Superheat control method and system for supercritical thermal power units based on coal-water distribution coefficient

Abstract

The present invention discloses a superheat control method and system for a supercritical thermal power unit based on a coal-water distribution coefficient, and belongs to the technical field of thermal power unit control. First, the coal-water distribution coefficient is calculated according to the main steam pressure feedback value, the main steam pressure setting value, the superheat setting value and the superheat feedback value; then, the water supply correction instruction is calculated according to the superheat setting value, the superheat feedback value and the coal-water distribution coefficient; the coal supply correction instruction is calculated according to the superheat setting value, the superheat feedback value and the coal-water distribution coefficient; finally, the water supply correction instruction is sent to the water supply main control, and the coal supply correction instruction is sent to the fuel main control. The present invention introduces the coal-water distribution coefficient into the superheat control strategy, so that the coal quantity and water quantity of the unit cooperate with each other and act reasonably, while suppressing the superheat deviation, taking into account the control of the main steam pressure, thereby obtaining a better control effect and ensuring the safe operation of the unit.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal power generation unit control, and in particular relates to a supercritical thermal power unit superheat control method and system based on a coal-water distribution coefficient. Background Art

[0002] In recent years, with the improvement of environmental protection assessment indicators and the increase of competitive pressure, the living environment of thermal power plants has become increasingly complex. Not only must they ensure safe production, but they must also pursue lower coal consumption for power generation and higher profits. In this context, supercritical units have gained more and more attention. Compared with subcritical units, supercritical units have high thermal efficiency and low heat consumption, which can effectively reduce energy consumption and pollutant emissions. In addition, the boiler has small inertia and fast load change rate, which is very suitable for the current trend of peak load regulation of coal-fired units. Therefore, so far, supercritical direct current units have become the mainstream of domestic thermal power plant development.

[0003] Although supercritical direct-flow boilers have many advantages, the control difficulty of the unit increases sharply as the boiler's heat storage capacity decreases, the main parameters increase, and the degree of coal-water coupling increases. Any unreasonable movement of the amount of coal and water entering the boiler will have a direct impact on the main steam pressure and main steam temperature, and the fluctuation of important parameters such as main steam temperature and main steam pressure will not only affect the unit's ability to carry load, but also cause huge hidden dangers to the safe operation of the unit. Therefore, compared with subcritical units, supercritical units have higher requirements for control systems.

[0004] Among them, superheat is an important parameter for coordinated control of supercritical units, and its control effect will have a direct impact on the main steam temperature. Only by controlling the fluctuation of superheat within a reasonable range can the main steam temperature achieve better control effect. The control effect of superheat is seriously coupled with the action of coal and water volume of the unit. Only when the action of coal and water volume is reasonable can the disturbance of superheat be effectively suppressed.

[0005] In traditional superheat control strategies, a single amount of coal or water is usually used to adjust the superheat. Although this can achieve better control effects, due to the serious coupling between the main steam temperature and pressure of supercritical units, traditional control strategies do not take into account the main steam pressure while adjusting the superheat. In some specific cases, this will cause the main steam pressure deviation to increase, affecting the safe operation of the unit. Summary of the invention

[0006] In order to solve the defects existing in the above-mentioned prior art, the purpose of the present invention is to provide a superheat control method and system for a supercritical thermal power unit based on the coal-water distribution coefficient. By introducing the coal-water distribution coefficient into the superheat control strategy, the coal quantity and water quantity of the unit are coordinated with each other and operate reasonably. While suppressing the superheat deviation, the control of the main steam pressure is taken into account, thereby obtaining a better control effect and ensuring the safe operation of the unit.

[0007] The present invention is achieved through the following technical solutions:

[0008] A superheat control method for a supercritical thermal power unit based on a coal-water distribution coefficient, comprising:

[0009] S1: The coal-water distribution coefficient is calculated based on the main steam pressure feedback value, the main steam pressure setting value, the superheat setting value and the superheat feedback value;

[0010] S2: Calculate the feed water correction value instruction according to the superheat setting value, superheat feedback value and the coal-water distribution coefficient obtained by S1;

[0011] S3: Calculate the coal feed correction instruction based on the superheat setting value, superheat feedback value and the coal-water distribution coefficient obtained in S1;

[0012] S4: Send the water supply correction value instruction obtained in S2 to the water supply main control;

[0013] S5: Send the coal feed correction instruction obtained in S3 to the fuel main control.

[0014] Preferably, S1 is specifically: a differential signal of the main steam pressure feedback value is calculated from the main steam pressure feedback value; a signal obtained by superimposing the differential signal of the main steam pressure feedback value from the main steam pressure setting value and the main steam pressure feedback value to obtain a main steam pressure deviation signal;

[0015] The superheat feedback value differential signal is calculated from the superheat feedback value; the superheat deviation signal is obtained by subtracting the superheat feedback value differential signal from the superheat set value and superheat feedback value.

[0016] The main steam pressure deviation signal is multiplied by the superheat deviation signal, and the result is converted into the coal-water distribution coefficient through a piecewise function.

[0017] Further preferably, after the main steam pressure deviation signal is multiplied by the superheat deviation signal, if the result is a positive number, the unit superheat is adjusted by correcting the coal amount; if the result is 0 or a negative number, the unit superheat is adjusted by correcting the water amount.

[0018] Preferably, S2 is specifically: the result obtained by subtracting the superheat feedback value from the superheat setting value is multiplied by the coal-water distribution coefficient obtained by S1, the result obtained is added to the superheat feedback value, the result obtained is used as the feedback value of the PID controller, the superheat setting value is used as the setting value of the PID controller, and the water feed correction instruction is calculated by the PID controller.

[0019] Preferably, S3 is specifically: the coal-water distribution coefficient is obtained by subtracting S1 from the constant 1, the result is multiplied by the result obtained by subtracting the superheat feedback value from the superheat setting value, the result is added to the superheat feedback value, the result is used as the feedback value of the PID controller, the superheat setting value is used as the setting value of the PID controller, and the coal feeding correction amount instruction is calculated by the PID controller.

[0020] Preferably, S4 is specifically as follows: inputting the boiler master control signal into the boiler load-water volume curve, adding the result obtained by adding the sum of the feed water correction instruction obtained by S2 and the feed water dynamic feedforward, and obtaining the boiler total water volume instruction to be sent to the feed water master control.

[0021] Preferably, S5 is specifically as follows: inputting the boiler master control signal into the boiler load-coal quantity curve, adding the result obtained by S3 to the sum of the coal feed correction instruction and the coal feed dynamic feedforward, and obtaining the boiler total coal quantity instruction to be sent to the fuel master control.

[0022] The present invention discloses a system for realizing the above-mentioned supercritical thermal power unit superheat control method based on coal-water distribution coefficient, comprising:

[0023] The coal-water distribution coefficient calculation unit calculates the coal-water distribution coefficient according to the main steam pressure feedback value, the main steam pressure setting value, the superheat setting value and the superheat feedback value;

[0024] The feed water correction quantity instruction calculation unit calculates the feed water correction quantity instruction according to the superheat setting value, the superheat feedback value and the coal-water distribution coefficient;

[0025] The coal feeding correction amount instruction calculation unit calculates the coal feeding correction amount instruction according to the superheat setting value, the superheat feedback value and the coal-water distribution coefficient;

[0026] The water supply correction quantity instruction sending unit sends the water supply correction quantity instruction to the water supply main control;

[0027] The coal feeding correction amount instruction sending unit sends the coal feeding correction amount instruction to the fuel main control.

[0028] Compared with the prior art, the present invention has the following beneficial technical effects:

[0029] The superheat control method of a supercritical thermal power unit based on the coal-water distribution coefficient disclosed in the present invention, compared with the traditional superheat control method, introduces the concept of the coal-water distribution coefficient in the superheat control, takes into account the control of the main steam pressure while adjusting the superheat, and quickly suppresses the superheat deviation without causing the main steam pressure control effect to deteriorate and affecting the safe operation of the unit. At the same time, compared with the traditional superheat control method, the present invention no longer relies solely on a single coal amount or water amount to adjust the superheat, but introduces the coal-water distribution coefficient to make the coal amount and the water amount cooperate with each other. By analyzing the superheat deviation and its changing trend and the main steam pressure deviation and its changing trend, the distribution coefficient is changed reasonably, and different adjustment strategies are adopted for different working conditions, so as to obtain better control effects. .

[0030] The superheat control system of a supercritical thermal power unit based on a coal-water distribution coefficient disclosed by the invention has the advantages of simple construction, high automation and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a system logic diagram of the present invention;

[0032] Figure 2 It is a logic diagram of the total water supply instruction and total coal supply instruction calculation system of the present invention;

[0033] Figure 3 It is a system schematic diagram of the present invention.

[0034] In the figure: 1 to 33 are signals 1 to 33 respectively, F1 is the separator outlet temperature signal, F2 is the separator outlet pressure signal, F3 is the superheat setting value signal, F4 is the superheat feedback value signal, f(x) is the pressure corresponding to the saturation temperature curve, WFR is the superheat control system, F5 is the water quantity correction signal, F6 is the coal quantity correction signal, FWD is the water supply master control, and FMD is the fuel master control. DETAILED DESCRIPTION

[0035] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments, which are intended to explain the present invention rather than to limit it.

[0036] like Figure 3As shown, the system and main technical ideas of this embodiment are as follows: take the steam-water separator outlet temperature measurement point signal F1, the separator outlet pressure signal F2, and the superheat setting value signal F3 manually set by the operator, subtract the saturation temperature corresponding to the signal F2 from the signal F1, and obtain the superheat feedback value signal F4, send the signal F3 and the signal F4 to the superheat control system WFR, calculate and obtain the water supply correction signal F5 and the coal supply correction signal F6, send F5 to the unit water supply main control FWD, send F6 to the unit fuel main control FMD, correct the total coal quantity signal and the total water quantity signal, adjust the boiler coal supply and water supply, and control the unit superheat.

[0037] like Figure 1 and Figure 2 As shown, the system of this embodiment includes a PID module, a plurality of analog input modules, an inertia module, an addition module, a piecewise function module, an analog output module and a multiplication module. The superheat control method of a supercritical thermal power unit based on a coal-water distribution coefficient of the present invention includes the following steps:

[0038] Step 1: Calculate the coal-water distribution coefficient as follows:

[0039] Signal 1 (main steam pressure feedback value) is input into an inertial module to obtain signal 3. Signal 3 is subtracted from signal 1 to obtain signal 4 (differential signal of main steam pressure feedback value). Signal 1 is superimposed on signal 4 to obtain signal 5. Signal 5 is subtracted from signal 2 (main steam pressure setting value) to obtain signal 6 (main steam pressure deviation signal). Similar to the processing method of main steam pressure, signal 7 (superheat feedback value) passes through an inertial module to obtain signal 9. Signal 7 is subtracted from signal 9 to obtain signal 10 (differential signal of superheat feedback value). Signal 7 and signal 10 are superimposed to obtain signal 11. Signal 11 is subtracted from signal 8 (superheat setting value) to obtain signal 12 (superheat deviation signal). After processing, signal 6 (main steam pressure deviation signal) is multiplied by signal 12 (superheat deviation signal) to obtain signal 13. When signal 13 is a positive number, it means that the main steam pressure is overpressure and the superheat is higher than the set value, or the main steam pressure is underpressure and the superheat is lower than the set value. In this case, the superheat should be adjusted with coal as much as possible. When signal 13 is a negative number, it means that the main steam pressure is overpressure and the superheat is lower than the set value, or the main steam pressure is underpressure and the superheat is higher than the set value. In this case, water should be used to adjust the superheat. Signal 13 is then converted into signal 14 (coal-water distribution coefficient) through the piecewise function module. The value range of signal 14 is [0, 1], and the piecewise function settings are shown in Table 1.

[0040] Table 1

[0041] X -10 -5 -3 -1 0 1 3 5 10 Y 1 1 1 1 1 0.7 0.5 0.4 0.3

[0042] Step 2: Calculate the water supply correction instruction as follows:

[0043] After obtaining signal 14 (coal-water distribution coefficient), subtract signal 7 (superheat feedback value) from signal 8 (superheat setting value) to obtain signal 15, and then multiply signal 15 by signal 14 to obtain signal 16. Add signal 16 to signal 7 to obtain signal 17. Using signal 8 as the setting value of the PID control module and signal 17 as the feedback value of the PID controller module, signal 18 (water volume instruction for adjusting superheat) can be calculated by the PID module.

[0044] Step 3: Calculate the coal feed correction instruction as follows:

[0045] After obtaining signal 14 (coal-water distribution coefficient), subtract signal 14 from signal 19 (constant 1) to obtain signal 20. Subtract signal 7 (superheat feedback value) from signal 8 (superheat setting value) to obtain signal 21, and then multiply signal 21 by signal 20 to obtain signal 22. Add signal 22 to signal 7 to obtain signal 23. Using signal 8 as the setting value of the PID module and signal 23 as the feedback value of the PID control module, signal 24 (coal quantity instruction for adjusting superheat) can be calculated by the PID module.

[0046] Step 4: Send the water supply correction amount to the water supply main control as follows:

[0047] Signal 18 (feedwater correction) is added to signal 25 (feedwater dynamic feedforward) to obtain signal 28, and signal 26 (boiler master control) is sent to multi-terminal function module 1. The function module outputs signal 29, and the function is the boiler load-water volume curve. Signal 29 is added to signal 28 to obtain signal 32 (boiler total water volume instruction).

[0048] Step 5: Send the coal feed correction amount to the fuel master control as follows:

[0049] Signal 24 (coal correction) and signal 27 (coal dynamic feedforward) are added to obtain signal 31, and signal 26 (boiler master control) is sent to multi-terminal function module 2. The function module outputs signal 30, and the function is the boiler load-coal quantity curve. Signal 30 and signal 31 are added to obtain signal 33 (boiler total coal quantity instruction).

[0050] It should be noted that the above is only a part of the implementation of the present invention, and equivalent changes made to the system described in the present invention are all included in the protection scope of the present invention. Those skilled in the art of the present invention can replace the specific examples described in a similar manner, as long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they all belong to the protection scope of the present invention.

Claims

1. A superheat control method for a supercritical thermal power unit based on a coal-water distribution coefficient, characterized in that: include: S1: The coal-water distribution coefficient is calculated according to the main steam pressure feedback value, the main steam pressure setting value, the superheat setting value and the superheat feedback value. Specifically, the differential signal of the main steam pressure feedback value is calculated from the main steam pressure feedback value; the main steam pressure deviation signal is obtained by superimposing the differential signal of the main steam pressure setting value minus the main steam pressure feedback value and the main steam pressure feedback value; The superheat feedback value differential signal is calculated from the superheat feedback value; the superheat deviation signal is obtained by subtracting the superheat feedback value differential signal from the superheat set value and superheat feedback value. The main steam pressure deviation signal is multiplied by the superheat deviation signal, and the result is converted into the coal-water distribution coefficient through a piecewise function; S2: Calculate the feed water correction value instruction according to the superheat setting value, superheat feedback value and the coal-water distribution coefficient obtained by S1; S3: Calculate the coal feed correction instruction based on the superheat setting value, superheat feedback value and the coal-water distribution coefficient obtained in S1; S4: Send the water supply correction value instruction obtained in S2 to the water supply main control; S5: Send the coal feed correction instruction obtained in S3 to the fuel main control.

2. After the main steam pressure deviation signal is multiplied by the superheat deviation signal, if the result is a positive number, the unit superheat is adjusted by correcting the coal amount; if the result is 0 or a negative number, the unit superheat is adjusted by correcting the water amount.

3. The superheat control method of a supercritical thermal power unit based on the coal-water partition coefficient according to claim 1, characterized in that: Specifically, S2 is: the result obtained by subtracting the superheat feedback value from the superheat setting value is multiplied by the coal-water distribution coefficient obtained by S1, and the result is added to the superheat feedback value. The result is used as the feedback value of the PID controller, and the superheat setting value is used as the setting value of the PID controller. The water feed correction instruction is calculated by the PID controller.

4. The superheat control method of a supercritical thermal power unit based on the coal-water partition coefficient according to claim 1, characterized in that: S3 is specifically: the coal-water distribution coefficient is obtained by subtracting S1 from the constant 1, the result is multiplied by the result obtained by subtracting the superheat feedback value from the superheat setting value, the result is added to the superheat feedback value, the result is used as the feedback value of the PID controller, the superheat setting value is used as the setting value of the PID controller, and the coal feeding correction instruction is calculated by the PID controller.

5. The superheat control method of a supercritical thermal power unit based on the coal-water partition coefficient according to claim 1, characterized in that: S4 is specifically as follows: the boiler master control signal is input into the boiler load-water volume curve, the result is added to the sum of the feed water correction command obtained in S2 and the feed water dynamic feedforward, and the boiler total water volume command is obtained and sent to the feed water master control.

6. The superheat control method of a supercritical thermal power unit based on the coal-water partition coefficient according to claim 1, characterized in that: S5 is specifically as follows: input the boiler master control signal into the boiler load-coal quantity curve, add the result obtained by S3 to the sum of the coal feed correction instruction and the coal feed dynamic feedforward, and obtain the boiler total coal quantity instruction to be sent to the fuel master control.

7. A system for implementing the superheat control method of a supercritical thermal power unit based on the coal-water partition coefficient as described in any one of claims 1 to 6, characterized in that: include: The coal-water distribution coefficient calculation unit calculates the coal-water distribution coefficient according to the main steam pressure feedback value, the main steam pressure setting value, the superheat setting value and the superheat feedback value; The feed water correction quantity instruction calculation unit calculates the feed water correction quantity instruction according to the superheat setting value, the superheat feedback value and the coal-water distribution coefficient; The coal feeding correction amount instruction calculation unit calculates the coal feeding correction amount instruction according to the superheat setting value, the superheat feedback value and the coal-water distribution coefficient; The water supply correction quantity instruction sending unit sends the water supply correction quantity instruction to the water supply main control; The coal feeding correction amount instruction sending unit sends the coal feeding correction amount instruction to the fuel main control.

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