Method for adjusting swing of high-pressure control valve of steam turbine

Abstract

The method for adjusting swing of high-pressure valve of steam turbine relates to the field of high-pressure valve control of steam turbine. The method is used to solve the problem that the EDPF-NT type DEH system appears small swing of high-pressure valve during actual operation of the thermal power unit. The method for adjusting swing of high-pressure valve of steam turbine is used to calculate the absolute value of the difference between the current CCS steam turbine load instruction and the DEH steam turbine load instruction of the previous time, and then take the minimum value between the absolute value and the maximum increment of the CCS steam turbine load instruction, so as to completely eliminate the small swing of the high-pressure valve when the steam turbine is offline and stopped. When the steam turbine is online, the maximum increment of the CCS steam turbine load instruction is reduced during the execution of the CCS steam turbine load instruction to the DEH steam turbine load instruction, so as to weaken the small swing of the high-pressure valve.

Description

Technical Field

[0001] This invention belongs to the field of high-speed control of steam turbines. Background Technology

[0002] DEH, or Digital Electric Hydraulic Control System for Steam Turbines, is an important component of DCS. It includes: steam turbine speed control, automatic synchronization control, load control, participation in primary frequency regulation, turbine-boiler coordinated control, rapid load reduction, main steam pressure control, single valve control, multi-valve decoupling control, valve testing, steam turbine programmed start-up, OPC control, manual control, etc., and achieves data sharing with the DCS system.

[0003] Figure 1 This is a logic diagram illustrating the transmission from the CCS (Coordinated Control System) turbine load command to the DEH turbine load command in an EDPF-NT type DEH system. The DEH turbine load command is used to control the high-pressure regulating valve position. The DEH logic operates according to the following steps in each operation cycle: Figure 2 The execution order shown calculates each function block sequentially. The current output of the subtraction operation (the difference between the current CCS turbine load command and the previous DEH turbine load command) needs to lag two operation cycles before the addition operation can be performed. For example, at the current time k, the current output of the subtraction function block is δ. k The current output of the absolute value operation block is the absolute value |δ of the output of the subtraction operation block at the previous time step (time step k-1). k-1 The current output of the minimum value operation block is the minimum value (|δ) of the output of the absolute value operation block at the previous time step (time step k-2) and the maximum increment of 0.35 in CCS mode. k-2 |,0.35). Therefore, using the existing execution flow from CCS turbine load command to DEH turbine load command will cause the DEH turbine load command to overshoot relative to the CCS turbine load command, resulting in a swing in the DEH turbine load command. The peak-to-peak value of this swing is 2 (peak + trough) × 2 (2 lag cycles) × 0.35 (maximum increment in CCS mode). Therefore, in the EDPF-NT type DEH system, some units will experience a small swing in the high-voltage control valve, manifested as no swing in the CCS turbine load command but a small swing in the DEH turbine load command during adjustment. Figure 3 As shown. Summary of the Invention

[0004] This invention aims to solve the problem of slight oscillation of the high-pressure regulating valve in some units of the EDPF-NT type DEH system during actual operation of thermal power units. A method for adjusting the oscillation of the turbine high-pressure regulating valve is provided.

[0005] Methods for adjusting the swing of the turbine high-pressure control valve include:

[0006] Determine if the steam turbine is offline and shut down.

[0007] Therefore, during the execution of the CCS turbine load command to the DEH turbine load command, the absolute value of the difference between the current CCS turbine load command and the DEH turbine load command at the previous moment is first calculated, and then the minimum value between the absolute value and the maximum increment of the CCS turbine load command is taken.

[0008] Otherwise, during the execution of the CCS turbine load command to the DEH turbine load command, the maximum increment of the CCS turbine load command is reduced.

[0009] Furthermore, when the turbine is offline and shut down, the execution process from the CCS turbine load command to the DEH turbine load command is as follows:

[0010] S1: Calculate the difference between the current CCS turbine load command and the previous DEH turbine load command;

[0011] S2: Take the absolute value of the difference obtained from S1;

[0012] S3: Take the minimum value between the absolute value obtained in S2 and the maximum increment of the CCS turbine load command;

[0013] S4: Determine whether the difference obtained in S1 is greater than or equal to 0.001. If yes, set the intermediate variable to 1; otherwise, set the intermediate variable to -1.

[0014] S5: Multiply the intermediate variable obtained in S4 with the minimum value obtained in S3 to obtain the product;

[0015] S6: Add the product obtained in S5 to the DEH turbine load command at the previous moment to obtain the DEH turbine load command at the current moment, and use the DEH turbine load command at the current moment to control the high-pressure regulating valve position.

[0016] Furthermore, the maximum increment of the CCS turbine load command in S3 above is 0.35.

[0017] Furthermore, the aforementioned reduction in the maximum increment of the CCS turbine load command includes:

[0018] The maximum increment of the CCS turbine load command is reduced to A, and the method for determining the value of A includes:

[0019] Collect CCS turbine load commands for historical periods at time intervals of λ.

[0020] Calculate the absolute value of the difference between two adjacent CCS turbine load commands, and select the maximum value B among the absolute values;

[0021] A is calculated according to the following formula:

[0022]

[0023] Where C represents the operation cycle of a logical page.

[0024] Furthermore, the aforementioned time interval λ is 1 second.

[0025] Furthermore, the CCS turbine load instructions for the aforementioned historical period are CCS turbine load instructions for one month in history.

[0026] This invention proposes a method for adjusting the swing of the high-pressure control valve of a steam turbine. This method is designed for EDPF-NT type DEH systems and can reduce the small swing of the high-pressure control valve while operating online without shutting down the machine. It can also completely eliminate the problem of small swing of the high-pressure control valve during offline shutdown maintenance. Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating the transfer of CCS turbine load commands to DEH turbine load commands in the existing EDPF-NT type DEH system.

[0028] Figure 2 This is a schematic diagram of the execution flow from CCS turbine load command to DEH turbine load command in the existing EDPF-NT type DEH system;

[0029] Figure 3 A schematic diagram of the small swing curve of the high-adjustment gate in the existing EDPF-NT type DEH system;

[0030] Figure 4 The diagram shows the effect of reducing the slight swing of the high-adjustment door of the EDPF-NT type DEH system after adopting method one for online operation without shutting down the system.

[0031] Figure 5 This is a schematic diagram of the execution flow of Method 2;

[0032] Figure 6 The diagram shows the effect of completely eliminating the slight oscillation of the high-adjustment door of the EDPF-NT type DEH system after using Method 2 when the system is shut down and operating offline. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0034] Reference Figures 4 to 6 This implementation method reduces the peak-to-peak value of the swing in two ways: first, by reducing the maximum increment in CCS mode, and second, by reducing the lag in the computation cycle. Therefore, this implementation method includes two approaches, as follows:

[0035] Method 1: To mitigate the problem of small-amplitude oscillations of the high-pitched gate while maintaining continuous operation online, the following method is employed:

[0036] Figure 2 In the sequential execution process shown, the maximum increment of the CCS turbine load command is adjusted to A.

[0037] The method for determining the value of A is as follows:

[0038] Collect CCS turbine load commands for one month at 1-second intervals.

[0039] Calculate the absolute value of the difference between two adjacent CCS turbine load commands, and extract the maximum value B from the absolute values.

[0040] The maximum increment A of the CCS turbine load command is calculated using the following formula:

[0041]

[0042] Where C represents the logical page operation cycle, measured in milliseconds (ms).

[0043] After adopting the above method one, the effect of reducing the small swaying problem of the high-pitched gate is as follows: Figure 4 As shown.

[0044] Method 2: To completely eliminate the problem of slight oscillation of the high-pitched door during offline shutdown maintenance, the following method is used:

[0045] The execution order of each computing module was rearranged, combined with... Figure 5 As shown, the steps after arranging are as follows:

[0046] S1: Calculate the difference between the current CCS turbine load command and the previous DEH turbine load command;

[0047] S2: Take the absolute value of the difference from S1;

[0048] S3: Take the minimum value between the absolute value obtained from S2 and the maximum increment of the CCS turbine load command;

[0049] S4: Determine whether the difference between the current CCS turbine load command and the previous DEH turbine load command is greater than or equal to 0.001. If yes, set the intermediate variable to 1; otherwise, set the intermediate variable to -1.

[0050] S5: Multiply the intermediate variable obtained in S4 with the minimum value obtained in S3 to obtain the product;

[0051] S6: Add the product obtained in S5 to the DEH turbine load command at the previous moment to obtain the DEH turbine load command at the current moment, and use the DEH turbine load command at the current moment to control the high-pressure valve position.

[0052] After using Method 2 above, at the current time k, the current output of the subtraction operation function block is δ. k The current output of the absolute value operation block is the absolute value of the output at time k, |δ. k The current output of the minimum value operation block is the minimum value min(|δ) of the output of the absolute value operation block at time k and the maximum increment of 0.35 in CCS mode. k |,0.35), ensuring that subsequent addition and subtraction operations are synchronized, meaning that the DEH turbine load command and the CCS turbine load command are completely consistent, thus completely eliminating the problem of small swing in the high-pressure valve. The effect of eliminating the small swing problem in the high-pressure valve is as follows: Figure 6 As shown.

[0053] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A method for adjusting the swing of the high-pressure regulating valve of a steam turbine, characterized in that, include: Determine if the steam turbine is offline and shut down. When the steam turbine is offline and shut down, the execution process from the CCS steam turbine load command to the DEH steam turbine load command is as follows: S1: Calculate the difference between the current CCS turbine load command and the previous DEH turbine load command; S2: Take the absolute value of the difference obtained from S1; S3: Take the minimum value between the absolute value obtained in S2 and the maximum increment of the CCS turbine load command; S4: Determine whether the difference obtained in S1 is greater than or equal to 0.

001. If yes, set the intermediate variable to 1; otherwise, set the intermediate variable to -1. S5: Multiply the intermediate variable obtained in S4 with the minimum value obtained in S3 to obtain the product; S6: Add the product obtained in S5 to the DEH turbine load command at the previous moment to obtain the DEH turbine load command at the current moment, and use the DEH turbine load command at the current moment to control the high-pressure valve position; Otherwise, during the execution of the CCS turbine load command to the DEH turbine load command, the maximum increment of the CCS turbine load command is reduced; The reduction of the maximum increment of the CCS turbine load command includes: Reduce the maximum increment of the CCS turbine load command to The The methods for obtaining values ​​include: by The CCS turbine load commands for historical time periods are collected at time intervals. Calculate the absolute value of the difference between two adjacent CCS turbine load commands, and select the maximum value among the absolute values. ; The following formula is used to calculate: : ， in, This is the operation cycle of a logical page.

2. The method for swinging the high-pressure control valve of a steam turbine according to claim 1, characterized in that, The time interval It takes 1 second.

3. The method for swinging the high-pressure control valve of a steam turbine according to claim 1 or 2, characterized in that, The CCS turbine load command for the historical period refers to the CCS turbine load command for one month in history.

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