CN113390099B - Coordination control method under coal-fired cogeneration unit self-adaptive BTU - Google Patents
Coordination control method under coal-fired cogeneration unit self-adaptive BTU Download PDFInfo
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
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- F23N1/00—Regulating fuel supply
- F23N1/08—Regulating fuel supply conjointly with another medium, e.g. boiler water
- F23N1/10—Regulating fuel supply conjointly with another medium, e.g. boiler water and with air supply or draught
- F23N1/102—Regulating fuel supply conjointly with another medium, e.g. boiler water and with air supply or draught using electronic means
Abstract
The invention provides a coordination control method under a coal-fired cogeneration unit self-adaptive BTU. The method comprises the following steps: acquiring standard coal amount under different generating capacities; the coal quality correction coefficient BTU is detected and optimized at regular time through the logic configuration of a distributed control system; the differential feedforward of main steam pressure deviation, the proportional feedforward of unit load instructions and the proportional coefficient of the boiler main control are corrected through the coal quality correction coefficient BTU, the fuel main control is corrected, and the adjustment output of a secondary air door of the boiler is corrected. The stability of the main controlled parameters of the unit is greatly improved, the coordination control and automatic power generation control indexes of the unit can be ensured, the change of wind and coal parameters is smoother during the load change, the adjustment variation of the main parameters of the unit is further reduced, and the economy of the unit is higher. The influence of internal and external disturbance on coordination control and automatic power generation control and regulation is reduced, and the safe and economic operation level of the unit is improved.
Description
Technical Field
The invention relates to the technical field of production safety and thermal control of a coal-fired cogeneration unit, in particular to a coordination control method under a self-adaptive BTU (thermal power unit) of the coal-fired cogeneration unit.
Background
With the wide application of material technology and clean energy (including hydraulic energy, wind energy, solar energy and the like), the remote transmission of ultra/extra-high voltage alternating current and direct current and the construction of large power supply base stations, the frequency modulation and peak regulation of power grids are required more frequently, and the quality requirements of the power grids on electric energy are higher and higher. At the present stage, the power grid structure of China still mainly adopts thermal power generation, and AGC economic dispatching is realized to save energy. The existing AGC is mainly carried out on the basis of coordination, and in a coordination control system, two problems cannot be well solved, namely, how to accurately and quickly judge the change of the current coal quality, and what measures are taken to automatically adjust the combustion and coordination control mode of a boiler after judging the change of the coal quality. Because the components in the coal change along with the change of the coal quality, the heat quantity released by the coal with the same quality is different, and various parameters of a boiler and an auxiliary machine of a coal-fired unit are influenced to a great extent, and the coordinated control and the AGC are influenced. When the load changes, the traditional load instruction feedforward and PID feedback control strategies cannot meet the requirements of the power grid operation criteria, and the dispatching of the power grid to the unit is seriously influenced.
For coal composition analysis, the traditional analysis method is completed by three links of sampling, sample preparation and assay. The coal is sampled at regular time, and important indexes such as ash content, moisture content, heat value and the like of the coal are measured and calculated by an analyzer of a burning method. The method is long in time consumption, running personnel can perform real-time online adjustment according to the change of coal quality after obtaining the test report in hours, and the promotion effect on adjustment and optimized operation of real-time combustion is very limited. Some on-line monitoring systems have been developed in order to make up for the shortcomings of the conventional methods, but the above monitoring systems have problems of complicated structure, high cost and inconvenient maintenance. Specific components in coal quality, such as ash content and moisture, are only detected from the internal components of coal quality elements, but the comprehensive judgment on the coal quality cannot meet the requirement, and the coal quality online monitoring device is difficult to be applied in a large range due to the factors in various aspects. In conclusion, it is necessary and meaningful to explore a novel adaptive real-time coal quality correction method.
In the aspect of control technology, the traditional load instruction feedforward and PID feedback control strategies comprise loops such as boiler main control, steam turbine main control and fuel main control. The boiler master control adjusts boiler input variables such as total fuel quantity, total feed water flow, total air quantity and the like of the boiler according to the requirement of the unit load instruction so as to meet the requirement of a steam engine side on the boiler load. The main control of the steam turbine is divided into two working modes of pressure control and load control, and the two working modes respectively receive the pressure before the turbine and the load of the unit calculated by the coordination system as target values so as to control the opening degree of the regulating valve. The fuel main control generates a total coal supply quantity instruction according to the comparison of the fuel instruction and the actual total fuel quantity, and a total fuel quantity signal is generated by adding the total coal supply quantity and the fuel flow (converting an oil-coal conversion coefficient according to a low-order heating value of the designed coal type and a heating value of the fuel). Along with the change of the unit working condition and the coal quality, the control quality of the operation unit is worse and worse, and the manual intervention of an operator is often required. Therefore, the coordination of the unit and the AGC control system need to be adjusted by the variable parameter adaptive coal quality correction coefficient.
Typical coal quality correction methods are as follows: a method for correcting the coal quality of the working coal ratio. The method is shown in figure 1, and a coal quality correction coefficient is constructed according to actual operation parameters of a unit. The principle of the method is that whether the unit is in a stable working condition or not is judged, and after the judgment is passed, the working capacity of the unit is represented by the ratio of the actual total coal supply quantity of the boiler to the actual power output of the unit, namely the output capacity of the unit under the condition of the current coal quality and the coal quantity. The coefficient obtained by dividing the value by the output under the standard coal is the coal quality correction coefficient. When the coal quality is not changed, the coefficient is 1, when the coal quality is changed, the numerical value deviates, the amplitude limit of 0.8-1.2 is carried out on the numerical value, and the amplitude limit range can be changed according to the actual coal type change condition of the unit. However, the method adopts two parameters of the power generation amount and the coal feeding amount, so that the period from the reaction of the change of the coal amount to the change of the power generation amount is very long, and the judgment condition is harsh, so that the space of engineering application is very limited.
In the aspect of control technology, the coordination control mode is that the load control is carried out at the side of a steam turbine, and the system is a single-loop system and is simpler; the pressure control at the boiler side involves many factors, and in order to ensure that parameters such as pressure, temperature and the like are appropriate, the main control output of the boiler is changed in advance by introducing pressure feedforward, so that the control speed is accelerated. The conventional boiler main control logic is shown in fig. 2.
The PV input quantity of the PID link is a main steam pressure actual value, the SP input quantity is a main steam pressure set value, and the FF input quantity is a main control feed-forward input end of the boiler. The feedforward mainly comprises two parts, namely unit load instruction feedforward and main steam pressure differential feedforward: the input quantity of f (x) is a unit load instruction, a fixed boiler main control instruction feedforward is generated through a function generator f (x) according to the unit load instruction, and if the coal is a design coal type, the function generator f (x) can be directly set according to a fixed function. Differential feedforward is generated according to the deviation of the set value and the actual value of the main steam pressure, and the principle is that the deviation value subtracts the value of the deviation value after first-order inertia lag, which is equivalent to differential action. And the PID final output quantity is a boiler main control instruction.
The control scheme has good control effects on pressure, temperature and the like when the working condition of the unit is stable and the coal quality is stable, but when the coal quality changes, particularly changes greatly, main parameters such as main steam pressure and the like fluctuate greatly, so that the response speed and the control precision of the load are influenced, and the quality of coordinated control of the unit is influenced.
Disclosure of Invention
According to the problems of long time consumption, complex structure, high cost and complex control logic in the conventional coal quality analysis method, the coordination control method under the self-adaptive BTU of the coal-fired cogeneration unit is provided. According to the invention, the coal quality is changed in the required load change rate and load change range through the self-adaptive coal quality correction coefficient BTU, so that the coordination control and automatic power generation control indexes of the unit are ensured, and meanwhile, the change of main parameters such as wind and coal in the load change is smoother, so that the adjustment deviation of the main parameters of the unit is further reduced, and the stable operation of combustion adjustment under the coal quality change disturbance is met. The technical means adopted by the invention are as follows:
a coordination control method under a coal-fired cogeneration unit self-adaptive BTU comprises the following steps:
step 1, obtaining standard coal amount under different power generation quantities, and taking the standard coal amount as a reference coal amount;
step 2, the obtained standard coal quantity is subjected to timing detection and optimized output of a coal quality correction coefficient BTU under the stable combustion working condition of the unit through the logic configuration of a distributed control system;
and 3, correcting differential feedforward of main steam pressure deviation, proportional feedforward of unit load instructions and proportional coefficients of a boiler main control through the coal quality correction coefficient BTU, further correcting a fuel main control, and correcting the adjustment output of a secondary air door of the boiler through the coal quality correction coefficient.
Further, the standard coal quantity is obtained through a combustion test of the actual dynamic standard coal or the standard coal close to the standard coal of the thermal power generating unit.
Further, the coal quality correction coefficient is optimized in real time through the following method: and multiplying the total coal quantity detected by the primary element by the coal quality correction coefficient BTU to obtain the standard coal quantity corresponding to the current coal type of the unit, and optimizing the coal quality correction coefficient in real time by continuously correcting the standard coal quantity corresponding to the current coal type and the reference coal quantity.
Further, the BTU coal quality correction coefficient is corrected according to the coal quantity deviation value, when the coal quantity deviation is larger than 0.5%, the BTU coal quality correction coefficient is corrected in the negative direction, and when the coal quantity deviation is smaller than-0.5%, the BTU coal quality correction coefficient is corrected in the positive direction, wherein the specific correction method is determined by a BTU correction function generator. And determining the proportion and integral coefficient of PID (proportion integration differentiation) adjusting parameters of the coal quality correction coefficient according to the actual working condition. Further, the upper and lower limits of the PID adjustment are 1.2 and 0.8, respectively.
Further, in the logic configuration of the distributed control system, the determining of the influencing factors in the calculation process of the coal quality correction coefficient includes: the method comprises the steps of actual power of a unit, load instructions of the unit, pressure deviation, main water supply flow, coal feeding amount of a single coal mill and fuel flow in the operation process of an oil gun.
Further, when the boiler is in a stable combustion condition, the BTU is normally calculated, and when the boiler is unstable in combustion, the BTU is stopped, and the preset unstable boiler combustion condition in step 2 includes the following:
(a) Starting and stopping in the grinding process
(b) The load instruction of the unit changes within 600 seconds;
(c) The deviation of the main steam pressure is more than 0.3Mpa;
(d) The power deviation is more than 15MW;
(e) Boiler MFT signal triggering;
(f) When the signal quality of the main water supply flow, the coal feeding amount of a single coal mill and the fuel flow in the operation process of an oil gun is in fault;
(g) When resection is coordinated.
Further, the step of correcting the differential feedforward of the main steam pressure deviation, the proportional feedforward of the unit load instruction and the proportional coefficient of the boiler main control through the coal quality correction coefficient BTU specifically includes:
the coal quality correction coefficient BTU corrects differential feedforward of main steam pressure deviation through a function generator f1 (x), and the correction coefficient is k 1 F1 (x) is a proportional element, k 1 The value change trend is opposite to the BTU change trend, the feedforward quantity is increased when the coal quality is poor, and the differential feedforward of the main steam pressure deviation refers to the differential feedforward formed by comparing the deviation between the main steam pressure set value and the actual value of the boiler with the output value of the deviation value after passing through an inertial lag link and finally outputting the control quantity.
Correcting the proportion feedforward of the unit load instruction through a function generator f2 (x) according to a coal quality correction coefficient BTU, wherein the correction coefficient is k 2 F2 (x) is a proportional element, k 2 The value change trend is opposite to the BTU change trend, the feedforward quantity is increased when the coal quality is poor, the quick response of the main steam pressure is ensured, and the proportion feedforward of the unit load instruction is that a fixed boiler main control instruction feedforward is generated by the unit load instruction through a function.
And correcting a proportional coefficient K of the boiler master control through a function generator f3 (x) according to the coal quality correction coefficient BTU, wherein the K value change trend is opposite to the BTU change trend, the proportional action is increased when the coal quality is poor, and the pressure stability is realized by changing more coal quantity.
And adding the differential feedforward of the corrected main steam pressure deviation and the corrected unit load instruction proportional feedforward to be used as the feedforward of the new boiler main control, and simultaneously using the corrected boiler main control proportional coefficient K together as the input quantity of a follow-up boiler main control PID link to realize the output control of the boiler main control.
The invention has the following advantages:
1. the invention can greatly improve the stability of main controlled parameters of the unit relative to the conventional control in the required load change rate and load change range after the coal quality changes, ensure the coordination control and automatic power generation control indexes of the unit, simultaneously ensure smoother change of the main parameters such as wind, coal and the like in the load change, further reduce the adjustment deviation of the main parameters of the unit, ensure higher economy of the unit, reduce the influence of internal and external disturbance on the coordination control and automatic power generation control adjustment, ensure higher operation stability of the unit, improve the safe and economic operation level of the unit, and effectively solve the problem of poor automatic control quality of the unit caused by larger change of the coal quality of the current thermal power generating unit.
2. In conventional automatic control of secondary dampers, the secondary damper is typically adjusted based on the differential pressure between the furnace and the secondary windbox under different loads. The method can only realize the adjustment of the air door aiming at the unit load or the coal quantity, but cannot realize the mode of changing the combustion by changing the opening degree of each adjusting door, and in the prior operation process, the adjustment of the secondary air door is mainly realized by manually setting the offset by an operator. The invention corrects the secondary air damper regulation output of the boiler according to the coal quality correction coefficient, regulates the integral combustion state of secondary air auxiliary air, and performs smooth undisturbed regulation on the secondary air regulation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a process diagram of a conventional work coal-to-coal ratio coal quality correction method.
Fig. 2 is a control block diagram of a conventional coordinated control system.
FIG. 3 is a diagram of the adaptive BTU coal correction coefficient calculation and correction process.
FIG. 4 is a system control diagram of the coordinated control system in the operation state of the adaptive BTU coal quality correction system.
FIG. 5 is a diagram of a process for calculating feedforward coefficients of each layer of a secondary air damper of a boiler by using an adaptive BTU coal quality correction coefficient.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, 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 some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
As shown in fig. 3, an embodiment of the present invention discloses a coordination control method under a coal-fired cogeneration unit adaptive BTU, including the following steps:
step 1, obtaining standard coal amount under different power generation quantities, and taking the standard coal amount as a reference coal amount; in this embodiment, the standard coal amount is obtained through a combustion test of a real dynamic thermal power generating unit standard coal or a coal type close to the standard coal, a function generator f1 (x) in fig. 3 is a reference coal amount instruction function generator, and the function of the function is to convert the real load of the unit into a corresponding reference coal feeding amount instruction, and specific parameters of the function are as shown in table 1 below.
TABLE 1
| Unit load (MW) | Reference coal amount (kg/s) |
| 0 | 0 |
| 330 | 36 |
Step 2, the obtained standard coal quantity is subjected to timing detection and optimized output of a coal quality correction coefficient BTU under the stable combustion working condition of the unit through the logic configuration of a distributed control system; specifically, the coal quality correction coefficient BTU is a process variable obtained by sampling an actual coal amount in real time through a power plant sensor, calculating a current coal amount in real time, and dividing the current coal amount by a reference coal amount. Wherein, BTU normally calculates under the boiler is in stable burning operating mode, and BTU stops calculating when the boiler burning is unstable, predetermines unstable operating mode of boiler burning and includes following several: (a) In the process of starting and stopping the mill, (b) the load instruction of the unit changes within 600 seconds; (c) the deviation of the main steam pressure is more than 0.3Mpa; (d) a power deviation greater than 15MW; (e) boiler MFT signal trigger; (f) When the signal quality of the main water supply flow, the coal feeding amount of a single coal mill and the fuel flow in the operation process of an oil gun is in fault; (g) coordinate the excision.
In the logic configuration of the distributed control system, the influence factors in the calculation process of determining the coal quality correction coefficient comprise: the method comprises the steps of actual power of a unit, load instructions of the unit, pressure deviation, main water supply flow, coal feeding amount of a single coal mill and fuel flow in the operation process of an oil gun.
And 3, correcting differential feedforward of main steam pressure deviation, proportional feedforward of unit load instructions and proportional coefficients of a boiler main control through the coal quality correction coefficient BTU, further correcting a fuel main control, and correcting the adjustment output of a secondary air door of the boiler through the coal quality correction coefficient. The secondary air is combustion-supporting air, firstly, air required by combustion is supplemented, a disturbance effect is achieved, the mixing of gas and solid is enhanced, the secondary air damper of the boiler is corrected according to the coal quality correction coefficient to adjust output, and the overall combustion state of secondary air auxiliary air is adjusted.
As a preferred embodiment, in step 2, the coal quality correction coefficient is also optimized in real time by the following method: and multiplying the total coal quantity detected by the primary element by the coal quality correction coefficient BTU to obtain the standard coal quantity corresponding to the current coal type of the unit, and optimizing the coal quality correction coefficient in real time by continuously correcting the standard coal quantity corresponding to the current coal type and the reference coal quantity.
And correcting the BTU coal quality correction coefficient according to the coal quantity deviation value, correcting the BTU coal quality correction coefficient in a negative direction when the coal quantity deviation is more than 0.5%, and correcting the BTU coal quality correction coefficient in a positive direction when the coal quantity deviation is less than-0.5%, wherein the specific correction method is determined by a BTU correction function generator. And determining the proportion and integral coefficient of PID (proportion integration differentiation) adjusting parameters of the coal quality correction coefficient according to the actual working condition. The specific parameters of the BTU correction function generator are shown in table 2 below.
TABLE 2
| Deviation of coal amount (%) | BTU correction value |
| -0.5 | 1 |
| 0 | 0 |
| 0.5 | -1 |
And determining proportion and integral coefficients of PID (proportion integration differentiation) adjusting parameters of the coal quality correction coefficient according to actual working conditions. In this example, the upper and lower limits of PID adjustment are 1.2 and 0.8, respectively, the proportionality coefficient is 0.001, and the integration time is 350 seconds.
As shown in fig. 4, the modifying of the differential feedforward of the main steam pressure deviation, the proportional feedforward of the unit load instruction, and the proportional coefficient of the boiler main control by the coal quality correction coefficient BTU specifically includes:
the coal quality correction coefficient BTU corrects differential feedforward of main steam pressure deviation through a function generator f1 (x), and the correction coefficient is k 1 F1 (x) is a proportional link, k 1 The value change trend is opposite to the BTU change trend, the feedforward quantity is increased when the coal quality is poor, and the differential feedforward of the main steam pressure deviation refers to the differential feedforward formed by comparing the deviation between the main steam pressure set value and the actual value of the boiler with the output value of the deviation value after passing through an inertial lag link and finally outputting the control quantity.
Correcting the proportion feedforward of the unit load instruction through a function generator f2 (x) according to a coal quality correction coefficient BTU, wherein the correction coefficient is k 2 F2 (x) is a proportional element, k 2 The value change trend is opposite to the BTU change trend, the feedforward quantity is increased when the coal quality is poor, the quick response of the main steam pressure is ensured, and the proportion feedforward of the unit load instruction is that a fixed boiler main control instruction feedforward is generated by the unit load instruction through a function.
And correcting a proportional coefficient K of the boiler master control through a function generator f3 (x) according to the coal quality correction coefficient BTU, wherein the K value change trend is opposite to the BTU change trend, the proportional action is increased when the coal quality is poor, and the pressure stability is realized by changing more coal quantity.
And adding the differential feedforward of the corrected main steam pressure deviation and the corrected unit load instruction proportional feedforward to be used as the feedforward of the new boiler main control, and simultaneously using the corrected boiler main control proportional coefficient K together as the input quantity of a follow-up boiler main control PID link to realize the output control of the boiler main control.
Example 1
In the embodiment, the power plant boiler is a 300MW (combined heat and power) coal-fired power generator set, the model is BLK-1025, subcritical parameters are adopted, a direct-blowing pulverizing system, double combustion chambers, 100% fly ash re-combustion and a direct-current liquid slag discharging furnace are adopted, and two medium-speed coal mills are designed on each side of the double combustion chambers. 16 cyclone burners are arranged on the top of the combustion chamber, and one coal mill is matched with four burners at different positions. The rotational flow regulation of the central air pipe and the secondary air pipe is designed for ensuring the stable burner for burning. The practical application numerical example of the 300MW cogeneration unit is as follows:
1. coal quality correction factor output example
Under the condition of setting the combustion state of standard coal, namely under the condition of 4% oxygen content, the current load is 330MW, and the total coal supply amount is 36kg/s, when the coal quality is changed, if the coal quality is deteriorated, the coal supply amount is inevitably increased on the premise of ensuring the unit load, but the change of the air volume is very small, and if the total coal amount is changed into 36.8kg/s after correction. According to the adaptive BTU coal quality correction coefficient operation and correction process diagram of FIG. 3, the corrected coal quantity is subtracted by the reference coal quantity calculated by the function generator f1 (x), the difference is divided by the reference coal quantity to obtain a percentage, namely 2.2%, the value is passed through a BTU correction function generator f2 (x), the function sets the BTU correction PID deviation input to-1 according to the coal quantity deviation value, and the BTU coefficient is corrected in the negative direction. The proportional and integral coefficients of the PID adjustment parameters of the coal quality correction coefficient are 0.001 and 350 respectively. Meanwhile, the upper limit and the lower limit of PID regulation are respectively 1.2 and 0.8. Assuming that the working conditions at this time are satisfied simultaneously: and if the conditions that the load instruction is not changed, the main steam pressure and the power deviation are not large, no MFT signal is triggered, the quality of a relevant measuring point is bad and the like are not met in the process of starting and stopping the mill, the coal quality correction coefficient BTU can be output in an accumulated mode, and the real-time coal quality correction coefficient is calculated.
2. Example of coal correction factor to boiler master control and fuel master control correction
Table 3, table 4 and Table 5 show the k values generated by the function generator f1 (x) 1 K generated by function generator f2 (x) 2 Function ofGenerator f3 (x) generates a proportionality coefficient K for the boiler master control.
TABLE 3
| Coal quality correction coefficient BTU | Correction factor k 1 |
| 1.2 | 0.85 |
| 1.1 | 0.95 |
| 1 | 1 |
| 0.9 | 1.1 |
| 0.85 | 1.2 |
| 0.8 | 1.4 |
TABLE 4
| Coal quality correction coefficient BTU | Correction factor k 2 |
| 1.2 | 1.25 |
| 1.1 | 1.35 |
| 1 | 1.5 |
| 0.9 | 1.8 |
| 0.85 | 1.95 |
| 0.8 | 2.15 |
TABLE 5
| Coal quality correction coefficient BTU | Coefficient of proportionality K |
| 1.2 | 0.85 |
| 1.1 | 0.96 |
| 1 | 1 |
| 0.9 | 1.05 |
| 0.85 | 1.1 |
| 0.8 | 1.2 |
As can be seen from the values in tables 3, 4, and 5, k fluctuates around 1 as the coal quality correction factor BTU fluctuates 1 、k 2 The K value change trend is opposite to the BTU change trend, when the coal quality correction coefficient BTU is 1 and 0.9, the K1 value is from 1 to 1.1, the K2 value is from 1.5 to 1.8, and the proportional coefficient K value change is from 1 to 1.05. The specific parameters in tables 3, 4 and 5 are the results calculated according to the corresponding parameters under different working conditions of different loads during the operation of the unit.
As shown in fig. 4, if the operating condition at this time is: the unit load is 330MW, the actual pressure is 16.9MPa, the set pressure is 17.3MPa, the deviation between the set pressure and the actual pressure is 0.4MPa, the output of the deviation value after passing through an inertial lag link is 0.15MPa, the standard coal quantity is 36kg/s, and the actual coal quantity is 36.8kg/s. At this time, the load is stable, the parameters are stable, and the oil gun operation is not performed, and if the coal quality correction coefficient PID calculation result is 0.9, k1=1.1, k2=1.8, and k3=1.05.
Then the differential feedforward calculation result of the coal quality correction coefficient to the main steam pressure deviation at this time is as follows: 0.15 × 1.1=0.165.
The proportion feedforward calculation result of the coal correction coefficient to the unit load instruction is as follows: 0.92 × 1.8=1.656. Wherein 0.92 is the unit load instruction which is calculated and output by a function generator f (x) and is the action intensity of the coal quality correction coefficient under different unit loads.
The feed forward summary of boiler master control is: 0.165+1.656=1.821.
The result of the calculation of correcting the proportionality coefficient of the boiler master control by the coal quality correction coefficient is 1.05.
And inputting the data into a PID regulator, regulating the output of the boiler main control, and continuously calculating and correcting the fuel main control by the boiler main control output and the corrected total coal quantity.
3. Coal quality correction coefficient correction boiler secondary air damper regulation output example
The secondary air is combustion-supporting air, firstly, air required by combustion is supplemented, a disturbance effect is achieved, the mixing of gas and solid is enhanced, the secondary air damper of the boiler is corrected according to the coal quality correction coefficient to adjust the output, and the overall combustion state of the secondary air auxiliary air is adjusted. In this embodiment, the overall combustion state of the secondary air auxiliary air is adjusted, and the secondary air auxiliary air is automatically adjusted without depending on manual control, but may be manually intervened, as shown in fig. 5.
And correcting the actual coal amount of the single coal feeder according to the coal quality correction coefficient and the artificial manual bias. And dividing the corrected single coal feeding quantity by 4 to obtain a theoretical coal discharge quantity, and calculating the theoretical coal discharge quantity through a function generator f (x) to obtain a theoretical secondary air discharge quantity. And carrying out PID calculation on the deviation of the secondary air flow and the final deviation of the actual secondary air flow to obtain the secondary air flow regulation output.
In conclusion, the invention can effectively solve the problem of poor automatic control quality of the thermal power generating unit caused by large coal quality change of the current thermal power generating unit.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (1)
1. A coordination control method under a coal-fired cogeneration unit self-adaptive BTU is characterized by comprising the following steps:
step 1, obtaining standard coal amount under different generating capacities, and taking the standard coal amount as a reference coal amount, wherein the standard coal amount is obtained through a combustion test of actual dynamic standard coal or coal types close to the standard coal of a thermal power generating unit;
step 2, the obtained standard coal quantity is subjected to timing detection and optimized output of a coal quality correction coefficient BTU under the stable combustion working condition of the unit through the logic configuration of a distributed control system; coal quality correction coefficient BTU is for sampling in real time actual coal volume through power plant's sensor, calculates current coal volume in real time to divide by benchmark coal volume, the process variable who obtains, wherein, BTU normally calculates under being in the stable combustion operating mode when the boiler, BTU stops calculating when the boiler combustion is unstable, predetermines the unstable operating mode of boiler combustion and includes following several kinds: (a) In the process of starting and stopping the mill, (b) the load instruction of the unit changes within 600 seconds; (c) the deviation of the main steam pressure is larger than 0.3Mpa; (d) a power deviation greater than 15MW; (e) boiler MFT signal trigger; (f) When the signal quality of the main water supply flow, the coal feeding amount of a single coal mill and the fuel flow in the operation process of an oil gun is in fault; (g) in coordinative excision;
optimizing the coal quality correction coefficient in real time by the following method: multiplying the total coal quantity detected by the primary element by the coal quality correction coefficient BTU to obtain a standard coal quantity corresponding to the current coal type of the unit, and optimizing the coal quality correction coefficient in real time by continuously correcting the standard coal quantity corresponding to the current coal type and the reference coal quantity;
step 3, correcting differential feedforward of main steam pressure deviation, proportional feedforward of unit load instruction and proportional coefficient of boiler main control through the coal quality correction coefficient BTU, further correcting the fuel main control, and correcting the adjustment output of a secondary air door of the boiler through the coal quality correction coefficient;
correcting the BTU coal quality correction coefficient according to the coal quantity deviation value, correcting the BTU coal quality correction coefficient to the negative direction when the coal quantity deviation is more than 0.5%, and correcting the BTU coal quality correction coefficient to the positive direction when the coal quantity deviation is less than-0.5%, wherein the specific correction method is determined by a BTU correction function generator, and the proportion and the integral coefficient of PID (proportion integration differentiation) adjusting parameters of the coal quality correction coefficient are determined according to the actual working condition;
the upper limit and the lower limit of PID regulation are 1.2 and 0.8 respectively;
the method specifically comprises the following steps of correcting differential feedforward of main steam pressure deviation, proportional feedforward of unit load instructions and proportional coefficients of boiler main control through the coal quality correction coefficient BTU, wherein the correction specifically comprises the following steps:
the coal quality correction coefficient BTU corrects differential feedforward of main steam pressure deviation through a function generator f1 (x), and the correction coefficient is k 1 F1 (x) is a proportional element, k 1 The value change trend is opposite to the BTU change trend, the feedforward quantity is increased when the coal quality is poor, and the differential feedforward of the main steam pressure deviation refers to the differential feedforward formed by comparing the deviation between the main steam pressure set value and the actual value of the boiler with the output value of the deviation value after passing through an inertial lag link and finally outputting a control quantity;
correcting the proportion feedforward of the unit load instruction through a function generator f2 (x) according to a coal quality correction coefficient BTU, wherein the correction coefficient is k 2 F2 (x) is a proportional link, k 2 The value change trend is opposite to the BTU change trend, the feedforward quantity is increased when the coal quality is poor, the quick response of the main steam pressure is ensured, and the proportion feedforward of the unit load instruction is that a fixed boiler main control instruction feedforward is generated by the unit load instruction through a function;
correcting a proportional coefficient K of the boiler main control through a function generator f3 (x) according to a coal quality correction coefficient BTU, wherein the change trend of the value of K is opposite to that of the BTU, the proportional action is increased when the coal quality is poor, and the pressure is stabilized by changing more coal quantity;
adding the differential feedforward of the corrected main steam pressure deviation and the corrected unit load instruction proportional feedforward to be used as the feedforward of a new boiler main control, and simultaneously using the corrected boiler main control proportional coefficient K together as the input quantity of a follow-up boiler main control PID link to realize the output control of the boiler main control;
in the logic configuration of the distributed control system, the influence factors in the calculation process of determining the coal quality correction coefficient comprise: the method comprises the steps of actual power of a unit, load instructions of the unit, pressure deviation, main water supply flow, coal feeding amount of a single coal mill and fuel flow in the operation process of an oil gun.
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