CN104075340A - Low-nitrogen combustion control method and system based on PLC - Google Patents
Low-nitrogen combustion control method and system based on PLC Download PDFInfo
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- CN104075340A CN104075340A CN201410341338.3A CN201410341338A CN104075340A CN 104075340 A CN104075340 A CN 104075340A CN 201410341338 A CN201410341338 A CN 201410341338A CN 104075340 A CN104075340 A CN 104075340A
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Abstract
The invention discloses a low-nitrogen combustion control method and system based on a PLC. The programmable logic controller (PLC) obtains a secondary air door opening degree instruction and a separate over fire air (SOFA) air door opening degree instruction which correspond to each other from a preset low-nitrogen combustion control model and obtains corresponding nitrogen oxide emission target values according to boiler running parameters fed back by a distributed control system (DCS), and therefore the DCS can control a secondary air door and a corresponding SOFA air door according to the secondary air door opening degree instruction and the SOFA air door opening degree instruction. The PLC determines the polarization amount of the SOFA air door according to the actually-measured nitrogen oxide value fed back by the DCS and the current nitrogen oxide emission target value. The PLC overlays the polarization amount of the SOFA air door with the current SOFA air door opening degree instruction obtained from the low-nitrogen combustion control model so that a corrected SOFA air door opening degree instruction can be obtained and the DCS can control the SOFA air door according to the corrected SOFA air door opening degree instruction. Thus, low-nitrogen combustion control over boilers can be effectively achieved, and economical, environment-friendly and optimized running of the boilers is achieved.
Description
Technical field
The present invention relates to boiler optimization burning control field, particularly a kind of low nitrogen burning control method and system based on PLC.
Background technology
Within 2012, national environmental protection portion has put into effect new < < fossil-fuel power plant atmospheric pollutant emission standard > >, the strict discharge standard of nitrogen oxide (NOx) of clearly having stipulated coal-burning power plant, domestic coal-burning power plant has carried out the low nitrogen burning improvement project for boiler in succession.After low nitrogen burning improvement project completes, obtain desirable low nitrogen burning effect, should consider that boiler efficiency takes into account discharged nitrous oxides again, this just requires to handle well coal dust, Secondary Air and separate type after-flame wind simultaneously, and (Separate Over Fire Air is called for short: proportion relation SOFA).
At present, adopting on the coal-fired plant boiler of low nitrogen burning technology, general employing by load instruction regulates the method for primary combustion zone Secondary Air and SOFA wind to adjust burning, control the discharge of nitrogen oxide, by load-air quantity (Secondary Air and SOFA wind air quantity), set the aperture that function F (x) is controlled each air door.The realization of this control mode realizes by the configuration of DCS (Distributed Control System, dcs) system standard algorithmic block.
The above-mentioned mode of air distribution of controlling by load-air quantity setting function F (x) based on DCS system, Consideration only has load, and when determination of power load, each Secondary Air and SOFA wind air distribution scheme are also determined.Under this control mode, load does not change, but when the factors such as boiler ature of coal, operation of coal pulverizing mills, discharged nitrous oxides change, boiler combustion characteristic also changes thereupon, original Secondary Air and the inapplicable combustion characteristics now of SOFA wind air distribution scheme, under this control mode, Secondary Air and SOFA wind air distribution scheme can not synchronously be adjusted with boiler combustion characteristic, cause air distribution scheme not mate with combustion characteristics demand, finally cause the discharge of NOx value all to affect adversely with boiler combustion efficiency.This control mode is a kind of control mode of extensive style comparatively speaking, does not possess the ability of low nitrogen burning optimum control when the factor changes such as boiler ature of coal, operation of coal pulverizing mills, NOx discharge.
Summary of the invention
The embodiment of the present invention provides a kind of low nitrogen burning control method and system based on PLC, Programmable Logic Controller PLC determines the instruction of corresponding secondary air register aperture and the instruction of SOFA air door according to the boiler operating parameter of DCS feedback, and according to nitrogen oxide measured value to SOFA air door instruction revise, thereby the low nitrogen burning of effectively realizing boiler is controlled.
According to an aspect of the present invention, provide a kind of low nitrogen burning control method based on PLC, comprising:
Programmable Logic Controller PLC is according to the boiler operating parameter of dcs DCS feedback, at the low nitrogen burning setting in advance, control in model and obtain corresponding secondary air register aperture instruction and the instruction of separate type after-flame wind SOFA throttle opening, and corresponding discharged nitrous oxides desired value;
PLC sends to DCS by the instruction of secondary air register aperture and the instruction of SOFA throttle opening, so that DCS utilizes the instruction of secondary air register aperture and the instruction of SOFA throttle opening respectively secondary air register and SOFA air door to be controlled;
PLC, according to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determines SOFA air door amount of bias;
PLC is by SOFA air door amount of bias and current SOFA throttle opening instruction stack of obtaining from low nitrogen burning control model, to obtain calibrated SOFA throttle opening instruction;
PLC sends to DCS by calibrated SOFA throttle opening instruction, so that DCS utilizes calibrated SOFA throttle opening instruction to control SOFA air door.
In one embodiment, PLC is by boiler operating parameter and the nitrogen oxide measured value of DCS feedback, and corresponding secondary air register aperture instruction, the instruction of SOFA throttle opening and SOFA air door amount of bias store low nitrogen burning into and control in model, to revise Optimizing Combustion, control model.
In one embodiment, PLC, according to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determines that the step of SOFA air door amount of bias comprises:
PLC, when arriving n computing cycle, calculates current discharged nitrous oxides desired value SP
nwith current nitrogen oxide measured value PV
ndifference Error
n;
Determine Error
naffiliated interval X and Error
n-1affiliated interval Y;
According to interval X and Y, determine corresponding control parameter Z, wherein control parameter Z and comprise proportionality coefficient C
p, integral coefficient C
i, differential coefficient C
d;
Calculate the PID output PIDOUT of n computing cycle
n, PIDOUT wherein
n=M
p,n+ M
i,n+ M
d,n=C
p* Error
n+ (M
i, n-1+ C
i* Error
n-1)+C
d* (PV
n-1-PV
n), M
p,nbe the PID ratio output quantity in n computing cycle, M
i,nbe the integration output quantity in n computing cycle, M
d,nit is the differential output quantity in n computing cycle;
By PIDOUT
nbe converted into corresponding SOFA air door amount of bias.
In one embodiment, after determining the step of corresponding control parameter Z according to interval X and Y, also comprise:
Whether judgement controls parameter Z for enabling first;
If controlling parameter Z is not to enable first, carry out the PID output PIDOUT that calculates n computing cycle
nstep;
If control parameter Z for enabling first, to the integration output quantity M in n-1 computing cycle
i, n-1initialize M
i, n-1=PIDOUT
n-1-M
p,n+ M
d,n, then carry out the PID output PIDOUT that calculates n computing cycle
nstep.
In one embodiment, Error
n=a* (SP
n-PV
nthe * of)+(1-a) Error
n-1;
Wherein a is filter factor.
In one embodiment, DCS after receiving the instruction that PLC sends, judge current self whether in low nitrogen burning control model, there is exiting when abnormal low nitrogen burning control model judgement and communicating by letter of PLC in DCS wherein;
If current self in low nitrogen burning control model, whether the parameter in the further decision instruction of DCS effectively, whether parameter rate of change in preset range;
If the parameter in instruction effectively and parameter rate of change in preset range, DCS utilizes instruction to control corresponding air door;
If the invalid parameters in instruction, or parameter rate of change exceeds preset range, the instruction that execution of DCS refusal receives.
According to a further aspect in the invention, provide a kind of low nitrogen burning control system based on PLC, comprise Programmable Logic Controller PLC and dcs DCS, wherein:
DCS, for feeding back boiler operating parameter and nitrogen oxide measured value to PLC, when receiving secondary air register aperture instruction that PLC sends and the instruction of separate type after-flame wind SOFA throttle opening, utilize the instruction of secondary air register aperture and the instruction of SOFA throttle opening respectively secondary air register and SOFA air door to be controlled; When receive that PLC sends calibrated SOFA throttle opening instruction time, utilize calibrated SOFA throttle opening instruction to control SOFA air door;
PLC, for according to the boiler operating parameter of DCS feedback, controls in model and obtains corresponding secondary air register aperture instruction and the instruction of SOFA throttle opening at the low nitrogen burning setting in advance, and corresponding discharged nitrous oxides desired value; The instruction of secondary air register aperture and the instruction of SOFA throttle opening are sent to DCS; According to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determine SOFA air door amount of bias; By SOFA air door amount of bias and current SOFA throttle opening instruction stack of obtaining, to obtain calibrated SOFA throttle opening instruction, calibrated SOFA throttle opening instruction is sent to DCS from low nitrogen burning control model.
In one embodiment, PLC is boiler operating parameter and the nitrogen oxide measured value for DCS is fed back also, and corresponding secondary air register aperture instruction, the instruction of SOFA throttle opening and SOFA air door amount of bias store low nitrogen burning into and control in model, to revise Optimizing Combustion, control model.
In one embodiment, PLC specifically, when arriving n computing cycle, calculates current discharged nitrous oxides desired value SP
nwith current nitrogen oxide measured value PV
ndifference Error
n; Determine Error
naffiliated interval X and Error
n-1affiliated interval Y; According to interval X and Y, determine corresponding control parameter Z, wherein control parameter Z and comprise proportionality coefficient C
p, integral coefficient C
i, differential coefficient C
d; Calculate the PID output PIDOUT of n computing cycle
n, PIDOUT wherein
n=M
p,n+ M
i,n+ M
d,n=C
p* Error
n+ (M
i, n-1+ C
i* Error
n-1)+C
d* (PV
n-1-PV
n), M
p,nbe the PID ratio output quantity in n computing cycle, M
i,nbe the integration output quantity in n computing cycle, M
d,nit is the differential output quantity in n computing cycle; By PIDOUT
nbe converted into corresponding SOFA air door amount of bias.
In one embodiment, PLC is specifically determining after corresponding control parameter Z according to interval X and Y, is also comprising: whether judgement controls parameter Z for enabling first; If controlling parameter Z is not to enable first, carry out the PID output PIDOUT that calculates n computing cycle
noperation; If control parameter Z for enabling first, to the integration output quantity M in n-1 computing cycle
i, n-1initialize M
i, n-1=PIDOUT
n-1-M
p,n+ M
d,n, then carry out the PID output PIDOUT that calculates n computing cycle
noperation.
In one embodiment, PLC specifically utilizes formula
Error
n＝a*(SP
n-PV
n)+(1-a)*Error
n-1
Calculated difference Error
n, wherein a is filter factor.
In one embodiment, DCS is also for after receiving the instruction that PLC sends, judge current self whether in low nitrogen burning control model, there is exiting when abnormal low nitrogen burning control model judgement and communicating by letter of PLC in DCS wherein; If current self in low nitrogen burning control model, further effectively whether the parameter in decision instruction, whether parameter rate of change in preset range; If the parameter in instruction effectively and parameter rate of change in preset range, utilize instruction to control corresponding air door; If the invalid parameters in instruction, or parameter rate of change exceeds preset range, the instruction that refusal execution receives.
The present invention determines the instruction of corresponding secondary air register aperture and the instruction of SOFA air door by PLC according to the boiler operating parameter of DCS feedback, and according to nitrogen oxide measured value to SOFA air door instruction revise, thereby the low nitrogen burning of effectively realizing boiler is controlled, realize the economic environmental protection optimization operation of boiler.
Description of the invention provides for example with for the purpose of describing, and is not exhaustively or limit the invention to disclosed form.Many modifications and variations are obvious for the ordinary skill in the art.Selecting and describing embodiment is for better explanation principle of the present invention and practical application, thereby and makes those of ordinary skill in the art can understand the various embodiment with various modifications that the present invention's design is suitable for special-purpose.
Accompanying drawing explanation
In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, to the accompanying drawing of required use in embodiment or description of the Prior Art be briefly described below, apparently, accompanying drawing in the following describes is only some embodiments of the present invention, for those of ordinary skills, do not paying under the prerequisite of creative work, can also obtain according to these accompanying drawings other accompanying drawing.
Fig. 1 is the schematic diagram that the present invention is based on an embodiment of low nitrogen burning control method of PLC.
Fig. 2 is the schematic diagram that the present invention determines an embodiment of SOFA air door amount of bias.
Fig. 3 is the schematic diagram that the present invention determines another embodiment of SOFA air door amount of bias.
Fig. 4 is the schematic diagram that the present invention is based on an embodiment of low nitrogen burning control system of PLC.
Fig. 5 is the schematic diagram of an embodiment of low nitrogen burning control system configuration of the present invention.
Fig. 6 is the schematic diagram that low nitrogen burning control system of the present invention configures another embodiment.
The specific embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is clearly and completely described, obviously, described embodiment is only the present invention's part embodiment, rather than whole embodiment.To the description only actually of at least one exemplary embodiment, be illustrative below, never as any restriction to the present invention and application or use.Embodiment based in the present invention, those of ordinary skills, not making the every other embodiment obtaining under creative work prerequisite, belong to the scope of protection of the invention.
Unless illustrate in addition, otherwise the parts of setting forth in these embodiments and positioned opposite, numeral expression formula and the numerical value of step not limited the scope of the invention.
, it should be understood that for convenience of description, the size of the various piece shown in accompanying drawing is not to draw according to actual proportionate relationship meanwhile.
For the known technology of person of ordinary skill in the relevant, method and apparatus, may not discuss in detail, but in suitable situation, described technology, method and apparatus should be regarded as authorizing a part for description.
In all examples with discussing shown here, it is exemplary that any occurrence should be construed as merely, rather than as restriction.Therefore, other example of exemplary embodiment can have different values.
It should be noted that: in similar label and letter accompanying drawing below, represent similar terms, therefore, once be defined in an a certain Xiang Yi accompanying drawing, in accompanying drawing subsequently, do not need it to be further discussed.
Fig. 1 is the schematic diagram that the present invention is based on an embodiment of low nitrogen burning control method of PLC.As shown in Figure 1, the method step of the present embodiment is as follows:
Step 101, PLC, according to the boiler operating parameter of DCS feedback, controls in model and obtains corresponding secondary air register aperture instruction and the instruction of SOFA throttle opening at the low nitrogen burning setting in advance, and corresponding discharged nitrous oxides desired value.
For example, boiler operating parameter can comprise load, ature of coal, primary air flow, total blast volume (oxygen amount), coal pulverizer combination, boiler efficiency etc.DCS can predetermined time interval feedback boiler operating parameter, also can feed back in real time.
Preferably, the low nitrogen burning setting in advance is controlled model and can be obtained by a large amount of meticulous hot experiments.For example, can consider discharged nitrous oxides and boiler efficiency, for power plant conventional several atures of coal and coal pulverizer combination, under a plurality of typical loads, carry out hot experiment, obtain the optimum air distribution general layout of discharged nitrous oxides desired value and Secondary Air and SOFA wind, the resulting data of take are by experiment set up typical condition storehouse as sample point.Take typical condition as basis, and curve is controlled in matching, determines Secondary Air and the instruction of SOFA wind aperture corresponding under different operating modes, sets up low nitrogen burning control model with this.Thus, PLC can control model from the low nitrogen burning setting in advance, and obtains the secondary air register aperture instruction relevant to DCS feedback parameter and the instruction of SOFA throttle opening.
Step 102, PLC sends to DCS by the instruction of secondary air register aperture and the instruction of SOFA throttle opening, so that DCS utilizes the instruction of secondary air register aperture and the instruction of SOFA throttle opening respectively secondary air register and SOFA air door to be controlled.
Step 103, PLC, according to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determines SOFA air door amount of bias.
Step 104, PLC is by SOFA air door amount of bias and current SOFA throttle opening instruction stack of obtaining from low nitrogen burning control model, to obtain calibrated SOFA throttle opening instruction.
Step 105, PLC sends to DCS by calibrated SOFA throttle opening instruction, so that DCS utilizes calibrated SOFA throttle opening instruction to control SOFA air door.
Preferably, PLC can utilize Modbus agreement and DCS to carry out opposing traffic, and DCS can control main combustion zone secondary air register and SOFA air door by hardwire.
The low nitrogen burning control method based on PLC providing based on the above embodiment of the present invention, by PLC, according to the boiler operating parameter of DCS feedback, determine the instruction of corresponding secondary air register aperture and the instruction of SOFA air door, and according to nitrogen oxide measured value to SOFA air door instruction revise, thereby the low nitrogen burning of effectively realizing boiler is controlled, realize the economic environmental protection optimization operation of boiler.
In one embodiment, PLC is by boiler operating parameter and the nitrogen oxide measured value of DCS feedback, and corresponding secondary air register aperture instruction, the instruction of SOFA throttle opening and SOFA air door amount of bias store in low nitrogen burning control model.
Thereby, during using control program actual motion, can add typical condition storehouse to as the process data historical sample of typical condition, further enrich typical condition storehouse, and further revise Optimizing Combustion and control model.
For example, the low nitrogen burning control system of 600MW generating set of take is example, at Optimizing Combustion, control in model, between 500MW-600MW loading zone, only include 500 megawatts and two typical conditions of 600 megawatts, and for the operating mode between 500 megawatts and 600 megawatts, for example, for the operating mode of 550 megawatts, need to take these two typical conditions of 500 megawatts and 600 megawatts as basis, by matching, control curve and determined.Owing to existing a certain distance between matched curve and actual condition, therefore can not effectively realize the low nitrogen burning of boiler and control.If there are representing the canonical process data of 550 megawatt operating modes in actual motion, this process data historical sample can be added in typical condition storehouse.Because the precision of actual operating data is better than the result that matched curve obtains, therefore by enriching typical condition storehouse, can further revise Optimizing Combustion and control model, thereby the low nitrogen burning of effectively realizing boiler is controlled.
It should be noted that: the data such as load, ature of coal, coal pulverizer combination, oxygen amount, primary air flow, boiler efficiency are passed through Modbus mode from DCS system acquisition, for the unit that there is no ature of coal on-line monitoring, the coal industry analysis of coal data source power plant.For not characterizing the unit of boiler efficiency in DCS, can characterize the parameter substitution of boiler economy by other.
When main combustion zone, Secondary Air air distribution is constant, and when SOFA wind air distribution increases, NOx discharge can decline, and vice versa.Therefore low nitrogen burning control system is with regulating the method for SOFA wind to regulate NOx value of feedback and desired value difference.Because SOFA air door is adjusted, it is a combustion process that end reaction changes to NOx discharge, belongs to large delayed time system, if according to conventional PID (Proportion, Integration, Differentiation, ratio, integration and differentiation) regulate, be difficult to the stable of the system that reaches.In order to obtain good control effect, make PID control output more steady, reduce the operating frequency of SOFA wind air door, select the PID of variable element to control to regulate SOFA air door here.Therefore above-mentioned PLC is according to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determines that the step of SOFA air door amount of bias can be as shown in Figure 2:
Step 201, PLC, when arriving n computing cycle, calculates current discharged nitrous oxides desired value SP
nwith current nitrogen oxide measured value PV
ndifference Error
n.
Preferably, Error
n=a* (SP
n-PV
nthe * of)+(1-a) Error
n-1, wherein a is filter factor.
Step 202, determines Error
naffiliated interval X and Error
n-1affiliated interval Y.
Step 203, determines corresponding control parameter Z according to interval X and Y, wherein controls parameter Z and comprises proportionality coefficient C
p, integral coefficient C
i, differential coefficient C
d.
Step 204, the PID that calculates n computing cycle exports PIDOUT
n, PIDOUT wherein
n=M
p,n+ M
i,n+ M
d,n=C
p* Error
n+ (M
i, n-1+ C
i* Error
n-1)+C
d* (PV
n-1-PV
n), M
p,nbe the PID ratio output quantity in n computing cycle, M
i,nbe the integration output quantity in n computing cycle, M
d,nit is the differential output quantity in n computing cycle.
Step 205, by PIDOUT
nbe converted into corresponding SOFA air door amount of bias.
The PID of variable element controls that to take the desired value of NOx concentration of emission and the difference of value of feedback be input, passing ratio and integral and calculating and data transform the amount of bias that obtains SOFA air door, and this amount of bias is finally added to and is controlled in the SOFA throttle opening instruction of model calculating output by low nitrogen burning.Can PID be controlled and carry out on-line tuning according to the size of the difference of the desired value of NOx concentration of emission and value of feedback and rate of change, make PID control output more steady, can reduce the operating frequency of SOFA air door, extend the service life of air door.
Fig. 3 is the schematic diagram that the present invention determines another embodiment of SOFA air door amount of bias.Wherein:
Step 301, PLC, when arriving n computing cycle, calculates current discharged nitrous oxides desired value SP
nwith current nitrogen oxide measured value PV
ndifference Error
n.
Preferably, Error
n=a* (SP
n-PV
nthe * of)+(1-a) Error
n-1, wherein a is filter factor.
Step 302, determines Error
naffiliated interval X and Error
n-1affiliated interval Y.
Step 303, determines corresponding control parameter Z according to interval X and Y, wherein controls parameter Z and comprises proportionality coefficient C
p, integral coefficient C
i, differential coefficient C
d.
Step 304, whether judgement controls parameter Z for enabling first.If control parameter Z for enabling first, perform step 305; If controlling parameter Z is not to enable first, perform step 306.
Step 305, to the integration output quantity M in n-1 computing cycle
i, n-1initialize M
i, n-1=PIDOUT
n-1-M
p,n+ M
d,n.
Step 306, the PID that calculates n computing cycle exports PIDOUT
n, PIDOUT wherein
n=M
p,n+ M
i,n+ M
d,n=C
p* Error
n+ (M
i, n-1+ C
i* Error
n-1)+C
d* (PV
n-1-PV
n), M
p,nbe the PID ratio output quantity in n computing cycle, M
i,nbe the integration output quantity in n computing cycle, M
d,nit is the differential output quantity in n computing cycle.
Step 307, by PIDOUT
nbe converted into corresponding SOFA air door amount of bias.
In the present embodiment, when controlling parameter Z when enabling first, by integration output quantity is initialized, can guarantee that control program is when switching, PID output does not have disturbance, so that the stability of assurance system.
Preferably, in order to improve security of system, can further increase communication security protection logic.For example, DCS and PLC can judge that by monitoring heartbeat signal whether the communication between DCS and PLC is normal respectively.
In one embodiment, DCS after receiving the instruction that PLC sends, judge current self whether in low nitrogen burning control model, there is exiting when abnormal low nitrogen burning control model judgement and communicating by letter of PLC in DCS wherein.If current self in low nitrogen burning control model, whether the parameter in the further decision instruction of DCS effectively, whether parameter rate of change in preset range.If the parameter in instruction effectively and parameter rate of change in preset range, DCS utilizes instruction to control corresponding air door; If the invalid parameters in instruction, or parameter rate of change exceeds preset range, the instruction that execution of DCS refusal receives.If there is continuously the invalid parameters in instruction, or parameter rate of change exceeds the situation of preset range, also can exit low nitrogen burning control model.
In another embodiment, PLC also can judge whether to be adopted according to validity and the rate of change of the data of DCS feedback.
Fig. 4 is the schematic diagram that the present invention is based on an embodiment of low nitrogen burning control system of PLC.As shown in Figure 4, the low nitrogen burning control system based on PLC can comprise PLC401 and DCS402.Wherein:
DCS402, for feeding back boiler operating parameter and nitrogen oxide measured value to PLC401, when receiving secondary air register aperture instruction that PLC401 sends and the instruction of SOFA throttle opening, utilize the instruction of secondary air register aperture and the instruction of SOFA throttle opening respectively secondary air register and SOFA air door to be controlled; When receive that PLC401 sends calibrated SOFA throttle opening instruction time, utilize calibrated SOFA throttle opening instruction to control SOFA air door.
PLC401, for according to the boiler operating parameter of DCS402 feedback, controls in model and obtains corresponding secondary air register aperture instruction and the instruction of SOFA throttle opening at the low nitrogen burning setting in advance, and corresponding discharged nitrous oxides desired value; The instruction of secondary air register aperture and the instruction of SOFA throttle opening are sent to DCS402; According to the nitrogen oxide measured value of DCS402 feedback and current discharged nitrous oxides desired value, determine SOFA air door amount of bias; By SOFA air door amount of bias and current SOFA throttle opening instruction stack of obtaining, to obtain calibrated SOFA throttle opening instruction, calibrated SOFA throttle opening instruction is sent to DCS402 from low nitrogen burning control model.
Wherein, the low nitrogen burning setting in advance is controlled model and can be obtained by a large amount of meticulous hot experiments.For example, can consider discharged nitrous oxides and boiler efficiency, for power plant conventional several atures of coal and coal pulverizer combination, under a plurality of typical loads, carry out hot experiment, obtain the optimum air distribution general layout of discharged nitrous oxides desired value and Secondary Air and SOFA wind, the resulting data of take are by experiment set up typical condition storehouse as sample point.Thus, PLC can control model from the low nitrogen burning setting in advance, and obtains the secondary air register aperture instruction relevant to DCS feedback parameter and the instruction of SOFA throttle opening.
The low nitrogen burning control system based on PLC providing based on the above embodiment of the present invention, by PLC, according to the boiler operating parameter of DCS feedback, determine the instruction of corresponding secondary air register aperture and the instruction of SOFA air door, and according to nitrogen oxide measured value to SOFA air door instruction revise, thereby the low nitrogen burning of effectively realizing boiler is controlled, realize the economic environmental protection optimization operation of boiler.
Preferably, PLC401 can utilize Modbus agreement and DCS402 to carry out opposing traffic, and DCS402 can control main combustion zone secondary air register and SOFA air door by hardwire.
In one embodiment, PLC401 is also for storing the boiler operating parameter of DCS402 feedback and corresponding secondary air register aperture instruction, the instruction of SOFA throttle opening and SOFA air door amount of bias into low nitrogen burning control model.
Thereby, can add typical condition storehouse to as the process data historical sample of typical condition when using control program actual motion, further enrich typical condition storehouse, and further revise Optimizing Combustion and control model.
In one embodiment, PLC401 specifically, when arriving n computing cycle, calculates current discharged nitrous oxides desired value SP
nwith current nitrogen oxide measured value PV
ndifference Error
n; Determine Error
naffiliated interval X and Error
n-1affiliated interval Y; According to interval X and Y, determine corresponding control parameter Z, wherein control parameter Z and comprise proportionality coefficient C
p, integral coefficient C
i, differential coefficient C
d; Calculate the PID output PIDOUT of n computing cycle
n, PIDOUT wherein
n=M
p,n+ M
i,n+ M
d,n=C
p* Error
n+ (M
i, n-1+ C
i* Error
n-1)+C
d* (PV
n-1-PV
n), M
p,nbe the PID ratio output quantity in n computing cycle, M
i,nbe the integration output quantity in n computing cycle, M
d,nit is the differential output quantity in n computing cycle; By PIDOUT
nbe converted into corresponding SOFA air door amount of bias.
Preferably, PLC401 specifically utilizes formula
Error
n＝a*(SP
n-PV
n)+(1-a)*Error
n-1
Calculated difference Error
n, wherein a is filter factor.
Preferably, PLC401 is specifically determining after corresponding control parameter Z according to interval X and Y, is also comprising: whether judgement controls parameter Z for enabling first; If controlling parameter Z is not to enable first, carry out the PID output PIDOUT that calculates n computing cycle
noperation; If control parameter Z for enabling first, to the integration output quantity M in n-1 computing cycle
i, n-1initialize M
i, n-1=PIDOUT
n-1-M
p,n+ M
d,n, then carry out the PID output PIDOUT that calculates n computing cycle
noperation.
Wherein, when controlling parameter Z when enabling first, by integration output quantity is initialized, can guarantee that control program is when switching, PID output does not have disturbance, so that the stability of assurance system.
In addition,, in order to improve security of system, can further increase communication security protection logic.For example, DCS402 and PLC401 can judge that by monitoring heartbeat signal whether the communication between DCS402 and PLC401 is normal respectively.
In one embodiment, DCS402 is also for after receiving the instruction that PLC401 sends, judge current self whether in low nitrogen burning control model, there is exiting when abnormal low nitrogen burning control model judgement and communicating by letter of PLC in DCS402 wherein.If current self in low nitrogen burning control model, further effectively whether the parameter in decision instruction, whether parameter rate of change in preset range; If the parameter in instruction effectively and parameter rate of change in preset range, utilize instruction to control corresponding air door; If the invalid parameters in instruction, or parameter rate of change exceeds preset range, the instruction that refusal execution receives.If there is continuously the invalid parameters in instruction, or parameter rate of change exceeds the situation of preset range, also can exit low nitrogen burning control model.
In another embodiment, PLC401 also can judge whether to be adopted according to validity and the rate of change of the data of DCS402 feedback.
Fig. 5 is the schematic diagram of an embodiment of low nitrogen burning control system configuration of the present invention.As shown in Figure 5, PLC and DCS communicate by Modbus agreement.DCS is according to predetermined time interval the or in real time boiler operating parameters such as load, primary air pressure and nitrogen oxide measured value are fed back to PLC.PLC is according to DCS feedack, the low nitrogen burning that utilization sets in advance is controlled model and is obtained the instruction of corresponding secondary air register aperture and the instruction of SOFA throttle opening, wherein the instruction of SOFA throttle opening can be controlled directly acquisition of model by low nitrogen burning, can be also the SOFA throttle opening instruction after the determined SOFA air door of the difference amount of bias based between nitrogen oxide measured value and nitrogen oxide desired value is proofreaied and correct.PLC sends to DCS by the instruction of secondary air register aperture and the instruction of SOFA throttle opening, so that DCS utilizes the instruction of secondary air register aperture and the instruction of SOFA throttle opening to control corresponding secondary air register and SOFA air door.Secondary air register and SOFA air door also can be by throttle opening feedback of status to DCS, so that DCS carries out airdoor control.
Wherein, the control algolithm of PLC can adopt the structured text programming language programming that meets IEC61131-3 standard, and it is similar to computer advanced programming language, can realize complicated control algorithm, thereby is not subject to the impact of DCS.
Fig. 6 is the schematic diagram that low nitrogen burning control system of the present invention configures another embodiment.Compare with embodiment illustrated in fig. 5, in the embodiment shown in fig. 6, also industrial computer can be further set.Wherein industrial computer communicates by ICP/IP protocol and PLC.PLC can offer industrial computer by system-computed result.On industrial computer, can move the man-machine interface that a set of configuration software is usingd as low nitrogen burning control system, user can show and the inquiry of historical data be analyzed by man-machine interface completion system parameter configuration, online data.The systematic parameter that industrial computer can arrange user sends to PLC, to system is controlled.
By implementing the present invention, can be according to factors such as load, ature of coal, oxygen amount, air quantity, coal pulverizer combinations, choose the air distribution scheme under corresponding fired state, and can revise in real time according to nitrogen oxide value of feedback the air distribution scheme of SOFA wind, thereby the low nitrogen burning of effectively realizing boiler is controlled, realize the economic environmental protection optimization operation of boiler simultaneously.
One of ordinary skill in the art will appreciate that all or part of step that realizes above-described embodiment can complete by hardware, also can come the hardware that instruction is relevant to complete by program, described program can be stored in a kind of computer-readable recording medium, the above-mentioned storage medium of mentioning can be read-only storage, disk or CD etc.
Claims (12)
1. the low nitrogen burning control method based on PLC, is characterized in that, comprising:
Programmable Logic Controller PLC is according to the boiler operating parameter of dcs DCS feedback, at the low nitrogen burning setting in advance, control in model and obtain corresponding secondary air register aperture instruction and the instruction of separate type after-flame wind SOFA throttle opening, and corresponding discharged nitrous oxides desired value;
PLC sends to DCS by the instruction of secondary air register aperture and the instruction of SOFA throttle opening, so that DCS utilizes the instruction of secondary air register aperture and the instruction of SOFA throttle opening respectively secondary air register and SOFA air door to be controlled;
PLC, according to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determines SOFA air door amount of bias;
PLC is by SOFA air door amount of bias and current SOFA throttle opening instruction stack of obtaining from low nitrogen burning control model, to obtain calibrated SOFA throttle opening instruction;
PLC sends to DCS by calibrated SOFA throttle opening instruction, so that DCS utilizes calibrated SOFA throttle opening instruction to control SOFA air door.
2. method according to claim 1, is characterized in that,
PLC is boiler operating parameter and the nitrogen oxide measured value of DCS feedback, and corresponding secondary air register aperture instruction, the instruction of SOFA throttle opening and SOFA air door amount of bias store low nitrogen burning into and control in model, to revise Optimizing Combustion, controls model.
3. method according to claim 1, is characterized in that,
PLC, according to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determines that the step of SOFA air door amount of bias comprises:
PLC, when arriving n computing cycle, calculates current discharged nitrous oxides desired value SP
nwith current nitrogen oxide measured value PV
ndifference Error
n;
Determine Error
naffiliated interval X and Error
n-1affiliated interval Y;
According to interval X and Y, determine corresponding control parameter Z, wherein control parameter Z and comprise proportionality coefficient C
p, integral coefficient C
i, differential coefficient C
d;
Calculate the PID output PIDOUT of n computing cycle
n, PIDOUT wherein
n=M
p,n+ M
i,n+ M
d,n=C
p* Error
n+ (M
i, n-1+ C
i* Error
n-1)+C
d* (PV
n-1-PV
n), M
p,nbe the PID ratio output quantity in n computing cycle, M
i,nbe the integration output quantity in n computing cycle, M
d,nit is the differential output quantity in n computing cycle;
By PIDOUT
nbe converted into corresponding SOFA air door amount of bias.
4. method according to claim 3, is characterized in that,
After determining the step of corresponding control parameter Z according to interval X and Y, also comprise:
Whether judgement controls parameter Z for enabling first;
If controlling parameter Z is not to enable first, carry out the PID output PIDOUT that calculates n computing cycle
nstep;
If control parameter Z for enabling first, to the integration output quantity M in n-1 computing cycle
i, n-1initialize M
i, n-1=PIDOUT
n-1-M
p,n+ M
d,n, then carry out the PID output PIDOUT that calculates n computing cycle
nstep.
5. method according to claim 3, is characterized in that,
Error
n＝a*(SP
n-PV
n)+(1-a)*Error
n-1；
Wherein a is filter factor.
6. according to the method described in any one in claim 1-5, it is characterized in that,
DCS after receiving the instruction that PLC sends, judge current self whether in low nitrogen burning control model, there is exiting when abnormal low nitrogen burning control model judgement and communicating by letter of PLC in DCS wherein;
If current self in low nitrogen burning control model, whether the parameter in the further decision instruction of DCS effectively, whether parameter rate of change in preset range;
If the parameter in instruction effectively and parameter rate of change in preset range, DCS utilizes instruction to control corresponding air door;
If the invalid parameters in instruction, or parameter rate of change exceeds preset range, the instruction that execution of DCS refusal receives.
7. the low nitrogen burning control system based on PLC, is characterized in that, comprises Programmable Logic Controller PLC and dcs DCS, wherein:
DCS, for feeding back boiler operating parameter and nitrogen oxide measured value to PLC, when receiving secondary air register aperture instruction that PLC sends and the instruction of separate type after-flame wind SOFA throttle opening, utilize the instruction of secondary air register aperture and the instruction of SOFA throttle opening respectively secondary air register and SOFA air door to be controlled; When receive that PLC sends calibrated SOFA throttle opening instruction time, utilize calibrated SOFA throttle opening instruction to control SOFA air door;
PLC, for according to the boiler operating parameter of DCS feedback, controls in model and obtains corresponding secondary air register aperture instruction and the instruction of SOFA throttle opening at the low nitrogen burning setting in advance, and corresponding discharged nitrous oxides desired value; The instruction of secondary air register aperture and the instruction of SOFA throttle opening are sent to DCS; According to the nitrogen oxide measured value of DCS feedback and current discharged nitrous oxides desired value, determine SOFA air door amount of bias; By SOFA air door amount of bias and current SOFA throttle opening instruction stack of obtaining, to obtain calibrated SOFA throttle opening instruction, calibrated SOFA throttle opening instruction is sent to DCS from low nitrogen burning control model.
8. system according to claim 7, is characterized in that,
PLC is boiler operating parameter and the nitrogen oxide measured value for DCS is fed back also, and corresponding secondary air register aperture instruction, the instruction of SOFA throttle opening and SOFA air door amount of bias store low nitrogen burning into and control in model, to revise Optimizing Combustion, control model.
9. system according to claim 7, is characterized in that,
PLC specifically, when arriving n computing cycle, calculates current discharged nitrous oxides desired value SP
nwith current nitrogen oxide measured value PV
ndifference Error
n; Determine Error
naffiliated interval X and Error
n-1affiliated interval Y; According to interval X and Y, determine corresponding control parameter Z, wherein control parameter Z and comprise proportionality coefficient C
p, integral coefficient C
i, differential coefficient C
d; Calculate the PID output PIDOUT of n computing cycle
n, PIDOUT wherein
n=M
p,n+ M
i,n+ M
d,n=C
p* Error
n+ (M
i, n-1+ C
i* Error
n-1)+C
d* (PV
n-1-PV
n), M
p,nbe the PID ratio output quantity in n computing cycle, M
i,nbe the integration output quantity in n computing cycle, M
d,nit is the differential output quantity in n computing cycle; By PIDOUT
nbe converted into corresponding SOFA air door amount of bias.
10. system according to claim 9, is characterized in that,
PLC is specifically determining after corresponding control parameter Z according to interval X and Y, is also comprising: whether judgement controls parameter Z for enabling first; If controlling parameter Z is not to enable first, carry out the PID output PIDOUT that calculates n computing cycle
noperation; If control parameter Z for enabling first, to the integration output quantity M in n-1 computing cycle
i, n-1initialize M
i, n-1=PIDOUT
n-1-M
p,n+ M
d,n, then carry out the PID output PIDOUT that calculates n computing cycle
noperation.
11. systems according to claim 9, is characterized in that,
PLC specifically utilizes formula
Error
n＝a*(SP
n-PV
n)+(1-a)*Error
n-1
Calculated difference Error
n, wherein a is filter factor.
12. systems according to claim 7, is characterized in that,
DCS is also for after receiving the instruction that PLC sends, judge current self whether in low nitrogen burning control model, there is exiting when abnormal low nitrogen burning control model judgement and communicating by letter of PLC in DCS wherein; If current self in low nitrogen burning control model, further effectively whether the parameter in decision instruction, whether parameter rate of change in preset range; If the parameter in instruction effectively and parameter rate of change in preset range, utilize instruction to control corresponding air door; If the invalid parameters in instruction, or parameter rate of change exceeds preset range, the instruction that refusal execution receives.
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