Feedforward control method for coal-fired units

Abstract

The present invention discloses a feedforward control method for a coal-fired unit. When the coal-fired unit enters the heat storage condition, the following steps are included: obtaining a first control signal according to a first unit load command; inputting the measured value of the first main steam pressure and the set value of the first main steam pressure into a PID controller and then outputting a second control signal; obtaining the maximum coal feeding amount u of the heat storage condition x , and calculating to obtain a first static coal feeding amount u1 and a first dynamic coal feeding amount u2, where u1 = f1(u x ), u2 = u x (1 - 1 / (T1s + 1)); obtaining a third control signal according to the first static coal feeding amount u1 and the first dynamic coal feeding amount u2; outputting the sum of the three control signals to the boiler main control to adjust the coal feeding amount to control the main steam pressure. The present invention adds a coal feeding amount feedforward signal to the traditional control method. When the coal-fired unit enters the heat storage condition, the coal feeding amount can act faster or in advance, the energy of the boiler is quickly supplemented, the main steam pressure and the like are maintained stable, and the operation stability of the unit is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of coal-fired unit control, and particularly to a feedforward control method for coal-fired units. Background Art

[0002] In recent years, the penetration rate of new energy sources such as wind power and solar energy in the power system has been continuously increasing. However, the randomness and intermittency of new energy power generation are significantly different from those of traditional synchronous generators, posing a great threat to the stability and security of the power system frequency. At the same time, the capacity ratio of conventional units such as thermal power units has gradually decreased, resulting in a weakened system peak shaving and frequency modulation ability. Under this background, it is urgent for coal-fired units in China to improve their own operation flexibility to support the consumption of a high proportion of new energy and maintain the safe and stable operation of the power system.

[0003] Installing a molten salt energy storage system is an important technical means proposed in recent years to achieve the rapid load change and deep peak shaving operation capabilities of coal-fired units. However, when using flue gas to heat molten salt for energy storage, a large amount of flue gas flow needs to be extracted, and part of the heat of the boiler enters the heat exchanger for heating, resulting in a reduction in the heat originally used to heat water and steam, causing the main steam pressure of the unit to start to slowly decline, and then causing the unit load to start to decline. To maintain the stability of the main steam pressure of the unit, currently, the boiler operation generally uses a conventional coal feeding amount control based on the deviation of the main steam pressure. However, the loop from the coal feeding amount of the unit to the main steam pressure is a large-delay and large-inertia link, which requires a long reaction time and is often difficult to obtain satisfactory control quality. At the same time, due to the relatively small adjustment parameters of the boiler main control PID controller, the feedback correction of the coal feeding amount is too slow and there are fluctuations, resulting in a large degree of fluctuation of the main steam pressure of the unit under the current control mode, which is not conducive to the stable and safe operation of the unit. Summary of the Invention

[0004] The purpose of the present invention is to provide a feedforward control method for coal-fired units, at least during the flue gas energy storage process, the coal feeding amount of the boiler can be accelerated or advanced, and the boiler energy can be quickly replenished, thereby reducing the fluctuations of main parameters such as the main steam pressure and improving the operation stability of the unit.

[0005] To solve the above technical problems, the present invention provides a feedforward control method for coal-fired units. When the coal-fired unit enters the energy storage working condition, the method includes the following steps:

[0006] Calculate a first control signal according to the first unit load command;

[0007] Obtain the measured value and the set value of the first main steam pressure, and input the measured value and the set value of the first main steam pressure into a first PID controller to output a second control signal;

[0008] Obtain the maximum coal feeding rate u under the heat storage condition x , and calculate the first static coal feeding rate u1 and the first dynamic coal feeding rate u2 according to the maximum coal feeding rate u x , and obtain the third control signal according to the first static coal feeding rate u1 and the first dynamic coal feeding rate u2;

[0009] Output the sum of the first control signal, the second control signal and the third control signal to the boiler master PID controller, and adjust the coal feeding rate according to the output of the boiler master PID controller to control the main steam pressure.

[0010] The present invention provides a feedforward control method for a coal-fired unit. On the basis of the traditional coal feeding rate control based on the main steam pressure deviation signal, an additional coal feeding rate feedforward signal is added. Specifically, the maximum coal feeding rate u under the heat storage condition is obtained x , and the first static coal feeding rate u1 and the first dynamic coal feeding rate u2 are calculated according to the maximum coal feeding rate u x , and then the third control signal, that is, the coal feeding rate feedforward signal, is obtained according to the first static coal feeding rate u1 and the first dynamic coal feeding rate u2. In this way, by adding this coal feeding rate feedforward signal, when the coal-fired unit enters the heat storage condition, the boiler coal feeding rate can act faster or earlier, so that the boiler energy can be quickly supplemented, avoiding the hysteresis and oscillation of the main steam pressure large delay link regulation, maintaining the stability of the main parameters such as the main steam pressure of the coal-fired unit, and improving the operation stability of the unit.

[0011] Optionally, the first static coal feeding rate u1 is calculated as: u1 = f1(u x ), where f1 is a ramp function with a starting point of 0, an ending point of u x , and a slope of p;

[0012] The first dynamic coal feeding rate u2 is calculated as: u2 = u x (1 - 1 / (T1s + 1)), where T1 is the time inertia constant and s is the Laplace operator.

[0013] Optionally, obtaining the maximum coal feeding rate u x includes the following steps:

[0014] Obtain the current unit load N when the coal-fired unit enters the heat storage condition x , and calculate the maximum flue gas extraction amount D when the coal-fired unit enters the heat storage condition according to the current unit load N x : D x = f2(N x ) x ;

[0015] The maximum coal feeding rate u x is calculated as: ux =D x / k0, where k0 is a conversion coefficient.

[0016] Optionally, obtaining the conversion coefficient k0 includes the following steps:

[0017] Obtain the average flue gas flow rate Q0 and the average coal feed rate u0 when the unit load is in a stable state under non-thermal energy storage conditions, and calculate the conversion coefficient k0: k0 = Q0 / u0.

[0018] Optionally, the judgment condition for determining that the unit load is in a stable state is: ;

[0019] In the formula:

[0020] N—the unit load;

[0021] n—the data length.

[0022] Optionally, the average flue gas flow rate Q0 is calculated as: ; the average coal feed rate u0 is calculated as: ;

[0023] In the formula:

[0024] Q—the flue gas flow rate of the unit;

[0025] u—the coal feed rate of the unit.

[0026] Optionally, calculating the third control signal according to the first static coal feed rate u1 and the first dynamic coal feed rate u2 specifically includes the following steps:

[0027] Calculate the sum of the first static coal feed rate u1 and the first dynamic coal feed rate u2. If the sum of the first static coal feed rate u1 and the first dynamic coal feed rate u2 is lower than the safety amplitude, the sum of the first static coal feed rate u1 and the first dynamic coal feed rate u2 is the third control signal;

[0028] If the sum of the first static coal feed rate u1 and the first dynamic coal feed rate u2 is higher than the safety amplitude, the safety amplitude is the third control signal.

[0029] Optionally, when the coal-fired unit enters the thermal energy storage condition, it further includes the following steps:

[0030] Obtain the set value of the first superheater outlet temperature and the measured value of the first superheater outlet temperature, and input the set value of the first superheater outlet temperature and the measured value of the first superheater outlet temperature into the second PID controller to output the set value of the first desuperheated water outlet temperature;

[0031] Obtain the measured value of the first desuperheated water outlet temperature, and input the set value of the first desuperheated water outlet temperature and the measured value of the first desuperheated water outlet temperature into the third PID controller, and then output a fourth control signal;

[0032] Output the sum of the fourth control signal and the fifth control signal to the desuperheated water valve PID controller, and adjust the opening of the desuperheated water valve according to the output of the desuperheated water valve PID controller;

[0033] The fifth control signal is -u z (1 / (T2s + 1) 3 ), where T2 is the time inertia constant and s is the Laplace operator.

[0034] Optionally, when the coal-fired unit exits the heat storage condition, the following steps are further included:

[0035] Calculate a sixth control signal according to the second unit load command;

[0036] Obtain the measured value of the second main steam pressure and the set value of the second main steam pressure, and input the measured value of the second main steam pressure and the set value of the second main steam pressure into the first PID controller, and then output a seventh control signal;

[0037] According to the maximum coal feeding amount u x Calculate a second static coal feeding amount u1' and a second dynamic coal feeding amount u2', and calculate an eighth control signal according to the second static coal feeding amount u1' and the second dynamic coal feeding amount u2';

[0038] Output the sum of the sixth control signal, the seventh control signal and the eighth control signal to the boiler master PID controller, and adjust the coal feeding amount according to the output of the boiler master PID controller to control the main steam pressure.

[0039] Optionally, the second static coal feeding amount u1' is calculated as: u1' = f3(u x ), where f1 is a ramp function with u x as the starting point, 0 as the ending point, and a slope of -p;

[0040] The second dynamic coal feeding amount u2' is calculated as: u2' = -u x (1 - 1 / (T1s + 1)), where T1 is the time inertia constant and s is the Laplace operator.

[0041] Optionally, when the coal-fired unit exits the heat storage condition, the following steps are further included:

[0042] Obtain the set value of the second superheater outlet temperature and the measured value of the second superheater outlet temperature, and input the set value of the second superheater outlet temperature and the measured value of the second superheater outlet temperature into the second PID controller, and then output the set value of the second desuperheated water outlet temperature;

[0043] Obtain the measured value of the second desuperheated water outlet temperature, and input the set value of the second desuperheated water outlet temperature and the measured value of the second desuperheated water outlet temperature into the third PID controller, and then output the ninth control signal;

[0044] Output the sum of the ninth control signal and the tenth control signal to the desuperheated water valve PID controller, and adjust the opening of the desuperheated water valve according to the output of the desuperheated water valve PID controller;

[0045] The tenth control signal is u z (1 / (T2s + 1) 3 ), where T2 is the time inertia constant and s is the Laplace operator. Description of the Drawings

[0046] Figure 1 It is the logic control diagram of the boiler master in the feedforward control method for a coal-fired unit provided by the present invention;

[0047] Figure 2 It is the logic control diagram of the desuperheated water valve in the feedforward control method for a coal-fired unit provided by the present invention;

[0048] Figure 3 It is the device diagram for implementing the feedforward control method for a coal-fired unit provided by the present invention;

[0049] Among them, Figures 1 - 3 The description of the reference numerals in

[0050] 1 - First PID controller; 2 - Second PID controller; 3 - Third PID controller; 4 - Analog quantity generator; 5 - Selection function module; 6 - Subtractor; 7 - Limiting module; 8 - Adder;

[0051] 01 - Intelligent computing server; 02 - DCS system. Detailed Embodiment

[0052] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0053] Please refer to Figures 1 - 3 , Figure 1 It is the logic control diagram of the boiler master in the feedforward control method for a coal-fired unit provided by the present invention; Figure 2 It is the logic control diagram of the desuperheated water valve in the feedforward control method for a coal-fired unit provided by the present invention;Figure 3 It is a device diagram for implementing the feedforward control method of a coal-fired unit provided by the present invention.

[0054] The present invention provides a feedforward control method for a coal-fired unit. When the coal-fired unit enters the heat storage condition, the following steps are included:

[0055] Calculate a first control signal according to the first unit load command;

[0056] Obtain the measured value and the set value of the first main steam pressure, and input the measured value and the set value of the first main steam pressure into a first PID controller (Proportional-Integral-Derivative controller) 1 and then output a second control signal;

[0057] Obtain the maximum coal feeding amount u under the heat storage condition x , and calculate a first static coal feeding amount u1 and a first dynamic coal feeding amount u2 according to the maximum coal feeding amount u x , and calculate a third control signal according to the first static coal feeding amount u1 and the first dynamic coal feeding amount u2;

[0058] Output the sum of the first control signal, the second control signal and the third control signal to the boiler master PID controller, and adjust the coal feeding amount according to the output of the boiler master PID controller to control the main steam pressure.

[0059] The present invention provides a feedforward control method for a coal-fired unit. On the basis of the traditional coal feeding amount control based on the main steam pressure deviation signal, an additional coal feeding amount feedforward signal is added. Specifically, obtain the maximum coal feeding amount u under the heat storage condition x , and calculate a first static coal feeding amount u1 and a first dynamic coal feeding amount u2 according to the maximum coal feeding amount u x , and then obtain a third control signal according to the first static coal feeding amount u1 and the first dynamic coal feeding amount u2, that is, the coal feeding amount feedforward signal. In this way, by adding this coal feeding amount feedforward signal, when the coal-fired unit enters the heat storage condition, the coal feeding amount of the boiler can act faster or in advance, so that the energy of the boiler can be quickly supplemented, avoiding the hysteresis and oscillation of the large time-delay link regulation of the main steam pressure, maintaining the stability of the main parameters such as the main steam pressure of the coal-fired unit, and improving the operation stability of the unit.

[0060] Among them, the first control signal is calculated according to the first unit load command. Specifically, for the designed coal type, the boiler design specification usually gives a broken line function representing the corresponding relationship between the unit load and the coal feeding amount. When the unit load is determined, the required coal feeding amount can be obtained through this broken line function. In practice, when the coal type changes, the broken line function needs to be adjusted to ensure the accuracy of the coal feeding amount.

[0061] Among them, the first main steam pressure set value is related to the first unit load command. When the unit load command is determined, the main steam pressure set value can be calculated from the unit load command through a corresponding relationship function, which is usually given by the manufacturer's design.

[0062] Among them, the measured value of the first main steam pressure can be obtained through tests using a pressure sensor or the like.

[0063] Further, the first static coal feeding amount u1 is calculated as: u1 = f1(u x ), where f1 is a ramp function starting from 0, ending at u x and having a slope of p. The static coal feeding amount remains unchanged when it increases to u x .

[0064] The first dynamic coal feeding amount u2 is calculated as: u2 = u x (1 - 1 / (T1s + 1)), where T1 is the time inertia constant and s is the Laplace operator.

[0065] Among them, the slope p of the ramp function is a parameter to be determined and can be obtained through debugging; the time inertia constant T1 can be obtained through debugging.

[0066] Further, obtaining the maximum coal feeding amount u x includes the following steps:

[0067] Obtain the current unit load N of the coal-fired unit when it enters the heat storage condition x , and calculate the maximum flue gas extraction amount D of the coal-fired unit when it enters the heat storage condition according to the current unit load N x : D x = f2(N x ); x

[0068] The maximum coal feeding amount u x is calculated as: u x = D x / k0, where k0 is the conversion coefficient.

[0069] Among them, f2 is the relationship function between the maximum flue gas extraction amount D x and the unit load, which is usually given by the manufacturer during design. When the operator selects to turn on the heat storage condition, obtain the current unit load N x , and the maximum flue gas extraction amount D x can be obtained through the corresponding relationship function f2. The maximum coal feeding amount u x is obtained by dividing the maximum flue gas extraction amount D x by the conversion coefficient k0, and its function is to perform coal quality correction to ensure the accuracy of the coal feeding feedforward amount.

[0070] In practice, the conversion coefficient k0 is related to the coal quality. When the coal quality changes, the conversion coefficient k0 needs to be updated.

[0071] Furthermore, obtaining the conversion coefficient k0 includes the following steps:

[0072] Obtain the average flue gas flow rate Q0 and the average coal feed rate u0 when the unit load is in a stable state under non-heat storage conditions, and calculate the conversion coefficient k0: k0 = Q0 / u0.

[0073] In this way, the conversion coefficient k0 is calculated based on the average flue gas flow rate Q0 and the average coal feed rate u0 when the unit load is in a stable state, and the calculation result is more accurate.

[0074] Among them, the judgment condition for determining that the unit load is in a stable state is: ;

[0075] In the formula:

[0076] N—the unit load;

[0077] n—the data length, with a default maximum of 1800, representing 1800 s.

[0078] It can be seen that in this judgment condition, each obtained unit load value is compared with the average unit load value to determine whether the unit load value deviates from the average value. If the unit load still meets the above judgment condition after obtaining 1800 data lengths, it is determined that the unit load has not fluctuated significantly during this time period, and it can be considered that the unit load is in a stable state.

[0079] Among them, the average flue gas flow rate Q0 is calculated as: ;

[0080] In the formula:

[0081] Q—the flue gas flow rate of the unit.

[0082] Among them, the average coal feed rate u0 is calculated as: ;

[0083] In the formula:

[0084] u—the coal feed rate of the unit.

[0085] In practice, if the unit load has multiple stable states, the conversion coefficient k0 is calculated from the average flue gas flow rate Q0 and the average coal feed rate u0 in the latest stable state, that is, k0 is updated to the latest value.

[0086] Please continue to refer to Figure 1 , obtaining the third control signal according to the first static coal feed rate u1 and the first dynamic coal feed rate u2 specifically includes the following steps:

[0087] Calculate the sum of the first static coal feeding amount u1 and the first dynamic coal feeding amount u2. If the sum of the first static coal feeding amount u1 and the first dynamic coal feeding amount u2 is lower than the safety amplitude value, then the sum of the first static coal feeding amount u1 and the first dynamic coal feeding amount u2 is the third control signal;

[0088] If the sum of the first static coal feeding amount u1 and the first dynamic coal feeding amount u2 is higher than the safety amplitude value, then the safety amplitude value is the third control signal.

[0089] Among them, the magnitude of the safety amplitude value is related to the power of the heat exchanger, and is usually given by the manufacturer's design value. By increasing the above safety amplitude value, the adjustment of the coal feeding amount can be adapted to the power of the heat exchanger, improving the operation safety of the unit.

[0090] Please refer to Figure 2 , Figure 2 which is the logic control diagram of the desuperheating water valve in the feedforward control method of the coal-fired unit provided by the present invention.

[0091] In the feedforward control method of the coal-fired unit of the present invention, when the coal-fired unit enters the heat storage working condition, the following steps are further included:

[0092] Obtain the set value of the temperature at the outlet of the first superheater and the measured value of the temperature at the outlet of the first superheater, and input the set value of the temperature at the outlet of the first superheater and the measured value of the temperature at the outlet of the first superheater into the second PID controller 2 and then output the set value of the temperature at the outlet of the first desuperheating water;

[0093] Obtain the measured value of the temperature at the outlet of the first desuperheating water, and input the set value of the temperature at the outlet of the first desuperheating water and the measured value of the temperature at the outlet of the first desuperheating water into the third PID controller 3 and then output the fourth control signal;

[0094] Output the sum of the fourth control signal and the fifth control signal to the desuperheating water valve PID controller, and adjust the opening of the desuperheating water valve according to the output of the desuperheating water valve PID controller;

[0095] The fifth control signal is -u z (1 / (T2s + 1) 3 ), where T2 is the inertia constant, which is determined by debugging.

[0096] During the operation of a coal-fired unit, in addition to maintaining the stability of the main steam pressure, it is also necessary to avoid large fluctuations in the main steam temperature. It can be understood that when the coal-fired unit enters the heat storage condition, a large amount of flue gas flow needs to be extracted, and part of the heat of the boiler enters the heat exchanger for heating, resulting in a reduction in the heat originally used to heat water and steam, and the temperature of the main steam will tend to decrease. Desuperheating water is used to reduce the temperature of the main steam. If the flow rate of the desuperheating water is too large, it will cause a significant drop in the temperature of the main steam, affecting the normal operation of the boiler. Therefore, when the coal-fired unit enters the heat storage condition, it is necessary to reduce the opening of the desuperheating water valve to avoid a large drop in the main steam temperature and ensure the normal operation of the boiler.

[0097] Traditional desuperheating water valve control realizes the control of the desuperheating water valve opening through the deviation of the superheater outlet temperature and the measured value of the desuperheating water outlet temperature, and then realizes the control of the main steam temperature. The reaction time is long, and the fluctuation degree of the main steam temperature is large, which is not conducive to the stable and safe operation of the unit. The feed-forward control method for the coal-fired unit of the present invention adds a feed-forward quantity -u z (1 / (T2s + 1) 3 ) to the basis of the traditional control method, where u z is the debugging setting value, and the default value can be selected as 10%. By adding this feed-forward quantity -u z (1 / (T2s + 1) 3 ), the opening of the desuperheating water valve can be quickly reduced, the injection of the desuperheating water flow can be reduced, the hysteresis and oscillation of the desuperheating water large dead-time link regulation can be avoided, the stability of the main steam temperature of the coal-fired unit can be maintained, and the operation stability of the unit can be improved.

[0098] Among them, the measured value of the first superheater outlet temperature and the measured value of the first desuperheating water outlet temperature can be obtained through temperature sensors.

[0099] Among them, the set value of the first superheater outlet temperature is related to the unit load. When the unit load command is determined, the set value of the first superheater outlet temperature can be calculated by the unit load command through the corresponding relationship function, and this relationship function is usually designed and given by the manufacturer.

[0100] Furthermore, the feed-forward control method for the coal-fired unit of the present invention, when the coal-fired unit exits the heat storage condition, includes the following steps:

[0101] Calculate the sixth control signal according to the second unit load command;

[0102] Obtain the measured value of the second main steam pressure and the set value of the second main steam pressure, and input the measured value of the second main steam pressure and the set value of the second main steam pressure into the first PID controller 1 and then output the seventh control signal;

[0103] According to the maximum coal feeding amount u xCalculate to obtain the second static coal feeding amount u1' and the second dynamic coal feeding amount u2', and calculate and obtain the eighth control signal according to the second static coal feeding amount u1' and the second dynamic coal feeding amount u2';

[0104] Output the sum of the sixth control signal, the seventh control signal and the eighth control signal to the boiler master PID controller, and adjust the coal feeding amount according to the output of the boiler master PID controller to control the main steam pressure.

[0105] With the above settings, the present invention provides a feedforward control method for a coal-fired unit. When exiting the heat storage condition, an additional coal feeding amount feedforward signal is also added to quickly reduce the coal feeding amount, avoid the rapid increase of the main steam pressure of the boiler, avoid the hysteresis and oscillation of the large dead-time link adjustment of the main steam pressure, and maintain the stability of the main steam pressure of the unit.

[0106] Similarly, the second main steam pressure set value is related to the second unit load command. When the unit load command is determined, the main steam pressure set value can be calculated from the unit load command through a corresponding relationship function, and this relationship function is usually designed and given by the manufacturer.

[0107] Among them, the second measured value of the main steam pressure can be obtained by testing with a pressure sensor or the like.

[0108] Further, the second static coal feeding amount u1' is calculated as: u1' = f3(u x ), where f3 is a ramp function with u x as the starting point, 0 as the ending point, and a slope of -p. When the static coal feeding amount is reduced to 0, it remains unchanged;

[0109] The first dynamic coal feeding amount u2' is calculated as: u2' = -u x (1 - 1 / (T1s + 1)).

[0110] Further, the feedforward control method for the coal-fired unit of the present invention further includes the following steps when the coal-fired unit exits the heat storage condition:

[0111] Obtain the second set value of the superheater outlet temperature and the second measured value of the superheater outlet temperature, and input the second set value of the superheater outlet temperature and the second measured value of the superheater outlet temperature into the second PID controller 2 and then output the second set value of the desuperheated water outlet temperature;

[0112] Obtain the second measured value of the desuperheated water outlet temperature, and input the second set value of the desuperheated water outlet temperature and the second measured value of the desuperheated water outlet temperature into the third PID controller 3 and then output the ninth control signal;

[0113] Output the sum of the ninth control signal and the tenth control signal to the desuperheated water valve PID controller, and adjust the opening of the desuperheated water valve according to the output of the desuperheated water valve PID controller;

[0114] The tenth control signal is u z (1 / (T2s + 1) 3 )

[0115] It can be understood that when the coal-fired unit exits the heat storage condition, the flue gas flow is no longer extracted outward, which increases the heat used to heat water and steam, and the temperature of the main steam will tend to rise. Therefore, it is necessary to increase the flow rate of desuperheating water to ensure the stability of the main steam temperature and maintain the normal operation of the boiler. Based on this, in the feedforward control method of the coal-fired unit of the present invention, when adjusting the main steam temperature, a feedforward quantity u z (1 / (T2s + 1) 3 ) is added on the basis of the traditional control method, which can quickly increase the opening of the desuperheating water valve and increase the injection of the desuperheating water flow rate, avoid the hysteresis and oscillation of the desuperheating water large-delay link adjustment, maintain the stability of the main steam temperature of the coal-fired unit, and improve the operation stability of the unit.

[0116] Among them, the set value of the second superheater outlet temperature is related to the unit load. When the unit load command is determined, the set value of the second superheater outlet temperature can be calculated from the unit load command through the corresponding relationship function, and this relationship function is usually designed and given by the manufacturer.

[0117] The logic control diagram of the boiler master control in the feedforward control method of the coal-fired unit of the present invention is as Figure 1 shown. The content in the dotted box is the generation logic of the feedforward signal of the coal feeding amount added by the present invention. Among them, from top to bottom, u x is the maximum coal feeding amount u that is calculated in real time in the intelligent computing server 01 and transmitted to the DCS system (Distributed Control System) 02 x . The value of A in the analog quantity generator 4 is 0. The two pass through the selection function module 5 and then output X1. The Y channel of the selection function module 5 is u x , the N channel is 0, and the logic judgment quantity is D. When D = 0, the coal-fired unit is in the non-heat storage condition, and X1 is equal to the value of the N channel. When D = 1, the coal-fired unit is in the heat storage condition, and X1 is equal to the value of the Y channel.

[0118] X1 becomes X2 through the rate limit algorithm, which is the static coal feeding amount in the above description.

[0119] X1 becomes X1 / (T1s + 1) after passing through the lead / lag link, and becomes X3 after passing through the subtractor 6. X3 = X1(1 - 1 / (T1s + 1)), which is the dynamic coal feeding amount in the above description.

[0120] X2 and X3 are added together and passed through the limiter module 7 before being superimposed on the adder 8 to form the control instruction of the boiler master control.

[0121] The logic control diagram of the desuperheating water valve in the feedforward control method of the coal-fired unit of the present invention is as follows: Figure 2 As shown, the content in the dotted box is the generation logic of the feedforward amount added by the present invention, wherein, from top to bottom, u z The value of A in the analog generator 4 is 0. Both are output through the selection function module 5. The Y channel of the selection function module 5 is u. z , N channel is 0, the logic judgment value is D, which means that when D=0, the coal-fired unit is in a non-heat storage condition, and the numerical output of the N channel is; when D is equal to 1, the coal-fired unit is in a heat storage condition, and the numerical output of the Y channel is.

[0122] The output of the selection function module 5 is added to the adder 8 after passing through three leading / lagging links to form a control instruction for the desuperheating water valve.

[0123] The above-mentioned logic control of the boiler master control and the logic control of the desuperheating water valve are implemented in the DCS system.

[0124] In addition, in order to implement the feedforward control method of the coal-fired unit of the present invention, it is necessary to add a functional module in the intelligent computing server 01, wherein the functional module should have at least the following functions: data communication with the DCS system, real-time data analysis function, steady-state flue gas volume / coal feed amount calculation, coal quality correction coefficient calculation, maximum flue gas volume calculation and maximum coal feed amount calculation, etc. Specifically:

[0125] The data communication with the DCS system requires time t, unit load N, unit flue gas flow Q, unit coal supply u, switch signal D indicating whether it is in heat storage condition (D=1 in heat storage condition, D=0 in non-heat storage condition, when the operator chooses to turn on the heat storage condition, D changes from 0 to 1, when the operator chooses to turn off the heat storage condition, D changes from 1 to 0), conversion coefficient k0 and maximum coal supply u in heat storage condition x Real-time transmission of equal data volume;

[0126] The real-time data analysis function requires the analysis of steady-state data volume and data extraction.

[0127] The calculation rules for each key data quantity are given in the calculation of steady-state flue gas volume / coal supply, the calculation of coal quality correction coefficient, the calculation of maximum flue gas volume and the calculation of maximum coal supply.

[0128] The above has introduced in detail a feedforward control method for a coal-fired unit provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A feedforward control method for a coal-fired unit, characterized in that: When a coal-fired unit enters the heat storage state, the following steps are included: Calculate and obtain a first control signal according to the load instruction of the first unit; Obtaining a first main steam pressure measured value and a first main steam pressure set value, inputting the first main steam pressure measured value and the first main steam pressure set value into a first PID controller and then outputting a second control signal; Get the maximum coal supply u for heat storage conditions x , according to the maximum coal feed amount u x Calculate and obtain a first static coal feeding amount u1 and a first dynamic coal feeding amount u2, and calculate and obtain a third control signal according to the first static coal feeding amount u1 and the first dynamic coal feeding amount u2; The sum of the first control signal, the second control signal and the third control signal is output to the boiler main control PID controller, and the coal feed amount is adjusted according to the output of the boiler main control PID controller to control the main steam pressure.

2. The feedforward control method for a coal-fired unit according to claim 1, characterized in that: The first static coal feeding amount u1 is calculated as: u1=f1(u x ), where f1 starts at 0 and ends at u x is the end point, and the slope is a ramp function of p; The first dynamic coal feeding amount u2 is calculated as: u2 = u x (1-1 / (T1s+1)), where T1 is the time inertia constant and s is the Laplace operator.

3. The feedforward control method of a coal-fired unit according to claim 1, characterized in that: Get the maximum coal feeding amount u x The steps include: Get the current load N of the coal-fired unit when it enters the heat storage state x , according to the current load N of the unit x Calculate the maximum flue gas extraction volume D when the coal-fired unit enters the heat storage condition x :D x =f2(N x ); The maximum coal feed amount u x Calculated as: x =D x / k0, where k0 is the conversion coefficient.

4. The feedforward control method for a coal-fired unit according to claim 3, characterized in that: Obtaining the conversion coefficient k0 includes the following steps: Obtain the average flue gas flow rate Q0 and the average coal supply u0 under non-heat storage conditions and when the unit load is in a stable state, and calculate the conversion coefficient k0: k0=Q0 / u0.

5. The feedforward control method for a coal-fired unit according to claim 4, characterized in that: The conditions for judging whether the unit load is in a stable state are: ; Where: N—unit load; n—data length.

6. The feedforward control method for a coal-fired unit according to claim 5, characterized in that: The average flue gas flow rate Q0 is calculated as: ; The average coal feeding amount u0 is calculated as: ; Where: Q—unit flue gas flow rate; u—coal supply quantity of the unit.

7. The feedforward control method for a coal-fired unit according to claim 1, characterized in that: The third control signal is calculated according to the first static coal feeding amount u1 and the first dynamic coal feeding amount u2, specifically comprising the following steps: Obtaining the sum of the first static coal feeding amount u1 and the first dynamic coal feeding amount u2. If the sum of the first static coal feeding amount u1 and the first dynamic coal feeding amount u2 is lower than the safety amplitude, the sum of the first static coal feeding amount u1 and the first dynamic coal feeding amount u2 is the third control signal; If the sum of the first static coal feeding rate u1 and the first dynamic coal feeding rate u2 is higher than the safety amplitude, the safety amplitude is the third control signal.

8. The feedforward control method for a coal-fired unit according to any one of claims 1 to 7, characterized in that: When the coal-fired unit enters the heat storage state, the following steps are also included: Obtaining a first superheater outlet temperature setting value and a first superheater outlet temperature measured value, inputting the first superheater outlet temperature setting value and the first superheater outlet temperature measured value into a second PID controller, and then outputting a first desuperheating water outlet temperature setting value; Obtaining a first measured value of the outlet temperature of the cooling water, inputting the first set value of the outlet temperature of the cooling water and the first measured value of the outlet temperature of the cooling water into a third PID controller and then outputting a fourth control signal; Outputting the sum of the fourth control signal and the fifth control signal to the desuperheating water valve PID controller, and adjusting the opening of the desuperheating water valve according to the output of the desuperheating water valve PID controller; The fifth control signal is -u z (1 / (T2s+1) 3 ), where T2 is the time inertia constant, s is the Laplace operator, and u z It is the setting value for debugging.

9. The feedforward control method for a coal-fired unit according to any one of claims 1 to 7, characterized in that: When the coal-fired unit exits the heat storage state, the following steps are also included: Calculate and obtain a sixth control signal according to the load instruction of the second unit; Obtaining a second main steam pressure measured value and a second main steam pressure set value, inputting the second main steam pressure measured value and the second main steam pressure set value into a first PID controller and then outputting a seventh control signal; According to the maximum coal feeding amount u x Calculate and obtain a second static coal feeding amount u1' and a second dynamic coal feeding amount u2', and calculate and obtain an eighth control signal according to the second static coal feeding amount u1' and the second dynamic coal feeding amount u2'; The sum of the sixth control signal, the seventh control signal and the eighth control signal is output to the boiler main control PID controller, and the coal feed amount is adjusted according to the output of the boiler main control PID controller to control the main steam pressure.

10. The feedforward control method for a coal-fired unit according to claim 9, characterized in that: The second static coal feeding amount u1' is calculated as: u1'=f3(u x ), where f3 is u x A ramp function with a starting point of , an end point of 0, and a slope of -p; The second dynamic coal feeding amount u2' is calculated as: u2'=-u x (1-1 / (T1s+1)), where T1 is the time inertia constant and s is the Laplace operator.

11. The feedforward control method for a coal-fired unit according to any one of claims 1 to 7, characterized in that: When the coal-fired unit exits the heat storage state, the following steps are also included: Obtaining a second superheater outlet temperature setting value and a second superheater outlet temperature measured value, inputting the second superheater outlet temperature setting value and the second superheater outlet temperature measured value into a second PID controller, and then outputting a second desuperheating water outlet temperature setting value; Obtaining a measured value of the second cooling water outlet temperature, inputting the second cooling water outlet temperature setting value and the second cooling water outlet temperature measured value into a third PID controller and then outputting a ninth control signal; The sum of the ninth control signal and the tenth control signal is output to the cooling water valve PID controller, and the opening of the cooling water valve is adjusted according to the output of the cooling water valve PID controller; the tenth control signal is ,in, is the time inertia constant, s is the Laplace operator, u z It is the setting value for debugging.

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