A fully automatic control strategy for dual-fuel switching of gas turbine generator sets

Abstract

This invention belongs to the field of generator set technology, and particularly relates to a fully automatic control strategy for dual-fuel switching in gas turbine generator sets. The invention includes control strategies before and after fuel switching, and a dual-fuel switching control strategy. This invention enables stable and reliable switching control between natural gas and syngas in dual-fuel gas turbine generator sets, shortening fuel switching time, reducing natural gas consumption, improving start-up economy, and ensuring smooth and undisturbed operation of the unit during fuel switching. The invention also considers changes in external factors, adding closed-loop control for combustion stability, achieving both speed and stability during dual-fuel switching, and enabling fully automatic control. It allows for smooth and undisturbed bidirectional online switching of the two fuels without shutting down the generator, ensuring rapid and stable control of parameters such as the average temperature and dynamic pressure at the unit's combustion chamber outlet.

Description

Technical Field

[0001] This invention belongs to the field of generator set technology, and in particular relates to a fully automatic control strategy for dual-fuel switching of gas turbine generator sets. Background Technology

[0002] Blast furnace gas (BFG), coke oven gas (COG), and converter gas (LDG) are byproducts of steel production and are considered secondary energy sources. Blast furnace gas, in particular, transfers approximately 60% of the energy from the fuel input to the blast furnace. With the rapid development of gas turbine technology and the need to improve the utilization efficiency of low-quality blast furnace gas and conserve resources in steel plants, heavy-duty gas turbine manufacturers, such as Kawasaki, Mitsubishi, and Westinghouse, have gradually developed high-efficiency gas turbine generator sets. The world's first combined cycle generator set using blast furnace gas as the working fluid was first put into operation at Baosteel in China. The success of this project greatly promoted the development of this technology in China. Subsequently, Tonghua Steel Plant, Ansteel, Shagang, Ma'anshan Steel Plant, and Jinan Steel Plant introduced and constructed blast furnace gas combined cycle generator sets, achieving good results. Combined cycle power generation units that burn blast furnace gas are gradually being widely used in steel plants due to their advantages such as short construction period, high thermal efficiency, low cooling water consumption, and good environmental performance, bringing good economic and social benefits to enterprises.

[0003] To meet energy conservation and emission reduction requirements, a steel plant constructed a new 180MW gas-steam combined cycle generator unit. This unit is the first gas turbine manufactured by Ansaldo, Italy, to use low-calorific-value mixed gas as fuel. Compared to conventional gas-liquid dual-fuel (natural gas-oil) gas turbines, this gas turbine adopts a gas-gas dual-fuel (natural gas-syngas) system. It uses low-calorific-value syngas (a mixture of blast furnace gas and coke oven gas, Synthetic Gas, SG) as the primary fuel for high-load operation, and high-calorific-value natural gas (NG) for ignition and startup for low-load operation and as backup fuel. Because the calorific value and volumetric flow rate of natural gas and syngas differ significantly, overheating, combustion oscillations, and even flameout are highly likely to occur during fuel switching, thus affecting the safe and stable operation of the unit.

[0004] In response to the above problems, those skilled in the art have made further technological updates and improvements. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides a fully automatic control strategy for dual-fuel switching in gas turbine generator sets. Its purpose is to achieve bidirectional fuel switching within a certain time frame, ensuring smooth and undisturbed operation of the unit during fuel switching, and guaranteeing reliable and stable bidirectional switching between natural gas and syngas fuels in the dual-fuel combustion chamber.

[0006] The technical solution adopted by the present invention to achieve the above objectives is as follows:

[0007] The fully automated control strategy for dual-fuel switching of gas turbine generator sets includes the following steps:

[0008] Step 1. Control strategy before and after fuel switching: In the initial stage of switching, first check and confirm whether the various indicators at the coal compressor outlet have reached the set values, and the unit load is in the load range of 40%-50% during fuel switching; In the final stage of switching, when the natural gas flow control valve gradually closes to the maximum nonlinear valve position of 10%, the natural gas flow control valve closes rapidly at the maximum closing rate; at the same time, the syngas to flare valve is closed, so that all the syngas enters the gas turbine for combustion.

[0009] Step 2. Dual-fuel switching control strategy: When the two fuels meet the switching conditions, the natural gas flow rate decreases from 100% to 0% at a set rate, and the syngas flow rate increases from 0% to 100% at a set rate; the syngas to the flare release valve is gradually closed at a rate of 5% / s, and the coal press outlet pressure is maintained at 18 bar through the recirculation regulating valve; during the switching process, closed-loop control of combustion chamber performance and closed-loop control of combustion stability are performed.

[0010] Furthermore, the various indicators at the outlet of the coal press include: syngas pressure, temperature, and calorific value.

[0011] Furthermore, the closed-loop control of the combustion chamber performance includes: a load controller, an exhaust temperature controller, and a compressor pressure limiter.

[0012] Furthermore, the combustion stability closed-loop control includes determining whether the gas turbine is burning stably by measuring the dynamic pressure changes in the combustion chamber and the dynamic amplitude changes of the oscillations generated by combustion. The combustion stability closed-loop control uses humming and ACC as performance indicators and adjusts the combustion state in real time according to a pre-set adjustment curve. When combustion is unstable, the humming and acceleration are used to reflect the combustion instability in real time. Before the combustion deteriorates, the gas turbine exhaust temperature setpoint, IGV opening, and natural gas flow are automatically adjusted to ensure that all parameters of the unit are adjusted to the optimal state during fuel switching.

[0013] Furthermore, the dual-fuel switching control strategy includes a natural gas fuel system and a syngas fuel system.

[0014] Furthermore, the natural gas fuel system uses natural gas as the ignition fuel for the gas turbine, controls the mass flow rate of natural gas entering the gas turbine combustion chamber, and prevents natural gas from entering the gas turbine under specific conditions. The system consists of a pre-filter module, a natural gas emergency shut-off valve, a natural gas vent valve, a natural gas control valve, and a natural gas ball valve. The pre-filter prevents any coarse foreign matter in the pipeline between the upstream fine filter unit and the filter from entering the natural gas emergency shut-off valve. The natural gas emergency shut-off valve supplies or cuts off the natural gas entering the burner during gas turbine startup and shutdown, as well as during natural gas system startup or shutdown. After the natural gas emergency shut-off valve, the gas supply pipeline splits into two branches: one leads to the syngas system, and the other directly enters the combustion chamber through the diffusion burner. The vent valve is located between the natural gas emergency shut-off valve and the natural gas control valve to discharge the natural gas in the pipeline section between the shut-off valves into the air. The natural gas control valve controls the flow rate of natural gas supplied to the diffusion burner according to the requirements of the gas turbine control system. Each pipeline leading to the combustion chamber is equipped with a natural gas ball valve to supply or cut off the flow of natural gas to the burner.

[0015] Furthermore, the syngas fuel system controls the mass flow rate of syngas entering the gas turbine combustion chamber and cuts off the syngas supply to the gas turbine in the event of gas turbine protection action or emergency shutdown; the syngas from the coal compressor outlet has one path leading to the flare for adjusting the syngas calorific value, and another path leading to the burner, which, after passing through the filter outlet, connects to two branch pipelines for combustion chamber A and combustion chamber B respectively. The burner branch pipeline is equipped with a syngas shut-off valve assembly, including: a syngas emergency shut-off valve, a syngas vent valve, and a syngas control valve.

[0016] Furthermore, the burner has three different fuel gas nozzle piping systems, including: a diffuser piping, a syngas piping, and a standby gas piping; the diffuser piping is used for starting with minimum fuel quantity, accelerating to rated speed, and operating under partial load until load switching; the standby gas piping is a fuel line used to promote burner operation; the syngas piping is used to burn the syngas from load switching to base load; the syngas flow passes through a syngas cyclone separator and enters the combustion chamber, where it mixes with and burns with combustion air. Air is supplied to the burner through the combustion air inlet via an oblique cyclone separator and a central axial cyclone separator; a small amount of combustion air enters the internal air passage and enters the combustion chamber through the central axial cyclone separator; a smaller portion of the combustion air is used to cool the central nozzle, and the remaining combustion air flows through the oblique cyclone separator.

[0017] Furthermore, the gas turbine adopts a dual-fuel gas turbine control system for dual-fuel switching during operation. From ignition, speed increase, speed maintenance, grid connection to the fuel switching load point of 40%-50%, natural gas is used as fuel. After the natural gas is pressurized to a predetermined pressure by the booster, it passes through a pre-filter and enters the combustion chamber through the natural gas fuel passage via the natural gas control valve. During this stage, the syngas fuel passage and other valves are closed. After the unit load reaches a certain initial load, the fuel switching is carried out quickly.

[0018] Furthermore, the dual-fuel switching must be carried out after confirming that the fuel supply parameters, including calorific value, pressure and temperature, meet the requirements; the switching process includes two stages: the syngas fuel adjustment stage and the fuel dynamic switching stage.

[0019] Syngas fuel conditioning stage: Adjusting the calorific value of syngas through flare release;

[0020] Dynamic fuel switching phase: Once the calorific value, temperature and stress of the syngas meet the switching requirements, select one-click switching, and the dynamic switching phase will begin.

[0021] The present invention has the following beneficial effects and advantages:

[0022] This invention proposes a one-button, fully automated control strategy for dual-fuel gas turbine generator sets, based on the functions of the gas turbine control system and the dual-fuel switching process. This invention enables smooth, uninterrupted online bidirectional switching of the two fuels without shutting down the generator set, ensuring rapid and stable control of parameters such as the average temperature and dynamic pressure at the combustion chamber outlet. It can complete bidirectional fuel switching within a certain time range and ensures smooth, uninterrupted operation of the unit during fuel switching, guaranteeing reliable and stable bidirectional switching between natural gas and syngas fuels in the dual-fuel combustion chamber, filling a technological gap in this field.

[0023] Multiple switching tests have shown that the control strategy of this invention can achieve stable and reliable switching control between natural gas and syngas in dual-fuel gas turbine generator sets, shortening fuel switching time, reducing natural gas consumption, and improving the unit's start-up economy. This invention also considers changes in external factors and adds closed-loop control for combustion stability, achieving both speed and stability during dual-fuel switching. The control strategy of this invention achieves fully automatic control throughout the initial, final, and subsequent switching phases, ensuring rapid and stable control of all unit parameters. Attached Figure Description

[0024] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0025] Figure 1 This is a shaft system arrangement diagram of the gas turbine generator set of the present invention;

[0026] Figure 2 This is a schematic diagram of the natural gas fuel system of the present invention;

[0027] Figure 3 This is a schematic diagram of the syngas fuel system of the present invention;

[0028] Figure 4 This is a schematic diagram of the cylindrical combustion chamber of the present invention;

[0029] Figure 5 yes Figure 4 Schematic diagram of the middle cylinder structure;

[0030] Figure 6 This is a schematic diagram of the burner structure in this invention;

[0031] Figure 7 This is a schematic diagram of the dual-fuel gas turbine control system of the present invention;

[0032] Figure 8 This is a schematic diagram of the synthesis gas fuel adjustment stage and the fuel dynamic switching stage of the present invention;

[0033] Figure 9 This is a flowchart illustrating the dynamic switching process of converting natural gas to syngas according to the present invention.

[0034] Figure 10 This is a graph showing the fuel switching process during a startup of the unit according to the present invention.

[0035] In the diagram: 1. Gas compressor; 2. Speed-increasing gearbox; 3. Generator; 4. Compressor; 5. Gas turbine; 6. Combustion chamber A; 7. Combustion chamber B; 8. Diffuser line; 9. Syngas line; 10. Standby gas line; 11. Inclined cyclone; 12. Syngas cyclone after; 13. Central axial cyclone; 14. Cooling center nozzle; 15. Combustion air inlet; 16. Natural gas fuel system; 17. Syngas fuel system; 18. Syngas control valve assembly; 19. Natural gas control valve; 20. Flare; 180. Syngas shut-off valve assembly; 21. Burner assembly; 22. Flame detection port; 23. Mixing cylinder; 24. Brick; 25. Air bypass; 26. Support; 27. Inner cylinder; 28. Manhole; 29. ​​Detection pipe; 30. Guide block; 31. Flame tube; 32. Natural gas emergency shut-off valve; 33. Natural gas vent valve; 34. Pre-filter; 35. Natural gas ball valve; 36. Syngas vent valve. Detailed Implementation

[0036] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0038] The following reference Figures 1-10 The technical solutions of some embodiments of the present invention are described below.

[0039] Example 1

[0040] This invention provides an embodiment of a fully automatic control strategy for dual-fuel switching in a gas turbine generator set. The fully automatic control system for dual-fuel switching in a gas turbine generator set includes, for example... Figure 1 As shown, Figure 1 This is a shaft arrangement diagram of the gas turbine generator set of the present invention. The gas turbine generator set of the present invention adopts a single-shaft arrangement, and the equipment coaxially connected to the gas turbine 5 includes a compressor 4, a generator 3, a speed-increasing gearbox 2, and a gas compressor 1. Specifically, one end of the generator 3's shaft is connected to the gas turbine 5 via a rigid coupling, and the other end of the generator 3's shaft is connected to the speed-increasing gearbox 2 via a flexible coupling. The gas compressor 1 is connected to one end of the speed-increasing gearbox 2 via a rigid coupling.

[0041] The gas turbine 5 selected in the gas turbine generator set of this invention is the AE94.2KS single-shaft heavy-duty gas turbine manufactured by Shanghai Electric using technology imported from Ansaldo, Italy. Gas turbine 5 comprises an 18-stage axial compressor and a 4-stage axial turbine, employing cold-end drive and cylindrical combustion chambers. External air enters compressor 4 through the intake system, and after compression, it enters the burners at the top of each cylindrical combustion chamber of gas turbine 5. Two cylindrical combustion chambers of gas turbine 5 are arranged vertically and symmetrically on both sides of gas turbine 5, each equipped with eight burners. The burners use dual-fuel nozzles; natural gas or coal gas is pressurized separately and then enters the combustion chamber for combustion via pressure regulating valves. The two cylindrical combustion chambers are combustion chamber A6 and combustion chamber B7. Combustion chambers A6 and B7 are two gas-to-gas dual-fuel combustion chambers arranged perpendicular to gas turbine 5, capable of independently burning one type of fuel or mixing two fuels within the same combustion chamber. Each cylindrical combustion chamber is lined with a refractory lining and is equipped with eight separate burners, such as... Figure 4 and Figure 5 As shown, Figure 4 This is a schematic diagram of the cylindrical combustion chamber of the present invention. Figure 5 yes Figure 4 Schematic diagram of the middle cylinder section. Air passes through the compressor and is heated to the turbine inlet temperature in the combustion chamber. The cylinder section structure includes: burner assembly 21, flame detection port 22, mixing cylinder 23, bearing block 24, air bypass 25, support 26, inner cylinder 27, manhole 28, detection tube 29, guide block 30, and flame tube 31.

[0042] The burner has three different fuel gas nozzle piping systems: diffuser piping 8, syngas piping 9, and standby gas piping 10 (optional). Figure 6 As shown, Figure 6 This is a schematic diagram of the burner structure in this invention. The diffuser line 8 is used for start-up (minimum fuel quantity for ignition), acceleration to rated speed, and partial load operation until load switching; the standby gas line 10 is a fuel line, which can be used to promote burner operation. The syngas line 9 is used to burn the syngas from the load switch to the base load. The syngas flow passes through the syngas cyclone separator 12 and enters the combustion chamber, where it mixes with the combustion air and burns. Air is supplied to the burner through the combustion air inlet 15 via the oblique cyclone separator 11 and the central axial cyclone separator 13. A small amount of combustion air enters the internal air passage and enters the combustion chamber through the central axial cyclone separator 13; a smaller portion of the combustion air is used to cool the central nozzle 14, and the remaining combustion air flows through the oblique cyclone separator 11.

[0043] The gas turbine 5 of this invention adopts a dual-fuel system, including a natural gas fuel system 16 and a syngas fuel system 17.

[0044] (1) Natural gas fuel system.

[0045] like Figure 2 As shown, Figure 2 This is a schematic diagram of the natural gas fuel system of the present invention. The natural gas fuel system 16 uses natural gas as the ignition fuel for the gas turbine. This system controls the mass flow rate of natural gas entering the gas turbine combustion chamber and, under certain conditions, prevents natural gas from entering the gas turbine. The system mainly consists of a pre-filter module, a natural gas emergency shut-off valve 32, a natural gas vent valve 33, a natural gas control valve 19, and a natural gas ball valve 35. The pre-filter 34 is used to prevent any coarse foreign matter in the pipeline between the upstream fine filter unit and the filter from entering the natural gas emergency shut-off valve. The natural gas emergency shut-off valve 32 supplies or cuts off the natural gas entering the combustor during gas turbine startup and shutdown, and during natural gas system startup or shutdown. After the natural gas emergency shut-off valve 32, the gas supply pipeline splits into two branches: one leads to the syngas system (blending pipeline), and the other directly enters the combustion chamber through the diffusion burner. The vent valve must be positioned between the first shut-off valve, i.e., the natural gas emergency shut-off valve 32, and the second shut-off valve, i.e., the natural gas control valve 19, to release the natural gas in the pipeline section between the shut-off valves into the air. Natural gas control valve 19 controls the flow rate of natural gas supplied to the diffusion burner according to the requirements of the gas turbine control system. Each pipeline leading to the combustion chamber is equipped with a shut-off ball valve, i.e., a natural gas ball valve 35, which has the function of supplying or cutting off the flow of natural gas to the burner.

[0046] (2) Syngas fuel system.

[0047] like Figure 3 As shown, Figure 3 This is a schematic diagram of the syngas fuel system of the present invention. The syngas fuel system 17 controls the mass flow rate of syngas entering the gas turbine combustion chamber and cuts off the syngas supply to the gas turbine under specific conditions. Syngas from the coal compressor outlet has two paths: one to the flare 20 for adjusting the syngas calorific value, and the other to the burner. After passing through the filter outlet, it connects to two branch lines each for combustion chambers A6 and B7. The burner branch lines are equipped with a syngas shut-off valve assembly 180, including a syngas emergency shut-off valve, a syngas vent valve 36, and a syngas control valve. The specific conditions refer to gas turbine protection activation or emergency shutdown.

[0048] The gas turbine 5 of this invention employs a dual-fuel gas turbine control system. The control system of the gas turbine 5 mainly consists of a sequential control system, a regulation control system, a protection system, and a power supply system. The regulation control system includes a main control system, an IGV control system, and a fuel control system. The main control system of this gas turbine uses a digital control system integrated into a redundantly configured control system for regulation and control. This system mainly includes the following controllers: speed controller, load controller, exhaust temperature controller, compressor pressure ratio limit controller, compressor pressure limiter, and exhaust temperature limiter, such as... Figure 7 As shown. The main control system is the core control system of the gas turbine. From the gas turbine ignition to the load operation stage, it realizes the flow and position control of natural gas or syngas through minimum value selection logic.

[0049] During gas turbine startup, the speed-up controller controls the turbine speed to eventually reach the rated speed or synchronous speed. The load controller takes over turbine control during the synchronization to base load phase, adjusting the load to the selected target value. The exhaust temperature controller uses the exhaust temperature correction value as the controlled variable of the exhaust temperature regulator, indirectly adjusting the fuel quantity and controlling the turbine outlet temperature in real time. The compressor pressure ratio limit controller, compressor pressure limiter, and exhaust temperature limiter serve as constraints for gas turbine control, ensuring safe and stable operation of the gas turbine.

[0050] The gas turbine 5 employs a dual-fuel gas turbine control system for dual-fuel switching. From ignition, speed increase, speed maintenance, grid connection to the fuel switching load point, approximately 40%-50% of the time, the gas turbine 5 uses natural gas as fuel. After being pressurized to a predetermined pressure by a booster, the natural gas passes through a pre-filter and enters the combustion chamber via the natural gas fuel passage through the natural gas control valve. During this stage, the syngas fuel passage and other valves are closed. To avoid unstable combustion or flameout at low loads, the unit load must reach a certain initial load before fuel switching can occur. While ensuring relatively stable parameters during fuel switching, the fuel switching time should be minimized to reduce natural gas consumption and improve the unit's start-up economy.

[0051] like Figure 8 As shown, Figure 8 This is a schematic diagram of the syngas fuel adjustment stage and the dynamic fuel switching stage of this invention. Dual-fuel switching must be manually initiated by operators after confirming that the fuel supply parameters, including calorific value, pressure, and temperature, meet the requirements, and then by selecting a one-button switch. The following analysis uses the natural gas to syngas switching process as an example. The entire switching process is divided into two stages: the syngas fuel adjustment stage and the dynamic fuel switching stage, as follows... Figure 8 As shown. In the first stage, the calorific value of the syngas is adjusted through flare discharge. In the second stage, after the calorific value, temperature, and stress of the syngas meet the switching requirements, the operator manually selects a one-button switch, and the dynamic switching phase begins. The dynamic switching process is as follows: Figure 9 As shown, Figure 9 This is a flowchart illustrating the dynamic switching process of converting natural gas to syngas according to the present invention.

[0052] Example 2

[0053] This invention provides another embodiment, which is a fully automatic control strategy for dual-fuel switching of a gas turbine generator set. The dual-fuel switching control strategy for the gas turbine 5 described in this invention includes the following steps:

[0054] Step 1. Control strategies before and after fuel switching.

[0055] (1) Control strategy during the initial switching phase: It should be checked and confirmed that the syngas pressure, temperature, and calorific value at the coal press outlet have reached the set values, and the unit load is within the 40%-50% load range for fuel switching. Due to factors such as low fuel flow rate, fluctuating fuel calorific value, and large nonlinearity of the control valve at low valve positions during the initial fuel switching phase, the control valve may have difficulty accurately controlling the fuel flow rate at low flow rates, which can easily lead to large fluctuations in the dynamic pressure of the combustion chamber and buzzing noises during the initial switching phase. Therefore, before switching, the four syngas control valves on both sides should be opened to approximately 10% of their maximum nonlinear valve positions at the maximum opening rate. During the rapid opening phase of the syngas control valves, the unit load is regulated by the natural gas control valve through a closed-loop control. After the dynamic pressure of the combustion chamber and the outlet temperature stabilize, the two fuel switching operations can begin to ensure stable combustion operation of the unit.

[0056] (2) Control strategy at the end of the switching phase: When the natural gas flow control valve gradually closes to about 10% of the maximum nonlinear valve position, the natural gas flow control valve closes rapidly at the maximum closing rate. At this time, the four syngas flow control valves are controlled in a closed loop by the load controller, and the valve positions gradually increase, so that the fuel quantity is rapidly increased, ensuring stable control of the unit load. At the same time, the syngas to flare valve should close rapidly at a certain rate, so that all the syngas enters the gas turbine for combustion.

[0057] Step 2. Analysis of dual-fuel switching control strategy.

[0058] (1) Once the two fuels meet the switching conditions, the flow ratio between the two fuels will begin to change at a specified slope. The natural gas flow ratio will decrease from 100% to 0% at a set rate, and the syngas flow ratio will increase from 0% to 100% at a set rate. The change rate of the two fuels should be selected with the unit load stability and switching time as performance indicators to prevent the change rate from being too large, which could lead to large fluctuations in unit load or even unstable combustion.

[0059] (2) The synthesis gas to the flare release valve is gradually closed at a certain rate of 5% / s, and the pressure at the coal press outlet is maintained at about 18 bar through the recirculation regulating valve.

[0060] (3) During the switching process, the closed-loop control of combustion chamber performance is the determining factor affecting the actual time of fuel switching and load stability. Its closed-loop control mainly includes load controller, exhaust temperature (TETC) controller and compressor pressure limit.

[0061] (4) Combustion Stability Closed-Loop Control: The stability of combustion in the gas turbine is determined by measuring the dynamic pressure changes within the combustion chamber (i.e., humming) and the dynamic amplitude changes of combustion-generated oscillations (i.e., combustion chamber vibration acceleration, ACC). Humming and acceleration are the main performance indicators reflecting the stability of combustion in the combustion chamber. Humming is measured by a dynamic pressure sensor at the edge of the burner nozzle to detect pressure fluctuations within the combustion chamber, while ACC is measured by a piezoelectric sensor mounted on the outer wall of the cylinder within the combustion chamber to detect the dynamic vibration velocity of the combustion chamber. Combustion stability closed-loop control uses humming and ACC as performance indicators and adjusts the combustion state dynamically in real time according to a pre-set adjustment curve. When combustion is unstable, humming and acceleration are used to detect the instability in real time. Before combustion deteriorates, the gas turbine exhaust temperature setpoint, IGV opening, and natural gas flow are automatically adjusted to ensure that all parameters of the unit are adjusted to the optimal state during fuel switching.

[0062] Example 3

[0063] This invention provides another embodiment, which is a fully automatic control strategy for dual-fuel switching of a gas turbine generator set. For example... Figure 10 As shown, Figure 10 This is a graph showing the fuel switching process during a certain startup of the unit.

[0064] The present invention provides an experimental analysis of dual-fuel switching as follows:

[0065] (1) Experimental data and curves.

[0066] like Figure 10 As shown, Figure 10 This is a graph showing the fuel switching process during a unit startup. Table 1 shows a comparison of the switching data.

[0067] Table 1 Comparison of Dual-Fuel Switching Data

[0068]

[0069] (2) Analysis of experimental results.

[0070] From Table 1 and Figure 10 It can be seen that during the dual-fuel switchover, the unit load gradually and smoothly fluctuated between 46 and 48%, taking 5 minutes and 26 seconds. After the switchover began, the syngas control valve quickly opened to 10%, and then gradually opened at the set rate. The natural gas control valve gradually closed to maintain load stability. No vibration was observed in the natural gas and syngas control valves during the switchover process, indicating a smooth transition.

[0071] In summary, multiple switching tests have demonstrated that the dual-fuel one-button switching control strategy proposed in this invention dynamically changes the flow rates of the two fuels according to a pre-set rate. Simultaneously, it considers external factors, including changes in syngas calorific value and compressor inlet temperature, and enhances combustion stability closed-loop control, achieving both speed and stability during dual-fuel switching. This invention's control strategy provides fully automatic control throughout the initial, final, and subsequent switching phases, ensuring rapid and stable control of various unit parameters, shortening fuel switching time, reducing natural gas consumption, and improving unit start-up economy.

[0072] In this invention, the terms "connection" and "fixation" should be interpreted broadly. For example, "connection" can mean a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of these terms in this invention according to the specific circumstances.

[0073] In the description of this invention, it should be understood that the indicated orientation or positional relationship is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description, and is not intended to indicate or imply that the device or unit referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0074] In the description of this specification, the terms "one embodiment," "some embodiments," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fully automatic control strategy for dual-fuel switching of gas turbine generator sets, characterized by: Includes the following steps: Step 1. Control strategy before and after fuel switching: In the initial stage of switching, first check and confirm whether the various indicators at the coal compressor outlet have reached the set values, and the unit load is in the load range of 40%-50% during fuel switching; In the final stage of switching, when the natural gas flow control valve gradually closes to the maximum nonlinear valve position of 10%, the natural gas flow control valve closes rapidly at the maximum closing rate; At the same time, the syngas to flare valve is closed, so that all the syngas enters the gas turbine for combustion; The various indicators at the coal compressor outlet include: syngas pressure, temperature and calorific value; Step 2. Dual-fuel switching control strategy: When the two fuels meet the switching conditions, the natural gas flow rate decreases from 100% to 0% at a set rate, while the syngas flow rate increases from 0% to 100% at a set rate; the syngas to the flare release valve gradually closes at a rate of 5% / s, and the coal compressor outlet maintains a pressure of 18 bar through the recirculation regulating valve; during the switching process, closed-loop control of combustion chamber performance and closed-loop control of combustion stability are performed; the closed-loop control of combustion chamber performance includes: load controller, exhaust temperature controller, and compressor pressure limit; The combustion stability closed-loop control includes determining whether the gas turbine is burning stably by measuring the dynamic pressure changes in the combustion chamber and the dynamic amplitude changes of the oscillations generated by combustion. The combustion stability closed-loop control uses humming and ACC as performance indicators and adjusts the combustion state in real time according to a pre-set adjustment curve. When combustion is unstable, the humming and acceleration are used to reflect the combustion instability in real time. Before the combustion deteriorates, the gas turbine exhaust temperature setpoint, IGV opening degree and natural gas flow are automatically adjusted to ensure that the unit parameters are adjusted to the optimal state during fuel switching.

2. The fully automatic dual-fuel switching control strategy for gas turbine generator sets according to claim 1, characterized in that: The dual-fuel switching control strategy includes a natural gas fuel system and a syngas fuel system.

3. The fully automatic dual-fuel switching control strategy for gas turbine generator sets according to claim 2, characterized in that: The natural gas fuel system uses natural gas as the ignition fuel for the gas turbine, controls the mass flow rate of natural gas entering the gas turbine combustion chamber, and prevents natural gas from entering the gas turbine under specific conditions. The system consists of a pre-filter module, a natural gas emergency shut-off valve, a natural gas vent valve, a natural gas control valve, and a natural gas ball valve. The pre-filter is used to prevent any coarse foreign objects in the pipeline between the upstream fine filter unit and the filter from entering the natural gas emergency shut-off valve. The natural gas emergency shut-off valve supplies or cuts off the natural gas entering the burner during gas turbine startup and shutdown, as well as during natural gas system startup or shutdown. After the natural gas emergency shut-off valve, the gas supply pipeline splits into two branches: one leads to the syngas system, and the other goes directly into the combustion chamber through the diffusion burner. A vent valve is placed between the natural gas emergency shut-off valve and the natural gas control valve to release the natural gas in the pipeline section between the shut-off valves into the air. The natural gas control valve controls the flow of natural gas supplied to the diffusion burner according to the requirements of the gas turbine control system. Each pipeline leading to the combustion chamber is equipped with a natural gas ball valve to supply or cut off the flow of natural gas to the burner.

4. The fully automatic dual-fuel switching control strategy for gas turbine generator sets according to claim 2, characterized in that: The syngas fuel system controls the mass flow rate of syngas entering the gas turbine combustion chamber and cuts off the syngas supply to the gas turbine under the condition of gas turbine protection action or emergency shutdown; the syngas from the coal compressor outlet has one path leading to the flare for adjusting the syngas calorific value, and the other path leading to the burner. After passing through the filter outlet, it connects to two branch pipelines for combustion chamber A and combustion chamber B respectively. The burner branch pipeline is equipped with a syngas shut-off valve group, including: a syngas emergency shut-off valve, a syngas vent valve, and a syngas control valve.

5. The fully automatic dual-fuel switching control strategy for gas turbine generator sets according to claim 4, characterized in that: The burner has three different fuel gas nozzle piping systems, including: a diffuser piping, a syngas piping, and a standby gas piping; the diffuser piping is used for starting with minimum fuel quantity, accelerating to rated speed, and operating under partial load until load switching; the standby gas piping is a fuel line used to promote burner operation; the syngas piping is used to burn the syngas from load switching to base load; the syngas flow passes through a syngas cyclone separator and enters the combustion chamber, where it mixes with and burns with combustion air. Air is supplied to the burner through the combustion air inlet via an oblique cyclone separator and a central axial cyclone separator; a small amount of combustion air enters the internal air passage and enters the combustion chamber through the central axial cyclone separator; a smaller portion of the combustion air is used to cool the central nozzle, and the remaining combustion air flows through the oblique cyclone separator.

6. The fully automatic dual-fuel switching control strategy for gas turbine generator sets according to claim 1, characterized in that: The gas turbine adopts a dual-fuel gas turbine control system for dual-fuel switching during operation. From ignition, speed increase, speed maintenance, grid connection to the fuel switching load point of 40%-50%, natural gas is used as fuel. After being pressurized to a predetermined pressure by a booster, the natural gas passes through a pre-filter and enters the combustion chamber through the natural gas fuel passage via the natural gas control valve. During this stage, the syngas fuel passage and other valves are closed; once the unit load reaches a certain initial load, the fuel is quickly switched.

7. The fully automatic dual-fuel switching control strategy for gas turbine generator sets according to claim 6, characterized in that: The dual-fuel switching must be carried out after confirming that the fuel supply parameters, including calorific value, pressure and temperature, meet the requirements; the switching process includes two stages: the syngas fuel adjustment stage and the fuel dynamic switching stage. Syngas fuel conditioning stage: Adjusting the calorific value of syngas through flare release; Dynamic fuel switching phase: Once the calorific value, temperature and stress of the syngas meet the switching requirements, select one-click switching, and the dynamic switching phase will begin.

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