A steam turbine double-loop coordinated control system
By using the dual-loop coordinated control system of the steam turbine and employing a 3-out-of-2 logic to determine the ETS action signal, the main steam valve and regulating valve control modules are linked, thus resolving the safety hazards caused by AST solenoid valve malfunctions and achieving safe unit shutdown and equipment protection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DATANG BAOJI THERMOELECTRICITY FACTORY
- Filing Date
- 2025-10-14
- Publication Date
- 2026-07-21
Smart Images
Figure CN224532791U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of steam turbine safety control technology, specifically a dual-loop coordinated control system for steam turbines. Background Technology
[0002] Reliable turbine tripping is a fundamental function of the regulation and safety system, used to achieve normal unit shutdown and emergency tripping, protecting turbine equipment and preventing accidents from escalating. A typical turbine tripping method employs an Emergency Trip System (ETS), which uses four AST solenoid valves connected in series and parallel to release the safety oil pressure in the high-pressure EH oil circuit, thereby closing all main steam valves and control valves. However, due to substandard EH oil quality, inadequate maintenance, etc., AST solenoid valves are prone to jamming, and the trip module's throttling orifice is easily blocked. This can prevent the safety oil pressure from being released when the ETS activates, preventing the main steam valves and control valves from closing, posing a significant risk of turbine overspeed or equipment damage.
[0003] Some existing units have not undergone online testing of AST solenoid valves due to aging protection circuits or to avoid unplanned shutdowns. This makes it impossible to detect solenoid valve abnormalities in a timely manner, resulting in the main steam valve and control valve failing to close, posing a significant safety hazard. Utility Model Content
[0004] The purpose of this utility model is to provide a dual-circuit coordinated control system for steam turbines to solve the problem mentioned above where, due to aging of the protection circuit or to avoid unplanned shutdowns, online testing of the AST solenoid valves was not performed, so abnormalities of the solenoid valves could not be detected in time, resulting in the main steam valve and regulating valve being unable to close, posing a significant safety hazard.
[0005] To achieve the above objectives, this utility model provides the following technical solution: A dual-loop coordinated control system for a steam turbine includes an emergency shutdown system, an AST solenoid valve control loop, a main steam valve control solenoid valve, an OPC solenoid valve, and a digital electro-hydraulic control system. The emergency shutdown system is electrically connected to the AST solenoid valve control circuit. The emergency shutdown system detects the overspeed operation of the steam turbine, generates an ETS action signal, and starts the AST solenoid valve control circuit. The AST solenoid valve circuit is used for high-pressure oil circuit depressurization of the main steam valve and the regulating valve. The digital electro-hydraulic control system is electrically connected to the main steam valve control solenoid valve and the OPC solenoid valve. Three inter-cabinet cables are provided between the digital electro-hydraulic control system and the emergency trip system. The inter-cabinet cables are used to transmit the ETS action signal to the digital electro-hydraulic control system. The digital electro-hydraulic control system judges the ETS action signal based on the three-out-of-two logic and outputs a new trip signal channel. The digital electro-hydraulic control system includes a main steam valve control module and a regulating valve control module. The main steam valve control module adds a trip signal channel based on the main steam valve control logic linkage to control the main steam valve control solenoid valve. The regulating valve control module adds a trip signal channel based on the regulating valve control logic linkage to control the OPC solenoid valve. Both the main steam valve control solenoid valve and the OPC solenoid valve are used for high-pressure oil circuit depressurization to collaboratively close the main steam valve and the regulating valve.
[0006] As a further embodiment of this utility model: the digital electro-hydraulic control system obtains a pulse signal based on the ETS action signal using a 3-out-of-2 logic, the pulse signal is input to an RS trigger, and the RS trigger outputs a new trip signal channel.
[0007] As a further embodiment of this utility model: the digital electro-hydraulic control system further includes a display panel, which is used to display the DEH operation screen. When a new trip signal channel is triggered, the DEH operation screen of the display panel displays a DEH screen alarm, and a reset button is set in the DEH operation screen for resetting operation.
[0008] As a further embodiment of this utility model: the main steam valve control logic includes the main steam valve control logic of the high-pressure cylinder and the main steam valve control logic of the intermediate-pressure cylinder. The main steam valve control logic of the high-pressure cylinder and the main steam valve control logic of the intermediate-pressure cylinder are connected in parallel to add a trip signal channel. The added trip signal channel triggers the main steam valve control solenoid valve to be energized, so as to quickly close the main steam valve by depressurizing the high-pressure oil circuit.
[0009] As a further embodiment of this utility model: the regulating gate includes a high regulating gate and a medium regulating gate; The regulating valve control module includes three speed cards, a high-speed regulating valve servo card, and a medium-speed regulating valve servo card. The speed cards output speed signals. The three speed signals form an overspeed protection module based on a 3-out-of-2 logic. The regulating valve control logic also includes a turbine not engaged action. The overspeed protection module and the turbine not engaged action are linked in parallel to add a trip signal channel. Any one of the overspeed protection module, the turbine not engaged action, and the added trip signal channel triggers the output of a reset command. The reset command is transmitted to the high-speed regulating valve servo card and the medium-speed regulating valve servo card. After the command is reset, the high-speed regulating valve servo card and the medium-speed regulating valve servo card trigger the OPC solenoid valve to be energized, and the high-pressure oil circuit is depressurized to quickly close the high-speed regulating valve and the medium-speed regulating valve.
[0010] As a further embodiment of this utility model: the OPC solenoid valve includes a first solenoid valve and a second solenoid valve; The overspeed protection module includes a first protection module and a second protection module, both of which are used for overspeed protection action. The regulating gate control module includes multiple digital output cards and a power supply module. The newly added trip signal channel inputs multiple digital output cards to form a first channel module, a second channel module, a third channel module, and a fourth channel module. The power supply module includes a first power supply and a second power supply. The positive terminal of the first power supply is connected to the first terminal of switch K1, the second terminal of switch K1 is connected to the input terminal of the first channel module and the input terminal of the first protection module, the output terminal of the first channel module is connected to the input terminal of the second channel module, and the output terminals of the second channel module and the first protection module are connected to the negative terminal of the first power supply. The positive terminal of the second power supply is connected to the first terminal of switch K2, the second terminal of switch K2 is connected to the input terminal of the third channel module and the input terminal of the second protection module, the output terminal of the third channel module is connected to the input terminal of the fourth channel module, and the output terminal of the fourth channel module and the output terminal of the second protection module are connected to the negative terminal of the second power supply. Both the first and second solenoid valves are energized and release the oil pressure in the high-pressure oil circuit through a newly added trip signal channel to close the high-pressure regulating valve and the medium-pressure regulating valve.
[0011] As a further embodiment of this utility model: the AST solenoid valve control circuit includes 4 AST solenoid valves, which are arranged in two groups on average and connected in series and parallel.
[0012] Compared with the prior art, the beneficial effects of this utility model are: 1. In this utility model, when the ETS activates and the safety oil pressure cannot be released, the emergency trip system and the digital electro-hydraulic control system work together to output a new trip signal channel. This new trip signal channel is used to control and link with the main steam valve control module and the regulating valve control module. The main steam valve is directly closed through the main steam valve control solenoid valve. The regulating valve is then quickly closed by setting the logic regulating valve command to zero, clearing the regulating valve servo card command, and controlling the OPC solenoid valve. This linkage with the new trip signal channel controls the operation of the main steam valve control solenoid valve and the OPC solenoid valve respectively. This avoids turbine overspeed or equipment damage. The application of dual-loop collaborative control technology effectively avoids the risk of the trip solenoid valve jamming or the trip module throttle orifice being blocked, preventing the unit from safely shutting down due to ETS activation and causing significant equipment damage.
[0013] 2. In this utility model, in order to prevent the first solenoid valve and the second solenoid valve from being opened accidentally, the first channel module and the second channel module are connected in series, and the third channel module and the fourth channel module are connected in series, adopting a redundant design to release the oil pressure in the high-pressure oil circuit so as to close the high-adjustment valve and the medium-adjustment valve. Attached Figure Description
[0014] Figure 1This is a schematic diagram of the system connection of this utility model; Figure 2 This is a schematic diagram of the control principle of the first solenoid valve of this utility model; Figure 3 This is a schematic diagram of the control principle of the second solenoid valve of this utility model.
[0015] In the diagram: 1. First solenoid valve; 2. Second solenoid valve; 3. First protection module; 4. Second protection module; 5. First power supply; 6. Second power supply; 7. First channel module; 8. Second channel module; 9. Third channel module; 10. Fourth channel module. Detailed Implementation
[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.
[0017] Example: Please see Figure 1 In this embodiment of the invention, a dual-loop coordinated control system for a steam turbine includes an Emergency Trip System (ETS), an AST solenoid valve control loop, a main steam valve control solenoid valve, an OPC solenoid valve, and a digital electro-hydraulic control system (DEH). The Emergency Shutdown System (ETS) is electrically connected to the AST solenoid valve control circuit. The Emergency Shutdown System (ETS) detects overspeed operation of the steam turbine, generates an ETS action signal, and activates the AST solenoid valve control circuit. The AST solenoid valve circuit is used to release the high-pressure oil circuit of the main steam valve and the regulating valve. The digital electro-hydraulic control system (DEH) is electrically connected to the main steam valve control solenoid valve and the OPC solenoid valve. There are three inter-cabinet cables between the digital electro-hydraulic control system (DEH) and the emergency trip system (ETS). The inter-cabinet cables are used to transmit the ETS action signal to the digital electro-hydraulic control system (DEH). The digital electro-hydraulic control system (DEH) judges the ETS action signal based on the three-out-of-two logic and outputs a new trip signal channel (ETSTODEH). The digital electro-hydraulic control system (DEH) includes a main steam valve control module and a regulating valve control module. The main steam valve control module adds a trip signal channel (ETSTODEH) based on the main steam valve control logic to control the main steam valve control solenoid valve. The regulating valve control module adds a trip signal channel (ETSTODEH) based on the regulating valve control logic to control the OPC solenoid valve. Both the main steam valve control solenoid valve and the OPC solenoid valve are used for high-pressure oil circuit depressurization to coordinate the closure of the main steam valve and the regulating valve.
[0018] Specifically, this system, through the linkage of the emergency trip system and the digital electro-hydraulic control system, allows the emergency trip system to monitor the turbine's operating status in real time. Upon detecting abnormalities such as overspeeding, it immediately generates an ETS (Emergency Trip System) action signal and activates the AST (Anti-Stage Solenoid Valve) control circuit. The AST circuit then quickly closes the main steam valve and regulating valve by controlling the pressure relief of the high-pressure oil circuit. When the ETS activates but the safety oil pressure cannot be released, the emergency trip system and the digital electro-hydraulic control system work together to output a new trip signal channel. This new trip signal channel is then used to communicate with the main steam valve control module and... The control module controls the main steam valve by directly closing it through the main steam valve control solenoid valve. It also controls the OPC solenoid valve by setting the logic control valve command to zero, clearing the control valve servo card command, and controlling the OPC solenoid valve's action, thus quickly closing the control valve. A new trip signal channel is added to control the actions of both the main steam valve control solenoid valve and the OPC solenoid valve. This avoids turbine overspeed or equipment damage. The application of dual-loop coordinated control technology effectively prevents the trip solenoid valve from jamming or the trip module's throttling orifice from becoming blocked, thus avoiding the significant risk of the ETS (Electronic Toll System) failing to safely shut down the unit and causing equipment damage.
[0019] Preferably, the digital electro-hydraulic control system (DEH) uses a 3-out-of-2 logic to determine the ETS action signal to obtain a pulse signal. The pulse signal is input to the RS flip-flop, and the RS flip-flop outputs a new trip signal channel (ETSTODEH).
[0020] Specifically, the digital electro-hydraulic control system transmits the ETS action signal through three inter-cabinet cables. The digital electro-hydraulic control system uses a 2-out-of-3 logic to determine the pulse signal from the ETS action signal. This pulse signal has high reliability and stability, effectively avoiding misjudgments caused by a single abnormal signal. After receiving the ETS action signal, the digital electro-hydraulic control system quickly performs a comprehensive analysis and judgment on the three signals. Only when at least two of the signals indicate that the ETS has taken action will the corresponding pulse signal be generated. After receiving the pulse signal, the RS trigger processes the signal according to its internal logic characteristics to ensure that the newly added trip signal channel is stable and reliable. This new channel serves as a key connection between the digital electro-hydraulic control system and the external tripping equipment, enabling it to quickly and accurately transmit the trip command when the ETS takes action, thereby effectively ensuring the safe shutdown of the unit.
[0021] Preferably, the digital electro-hydraulic control system (DEH) also includes a display panel for displaying the DEH operation screen. When a new trip signal channel (ETSTODEH) is triggered, the DEH operation screen on the display panel displays a DEH screen alarm and a reset button is set in the DEH operation screen for resetting.
[0022] Specifically, the display panel uses a high-definition touch screen that can clearly and accurately display various parameters and status information of the DEH operation screen, ensuring that operators can intuitively obtain the system's operating status. When a new trip signal channel is triggered, the DEH screen alarm will be displayed on the operation screen with a striking color and obvious prompt information, promptly reminding operators to pay attention to abnormal system conditions. After the system completes the corresponding processing and confirms safety, the operator only needs to press the reset button to reset the DEH system, restoring it to normal working status so that stable control and monitoring of the unit can continue.
[0023] Preferably, the main steam valve control logic includes the main steam valve control logic for the high-pressure cylinder and the main steam valve control logic for the intermediate-pressure cylinder. The main steam valve control logic for the high-pressure cylinder and the main steam valve control logic for the intermediate-pressure cylinder are connected in parallel and linked to add a trip signal channel. The added trip signal channel triggers the main steam valve control solenoid valve to be energized, so as to quickly close the main steam valve by depressurizing the high-pressure oil circuit.
[0024] Specifically, the high-pressure cylinder main steam valve control logic is triggered by a new trip signal channel. The control logic responds rapidly, instantly energizing the main steam valve control solenoid valve and quickly depressurizing the high-pressure oil circuit. This closes the high-pressure cylinder main steam valve in a very short time, preventing the fault from escalating further. Similarly, the intermediate-pressure cylinder main steam valve control logic has a similar rapid response mechanism. It works in conjunction with the high-pressure cylinder main steam valve control logic. When a new trip signal channel is triggered, the intermediate-pressure cylinder main steam valve will also close rapidly, ensuring the safe shutdown of the entire unit under abnormal conditions and effectively guaranteeing the safe and stable operation of the unit equipment.
[0025] Preferably, the tuning gate includes a high-pitched tuning gate and a medium-pitched tuning gate; The regulating valve control module includes three speed cards, a high-speed regulating valve servo card, and a medium-speed regulating valve servo card. The speed cards output speed signals. The three speed signals form an overspeed protection module based on a 3-out-of-2 logic. The regulating valve control logic also includes a turbine not engaged action. The overspeed protection module and the turbine not engaged action are linked in parallel to add a trip signal channel. Any one of the overspeed protection module, the turbine not engaged action, and the newly added trip signal channel can trigger the output of a clear command. The clear command is transmitted to the high-speed regulating valve servo card and the medium-speed regulating valve servo card. After the high-speed regulating valve servo card and the medium-speed regulating valve servo card are cleared, the OPC solenoid valve is energized, and the high-pressure oil circuit is used to quickly close the high-speed regulating valve and the medium-speed regulating valve.
[0026] Specifically, the three speed cards will output corresponding speed signals in real time. These speed signals are judged and processed through a 3-out-of-2 logic to form an overspeed protection module. The overspeed protection module, the turbine not being engaged, and the newly added trip signal channel can trigger a reset command. When any one of these is triggered, a reset command will be output immediately. The reset command is set to zero through the logic control valve command. At the same time, the reset command will be quickly transmitted to the high-speed control valve servo card and the medium-speed control valve servo card, so that the commands in these two servo cards are reset. After the command is reset, the OPC solenoid valve will be energized, which will cause the high-pressure oil circuit to be depressurized, and finally the high-speed control valve and the medium-speed control valve will be quickly closed. This ensures that the unit can take timely protective measures when facing abnormal situations such as overspeed or turbine not being engaged, and ensures the safe operation of the unit.
[0027] Preferred, such as Figure 2 and Figure 3 As shown, the OPC solenoid valve includes a first solenoid valve 1 and a second solenoid valve 2. The overspeed protection module includes a first protection module 3 and a second protection module 4, both of which are used for overspeed protection action; The regulating control module includes multiple digital output cards and a power supply module. The trip signal input is added to multiple digital output cards to form a first channel module 7, a second channel module 8, a third channel module 9 and a fourth channel module 10. The power supply module includes a first power supply 5 and a second power supply 6. The positive terminal of the first power supply 5 is connected to the first terminal of switch K1, the second terminal of switch K1 is connected to the input terminal of the first channel module 7 and the input terminal of the first protection module 3, the output terminal of the first channel module 7 is connected to the input terminal of the second channel module 8, and the output terminals of the second channel module 8 and the first protection module 3 are connected to the negative terminal of the first power supply 5. The positive terminal of the second power supply 6 is connected to the first terminal of switch K2, the second terminal of switch K2 is connected to the input terminal of the third channel module 9 and the input terminal of the second protection module 4, the output terminal of the third channel module 9 is connected to the input terminal of the fourth channel module 10, and the output terminal of the fourth channel module 10 and the output terminal of the second protection module 4 are connected to the negative terminal of the second power supply 6. Both the first solenoid valve 1 and the second solenoid valve 2 are energized and release the oil pressure in the high-pressure oil circuit through the newly added trip signal channel to close the high-pressure regulating valve and the medium-pressure regulating valve.
[0028] Specifically, to prevent the first solenoid valve 1 and the second solenoid valve 2 from opening accidentally, the first channel module 7 and the second channel module 8 are connected in series, and the third channel module 9 and the fourth channel module 10 are connected in series, adopting a redundant design. The first solenoid valve 1 is triggered by two channel modules, which improves the reliability of the action. When the switch K1 connected to the first power supply 5 is closed, the first channel module 7 and the first protection module 3 obtain the electrical energy required for operation. When the emergency shutdown system cannot depressurize, the first channel module 7 and the second channel module 8 are connected in series, together with the first protection module 3, to trigger the first solenoid valve 1 to close the high-adjustment door and the medium-adjustment door. Similarly, for the second power supply 6, after switch K2 is closed, the third channel module 9 and the second protection module 4 are connected in series and in parallel to the second protection module 4, and together trigger the second solenoid valve 2 to close the high-pressure regulating valve and the medium-pressure regulating valve; quickly release the oil pressure in the high-pressure oil circuit, so that the high-pressure regulating valve and the medium-pressure regulating valve can close quickly, thereby effectively avoiding damage to the unit due to abnormal conditions such as overspeed, and ensuring the safety and stability of the entire unit operation.
[0029] Preferably, the AST solenoid valve control circuit includes four AST solenoid valves, which are arranged in two groups on average and connected in series and parallel.
[0030] Specifically, the first group consists of the first AST solenoid valve and the third AST solenoid valve connected in series; the second group consists of the second AST solenoid valve and the fourth AST solenoid valve connected in series. The four AST solenoid valves are arranged in a series-parallel configuration. If any one of the first AST solenoid valves or the third AST solenoid valve operates, and any one of the second AST solenoid valves or the fourth AST solenoid valve operates, the safety oil pressure will be released, and the turbine will trip.
[0031] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.
Claims
1. A dual-loop coordinated control system for a steam turbine, comprising an emergency trip system, an AST solenoid valve control loop, a main steam valve control solenoid valve, an OPC solenoid valve, and a digital electro-hydraulic control system, characterized in that: The emergency shutdown system is electrically connected to the AST solenoid valve control circuit. The emergency shutdown system detects the overspeed operation of the steam turbine, generates an ETS action signal, and starts the AST solenoid valve control circuit. The AST solenoid valve circuit is used for high-pressure oil circuit depressurization of the main steam valve and the regulating valve. The digital electro-hydraulic control system is electrically connected to the main steam valve control solenoid valve and the OPC solenoid valve. Three inter-cabinet cables are provided between the digital electro-hydraulic control system and the emergency trip system. The inter-cabinet cables are used to transmit the ETS action signal to the digital electro-hydraulic control system. The digital electro-hydraulic control system judges the ETS action signal based on the three-out-of-two logic and outputs a new trip signal channel. The digital electro-hydraulic control system includes a main steam valve control module and a regulating valve control module. The main steam valve control module adds a trip signal channel based on the main steam valve control logic linkage to control the main steam valve control solenoid valve. The regulating valve control module adds a trip signal channel based on the regulating valve control logic linkage to control the OPC solenoid valve. Both the main steam valve control solenoid valve and the OPC solenoid valve are used for high-pressure oil circuit depressurization to collaboratively close the main steam valve and the regulating valve.
2. The dual-loop coordinated control system for a steam turbine according to claim 1, characterized in that: The digital electro-hydraulic control system uses a 3-out-of-2 logic to determine the ETS action signal and obtain a pulse signal. The pulse signal is input to an RS trigger, and the RS trigger outputs a new trip signal channel.
3. The dual-loop coordinated control system for a steam turbine according to claim 2, characterized in that: The digital electro-hydraulic control system also includes a display panel for displaying the DEH operation screen. When a new trip signal channel is triggered, the DEH operation screen on the display panel displays a DEH alarm and includes a reset button for resetting.
4. The dual-loop coordinated control system for a steam turbine according to claim 2, characterized in that: The main steam valve control logic includes the high-pressure cylinder main steam valve control logic and the intermediate-pressure cylinder main steam valve control logic. The high-pressure cylinder main steam valve control logic and the intermediate-pressure cylinder main steam valve control logic are connected in parallel to add a trip signal channel. The added trip signal channel triggers the main steam valve control solenoid valve to be energized, so as to quickly close the main steam valve by depressurizing the high-pressure oil circuit.
5. A dual-loop coordinated control system for a steam turbine according to claim 4, characterized in that: The modulation gate includes a high modulation gate and a medium modulation gate; The regulating valve control module includes three speed cards, a high-speed regulating valve servo card, and a medium-speed regulating valve servo card. The speed cards output speed signals. The three speed signals form an overspeed protection module based on a 3-out-of-2 logic. The regulating valve control logic also includes a turbine not engaged action. The overspeed protection module and the turbine not engaged action are linked in parallel to add a trip signal channel. Any one of the overspeed protection module, the turbine not engaged action, and the added trip signal channel triggers the output of a reset command. The reset command is transmitted to the high-speed regulating valve servo card and the medium-speed regulating valve servo card. After the command is reset, the high-speed regulating valve servo card and the medium-speed regulating valve servo card trigger the OPC solenoid valve to be energized, and the high-pressure oil circuit is depressurized to quickly close the high-speed regulating valve and the medium-speed regulating valve.
6. A dual-loop coordinated control system for a steam turbine according to claim 5, characterized in that: The OPC solenoid valve includes a first solenoid valve (1) and a second solenoid valve (2); The overspeed protection module includes a first protection module (3) and a second protection module (4), both of which are used for overspeed protection action; The regulating gate control module includes multiple digital output cards and a power supply module. The newly added trip signal channel inputs multiple digital output cards to form a first channel module (7), a second channel module (8), a third channel module (9), and a fourth channel module (10). The power supply module includes a first power supply (5) and a second power supply (6). The positive terminal of the first power supply (5) is connected to the first end of the switch K1, the second end of the switch K1 is connected to the input terminal of the first channel module (7) and the input terminal of the first protection module (3), the output terminal of the first channel module (7) is connected to the input terminal of the second channel module (8), and the output terminals of the second channel module (8) and the first protection module (3) are connected to the negative terminal of the first power supply (5). The positive terminal of the second power supply (6) is connected to the first terminal of switch K2, the second terminal of switch K2 is connected to the input terminal of the third channel module (9) and the input terminal of the second protection module (4), the output terminal of the third channel module (9) is connected to the input terminal of the fourth channel module (10), and the output terminal of the fourth channel module (10) and the output terminal of the second protection module (4) are connected to the negative terminal of the second power supply (6). Both the first solenoid valve (1) and the second solenoid valve (2) are energized and release the oil pressure in the high-pressure oil circuit through the newly added trip signal channel to close the high-pressure regulating valve and the medium-pressure regulating valve.
7. A dual-loop coordinated control system for a steam turbine according to claim 1, characterized in that: The AST solenoid valve control circuit includes four AST solenoid valves, which are arranged in two groups on average and connected in series and parallel.