A sliding pressure control method and system for a full - admission steam turbine

Abstract

The present invention discloses a sliding pressure control method and system for a full-arc admission steam turbine, relating to the field of sliding pressure control. The method includes: controlling the main regulating steam valve and the auxiliary regulating steam valve in the full-arc admission steam turbine to be in an overlapping opening regulation mode; the overlapping opening regulation mode is that when the opening of the main regulating steam valve reaches a first set ratio, the auxiliary regulating steam valve starts to open, and when the main regulating steam valve is fully open, the opening of the auxiliary regulating steam valve reaches a second set ratio; determining the sliding pressure load range of the full-arc admission steam turbine; within the overlapping opening regulation mode and the sliding pressure load range, calculating the target value of the main steam pressure of the full-arc admission steam turbine based on the real-time unit load and the real-time operating back pressure; the target value of the main steam pressure is used to achieve the sliding pressure control of the main regulating steam valve. The present invention can not only ensure that the unit has sufficient primary frequency regulation ability, but also reduce the cost of the unit operating at sliding pressure.

Description

Technical Field

[0001] The present invention relates to the field of sliding pressure control, and particularly to a sliding pressure control method and system for a full-arc admission steam turbine unit. Background Art

[0002] The difference between a non-governing-stage full-arc admission steam turbine unit and a governing-stage partial-arc admission steam turbine unit lies in that the governing-stage partial-arc admission steam turbine unit has 4 to 6 governing valves, while the non-governing-stage full-arc admission steam turbine unit is only equipped with two main governing valves, and the same-opening regulation mode is adopted in the design. Therefore, the sliding pressure operation of this type of unit at part load is essentially a single-valve sliding pressure mode, that is, the x% + x% mode: the two main governing valves throttle and slide pressure with the same opening, and x% represents the opening of the main governing valve. In addition to the main governing valves, although the non-governing-stage full-arc admission steam turbine unit is designed with 2 supplementary steam valves, they usually only participate in regulation when the unit is overloaded and do not have the primary frequency modulation ability at part load. The non-governing-stage full-arc admission steam turbine unit is designed with a 100% + 100% opening sliding pressure mode. However, considering that the unit must have the primary frequency modulation ability, the two main governing valves are closed to a certain opening (usually 40% to 50%) to exchange throttling loss for frequency modulation ability. Obviously, for such a full-arc admission steam turbine unit, the steam distribution mode is suitable for the unit to carry the base load, and the economy of the unit will decrease significantly at part load, especially when the unit is operating at deep peak shaving, which has a greater impact on the economy of the unit and leads to a significant increase in the unit cost. Summary of the Invention

[0003] Based on this, the embodiments of the present invention provide a sliding pressure control method and system for a full-arc admission steam turbine unit, which can not only ensure that the unit has sufficient primary frequency modulation ability but also reduce the cost of the unit's sliding pressure operation.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] A sliding pressure control method for a full-arc admission steam turbine unit, comprising:

[0006] Controlling the main governing valve and the auxiliary governing valve in the full-arc admission steam turbine unit to be in an overlapping opening regulation mode; the overlapping opening regulation mode is that when the opening of the main governing valve reaches a first set ratio, the auxiliary governing valve starts to open, and when the main governing valve is fully open, the opening of the auxiliary governing valve reaches a second set ratio; the first set ratio is greater than the second set ratio;

[0007] Determining the sliding pressure load range of the full-arc admission steam turbine unit;

[0008] Obtaining the real-time unit load and the real-time operating back pressure of the full-arc admission steam turbine unit;

[0009] In the overlapping opening adjustment mode and within the sliding pressure load range, the main steam pressure target value of the full-cycle steam inlet unit is calculated based on the real-time unit load and the real-time operating back pressure; the main steam pressure target value is used to achieve sliding pressure control of the main regulating steam valve.

[0010] Optionally, in the overlap opening adjustment mode and within the sliding pressure load range, calculating the main steam pressure target value of the full-cycle steam inlet unit based on the real-time unit load and the real-time operating back pressure specifically includes:

[0011] Use the sliding pressure curve test method to determine the sliding pressure curve related to the unit load;

[0012] Determine a sliding pressure curve related to the unit back pressure from the influence curve of the unit back pressure change on the unit load and the sliding pressure curve related to the unit load;

[0013] Determine a sliding pressure curve of a phase-changing valve according to the sliding pressure curve related to the unit load and the sliding pressure curve related to the unit back pressure; the sliding pressure curve of the phase-changing valve is the sliding pressure curve of the unit under partial load;

[0014] The main steam pressure target value of the full-cycle steam inlet unit is calculated according to the real-time unit load, the real-time operating back pressure and the variable phase forward valve sliding pressure curve.

[0015] Optionally, the phase-changing valve sliding pressure curve is specifically:

[0016] P0=P01(N+▽N);

[0017] Among them, P0 represents the target value of the main steam pressure of the full-cycle steam inlet unit output by the variable phase valve sliding pressure curve; P01 represents the pressure output by the sliding pressure curve related to the unit load; N represents the real-time unit load; ▽N represents the slight increase in unit power; ▽N=f(Pc-Pc0), f represents the influence curve of the unit back pressure change on the unit load; Pc represents the real-time operating back pressure; Pc0 represents the set operating back pressure.

[0018] Optionally, the first setting ratio is 93%; the second setting ratio ranges from 5% to 8%.

[0019] Optionally, the sliding pressure load ranges from 50% to 100% of the rated load.

[0020] The present invention also provides a full-cycle steam inlet unit sliding pressure control system, comprising:

[0021] The opening adjustment mode control module is used to control the main control valve and the auxiliary control valve in the full arc admission steam turbine to be in the overlapping opening adjustment mode; the overlapping opening adjustment mode means that when the opening of the main control valve reaches the first set ratio, the auxiliary control valve starts to open, and when the main control valve is fully open, the opening of the auxiliary control valve reaches the second set ratio; the first set ratio is greater than the second set ratio;

[0022] The sliding pressure load range determination module is used to determine the sliding pressure load range of the full arc admission steam turbine;

[0023] The data acquisition module is used to acquire the real-time unit load and the real-time operating back pressure of the full arc admission steam turbine;

[0024] The sliding pressure control module is used to calculate the main steam pressure target value of the full arc admission steam turbine based on the real-time unit load and the real-time operating back pressure in the overlapping opening adjustment mode and within the sliding pressure load range; the main steam pressure target value is used to realize the sliding pressure control of the main control valve.

[0025] Optionally, the sliding pressure control module specifically includes:

[0026] The first curve determination unit is used to determine the sliding pressure curve related to the unit load by using the sliding pressure curve test method;

[0027] The second curve determination unit is used to determine the sliding pressure curve related to the unit back pressure from the influence curve of the unit back pressure change on the unit load and the sliding pressure curve related to the unit load;

[0028] The variable-phase valve following sliding pressure curve determination unit is used to determine the variable-phase valve following sliding pressure curve according to the sliding pressure curve related to the unit load and the sliding pressure curve related to the unit back pressure; the variable-phase valve following sliding pressure curve is the sliding pressure curve of the unit under partial load;

[0029] The pressure target value determination unit is used to calculate the main steam pressure target value of the full arc admission steam turbine according to the real-time unit load, the real-time operating back pressure and the variable-phase valve following sliding pressure curve.

[0030] Optionally, the variable-phase valve following sliding pressure curve in the variable-phase valve following sliding pressure curve determination unit is specifically:

[0031] P0 = P01(N + ▽N);

[0032] Among them, P0 represents the main steam pressure target value of the full-arc admission unit output by the variable-phase throttle valve sliding pressure curve; P01 represents the pressure output by the sliding pressure curve related to the unit load; N represents the real-time unit load; ▽N represents the unit incremental power; ▽N = f(Pc - Pc0), where f represents the influence curve of the unit back pressure change on the unit load; Pc represents the real-time operating back pressure; Pc0 represents the set operating back pressure.

[0033] Optionally, the first set ratio in the opening adjustment mode control module is 93%; the range of the second set ratio is 5% - 8%.

[0034] Optionally, the sliding pressure load range in the sliding pressure load range determination module is 50% - 100% of the rated load.

[0035] Compared with the prior art, the beneficial effects of the present invention are:

[0036] The embodiment of the present invention provides a sliding pressure control method and system for a full-arc admission unit. First, control the main regulating valve and the auxiliary regulating valve in the full-arc admission unit to be in the overlapping opening adjustment mode; the overlapping opening adjustment mode is that when the opening of the main regulating valve reaches the first set ratio, the auxiliary regulating valve starts to open, and when the main regulating valve is fully open, the opening of the auxiliary regulating valve reaches the second set ratio; within the overlapping opening adjustment mode and the sliding pressure load range, calculate the main steam pressure target value of the full-arc admission unit based on the real-time unit load and the real-time operating back pressure to achieve the sliding pressure control of the main regulating valve. The present invention realizes variable-phase throttle valve sliding pressure control based on the overlapping opening adjustment mode. Compared with the single-valve sliding pressure control achieved based on the same-opening, same-closing, and same-opening degree mode of two regulating valves, the present invention not only ensures that the unit has sufficient primary frequency modulation ability but also can reduce the cost of the unit operating under sliding pressure. Description of the Drawings

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0038] Figure 1 It is the flowchart of the sliding pressure control method for the full-arc admission unit provided by the embodiment of the present invention;

[0039] Figure 2 It is the structural diagram of the sliding pressure control system for the full-arc admission unit provided by the embodiment of the present invention. Detailed Embodiments

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] See Figure 1 , the throttle control method for the full arc admission steam turbine in this embodiment includes:

[0043] Step 101: Control the main governing valve and the auxiliary governing valve in the full arc admission steam turbine to be in an overlapping opening adjustment mode; the overlapping opening adjustment mode is that when the opening of the main governing valve reaches the first set ratio, the auxiliary governing valve starts to open, and when the main governing valve is fully open, the opening of the auxiliary governing valve reaches the second set ratio; the first set ratio is greater than the second set ratio.

[0044] The first set ratio is 93%; the range of the second set ratio is 5% - 8%.

[0045] Step 102: Determine the sliding pressure load range of the full arc admission steam turbine. The sliding pressure load range is 50% - 100% of the rated load.

[0046] Step 103: Obtain the real-time unit load and the real-time operating back pressure of the full arc admission steam turbine.

[0047] Step 104: Calculate the target value of the main steam pressure of the full arc admission steam turbine based on the real-time unit load and the real-time operating back pressure within the overlapping opening adjustment mode and the sliding pressure load range; the target value of the main steam pressure is used to achieve the sliding pressure control of the main governing valve.

[0048] Among them, step 104 specifically includes:

[0049] 1) Use the sliding pressure curve test method to determine the sliding pressure curve related to the unit load.

[0050] 2) Determine the sliding pressure curve related to the unit back pressure from the influence curve of the unit back pressure change on the unit load and the sliding pressure curve related to the unit load.

[0051] 3) Determine the variable-phase valve following sliding pressure curve according to the sliding pressure curve related to the unit load and the sliding pressure curve related to the unit back pressure; the variable-phase valve following sliding pressure curve is the sliding pressure curve of the unit under partial load.

[0052] The transformed valve sliding pressure curve is specifically as follows:

[0053] P0 = P01(N + ▽N);

[0054] Wherein, P0 represents the main steam pressure target value of the full-arc admission unit output by the transformed valve sliding pressure curve; P01 represents the pressure output by the sliding pressure curve related to the unit load; N represents the real-time unit load; ▽N represents the unit incremental power; ▽N = f(Pc - Pc0), f represents the influence curve of the unit back pressure change on the unit load; Pc represents the real-time operating back pressure; Pc0 represents the set operating back pressure.

[0055] 4) Calculate the main steam pressure target value of the full-arc admission unit according to the real-time unit load, the real-time operating back pressure and the transformed valve sliding pressure curve.

[0056] In practical applications, the above-mentioned sliding pressure control method for the full-arc admission unit is implemented based on the unit digital electro-hydraulic control system (Digital Electro-Hydraulic Control System, DEH), and its specific implementation process is as follows:

[0057] (1) Add a single-valve (single control valve) control function logic module in the unit digital electro-hydraulic control system.

[0058] Currently, the sliding pressure of the full-arc admission unit is in the single-valve sliding pressure mode, that is, when sliding pressure operation, the two control valves open and close at the same time with the same opening. The transformed valve sliding pressure proposed in this embodiment is based on the different openings of the two control valves. Each control valve must be able to control the opening separately. This function requires adding a single-valve control logic in the DEH. The purpose is to meet the requirement of separately controlling the control valves for the subsequent mentioned transformed valve sliding pressure.

[0059] (2) Set the main control valve and the auxiliary control valve of the unit for the two control valves (control valves) of the unit in the added single-valve control function logic module (for example, the A control valve is the main control valve and the B control valve is the auxiliary control valve; vice versa, such as the B control valve is the control valve and the A control valve is the auxiliary control valve).

[0060] (3) After completing the setting in (2), in order to ensure that when the full-arc admission unit transfers from the original single-valve sliding pressure mode to the transformed valve sliding pressure mode proposed in this embodiment, the main steam flow rate of the unit suddenly changes, causing safety problems of the unit, it is necessary to adjust the overlap of the two control valves to 5% - 8% (for example, if the A control valve is the main control valve and the B control valve is the auxiliary control valve, when the opening of the A control valve reaches 93%, the B control valve starts to open, and when the A control valve is fully open, the B control valve has an opening of 5% - 8%) to ensure the smooth transition of the flow rate of the two control valves.

[0061] (4) After the overlap degree of the two governing valves is set, the overlap degree obtained from the above steps serves as the basis for the following sliding pressure module to ensure the overlap degree of the subsequent two governing valves. The subsequent variable-phase sequential sliding pressure module conducts sliding pressure control for a specific governing valve. However, during the sliding pressure control process of a single governing valve, the overlap degree between the other governing valve and the currently controlled governing valve is ensured (similar to the control process of the active and driven). Based on the original single-valve sliding pressure module of the unit distributed control system DCS, a variable-phase sequential valve sliding pressure module is added.

[0062] (5) Set the unit sliding pressure load range in the variable-phase sequential valve sliding pressure module to 50% - 100% of the rated load.

[0063] The unit sliding pressure operation cannot be carried out within the full load range. Generally, in the professional field, the process from turbine startup to full load is called the "constant - sliding - constant" mode, that is, the constant pressure section from 0 to 50% load, the sliding pressure section from 50% to 90% load, and then the constant pressure section from 90% to 100% load. The unit sliding pressure load range in this embodiment is defined as 50% - 100% of the rated load.

[0064] (6) The unit needs to achieve the function of operating with different main steam pressures at different loads under automatic control conditions. The thermal power plant adopts a two - level mode to achieve this: the real - time target value generation function + the function of automatically executing according to the target value. The sliding pressure module completes the first function, and the coordinated control CCS in the plant distributed control system DCS completes the second function. Whether it is single - valve sliding pressure or sequential valve sliding pressure, it is to implement the first function with different technologies or logics. Therefore, essentially, the sliding pressure module is a real - time unit main steam pressure target value generator.

[0065] The sliding pressure module in this embodiment is a variable - phase sequential valve sliding pressure module. The method for the variable - phase sequential valve sliding pressure module to generate the unit main steam pressure target value: taking the unit load as the independent variable, the corresponding main steam pressure obtained by looking up or calculating through the sliding pressure curve (essentially the relationship curve of main steam pressure to load) obtained from tests or provided by the manufacturer is the unit real - time main steam pressure target value. Specifically: the variable - phase sequential valve sliding pressure module conducts sliding pressure according to the given sliding pressure curve. The determination method of the sliding pressure curve is as follows:

[0066] Different from the conventional sliding pressure curve which is only determined by the unit load, the variable - phase sequential valve sliding pressure curve consists of a sliding pressure curve related to the unit load and a sliding pressure curve related to the unit back pressure:

[0067] P0 = P01(N) + P02(Pc)

[0068] Wherein: P0 represents the main steam pressure target value of the full-arc admission unit output by the variable valve sliding pressure curve; P01(N) is the pressure output by the sliding pressure curve related to the unit load when the input of the sliding pressure curve related to the unit load is the real-time unit load N; P01 is obtained by the conventional sliding pressure curve test method; P02(Pc) is the pressure output by the sliding pressure curve related to the unit back pressure when the input of the sliding pressure curve related to the unit back pressure is the real-time operating back pressure Pc; P02 can be obtained from the curve of the influence of the unit back pressure change on the load (provided by the manufacturer when the equipment leaves the factory), and then calculated using P01(N).

[0069] Because the curve of the influence of the unit back pressure change on the load can be expressed as ▽N = f(Pc - Pc0), that is, the incremental power ▽N of the unit generated by the difference between the actual operating back pressure Pc and the set operating back pressure Pc0 of the unit, so the variable valve sliding pressure curve can ultimately be expressed as:

[0070] P0 = P01(N + ▽N).

[0071] (7) After completing the above work, the actual unit operates in the variable valve sliding pressure mode as follows: The variable valve sliding pressure module calculates the corresponding sliding pressure main steam pressure target value P0 according to the real-time unit load N and the real-time operating back pressure Pc, and sends this target value to the unit coordinated control system CCS, thereby completing the automatic control operation of the variable valve sliding pressure.

[0072] (8) Since the economy of the valve sliding pressure is necessarily better than that of the single valve sliding pressure, the operating economy of the full-arc admission unit with variable valve sliding pressure given in this embodiment is necessarily better than the original single valve sliding pressure economy.

[0073] Finally, through theoretical and numerous on-site tests, it is verified that: the economy of the valve sliding pressure is necessarily better than that of the single valve sliding pressure. Because the variable sliding pressure is essentially a valve mode, the economy of the 100% + y% sliding pressure mode must be better than that of the x% + x% single valve sliding pressure mode, which can significantly improve the operating economy of the unit. In the 100% + y% sliding pressure mode, 100% represents the opening degree (fully open) of the main regulating steam valve, and y% represents the opening degree of the auxiliary regulating steam valve; in the x% + x% single valve sliding pressure mode, both are main regulating valves, and the opening degrees of the two main regulating valves are both x%. This embodiment realizes that the full-arc admission unit can ensure that the unit has sufficient primary frequency modulation ability under partial load, and at the same time can improve the sliding pressure operating economy of the unit and reduce costs.

[0074] The present invention also provides a sliding pressure control system for a full-arc admission unit, see Figure 2 , the system includes:

[0075] The opening degree adjustment mode control module 201 is used to control the main regulating steam valve and the auxiliary regulating steam valve in the full arc admission steam turbine to be in the overlapping opening degree adjustment mode; the overlapping opening degree adjustment mode means that when the opening degree of the main regulating steam valve reaches the first set ratio, the auxiliary regulating steam valve starts to open, and when the main regulating steam valve is fully open, the opening degree of the auxiliary regulating steam valve reaches the second set ratio; the first set ratio is greater than the second set ratio.

[0076] The sliding pressure load range determination module 202 is used to determine the sliding pressure load range of the full arc admission steam turbine.

[0077] The data acquisition module 203 is used to acquire the real-time unit load and the real-time operating back pressure of the full arc admission steam turbine.

[0078] The sliding pressure control module 204 is used to calculate the target value of the main steam pressure of the full arc admission steam turbine based on the real-time unit load and the real-time operating back pressure in the overlapping opening degree adjustment mode and within the sliding pressure load range; the target value of the main steam pressure is used to realize the sliding pressure control of the main regulating steam valve.

[0079] In one example, the sliding pressure control module 204 specifically includes:

[0080] The first curve determination unit is used to determine the sliding pressure curve related to the unit load by using the sliding pressure curve test method.

[0081] The second curve determination unit is used to determine the sliding pressure curve related to the unit back pressure from the influence curve of the unit back pressure change on the unit load and the sliding pressure curve related to the unit load.

[0082] The variable-phase valve following sliding pressure curve determination unit is used to determine the variable-phase valve following sliding pressure curve according to the sliding pressure curve related to the unit load and the sliding pressure curve related to the unit back pressure; the variable-phase valve following sliding pressure curve is the sliding pressure curve of the unit under partial load.

[0083] The target pressure value determination unit is used to calculate the target value of the main steam pressure of the full arc admission steam turbine according to the real-time unit load, the real-time operating back pressure and the variable-phase valve following sliding pressure curve.

[0084] In one example, the variable-phase valve following sliding pressure curve in the variable-phase valve following sliding pressure curve determination unit is specifically:

[0085] P0 = P01(N + ▽N);

[0086] Among them, P0 represents the main steam pressure target value of the full-arc admission unit output by the variable-phase throttle valve sliding pressure curve; P01 represents the pressure output by the sliding pressure curve related to the unit load; N represents the real-time unit load; ▽N represents the unit's incremental power; ▽N = f(Pc - Pc0), where f represents the influence curve of the unit back pressure change on the unit load; Pc represents the real-time operating back pressure; Pc0 represents the set operating back pressure.

[0087] In one example, the first set ratio in the opening adjustment mode control module is 93%; the range of the second set ratio is 5% - 8%.

[0088] In one example, the sliding pressure load range in the sliding pressure load range determination module is 50% - 100% of the rated load.

[0089] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. The same or similar parts among the embodiments can be referred to each other. For the system disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the description of the method part.

[0090] Specific examples are used in this article to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, based on the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A sliding pressure control method for a full - admission steam turbine, characterized in that, include: Control the main regulating steam valve and the auxiliary regulating steam valve in the full-cycle steam inlet unit to be in overlapping opening adjustment mode; The overlapping opening adjustment mode is that when the opening of the main regulating steam valve reaches a first set ratio, the auxiliary regulating steam valve starts to open, and when the main regulating steam valve is fully opened, the opening of the auxiliary regulating steam valve reaches a second set ratio; The first set ratio is greater than the second set ratio; Determine the sliding pressure load range of the full-cycle steam inlet unit; Obtaining the real-time unit load and real-time operating back pressure of the full-cycle steam inlet unit; In the overlapping opening adjustment mode and within the sliding pressure load range, the main steam pressure target value of the full-cycle steam inlet unit is calculated based on the real-time unit load and the real-time operating back pressure; the main steam pressure target value is used to achieve sliding pressure control of the main regulating steam valve.

2. The sliding pressure control method for a full - circumference steam admission unit according to claim 1, characterized in that, The calculation of the main steam pressure target value of the full-cycle steam inlet unit based on the real-time unit load and the real-time operating back pressure in the overlap opening adjustment mode and within the sliding pressure load range specifically includes: Use the sliding pressure curve test method to determine the sliding pressure curve related to the unit load; Determine a sliding pressure curve related to the unit back pressure from the influence curve of the unit back pressure change on the unit load and the sliding pressure curve related to the unit load; Determine a sliding pressure curve of a phase-changing valve according to the sliding pressure curve related to the unit load and the sliding pressure curve related to the unit back pressure; the sliding pressure curve of the phase-changing valve is the sliding pressure curve of the unit under partial load; The main steam pressure target value of the full-cycle steam inlet unit is calculated according to the real-time unit load, the real-time operating back pressure and the variable phase forward valve sliding pressure curve.

3. A sliding pressure control method for a full - circumference steam inlet steam turbine according to claim 2, characterized in that, The phase-changing valve sliding pressure curve is specifically: P0=P01(N+▽N); Among them, P0 represents the target value of the main steam pressure of the full-cycle steam inlet unit output by the variable phase valve sliding pressure curve; P01 represents the pressure output by the sliding pressure curve related to the unit load; N represents the real-time unit load; ▽N represents the slight increase in unit power; ▽N=f(Pc-Pc0), f represents the influence curve of the unit back pressure change on the unit load; Pc represents the real-time operating back pressure; Pc0 represents the set operating back pressure.

4. A sliding pressure control method for a full - circumference steam inlet steam turbine according to claim 1, characterized in that, The first setting ratio is 93%; the second setting ratio ranges from 5% to 8%.

5. A sliding pressure control method for a full - circumference steam inlet unit according to claim 1, characterized in that, The sliding pressure load range is 50%-100% of the rated load.

6. A sliding pressure control system for a full-arc admission steam turbine, characterized in that, include: The opening adjustment mode control module is used to control the main regulating steam valve and the auxiliary regulating steam valve in the full-cycle steam inlet unit to be in the overlapping opening adjustment mode; The overlapping opening adjustment mode is that when the opening of the main regulating steam valve reaches a first set ratio, the auxiliary regulating steam valve starts to open, and when the main regulating steam valve is fully opened, the opening of the auxiliary regulating steam valve reaches a second set ratio; The first set ratio is greater than the second set ratio; A sliding pressure load range determination module, used to determine the sliding pressure load range of the full-cycle steam inlet unit; A data acquisition module, used to obtain the real-time unit load and real-time operating back pressure of the full-cycle steam inlet unit; The sliding pressure control module is used to calculate the target value of the main steam pressure of the full arc admission steam turbine based on the real-time unit load and the real-time operating back pressure within the overlapping opening adjustment mode and the sliding pressure load range; the target value of the main steam pressure is used to achieve the sliding pressure control of the main regulating steam valve.

7. A sliding pressure control system for a full - circumference steam admission steam turbine according to claim 6, characterized in that, The sliding pressure control module specifically includes: The first curve determination unit is used to determine the sliding pressure curve related to the unit load by using the sliding pressure curve test method; The second curve determination unit is used to determine the sliding pressure curve related to the unit back pressure from the influence curve of the unit back pressure change on the unit load and the sliding pressure curve related to the unit load; The variable-phase valve sliding pressure curve determination unit is used to determine the variable-phase valve sliding pressure curve according to the sliding pressure curve related to the unit load and the sliding pressure curve related to the unit back pressure; the variable-phase valve sliding pressure curve is the sliding pressure curve of the unit at part load; The pressure target value determination unit is used to calculate the target value of the main steam pressure of the full arc admission steam turbine according to the real-time unit load, the real-time operating back pressure and the variable-phase valve sliding pressure curve.

8. A sliding pressure control system for a full - circumference steam admission steam turbine according to claim 7, characterized in that, The variable-phase valve sliding pressure curve in the variable-phase valve sliding pressure curve determination unit is specifically: P0 = P01(N + ▽N); Wherein, P0 represents the target value of the main steam pressure of the full arc admission steam turbine output by the variable-phase valve sliding pressure curve; P01 represents the pressure output by the sliding pressure curve related to the unit load; N represents the real-time unit load; ▽N represents the unit incremental power; ▽N = f(Pc - Pc0), f represents the influence curve of the unit back pressure change on the unit load; Pc represents the real-time operating back pressure; Pc0 represents the set operating back pressure.

9. A sliding pressure control system for a full - circumference steam admission steam turbine according to claim 6, characterized in that, The first set ratio in the opening adjustment mode control module is 93%; the range of the second set ratio is 5% - 8%.

10. A sliding pressure control system for a full - circumferential steam admission steam turbine according to claim 6, characterized in that, The sliding pressure load range in the sliding pressure load range determination module is 50% - 100% of the rated load.

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