A high-pressure heater upper end difference adjusting system and control method

Abstract

This invention discloses a control method for a high-pressure heater upper differential pressure regulation system, including an upper differential pressure superposition module, a variable load fast adjustment control module, and an inlet steam pressure lockout reduction module. The high-pressure heater upper differential pressure regulation system and control method of this invention are easy to use. When the unit load changes, rapid closed-loop automatic control of the regulating valve is achieved through steam pressure regulation PID to ensure that the inlet steam pressure meets the design economic parameter requirements. When the unit load is stable, the upper differential pressure meets the design economic parameter requirements through superposition calculation of inlet steam regulating valve commands.

Description

Technical Field

[0001] This invention relates to the field of high-pressure heater technology, and specifically to a high-pressure heater upper end differential pressure adjustment system and control method. Background Technology

[0002] In thermal power plants, high-pressure heaters function by using a portion of the extracted steam from the turbine to heat feedwater. Their heat transfer performance directly impacts the unit's economy and safety. Therefore, improving the heat transfer efficiency of high-pressure heaters and maximizing the use of waste heat to heat feedwater is a crucial measure for achieving efficient energy utilization.

[0003] The upper differential pressure and the heat transfer efficiency of the high-pressure heater are closely related. To improve energy economy, while ensuring the water level is within the normal range, the upper differential pressure must be kept within the most economical range. Since the unit operates in AGC mode, the unit load fluctuates significantly, causing the inlet steam pressure and outlet water temperature of the high-pressure heater to fluctuate in real time with the load. Therefore, it is necessary to implement automatic control of the extraction steam regulating valve to follow the load.

[0004] Currently, upper-end differential control is mostly achieved through direct upper-end differential PID control. However, upper-end differential is essentially a temperature difference measurement point, and the outlet water temperature data changes slowly, which is not suitable for the actual high load rate of the unit under AGC mode. In terms of application approach, there is a lack of consideration for the safety risks of flash evaporation of hydrophobic media, and there is a lack of effective control over the lower limit of inlet steam pressure.

[0005] Based on the above, this invention proposes a high-pressure heater upper end differential pressure adjustment system and control method, which can effectively solve the above problems. Summary of the Invention

[0006] The purpose of this invention is to provide a high-pressure heater upper-end differential pressure adjustment system and control method. The high-pressure heater upper-end differential pressure adjustment system and control method of this invention are easy to use. When the unit load changes, rapid closed-loop automatic control of the regulating valve is achieved through steam pressure regulation PID to ensure that the inlet steam pressure meets the design economic parameter requirements. When the unit load is stable, the upper-end differential pressure meets the design economic parameter requirements through superposition calculation of inlet steam regulating valve commands.

[0007] This invention is achieved through the following technical solution:

[0008] A high-pressure heater upper differential pressure regulation system includes an upper differential pressure superposition module, a variable load fast adjustment control module, and an inlet steam pressure lock-up reduction module.

[0009] The purpose of this invention is to provide a high-pressure heater upper-end differential pressure adjustment system and control method. The high-pressure heater upper-end differential pressure adjustment system and control method of this invention are easy to use. When the unit load changes, rapid closed-loop automatic control of the regulating valve is achieved through steam pressure regulation PID to ensure that the inlet steam pressure meets the design economic parameter requirements. When the unit load is stable, the upper-end differential pressure meets the design economic parameter requirements through superposition calculation of inlet steam regulating valve commands.

[0010] Preferably, the upper differential superposition module includes an upper differential calculation unit, a valve position superposition calculation unit, a valve position superposition self-holding unit, and a valve position superposition zeroing unit.

[0011] Preferably, the variable load fast adjustment control module includes a steam pressure regulation PID unit and a variable load fast adjustment self-holding unit.

[0012] A control method for a high-pressure heater upper-end differential pressure adjustment system includes the following steps:

[0013] Step S1: Calculate the actual value T1 of the upper end difference of the high-pressure heater by the deviation between the saturation temperature of the steam inlet pressure and the outlet water temperature.

[0014] Step S2: When the actual load of the unit and the load command are less than the preset value k, compare the value T1 with the difference T2 at the most economic end corresponding to different load segments of the unit;

[0015] Step S3: When T1-T2 > preset dead zone value D1, the valve position superposition value Y1 is reduced by the preset value △Y to the new Y1 value every preset time t1. This step is repeated continuously until T1-T2 ≤ preset dead zone value D1.

[0016] When T1-T2 < preset dead zone value D2, the superimposed value Y1 is increased by a preset value △Y to a new Y1 value every preset time interval t1. This step is repeated continuously until T1-T2 ≥ preset dead zone value D2.

[0017] Preferably, in the valve position superposition self-holding unit, the Y1 value remains unchanged when any of the three operating conditions—bad quality of outlet water temperature, bad quality of inlet steam pressure, or malfunction of extraction steam regulating valve—are triggered.

[0018] Preferably, in the valve position superposition zeroing unit, when the extraction steam regulating valve is withdrawn from automatic operation, the valve position superposition value Y1 is cleared to zero; otherwise, the Y1 value is used as the extraction steam regulating valve command superposition value.

[0019] Preferably, in the steam pressure regulating PID unit, when the actual load of the unit and the load command are greater than or equal to the preset value k, the actual value of the inlet steam pressure P1 is compared with the calculated value of the inlet steam pressure P2 corresponding to different load segments, and the deviation of the inlet steam pressure regulating PID unit is output as the valve opening command Y2 value.

[0020] Preferably, in the variable load fast adjustment self-holding unit, when any of the three operating conditions such as bad steam pressure, extraction steam regulating valve failure, and actual load and load command < preset value k are triggered, the Y2 value remains unchanged; otherwise, the Y2 value is used as the extraction steam regulating valve command.

[0021] Preferably, in the steam inlet pressure lockout reduction module, when the deviation between the calculated saturation temperature of the steam inlet pressure and the emergency drain temperature is <3℃, it indicates that there is a risk of flash evaporation of the medium in the emergency drain pipeline, and the extraction steam regulating valve command reduces the lockout.

[0022] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0023] The high-pressure heater upper differential pressure adjustment system and control method of the present invention are easy to use. When the unit load changes, the steam pressure adjustment PID realizes rapid closed-loop automatic control of the regulating valve to ensure that the inlet steam pressure meets the design economic parameter requirements. When the unit load is stable, the upper differential pressure meets the design economic parameter requirements through superposition calculation of the inlet steam regulating valve command. Attached Figure Description

[0024] Figure 1 This is a control strategy diagram for the differential superposition unit at the upper end of the high-pressure heater of the present invention;

[0025] Figure 2 This is a general diagram of the differential pressure control strategy for the high-pressure heater of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of the present invention, preferred embodiments of the present invention are described below in conjunction with specific examples. However, it should be understood that the accompanying drawings are for illustrative purposes only and should not be construed as limiting the present patent. For better illustration of this embodiment, some components in the drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions of the product. It is understandable that some well-known structures and their descriptions may be omitted in the drawings for those skilled in the art. The positional relationships described in the drawings are for illustrative purposes only and should not be construed as limiting the present patent.

[0027] Example 1:

[0028] like Figures 1 to 2 As shown, a high-pressure heater upper differential pressure adjustment system includes an upper differential pressure superposition module, a variable load fast adjustment control module, and an inlet steam pressure lock-up reduction module.

[0029] Furthermore, in another embodiment, the upper differential superposition module includes an upper differential calculation unit, a valve position superposition calculation unit, a valve position superposition self-holding unit, and a valve position superposition zeroing unit.

[0030] Furthermore, in another embodiment, the variable load fast adjustment control module includes a steam pressure regulation PID unit and a variable load fast adjustment self-holding unit.

[0031] A control method for a high-pressure heater upper-end differential pressure adjustment system includes the following steps:

[0032] Step S1: Calculate the actual value T1 of the upper end difference of the high-pressure heater by the deviation between the saturation temperature of the steam inlet pressure and the outlet water temperature.

[0033] Step S2: When the actual load of the unit and the load command are less than the preset value k, compare the value T1 with the difference T2 at the most economic end corresponding to different load segments of the unit;

[0034] Step S3: When T1-T2 > preset dead zone value D1, the valve position superposition value Y1 is reduced by the preset value △Y to the new Y1 value every preset time t1. This step is repeated continuously until T1-T2 ≤ preset dead zone value D1.

[0035] When T1-T2 < preset dead zone value D2, the superimposed value Y1 is increased by a preset value △Y to a new Y1 value every preset time interval t1. This step is repeated continuously until T1-T2 ≥ preset dead zone value D2.

[0036] Furthermore, in another embodiment, in the valve position superposition self-holding unit, the Y1 value remains unchanged when any of the three operating conditions—bad quality of outlet water temperature, bad quality of inlet steam pressure, or malfunction of extraction steam regulating valve—are triggered.

[0037] Furthermore, in another embodiment, in the valve position superposition value clearing unit, when the extraction steam regulating valve is withdrawn from automatic operation, the valve position superposition value Y1 is cleared to zero; otherwise, the Y1 value is used as the extraction steam regulating valve command superposition value.

[0038] Furthermore, in another embodiment, in the steam pressure regulating PID unit, when the actual load of the unit and the load command are greater than or equal to the preset value k, the actual value of the inlet steam pressure P1 is compared with the calculated value of the inlet steam pressure P2 corresponding to different load segments, and the deviation in the steam pressure regulating PID unit is output as the valve opening command Y2 value.

[0039] To ensure reliable control of the valve opening, the proportional P parameter in the steam pressure regulating PID unit is taken from the piecewise linear function f1(x) of the actual load rate, and the integral I parameter is taken from the piecewise linear function f2(x) of the deviation between the actual load and the load command.

[0040] Furthermore, in another embodiment, in the variable load fast adjustment self-holding unit, when any of the three operating conditions such as bad steam pressure, extraction steam regulating valve failure, and actual load and load command < preset value k are triggered, the Y2 value remains unchanged; otherwise, the Y2 value is used as the extraction steam regulating valve command.

[0041] Furthermore, in another embodiment, in the steam inlet pressure lockout reduction module, when the deviation between the calculated saturation temperature of the steam inlet pressure and the emergency drain temperature is <3℃, it indicates that there is a risk of flash evaporation of the medium in the emergency drain pipeline, and the extraction steam regulating valve command reduces the lockout.

[0042] Figure 1 In the middle, 1 is the upper end difference calculation unit, 2 is the valve position superposition calculation unit, 3 is the valve position superposition self-holding unit, and 4 is the valve position superposition zeroing unit; Figure 2 In the diagram, 5 is the steam pressure regulation PID unit, 6 is the variable load fast adjustment self-holding unit, and 7 is the inlet steam pressure lock-up reduction unit.

[0043] Example 2:

[0044] At a certain moment, the generator load of a 600MW thermal power unit is 400MW and remains stable. At this time, the most economical end difference T2 is -2℃, the outlet water temperature of a certain high-pressure heater is 222℃, the inlet steam pressure of the high-pressure heater is 2.05MPa, and the corresponding saturation temperature is 213℃. At this time, the calculated real-time end difference T1 = 222℃ - 213℃ = 9℃. At this time, T1 - T2 > the preset dead zone value D1, which exceeds the preset time t1. The value of D1 is 1℃, and the value of t1 is 180s.

[0045] Furthermore, the valve position superposition calculation module outputs a ΔY value of 2%. This ΔY value is passed through the valve position superposition self-holding module and the valve position superposition zeroing module. If both of these conditions are not met, the ΔY value of 2% is superimposed on the extraction steam regulating valve command, causing the valve to close by 2%.

[0046] Furthermore, in the next time period, the lower differential water level superposition module determines that T1-T2 > preset dead zone value D1 exceeds preset time t1. The Y1 value is superimposed on the ΔY value of 2% + 2% = 4%. At this time, the ΔY value of 4% is passed through the valve position superposition self-holding module and the valve position superposition zeroing module. If both conditions are not met, the Y1 value of 4% is superimposed on the extraction steam regulating valve command, causing the valve to close by 4%. This step is repeated until the condition D2 < T1-T2 < D1 is met, and the valve superposition remains unchanged.

[0047] Based on the description and accompanying drawings of this invention, those skilled in the art can easily manufacture or use the high-pressure heater upper differential pressure adjustment system and control method of this invention, and can produce the positive effects described in this invention.

[0048] Unless otherwise specified, in this invention, terms such as "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and 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, the terms used to describe orientation or positional relationships in this invention are for illustrative purposes only and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood in conjunction with the accompanying drawings and according to the specific circumstances.

[0049] Unless otherwise explicitly specified and limited, the terms "set up," "connected," and "linked" in this invention 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 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.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A control method for a high-pressure heater upper-end differential pressure adjustment system, characterized in that, Includes the following steps: Step S1: Calculate the actual value T1 of the upper end difference of the high-pressure heater by the deviation between the saturation temperature of the steam inlet pressure and the outlet water temperature. Step S2: When the actual load of the unit and the load command are less than the preset value k, compare the value T1 with the difference T2 at the most economic end corresponding to different load segments of the unit; Step S3: When T1-T2 > preset dead zone value D1, the valve position superposition value Y1 is reduced by the preset value △Y to the new Y1 value every preset time t1. This step is repeated continuously until T1-T2 ≤ preset dead zone value D1. When T1-T2 < preset dead zone value D2, the superimposed value Y1 is increased by a preset value △Y to a new Y1 value every preset time t1, and this step is repeated continuously until T1-T2 ≥ preset dead zone value D2. In the valve position superposition self-holding unit, when any of the three working conditions such as bad quality of outlet water temperature, bad quality of inlet steam pressure, or failure of extraction steam regulating valve are triggered, the value of Y1 remains unchanged. The high-pressure heater upper end differential adjustment system includes an upper end differential superposition module, a variable load fast adjustment control module, and an inlet steam pressure lock-up reduction module. The upper differential superposition module includes an upper differential calculation unit, a valve position superposition calculation unit, a valve position superposition self-holding unit, and a valve position superposition zeroing unit. The variable load fast adjustment control module includes a steam pressure regulation PID unit and a variable load fast adjustment self-holding unit.

2. The control method for the high-pressure heater upper end differential pressure adjustment system according to claim 1, characterized in that: In the valve position superposition zeroing unit, when the extraction steam regulating valve is withdrawn from automatic operation, the valve position superposition value Y1 is cleared to zero; otherwise, the Y1 value is used as the extraction steam regulating valve command superposition value.

3. The control method for the high-pressure heater upper end differential pressure adjustment system according to claim 1, characterized in that: In the steam pressure regulation PID unit, when the actual load of the unit and the load command are greater than or equal to the preset value k, the actual value of the inlet steam pressure P1 is compared with the calculated value of the inlet steam pressure P2 corresponding to different load segments. The steam pressure regulation PID unit outputs the valve opening command Y2 value according to the deviation.

4. The control method for the high-pressure heater upper end differential pressure adjustment system according to claim 1, characterized in that: In the variable load fast adjustment self-holding unit, when any of the three working conditions are triggered, such as bad steam pressure, extraction steam regulating valve failure, or actual load and load command < preset value k, the Y2 value remains unchanged; otherwise, the Y2 value is used as the extraction steam regulating valve command.

5. The control method for the high-pressure heater upper end differential pressure adjustment system according to claim 1, characterized in that: In the steam inlet pressure lockout reduction module, when the deviation between the calculated saturation temperature of the steam inlet pressure and the emergency drain temperature is <3℃, it indicates that there is a risk of flash evaporation of the medium in the emergency drain pipeline, and the extraction steam regulating valve command reduces the lockout.

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