Automatic control method for a steam pump recirculation regulating valve

Abstract

The application discloses an automatic control method for a steam pump recirculation regulating valve, and comprises the following steps: when the steam pump recirculation regulating valve is automatically controlled, PID control constants are automatically set; when the actual steam pump water flow value exceeds the PID control constants, the opening of the steam pump recirculation regulating valve is gradually reduced to a preset opening, and the opening of the steam pump recirculation regulating valve is maintained at the preset opening; after the steam pump water flow exceeds a preset value for a certain time, the steam pump recirculation regulating valve is gradually closed at a preset rate; a hysteresis function is formed according to a received unit load instruction correction value, the upper and lower limit values of the opening of the steam pump recirculation regulating valve are limited by the hysteresis function, and the steam pump recirculation regulating valve is operated in a preset range; and the steam pump recirculation regulating valve opening can be automatically controlled according to the operation condition, and the steam pump is protected to be safely operated.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of thermal power generation control, and relates to an automatic control method for a steam pump recirculation regulating valve. BACKGROUND

[0002] The steam pump recirculation regulating valve is mainly used in cooperation with a steam pump. When the steam pump water supply is low, the steam pump recirculation valve is used to return water to a deaerator to ensure stable operation of the steam pump during low water supply. When the steam pump water supply is normal, the steam pump recirculation regulating valve is closed, and the steam pump stably supplies water to the boiler. When the steam pump water supply suddenly decreases to the minimum flow, the steam pump recirculation regulating valve is quickly opened to ensure safe operation of the steam pump.

[0003] The steam pump recirculation regulating valve is generally controlled by an open loop, and a hysteresis loop control is more common. However, the open loop control is relatively simple, and when minimum flow protection occurs, the steam pump recirculation regulating valve cannot be quickly opened. SUMMARY

[0004] The present application aims to overcome the shortcomings of the prior art and provides an automatic control method for a steam pump recirculation regulating valve, which can automatically control the opening degree of the steam pump recirculation regulating valve according to the operating conditions to protect safe operation of the steam pump.

[0005] To achieve the above-mentioned purpose, the automatic control method for a steam pump recirculation regulating valve comprises the following steps:

[0006] When the steam pump recirculation regulating valve is automatically controlled, the PID control constant value is automatically set;

[0007] When the actual value of the steam pump water supply flow exceeds the PID control constant value, the opening degree of the steam pump recirculation regulating valve is gradually reduced to a preset opening degree, and the opening degree of the steam pump recirculation regulating valve is maintained at the preset opening degree;

[0008] When the steam pump water supply flow exceeds the preset value for a preset time, the steam pump recirculation regulating valve is gradually closed at a preset rate;

[0009] A hysteresis function is formed according to the received unit load instruction correction value, the upper and lower limit values of the opening degree of the steam pump recirculation regulating valve are limited by using the hysteresis function, and the steam pump recirculation regulating valve is operated in a preset range.

[0010] When the minimum flow protection of the steam pump is triggered, the steam pump recirculation regulating valve is opened by the feedforward action of the PID, and the upper and lower limit values of the steam pump recirculation regulating valve are corrected, so that the steam pump recirculation regulating valve can match the safe operation of the steam pump.

[0011] The preset opening degree is 20%.

[0012] When the steam pump recirculation valve is automatically switched to manual, if the opening of the steam pump recirculation valve is less than 20% at this time, the opening of the steam pump recirculation valve is gradually adjusted to 20% at a preset rate; otherwise, the opening of the steam pump recirculation valve is maintained unchanged.

[0013] The automatic control method is realized through a steam pump recirculation valve control loop.

[0014] The present application has the following beneficial effects:

[0015] In the automatic control method of the steam pump recirculation valve, the opening of the steam pump recirculation valve is controlled based on PID control, the upper and lower limit values of the opening of the steam pump recirculation valve are controlled based on a hysteresis function, and the steam pump recirculation valve is quickly opened based on the feedforward action of PID, while the upper and lower limit values of the steam pump recirculation valve are corrected to meet the automatic opening and closing function under normal operating conditions of the steam pump recirculation valve and the quick opening function under the minimum flow condition of the steam pump recirculation valve. It should be noted that by using the present application, the optimal control constant is automatically set after the steam pump recirculation valve is automatically switched, and the operating requirements of each condition are automatically matched. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 The present application is a schematic diagram.

[0017] PID-01, SP-01, T-01, T-02, A-00, A-01, A-02, A-03, A-04, A-05, A-06, A-07, A-08, A-09, A-10, AO-01, LAG-01, LAG-02, FX-01, FX-02, FX-03, FX-04, FX-05, V-01, V-02, V-03, L-01, H-01, ADD-01, SUB-01, SUB-02, MAX-01, MAX-02, MAX-03, MAX-04, MAX-05, MIN-01, MIN-02, D-01, D-02, TON-01, OR-01, AND-01, SR-01, NOT-01. DETAILED DESCRIPTION

[0018] In order to make the person skilled in the art better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments, and are not intended to limit the scope of the present application. In addition, in the following description, the description of the known structures and technologies is omitted to avoid unnecessary confusion of the concepts disclosed in the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0019] The structural schematic diagrams according to the disclosed embodiments of the present application are shown in the drawings. These drawings are not drawn to scale, in which some details are enlarged for the purpose of clear expression, and some details can be omitted. The shapes of various regions, layers and their relative size and positional relationship shown in the drawings are only exemplary, and in actuality, there can be deviations due to manufacturing tolerances or technical limitations, and the regions / layers with different shapes, sizes and relative positions can be additionally designed by those skilled in the art according to actual needs.

[0020] The automatic control method of the steam pump recirculation regulating valve described in the present application comprises:

[0021] When the steam pump recirculation regulating valve is put into automatic control, the PID control set value is set;

[0022] When the actual value of the steam pump water supply flow exceeds the PID control set value, the opening of the steam pump recirculation regulating valve is gradually reduced to a preset opening, and the preset opening is 20%; and the opening of the steam pump recirculation regulating valve is maintained at the preset opening to avoid fluctuations of the steam pump water supply flow around the PID control set value, which causes the steam pump recirculation regulating valve to vibrate;

[0023] When the steam pump water supply flow exceeds the preset value for a preset time, the steam pump recirculation regulating valve is gradually closed at a preset rate;

[0024] A hysteresis function is formed according to the received unit load instruction correction value, the upper and lower limit values of the opening of the steam pump recirculation regulating valve are limited by using the hysteresis function, and the steam pump recirculation regulating valve is operated in a preset range.

[0025] When the minimum flow protection of the steam pump is triggered, the steam pump recirculation regulating valve is opened by the feedforward action of the PID, and the upper and lower limit values of the steam pump recirculation regulating valve are corrected, so that the steam pump recirculation regulating valve can match the safe operation of the steam pump.

[0026] When the steam pump recirculation valve is switched from automatic to manual, if the opening of the steam pump recirculation valve is less than 20% at this time, the opening of the steam pump recirculation valve is gradually adjusted to 20% at a preset rate; otherwise, the opening of the steam pump recirculation valve is maintained unchanged to ensure the safe operation of the steam pump.

[0027] Reference Figure 1 The present application is realized by the following steam pump recirculation valve control circuit, the logic circuit comprises a steam pump recirculation valve control block PID-01, a steam pump recirculation valve control setting block SP-01, a steam pump recirculation valve switching block T-01, a steam pump recirculation valve lower limit switching block T-02, a steam pump recirculation valve automatic setting value module A-00, a steam pump minimum flow protection value module A-01, a steam pump feed water flow deviation comparison value module A-02, a steam pump recirculation instruction comparison value module A-03, a set block A-04 of the first control switching block, a set block A-05 of the second control switching block, a steam pump feed water flow value module A-06, a minimum flow protection correction upper limit value module A-07, a steam pump recirculation valve upper limit value module A-08, a unit load instruction value module A-09, a steam pump recirculation valve lower limit value module A-10, a steam pump recirculation valve instruction module AO-01, a steam pump feed water flow filter block LAG-01, a minimum flow protection margin filter block LAG-02, a steam pump recirculation valve feedforward function block FX-01, a control deviation correction valve upper limit function block FX-02, a minimum flow protection margin correction valve upper limit function block FX-03, a unit load instruction correction valve lower limit function block FX-04, a unit load instruction correction valve upper limit function block FX-05, a steam pump recirculation valve switching block rear limit speed block V-01, a steam pump recirculation valve control deviation correction rear limit speed block V-02, a minimum flow protection correction rear limit speed block V-03, a control deviation low limit block L-01, a steam pump recirculation valve instruction high limit block H-01, a steam pump recirculation valve upper limit calculation block ADD-01, a control deviation subtraction block SUB-01, a minimum flow protection margin subtraction block SUB-02, a steam pump recirculation valve instruction maximum selection block MAX-01, a first steam pump recirculation valve upper limit maximum selection block MAX-02, a second steam pump recirculation valve upper limit maximum selection block MAX-03, a third steam pump recirculation valve upper limit maximum selection block MAX-04, a steam pump recirculation valve lower limit maximum selection block MAX-05, a steam pump recirculation valve upper limit minimum selection block MIN-01, a steam pump recirculation valve lower limit minimum selection block MIN-02, a first steam pump recirculation manual bit D-01, a second steam pump recirculation manual bit D-02, a control deviation low limit comparison rear delay block TON-01, a switching quantity or block OR-01, a switching quantity and block AND-01, a switching quantity SR memory block SR-01, and a switching quantity non-taking block NOT-01.

[0028] The output end of the steam pump recirculation regulating valve automatic setting value module A-00 is connected with the input end SP of the steam pump recirculation regulating valve control setting block SP-01; the output end of the steam pump minimum flow protection value module A-01 is connected with the input end LL of the steam pump recirculation regulating valve control setting block SP-01.

[0029] The output end of the steam pump feed water flow value module A-06 is connected with the input end X1 of the steam pump feed water flow filtering block LAG-01.

[0030] The output end OUT of the steam pump recirculation regulating valve control setting block SP-01 is connected with the input end X1 of the control deviation subtraction block SUB-01, and the output end OUT of the steam pump feed water flow filtering block LAG-01 is connected with the input end X2 of the control deviation subtraction block SUB-01.

[0031] The output end OUT of the control deviation subtraction block SUB-01 is connected with the input end X1 of the steam pump recirculation regulating valve control block PID-01 and the input end X1 of the control deviation low limit block L-01, and the output end of the steam pump feed water flow deviation comparison value module A-02 is connected with the input end X2 of the control deviation low limit block L-01.

[0032] The output end OUT of the control deviation low limit block L-01 is connected with the input end X1 of the control deviation low limit comparison and time delay block TON-01.

[0033] The output end OUT of the steam pump recirculation regulating valve control block PID-01 is connected with the input end X1 of the steam pump recirculation regulating valve instruction high limit block H-01, and the output end of the steam pump recirculation instruction comparison value module A-03 is connected with the input end X2 of the steam pump recirculation regulating valve instruction high limit block H-01.

[0034] The output end OUT of the steam pump recirculation regulating valve instruction high limit block H-01 is connected with the input end X1 of the on-off quantity taking non block NOT-01.

[0035] The output end OUT of the control deviation low limit comparison and time delay block TON-01 is connected with the input end X1 of the on-off quantity and block AND-01, and the output end OUT of the on-off quantity taking non block NOT-01 is connected with the input end X2 of the on-off quantity and block AND-01.

[0036] The output end of the first steam pump recirculation manual position D-01 is connected with the input end X1 of the on-off quantity or block OR-01, and the output end OUT of the on-off quantity and block AND-01 is connected with the input end X2 of the on-off quantity or block OR-01.

[0037] The output terminal OUT of the switch quantity OR-01 is connected with the input terminal R of the switch quantity SR memory block SR-01. The output terminal OUT of the pump recirculation valve command high limit block H-01 is connected with the input terminal S of the switch quantity SR memory block SR-01.

[0038] The output terminal OUT of the switch quantity SR memory block SR-01 is connected with the input terminal X1 of the pump recirculation valve switching block T-01. The output terminal of the set block A-04 of the first control switching block is connected with the input terminal Y of the pump recirculation valve switching block T-01. The output terminal of the set block A-05 of the second control switching block is connected with the input terminal N of the pump recirculation valve switching block T-01.

[0039] The output terminal OUT of the pump recirculation valve switching block T-01 is connected with the input terminal X1 of the pump recirculation valve switching block rear speed limit block V-01.

[0040] The output terminal OUT of the pump recirculation valve switching block rear speed limit block V-01 is connected with the input terminal X1 of the pump recirculation valve command maximum selection block MAX-01. The output terminal OUT of the pump recirculation valve control block PID-01 is connected with the input terminal X2 of the pump recirculation valve command maximum selection block MAX-01.

[0041] The output terminal OUT of the pump recirculation valve command maximum selection block MAX-01 is connected with the input terminal of the pump recirculation valve command module AO-01.

[0042] The output terminal of the pump minimum flow protection value module A-01 is connected with the input terminal X1 of the minimum flow protection margin subtraction block SUB-02. The output terminal of the pump feed water flow value module A-06 is connected with the input terminal X2 of the minimum flow protection margin subtraction block SUB-02.

[0043] The output terminal OUT of the minimum flow protection margin subtraction block SUB-02 is connected with the input terminal X1 of the minimum flow protection margin filter block LAG-02.

[0044] The output terminal OUT of the minimum flow protection margin filter block LAG-02 is connected with the input terminal X1 of the pump recirculation valve feed forward function block FX-01.

[0045] The output terminal OUT of the pump recirculation valve feed forward function block FX-01 is connected with the input terminal X2 of the pump recirculation valve control block PID-01.

[0046] The output terminal OUT of the control deviation subtraction block SUB-01 is connected with the input terminal X1 of the control deviation correction control valve upper limit function block FX-02.

[0047] The output terminal OUT of the control deviation correction modified upper limit function block FX-02 is connected to the input terminal Xl of the pump recirculation control valve control deviation correction post-limiting speed block V-02.

[0048] The output terminal OUT of the minimum flow protection margin filter block LAG-02 is connected to the input terminal Xl of the minimum flow protection margin correction modified upper limit function block FX-03.

[0049] The output terminal OUT of the minimum flow protection margin correction modified upper limit function block FX-03 is connected to the input terminal Xl of the minimum flow protection correction post-limiting speed block V-03.

[0050] The output terminal OUT of the minimum flow protection correction post-limiting speed block V-03 is connected to the input terminal Xl of the pump recirculation control valve upper limit calculation block ADD-01, and the output terminal of the minimum flow protection correction upper limit value block A-07 is connected to the input terminal X2 of the pump recirculation control valve upper limit calculation block ADD-01.

[0051] The output terminal OUT of the pump recirculation control valve control deviation correction post-limiting speed block V-02 is connected to the input terminal Xl of the first pump recirculation control valve upper limit maximum selection block MAX-02, and the output terminal OUT of the pump recirculation control valve upper limit calculation block ADD-01 is connected to the input terminal X2 of the first pump recirculation control valve upper limit maximum selection block MAX-02.

[0052] The output terminal of the unit load command value block A-09 is connected to the input terminal Xl of the unit load command correction modified lower limit function block FX-04 and the input terminal Xl of the unit load command correction modified upper limit function block FX-05.

[0053] The output terminal OUT of the unit load command correction modified lower limit function block FX-04 is connected to the input terminal Xl of the pump recirculation control valve lower limit minimum selection block MIN-02, and the output terminal OUT of the third pump recirculation control valve upper limit maximum selection block MAX-04 is connected to the input terminal X2 of the pump recirculation control valve lower limit minimum selection block MIN-02.

[0054] The output terminal OUT of the pump recirculation control valve lower limit minimum selection block MIN-02 is connected to the input terminal Xl of the third pump recirculation control valve upper limit maximum selection block MAX-04, and the output terminal OUT of the unit load command correction modified upper limit function block FX-05 is connected to the input terminal X2 of the third pump recirculation control valve upper limit maximum selection block MAX-04.

[0055] The output end OUT of the first steam pump recirculation valve upper limit large selection block MAX-02 is connected with the input end X1 of the second steam pump recirculation valve upper limit large selection block MAX-03. The output end OUT of the third steam pump recirculation valve upper limit large selection block MAX-04 is connected with the input end X2 of the second steam pump recirculation valve upper limit large selection block MAX-03.

[0056] The output end OUT of the second steam pump recirculation valve upper limit large selection block MAX-03 is connected with the input end X1 of the steam pump recirculation valve upper limit small selection block MIN-01. The output end of the steam pump recirculation valve upper limit value module A-08 is connected with the input end X2 of the steam pump recirculation valve upper limit small selection block MIN-01.

[0057] The output end OUT of the steam pump recirculation valve upper limit small selection block MIN-01 is connected with the input end X3 of the steam pump recirculation valve control block PID-01.

[0058] The output end OUT of the minimum flow protection correction after limiting block V-03 is connected with the input end X1 of the steam pump recirculation valve lower limit large selection block MAX-05. The output end OUT of the steam pump recirculation valve lower limit small selection block MIN-02 is connected with the input end X2 of the steam pump recirculation valve lower limit large selection block MAX-05.

[0059] The output end of the second steam pump recirculation manual position D-02 is connected with the input end X1 of the steam pump recirculation valve lower limit switching block T-02. The output end of the steam pump recirculation valve lower limit value module A-10 is connected with the input end Y of the steam pump recirculation valve lower limit switching block T-02. The output end OUT of the steam pump recirculation valve lower limit large selection block MAX-05 is connected with the input end N of the steam pump recirculation valve lower limit switching block T-02.

[0060] The output end OUT of the steam pump recirculation valve lower limit switching block T-02 is connected with the input end X4 of the steam pump recirculation valve control block PID-01.

[0061] It is to be noted that the minimum flow protection value of the steam pump is taken as the lower limit of the steam pump recirculation valve control setting block SP-01, so that the steam pump recirculation valve is prevented from being quickly opened due to setting errors of the operator.

[0062] In addition, the output value of the steam pump recirculation valve control setting value minus the steam pump feed water flow filtering block LAG-01 is taken as the deviation adjustment controlled variable of the steam pump recirculation valve.

[0063] It should be noted that the set value outputted by the steam pump water flow deviation comparison module A-02 is -200t / h; the set value outputted by the control deviation low limit comparison and delay block TON-01 is 60s; the set value outputted by the steam pump recirculation instruction comparison module A-03 is 3%; the set value outputted by the setting block A-04 of the first control switch block is 20%; and the set value outputted by the setting block A-05 of the second control switch block is 0%.

[0064] In operation, when the input end X1 of the steam pump recirculation valve switch block T-01 is true, the output end of the steam pump recirculation valve switch block T-01 outputs the value of the input end Y of the steam pump recirculation valve switch block T-01, and the output is 20%; when the input end X1 of the steam pump recirculation valve switch block T-01 is false, the output end of the steam pump recirculation valve switch block T-01 outputs the value of the input end N of the steam pump recirculation valve switch block T-01, and the output is 0%.

[0065] The set value outputted by the steam pump recirculation valve upper limit module A-08 is 100%; and the set value outputted by the steam pump recirculation valve lower limit module A-10 is 20%.

[0066] The present application limits the maximum value of the steam pump recirculation valve according to the maximum value of the control deviation correction value, the minimum flow protection margin correction value and the unit load instruction correction value; and limits the minimum value of the steam pump recirculation valve according to the minimum value of the minimum flow protection margin correction value and the unit load instruction correction value.

[0067] When the input end X1 of the steam pump recirculation valve lower limit switch block T-02 is true, the output end of the steam pump recirculation valve lower limit switch block T-02 outputs the value of the input end Y of the steam pump recirculation valve lower limit switch block T-02, and the output is 20%; when the input end X1 of the steam pump recirculation valve lower limit switch block T-02 is false, the output end of the steam pump recirculation valve lower limit switch block T-02 outputs the value of the input end N of the steam pump recirculation valve lower limit switch block T-02, and the output is the value of the steam pump recirculation valve lower limit maximum selection block MAX-05.

[0068] When the steam pump recirculation valve is in manual mode, the minimum opening of the steam pump recirculation valve is 20% to ensure sufficient recirculation flow.

[0069] Finally, it should be noted that the parameters of the steam pump recirculation valve feedforward function block FX-01, the control deviation correction valve upper limit function block FX-02, the minimum flow protection margin correction valve upper limit function block FX-03, the unit load instruction correction valve lower limit function block FX-04, the unit load instruction correction valve upper limit function block FX-05, the control deviation low limit block L-01 and the steam pump recirculation valve instruction high limit block H-01 are set according to the unit operation condition.

Claims

1. An automatic control method for a steam pump recirculation control valve, characterized in that, include: When the steam pump recirculation control valve is set to automatic, the PID control setpoint is automatically set. When the actual value of the steam pump feed water flow exceeds the PID control setpoint, the opening of the steam pump recirculation control valve is gradually reduced to the preset opening, and the opening of the steam pump recirculation control valve is maintained at the preset opening. When the water flow rate of the steam pump exceeds the preset value and the preset time, the steam pump recirculation control valve will be gradually closed at the preset rate. A hysteresis function is formed based on the received unit load command correction value. The hysteresis function is used to limit the upper and lower limits of the opening of the steam pump recirculation control valve, so that the steam pump recirculation control valve operates within a preset range. When the minimum flow protection of the steam pump is triggered, the steam pump recirculation control valve is opened through the feedforward action of the PID controller, and the upper and lower limit values ​​of the steam pump recirculation control valve are corrected to ensure that the steam pump recirculation control valve can match the safe operation of the steam pump. The preset opening degree is 20%; When the steam pump recirculation control valve switches from automatic to manual, if the valve opening is less than 20%, the valve opening will be gradually adjusted to 20% at a preset rate; otherwise, the valve opening will remain unchanged. The automatic control method is implemented through the steam pump recirculation valve control loop.

Images