Supercritical unit boiler master variable speed control system and method

Abstract

A kind of supercritical unit boiler main control variable speed control system and method, it is related to thermal power generation field, for correcting the proportion and integral coefficient of PID adjustment link of main steam pressure deviation, coal quality, load instruction, main steam pressure deviation process quantity are introduced in the process of boiler main control adjustment, the proportion coefficient and integral coefficient of PID adjustment link of main steam pressure deviation are corrected, the intensity of boiler main control adjustment is corrected, by judging the amplitude and duration that main steam pressure deviates from target value, in combination with boiler combustion characteristics, realize the timing variable speed regulation of boiler main control, the problem of supercritical unit boiler main steam pressure control fluctuation and long time deviation from target value is solved.

Description

Technical Field

[0001] This invention relates to the field of thermal power generation, and specifically to a main control speed change control system and method for a supercritical unit boiler. Background Technology

[0002] Supercritical thermal power units have become the mainstay of the power industry. For supercritical thermal power units, steam temperature and pressure are crucial parameters for enthalpy, as their levels determine the steam enthalpy and the work capacity per unit flow rate of steam. Supercritical DC unit generators inherently possess characteristics such as pure delay, large inertia, and nonlinearity. Multiple parameters within the unit are interconnected and mutually restrictive, exhibiting strong coupling characteristics. Changes in the energy landscape and the increasing demands for grid peak shaving and frequency regulation introduce numerous uncertain external disturbances to the unit generators. The marketization of coal and the blending of coal result in variable coal quality, further complicating the control of the unit generators. The boiler master control of supercritical units is the most critical link in adjusting steam flow and enthalpy. The aforementioned constraints place higher demands on the boiler master control of supercritical units. Improper boiler master control, in addition to affecting the unit's load regulation capacity, can also cause long-term exceedances or significant fluctuations in important parameters such as main steam pressure, impacting unit safety.

[0003] For supercritical DC units, the boiler main control mainly includes static fuel composition based on load commands and dynamic feedforward to compensate for heat storage during the initial dynamic load of the DC boiler. Based on this, the boiler main control regulator is designed as a PID control based on the deviation of the main steam pressure. Its main function is to eliminate the deviation of the steady-state main steam pressure and ensure that the main steam enthalpy and electrical power remain in balance.

[0004] In the prior art, Chinese invention patent application CN102563598A, published on July 11, 2012, entitled "Optimization Control Method for Main Control of Supercritical Unit Boiler", discloses an optimization control method for the main control of a supercritical unit boiler. When the AGC command changes significantly, the boiler main control can quickly and accurately output commands to the fuel main control and feedwater main control, thereby ensuring the control effect of the main steam pressure, ensuring the load response characteristics, and improving the control quality and economic indicators of the unit.

[0005] Dynamic feedforward control of boilers focuses on proactive regulation to compensate for the lag between boiler combustion and turbine work in supercritical units, but it cannot achieve quantitative control. In principle, there is a one-to-one correspondence between static fuel quantity and unit load in boiler main control. However, due to the uncertainty of coal quality, a mismatch occurs between static fuel quantity and unit load. PID control based on main steam pressure deviation is a supplementary regulation to the above two aspects. Currently, when tuning the PID parameters of boiler main control, changes in coal quality are not fully considered, resulting in frequent and large fluctuations or long-term large deviations in main steam pressure control. Summary of the Invention

[0006] The purpose of this invention is to design a main control speed change control system and method for supercritical boiler units, so as to solve the problems of main steam pressure control fluctuation and long-term deviation from the target value in supercritical boiler units.

[0007] The present invention solves the above-mentioned technical problems through the following technical solutions:

[0008] A supercritical boiler main control speed control system, comprising proportional and integral coefficients of the PID control link for correcting main steam pressure deviation, including: a first multiplier (10), a second multiplier (11), a third multiplier (12), a fourth multiplier (13), a fifth multiplier (14), a sixth multiplier (15), a subtractor (16), a first absolute value function (17), a second absolute value function (18), a unit state correction module (19), a main steam pressure deviation change direction correction module (20), and a main steam pressure deviation time over-limit correction module (21); fuel heat The following modules are defined: boiler main control proportional coefficient correction function module f(x1) corresponding to the value; boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load; boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load; boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation; boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation; boiler main control proportional coefficient correction function module f(x6) corresponding to the main steam pressure deviation derivative; first-order filter module f(t1); second-order filter module f(t2).

[0009] The output of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value is connected to the first input of the first multiplier (10). The output of the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load is connected to the second input of the first multiplier (10). The output of the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation is connected to the third input of the first multiplier (10). The output of the first multiplier (10) is connected to the first input of the second multiplier (11). The second input of the second multiplier (11) is connected to the output of the unit state correction module (19). The output of the second multiplier (11) is connected to the first input of the third multiplier (12). The second input of the third multiplier (12) is connected to the output of the boiler main control proportional coefficient correction function module f(x6) corresponding to the main steam pressure deviation differential. The boiler main control proportional coefficient correction function module f(x6) corresponding to the main steam pressure deviation differential is connected to the output of the boiler main control proportional coefficient correction function module f(x6). The input of the coefficient correction function module f(x6) is connected to the output of the second first-order filter module f(t2), the input of the second first-order filter module f(t2) is connected to the output of the first absolute value function (17), the input of the first absolute value function (17) is connected to the output of the subtractor (16), and the first input of the subtractor (16) is connected to the output of the first first-order filter module f(t1). The input of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value is input, the input of the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load is input, the input of the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation is input, the second input of the subtractor (16) and the input of the first first-order filter module f(t1) are both input to the main steam pressure deviation, and the output of the third multiplier (12) outputs the corrected proportional coefficient.

[0010] The output of the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load is connected to the first input of the fourth multiplier (13). The output of the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation is connected to the second input of the fourth multiplier (13). The output of the fourth multiplier (13) is connected to the first input of the fifth multiplier (14). The second input of the fifth multiplier (14) is connected to the output of the main steam pressure deviation change direction correction module (20). The input of the main steam pressure deviation change direction correction module (20) is connected to the output of the sixth multiplier (15). The first input of the sixth multiplier (15) is connected to the subtractor. The output of (16) is connected, the output of the second absolute value function (18) is connected to the input of the main steam pressure deviation time over-limit correction module (21), and the output of the main steam pressure deviation time over-limit correction module (21) is connected to the third input of the fifth multiplier (14). The unit load is input to the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load. The main steam pressure deviation is input to the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation, the second input of the sixth multiplier (15), and the input of the second absolute value function (18). The corrected integral coefficient is output to the output of the fifth multiplier (14).

[0011] The technical solution of this invention introduces coal quality, load command, and main steam pressure deviation process quantities into the boiler main control regulation process, corrects the proportional coefficient and integral coefficient of the PID regulation link of the main steam pressure deviation, corrects the boiler main control regulation intensity, and realizes the boiler main control timed variable speed regulation by judging the magnitude and duration of the main steam pressure deviation from the target value and combining the boiler combustion characteristics, thus solving the problem of main steam pressure control fluctuation and long-term deviation from the target value in supercritical unit boilers.

[0012] Further, the unit status correction module (19) includes: a first delay-on module (191), a first delay-off module (192), and a first selection module (193); the output terminal of the first delay-on module (191) is connected to the input terminal of the first delay-off module (192), the output terminal of the first delay-off module (192) is connected to the first input terminal of the first selection module (193), and the output terminal of the first selection module (193) is connected to the second input terminal of the second multiplier (11); the unit status is input at the input terminal of the first delay-on module (191), and the second and third input terminals of the first selection module (193) are respectively input to the variable load state correction constant A1 and the stable state correction constant A2. The first selection module (193) selects the variable load state correction constant A1 or the stable state correction constant A2 according to the signal input at its first input terminal and then outputs it.

[0013] Furthermore, the main steam pressure deviation change direction correction module (20) includes: a low threshold module (201), a second delay-on module (202), a second delay-off module (203), and a second selection module (204); the input terminal of the low threshold module (201) is connected to the output terminal of the sixth multiplier (15), the output terminal of the low threshold module (201) is connected to the input terminal of the second delay-on module (202), and the output terminal of the second delay-on module (202) is connected to the input terminal of the second delay-off module (204). The input terminal of the block (203) is connected, the output terminal of the second delay interrupt module (203) is connected to the first input terminal of the second selection module (204), and the output terminal of the second selection module (204) is connected to the second input terminal of the fifth multiplier (14). The second and third input terminals of the second selection module (204) correspond to the boiler main control integral time correction constants A3 and A4 corresponding to the differential of the main steam pressure deviation, respectively. The second selection module (204) selects to output A3 or A4 according to the signal input at its first input terminal.

[0014] Furthermore, the main steam pressure deviation time over-limit correction module (21) includes: a high limit threshold module (211), a third delay-through module (212), an SR trigger (213), a fourth delay-through module (214), a pulse generator (215), and a third selection module (216); the input terminal of the high limit threshold module (211) is connected to the output terminal of the second absolute value function (18), the output terminal of the high limit threshold module (211) is connected to the input terminal of the third delay-through module (212), the output terminal of the third delay-through module (212) is connected to the S port of the SR trigger (213), and the output terminal of the SR trigger (213) is connected to the fourth delay-through module (214). The input terminal of module (214) is connected to the input terminal of pulse generator (215). The output terminal of the fourth delay-through module (214) is connected to the R port of SR trigger (213). The output terminal of pulse generator (215) is connected to the first input terminal of third selection module (216). The output terminal of third selection module (216) is connected to the third input terminal of fifth multiplier (14). The second and third input terminals of third selection module (216) are respectively input to the boiler main control integral time correction constants A5 and A6 set according to the magnitude and duration of the deviation of main steam pressure from the target value. Third selection module (216) selects to output A5 or A6 according to the signal input at its first input terminal.

[0015] A control method for the supercritical unit boiler main control variable speed control system includes: correcting the proportional coefficient of the PID control link for the main steam pressure deviation; and correcting the integral coefficient of the PID control link for the main steam pressure deviation.

[0016] Furthermore, the method for correcting the proportional coefficient of the PID control link for the main steam pressure deviation is as follows:

[0017] The output signals of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value, the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load, and the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation are simultaneously input into the first multiplier (10) for multiplication to obtain the output signal u1. The signal u1 and the output signal u2 of the unit status correction module (19) are simultaneously input into the second multiplier (11) for multiplication to obtain the output signal u3.

[0018] The main steam pressure deviation and the main steam pressure deviation filtered by the first first-order filter module f(t1) are simultaneously input into the subtractor (16) for subtraction calculation to obtain the output signal u4. The signal u4 is then subjected to the absolute value of the first absolute value function (17), and then filtered by the second first-order filter module f(t2) before being input to the boiler main control proportional coefficient correction function module f(x6) corresponding to the differential of the main steam pressure deviation, thereby obtaining the output signal u5.

[0019] Signals u3 and u5 are simultaneously input into the third multiplier (12) to obtain the corrected proportional coefficient.

[0020] Furthermore, the method for correcting the integral coefficient of the PID control link for the main steam pressure deviation is as follows:

[0021] The output signals of the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load and the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation are simultaneously input into the fourth multiplier (13) for multiplication to obtain the output signal u6;

[0022] After the main steam pressure deviation and signal u4 are simultaneously input to the sixth multiplier (15), the signal u7 is output after being corrected by the main steam pressure deviation change direction correction module (20).

[0023] After the main steam pressure deviation is taken by the second absolute value function (18), it is then corrected by the main steam pressure deviation time over-limit correction module (21) and output signal u8.

[0024] Signals u6, u7 and u8 are simultaneously input into the fifth multiplier (14) to obtain the corrected integral coefficients.

[0025] The advantages of this invention are:

[0026] The technical solution of this invention introduces coal quality, load command, and main steam pressure deviation process quantities into the boiler main control regulation process, corrects the proportional coefficient and integral coefficient of the PID regulation link of the main steam pressure deviation, corrects the boiler main control regulation intensity, and realizes the boiler main control timed variable speed regulation by judging the magnitude and duration of the main steam pressure deviation from the target value and combining the boiler combustion characteristics, thus solving the problem of main steam pressure control fluctuation and long-term deviation from the target value in supercritical unit boilers. Attached Figure Description

[0027] Figure 1 This is a structural diagram of the supercritical unit boiler main control speed control system according to Embodiment 1 of the present invention;

[0028] Figure 2 This is a structural diagram of the unit state correction module of the supercritical unit boiler main control speed control system according to Embodiment 1 of the present invention;

[0029] Figure 3 This is a structural diagram of the main steam pressure deviation change direction correction module of the supercritical unit boiler main control speed control system according to Embodiment 1 of the present invention;

[0030] Figure 4 This is a structural diagram of the main steam pressure deviation time over-limit correction module of the supercritical unit boiler main control speed control system according to Embodiment 1 of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments:

[0033] Example 1

[0034] The supercritical unit is a three-input, three-output multivariable control system. The three inputs are: boiler main control command B (fuel quantity), feedwater flow command W, and turbine control valve opening μ. The three outputs are: power N, main steam pressure P, and separator outlet temperature T.

[0035] For most coordinated control systems that employ water-coal following and are based on boiler following, the time-domain command model of the regulation system can be described as follows:

[0036] Steam turbine control valve opening:

[0037] μ=f1(N0)+K P1 ·ΔN+∫ΔN·dt+dΔN / dt

[0038] Boiler main control commands:

[0039] B = B1 + B2

[0040] B1 = f2(N0)

[0041] B2 = K P2 ·ΔP+∫ΔP·dt+dΔP / dt

[0042] Water supply flow rate:

[0043] W = f3(B) + K P3 ·ΔT+∫ΔT·dt+dΔT / dt

[0044] In the formula, N0 is the unit load, f1 is the turbine main control feedforward function with load command N0 as the variable, f3 is the set coal-water relationship function, f2 is the boiler main control feedforward function, B1 mainly includes the static coal quantity based on the load command and the dynamic coal quantity with the load command change as the variable, and B2 is the PID control link based on the main steam pressure deviation.

[0045] like Figure 1 As shown, a supercritical unit boiler main control speed control system includes proportional and integral coefficients for the PID control link used to correct the main steam pressure deviation, comprising: a first multiplier (10), a second multiplier (11), a third multiplier (12), a fourth multiplier (13), a fifth multiplier (14), a sixth multiplier (15), a subtractor (16), a first absolute value function (17), a second absolute value function (18), a unit state correction module (19), a main steam pressure deviation change direction correction module (20), and a main steam pressure deviation time over-limit correction module (21); fuel The following modules are defined as follows: boiler main control proportional coefficient correction function module f(x1) corresponding to calorific value; boiler main control proportional coefficient basic quantity function module f(x2) corresponding to unit load; boiler main control integral coefficient basic quantity function module f(x3) corresponding to unit load; boiler main control proportional coefficient correction function module f(x4) corresponding to main steam pressure deviation; boiler main control integral coefficient correction function module f(x5) corresponding to main steam pressure deviation; boiler main control proportional coefficient correction function module f(x6) corresponding to main steam pressure deviation differential; first-order filter module f(t1); and second-order filter module f(t2).

[0046] The output of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value is connected to the first input of the first multiplier (10). The output of the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load is connected to the second input of the first multiplier (10). The output of the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation is connected to the third input of the first multiplier (10). The output of the first multiplier (10) is connected to the first input of the second multiplier (11). The second input of the second multiplier (11) is connected to the output of the unit state correction module (19). The output of the second multiplier (11) is connected to the first input of the third multiplier (12). The second input of the third multiplier (12) is connected to the output of the boiler main control proportional coefficient correction function module f(x6) corresponding to the main steam pressure deviation differential. The boiler main control proportional coefficient corresponding to the main steam pressure deviation differential... The input of the correction function module f(x6) is connected to the output of the second first-order filter module f(t2), the input of the second first-order filter module f(t2) is connected to the output of the first absolute value function (17), the input of the first absolute value function (17) is connected to the output of the subtractor (16), and the first input of the subtractor (16) is connected to the output of the first first-order filter module f(t1). The input of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value is input, the input of the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load is input, the input of the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation is input, the second input of the subtractor (16) and the input of the first first-order filter module f(t1) are both input to the main steam pressure deviation, and the output of the third multiplier (12) outputs the corrected boiler main control proportional coefficient.

[0047] The output of the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load is connected to the first input of the fourth multiplier (13). The output of the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation is connected to the second input of the fourth multiplier (13). The output of the fourth multiplier (13) is connected to the first input of the fifth multiplier (14). The second input of the fifth multiplier (14) is connected to the output of the main steam pressure deviation change direction correction module (20). The input of the main steam pressure deviation change direction correction module (20) is connected to the output of the sixth multiplier (15). The first input of the sixth multiplier (15) is connected to the subtractor (1... The output of the second absolute value function (18) is connected to the input of the main steam pressure deviation time over-limit correction module (21), and the output of the main steam pressure deviation time over-limit correction module (21) is connected to the third input of the fifth multiplier (14). The unit load is input to the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load. The main steam pressure deviation is input to the main steam pressure deviation of the boiler main control integral coefficient correction function module f(x5), the second input of the sixth multiplier (15), and the input of the second absolute value function (18). The corrected boiler main control integral coefficient is output to the output of the fifth multiplier (14).

[0048] like Figure 2 As shown, the unit status correction module (19) includes: a first delay-on module (191), a first delay-off module (192), and a first selection module (193); the output terminal of the first delay-on module (191) is connected to the input terminal of the first delay-off module (192), the output terminal of the first delay-off module (192) is connected to the first input terminal of the first selection module (193), and the output terminal of the first selection module (193) is connected to the second input terminal of the second multiplier (11); the unit status is input at the input terminal of the first delay-on module (191), and the second and third input terminals of the first selection module (193) are respectively input to the variable load state correction constant A1 and the stable state correction constant A2. The first selection module (193) selects the variable load state correction constant A1 or the stable state correction constant A2 according to the signal input at its first input terminal and then outputs it.

[0049] like Figure 3As shown, the main steam pressure deviation change direction correction module (20) includes: a low threshold module (201), a second delay-on module (202), a second delay-off module (203), and a second selection module (204); the input terminal of the low threshold module (201) is connected to the output terminal of the sixth multiplier (15), the output terminal of the low threshold module (201) is connected to the input terminal of the second delay-on module (202), the output terminal of the second delay-on module (202) is connected to the input terminal of the second delay-off module (203), the output terminal of the second delay-off module (203) is connected to the first input terminal of the second selection module (204), and the output terminal of the second selection module (204) is connected to the second input terminal of the fifth multiplier (14); the second and third input terminals of the second selection module (204) correspond to the boiler main control integral time correction constants A3 and A4 corresponding to the differential of the main steam pressure deviation, respectively, and the second selection module (204) selects to output A3 or A4 according to the signal input at its first input terminal.

[0050] like Figure 4 As shown, the main steam pressure deviation time over-limit correction module (21) includes: a high limit threshold module (211), a third delay-through module (212), an SR trigger (213), a fourth delay-through module (214), a pulse generator (215), and a third selection module (216); the input terminal of the high limit threshold module (211) is connected to the output terminal of the second absolute value function (18), the output terminal of the high limit threshold module (211) is connected to the input terminal of the third delay-through module (212), the output terminal of the third delay-through module (212) is connected to the S port of the SR trigger (213), and the output terminal of the SR trigger (213) is connected to the fourth delay-through module (214). The input terminal of block (214) is connected to the input terminal of pulse generator (215). The output terminal of the fourth delay module (214) is connected to the R port of SR trigger (213). The output terminal of pulse generator (215) is connected to the first input terminal of third selection module (216). The output terminal of third selection module (216) is connected to the third input terminal of fifth multiplier (14). The second and third input terminals of third selection module (216) are respectively input to the boiler main control integral time correction constants A5 and A6 set according to the magnitude and duration of the deviation of main steam pressure from the target value. Third selection module (216) selects to output A5 or A6 according to the signal input at its first input terminal.

[0051] When the input value in the high threshold module (211) is greater than the set threshold H, the output is "1"; otherwise, it is "0". When the input value in the low threshold module (201) is less than the set threshold L, the output is "1"; otherwise, it is "0".

[0052] In the SR flip-flop (213), the S port is for setting and the R port is for resetting.

[0053] If the delay time of the first delay module (191), the second delay module (202), the third delay module (212) and the fourth delay module (214) is set to T, then when the input of the delay module changes from 0 to 1, its output will change to 1 after a delay of T seconds.

[0054] If the delay time of the first delay interrupt module (192) and the second delay interrupt module (203) is T, then when the input of the delay interrupt module changes from 1 to 0, its output will change to 0 after a delay of T seconds.

[0055] The judgment conditions of the first selection module (193), the second selection module (204), and the third selection module (216) are as follows: when the signal input at the first input terminal is "1", the parameter input at the second input terminal is selected for output; when the signal input at the first input terminal is "0", the parameter input at the third input terminal is selected for output.

[0056] The pulse generator (215) sets the speed control time Tp, T-on3 is the threshold for the duration of the main steam pressure deviating from the target value, and T-on4 is the time to restart the speed control function based on the boiler combustion reaction lag time. If the main steam pressure deviation always exceeds the set threshold within the T-on4 time, the speed control will be restarted.

[0057] f(x1), f(x2), f(x3), f(x4), f(x5), f(x6), f(t1), and f(t2) are all pre-defined multi-segment linear functions, one of which is a linear function with the relationship y. b =x b *(y c -y a ) / (x c -x a ), x b For the input value, y b The output value corresponding to the input value, x a Let y be the x-coordinate of a point adjacent to the input value. a The y-coordinate of the point adjacent to the input value, x c Let y be the x-coordinate of another point adjacent to the input value. c The ordinate of the point adjacent to the input value.

[0058] 1. Correct the proportional coefficient Kp2 of the PID control link for the main steam pressure deviation.

[0059] The output signals of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value, the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load, and the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation are simultaneously input into the first multiplier (10) for multiplication to obtain the output signal u1. The signal u1 and the output signal u2 of the unit status correction module (19) are simultaneously input into the second multiplier (11) for multiplication to obtain the output signal u3.

[0060] The main steam pressure deviation and the main steam pressure deviation filtered by the first first-order filter module f(t1) are simultaneously input into the subtractor (16) for subtraction calculation to obtain the output signal u4. The signal u4 is then subjected to the absolute value of the first absolute value function (17), and then filtered by the second first-order filter module f(t2) before being input to the boiler main control proportional coefficient correction function module f(x6) corresponding to the differential of the main steam pressure deviation, thereby obtaining the output signal u5.

[0061] Signals u3 and u5 are simultaneously input into the third multiplier (12) to obtain the corrected boiler main control proportional coefficient Kp2.

[0062] The function of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value is as follows: Thermal power units generate heat by burning coal to heat the medium and do work. Theoretically, the work capacity is directly proportional to the fuel calorific value, that is, the higher the calorific value, the more work is done per unit of coal. Thermal power units achieve unit load regulation by controlling the amount of fuel. Therefore, by correcting the control effect through changes in fuel calorific value, the control parameters can be controlled more accurately for fuel.

[0063] The function of the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation is: the main steam pressure deviation reflects the degree of matching between fuel quantity and unit load, that is, the coal quantity deviation can be calculated through the main steam pressure deviation.

[0064] The function of the unit status correction module (19) is: In the existing control strategy, the coal feedforward will be set according to the magnitude of the load change during the load change process. Due to the lag of coal combustion, the main steam pressure and other parameters of the unit will be delayed. Therefore, the actual coal has increased during the dynamic process. It is only because the combustion is slow that instantaneous pressure deviation occurs. At this time, there is no need to improve the function of pressure PID.

[0065] The function of the boiler main control proportional coefficient correction function module f(x6) corresponding to the main steam pressure deviation differential is: the main steam pressure deviation differential reflects the direction of change of the main steam pressure deviation. Although the pressure deviation exists, it tends to decrease. The strength of the effect of increasing or decreasing the amount of coal is adjusted through this indicator.

[0066] 2. Correct the integral coefficient Ti2 of the PID control link for the main steam pressure deviation.

[0067] The output signals of the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load and the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation are simultaneously input into the fourth multiplier (13) for multiplication to obtain the output signal u6;

[0068] After the main steam pressure deviation and signal u4 are simultaneously input to the sixth multiplier (15), the signal u7 is output after being corrected by the main steam pressure deviation change direction correction module (20).

[0069] After the main steam pressure deviation is taken by the second absolute value function (18), it is then corrected by the main steam pressure deviation time over-limit correction module (21) and output signal u8.

[0070] Signals u6, u7 and u8 are simultaneously input into the fifth multiplier (14) to obtain the corrected integral coefficient Ti2 of the boiler main control PID.

[0071] The function of the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation is as follows: Thermal power units generate heat by burning coal to heat the medium and do work. Theoretically, the work capacity is directly proportional to the calorific value of the fuel. That is, the higher the calorific value, the more work is done per unit of coal. Thermal power units achieve unit load regulation by controlling the amount of fuel. Therefore, by correcting the control action through changes in calorific value, that is, proportional and integral parameters, the fuel can be controlled more accurately.

[0072] The function of the main steam pressure deviation change direction correction module (20) is: the main steam pressure deviation differential reflects the change direction of the main steam pressure deviation. Although the pressure deviation exists, it is developing in the direction of reducing the deviation. The strength of the effect of increasing or decreasing the amount of coal can be adjusted through this indicator.

[0073] The function of the main steam pressure deviation time over-limit correction module (21) is: the main steam pressure deviation differential reflects the direction of change of the main steam pressure deviation. Since coal combustion is delayed and the pressure changes slowly, the main steam pressure deviation exceeding a certain value and maintaining it for a certain period of time is regarded as the coal quantity deviating from the demand value.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A main control speed change control system for a supercritical unit boiler, characterized in that, The proportional and integral coefficients of the PID control loop used to correct the main steam pressure deviation include: a first multiplier (10), a second multiplier (11), a third multiplier (12), a fourth multiplier (13), a fifth multiplier (14), a sixth multiplier (15), a subtractor (16), a first absolute value function (17), a second absolute value function (18), a unit status correction module (19), a main steam pressure deviation change direction correction module (20), and a main steam pressure deviation time over-limit correction module (21); the boiler main control ratio corresponding to the fuel calorific value. Example: Boiler main control proportional coefficient correction function module f(x1), boiler main control integral coefficient basic quantity function module f(x2) corresponding to unit load, boiler main control integral coefficient basic quantity function module f(x3) corresponding to unit load, boiler main control proportional coefficient correction function module f(x4) corresponding to main steam pressure deviation, boiler main control integral coefficient correction function module f(x5) corresponding to main steam pressure deviation, boiler main control proportional coefficient correction function module f(x6) corresponding to main steam pressure deviation derivative; first-order filter module f(t1), second-order filter module f(t2); The output of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value is connected to the first input of the first multiplier (10). The output of the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load is connected to the second input of the first multiplier (10). The output of the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation is connected to the third input of the first multiplier (10). The output of the first multiplier (10) is connected to the first input of the second multiplier (11). The second input of the second multiplier (11) is connected to the output of the unit state correction module (19). The output of the second multiplier (11) is connected to the first input of the third multiplier (12). The second input of the third multiplier (12) is connected to the output of the boiler main control proportional coefficient correction function module f(x6) corresponding to the main steam pressure deviation differential. The boiler main control proportional coefficient correction function module f(x6) corresponding to the main steam pressure deviation differential is connected to the output of the boiler main control proportional coefficient correction function module f(x6). The input of the coefficient correction function module f(x6) is connected to the output of the second first-order filter module f(t2), the input of the second first-order filter module f(t2) is connected to the output of the first absolute value function (17), the input of the first absolute value function (17) is connected to the output of the subtractor (16), and the first input of the subtractor (16) is connected to the output of the first first-order filter module f(t1). The input of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value is input, the input of the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load is input, the input of the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation is input, the second input of the subtractor (16) and the input of the first first-order filter module f(t1) are both input to the main steam pressure deviation, and the output of the third multiplier (12) outputs the corrected proportional coefficient. The output of the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load is connected to the first input of the fourth multiplier (13). The output of the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation is connected to the second input of the fourth multiplier (13). The output of the fourth multiplier (13) is connected to the first input of the fifth multiplier (14). The second input of the fifth multiplier (14) is connected to the output of the main steam pressure deviation change direction correction module (20). The input of the main steam pressure deviation change direction correction module (20) is connected to the output of the sixth multiplier (15). The first input of the sixth multiplier (15) is connected to the subtractor. The output of (16) is connected, the output of the second absolute value function (18) is connected to the input of the main steam pressure deviation time over-limit correction module (21), and the output of the main steam pressure deviation time over-limit correction module (21) is connected to the third input of the fifth multiplier (14). The unit load is input to the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load. The main steam pressure deviation is input to the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation, the second input of the sixth multiplier (15), and the input of the second absolute value function (18). The corrected integral coefficient is output to the output of the fifth multiplier (14).

2. The supercritical unit boiler main control speed control system according to claim 1, characterized in that, The unit status correction module (19) includes: a first delay-on module (191), a first delay-off module (192), and a first selection module (193); the output terminal of the first delay-on module (191) is connected to the input terminal of the first delay-off module (192), the output terminal of the first delay-off module (192) is connected to the first input terminal of the first selection module (193), and the output terminal of the first selection module (193) is connected to the second input terminal of the second multiplier (11); the unit status is input at the input terminal of the first delay-on module (191), and the second and third input terminals of the first selection module (193) are respectively input to the variable load state correction constant A1 and the stable state correction constant A2. The first selection module (193) selects the variable load state correction constant A1 or the stable state correction constant A2 according to the signal input at its first input terminal and then outputs it.

3. The supercritical unit boiler main control speed change control system according to claim 2, characterized in that, The main steam pressure deviation change direction correction module (20) includes: a low threshold module (201), a second delay-on module (202), a second delay-off module (203), and a second selection module (204); the input terminal of the low threshold module (201) is connected to the output terminal of the sixth multiplier (15), the output terminal of the low threshold module (201) is connected to the input terminal of the second delay-on module (202), the output terminal of the second delay-on module (202) is connected to the input terminal of the second delay-off module (203), the output terminal of the second delay-off module (203) is connected to the first input terminal of the second selection module (204), and the output terminal of the second selection module (204) is connected to the second input terminal of the fifth multiplier (14); the second and third input terminals of the second selection module (204) correspond to the boiler main control integral time correction constants A3 and A4 corresponding to the differential of the main steam pressure deviation, respectively, and the second selection module (204) selects to output A3 or A4 according to the signal input at its first input terminal.

4. The supercritical unit boiler main control speed control system according to claim 3, characterized in that, The main steam pressure deviation time over-limit correction module (21) includes: a high limit threshold module (211), a third delay-through module (212), an SR trigger (213), a fourth delay-through module (214), a pulse generator (215), and a third selection module (216); the input terminal of the high limit threshold module (211) is connected to the output terminal of the second absolute value function (18), the output terminal of the high limit threshold module (211) is connected to the input terminal of the third delay-through module (212), the output terminal of the third delay-through module (212) is connected to the S port of the SR trigger (213), and the output terminal of the SR trigger (213) is connected to the fourth delay-through module (214). The input terminal of the fourth delay module (214) is connected to the input terminal of the pulse generator (215). The output terminal of the fourth delay module (214) is connected to the R port of the SR trigger (213). The output terminal of the pulse generator (215) is connected to the first input terminal of the third selection module (216). The output terminal of the third selection module (216) is connected to the third input terminal of the fifth multiplier (14). The second and third input terminals of the third selection module (216) are respectively input to the boiler main control integral time correction constants A5 and A6 set according to the magnitude and duration of the deviation of the main steam pressure from the target value. The third selection module (216) selects to output A5 or A6 according to the signal input at its first input terminal.

5. A control method applied to the main control speed control system of a supercritical unit boiler as described in any one of claims 1-4, characterized in that, include: The proportional coefficient of the PID control link for the main steam pressure deviation is corrected; The integral coefficient of the PID control loop for the main steam pressure deviation is corrected.

6. The control method according to claim 5, characterized in that, The method for correcting the proportional coefficient of the PID control link for the main steam pressure deviation is as follows: The output signals of the boiler main control proportional coefficient correction function module f(x1) corresponding to the fuel calorific value, the boiler main control proportional coefficient basic quantity function module f(x2) corresponding to the unit load, and the boiler main control proportional coefficient correction function module f(x4) corresponding to the main steam pressure deviation are simultaneously input into the first multiplier (10) for multiplication to obtain the output signal u1. The signal u1 and the output signal u2 of the unit status correction module (19) are simultaneously input into the second multiplier (11) for multiplication to obtain the output signal u3. The main steam pressure deviation and the main steam pressure deviation filtered by the first first-order filter module f(t1) are simultaneously input into the subtractor (16) for subtraction calculation to obtain the output signal u4. The signal u4 is then subjected to the absolute value of the first absolute value function (17), and then filtered by the second first-order filter module f(t2) before being input to the boiler main control proportional coefficient correction function module f(x6) corresponding to the differential of the main steam pressure deviation, thereby obtaining the output signal u5. Signals u3 and u5 are simultaneously input into the third multiplier (12) to obtain the corrected proportional coefficient.

7. The control method according to claim 5, characterized in that, The method for correcting the integral coefficient of the PID control link for the main steam pressure deviation is as follows: The output signals of the boiler main control integral coefficient basic quantity function module f(x3) corresponding to the unit load and the boiler main control integral coefficient correction function module f(x5) corresponding to the main steam pressure deviation are simultaneously input into the fourth multiplier (13) for multiplication to obtain the output signal u6; After the main steam pressure deviation and signal u4 are simultaneously input to the sixth multiplier (15), the signal u7 is output after being corrected by the main steam pressure deviation change direction correction module (20). After the main steam pressure deviation is taken by the second absolute value function (18), it is then corrected by the main steam pressure deviation time over-limit correction module (21) and output signal u8. Signals u6, u7 and u8 are simultaneously input into the fifth multiplier (14) to obtain the corrected integral coefficients.

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