Pre-control method for suppressing load fluctuations in steam distribution system of full admission steam turbine

Abstract

The present application discloses a pre-control method for suppressing load fluctuations in a steam distribution system of a full admission steam turbine. In the method, by means of step-by-step modeling that integrates equipment mechanisms with on-site measurement data, a high-fidelity control valve flow-characteristic model for a full admission steam turbine is constructed, said model conforming to actual flow characteristics of control valves. Steam‑admission flow simulation for the steam turbine is performed when the control valves are in a double-sided synchronous steam admission working condition, a single-sided steam admission working condition and other non-synchronous steam admission conditions. The working statuses and flow capacities of the control valves in the double-sided synchronous steam admission working condition, a single-sided steam admission working condition and other non-synchronous steam admission conditions are comprehensively understood. According to the flow capacities of the control valves at different opening degrees in the single-side steam admission working condition, a safe operation manual of related regulation tests of a governing system is formulated, and an automatic control valve opening / closing function and an automatic control valve operating speed regulation function are added during full-stroke operation tests of main steam stop valves.

Description

A pre-control method for suppressing load fluctuations in the steam distribution system of a full-cycle steam turbine unit

[0001] This disclosure claims priority to the invention patent application filed on March 24, 2025, with application number 202510285656.0 and entitled "A Method for Pre-controlling Load Fluctuations in a Steam Distribution System for a Full-Circulation Steam Turbine Unit". Technical Field

[0002] This disclosure relates to a pre-control method for suppressing load fluctuations in the steam distribution system of a full-cycle steam turbine unit, belonging to the field of thermal power generation technology. Background Technology

[0003] For circumferential steam turbine units, main steam typically enters the turbine from the left and right sides, with one main steam valve and one control valve on each side (front and rear). The turbine's DEH system is responsible for unit start-up speed control and grid-connected power coordination control, and is designed with functional modules such as valve tightness testing, overspeed protection testing, and valve movement testing. The main steam valve full-stroke movement test procedure is as follows: taking main steam valve 2 as an example, first, close the control valve 2 on the same side at a rate of 0.1% / s; after control valve 2 is fully closed, perform a full-stroke movement test on main steam valve 2. After main steam valve 2 has completed its full stroke movement, control valve 2 on the same side is then opened at a rate of 0.1% / s and resumes normal operation. During the test, the DEH side load control mode is activated, and the opening of the control valve 1 on the opposite side is adjusted by changing the turbine command to maintain a constant unit load. For dual-side steam turbine units, when the main steam valve movement test is conducted, the operating state of each control valve is drastically different from the normal operating condition; this will cause changes in the turbine control valve flow characteristics, thus affecting the normal regulation of the unit load. Because the on-site test plan and related safety measures did not take this characteristic change into account, a certain full-cycle steam turbine unit experienced frequent and significant load fluctuations during periodic testing, triggering power oscillations multiple times and endangering the safe operation of the power grid. Meanwhile, during other speed control system adjustment tests conducted on-site, the steam distribution system was also frequently under the special condition of asynchronous steam inlet valves, also posing a safety risk of significant load fluctuations and triggering power oscillations.

[0004] The numerical correspondence between the turbine directive (FDEM) and the actual steam flow rate at the turbine inlet is generally referred to as the turbine control valve flow characteristics. Currently, research on the variation law of control valve flow characteristics during the full stroke operation test of the turbine main steam valve is still insufficient. It has failed to deeply analyze the dominant factors of unit load imbalance and triggering power oscillation events from a mechanistic perspective, and no targeted preventive measures have been developed. Summary of the Invention

[0005] The purpose of this disclosure is to prevent unit load imbalance and trigger power oscillation events, and to ensure the regular and safe conduct of relevant adjustment tests of the speed control system. This disclosure proposes a pre-control method for suppressing load fluctuations in the steam distribution system of a full-cycle steam turbine unit.

[0006] The technical solution disclosed herein is as follows: A pre-control method for suppressing load fluctuations in the steam distribution system of a full-circumference steam turbine unit. This method, through step-by-step modeling and integrating equipment mechanisms and on-site measured data, constructs a high-fidelity simulation model of the flow characteristics of the control valves in a full-circumference steam turbine unit, conforming to the actual flow characteristics of the control valves. Simulations of the turbine inlet steam flow under dual-sided synchronous steam inlet, single-sided steam inlet, and other asynchronous steam inlet conditions are conducted. The working status and flow capacity of the control valves under dual-sided synchronous steam inlet, single-sided steam inlet, and other asynchronous steam inlet conditions are comprehensively understood. Based on the flow capacity of the control valves at different opening degrees under single-sided steam inlet conditions, a safety operation manual for relevant adjustment tests of the speed control system is formulated. Automatic opening / closing functions and automatic adjustment of the control valve's action rate are added during the full-stroke activity test of the main steam valve, shortening the test time and significantly reducing the safety risks of unit load fluctuation amplitude and triggered power oscillations under special operating conditions of the speed control system, ensuring that test items are carried out safely and regularly in accordance with relevant national standards.

[0007] The method requires first adjusting the steam distribution parameters of the full-cycle inlet turbine DEH system through on-site testing to achieve a 1:1 correspondence between turbine commands and inlet steam flow percentage; and then plotting the DEH system steam distribution curve with turbine commands as the x-axis and valve opening as the y-axis. To prevent valve swaying at large openings, a 60% upper limit lockout is set for the valve opening.

[0008] The method first connects the inlet and outlet of a single main steam valve and a single regulating valve in series to form a steam distribution unit; then, it connects the inlet and outlet of both sides of the steam distribution unit in parallel and in series with the downstream flow passage to construct a steam distribution end model of a full-circuit steam inlet unit; then, by integrating equipment mechanism and field measurement data, a high-fidelity simulation model of the flow characteristics of the full-circuit steam inlet unit is constructed through step-by-step modeling, which conforms to the actual flow characteristics of the regulating valve. This allows for a comprehensive understanding of the operating status and flow capacity of the regulating valve under conditions of simultaneous steam inlet on both sides, single-side steam inlet, and other asynchronous steam inlet conditions.

[0009] The simulation modeling method is implemented in steps. In the first simulation step, simulation calculations are carried out based on the measured pressure loss values ​​of the main steam valve / control valve when fully open and the default flow characteristics of the control valve. During the simulation, parameters such as main steam pressure / main steam temperature / hot reheat temperature back pressure are kept constant, and the opening of the control valve is gradually and synchronously reduced by 1 / 2. The corresponding turbine inlet steam flow and first-stage pressure under different operating conditions are recorded.

[0010] The simulation modeling method is implemented in steps. In the second simulation step, the flow gain of valve 1 / 2 under each operating condition is calculated based on the percentage of steam inlet flow in each operating condition from the previous simulation. Then, the "valve opening - flow gain" characteristic of valve 1 / 2 from the field flow characteristic test is extracted. Based on the "flow gain" under the simulation conditions, the required valve opening value is calculated in reverse. Thus, the actual flow characteristics of the valve are obtained. The default flow characteristics of the valve in the original model are replaced with the actual flow characteristics, and the simulation calculation is carried out again. While keeping parameters such as main steam pressure, main steam temperature, and hot reheat temperature back pressure unchanged, the opening of valve 1 / 2 is gradually and synchronously reduced, and the corresponding turbine inlet steam flow and first-stage pressure under different operating conditions are recorded.

[0011] The simulation modeling method is implemented in steps. Based on the simulation results of the second step, the steam distribution curve of the control valve under the actual flow characteristics is plotted, and its consistency with the steam distribution curve of the DEH system is checked. If the valve opening deviation between the two under the same turbine command is greater than 2%, the above steps are repeated to conduct a third simulation until the deviation is less than 0.5%. Based on the actual flow characteristics of the control valve, the final version of the high-simulation model is determined.

[0012] The method is based on the final version of the high-fidelity model. It further assumes that the opening of valve 2 is fixed at different openings such as 0%, 5%, 10% and 20%, and valve 1 changes with the turbine command according to the steam distribution curve of the DEH system, so as to obtain the valve flow characteristics under different operating conditions.

[0013] In the method described, the valve 2 opening is fixed at 0%, which is the single-sided steam inlet condition. The turbine inlet steam flow rate is observed when the valve is at different openings under this condition, and the required valve opening under the single-sided steam inlet condition is determined accordingly during the full stroke operation test of the main steam valve.

[0014] The method utilizes the advantage of a high proportion of single-sided steam flow during the full-stroke operation test of the main steam valve, and adds automatic valve opening / closing function and automatic adjustment of valve action rate during the full-stroke operation test. Taking main steam valve 2 as an example, specific measures are listed below:

[0015] (1) Before the test, the unit was switched from coordinated control mode to DEH manual mode, and the primary frequency regulation function on the DEH side was deactivated; and the upper limit lock of 60% of the regulating valve opening was temporarily released.

[0016] (2) In the DEH system configuration, an automatic valve opening / closing function and an automatic valve action rate adjustment function are added during the main steam valve full-stroke activity test. When the main steam valve 2 activity test signal is triggered, the same-side valve 1 automatically closes from the test start opening to 0% opening, and the opposite-side valve 2 automatically opens from the test start opening to 100% opening; the action time of valves 1 and 2 is set to 20 seconds, and the action rate of valves 1 and 2 is automatically adjusted accordingly. When valve 1 closes to 0% opening, a signal for main steam valve 2 to close first and then open is issued. After main steam valve 2 completes the close-then-open action, the same-side valve 1 automatically opens from 0% opening to the test start opening at the same speed as before, and the opposite-side valve 2 also automatically closes from 100% opening to the test start opening at the same speed as before. After 20 seconds, a test end signal is triggered, and the unit resumes normal operation.

[0017] When conducting speed control system adjustment tests on-site, valve 1 / 2 is likely to be under asynchronous steam intake special conditions. In addition to disabling the primary frequency regulation function in advance, unnecessary DCS / DEH side automatic control functions should also be disabled as much as possible.

[0018] The beneficial effects of this disclosure are that by integrating equipment mechanisms and on-site measured data, and through step-by-step modeling, a comprehensive understanding of the working status and flow capacity of the regulating valve under conditions of simultaneous steam inlet on both sides, single-sided steam inlet, and other asynchronous steam inlet conditions can be achieved. Based on this, a safety operation manual for relevant adjustment tests of the speed control system has been developed, significantly reducing the safety risk of triggering power oscillations under special operating conditions of the speed control system, and ensuring that test items are carried out safely and regularly in accordance with relevant national standards. Attached Figure Description

[0019] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and are configured together with the description to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art will be able to derive other drawings from these drawings without inventive effort.

[0020] Figure 1 is a schematic diagram of the steam distribution section of the unit in an embodiment of this disclosure;

[0021] Figure 2 shows the inherent flow characteristics of the control valve of the unit in the embodiment of this disclosure;

[0022] Figure 3 shows the simulated steam distribution curve of the unit and the steam distribution curve of the DEH system in the embodiment of this disclosure.

[0023] Figure 4 shows the flow characteristics of valve 1 under different operating conditions of the unit in the embodiment of this disclosure. Detailed Implementation

[0024] The specific embodiments of this disclosure are shown in the figures. The technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to Figures 1-3.

[0025] The case unit is an ultra-supercritical, single-stage intermediate reheat, four-cylinder, four-exhaust, single-shaft, dual-backpressure, condensing steam turbine.

[0026] The unit adopts a full-circumferential steam inlet method, with main steam entering the turbine from the left and right sides. Each side has one main steam valve and one control valve, one at the front and one at the rear. In the DEH system, the upper limit of the control valve opening is 60%. Under the condition of both valves fully open, the main steam pressure, main steam temperature, hot reheat temperature, first-stage pressure, and back pressure are respectively 28.0 MPa / 600℃ / 620℃ / 27.58 MPa / 4.8 kPa.

[0027] This disclosure discloses a method for suppressing load fluctuations in a steam distribution system for a full-cycle steam turbine unit, comprising the following steps:

[0028] The proposed method employs step-by-step modeling, integrating equipment mechanisms and on-site measured data to construct a high-fidelity simulation model of the flow characteristics of the control valve in a full-circumference turbine unit, conforming to the actual flow characteristics of the control valve. Simulations of turbine inlet steam flow are conducted under conditions of simultaneous double-sided steam inlet, single-sided steam inlet, and other asynchronous steam inlet conditions. This provides a comprehensive understanding of the control valve's operating status and flow capacity under these conditions. Based on the flow capacity of the control valve at different opening degrees under single-sided steam inlet conditions, a safety operation manual for relevant adjustment tests of the speed control system is developed. Automatic opening / closing functions and automatic adjustment of the control valve's action rate are added during the full-stroke operation test of the main steam valve, shortening the test time and significantly reducing the safety risks of unit load fluctuations and triggered power oscillations under special operating conditions of the speed control system.

[0029] The method requires first adjusting the steam distribution parameters of the full-cycle inlet turbine DEH system through on-site testing to achieve a 1:1 correspondence between turbine commands and inlet steam flow percentage; and then plotting the DEH system steam distribution curve with turbine commands as the x-axis and valve opening as the y-axis. To prevent valve swaying at large openings, a 60% upper limit lockout is set for the valve opening.

[0030] The method first connects the inlet and outlet of a single main steam valve and a single regulating valve in series to form a steam distribution unit; then, it connects the inlet and outlet of both sides of the steam distribution unit in parallel and in series with the downstream flow passage to construct a steam distribution end model of a full-circuit steam inlet unit; then, by integrating equipment mechanism and field measurement data, a high-simulation model of the flow characteristics of the full-circuit steam inlet unit that conforms to the actual flow characteristics of the regulating valve is constructed through step-by-step modeling. This provides a comprehensive understanding of the operating status and flow capacity of the regulating valve under conditions of simultaneous steam inlet on both sides, single-side steam inlet, and other asynchronous steam inlet conditions, as shown in Figure 1.

[0031] The simulation modeling method is implemented in steps. In the first simulation step, simulation calculations are carried out based on the measured pressure loss values ​​of the main steam valve / control valve when fully open and the default flow characteristics of the control valve. During the simulation, parameters such as main steam pressure / main steam temperature / hot reheat temperature back pressure are kept constant, and the opening of the control valve is gradually and synchronously reduced by 1 / 2. The corresponding turbine inlet steam flow and first-stage pressure under different operating conditions are recorded.

[0032] The simulation modeling method is implemented in steps. In the second simulation step, the flow gain of valve 1 / 2 under each operating condition is calculated based on the percentage of steam inlet flow in each operating condition from the previous simulation. Then, the "valve opening - flow gain" characteristic of valve 1 / 2 in the field flow characteristic test is extracted. Based on the "flow gain" under the simulation operating condition, the required valve opening value is calculated in reverse. Thus, the actual flow characteristics of the valve are obtained, as shown in Figure 2. The default flow characteristics of the valve in the original model are replaced with the actual flow characteristics, and the simulation calculation is carried out again. The parameters such as main steam pressure, main steam temperature, and hot reheat temperature back pressure are kept unchanged. The opening of valve 1 / 2 is gradually and synchronously reduced, and the corresponding turbine inlet steam flow and first-stage pressure under different operating conditions are recorded.

[0033] The simulation modeling method described above is implemented in steps. Based on the simulation results of the second step, the steam distribution curve of the control valve under the actual flow characteristics is plotted, and its consistency with the steam distribution curve of the DEH system is checked. If the valve opening deviation between the two under the same turbine command is greater than 2%, a third simulation is carried out according to the simulation methods of the first and second steps until the deviation is less than 0.5%. Based on the actual flow characteristics of the control valve, the final version of the high-simulation model is determined, as shown in Figure 3.

[0034] The method is based on the final version of the high-simulation model. It further assumes that the opening of valve 2 is fixed at different openings such as 0%, 5%, 10% and 20%, and valve 1 changes with the turbine command according to the steam distribution curve of the DEH system. The valve flow characteristics under different operating conditions are obtained, as shown in Figure 4.

[0035] In the method described, the valve 2 opening is fixed at 0%, which is the single-sided steam inlet condition. The turbine inlet steam flow rate is observed under this condition when the valve is at different openings, and the required valve opening rate under the single-sided steam inlet condition is determined accordingly during the full-stroke operation test of the main steam valve. In the case unit, under the double-sided steam inlet condition, the pressure loss when valve 1 is fully open is 1.50%; under the single-sided steam inlet condition, the pressure loss when valve 1 is fully open is 3.78%. Unlike the nozzle-distributed steam unit, the single-sided steam inlet flow rate of the full-circumference steam inlet unit is 97.65% of the double-sided synchronous steam inlet flow rate, and the generator power reaches 97.83% of the same. As shown in Figure 4, in all conditions, including the single-sided steam inlet condition, the steam inlet flow rate is close to 100% when valve 1 is fully open. Even taking the upper limit of the valve opening of 60% in the case unit as an example, the steam inlet flow rate is 89.04% of the double-sided synchronous steam inlet flow rate, and the generator power reaches 89.79% of the same. To minimize load deviation, a 100% opening is most suitable for valve 1 under single-sided steam inlet conditions.

[0036] The method utilizes the advantage of a high proportion of single-sided steam flow during the full-stroke operation test of the main steam valve, and adds automatic valve opening / closing function and automatic adjustment of valve action rate during the full-stroke operation test. Taking main steam valve 2 as an example, specific measures are listed below:

[0037] (1) Before the test, the unit was switched from coordinated control mode to DEH manual mode, and the primary frequency regulation function on the DEH side was deactivated; and the upper limit lock of 60% of the regulating valve opening was temporarily released.

[0038] (2) In the DEH system configuration, an automatic valve opening / closing function and an automatic valve action rate adjustment function are added during the main steam valve full-stroke activity test. When the main steam valve 2 activity test signal is triggered, the same-side valve 1 automatically closes from the test start opening to 0% opening, and the opposite-side valve 2 automatically opens from the test start opening to 100% opening; the action time of valves 1 and 2 is set to 20 seconds, and the action rate of valves 1 and 2 is automatically adjusted accordingly. When valve 1 closes to 0% opening, a signal for main steam valve 2 to close first and then open is issued. After main steam valve 2 completes the close-then-open action, the same-side valve 1 automatically opens from 0% opening to the test start opening at the same speed as before, and the opposite-side valve 2 also automatically closes from 100% opening to the test start opening at the same speed as before. After 20 seconds, a test end signal is triggered, and the unit resumes normal operation.

[0039] When conducting on-site speed control system adjustment tests, valve 1 / 2 is likely to be under non-synchronous steam intake special operating conditions. In addition to disabling the primary frequency regulation function in advance, unnecessary DCS / DEH side automatic control functions should also be disabled as much as possible.

[0040] The above provides a detailed description of the method for suppressing load fluctuations in the steam distribution system of a full-cycle steam turbine unit provided by this disclosure. Specific examples in this embodiment illustrate the principles and implementation methods of this disclosure. The descriptions of the above embodiments are merely for the purpose of helping to understand the method and its core ideas. It should be noted that those skilled in the art can make various improvements and modifications to this disclosure without departing from its principles, and these improvements and modifications also fall within the protection scope of the claims of this disclosure.

Claims

1. A pre-control method for suppressing load fluctuations in the steam distribution system of a full-cycle steam turbine unit, wherein, The method includes the following steps: Step 1: Through on-site testing, the steam distribution parameters of the DEH system of the full-circle steam turbine unit are adjusted to achieve a 1:1 correspondence between the turbine command and the percentage of steam flow; and the steam distribution curve of the DEH system is plotted with the turbine command as the horizontal axis and the valve opening as the vertical axis. Step 2: Through step-by-step modeling, integrating equipment mechanism and on-site measured data, a high-fidelity simulation model of the flow characteristics of the full-circumference steam turbine control valve is constructed, which conforms to the actual flow characteristics of the control valve. Step 3: Conduct simulation work on the turbine inlet steam flow under the conditions of synchronous steam inlet on both sides, single-side steam inlet and other asynchronous steam inlet conditions to obtain a high-fidelity simulation model; Step 4: Based on the high-fidelity model obtained in Step 3, test the working condition and flow capacity of the regulating valve under the conditions of simultaneous steam inlet on both sides, single steam inlet on one side and other asynchronous steam inlet conditions. Based on the flow capacity of the regulating valve under different openings in the single steam inlet condition, formulate relevant adjustment strategies for the speed control system. In step 1, to prevent the control door from swaying when it is fully open, a 60% upper limit lock is set for the control door opening. Step 2, which describes constructing a high-fidelity model of the flow characteristics of the turbine control valve that conforms to the actual flow characteristics of the control valve, specifically includes the following steps: First, the inlet and outlet of a single main steam valve and a single regulating valve are connected in series to form a steam distribution unit; then, the inlet and outlet of the two steam distribution units are connected in parallel to each other and connected in series with the downstream flow section to construct the steam distribution end model of the full-circuit steam turbine unit. Then, by integrating the equipment mechanism and on-site measured data, a high-simulation model of the full-circumference steam turbine flow characteristics that conforms to the actual flow characteristics of the control valve is constructed through step-by-step modeling.

2. The method of claim 1, wherein, Step 3 includes the following steps: Step 3.1: Based on the measured pressure loss of the main steam valve / regulating valve when fully open and the default flow characteristics of the regulating valve, conduct simulation calculations. During the simulation, keep the parameters of main steam pressure / main steam temperature / reheat temperature / back pressure constant, and gradually and synchronously reduce the opening of the first regulating valve or the second regulating valve. Record the corresponding turbine inlet steam flow and first-stage pressure under different operating conditions. Step 3.2: Based on the percentage of steam flow in each operating condition in the previous simulation, calculate the flow gain of the first or second regulating valve under each operating condition; then, extract the "valve opening - flow gain" characteristic of the first or second regulating valve from the field flow characteristic test, and calculate the required value of the regulating valve opening based on the "flow gain" under the simulation conditions; then, obtain the actual flow characteristics of the regulating valve; replace the default flow characteristics of the regulating valve in Step 3.1 with the actual flow characteristics of the regulating valve, and perform the simulation calculation again; keep the main steam pressure / main steam temperature / reheat temperature / back pressure constant, and gradually and synchronously reduce the opening of the first or second regulating valve, and record the corresponding turbine inlet steam flow and first stage pressure under different operating conditions; Step 3.2: Plot the steam distribution curve of the control valve under the actual flow characteristics, and check whether it is basically consistent with the steam distribution curve of the DEH system obtained in Step 1. If the valve opening deviation is greater than 2% under the same turbine command, repeat Step 3.1-Step 3.2 until the deviation is less than the set threshold. Based on the actual flow characteristics of the control valve, determine the final version of the high-simulation model.

3. The method for suppressing load fluctuations in a full-cycle steam distribution system of a turbine generator unit according to claim 2, wherein, The set threshold for the deviation is 0.5%.

4. The method of claim 2 or 3, wherein, In step 4, the opening of the second regulating valve is fixed at different openings of 0%, 5%, 10% and 20%, respectively. The first regulating valve changes according to the steam distribution curve of the DEH system and the turbine command to obtain the regulating valve flow characteristics under different operating conditions.

5. The method for suppressing load fluctuation in advance in a steam distribution system of a full-peripheral admission turbine unit according to claim 4, wherein In step 4, the second regulating valve opening is fixed at 0%, which is the single-sided steam inlet condition. The turbine steam inlet flow rate is observed when the regulating valve is at different openings under this condition. Based on this, the required opening of the regulating valve under the single-sided steam inlet condition is determined during the full stroke activity test of the main steam valve. Then, based on the flow capacity of the regulating valve under the single-sided steam inlet condition at different openings, the relevant adjustment strategy of the speed control system is formulated.

6. The method for suppressing load fluctuations in a full-cycle steam distribution system of a turbine generator unit according to claim 5, wherein, The established speed control system adjustment strategies include: (1) Before the test, the unit was switched from coordinated control mode to DEH manual mode, and the primary frequency regulation function on the DEH side was deactivated; and the upper limit lock of 60% of the regulating valve opening was temporarily released. (2) In the DEH system configuration, add the function of automatic opening / closing of the control valve and the function of automatic adjustment of the control valve action rate during the full stroke activity test of the main steam valve.

7. A method for suppressing load fluctuations in a full-cycle steam distribution system of a turbine generator unit according to claim 6, wherein, The automatic opening / closing function of the control valve and the automatic adjustment of the control valve action rate during the full stroke activity test of the main steam valve include: when the main steam valve activity test signal is triggered, the first control valve on the same side automatically closes from the test start opening to 0% opening, and the second control valve on the opposite side automatically opens from the test start opening to 100% opening; the action time of the first or second control valve is set to 20 seconds, and the action rate of the first or second control valve is automatically adjusted accordingly; when the first control valve closes to 0% opening, a main steam valve close-then-open signal is issued; after the main steam valve completes the close-then-open action, the first control valve on the same side automatically opens from 0% opening to the test start opening at the same speed as before, and the second control valve on the opposite side also automatically closes from 100% opening to the test start opening at the same speed as before; after 20 seconds, a test end signal is triggered, and the unit resumes normal operation.

8. The method for suppressing load fluctuations in a full-cycle steam distribution system of a turbine generator unit according to claim 1, wherein, When conducting speed control system adjustment tests on-site, the first or second regulating gate needs to be deactivated from the frequency regulation function and the automatic control function on the DCS / DEH side.

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