350mw supercritical non-deaerator unit external steam supply system and method

Abstract

The application discloses a 350MW supercritical non-deaerator unit external steam supply system and method, and mainly relates to the technical field of steam extraction and heat supply of thermal power generating units; the system comprises an external steam pipeline extracted from a reheating hot section, a two-stage steam extraction pipeline for maintaining the temperature of feed water, a high-pressure bypass for maintaining the stability of main steam pressure, a low-pressure bypass for stabilizing the pressure of a steam supply source, and a system cooperative control module; one end of the two-stage steam extraction pipeline is connected with a #2 high-pressure heater, and a steam extraction check valve and a steam extraction electric valve are arranged on the two-stage steam extraction pipeline; the system cooperative control module is used for cooperatively adjusting the opening degree of the high-pressure bypass, the opening degree of the low-pressure bypass, the coal supply amount of the boiler and the feed water amount; the application can realize safe, stable and efficient supply of external industrial steam under the condition of "stopping the unit without stopping the boiler".

Description

Technical Field

[0001] This invention relates to the field of steam extraction and heating technology for thermal power units, specifically to an external steam supply system and method for a 350MW supercritical deaerator-free unit. Background Technology

[0002] Currently, existing large-scale thermal power units (such as 350MW supercritical units) generally adopt "Fast Cut Back" (FCB) technology, which can maintain generator and boiler operation and quickly restore power supply during grid faults. The core objective of traditional FCB operation is to maintain plant power consumption and quickly connect to the grid. Its main technical focus is on bypass control, combustion stability, and turbine speed control, without considering the situation of external steam supply. With the increasing demand for external industrial heating, how to safely, stably, and efficiently provide qualified steam (e.g., 3.7MPa / 455℃) to external industrial users under abnormal FCB operating conditions has become an urgent problem to be solved. This is especially true for units without deaerators, where the inability to meet steam supply requirements during peak shaving and shutdown significantly impacts the profitability of thermal power plants.

[0003] The existing 350MW supercritical deaerator-free units have the following main shortcomings when supplying steam to the outside under the condition of "shutdown without boiler interruption": 1. Poor adaptability of the thermal system: Traditional FCB designs do not consider the need for stable external steam supply. In supercritical once-through boiler units without deaerators, when the unit is switched to plant auxiliary power, the boiler enters wet operation, and the main steam pressure and temperature change drastically. If high-grade steam is directly extracted for external supply at this time, it is very easy to cause instability of the main steam parameters, affecting the boiler's hydrodynamic safety.

[0004] 2. Difficulty in controlling feedwater temperature: For units without deaerators, feedwater heating relies entirely on regenerative extraction steam. When the unit is disconnected, the turbine is idling, or operating at low load, the extraction steam pressure of the traditional high-pressure heater (high-pressure heater) drops significantly or even disappears, making it impossible to maintain the feedwater temperature (design requirement 240±10℃). Excessively low feedwater temperature directly affects boiler combustion stability, steam temperature, and the safety of the tail-end heating surfaces, and also exacerbates the risk of low-temperature corrosion.

[0005] 3. Strong coupling and difficulty in decoupling between steam supply parameters and boiler operating parameters: The extraction of external steam directly affects the main steam flow and pressure, thus creating a strong coupling with the bypass system that maintains the boiler's wet operation. Existing control systems lack a coordinated control strategy for the strong coupling of multiple variables in the "steam supply-bypass-combustion-feedwater" system, resulting in large fluctuations in steam supply pressure and temperature, making it difficult to meet the stable steam quality requirements of industrial users.

[0006] 4. Mismatched thermodynamic cycles and poor economic efficiency: Traditional methods may directly draw steam from the main steam or cold / reheat steam pipelines, resulting in unreasonable energy utilization and large energy loss.

[0007] Therefore, under the special operating condition of shutting down the boiler without stopping the steam turbine, there is an urgent need for an efficient and low-energy-consumption steam supply path and method that can match the boiler output and turbine status at this time. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and provide an external steam supply system and method for a 350MW supercritical deaerator-free unit, which can achieve a safe, stable and efficient supply of external industrial steam under the condition of "shutdown without boiler interruption".

[0009] To achieve the above objectives, the present invention employs the following technical solution: The external steam supply system of the 350MW supercritical deaerator-free unit includes an external steam supply pipeline drawn from the reheat section, a two-stage extraction steam pipeline for maintaining feedwater temperature, a high-pressure bypass for maintaining stable main steam pressure, a low-pressure bypass for stabilizing the steam source pressure, and a system coordination control module. One end of the two-stage extraction steam pipeline is connected to the #2 high-pressure heater, and an extraction steam non-return valve and an extraction steam electric valve are installed on the two-stage extraction steam pipeline. The system coordination control module is used to coordinate the adjustment of the opening degree of the high-pressure bypass, the opening degree of the low-pressure bypass, and the boiler's coal and water feed rates.

[0010] Preferably, when maintaining the feedwater temperature, the cold re-steam after the high-pressure exhaust check valve when the turbine is shut down or idling is used as a heat source.

[0011] Preferably, while maintaining the feedwater temperature, the temporary heating to the #2 high-pressure heater or the auxiliary steam heating to the #4 low-pressure heater is used as a backup preheating method.

[0012] Preferably, when maintaining the feedwater temperature, the feedwater temperature is maintained at 240±10℃ by adjusting the second-stage extraction steam flow control valve and making full use of the built-in condensate cooling section function of the #2 high-pressure heater.

[0013] Preferably, a steam supply regulating valve is provided on the external steam supply pipeline. When steam is drawn from the reheat section through the external steam supply pipeline, the main steam pressure is first stabilized by using a high-pressure bypass. Then, the steam supply source pressure is stabilized by adjusting the low-pressure bypass and / or extraction steam valve. Finally, the steam supply regulating valve realizes closed-loop control of the steam supply pressure and temperature.

[0014] Preferably, the system collaborative control module includes a steam supply-bypass collaborative submodule and a combustion-feedwater-steam supply balance submodule. The steam supply-bypass collaborative submodule prioritizes maintaining stable main steam pressure and reheat steam pressure, dynamically adjusts the opening of the high-pressure bypass and low-pressure bypass, and uses the increase or decrease in external steam supply as a feedforward signal to fine-tune the bypass opening in advance to counteract its disturbance. The combustion-feedwater-steam supply balance submodule calculates the required boiler evaporation based on the target steam supply and the feedwater demand of the boiler in wet operation, and then determines the benchmark values ​​of coal feed and total air volume, and introduces the water level of the storage tank and the main steam temperature change rate as feedback for correction.

[0015] Preferably, in the steam supply-bypass coordination submodule, when the external load increases, the external supply load increases, the pressure before the high-pressure bypass decreases, the boiler automatically operates to maintain the pressure unchanged, the fuel quantity automatically increases, and the feedwater automatically increases according to a given function.

[0016] Preferably, the system collaborative control module further includes a protection logic dynamic management submodule, which includes setting malfunctioning MFT conditions and core protection conditions. The malfunctioning MFT conditions include low feedwater flow and low total air volume; the core protection conditions include turbine tripping and boiler tripping. Before steam supply, the malfunctioning MFT conditions are released, while the core protection conditions are retained.

[0017] Preferably, the system collaborative control module further includes a safety monitoring submodule, which sets rate alarms and hard protection thresholds for key parameters. When the thresholds are exceeded, an audible and visual alarm is triggered and a preset stabilization strategy is automatically executed. The key parameters include superheat, main / reheat steam temperature drop rate, and condenser liquid level. The stabilization strategy includes suspending steam supply for adjustment.

[0018] Secondly, the present invention provides a method for supplying steam to the external system of a 350MW supercritical deaerator-free unit, as follows: Under the condition of unit shutdown without boiler shutdown, the second stage extraction steam pipeline of the steam turbine is isolated and kept unobstructed, and the extraction steam non-return valve and extraction steam electric valve are forcibly opened. Cold resteam is used as a heat source to maintain the feedwater temperature. The system collaborative control module coordinates steam supply, bypass, combustion and feedwater to achieve dynamic balance between steam supply and boiler operation. When supplying steam to the outside, the condenser liquid level is maintained through a correlation model. The correlation model is: external steam supply = steam supply for condenser makeup water + steam supply for soot blowing + steam supply for air heater + steam supply for temporary operation. When the external steam supply is too large and the condenser liquid level cannot be maintained, the correlation model will give a maximum safe steam supply suggestion or trigger the automatic start of the standby demineralized water pump. When supplying steam to external users, the low-pressure bypass is closed, and the high-pressure bypass operates automatically through pressure control to maintain stable reheater pressure. Except for the self-use heating feedwater and the portion used by the boiler, all the steam produced by the boiler is supplied to external users. The boiler combustion is put into automatic operation to ensure the internal heat balance of the boiler.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention draws steam from the reheat section as an external steam source, which can reduce direct interference to the main steam system and ensure the hydraulic safety of the boiler. This invention achieves stable maintenance of feedwater temperature under steam supply conditions. By using two-stage steam extraction and high-pressure heaters, the feedwater temperature is maintained under turbine idling conditions, overcoming the operational bottleneck of units without deaerators under this special condition, ensuring the long-term safe and stable operation of the boiler, and avoiding the risks of low-temperature corrosion of heating surfaces and unstable combustion.

[0020] 2. This invention achieves a stable supply of high-quality industrial steam. Through the steam supply path of high bypass pressure and low-grade steam extraction and intelligent collaborative control, the external steam supply pressure fluctuation can be controlled within ±0.3MPa and the temperature fluctuation within ±10℃. The steam supply quality fully meets the needs of high-end industrial users and expands the profit model of the unit.

[0021] 3. This invention improves the system's security and automation level. Through collaborative control logic and multi-level protection strategies, it effectively decouples the coupling between systems, reduces the intensity of manual intervention by operators and the risk of misoperation, and the temporary protection activation and deactivation mechanism safeguards the bottom line of safety while expanding functions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the feedwater heating steam source for the No. 2 high-pressure heater and the No. 4 low-pressure heater under the condition of shutdown without boiler shutdown. Figure 2 This is a schematic diagram of the main steam, reheat steam, and high and low pressure bypasses; The attached diagram is labeled as follows: 1. External steam supply pipeline; 2. Second-stage extraction steam pipeline; 5. No. 2 high-pressure heater; 6. Extraction steam non-return valve; 7. Steam extraction electric valve; 8. High-pressure bypass; 9. Low-pressure bypass; 10. Boiler superheater; 11. Boiler reheater; 12. Supply... 13. Steam regulating valve; 14. Standby gas source for temporary replenishment; 15. High-pressure heater #1; 16. High-pressure heater #0; 17. High-pressure heater #3; 18. Feedwater pump steam engine; 19. Low-pressure heater #4; 20. Low-pressure heater #6; 21. Low-pressure heater #7; 22. Condenser; 23. Low-pressure heater #8; 24. Low-pressure cylinder; 25. Intermediate-pressure steam turbine; 26. High-pressure steam turbine; 27. High-pressure cylinder; 28. Intermediate-pressure cylinder; 29. ​​Condenser. Detailed Implementation

[0023] The present invention will now be described in detail and completely with reference to the accompanying drawings and specific embodiments.

[0024] It should be noted that in the description of this invention, the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. These terms are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance. The terms "horizontal," "vertical," and "suspended," etc., do not indicate that the component must be absolutely horizontal or suspended, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0025] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Example 1: like Figure 2As shown, this invention discloses an external steam supply system for a 350MW supercritical deaerator-free unit. Based on the existing 350MW supercritical deaerator-free unit, without changing the structure of the existing 350MW supercritical deaerator-free unit, the second-stage extraction steam pipeline of the turbine is isolated and kept unobstructed under the condition of unit shutdown without boiler shutdown. Specifically, the 350MW supercritical deaerator-free unit mainly includes a high-pressure cylinder 27, an intermediate-pressure cylinder 28, a condenser 29, a low-pressure cylinder 24, an intermediate-pressure turbine 25, a high-pressure turbine 26, and a condenser 22, etc. This embodiment also includes an external steam supply pipeline 1 drawn from the reheat section, a two-stage extraction steam pipeline 2 for maintaining feedwater temperature, a high-pressure bypass 8 for maintaining stable main steam pressure, a low-pressure bypass 9 for stabilizing the steam source pressure, and a system coordination control module; wherein, one end of the two-stage extraction steam pipeline 2 is connected to the No. 2 high-pressure heater 5, and an extraction steam non-return valve 6 and an extraction steam electric valve 7 are provided on the two-stage extraction steam pipeline 2; the system coordination control module is used to coordinate and adjust the opening degree of the high-pressure bypass 8, the opening degree of the low-pressure bypass 9, and the coal and water feed rates of the boiler.

[0027] The aforementioned high-pressure bypass 8 includes two parallel lines, which connect the boiler superheater 10 and the boiler reheater 11. The superheated steam from the boiler superheater 10 is de-heated and depressurized, then passes through the boiler cold reheat pipeline and enters the boiler reheater 11. After the boiler reheater 11 raises the temperature, it supplies steam to the external steam supply pipeline 1 (which can be the industrial oil and gas pipeline in the plant area). A de-heating and depressurization device is installed on the high-pressure bypass 8. The high-pressure bypass 8 is also connected to the high-pressure cylinder 27. The aforementioned low-pressure bypass 9 includes two parallel paths. The two low-pressure bypasses 9 connect the boiler reheater 11 and the condenser 29. Steam from the boiler reheater 11 passes through the reheat steam hot section and then enters the condenser 29 after being de-heated and depressurized. A de-heating and depressurization device is installed on the low-pressure bypass 9. The low-pressure bypass 9 is also connected to the intermediate-pressure cylinder 28.

[0028] In this embodiment, by setting a low-pressure bypass 9, steam is drawn from the reheat section as an external steam source. Instead of directly taking steam from the high-grade main steam or the reheat section, the pressure of the reheat section is controlled by using primary industrial steam extraction (lower parameters) or by adjusting the low-pressure bypass 9 (low bypass). This reduces direct interference to the main steam system and better matches the low steam pressure of the boiler in wet operation.

[0029] In this embodiment, when maintaining the feedwater temperature, the cold re-steam after the high-pressure exhaust check valve when the turbine is shut down or idling is used as a heat source. At this time, the pressure and temperature of the cold re-steam can still meet the requirements.

[0030] In this embodiment, while maintaining the feedwater temperature, temporary heating to the No. 2 high-pressure heater or auxiliary steam heating to the No. 4 low-pressure heater is used as a backup preheating means to ensure the system responds quickly. In this embodiment, an auxiliary steam heating box is connected to the No. 4 low-pressure heater; the two-stage extraction steam pipeline 2 connected to the No. 2 high-pressure heater is equipped with an extraction steam non-return valve 6 and an extraction steam electric valve 7.

[0031] In this embodiment, while maintaining the feedwater temperature, the final feedwater temperature can be precisely controlled at 240±10℃ by adjusting the two-stage extraction steam flow control valve and making full use of the built-in condensate cooling section function of the No. 2 high-pressure heater.

[0032] In this embodiment, a steam supply regulating valve 12 is provided on the external steam supply pipeline. Precise throttling control is achieved through the steam supply regulating valve. When steam is drawn from the reheat section through the external steam supply pipeline, the main steam pressure is first stabilized (5.5±0.2MPa) using the high-pressure bypass to provide a basis for boiler operation. Then, the steam source pressure is stabilized by adjusting the low-pressure bypass and / or extraction valve. Finally, the steam supply regulating valve achieves closed-loop control of the steam supply pressure (4.2±0.5MPa) and temperature (455±20℃).

[0033] In this embodiment, a multi-system collaborative intelligent control logic is built within the system collaborative control module. This multi-system collaborative intelligent control logic is embedded in the unit's distributed control system (DCS) to coordinate steam supply, bypass, combustion, and feedwater, thereby achieving a dynamic balance between steam supply and boiler operation. The multi-system collaborative intelligent control logic includes a steam supply-bypass collaborative sub-logic and a combustion-feedwater-steam supply balance sub-logic. Among them, the steam supply-bypass coordination sub-logic prioritizes maintaining the stability of main steam pressure and reheat steam pressure, dynamically adjusts the opening of high-pressure bypass and low-pressure bypass, and uses the increase or decrease of external steam supply as a feedforward signal to fine-tune the bypass opening in advance to counteract its disturbance. The combustion-feedwater-steam balance sub-logic calculates the required boiler evaporation based on the target steam supply and the feedwater demand of the boiler in wet operation. It then determines the baseline values ​​for coal feed and total air volume and introduces the water level in the storage tank and the main steam temperature variation rate as feedback for correction.

[0034] Preferably, in the steam supply-bypass coordination sub-logic, maintaining stable main steam pressure and reheat steam pressure is the priority objective, and the high and low bypass opening degrees are dynamically adjusted. The increase or decrease in external steam supply is used as a feedforward signal to automatically operate the high-pressure bypass to maintain stable pressure before the bypass. When external load demand increases or decreases, it directly causes pressure changes, which the boiler tracks during automatic operation. When the external load increases, to ensure stable external steam pressure, the pressure before the high-pressure bypass decreases as the external load increases. The boiler automatically maintains the pressure, automatically increases fuel quantity, and automatically increases feedwater according to a given function ratio. The feedwater flow rate and fuel quantity maintain a specific functional relationship—i.e., "water-coal ratio" control—thereby achieving automatic adjustment of steam pressure and temperature while meeting the external steam supply load requirements.

[0035] In this embodiment, based on the target steam supply and the boiler's dry-state operation water demand not less than 30% of the rated load (>340t / h), the water-coal ratio is maintained at around 7.5, and the coal feed rate is (>44t / h). This avoids the boiler switching from dry to wet state operation due to excessively low fuel quantity. The control of the boiler's total air volume (>460t / h) is based on the core benchmark of boiler oxygen control. Differentiated oxygen targets are adopted for different load stages. At 30-40% load, the oxygen content is controlled at 5-6%, and at loads above 40%, the oxygen content is maintained at 3-5%, and the superheat is controlled at 25℃±10.

[0036] Preferably, the multi-system collaborative intelligent control logic also includes a protection logic dynamic management module. This module includes defining erroneous MFT conditions and core protection conditions. Erroneous MFT conditions include low feedwater flow and low total air volume; core protection conditions include turbine tripping and boiler tripping. Before steam supply, the erroneous MFT conditions are released, while the core protection conditions are retained. Before steam supply, the thermal control team temporarily and selectively releases potentially erroneous MFT conditions such as "low feedwater flow" and "low total air volume," but retains core protections (such as MFT tripping of the feedwater pump and turbine tripping and boiler tripping). These protections are automatically restored immediately after steam supply ends and load is restored.

[0037] Preferably, the system collaborative control module further includes a safety monitoring submodule to ensure steam supply safety. The safety monitoring submodule sets rate alarms and hard protection thresholds for key parameters. When the limits are exceeded, an audible and visual alarm is triggered and a preset stabilization strategy is automatically executed. The key parameters include superheat, main / reheat steam temperature drop rate, and condenser liquid level. The stabilization strategy includes suspending steam supply for adjustment.

[0038] Example 2: This invention describes an external steam supply method for a 350MW supercritical deaerator-free unit. When the turbine is shut down or idling, a specific extraction section (such as secondary extraction steam or auxiliary steam) is used as a heat source to heat and maintain the temperature of the feedwater through the high-pressure and low-pressure heater systems. Simultaneously, an external steam supply pipeline independent of the main steam is designed and controlled. Through coordinated regulation of the bypass system, extraction system, and combustion system, a dynamic balance between steam supply and boiler operation is achieved. Specific steps include: Under the condition of unit shutdown without boiler shutdown, the second-stage extraction steam pipeline of the turbine is isolated and kept unobstructed. The extraction steam non-return valve 6 and extraction electric valve 7 from the second-stage extraction steam to the No. 2 high-pressure heater are forcibly opened. The cold re-steam after the high-pressure exhaust non-return valve when the turbine is shut down or idling (the pressure and temperature still meet the requirements) is used as the heat source to maintain the feedwater temperature. Specifically, the final feedwater temperature is precisely controlled at 240±10℃ by adjusting the second-stage extraction steam flow control valve and making full use of the built-in condensate cooling section function of the No. 2 high-pressure heater. At the same time, "temporary heating to the No. 2 high-pressure heater" and "auxiliary steam heating to the No. 4 low-pressure heater" are used as backup preheating means to ensure rapid system response. The system collaborative control module coordinates steam supply, bypass, combustion, and feedwater to achieve dynamic balance between steam supply and boiler operation. When supplying steam to external users, there are measures to ensure the balance of water supply and heat for condenser 29. Condenser liquid level control can be implemented. First, a correlation model is established between the liquid level of condenser 29 and the amount of steam supplied to external users: External steam supply = Steam for condenser water supply + Steam for soot blowing + Steam for air heater + Steam for temporary use. In principle, the steam for heating the self-use feedwater is recovered to condenser 29 without any other losses. When the amount of steam supplied is large, resulting in a shortage of water supply and the liquid level of condenser cannot be maintained, the correlation model can provide a maximum safe steam supply suggestion or trigger the automatic start of the standby demineralized water pump.

[0039] In this embodiment, when supplying steam to the outside, the steam supply takes away the energy, the low-pressure bypass is completely closed, and the high-pressure bypass pressure control is put into automatic operation to maintain the reheater pressure stable. Except for the self-use heating feedwater and the self-use portion, all the steam produced by the boiler is supplied to the outside. The boiler combustion is put into automatic operation to ensure the internal heat balance of the boiler.

Claims

The external steam supply system for a 1.350MW supercritical deaerator-free unit is characterized by: It includes an external steam supply pipeline drawn from the reheat section, a two-stage extraction steam pipeline for maintaining feedwater temperature, a high-pressure bypass for maintaining stable main steam pressure, a low-pressure bypass for stabilizing the steam source pressure, and a system coordination control module; wherein, one end of the two-stage extraction steam pipeline is connected to the #2 high-pressure heater, and an extraction steam non-return valve and an extraction steam electric valve are provided on the two-stage extraction steam pipeline; the system coordination control module is used to coordinate and adjust the opening degree of the high-pressure bypass, the opening degree of the low-pressure bypass, and the coal and water feed rates of the boiler.

2. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 1, characterized in that, When maintaining the feedwater temperature, the cold re-steam after the high-pressure exhaust check valve when the turbine is shut down or idling is used as a heat source.

3. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 1, characterized in that, While maintaining the feedwater temperature, temporary heating to the #2 high-pressure heater or auxiliary steam heating to the #4 low-pressure heater are used as backup preheating methods.

4. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 1, characterized in that, While maintaining the feedwater temperature, the feedwater temperature is maintained at 240±10℃ by adjusting the second-stage extraction steam flow control valve and making full use of the built-in condensate cooling section function of the #2 high-pressure heater.

5. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 1, characterized in that, The external steam supply pipeline is equipped with a steam supply regulating valve. When steam is drawn from the reheat section through the external steam supply pipeline, the main steam pressure is first stabilized by using the high-pressure bypass; then, the steam source pressure is stabilized by adjusting the low-pressure bypass and / or extraction steam valve; finally, the steam supply regulating valve realizes closed-loop control of the steam supply pressure and temperature.

6. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 1, characterized in that, The system's collaborative control module includes a steam supply-bypass coordination submodule and a combustion-feedwater-steam supply balance submodule. The steam supply-bypass coordination submodule prioritizes maintaining stable main steam pressure and reheat steam pressure, dynamically adjusting the opening of the high-pressure bypass and low-pressure bypass, and using the increase or decrease in external steam supply as a feedforward signal to fine-tune the bypass opening in advance to counteract disturbances. The combustion-feedwater-steam supply balance submodule calculates the required boiler evaporation based on the target steam supply and the boiler's wet-state operation feedwater requirements, thereby determining the baseline values ​​for coal feed and total air volume, and incorporating the water level in the storage tank and the main steam temperature variation rate as feedback for correction.

7. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 6, characterized in that, In the steam supply-bypass coordination submodule, when the external load increases, the external supply load increases, the pressure before the high-pressure bypass decreases, the boiler automatically operates to maintain the pressure, the fuel quantity automatically increases, and the feedwater automatically increases according to a given function.

8. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 1, characterized in that, The system collaborative control module also includes a protection logic dynamic management submodule, which includes setting malfunctioning MFT conditions and core protection conditions. The malfunctioning MFT conditions include low feedwater flow and low total air volume; the core protection conditions include turbine tripping and boiler tripping. Before steam supply, the malfunctioning MFT conditions are released, while the core protection conditions are retained.

9. The external steam supply system for a 350MW supercritical deaerator-free unit as described in claim 1, characterized in that, The system collaborative control module also includes a safety monitoring submodule, which sets rate alarms and hard protection thresholds for key parameters. When the thresholds are exceeded, an audible and visual alarm is triggered and a preset stability control strategy is automatically executed. The key parameters include superheat, main / reheat steam temperature drop rate, and condenser liquid level. The stability control strategy includes suspending steam supply for adjustment.

10. The external steam supply method of the external steam supply system for a 350MW supercritical deaerator-free unit as described in any one of claims 1-9, characterized in that: Under the condition of unit shutdown without boiler shutdown, the second stage extraction steam pipeline of the steam turbine is isolated and kept unobstructed, and the extraction steam non-return valve and extraction steam electric valve are forcibly opened. Cold resteam is used as a heat source to maintain the feedwater temperature. The system collaborative control module coordinates steam supply, bypass, combustion and feedwater to achieve dynamic balance between steam supply and boiler operation. When supplying steam to the outside, the condenser liquid level is maintained by the correlation model. The correlation model is: external steam supply = steam supply for condenser makeup water + steam supply for soot blowing + steam supply for air heater + steam supply for temporary operation. When the external steam supply is too large and the condenser liquid level cannot be maintained, the correlation model will give a maximum safe steam supply suggestion or trigger the automatic start of the standby demineralized water pump. When supplying steam to external users, the low-pressure bypass is fully closed, and the high-pressure bypass pressure control is automatically activated to maintain stable reheater pressure. Except for the self-use heating feedwater and the portion used for self-use, all steam produced by the boiler is supplied to external users. The boiler combustion is put into automatic operation to ensure the internal heat balance of the boiler.

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