CN114278395A

CN114278395A - Control system for preventing exhaust overtemperature during startup of BEST small steam turbine

Info

Publication number: CN114278395A
Application number: CN202210096465.6A
Authority: CN
Inventors: 吴青云; 高玉峰; 蔺奕存; 高景辉; 何胜; 王海涛; 杨博; 何洋; 李华
Original assignee: Xian Thermal Power Research Institute Co Ltd
Current assignee: Xian Thermal Power Research Institute Co Ltd
Priority date: 2022-01-26
Filing date: 2022-01-26
Publication date: 2022-04-05

Abstract

The invention discloses a control system for preventing exhaust steam from overtemperature when a BEST small steam turbine is started, which comprises a first logic three-input AND-OR module, a first subtraction module, an amplitude limiting module, a smaller value module, a logic OR module, a first PID module, a logic NOT module, a logic AND module, a first analog quantity switching module, a second subtraction module, a second logic three-input AND-OR module, a second analog quantity switching module, a first addition module, a second addition module, a third analog quantity switching module, a multiplication module, a second PID module and a function conversion module.

Description

Control system for preventing exhaust overtemperature during startup of BEST small steam turbine

Technical Field

The invention belongs to the field of thermal control of a BEST small turbine with a small generator of an ultra-supercritical double-reheating coal-fired unit, and relates to a control system for preventing exhaust steam from being over-heated when the BEST small turbine is started.

Background

With the development of ultra-supercritical double-reheat coal-fired units, BEST small turbines of million-type thermal power units with small generators are applied to thermal power plants. After the BEST small turbine is started by the small turbine control valve, the opening of the valve of the BEST small turbine gradually rises, and the rotating speed value rises to 1000r/min, which is the warming rotating speed. At the moment, the small turbine feed pump is in a converter master control mode, the converter controls the current rotating speed and drags the feed pump to operate through the converter, the BEST small turbine throttle is in a full-open state, the steam inlet flow is increased, and the output power of the small generator is continuously increased. The rotating speed is increased to be more than 2400r/min, the No. 7 low-pressure heater is put in, the primary low-temperature reheating steam inlet valve is opened, and meanwhile, the exhaust switching is finished. In the mode, redundant power is output through the high-speed synchronous motor, and the service requirement of auxiliary power is met.

In the starting operation stage, before the steam source switching is completed, the regulating valve of the BEST small steam turbine is fully opened in a converter master control mode, the steam flow entering the BEST small steam turbine is rapidly increased, the phenomenon that the steam flow passes through the exhaust cylinder to generate overheating can occur, and the exhaust temperature is increased. When the exhaust temperature is too high, the BEST small turbine METS protection can be triggered, and the unit is not stopped.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a control system for preventing the overtemperature of exhaust steam when a BEST small steam turbine is started, which prevents the phenomenon that steam flow passes through an exhaust cylinder to generate overheating before the steam source is not switched and can avoid the overhigh temperature of the exhaust steam.

In order to achieve the purpose, the control system for preventing the exhaust steam from overtemperature during the startup of the BEST small steam turbine comprises a first logic three-input AND-OR module, a first subtraction module, a limiting module, a smaller value module, a logic OR module, a first PID module, a logic NOT module, a logic AND module, a first analog quantity switching module, a second subtraction module, a second logic three-input AND-OR module, a second analog quantity switching module, a first addition module, a second addition module, a third analog quantity switching module, a multiplication module, a second PID module, a function conversion module, a collected exhaust steam temperature 1 signal end, a collected exhaust steam temperature 2 signal end, a collected exhaust steam temperature 3 signal end, a DI block for controlling the exhaust steam source switching and before the exhaust temperature cooling and exiting in the 16 th step of steam source switching, a DI block for controlling the exhaust steam source switching and before the exhaust temperature cooling and outputting in the 16 th step of steam source switching in the sequential control, The device comprises a BEST small turbine delay rotating speed set value input end, a DI block of a converter master control state, a DI block HH of a first BEST small turbine tripping, a DI block of a BEST small turbine primary low-temperature reheating steam inlet valve opened, a DI block of a BEST steam source switching completion 1, a DI block of a BEST steam source switching completion 2, a BEST small turbine actual rotating speed input end, a BEST sequential control 10 th step throttle fully opened DI block, a DI block of a second DBEST small turbine tripping, and a BEST small turbine throttle opening control signal output end;

the control logic module for preventing the exhaust overtemperature is composed of a collected exhaust steam temperature 1 signal end, a collected exhaust steam temperature 2 signal end, a collected exhaust steam temperature 3 signal end, a DI block for cooling and exiting the exhaust steam before the sequential control 16-step steam source switching, a DI block for cooling and outputting the exhaust steam before the sequential control 16-step steam source switching, a first logic three-input AND-OR module, a first subtraction module, an amplitude limiting module, a smaller value module, a logic OR module and a first PID module;

the system comprises a collected exhaust steam temperature 1 signal end, a collected exhaust steam temperature 2 signal end and a collected exhaust steam temperature 3 signal end, wherein the collected exhaust steam temperature 1 signal end, the collected exhaust steam temperature 2 signal end and the collected exhaust steam temperature 3 signal end are connected with the input end of a first logic three-input and OR module, the output end of the first logic three-input and OR module is connected with the input end of a first subtraction module, the output end of the first subtraction module is connected with the input end of an amplitude limiting module, the output end of the amplitude limiting module is connected with the input end of a smaller value module and the input end of a first PID module, the output ends of a DI block for exhaust temperature cooling withdrawal before the switch of a 16 th-step steam source and the smaller value module are connected with the input end of the logic OR module, the output end of the logic OR module is connected with the input end of the first PID module, and the output end of the first PID module is connected with the DI block for exhaust temperature cooling output before the switch of the sequentially controlled 16 th-step steam source;

the DI block of the tripping of the first BEST small turbine is connected with the input end of the logic non-module, and the output end of the logic non-module and the DI block of the main control state of the converter are connected with the input end of the logic and module;

the DI block of the BEST small turbine primary low-temperature reheat steam inlet valve which is opened, the DI block of the BEST steam source switching completion 1 and the DI block of the BEST steam source switching completion 2 are connected with the input end of a second logic three-input and OR module, the output end of the second logic three-input and OR module is connected with the input end of a second analog quantity switching module, the output end of the second analog quantity switching module and the DI block of the exhaust temperature cooling output before the steam source switching in the sequential control 16 th step are connected with the input end of a first addition module, the output end of the first addition module and the actual rotating speed input end of the BEST small turbine are connected with the input end of a second addition module, the output end of the logic and module and the delay rotating speed set value input end of the BEST small turbine are connected with the input end of the first analog quantity switching module, the output end of the first analog quantity switching module and the actual rotating speed input end of the BEST small turbine are connected with the input end of a second subtraction module MM, the output end of the second subtraction module is connected with the input end of the second PID module and the input end of the multiplication module, the output end of the multiplication module is connected with the input end of the second PID module, the DI block of the BEST sequential control 10 th step gate which is fully opened is connected with the input end of the third analog quantity switching module, the output end of the third analog quantity switching module and the DI block of the second BEST small turbine trip-out are connected with the input end of the second PID module, the output end of the second PID module is connected with the input end of the function transformation module, and the output end of the function transformation module is connected with the gate opening control signal output end of the BEST small turbine.

The output of the clipping module is clipped between-10 and 10.

The preset temperature value input by the first subtraction module is 300 ℃.

When the output end of the smaller value module is 0, the actual value of the exhaust steam temperature is larger than the set value 300; when the output end of the smaller value module is 1, the actual value of the exhaust steam temperature is smaller than the set value 300.

When the output of the logic OR module is 0, the actual value of the exhaust steam temperature is larger than the set value 300, or the exhaust temperature cooling exit is not executed before the steam source switching in the 16 th step is controlled sequentially; when the output of the logic or module is 1, it indicates that the actual value of the exhaust steam temperature is less than the set value 300, or the exhaust temperature cooling is quitted before the steam source is switched in the 16 th step of the sequential control.

The invention has the following beneficial effects:

when the control system for preventing the exhaust overtemperature when the BEST small turbine is started is in specific operation, the control logic module for preventing the exhaust overtemperature is added, and is used for controlling the opening of the regulating valve of the BEST small turbine in advance in a master control state of the converter when the steam source is not switched and is overhigh, so that the phenomenon that steam airflow passes through the exhaust cylinder to generate overheat before the steam source is not switched and can be avoided. In addition, the invention adopts a PID control mode to achieve the purpose of closing the small steam turbine valve of BEST in advance, effectively reduce the steam flow and avoid the problem of exhaust overtemperature caused by overlarge steam flow. It should be noted that the invention can control the opening degree of the regulating valve of the small BEST turbine in advance to stabilize the exhaust temperature, complete the steam source switching of the startup sequence control of the small BEST turbine, smoothly execute the startup sequence control steps of the rest small BEST turbines, and realize that the small BEST turbines convert the redundant output into electric energy in the state of 'converter master control'.

Drawings

FIG. 1 is a schematic diagram of a prior art structure;

FIG. 2 is a block diagram of a control logic module for preventing exhaust over-temperature;

fig. 3 is a block diagram of the present invention.

Wherein 001 is a first logical three-input and or module, 002 is a first subtraction module, 003 is a limiting module, 004 is a smaller-value module, 005 is a logical or module, 006 is a first PID module, 007 is a logical non-module, 008 is a logical and module, 009 is a first analog quantity switching module, 010 is a second subtraction module, 011 is a second logical three-input and or module, 012 is a second analog quantity switching module, 013 is a first addition module, 014 is a second addition module, 015 is a third analog quantity switching module, 016 is a multiplication module, 017 is a second PID module, 018 is a function transformation module, AA is a collected exhaust steam temperature 1 signal terminal, BB is a collected exhaust steam temperature 2 signal terminal, CC is a collected exhaust steam temperature 3 signal terminal, DD is a DI block which is cooled and exited before switching of the steam source of the following control 16 th step, EE is a DI block which is cooled and output before switching of the following control 16 th step steam source, and 017 is cooled and output, FF is a BEST small turbine delay rotating speed set value input end, GG is a DI block of a converter master control state, HH is a DI block of a first BEST small turbine tripping, II is a DI block of a BEST small turbine primary low-temperature reheating steam inlet valve opened, JJ is a DI block of BEST steam source switching completion 1, KK is a DI block of BEST steam source switching completion 2, MM is a BEST small turbine actual rotating speed input end, NN is a DI block of BEST sequential control 10 th step throttle full opening, OO is a DI block of a second DBEST small turbine tripping, and PP is a BEST small turbine throttle opening control signal output end.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments, and are not intended to limit the scope of the present disclosure. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present disclosure. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

There is shown in the drawings a schematic block diagram of a disclosed embodiment in accordance with the invention. The figures are not drawn to scale, wherein certain details are exaggerated and possibly omitted for clarity of presentation. The shapes of various regions, layers and their relative sizes and positional relationships shown in the drawings are merely exemplary, and deviations may occur in practice due to manufacturing tolerances or technical limitations, and a person skilled in the art may additionally design regions/layers having different shapes, sizes, relative positions, according to actual needs.

Referring to fig. 1, in the prior art, the hidden danger before switching the air source in the 16 th sequential control step is not considered, when the air source is not switched and is in the "converter master control" state, the small BEST turbine throttle is already in the fully open state in the 10 th sequential control step, and as the rotating speed is increased, the steam flow entering the small BEST turbine is rapidly increased, so that the phenomenon that the steam flow passes through the exhaust cylinder to generate overheating occurs, and the exhaust temperature is increased.

The invention can effectively solve the problems, is suitable for controlling the opening of the regulating valve of the BEST small turbine in time through the 'converter master control' state if the exhaust temperature is increased when the steam source is not switched at the starting stage of the BEST small turbine, reduces the steam flow and prevents the hidden trouble of exhaust overtemperature.

Referring to fig. 2 and 3, the control system for preventing exhaust steam from overtemperature when the small BEST turbine is started according to the present invention includes a first logical three-input and or module 001, a first subtraction module 002, a limiting module 003, a smaller-ratio module 004, a logical or module 005, a first PID module 006, a logical non-module 007, a logical and module 008, a first analog switching module 009, a second subtraction module 010, a second logical three-input and or module 011, a second analog switching module 012, a first addition module 013, a second addition module 014, a third analog switching module 015, a multiplication module 016, a second PID module 017, a function transformation module 018, a collected exhaust steam temperature 1 signal terminal AA, a collected exhaust steam temperature 2 signal terminal BB, a collected exhaust steam temperature 3 signal terminal CC, a DI block DD, a collected exhaust steam temperature before the 16 th step of steam source switching exits cooling, a sequential control module DD, a sequential control module b, a sequential control module, and a sequential control module, wherein the sequential control module are included in which is performed in order, and a sequential control module, and a control module are included in which are included in the control module, and the control module is included in which are included in, The system comprises a DI block EE for forward control of exhaust temperature cooling output before switching of a 16 th step steam source, a BEST small steam turbine delay rotating speed set value input end FF, a DI block GG of a converter master control state, a DI block HH for tripping of a first BEST small steam turbine, a DI block II for opening a BEST small steam turbine primary low-temperature reheating steam inlet valve, a DI block JJ for completing switching of a BEST steam source 1, a DI block KK for completing switching of a BEST steam source 2, an actual rotating speed input end MM of the BEST small steam turbine, a DBST forward control 10 th step door fully-opened DI block NN, a DI block OO for tripping of a second BEST small steam turbine and a BEST small steam turbine door opening control signal output end PP;

the collected exhaust steam temperature 1 signal end AA, the collected exhaust steam temperature 2 signal end BB and the collected exhaust steam temperature 3 signal end CC are connected with the input end of a first logic three-input AND/OR module 001, the output end of the first logic three-input and or module 001 is connected with the input end of the first subtraction module 002, the output end of the first subtraction module 002 is connected with the input end of the amplitude limiting module 003, the output end of the amplitude limiting module 003 is connected with the input end of the smaller-value module 004 and the input end of the first PID module 006, the output end of the DI block DD for cooling and exiting the exhaust temperature before the steam source switching of the 16 th step and the output end of the smaller-value module 004 are connected with the input end of the logic or module 005, the output end of the logic or module 005 is connected with the input end of the first PID module 006, and the output end of the first PID module 006 is connected with the DI block EE for cooling and outputting the exhaust temperature before the steam source switching of the 16 th step;

the DI block HH of the tripping small turbine of the first BEST is connected with the input end of the logic NOT module 007, and the output end of the logic NOT module 007 and the DI block GG of the main control state of the converter are connected with the input end of the logic AND module 008;

the DI block II of the BEST small turbine primary low-temperature reheat steam inlet valve which is opened, the DI block JJ of the BEST steam source switching completion 1 and the DI block KK of the BEST steam source switching completion 2 are connected with the input end of a second logic three-input and OR module 011, the output end of the second logic three-input and OR module 011 is connected with the input end of a second analog quantity switching module 012, the output end of the second analog quantity switching module 012 and the DI block EE of the exhaust temperature cooling output before the steam source switching of the sequence control 16 step 16 are connected with the input end of a first addition module 013, the output end of the first addition module 013 and the actual rotating speed input end MM of the BEST small turbine are connected with the input end of a second addition module 014, the output end of the logic and module 008 and the delay rotating speed set value FF of the BEST small turbine are connected with the input end of a first analog quantity switching module 009, the output end of the first analog quantity switching module 009 and the actual rotating speed input end of the BEST small turbine are connected with the second analog quantity switching module 014 The input end of module 010 is connected, the output end of second subtraction module 010 is connected with the input end of second PID module 017 and the input end of multiplication module 016, the output end of multiplication module 016 is connected with the input end of second PID module 017, BEST is in the same direction as the DI block NN that accuse 10 th step governing door was opened entirely is connected with the input end of third analog quantity switch module 015, the output end of third analog quantity switch module 015 and the DI block OO that little turbine of second BEST tripped are connected with the input end of second PID module 017, the output end of second PID module 017 is connected with the input end of function transform module 018, the output end of function transform module 018 is connected with BEST little turbine governing door opening control signal output end PP.

When the device works, the amplitude of the output end of the amplitude limiting module 003 is between-10 and 10, the other input of the smaller value module 004 is 0, and when the output end of the smaller value module 004 is 0, the actual value of the exhaust steam temperature is larger than the set value 300; when the output of the smaller value module 004 is 1, it indicates that the actual value of the exhaust steam temperature is less than the set value 300. When the output of the or logic 005 is 0, it indicates that the actual value of the exhaust steam temperature is greater than the set value 300, or the exhaust temperature cooling exit is not performed before the steam source is switched in the 16 th step of the sequential control. When the output of the or logic 005 is 1, it indicates that the actual value of the exhaust steam temperature is less than the set value 300, or the exhaust temperature cooling is exited before the steam source is switched in the sequence 16. And adding a DI block DD for cooling and exiting the exhaust temperature before the steam source switching in the 16 th step of sequential control to the 16 th step of starting sequential control, and after the edge switching is finished, cooling and exiting the exhaust temperature before the steam source switching in the 16 th step of sequential control. The output terminal of the or logic module 005 is used as the input terminal TS of the first PID module 006, and when the TS tracking switch is 0, the first PID module 006 performs calculation according to the input deviation to control the problem of excessive exhaust temperature before the 16 th step of the sequential control. When the TS tracking switch is 1, the tracking value of the first PID module 006 is 0 to output the result, and at this time, the logic does not control the exhaust over-temperature problem.

After a control logic module for preventing exhaust overtemperature is added, when the exhaust temperature is high, after the control logic module for preventing exhaust overtemperature is used for operation, the output value is the exhaust temperature cooling output before the steam source switching of the sequence control 16 th step, the output value of the control logic module for preventing exhaust overtemperature and the actual rotating speed of the small turbine at the actual rotating speed input end MM of the BEST small turbine are added through a second adding module 014 to obtain the rotating speed set value of the BEST small turbine, a deviation value is calculated through a second subtraction module 010, and finally, the operation is carried out through a second PID module 017, so that the purpose of closing the gate of the BEST small turbine in advance is achieved, the steam intake is reduced, and the exhaust overtemperature is prevented.

Claims

1. The utility model provides a control system for prevent exhaust steam overtemperature when small steam turbine of BEST starts, peculiar in, including first logic three input and or module (001), first subtraction module (002), limit module (003), less than module (004), logic or module (005), first PID module (006), logic not module (007), logic and module (008), first analog quantity switching module (009), second subtraction module (010), second logic three input and or module (011), second analog quantity switching module (012), first addition module (013), second addition module (014), third analog quantity switching module (015), multiplication module (016), second PID module (017), function conversion module (018), exhaust steam temperature 1 signal end (AA) of collection, exhaust steam temperature 2 signal end (BB) of collection, exhaust steam temperature 3 signal end (CC) of collection, The system comprises a DI block (DD) for cooling and exiting exhaust gas before the steam source is switched in a forward control 16 th step, a DI block (EE) for cooling and outputting exhaust gas before the steam source is switched in the forward control 16 th step, a BEST small steam turbine delay rotating speed set value input end (FF), a DI block (GG) of a converter master control state, a DI block (HH) tripped by a first BEST small steam turbine, a DI block (II) opened by a BEST small steam turbine primary low-temperature reheating steam inlet valve, a DI block (JJ) completed by BEST steam source switching 1, a DI block (KK) completed by BEST steam source switching 2, an actual rotating speed input end (MM) of the BEST small steam turbine, a DI block (NN) fully opened by a BEST forward control 10 th step throttle, a DI block (OO) tripped by a second DBEST small steam turbine and a BEST small steam turbine opening control signal output end (PP);

the control logic module for preventing the exhaust overtemperature comprises an acquired exhaust steam temperature 1 signal end (AA), an acquired exhaust steam temperature 2 signal end (BB), an acquired exhaust steam temperature 3 signal end (CC), a DI block (DD) for cooling and exiting exhaust before the steam source is switched in the sequential control 16 step, a DI block (EE) for cooling and outputting the exhaust temperature before the steam source is switched in the sequential control 16 step, a first logic three-input AND (OR) module (001), a first subtraction module (002), an amplitude limiting module (003), a smaller ratio module (004), a logic OR module (005) and a first PID (proportion integration differentiation) module (006);

the collected exhaust steam temperature 1 signal end (AA), the collected exhaust steam temperature 2 signal end (BB) and the collected exhaust steam temperature 3 signal end (CC) are connected with the input end of a first logic three-input and OR module (001), the output end of the first logic three-input and OR module (001) is connected with the input end of a first subtraction module (002), the output end of the first subtraction module (002) is connected with the input end of an amplitude limiting module (003), the output end of the amplitude limiting module (003) is connected with the input end of a smaller-value module (004) and the input end of a first PID module (006), the output end of a DI block (DD) which is used for cooling and withdrawing the exhaust temperature before the 16-step steam source is switched and the output end of the smaller-value module (004) are connected with the input end of a logic OR module (005), and the output end of the logic OR module (005) is connected with the input end of the first PID module (006), the output end of the first PID module (006) is connected with a DI block (EE) for the cooling output of the exhaust gas temperature before the steam source switching in the 16 th step in the sequential control;

the DI block (HH) of the tripping of the first BEST small turbine is connected with the input end of a logic NOT module (007), and the output end of the logic NOT module (007) and the DI block (GG) of the main control state of the converter are connected with the input end of a logic AND module (008);

the DI block (II) of a BEST small turbine primary low-temperature reheat steam inlet valve which is opened, the DI block (JJ) of a BEST steam source switching completion 1 and the DI block (KK) of a BEST steam source switching completion 2 are connected with the input end of a second logic three-input and OR module (011), the output end of the second logic three-input and OR module (011) is connected with the input end of a second analog quantity switching module (012), the output end of the second analog quantity switching module (012) and the DI block (EE) of exhaust temperature cooling output before the steam source switching of a 16 th step are controlled in sequence are connected with the input end of a first addition module (013), the output end of the first addition module (013) and the BEST small turbine actual rotating speed input end (MM) are connected with the input end of a second addition module (014), the output end of the second addition module (014), the output end of a logic and module (008) and the BEST small turbine delay rotating speed set value (FF) are connected with the input end of a first analog quantity switching module (009), the output end of a first analog quantity switching module (009) and the actual rotating speed input end (MM) of the BEST small turbine are connected with the input end of a second subtraction module (010), the output end of the second subtraction module (010) is connected with the input end of a second PID module (017) and the input end of a multiplication module (016), the output end of the multiplication module (016) is connected with the input end of the second PID module (017), a DI block (NN) of the BEST sequential control 10-step governing door fully opened is connected with the input end of a third analog quantity switching module (015), the output end of the third analog quantity switching module (015) and a DI block (OO) of the second BEST small turbine tripping are connected with the input end of the second PID module (017), the output end of the second PID module (017) is connected with the input end of a function transformation module (018), and the output end of the function transformation module (018) is connected with the opening degree control signal output end (PP) of the BEST small turbine.

2. The control system for preventing exhaust steam overtemperature at startup of a BEST small turbine as claimed in claim 1, characterized in that the output of the limiting module (003) is limited to between-10 and 10.

3. The control system for preventing over-temperature of exhaust steam at startup of a BEST small turbine according to claim 1, peculiar in that the preset temperature value inputted by the first subtraction module (002) is 300 ℃.

4. The control system for preventing exhaust overtemperature at startup of a BEST small turbine according to claim 1, particularly in that when the output of the smaller value module (004) is 0, it indicates that the actual value of the exhaust steam temperature is greater than the set value of 300; when the output end of the smaller value module (004) is 1, the actual value of the exhaust steam temperature is smaller than the set value 300.

5. The control system for preventing the excessive temperature of the exhaust steam when the small BEST turbine is started according to claim 1, wherein if the output of the logical or module (005) is 0, the actual value of the exhaust steam temperature is larger than the set value 300, or the cooling and the exit of the exhaust steam temperature are not executed before the steam source is switched in the 16 th step; when the output of the or logic (005) is 1, it indicates that the actual value of the exhaust steam temperature is less than the set value 300, or the exhaust temperature cooling is exited before the steam source is switched in the 16 th step of the sequential control.