the problems of combustion shutdown, combustion oscillation, and compressor stall caused by the large deviation in actual fuel supply due to the "cliff-like" fuel cut-off process in the existing technology, which is caused by the large instantaneous change in fuel quantity. This improves the operational safety of the gas turbine during the sudden load shedding process under high operating conditions and achieves a reasonable balance between good speed regulation performance and stable operation of the gas turbine.

[0052] 2) Compared with the minimum oil-gas ratio limiting curve in the existing technology, the minimum oil pressure ratio limiting curve adopts the total pressure parameter Pt3 of the compressor outlet with high dynamic sensitivity, and discards the gas turbine inlet air flow parameter W0, which will have obvious delay and distortion during the rapid change of gas turbine state. Therefore, it is more suitable for the rapid change of gas turbine state such as high-condition sudden load unloading (or high-condition load shedding), and the fuel quantity control is more accurate and scientific.

[0053] 3) The minimum oil pressure ratio limiting curve is formulated based on the minimum oil-air ratio limiting curve determined by the combustion chamber quench test, with a certain safety margin, to avoid the problem that the minimum oil-air ratio limiting curve in the existing technology is set close to the combustion quench boundary, which is easy to cause combustion quench.

[0054] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A fuel control method for a high-operating-condition sudden load unloading process of a power generation gas turbine, characterized in that, include: Obtain the generator trip signal; The generator set of the generator-type gas turbine is continuously monitored during operation. When the generator trip signal is valid and the generator set of the generator-type gas turbine is running at a load greater than or equal to the predetermined load, it is determined that the generator-type gas turbine has experienced a sudden load unloading under high operating conditions. At this time, the generator-type gas turbine exits the closed-loop control mode of the power turbine speed and starts to execute the open-loop control mode of fuel. In the open-loop fuel control mode, the start point for fuel cut-off is when the generator trip signal is received. A uniform rate fuel cut-off is initiated, with the fuel quantity during this process being Wf1 = Wf - k * t, where Wf is the fuel quantity at time t0 when the generator trip signal is received, k is the fuel cut-off rate, and t is the duration relative to time t0. Simultaneously, the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve Wfmin = f(Nghs, Pt3) is executed. The higher of the fuel supply quantity Wf1 corresponding to the uniform rate fuel cut-off and the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve is selected for fuel control, where Nghs is the core engine's converted speed, and Pt3 is the compressor outlet total pressure. The power turbine speed Np of the generator gas turbine in the open-loop fuel control mode is continuously monitored. When the power turbine speed Np drops back to the first predetermined range, the open-loop fuel control mode is exited and the power turbine speed closed-loop control mode is restored to perform load shedding. When the power turbine speed Np continues to drop back to the second predetermined range, the high-condition sudden load shedding process of the gas turbine is considered to be completed, and the gas turbine returns to normal control.

2. The fuel control method for a high-load sudden unloading process of a power generation gas turbine as described in claim 1, characterized in that, An invalid generator trip signal indicates that the generator set of the generator-type gas turbine has not tripped to shed load, while a valid generator trip signal indicates that the generator set of the generator-type gas turbine has tripped to shed load.

3. The fuel control method for a high-load sudden unloading process of a power generation gas turbine as described in claim 1, characterized in that, The predetermined load is 70% or higher.

4. The fuel control method for a high-load sudden unloading process of a power generation gas turbine as described in claim 3, characterized in that, When the generator trip signal is valid and the generator set of the power generation gas turbine is not running at the predetermined load, the power turbine speed closed-loop control mode is maintained to complete the load shedding control of the power generation gas turbine.

5. The fuel control method for a generator-type gas turbine under high operating conditions during sudden load unloading as described in claim 1, characterized in that, If the power generation gas turbine is a dual-rotor power generation gas turbine, a venting valve is installed between the high-pressure and low-pressure compressors of the dual-rotor power generation gas turbine. When it is determined that the gas turbine experiences a sudden load unloading under high operating conditions, the venting valve opens to ensure that the operating margin of the low-pressure compressor meets the operating requirements during the sudden load unloading under high operating conditions.

6. The fuel control method for a high-load sudden unloading process of a power generation gas turbine as described in claim 1, characterized in that, The oil cutting rate k is selected as 40% to 80% of the fuel quantity of the generator gas turbine under rated operating conditions.

7. The fuel control method for a high-load sudden unloading process of a power generation gas turbine as described in claim 1, characterized in that, The process of obtaining the minimum oil pressure ratio limiting curve is as follows: First, obtain the minimum oil-gas ratio corresponding to the combustion chamber shutdown test. Then, convert the relationship between the inlet air flow W0 and the compressor outlet total pressure Pt3 within the full operating range of the gas turbine into the minimum oil pressure ratio of the gas turbine corresponding to the shutdown test. Then, obtain the oil pressure ratio operating envelope obtained from the actual low-condition load shedding test or simulation results of the gas turbine. Finally, obtain the minimum oil pressure ratio limiting curve by combining the oil pressure ratio operating envelope with the safety operating margin.

8. The fuel control method for a generator-type gas turbine under high operating conditions during sudden load unloading as described in claim 7, characterized in that, The process of determining the minimum oil supply quantity Wfmin corresponding to the minimum oil pressure ratio limit curve is as follows: based on the core engine converted speed Nghs at the current moment, interpolate the minimum oil pressure ratio limit value Wfmin / Pt3 at the current moment on the minimum oil pressure ratio limit curve, and then calculate the minimum oil supply quantity Wfmin based on the compressor outlet total pressure Pt3 at the current moment.

9. The fuel control method for a generator-type gas turbine under high operating conditions during sudden load unloading as described in claim 7 or 8, characterized in that, In the open-loop fuel control mode, a minimum fuel supply boundary value Wfbv is set. During fuel control using either the fuel supply quantity Wf1 corresponding to uniform rate fuel cutting or the minimum fuel supply quantity Wfmin corresponding to the minimum fuel pressure ratio limit curve, the fuel supply quantity will not be lower than the minimum fuel supply boundary value Wfbv.

10. The fuel control method for a high-load sudden unloading process of a power generation gas turbine as described in claim 1, characterized in that, The first predetermined range is less than or equal to 103% Npgd, and the second predetermined range is less than or equal to 101% Npgd, where Npgd is the set speed of the power turbine.

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