CN115405376A - Control system for improving impulse efficiency during startup of BEST small steam turbine - Google Patents

Abstract

The invention discloses a control system for improving the impulse efficiency when a BEST small turbine is started, which comprises a BEST small turbine bypass valve control system and a BEST small turbine actual backpressure and backpressure set value difference control system, wherein the system can ensure the stable operation of the BEST small turbine.

Description

A Control System for Improving Rush Efficiency When BEST Small Steam Turbine Starts

technical field

The invention belongs to the thermal control field of a BEST small steam turbine with a small generator in an ultra-supercritical double-reheating coal-fired unit, and relates to a control system for improving the running efficiency of the BEST small steam turbine when starting.

Background technique

In the field of thermal power, the experience and technology of BEST small steam turbine in all aspects of operation and commissioning are being perfected day by day. In the cold start-up stage of the BEST small steam turbine, the valve opening of the BEST small steam turbine gradually increases and the bypass valve is fully open, and the speed value rises to 1000r/min. At this time, it is in a low-speed warm-up state. All parts of the steam turbine expand evenly when heated, so that the cylinder, partition, nozzle, shaft, impeller, steam seal and shaft seal and other parts are prevented from deformation and relaxation.

In the warm-up state, because the bypass valve is fully open, the steam supply is large, the mass-to-surface ratio of the rotor is small, and the mass-to-surface ratio of the cylinder is large, which will cause the expansion speed of the rotor to be greater than the expansion speed of the cylinder, so that the expansion difference begins If it increases, it will even trigger the MEST protection, which threatens the stable operation of the BEST small steam turbine and may lead to non-stop accidents of the unit.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art, and provide a control system for improving the running efficiency of the BEST small steam turbine when it is started, and the system can ensure the stable operation of the BEST small steam turbine.

In order to achieve the above-mentioned purpose, the control system for improving the speed-up efficiency of the BEST small steam turbine at start-up according to the present invention includes a BEST small steam turbine bypass valve control system and a BEST small steam turbine actual back pressure and back pressure set value difference control system.

The BEST small steam turbine bypass valve control system includes the input end of the difference between the BEST actual back pressure and the set value of the back pressure, the input end of the difference between the BEST final stage pressure ratio setting and the actual pressure ratio, the BEST small steam turbine startup sequential control feedback end, 7 Feedback ports for No. and No. 8 low-load cut-off, BEST bypass valve full-close feedback port, manual mode feedback port for valve position control of bypass valve, No. 8 low-load cut-off feedback port, BEST small steam turbine trip feedback port, first or second choice Switching block, first non-block, first and block, RS flip-flop, second and block, first or block, second non-block, small machine shaft seal program control instruction 4 feedback terminal, BEST small steam turbine sequence control step 8 Feedback terminal, bypass valve quick-open solenoid valve live command feedback terminal, BEST small steam turbine bypass valve opening output module, first pulse block, second pulse block, third pulse block, first analog constant block, second Analog constant block, third analog constant block, second or block, second two-choice switching block, third two-choice switching block, first PID controller, first F(x) function block, BEST small Steam turbine differential expansion input terminal, first subtraction block, greater than comparison block, second PID controller, limiter block, second F(x) function block and second subtraction block;

The BEST small steam turbine startup sequential control feedback terminal is connected to the input terminal of the first AND block through the first non-block, No. 7 and No. 8 low-plus cut-off feedback terminals are connected to the input end of the first AND block, and the The output terminal is connected with the S terminal of the RS flip-flop;

The No. 8 low plus cut-off feedback terminal is connected to the input terminal of the second AND block through the second non-block, and the BEST bypass valve full-close feedback port and bypass valve valve position control manual mode feedback port are connected to the input end of the second AND block. connected, the output end of the second block and the BEST small steam turbine tripping feedback end are connected with the input end of the first or block, and the output end of the first or block is connected with the R end of the RS flip-flop;

The DV terminal of the RS flip-flop is connected to the EN terminal of the first one-two switching block, the input terminal of the difference between the BEST actual back pressure and the back pressure setting value and the input terminal of the difference between the BEST final stage pressure ratio setting and the actual pressure ratio It is connected with the input end of the first one-two switching block; the RV end of the RS flip-flop is connected with the EN end of the third one-two switching block and the EN end of the second one-two switching block;

The feedback terminal of the small machine shaft seal program control instruction 4 is connected to the input terminal of the second or block through the first pulse block, and the feedback terminal of the 8th step of BEST small steam turbine sequence control is connected to the input end of the second or block through the second pulse block , the BEST small steam turbine trip feedback terminal is connected to the input terminal of the second or block through the third pulse block, the bypass valve quick-open solenoid valve live command feedback terminal is connected to the input end of the second or block, and the first analog constant block, the second analog constant block, the third analog constant block, the output end of the second or block, the output end of the second two-to-one switching block, and the output end of the third two-to-one switching block are respectively connected with the first PID The E terminal, H terminal, L terminal, TR terminal, TS terminal, Kp terminal and Ti terminal of the controller are connected;

The output end of the first PID controller is connected with the input end of the second subtraction block through the first F (x) function block; BEST small steam turbine differential expansion input end and the input end of the first subtraction block and the input end greater than the comparison block The output end of the first subtraction block and the output end of the comparison block are connected with the input end of the second PID controller, and the output end of the second PID controller is connected with the second F(x) function block through the limiting block and the second PID controller. The input end of the second subtraction block is connected, and the output end of the second subtraction block is connected with the BEST small steam turbine bypass valve opening output module.

When working, the second F(x) function block is used to calculate the deviation value of the expansion difference in advance, and the opening degree of the bypass valve of the BEST small steam turbine needs to be reduced.

When the expansion difference gradually increases, the opening of the bypass valve of the BEST small steam turbine is reduced, and the warm-up time of the BEST small steam turbine is increased.

BEST small steam turbine actual back pressure and back pressure set value difference control system includes BEST exhaust steam pressure input end, BEST delay back pressure set value input end, multiplication block, BEST actual back pressure and back pressure set value difference An output module, a third F(x) function block, an addition block, a fourth two-to-one switching block and a third subtraction block;

The BEST small steam turbine expansion difference input terminal is connected to the input terminal of the addition block through the third F(x) function block, the BEST delay back pressure setting value input terminal is connected to the input terminal of the addition block; the BEST exhaust pressure input terminal Connected with the input end of the fourth two-choice switching block and the input end of the third subtraction block;

The bypass valve valve position control manual mode feedback terminal and the output terminal of the addition block are connected to the input terminal of the fourth two-choice switching block, and the output terminal of the fourth two-choice switching block is connected to the input terminal of the third subtraction block , the output terminal of the third subtraction block is connected with the input terminal of the multiplication block, and the output terminal of the multiplication block is connected with the output module of the difference between the BEST actual back pressure and the back pressure set value.

The present invention has the following beneficial effects:

During specific operation of the control system for improving the speed-up efficiency when the BEST small steam turbine is started, when the BEST small steam turbine is started in a cold state, the speed value rises to 1000r/min and is in a warm-up state and the bypass valve is in a fully open state , by monitoring the expansion difference and controlling the opening of the bypass valve in advance, the increasing expansion difference can be effectively controlled to avoid that the bypass valve is fully open and the steam supply increases when the engine is warming up, resulting in The expansion speed of the rotor is greater than the expansion speed of the cylinder, so that the expansion difference begins to increase, which eventually triggers the METS protection.

Description of drawings

Figure 1 is a schematic diagram of the BEST small steam turbine before starting;

Figure 2 is a schematic diagram of the BEST small steam turbine reaching 1000r/min after starting;

Figure 3 is a schematic diagram of the BEST small steam turbine reaching 2400r/min after starting;

Figure 4 is a schematic diagram of the original control system of the BEST small steam turbine bypass valve;

Figure 5 is a schematic diagram of the new control system of the BEST small steam turbine bypass valve;

Fig. 6 is a schematic diagram of the original control system of the difference between the actual back pressure of the BEST small steam turbine and the set value of the back pressure;

Fig. 7 is a schematic diagram of the new control system for the difference between the actual back pressure of the BEST small steam turbine and the set value of the back pressure.

Among them, B001 is the input terminal of the difference between the BEST actual back pressure and the back pressure set value, B002 is the input terminal of the difference between the BEST final stage pressure ratio setting and the actual pressure ratio, B003 is the BEST small steam turbine startup sequential control feedback terminal, and B004 is the No. 7 and No. 8 low-load cut-off feedback ports, B005 is the BEST bypass valve full-close feedback port, B006 is the bypass valve valve position control manual mode feedback port, B007 is the No. 8 low-load cut-off feedback port, and B008 is the BEST small steam turbine Trip feedback terminal, B009 is the first two alternative switching block, B010 is the first non-block, B011 is the first AND block, B012 is the RS flip-flop, B013 is the second AND block, B014 is the first OR block, B015 is the The second non-block, B016 is the feedback terminal of the program control command 4 of the shaft seal of the small machine, B017 is the feedback terminal of the 8th step of the sequence control of the BEST small steam turbine, B018 is the feedback terminal of the live command of the bypass valve quick-open solenoid valve, and B019 is the side of the BEST small steam turbine B020 is the first pulse block, B021 is the second pulse block, B022 is the third pulse block, B023 is the first analog constant block, B024 is the second analog constant block, B025 is the third Analog constant block, B026 is the second or block, B027 is the second one-two switching block, B028 is the third two-one switching block, B029 is the first PID controller, B030 is the first F(x) function block , B031 is the input terminal of BEST small steam turbine differential expansion, B032 is the first subtraction block, B033 is the greater than comparison block, B034 is the second PID controller, B035 is the limiting block, B036 is the second F(x) function block, B037 It is the second subtraction block, D001 is the BEST exhaust pressure input terminal, D002 is the BEST delayed back pressure set value input terminal, D003 is the multiplication block, D004 is the output module of the difference between the BEST actual back pressure and the back pressure set value, D005 is the third F(x) function block, D006 is the addition block, D007 is the fourth two-to-one switching block, and D008 is the third subtraction block.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only The embodiments are a part of the present invention, not all embodiments, and are not intended to limit the scope of the present invention. Also, in the following description, descriptions of well-known structures and techniques are omitted to avoid unnecessarily obscuring the concepts disclosed in the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

The schematic diagrams of the structures according to the disclosed embodiments of the present invention are shown in the accompanying drawings. The figures are not drawn to scale, with certain details exaggerated and possibly omitted for clarity of presentation. The shapes of various regions and layers shown in the figure and their relative sizes and positional relationships are only exemplary, and may deviate due to manufacturing tolerances or technical limitations in practice, and those skilled in the art may Regions/layers with different shapes, sizes, and relative positions can be additionally designed as needed.

Figure 1 is a schematic diagram of the BEST small steam turbine before starting;

1) Figure 1 shows the operating conditions of the BEST small steam turbine before starting;

2) The line numbered 1 is the speed of the BEST small steam turbine, the line numbered 2 is the expansion difference of the BEST small steam turbine, the line numbered 3 is the feedback of the opening degree of the steam supply valve of the BEST small steam turbine, and the line numbered 4 is the shaft of the BEST small steam turbine Sealed steam supply temperature, the line numbered 5 is the pressure of the BEST small steam turbine shaft seal main pipe, the line numbered 6 is the feedback of the bypass valve opening of the BEST small steam turbine, and the line numbered 7 is the exhaust pressure of the BEST small steam turbine;

3) At 16:45:07, the line No. 1 indicates that the speed of BEST small steam turbine is 104.9r/min, the line No. 2 indicates that the expansion difference of BEST small steam turbine is 0mm, and the line No. 3 indicates that the BEST small steam turbine The feedback of the opening of the steam control valve is 0.01%, the line No. 4 is the steam supply temperature of the BEST small steam turbine shaft seal is 28.91°C, the line No. 5 is the pressure of the main pipe of the BEST small steam turbine shaft seal is -0.07kPa, and the line No. 6 is The feedback of the opening degree of the bypass valve of the BEST small steam turbine is 0%, and the line numbered 7 indicates that the exhaust pressure of the BEST small steam turbine is 0 MPa;

4) At 16:45:07, it shows that the BEST small steam turbine BEST is in the cranking state of 104.9r/min, the steam supply regulating valve is not opened, and the expansion difference is in a normal state;

5) During the period from 16:45:07 to 18:23:57, the BEST small steam turbine is in the cranking state of 104.9r/min, the opening of the steam supply regulating valve of the BEST small steam turbine gradually increases, and the expansion difference increases with the the gradual increase;

6) During the period from 18:23:57 to 21:23:57, the BEST small steam turbine BEST is in the cranking state of 104.9r/min, and the opening of the steam supply regulating valve of the BEST small steam turbine has been reduced and maintained. degree state, the expansion difference gradually tends to be stable;

7) During the period from 21:23:57 to 00:23:57, the BEST small steam turbine BEST starts to start, the opening of the BEST small steam turbine steam supply control valve gradually increases, and the opening of the BEST small steam turbine bypass valve is gradually fully opened state, the expansion difference began to increase.

See Figure 2, the schematic diagram of BEST small steam turbine reaching 1000r/min after starting;

1) Figure 2 mainly shows the operating conditions of the BEST small steam turbine reaching 1000r/min after starting;

2) The line numbered 1 is the speed of the BEST small steam turbine, the line numbered 2 is the expansion difference of the BEST small steam turbine, the line numbered 3 is the feedback of the opening degree of the steam supply valve of the BEST small steam turbine, and the line numbered 4 is the shaft of the BEST small steam turbine Sealed steam supply temperature, the line numbered 5 is the pressure of the BEST small steam turbine shaft seal main pipe, the line numbered 6 is the feedback of the bypass valve opening of the BEST small steam turbine, and the line numbered 7 is the exhaust pressure of the BEST small steam turbine;

3) At 16:45:07, the line numbered 1 is the BEST small steam turbine with a BEST speed of 1000.14r/min, the line numbered 2 is the expansion difference of the BEST small steam turbine is 1.38mm, and the line numbered 3 is the BEST small steam turbine The feedback of the opening of the steam supply regulating valve is 4.83%, the line No. 4 is the steam supply temperature of the BEST small steam turbine shaft seal is 156.55°C, the line No. 5 is the pressure of the main pipe of the BEST small steam turbine shaft seal is -0.72kPa, and the line No. 6 is The line is the feedback of the opening of the bypass valve of the BEST small steam turbine is 99.78%, and the line numbered 7 is the exhaust pressure of the BEST small steam turbine is 0MPa;

4) At this time, the BEST small steam turbine has successfully started up to 1000r/min and started to enter the warm-up state. The BEST small steam turbine is maintained at a certain speed, and the steam passes through the BEST small steam turbine to make the rotor and cylinder evenly heated and expanded. Bends are slowly straightened. At the same time, through the warm-up of the BEST small steam turbine, the cylinder body can be fully expanded to prevent the differential expansion between the BEST small steam turbine rotor and the cylinder body due to the rapid expansion of the rotor, which will cause friction between the BEST small steam turbine static and static, resulting in the BEST small steam turbine. Turbine vibration. Through the warm-up of the BEST small steam turbine, the internal metal temperature of the rotor center hole is higher than the brittle transition temperature;

5) The expansion difference of BEST small steam turbine is the change displacement of the relative axial position between the cylinder body and the rotor in a certain section, which is the difference between the axial expansion of the rotor and the cylinder body, which is called the relative expansion difference between the rotor and the cylinder body. The expansion difference of the BEST small steam turbine is mainly affected by three factors: one is the difference between the thermal expansion displacement of the rotor and the cylinder block, the other is the displacement of the rotor shortened by the centrifugal force when the rotor rotates, and the third is the axial displacement of the rotor at the thrust bearing quantity;

The theoretical formula for differential expansion is:

Z=Za-Zb+Zc-Zd

Among them, Z is the expansion difference, Za is the thermal expansion of the rotor, Zb is the deformation of the rotor due to centrifugal force, Zc is the axial displacement of the rotor, and Zd is the thermal expansion of the cylinder;

6) In the warm-up state, the opening of the BEST small steam turbine steam supply control valve has gradually been fully closed, and the BEST small steam turbine bypass valve is fully open, allowing a large amount of steam to flow into the rotor and cylinder, because The mass-to-surface ratio of the rotor is small and the mass-to-surface ratio of the cylinder is large, so that the thermal expansion speeds of the rotor and the cylinder are no longer consistent, and the expansion difference begins to increase gradually, approaching the trip value, which seriously threatens the start-up of the BEST small steam turbine.

See Figure 3, the schematic diagram of BEST small steam turbine reaching 2400r/min after starting;

1) Figure 3 mainly shows the operating condition of the BEST small steam turbine reaching 2400r/min after starting;

2) The line numbered 1 is the speed of the BEST small steam turbine, the line numbered 2 is the expansion difference of the BEST small steam turbine, the line numbered 3 is the feedback of the opening degree of the steam supply valve of the BEST small steam turbine, and the line numbered 4 is the shaft of the BEST small steam turbine Sealed steam supply temperature, the line numbered 5 is the pressure of the BEST small steam turbine shaft seal main pipe, the line numbered 6 is the feedback of the bypass valve opening of the BEST small steam turbine, and the line numbered 7 is the exhaust pressure of the BEST small steam turbine;

3) At 16:45:07, the line numbered 1 is the BEST small steam turbine with a BEST speed of 2441.11r/min, the line numbered 2 is the expansion difference of the BEST small steam turbine is 1.61mm, and the line numbered 3 is the BEST small steam turbine The feedback of the opening of the steam supply regulating valve is 5.18%, the line No. 4 is the steam supply temperature of the BEST small steam turbine shaft seal is 155.9°C, the line No. 5 is the pressure of the main pipe of the BEST small steam turbine shaft seal is -0.71kPa, and the line No. 6 is The line is the feedback of the opening of the bypass valve of the BEST small steam turbine is 99.75%, and the line numbered 7 is the exhaust pressure of the BEST small steam turbine is 0MPa;

4) At this time, the BEST small steam turbine has successfully started and completed the warm-up process at 1000r/min, the speed has risen to above 2400r/min, the No. 7 low-pressure heater is put into operation and the primary low-temperature reheat steam inlet valve is opened, and the exhaust steam is switched at the same time Finish. Through this stage, it can be found that after the warm-up of the BEST small steam turbine is completed, the expansion difference has not been improved, and the thermal expansion speed of the rotor is still greater than the expansion speed of the cylinder block and is close to the trip value. METS protection will be triggered at any time, causing the unit to stop.

Refer to Figure 4 for the existing BEST small steam turbine bypass valve control system. In application, after the BEST small steam turbine starts and reaches 1000r/min, the BEST small steam turbine is in a warm-up state and the bypass valve is fully open. The fully opened BEST small steam turbine bypass valve has too much influence on the expansion speed of the rotor and cylinder, resulting in an increase in expansion difference; in view of such problems, it is necessary to optimize the original control system of the BEST small steam turbine bypass valve shown in Figure 4 , to avoid the problem that when the BEST small steam turbine is in the warm-up state, the bypass valve is fully open and the steam flow increases, which makes the expansion difference gradually increase.

Referring to Fig. 5, based on this, the present invention designs a new control system of the BEST small steam turbine bypass valve, which includes the input port B001 of the difference between the BEST actual back pressure and the back pressure set value, the BEST final stage pressure ratio setting and the actual pressure ratio Difference input terminal B002, BEST small steam turbine start-up sequence control feedback terminal B003, No. 7 and No. 8 low-load cut-off feedback terminals B004, BEST bypass valve full-close feedback terminal B005, bypass valve valve position control manual mode feedback terminal B006, Feedback terminal B007 for No. 8 low plus cut-off, BEST small steam turbine tripping feedback terminal B008, the first two-to-one switching block B009, the first non-block B010, the first and block B011, RS trigger B012, the second and block B013, the first One or block B014, second non-block B015, small machine shaft seal program control command 4 feedback terminal B016, BEST small steam turbine sequential control step 8 feedback terminal B017, bypass valve quick-open solenoid valve live command feedback terminal B018, BEST small steam turbine Bypass valve opening output module B019, first pulse block B020, second pulse block B021, third pulse block B022, first analog constant block B023, second analog constant block B024, third analog constant block B025 , the second or block B026, the second one-two switching block B027, the third two-one switching block B028, the first PID controller B029, the first F(x) function block B030, the BEST small steam turbine differential expansion input terminal B031 , the first subtraction block B032, greater than the comparison block B033, the second PID controller B034, the limiter block B035, the second F (x) function block B036 and the second subtraction block B037;

The BEST small steam turbine startup sequence control feedback terminal B003 is connected to the input terminal of the first non-block B011 through the first non-block B010, and the No. 7 and No. 8 low-plus cut-off feedback terminals B004 are connected to the input terminal of the first and block B011. The output terminal of the first AND block B011 is connected with the S terminal of the RS flip-flop B012;

The No. 8 low-plus cut-off feedback terminal B007 is connected to the input terminal of the second non-block B013 through the second non-block B015, the BEST bypass valve full-close feedback terminal B005 and the bypass valve valve position control manual mode feedback terminal B006 are connected to the second non-block B015. Connect to the input terminal of block B013, the second output terminal of block B013 and the BEST small steam turbine trip feedback terminal B008 are connected to the first or input terminal of block B014, and the output terminal of first or block B014 is connected to RS flip-flop B012 The R terminal is connected;

The DV terminal of the RS flip-flop B012 is connected to the EN terminal of the first one-two switching block B009, the difference input terminal B001 of the BEST actual back pressure and the back pressure setting value and the difference between the BEST final stage pressure ratio setting and the actual pressure ratio The difference input terminal B002 is connected to the input terminal of the first two-to-one switch block B009; the RV terminal of the RS flip-flop B012 is connected to the EN terminal of the third two-to-one switch block B028 and the EN terminal of the second two-to-one switch block B027 connected;

Small machine shaft seal program control instruction 4 feedback terminal B016 is connected to the input terminal of the second or block B026 through the first pulse block B020, and the feedback terminal B017 of the eighth step of BEST small steam turbine sequence control is connected to the second or block through the second pulse block B021 The input terminal of B026 is connected, the BEST small steam turbine tripping feedback terminal B008 is connected to the input terminal of the second or block B026 through the third pulse block B022, the bypass valve quick-open solenoid valve live command feedback terminal B018 is connected to the second or block B026 The input terminals of the first analog constant block B023, the second analog constant block B024, the third analog constant block B025, the output end of the second or block B026, and the output end of the second alternative switching block B027 And the output end of the third two-to-one switching block B028 is connected with the E end, H end, L end, TR end, TS end, Kp end and Ti end of the first PID controller B029 respectively;

The output end of the first PID controller B029 is connected with the input end of the second subtraction block B037 through the first F (x) function block B030; The input terminal of the comparison block B033 is connected, the output terminal of the first subtraction block B032 and the output terminal of the comparison block are connected with the input terminal of the second PID controller B034, and the output terminal of the second PID controller B034 is passed through the limiter block B035 And the second F(x) function block B036 is connected with the input end of the second subtraction block B037, and the output end of the second subtraction block B037 is connected with the BEST small steam turbine bypass valve opening output module B019.

When working, use the second F(x) function block B036 to calculate the deviation value of the expansion difference in advance, corresponding to the need to reduce the opening of the bypass valve, and then use the first F(x) function block B030 to calculate the actual deviation value corresponding to the opening of the bypass valve, the two are subtracted by the second subtraction block B037 to obtain when the expansion difference increases, and use this to control the opening of the bypass valve of the BEST small steam turbine;

Through the present invention, when the BEST small steam turbine is in the warm-up state, if the expansion difference gradually increases, the opening of the bypass valve of the BEST small steam turbine will be appropriately reduced through the expansion difference monitoring device, and the warm-up of the BEST small steam turbine will be increased. Time, to reduce the influence of steam on the expansion speed of the rotor and cylinder, and avoid further increase of expansion difference.

Referring to Figure 6, after the BEST small steam turbine starts to reach 1000r/min, the BEST small steam turbine is in a warm-up state and the bypass valve is fully open, and the steam passes through the fully open BEST small steam turbine bypass valve to the rotor and cylinder. The influence of the expansion speed is too large, resulting in an increase in the expansion difference. To solve this problem, it is necessary to optimize the original control system for the difference between the actual back pressure of the BEST small steam turbine and the set value of the back pressure in Figure 6, so as to avoid that the BEST small steam turbine is warm. In the engine state, the bypass valve is in a fully open state, resulting in an increase in the steam flow rate, which causes the problem of a gradual increase in the expansion difference.

Referring to Fig. 7, based on this, the new control system for the difference between the actual back pressure of the BEST small steam turbine and the set value of the back pressure according to the present invention includes a BEST exhaust pressure input terminal D001, a BEST delay back pressure set value input terminal D002, Multiplication block D003, BEST actual back pressure and back pressure setting difference output module D004, third F(x) function block D005, addition block D006, fourth two-to-one switching block D007 and third subtraction block D008;

The BEST small steam turbine expansion difference input terminal B031 is connected to the input terminal of the addition block D006 through the third F(x) function block D005, and the BEST delay back pressure set value input terminal D002 is connected to the input terminal of the addition block D006; BEST The exhaust pressure input terminal D001 is connected to the input terminal of the fourth one-of-two switching block D007 and the input terminal of the third subtraction block D008;

The bypass valve position control manual mode feedback terminal B006 and the output terminal of the addition block D006 are connected to the input terminal of the fourth two-to-one switch block D007, and the output terminal of the fourth two-to-one switch block D007 is connected to the third subtraction block D008 The input end of the third subtraction block D008 is connected to the input end of the multiplication block D003, and the output end of the multiplication block D003 is connected to the output module D004 of the difference between the BEST actual back pressure and the back pressure set value.

According to the present invention, when the BEST small steam turbine is in the warm-up state, if the expansion difference gradually increases, the opening of the bypass valve will be appropriately reduced through the expansion difference monitoring device, and the warm-up time of the BEST small steam turbine will be increased. Reduce the influence of steam on the expansion speed of the rotor and cylinder to avoid further increase of expansion difference.

Claims (5)

1. A control system for improving the impulse efficiency when a BEST small turbine is started is characterized by comprising a BEST small turbine bypass valve control system and a BEST small turbine actual back pressure and back pressure set value difference control system.

2. The control system for increasing the shoot-through efficiency at startup of a small turbine BEST as claimed in claim 1, wherein the control system for the bypass valve of the small turbine BEST comprises a difference input terminal (B001) between the actual backpressure and the backpressure set value, a difference input terminal (B002) between the BEST final pressure ratio setting and the actual pressure ratio, a pilot start compliance feedback terminal (B003), low cut feedback terminals (B004) of numbers 7 and 8, a pilot bypass full close feedback terminal (B005), a bypass valve position control manual mode feedback terminal (B006), a low cut feedback terminal (B007) of number 8, a pilot trip feedback terminal (B008), a first optional switching block (B009), a first non-block (B010), a first and block (B011), an RS trigger (B012), a second and block (B013), a first or block (B014), a second non-block (B014), a small shaft command 4 feedback terminal (B016), a pilot feedback terminal (B017) of the pilot poppet 0198, a second and block (B021), a second and analog bypass valve position control input terminal (B022), a second and third analog feedback output terminal (B027), a constant analog feedback terminal (B028), a second and a third analog feedback terminal (B027), a constant control module (B028), a constant control module (B) for the pilot bypass valve, a pilot control module (B022), a pilot control module (B) for the small turbine BEST), a pilot bypass control module, a pilot control module (B028), a pilot control module (B) for controlling a pilot bypass valve, a pilot control module (B) for controlling a pilot The system comprises a first PID controller (B029), a first F (x) function block (B030), a BEST small turbine differential expansion input end (B031), a first subtraction block (B032), a comparison block (B033), a second PID controller (B034), a limiting block (B035), a second F (x) function block (B036) and a second subtraction block (B037);

the start sequence control feedback end (B003) of the BEST small steam turbine is connected with the input end of a first and block (B011) through a first non-block (B010), the low-plus-cut feedback ends (B004) of No. 7 and No. 8 are connected with the input end of the first and block (B011), and the output end of the first and block (B011) is connected with the S end of an RS trigger (B012);

the No. 8 low plus cut feedback end (B007) is connected with the input end of a second and block (B013) through a second non-block (B015), a BEST bypass valve fully-closed feedback end (B005) and a bypass valve position control manual mode feedback end (B006) are connected with the input end of the second and block (B013), the output end of the second and block (B013) and a BEST small turbine tripping feedback end (B008) are connected with the input end of a first or block (B014), and the output end of the first or block (B014) is connected with the R end of an RS trigger (B012);

a DV end of the RS trigger (B012) is connected with an EN end of the first alternative switching block (B009), a difference input end (B001) of BEST actual backpressure and backpressure set value and a difference input end (B002) of BEST final voltage ratio set and actual voltage ratio are connected with an input end of the first alternative switching block (B009); the RV end of the RS trigger (B012) is connected with the EN end of the third alternative switching block (B028) and the EN end of the second alternative switching block (B027);

the feedback end (B016) of a small shaft seal program control command 4 is connected with the input end of a second or block (B026) through a first pulse block (B020), the feedback end (B017) of the 8 th step of forward control of the BEST small steam turbine is connected with the input end of the second or block (B026) through a second pulse block (B021), the tripping feedback end (B008) of the BEST small steam turbine is connected with the input end of the second or block (B026) through a third pulse block (B022), the electrified command feedback end (B018) of a bypass valve quick-opening electromagnetic valve is connected with the input end of the second or block (B026), the output ends of a first analog quantity block (B023), a second analog quantity block (B024), a third analog quantity constant block (B025), the second or block (B026), the output end of a second or constant block (B027), the output end of a second alternative switching block (B027) and the output end of a third alternative switching block (B028) are respectively connected with the E end, the H end and the PID end of a first alternative switching block (B026) of a controller (B029), the T end and the PID end of a Ti end;

the output of the first PID controller (B029) is connected to the input of the second subtraction block (B037) via a first F (x) function block (B030); the small BEST turbine differential expansion input end (B031) is connected with the input end of the first subtraction block (B032) and the input end larger than the comparison block (B033), the output end of the first subtraction block (B032) and the output end of the comparison block are connected with the input end of the second PID controller (B034), the output end of the second PID controller (B034) is connected with the input end of the second subtraction block (B037) through the amplitude limiting block (B035) and the second F (x) function block (B036), and the output end of the second subtraction block (B037) is connected with the small BEST turbine valve opening output module (B019).

3. The control system for improving the impulse efficiency of the small BEST turbine during startup according to claim 2, wherein in operation, the second F (x) function block (B036) is used to calculate the opening degree of the bypass valve of the small BEST turbine corresponding to the deviation value of the swell difference in advance.

4. The system of claim 2, wherein the gradual increase in differential expansion causes the BEST small turbine bypass valve to decrease in opening and increase the BEST small turbine warm-up time.

5. The control system for improving the impulse efficiency when the small BEST turbine is started according to claim 2, wherein the difference control system for the actual backpressure and the backpressure set value of the small BEST turbine comprises a BEST exhaust pressure input end (D001), a BEST delay backpressure set value input end (D002), a multiplication block (D003), a difference output module (D004) for the actual backpressure and the backpressure set value of the BEST, a third F (x) function block (D005), an addition block (D006), a fourth alternative switching block (D007) and a third subtraction block (D008);

the BEST small turbine differential expansion input end (B031) is connected with the input end of the adding block (D006) through a third F (x) function block (D005), and the BEST delay backpressure set value input end (D002) is connected with the input end of the adding block (D006); the BEST exhaust steam pressure input end (D001) is connected with the input end of the fourth alternative switching block (D007) and the input end of the third subtraction block (D008);

the output ends of a bypass valve position control manual mode feedback end (B006) and an addition block (D006) are connected with the input end of a fourth alternative switching block (D007), the output end of the fourth alternative switching block (D007) is connected with the input end of a third subtraction block (D008), the output end of the third subtraction block (D008) is connected with the input end of a multiplication block (D003), and the output end of the multiplication block (D003) is connected with a BEST actual backpressure and backpressure set value difference output module (D004).

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