Full-process unmanned start-stop system for gas combined cycle unit and control method thereof

Abstract

The present application relates to the field of gas combined cycle unit, for solving the bypass system mode of conventional control system is single, the linkage between each module is insufficient and the fuel consumption and working medium loss is larger in the process of starting and stopping problem, specifically is gas combined cycle unit whole process unmanned starting and stopping system and control method thereof, in the present application, the integrated starting and stopping control architecture of machine, furnace and electricity is constructed, six different control modes are given to high and medium pressure bypass valve of steam turbine, full-automatic pressure matching from boiler steam production to steam turbine is realized, the automation level and operation safety of starting and stopping process are significantly improved, and the logic of sequence control is also used, the water injection and automatic starting of closed water system are completed, the preparation and starting time of system is shortened, through multiple breakpoint design when stopping, the effects of avoiding steam turbine water impact, relieving steam drum deformation caused by too large temperature difference of upper and lower walls of high / medium / low pressure steam drum and shortening the response speed of next starting can be achieved.

Description

Technical Field

[0001] This invention relates to the field of gas-fired combined cycle units, specifically to a fully automated start-up and shutdown system and control method for gas-fired combined cycle units. Background Technology

[0002] A combined cycle gas turbine unit is a high-efficiency power generation system that combines a gas turbine and a steam turbine. Through energy cascade utilization, its thermal efficiency is much higher than that of a traditional coal-fired power plant. The specific working principle and process are as follows; Gas turbine cycle: After air is compressed by the compressor, it is mixed and burned with natural gas in the combustion chamber to produce high-temperature and high-pressure gas, which drives the gas turbine blades to rotate and drives the generator to generate electricity; Waste heat recovery: The high-temperature exhaust gas from the gas turbine enters the waste heat boiler to heat the feedwater and generate high-temperature and high-pressure steam; Steam turbine cycle: High-temperature and high-pressure steam enters the steam turbine, expands and does work, and then drives the generator to generate electricity; Condensation and Circulation: The exhaust steam from the turbine is condensed into water in the condenser, and after being pressurized by the feedwater pump, it is sent back to the waste heat boiler to complete the circulation.

[0003] Currently, the start-up and shutdown control of gas combined cycle units mainly relies on distributed control systems and the experience and judgment of operators. During the start-up and shutdown process, it involves the coordinated operation of multiple complex subsystems such as gas turbine speed, load control, bypass system mode switching, turbine thermal stress monitoring, and waste heat boiler water circulation regulation. Traditional technologies usually adopt discrete control logic, and the linkage between modules is insufficient, making it impossible to achieve unmanned start-up and shutdown control.

[0004] To address the aforementioned technical problems, this invention proposes a solution. Summary of the Invention

[0005] This invention addresses the problems of conventional control systems, such as the single bypass system mode, insufficient inter-module linkage, and significant fuel consumption and working fluid loss during start-up and shutdown. It proposes a fully unmanned start-up and shutdown system and control method for gas combined cycle units.

[0006] The objective of this invention can be achieved through the following technical solution: a fully unmanned start-up and shutdown system for a gas-fired combined cycle unit, including a main control module for the gas-fired combined cycle unit, a bypass control module, a bypass quick-opening and quick-closing management module, a closed-loop water control module, and a shutdown management module; The main control module of the gas combined cycle unit is used to monitor the operation of the gas turbine and steam turbine, and to obtain the operating parameters of the steam turbine side and the operating parameters of the gas turbine side. The bypass control module is used to switch and execute different operating modes of the medium-pressure bypass valve and the high-pressure bypass valve of the gas combined cycle unit; The bypass quick-opening and quick-closing control module is used to monitor the parameters of the gas combined cycle unit in real time, and to make a feasibility judgment based on the monitored parameters, and control the quick-closing and quick-opening actions of the high-pressure bypass valve. The closed-loop water control module can provide cooling water to the auxiliary equipment of the gas combined cycle unit through the closed-loop water system and realize the sequential control of cooling water injection. The shutdown control module is used to set four breakpoints when the gas combined cycle unit is shut down, and to control the gas combined cycle unit according to different breakpoints; The pressure, temperature, duration, and load settings described in this invention are preferred values ​​for a 487MW gas-fired steam combined cycle cogeneration unit engineering example. Other capacity units can be adjusted proportionally according to the unit characteristics, and the specific values ​​can be adjusted adaptively according to the actual requirements of the engineering example.

[0007] As a preferred embodiment of the present invention, the parameters of the gas combined cycle unit collected by the main control module of the gas combined cycle unit include at least: intermediate pressure bypass control mode, condenser vacuum degree, turbine-side reheat steam pressure, turbine-side grid connection parameters, intermediate pressure bypass valve opening degree, turbine main transformer high-pressure side circuit breaker status, turbine-side high-pressure steam pressure, high-pressure bypass valve opening degree, high-pressure bypass control mode, and gas turbine flame detection signal.

[0008] In a preferred embodiment of the present invention, the bypass control module is used to switch the operating modes of the medium-pressure bypass valve and the high-pressure bypass valve of the gas combined cycle unit. The high-pressure bypass valve and the medium-pressure bypass valve are each equipped with six automatically switching control modes: minimum opening mode, minimum pressure mode, pressure boosting mode, constant pressure mode, tracking mode, and shutdown constant pressure mode; the bypass control module automatically switches between the control modes according to the operating parameters of the gas combined cycle unit.

[0009] In a preferred embodiment of the present invention, the conditions for the bypass control module to switch the medium-pressure bypass valve mode are as follows: Conditions for entering minimum opening mode: the gas turbine has been ignited, the reheat steam pressure on the turbine side is greater than the set value and the intermediate bypass is automatically activated, or the gas turbine has been ignited for the set time and the condenser vacuum has reached the set value and the intermediate bypass is automatically activated. Conditions for entering minimum pressure mode: The bypass is in minimum opening mode and the reheat steam pressure on the turbine side is greater than the set value; Conditions for entering boost mode: The bypass is in minimum pressure mode and the opening of the bypass is greater than the set value; Conditions for entering constant pressure mode: The intermediate bypass is in boost mode and the reheat steam pressure on the turbine side is greater than the set value; Conditions for entering tracking mode: the bypass is in constant pressure mode, the turbine is connected to the grid, and the bypass opening is less than the set value; The conditions for entering the shutdown and pressure regulation mode are: the turbine has been shut down, or the high-voltage side circuit breaker of the turbine main transformer has been tripped, or the turbine shutdown and pressure regulation mode is executed by the turbine shutdown control or the bypass shutdown and pressure regulation mode is manually activated. The conditions for the bypass control module to switch the high-pressure bypass valve mode are as follows: The conditions for entering the minimum opening mode are: the gas turbine is ignited, the high-pressure steam pressure on the turbine side is greater than the set value and the intermediate bypass is automatically activated, or the gas turbine is ignited, the condenser vacuum is less than the set value and the intermediate bypass is automatically activated. Conditions for entering minimum pressure mode: The high-pressure bypass is in minimum opening mode and the high-pressure steam pressure on the turbine side is greater than the set value; Conditions for entering boost mode: The high-pressure bypass is in minimum pressure mode and the opening of the high-pressure bypass is greater than the set value; Conditions for entering constant pressure mode: The high-pressure bypass is in boost mode and the high-pressure main steam pressure is greater than the starting pressure; Conditions for entering tracking mode: The high-pressure bypass is in constant pressure mode, the turbine is connected to the grid, and the high-pressure bypass opening is less than the set value; Conditions for entering the shutdown and pressure regulation mode: The turbine has been shut down, or the high-voltage side circuit breaker of the turbine main transformer has been tripped, or the turbine shutdown control is executing the shutdown and pressure regulation mode, or the bypass shutdown and pressure regulation mode is manually activated.

[0010] In a preferred embodiment of the present invention, the conditions under which the bypass quick-opening and quick-closing control module controls the high-pressure bypass valve to close quickly are any one of the following: The steam pressure after the high-pressure bypass valve is greater than the preset value; the steam temperature after the high-pressure bypass valve is greater than the preset temperature; the intermediate bypass quick-closing is triggered, and the high-pressure bypass quick-closing is triggered at the same time; The conditions for the bypass quick-opening and quick-closing control module to control the high-pressure bypass valve to open quickly are: turbine tripping or turbine generator disconnection; The conditions for quick opening of the high-pressure bypass valve are: no quick closing conditions, steam pressure after the high-pressure bypass valve is less than the set pressure, steam temperature after the high-pressure bypass valve is less than the set temperature, and turbine load is greater than the set value for a certain period of time.

[0011] As a preferred embodiment of the present invention, the method for sequential water injection control by the closed-loop water control module is as follows: S1: Determine whether the closed water system meets the preset water injection conditions. If the conditions are met, proceed to the next step. S2: The electric valves, regulating valves, and bypass valves of the closed water system are in the fully open state; S3: Open the demineralized water supply valve of the high-level expansion tank to start injecting water into the closed water system from the high-level expansion tank; S4: After manually confirming that all air has been expelled from the closed water system, stop water injection and close the electric valve at the outlet of the closed water pump.

[0012] In a preferred embodiment of the present invention, the closed-loop water system controlled by the closed-loop water control module further includes a first standby closed-loop water pump and a second standby closed-loop water pump, and both are set with the same standby pump start-up value. When the pressure of the closed-loop water system drops to the standby pump start-up value, the standby closed-loop water pump is activated. The specific activation method is as follows: A1: Obtain the first and second standby closed-loop water pumps that have been manually set in advance. A2: Determine whether the closed water system meets the start-up requirements; A3: Set the closed-loop water system valves to the start position; A4: Start the first standby closed-loop water pump; A5: If the pressure of the closed water system is still lower than the joint start value when the first standby closed water pump starts up after the preset delay, the second standby closed water pump will be started automatically.

[0013] As a preferred embodiment of the present invention, the four breakpoints set by the shutdown control module include the unit load reduction breakpoint, the unit tripping breakpoint, the waste heat boiler stop breakpoint, and the unit shutdown breakpoint. The main steps for the unit load reduction breakpoint are: exiting automatic generation control, activating automatic high, medium, and low pressure bypasses, reducing the unit load to the set load, exiting the coordinated control system mode of the unit's gas combined cycle unit, and activating automatic shaft seals. The main steps for tripping the unit are: manually confirming that the auxiliary steam conditions are met, then initiating the turbine shutdown procedure; reducing the gas turbine load to the set low load; and requesting the gas turbine to be shut down by the distributed control system. The main steps for stopping the waste heat boiler are: automatically desuperheating water of the waste heat boiler, completely stop the high / medium pressure feedwater pumps, stop the steam drum water supply, close the drain valve, start the low-efficiency recirculation system stop function group, and put the condensate pump into standby mode. The main steps for shutting down the unit are: closing the outlet damper of the waste heat boiler chimney, starting the vacuum system stop function group, starting the shaft seal system stop function group, and starting the condensate system stop function group.

[0014] Additionally, this invention also proposes a fully unmanned start-up and shutdown control method for gas-fired combined cycle units, comprising the following steps: Step 1: Closed-loop water operation monitoring, automatic water injection, and automatic activation of backup water pumps; Step 2: Control the combined cycle gas turbine unit to complete the start-up and grid connection of the gas turbine; Step 3: During the start-up and shutdown of the gas combined cycle unit, automatically switch the operating modes of the medium-pressure bypass and the high-pressure bypass; Step 4: Monitor the operation of the high-pressure bypass valve and control its rapid closing or opening action; Step 5: Complete the shutdown of the gas combined cycle unit step by step through four breakpoints.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. In this invention, an integrated start-stop control architecture for the machine, boiler, and electricity is constructed. The bypass control module assigns six different control modes to the high and medium pressure bypass valves of the steam turbine according to the ignition of the gas turbine and the grid connection status of the steam turbine: minimum opening mode, minimum pressure mode, pressure boosting mode, constant pressure mode, tracking mode, and shutdown constant pressure mode. Moreover, no manual intervention is required for valve position setting, realizing fully automatic pressure matching from boiler steam production to steam turbine start-up, significantly improving the automation level and operational safety of the start-stop process.

[0016] 2. In this invention, sequential control logic is used to complete the water injection and automatic start-up of the closed-loop water system. The sequential logic is used for automatic control from the very beginning of the system water injection, eliminating the need for tedious manual inspection and verification of valves one by one, greatly reducing the workload of operators and shortening the system preparation and start-up time. At the same time, by setting a first standby and a second standby closed-loop water pump, the unit can operate only one closed-loop water pump when the water demand is not high, saving electricity. Meanwhile, the closed-loop water system can also automatically start the first standby closed-loop water pump and start the second standby closed-loop water pump after a delay according to the increase in closed-loop water demand, ensuring the safety of the unit.

[0017] 3. This invention also incorporates multiple interruption points during shutdown to ensure that the auxiliary steam for the unit is stably supplied by the adjacent unit or the starting boiler before the turbine is shut down. This prevents a sudden drop in the exhaust temperature of the gas turbine from causing a sudden drop in the temperature of the main steam entering the turbine, which could lead to insufficient superheat of the main steam and the risk of water hammer in the turbine due to moisture carried by the steam during the power operation process. By using the waste heat boiler to stop interruption points, the high, medium, and low pressure steam drums are ensured to be filled with water to the high water level before the high pressure feedwater pump and the medium pressure feedwater pump are shut down. This alleviates the problem of excessive temperature difference between the upper and lower walls of the high, medium, and low pressure steam drums, which could cause deformation of the steam drums. By using the unit shutdown interruption points, the shaft seal and vacuum system can be kept running after the unit is shut down, which can significantly shorten the response speed of the next startup and enable the unit to start up quickly when the power grid needs it. Attached Figure Description

[0018] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0019] Figure 1 This is a system flowchart of the present invention; Figure 2 This is a system block diagram of the present invention; Figure 3 This is a schematic diagram of the closed-loop water system of the present invention; Figure 4 This is a diagram illustrating the closed-loop water injection control steps of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1: Please refer to Figure 1 - Figure 4 As shown, the fully automated start-up and shutdown system for the gas-fired combined cycle unit includes the main control module, bypass control module, bypass quick-opening and quick-closing control module, closed-loop water control module, and shutdown control module. In this embodiment, to make the control system logic more hierarchical and modular, and to facilitate unified scheduling and interface calls of various functional modules, a logic module is defined to implement the underlying logic functions of the system. This logic module is applied to the control of closed-loop water pump functional groups, circulating water pump functional groups, condensate pump functional groups, etc., thereby realizing unified scheduling and module collaboration for unmanned start-stop control throughout the entire process. Meanwhile, the function call logic module can also manually confirm and select different breakpoints to be executed, realizing the system's one-click call function.

[0022] The main control module of the gas turbine combined cycle unit is used to monitor the operation of the gas turbine and steam turbine, and to obtain the operating parameters of the steam turbine side and the gas turbine side. The parameters collected by the main control module of the gas turbine combined cycle unit include at least: intermediate pressure bypass control mode, condenser vacuum, turbine-side reheat steam pressure, turbine-side grid connection parameters, intermediate pressure bypass valve opening, turbine main transformer high-pressure side circuit breaker status, turbine-side high-pressure steam pressure, high-pressure bypass valve opening, high-pressure bypass control mode, and gas turbine flame detection signal.

[0023] The bypass control module is used to switch and execute different operating modes of the medium-pressure bypass valve and the high-pressure bypass valve of the gas combined cycle unit; The high-pressure bypass valve and the medium-pressure bypass valve are each equipped with six automatically switching control modes: minimum opening mode, minimum pressure mode, pressure boosting mode, constant pressure mode, tracking mode, and shutdown constant pressure mode; the bypass control module automatically switches between the control modes according to the operating parameters of the gas combined cycle unit. The different operating modes and their functions are as follows: Minimum Opening Mode: After the gas turbine ignites, the high-pressure main steam valve on the waste heat boiler side opens slowly. Once the high-pressure steam pressure on both sides of the turbine and waste heat boiler is basically balanced, the high-pressure bypass valve automatically engages. In automatic mode, after pressure buildup, the minimum valve position control takes effect, meaning the high-pressure bypass valve maintains a 10% opening to warm up the pipes and ensure steam flow. The purpose of this mode is to ensure a steam flow path on the turbine side after the waste heat boiler generates high-pressure steam and sends it to the turbine side. This warms up the high-pressure main steam pipes on the turbine side while preventing the high-pressure steam from rapidly increasing in pressure due to a lack of flow path.

[0024] Minimum pressure mode: In minimum valve mode, when the high-pressure bypass valve opening is at the minimum opening of 10% and the pressure in front of the high-pressure bypass valve reaches 1.2MPa, the high-pressure bypass valve switches to minimum pressure mode and switches to pressure control. The pressure setting value is 1.2MPa. As the high-pressure main steam pressure on the waste heat boiler side continues to rise, the high-pressure bypass valve gradually opens according to this fixed setting pressure.

[0025] Pressure Boosting Mode: The pressure boosting mode is activated after the high-pressure bypass opening reaches 20%. The high-pressure bypass pressure is increased using a sliding pressure control method (three-state rate). During the pressure boosting process, the high-pressure bypass regulating valve adjusts according to the pressure deviation. This mode ensures that the high-pressure main steam pressure on the turbine side increases at the set pressure boosting rate, thus controlling the turbine-side main steam pressure boosting rate. The sliding pressure control method uses different boosting rates depending on the turbine's cold, warm, and hot states: 0.181 MPa / min for cold state, 0.317 MPa / min for warm state, and 0.294 MPa / min for hot state. During the pressure boosting process, the high-pressure bypass regulating valve adjusts according to the pressure deviation until the turbine-side reheat steam pressure reaches the starting pressure of 8 MPa, at which point the high-pressure bypass valve enters a constant pressure mode.

[0026] Constant pressure mode: When the high-pressure main steam pressure on the turbine side rises to the start-up pressure of 8 MPa, the high-pressure bypass valve enters constant pressure mode, maintaining the start-up pressure while waiting for the turbine to start. After the turbine begins receiving steam for start-up, the high-pressure bypass valve continues to maintain the start-up pressure. Setting this mode ensures that the main steam pressure remains stable during turbine start-up, guaranteeing turbine safety during the start-up process.

[0027] Tracking Mode: When the DCS distributed control system receives the initial load signal from the turbine generator connected to the grid, the high-pressure bypass valve begins to close slowly at a certain rate. When the high-pressure bypass valve is closed to 5%, it enters tracking mode. At this time, the high-pressure bypass valve pressure setpoint = turbine-side high-pressure main steam pressure + 0.15 MPa, and the high-pressure bypass valve remains fully closed. The purpose of setting this mode is to ensure that after the turbine is connected to the grid and under load, the high-pressure bypass valve is fully closed, and all high-pressure steam enters the turbine to perform work.

[0028] Shutdown Pressure Regulating Mode: When the turbine trips, is disconnected, or is manually activated, the high-pressure bypass valve switches to shutdown pressure regulating mode, maintaining the current pressure for a certain period. After the delay, the parameters are automatically reset, and the pressure setpoint slides back to the high-pressure main steam start-up pressure of 8 MPa. The purpose of this mode is to ensure that when the turbine trips or begins shutdown, the high-pressure main steam pressure can first remain stable and then slowly release pressure, preventing a large amount of high-pressure steam from entering the condenser through the high-pressure bypass and then the intermediate-pressure bypass at the moment of turbine tripping, thus avoiding impact on the condenser.

[0029] The conditions for the bypass control module to switch the medium-pressure bypass valve mode are as follows: Conditions for entering minimum opening mode: gas turbine is ignited, turbine-side reheat steam pressure is greater than 0.05MPa, and intermediate bypass is automatic (the above conditions are AND), or gas turbine is ignited and delayed for 1200s, condenser vacuum is less than -50, and intermediate bypass is automatic (the above conditions are AND). Conditions for entering minimum pressure mode: The bypass is in minimum opening mode, and the reheat steam pressure on the turbine side is greater than 0.08 MPa (the above conditions are combined with). Conditions for entering boost mode: The bypass is in minimum pressure mode and the opening of the bypass is greater than 20% (the above conditions are the same as those for other modes). Conditions for entering constant pressure mode: the intermediate bypass is in boost mode and the reheat steam pressure on the turbine side is greater than 0.9 MPa (the above conditions are the same as above). Conditions for entering tracking mode: the bypass is in constant pressure mode, the turbine is connected to the grid, and the bypass opening is less than 5% (the above conditions are AND). The conditions for entering the shutdown and pressure regulation mode are: the turbine has been shut down, the high-voltage side circuit breaker of the turbine main transformer has been opened, the turbine shutdown and pressure regulation mode is executed by the turbine shutdown and pressure regulation control, or the bypass shutdown and pressure regulation mode is manually activated (the above conditions are either 'or'). The conditions for the bypass control module to switch the high-pressure bypass valve mode are as follows: The conditions for entering the minimum opening mode are: the gas turbine is ignited, the high-pressure steam pressure on the turbine side is greater than 0.1 MPa, and the intermediate bypass is automatic (the above conditions are AND) or the gas turbine is ignited, the condenser vacuum is <50, and the intermediate bypass is automatic (the above conditions are AND). Conditions for entering minimum pressure mode: The high-pressure bypass is in minimum opening mode, and the high-pressure steam pressure on the turbine side is greater than 1.2 MPa (the above conditions are combined with). Conditions for entering boost mode: The high-pressure bypass is in minimum pressure mode, and the opening of the high-pressure bypass is greater than 20% (the above conditions are combined with). Conditions for entering constant pressure mode: The high-pressure bypass is in pressure boosting mode, and the high-pressure main steam pressure is greater than the starting pressure (8MPa) (the above conditions are the same as above). Conditions for entering tracking mode: the high-pressure bypass is in constant pressure mode, the turbine is connected to the grid, and the high-pressure bypass opening is less than 5% (the above conditions are AND); Conditions for entering the shutdown and pressure regulation mode: The turbine has been shut down, the high-voltage side circuit breaker of the turbine main transformer has been opened, the turbine shutdown control is executing the shutdown and pressure regulation mode, or the bypass shutdown and pressure regulation mode is manually activated (the above conditions are either 'or'). The bypass quick-opening and quick-closing control module is used to monitor the parameters of the gas combined cycle unit in real time, and to make feasibility judgments based on the monitored parameters. It controls the quick-closing and quick-opening actions of the high-pressure bypass valve. The core purpose of the high-pressure bypass valve's quick-closing function is to protect the condenser and prevent it from overheating and overpressure. The core purpose of the quick-opening function is to prevent safety malfunctions or equipment damage caused by waste heat boiler overpressure during turbine tripping and disconnection. It also prevents the impact on the turbine caused by a sudden increase in the high-pressure main steam pressure on the turbine side.

[0030] The conditions for the bypass quick-opening and quick-closing control module to control the high-pressure bypass valve to close quickly are any of the following: The steam pressure after the high-pressure bypass valve is greater than 3.9 MPa; the steam temperature after the high-pressure bypass valve is greater than 404℃; the intermediate bypass quick-closing is triggered, and the high-pressure bypass quick-closing is triggered simultaneously. The conditions for the bypass quick-opening and quick-closing control module to control the high-pressure bypass valve to open quickly are: turbine tripping or turbine generator disconnection; The conditions for quick opening of the high-pressure bypass valve are: no quick closing conditions, steam pressure after the high-pressure bypass valve is less than 3.8 MPa, steam temperature after the high-pressure bypass valve is less than 374℃, turbine load is greater than 15MW and the delay is at least four seconds (4s) (the above conditions are the same as above).

[0031] The closed-loop water control module provides cooling water to the auxiliary equipment of a gas combined cycle unit through a closed-loop water system and enables sequential control of cooling water injection. The main function of the closed-loop water system is to provide a cooling water source for the unit's auxiliary equipment, ensuring the normal operation of the auxiliary equipment and system. The closed-loop water itself is typically cooled by an open-loop circulating water system. Users of the closed-loop water system generally include lubricating oil coolers, EH oil coolers, generator air coolers, mechanical seals of water pumps, and online steam and water sampling and monitoring devices. The basic flow of the closed-loop water system is: demineralized water or condensate → closed-loop water tank → closed-loop water pump → closed-loop water heat exchanger → closed-loop water user → closed-loop water pump inlet. The method for sequential water injection control using a closed-loop water control module is as follows: S1: Determine whether the closed water system meets the preset water injection conditions. If the conditions are met, proceed to the next step. S2: The electric valves, regulating valves, and bypass valves of the closed water system are in the fully open state; S3: Open the demineralized water supply valve of the high-level expansion tank to start injecting water into the closed water system from the high-level expansion tank; S4: After manually confirming that all air has been expelled from the closed water system, stop water injection, close the outlet electric valve of the closed water pump, and keep the user side open.

[0032] The closed-loop water control module also controls a first standby closed-loop water pump and a second standby closed-loop water pump, both of which are set with the same standby pump start-up value. When the pressure of the closed-loop water system drops to the standby pump start-up value, the standby closed-loop water pump is activated. The specific activation method is as follows: A1: Obtain the first and second standby closed-loop water pumps that are manually set in advance. The manual setting is to manually select the first standby and second standby closed-loop water pumps to be started first, based on the current status of the three closed-loop water pumps, and to pre-select the closed-loop water (cooling) heat exchanger to be put into operation. A2: Determine whether the closed water system meets the start-up requirements; A3: Set the closed-loop water system valves to the start position; A4: Start the first standby closed-loop water pump; A5: If the pressure of the closed water system is still lower than the joint start value when the first standby closed water pump starts up after the preset delay, the second standby closed water pump will be started automatically.

[0033] The closed-loop water pump has a first standby and a second standby. The two standby pumps have the same start-up value. The second standby pump has an added delay to trigger, allowing the unit to operate only one closed-loop water pump when the water demand is low, saving plant power. At the same time, the closed-loop water system can also automatically start the first standby closed-loop water pump when the closed-loop water system pressure drops to the standby pump start-up value, based on the increase in closed-loop water demand. If the closed-loop water system pressure is still lower than the start-up value when the delay time is reached, the second standby closed-loop water pump will be automatically started to ensure the safety of the unit.

[0034] The shutdown control module is used to set four breakpoints when the gas combined cycle unit is shut down, and to control the gas combined cycle unit according to different breakpoints. The four breakpoints set by the shutdown control module include unit load reduction breakpoint, unit tripping breakpoint, waste heat boiler stop breakpoint, and unit shutdown breakpoint. The main steps for the unit load reduction breakpoint are: exit AGC, activate automatic high, medium and low pressure bypass, reduce unit load to 200MW, exit unit CCS mode, and activate automatic shaft seal. The unit load is reduced to the minimum 200MW required for stable operation of the combined cycle through CCS coordinated control. Then, CCS control is disengaged, and the turbine and gas turbine are shut down sequentially via the unit's tripping points. This is because for combined cycle units of this capacity, as the total load continues to decrease from 200MW under CCS coordinated control, the exhaust temperature of the gas turbine drops sharply, leading to a sudden drop in the temperature of the main steam entering the turbine. This can result in insufficient superheat of the main steam, causing moisture to be carried over during operation, posing a risk of water hammer in the turbine.

[0035] The main steps for tripping the unit are as follows: after manually confirming that the auxiliary steam conditions are met, start the turbine shutdown procedure, reduce the gas turbine load to 60MW, and request the DCS to shut down the gas turbine (after disconnecting the gas turbine from the grid, the primary frequency regulation of the gas turbine is turned off). Because a stable supply of shaft seal steam is required during turbine shutdown, it is necessary to confirm that the unit's auxiliary steam is being stably supplied by adjacent units or the starting boiler before shutting down the turbine. Setting a tripping point allows the operating operator to manually confirm that the unit's auxiliary steam supply meets the requirements before initiating the turbine shutdown procedure, ensuring a safe turbine shutdown.

[0036] The main steps for stopping the waste heat boiler are: automatically desuperheating water of the waste heat boiler, completely stop the high / medium pressure feedwater pumps, stop the steam drum water supply, close the drain valve, start the low-efficiency recirculation system stop function group, and put the condensate pump into standby mode. Since the entire unit is shut down, to mitigate the risk of steam drum deformation due to excessive temperature differences between the upper and lower walls of the high / medium / low-pressure steam drums, it is necessary to ensure that the high / medium / low-pressure steam drums are filled with water to the high water level before shutting down the high-pressure and medium-pressure feedwater pumps. Setting a stop point for the waste heat boiler allows the operating operator to manually confirm that all three steam drums are at the high water level before initiating the procedure to shut down the high and medium-pressure feedwater pumps and stop the water filling of the three steam drums.

[0037] The main steps for shutting down the unit are: closing the outlet damper of the waste heat boiler chimney, starting the vacuum system stop function group, starting the shaft seal system stop function group, and starting the condensate system stop function group.

[0038] Since combined cycle gas turbine units typically operate on a two-shift system, they play a crucial role in peak-shaving power generation within the power system. Therefore, maintaining the shaft seals and vacuum system after a unit shutdown can significantly shorten the response time for the next startup, enabling the unit to be quickly started when the grid requires it. Setting a shutdown cutoff point allows operators to selectively execute this cutoff. During normal two-shift standby shutdowns, this cutoff point is not executed; it is only executed when the unit has a planned long-term shutdown exceeding 72 hours.

[0039] AGC stands for Automatic Generation Control, which is the core function of power system automation. It is used to adjust the active power of generator sets in real time to maintain grid frequency stability and ensure that power is exchanged on inter-regional tie lines as planned.

[0040] DCS is a distributed control system. Each unit is equipped with a distributed control system (DCS). The control system (TCS) supplied with the main gas turbine equipment and the control system (DEH) supplied with the main steam turbine equipment are connected to the DCS through communication interfaces and a small number of hardwired connections, forming a complete control system for centralized monitoring of the combined cycle unit. The control of the steam-water system, steam turbine bypass, waste heat boiler, condensate system, circulating water system, chemical sampling and dosing system, etc. are all realized by the DCS.

[0041] CCS stands for Coordinated Control System, which is a strategy that integrates the gas turbine, waste heat boiler, and steam turbine as a whole for unified control. It aims to achieve safe, stable, and efficient operation of the unit and rapid response to grid load commands.

[0042] Example 2: Please refer to Figure 1 - Figure 4 As shown, the fully automated start-up and shutdown control method for a gas-fired combined cycle unit includes the following steps: Step 1: Closed-loop water operation monitoring, automatic water injection, and automatic activation of backup water pumps; Step 2: Control the combined cycle gas turbine unit to complete the start-up and grid connection of the gas turbine; Step 3: During the start-up and shutdown of the gas combined cycle unit, automatically switch the operating modes of the medium-pressure bypass and the high-pressure bypass; Step 4: Monitor the operation of the high-pressure bypass valve and control its rapid closing or opening action; Step 5: Complete the shutdown of the gas combined cycle unit step by step through four breakpoints.

[0043] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A fully automated start-up and shutdown system for a gas-fired combined cycle unit, characterized in that: It includes the main control module of the gas combined cycle unit, the bypass control module, the bypass quick-opening and quick-closing control module, the closed-loop water control module, and the shutdown control module; The main control module of the gas combined cycle unit is used to monitor the operation of the gas turbine and steam turbine, and to obtain the operating parameters of the steam turbine side and the operating parameters of the gas turbine side. The bypass control module is used to switch and execute different operating modes of the medium-pressure bypass valve and the high-pressure bypass valve of the gas combined cycle unit. The high-pressure bypass valve and the medium-pressure bypass valve are each equipped with six automatically switching control modes: minimum opening mode, minimum pressure mode, pressure boosting mode, constant pressure mode, tracking mode, and shutdown constant pressure mode. The bypass control module automatically switches between the control modes according to the operating parameters of the gas combined cycle unit. The bypass quick-opening and quick-closing control module is used to monitor the parameters of the gas combined cycle unit in real time, and to make feasibility judgments based on the monitored parameters, thereby controlling the quick-closing and quick-opening actions of the high-pressure bypass valve. The conditions for the bypass quick-opening and quick-closing control module to control the quick-closing action of the high-pressure bypass valve are any of the following sets: The steam pressure after the high-pressure bypass valve is greater than the preset value; the steam temperature after the high-pressure bypass valve is greater than the preset temperature; the intermediate bypass quick-closing is triggered, and the high-pressure bypass quick-closing is triggered at the same time; The conditions for the bypass quick-opening and quick-closing control module to control the high-pressure bypass valve to open quickly are: turbine tripping or turbine generator disconnection; The conditions for quick opening of the high-pressure bypass valve are: no quick closing conditions, steam pressure after the high-pressure bypass valve is less than the set pressure, steam temperature after the high-pressure bypass valve is less than the set temperature and turbine load is greater than the set value for a certain period of time. The closed-loop water control module can provide cooling water to the auxiliary equipment of the gas combined cycle unit through the closed-loop water system and realize the sequential control of cooling water injection. The shutdown control module is used to set four breakpoints when the gas combined cycle unit is shut down, and to control the gas combined cycle unit according to different breakpoints; The shutdown control module has four breakpoints: unit load reduction breakpoint, unit tripping breakpoint, waste heat boiler shutdown breakpoint, and unit shutdown breakpoint. The main steps for the unit load reduction breakpoint are: exiting automatic generation control, activating automatic high, medium, and low pressure bypasses, reducing the unit load to the set load, exiting the coordinated control system mode of the unit's gas combined cycle unit, and activating automatic shaft seals. The main steps for tripping the unit are: manually confirming that the auxiliary steam conditions are met, then initiating the turbine shutdown procedure, reducing the gas turbine load to the set low load, and requesting the gas turbine to be shut down by the distributed control system. The main steps for stopping the waste heat boiler are: automatically desuperheating water of the waste heat boiler, completely stop the high / medium pressure feedwater pumps, stop the steam drum water supply, close the drain valve, start the low-efficiency recirculation system stop function group, and put the condensate pump into standby mode. The main steps for shutting down the unit are: closing the outlet damper of the waste heat boiler chimney, starting the vacuum system stop function group, starting the shaft seal system stop function group, and starting the condensate system stop function group.

2. The fully automated start-up and shutdown system for a gas-fired combined cycle unit according to claim 1, characterized in that, The parameters collected by the main control module of the gas combined cycle unit include at least: intermediate pressure bypass control mode, condenser vacuum, turbine-side reheat steam pressure, turbine-side grid connection parameters, intermediate pressure bypass valve opening, turbine main transformer high-pressure side circuit breaker status, turbine-side high-pressure steam pressure, high-pressure bypass valve opening, high-pressure bypass control mode, and gas turbine flame detection signal.

3. The fully automated start-up and shutdown system for a gas-fired combined cycle unit according to claim 2, characterized in that, The conditions for the bypass control module to switch the medium-pressure bypass valve mode are as follows: Conditions for entering minimum opening mode: the gas turbine has been ignited, the reheat steam pressure on the turbine side is greater than the set value and the intermediate bypass is automatically activated, or the gas turbine has been ignited for the set time and the condenser vacuum has reached the set value and the intermediate bypass is automatically activated. Conditions for entering minimum pressure mode: The bypass is in minimum opening mode and the reheat steam pressure on the turbine side is greater than the set value; Conditions for entering boost mode: The bypass is in minimum pressure mode and the opening of the bypass is greater than the set value; Conditions for entering constant pressure mode: The intermediate bypass is in boost mode and the reheat steam pressure on the turbine side is greater than the set value; Conditions for entering tracking mode: the bypass is in constant pressure mode, the turbine is connected to the grid, and the bypass opening is less than the set value; The conditions for entering the shutdown and pressure regulation mode are: the turbine has been shut down, or the high-voltage side circuit breaker of the turbine main transformer has been opened, or the turbine shutdown and pressure regulation mode is executed by the turbine shutdown control or the bypass shutdown and pressure regulation mode is manually activated. The conditions for the bypass control module to switch the high-pressure bypass valve mode are as follows: The conditions for entering the minimum opening mode are: the gas turbine is ignited, the high-pressure steam pressure on the turbine side is greater than the set value and the intermediate bypass is automatically activated, or the gas turbine is ignited, the condenser vacuum is less than the set value and the intermediate bypass is automatically activated. Conditions for entering minimum pressure mode: The high-pressure bypass is in minimum opening mode and the high-pressure steam pressure on the turbine side is greater than the set value; Conditions for entering boost mode: The high-pressure bypass is in minimum pressure mode and the opening of the high-pressure bypass is greater than the set value; Conditions for entering constant pressure mode: The high-pressure bypass is in pressure boosting mode and the high-pressure main steam pressure is greater than the starting pressure; Conditions for entering tracking mode: The high-pressure bypass is in constant pressure mode, the turbine is connected to the grid, and the high-pressure bypass opening is less than the set value; Conditions for entering the shutdown and constant pressure mode: The turbine has been shut down, or the high-voltage side circuit breaker of the turbine main transformer has been tripped, or the turbine shutdown control is executing the shutdown and constant pressure mode, or the bypass shutdown and constant pressure mode is manually activated.

4. The fully automated start-up and shutdown system for a gas-fired combined cycle unit according to claim 3, characterized in that, The method for sequential water injection control by the closed-loop water control module is as follows: S1: Determine whether the closed water system meets the preset water injection conditions. If the conditions are met, proceed to the next step. S2: The electric valves, regulating valves, and bypass valves of the closed water system are in the fully open state; S3: Open the demineralized water supply valve of the high-level expansion tank to start injecting water into the closed water system from the high-level expansion tank; S4: After manually confirming that all air has been expelled from the closed water system, stop water injection and close the electric valve at the outlet of the closed water pump.

5. The fully automated start-up and shutdown system for a gas-fired combined cycle unit according to claim 4, characterized in that, The closed-loop water control module controls a closed-loop water system that also includes a first standby closed-loop water pump and a second standby closed-loop water pump, both of which are set with the same standby pump start-up value. When the pressure of the closed-loop water system drops to the standby pump start-up value, the standby closed-loop water pump is activated. The specific activation method is as follows: A1: Obtain the first and second standby closed-loop water pumps that have been manually set in advance. A2: Determine whether the closed water system meets the start-up requirements; A3: Set the closed-loop water system valves to the start position; A4: Start the first standby closed-loop water pump; A5: If the pressure of the closed water system is still lower than the joint start value when the first standby closed water pump starts up after the preset delay, the second standby closed water pump will be started automatically.

6. A fully automated start-up and shutdown control method for a gas-fired combined cycle unit, applied to the fully automated start-up and shutdown system for a gas-fired combined cycle unit as described in claim 5, characterized in that... Includes the following steps: Step 1: Closed-loop water operation monitoring, automatic water injection, and automatic activation of backup water pumps; Step 2: Control the combined cycle gas turbine unit to complete the start-up and grid connection of the gas turbine; Step 3: During the start-up and shutdown of the gas combined cycle unit, automatically switch the operating modes of the medium-pressure bypass and the high-pressure bypass; Step 4: Monitor the operation of the high-pressure bypass valve and control its rapid closing or opening action; Step 5: Complete the shutdown of the gas combined cycle unit step by step through four breakpoints.

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