System and method for controlling stable steam temperature of blending combustion economic coal of thermal power generating unit

Abstract

Provided is a thermal power generating unit blending combustion economic coal stable steam temperature control system. A load instruction unit is connected to a second function module, a third function module and a fourth function module. The load rising state unit, the fourth function module and the third function module are respectively connected to the first switching module; the variable load feed-forward unit is respectively connected to the fifth function module and the sixth function module; the variable load state unit, the sixth function module and the fifth function module are respectively connected to the second switching module; the output ends of the first switching module and the second switching module are connected to the first multiplication module; the output end of the first multiplication module and the output end of the second function module are respectively connected to the third switching module; the boiler instruction unit is sequentially connected to the first function module and the first rate module; the output end of the first rate module and the output end of the third switching module are both connected to the first inertia module, and the output end of the first inertia module is connected to the water supply instruction unit. The invention further provides a control method. According to the invention, stable and efficient control of the main steam temperature under different working conditions and various load sections is realized.

Description

Technical Field

[0001] This invention belongs to the field of intelligent control of generator sets, specifically relating to a control system and method for stabilizing steam temperature in thermal power units by co-firing economic coal. Background Technology

[0002] To reduce the operating costs of thermal power units, blending with economical coal is generally adopted to lower fuel costs. However, during actual load changes, the calorific value of the blended economical coal deviates significantly from the design coal quality, leading to large fluctuations in main steam temperature and the risk of overheating of the superheater walls. During load increases, the gradual addition of economical coal reduces its calorific value, resulting in a relative water-to-coal ratio, which manifests as a rapid decrease in main steam temperature. Conversely, during load decreases, the gradual removal of economical coal increases its calorific value, causing a faster rise in superheater wall temperature, accompanied by a rapid increase in main steam temperature. Therefore, timely adjustments to the economical coal quality to the design coal quality and dynamic adjustments to the water-to-coal ratio are crucial.

[0003] Therefore, based on the above-mentioned background, it is urgent to study a control method and system for stabilizing the steam temperature of thermal power units by co-firing economic coal, so as to achieve the goal of stable and efficient control of the main steam temperature under different operating conditions and load segments. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the present invention aims to provide a control system and method for stabilizing steam temperature in thermal power units by co-firing economic coal. The invention automatically corrects the coal feeder quantity based on the change in the calorific value of economic coal and uses it as the check coal quantity. At the same time, it automatically adjusts the feedwater command inertia time according to the change in the separator inlet steam temperature and the different load changes, so as to achieve dynamic balance of water-coal ratio. By suppressing the fluctuation of the superheater wall temperature through water-coal ratio, the main steam temperature is stabilized.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A control system for stabilizing steam temperature in a thermal power unit by co-firing economical coal, the control system comprising:

[0007] The rate-afterload instruction unit is used to act on the second function module, the third function module, and the fourth function module respectively, and after being converted by each function module, the corresponding output value is obtained.

[0008] The load increase state unit is used to trigger the first switching module. When the load increase state unit is active, the output value of the fourth function module is output. When the load increase state unit is active, the output value of the third function module is output.

[0009] The variable load feedforward unit is used to act on the fifth function module and the sixth function module respectively, and the corresponding output values ​​are obtained after being converted by each function module.

[0010] The variable load state unit is used to trigger the second switching module. When the variable load state unit is active, the output value of the sixth function module is output. When the variable load state unit is active, the output value of the fifth function module is output.

[0011] The boiler instruction unit is used to act on the first function module, and after being converted by the function module, the corresponding output values ​​are obtained respectively.

[0012] The water supply command unit is used to control the water supply command after it has been calculated by the first inertial module;

[0013] The first function module is used to perform a linear interpolation function on the input value of the boiler instruction unit and then output the corresponding output value.

[0014] The second function module is used to perform a linear interpolation function on the input value of the rate afterload command and then output the corresponding output value.

[0015] The third function module is used to perform a linear interpolation function on the input value of the rate afterload command and then output the corresponding output value.

[0016] The fourth function module is used to perform a linear interpolation function on the input value of the rate afterload command and then output the corresponding output value.

[0017] The fifth function module is used to perform a linear interpolation function on the input value of the variable load feedforward and then output the corresponding output value.

[0018] The sixth function module is used to perform a linear interpolation function on the input value of the variable load feedforward and output the corresponding output value.

[0019] The first switching module is used to output the output value of the fourth function module when the load increase state unit is , and to output the output value of the third function module when the load increase state unit is .

[0020] The second switching module is used to output the output value of the sixth function module when the variable load state unit is , and to output the output value of the fifth function module when the variable load state unit is .

[0021] The third switching module is used to output the output value of the first multiplication module when the trigger end is 0, and output the output value of the second function module when it is 0.

[0022] The first multiplication module is used to obtain the output value by multiplying the output of the first switching module with the output of the second switching module.

[0023] The first rate module is used to obtain the output value of the first function module after it has been limited by its maximum rate.

[0024] The first inertial module is used to obtain the output value after the first rate module and the third switching module have been applied to the inertial time.

[0025] The rate-afterload command unit is connected to the second function module, the third function module, and the fourth function module, respectively; the output terminals of the load increase state unit, the fourth function module, and the third function module are connected to the trigger terminal, the "Y" terminal, and the "N" terminal of the first switching module, respectively; the variable load feedforward unit is connected to the fifth function module and the sixth function module, respectively; the output terminals of the variable load state unit, the sixth function module, and the fifth function module are connected to the trigger terminal, the "Y" terminal, and the "N" terminal of the second switching module, respectively; the output terminals of the first switching module and the second switching module are both connected to the first multiplication module; the output terminals of the first multiplication module and the second function module are respectively connected to the "Y" terminal and the "N" terminal of the third switching module; the boiler command unit is connected to the first function module and the first rate module in sequence; the output terminals of the first rate module and the third switching module are both connected to the first inertial module, and the output terminal of the first inertial module is connected to the feedwater command unit.

[0026] Furthermore, the control system also includes:

[0027] The coal feeder calculation module is used to calculate the output value by multiplying the coal quantity input value and calorific value input value of all coal feeders with the output value of the seventh function module.

[0028] The first addition module is used to add the output values ​​of each coal feeder calculation module to obtain the output value;

[0029] The first multiplication module is used to perform multiplication calculations between the output of the first addition module and the BTU correction command to obtain the output value;

[0030] The first PID control module is used to apply the fuel command unit to the SP input terminal, and the output terminal of the first multiplication module is applied to the PV input terminal. The output value is obtained after PID calculation.

[0031] The coal feeder instruction unit is used to transmit the output value calculated by the first PID control module to each coal feeder.

[0032] The output value of the coal feeder calculation module is connected to the first summing module; the output of the first summing module and the BTU correction command unit are both connected to the first multiplication module; the output of the first multiplication module and the fuel command unit are respectively connected to the "PV" and "SP" terminals of the first PID control module; and the output of the first PID control module is connected to the coal feeder command unit.

[0033] Preferably, in the coal feeder calculation module, the coal feeders include coal feeder A, coal feeder B, coal feeder C, coal feeder D, coal feeder E, and coal feeder F, wherein the coal feeder A calculation module includes:

[0034] A coal feeder coal quantity unit is used to apply the input value to one of the input terminals of the second multiplication module;

[0035] A coal feeder calorific value unit is used to apply the input value to the input terminal of the seventh function module;

[0036] The seventh function module is used to convert the input value into a design coal calorific value correction coefficient, which is then applied to one of the inputs of the second multiplication module.

[0037] The second multiplication module is used to multiply the coal quantity of feeder A with the output of the seventh function module to obtain the output value.

[0038] A method for controlling the stable steam temperature of a thermal power unit by blending economical coal, the method comprising the following steps:

[0039] (1) The feedwater command is automatically adjusted according to the changes in the inlet steam temperature of the separator and the different load increases and decreases. The process is as follows:

[0040] When the load increase state unit is active, the first switching module outputs the calculated value of the fourth function module; when the load increase state unit is active, the first switching module outputs the calculated value of the third function module. When the load change state unit is active, the second switching module outputs the calculated value of the sixth function module; when the load change state unit is active, the second switching module outputs the calculated value of the fifth function module. The output of the first switching module and the output of the second switching module are multiplied to obtain the output of the first multiplication module. When the trigger of the third switching module is active, the third switching module outputs the calculated value of the first multiplication module. The boiler command unit obtains the calculated value of the first rate module after judging by the first function module and the first rate module. The output of the third switching module and the calculated value of the first rate module jointly trigger the first inertia module, and finally obtain the water supply command.

[0041] Furthermore, the method also includes the following steps:

[0042] (2) The coal feeder is automatically adjusted according to the change in the calorific value of economic coal. The process is as follows:

[0043] The output values ​​of the coal feeder calculation module are added together to obtain the coal feeder correction value. Then, it is multiplied with the BTU correction instruction unit. The result is the output of the first multiplication module, which is applied to the "PV" terminal of the first PID control module. The fuel instruction is applied to the "SP" terminal of the first PID control module. Finally, after calculation by the first PID control module, the coal feeder instructions A to F are obtained.

[0044] Preferably, the coal feeders include feeder A, feeder B, feeder C, feeder D, feeder E, and feeder F. The calorific value unit of feeder A is calculated by the seventh function module and then multiplied by the coal quantity of feeder A to obtain the correction value of feeder A. The correction values ​​of feeders B, C, D, E, and F are calculated in the same way as A. Finally, the correction values ​​of feeders A, B, C, D, E, and F are obtained, and the above six results are added together.

[0045] The present invention provides a method for controlling the stable steam temperature of thermal power units using blended economic coal. In the control of steam temperature in thermal power units using blended economic coal, due to the uncertainty and nonlinearity of changes in factors such as coal quality and load, the method allows for flexible adjustment of control parameters based on different operating conditions and experience, achieving precise control of steam temperature. It solves the problem of achieving rapid load response to grid load demands and stable and controllable main steam pressure during load changes in thermal power units through dynamic adjustment of the water-coal ratio.

[0046] In summary, the method and system for controlling the stable steam temperature of thermal power units using blended economic coal, as described in this invention, pre-sets the calorific value of the economic coal based on changes in the calorific value of the coal entering the silo. In the calculation of the main control coal quantity, calorific value correction of the coal distribution silo is achieved, rapidly approximating the design calorific value. During load changes, the feedwater command inertia time is dynamically corrected based on changes in the separator inlet steam temperature, achieving transient water-coal balance during unit load changes, and stabilizing the main steam temperature by suppressing changes in the superheater wall temperature.

[0047] The beneficial effects of this invention are: to achieve stable and efficient control of main steam temperature under different operating conditions and load segments. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the feedwater control principle for a method to stabilize steam temperature when co-firing economical coal in a thermal power unit.

[0049] Figure 2 A schematic diagram of the coal feeding control principle for controlling the stable steam temperature of thermal power units by blending economic coal. Detailed Implementation

[0050] The present invention will now be further described with reference to the accompanying drawings.

[0051] Reference Figure 1 and Figure 2 A control system for stabilizing steam temperature in thermal power units by co-firing economical coal includes:

[0052] The rate afterload instruction unit 001 is used to act on the second function module 008, the third function module 009, and the fourth function module 010 respectively, and after being converted by each function module, the corresponding output value is obtained.

[0053] The load increase state unit 002 is used to trigger the first switching module 013. When the load increase state unit 002 is 1, the output value of the fourth function module 010 is output. When the load increase state unit 002 is 0, the output value of the third function module 009 is output.

[0054] The variable load feedforward unit 003 is used to act on the fifth function module 011 and the sixth function module 012 respectively, and the corresponding output values ​​are obtained after being converted by each function module.

[0055] The variable load state unit 004 is used to trigger the second switching module 014. When the variable load state unit 004 is 1, the output value of the sixth function module 012 is output. When the variable load state unit 004 is 0, the output value of the fifth function module 011 is output.

[0056] Boiler instruction unit 005 is used to act on the first function module 007, and after the function module calculates, the corresponding output values ​​are obtained respectively.

[0057] Water supply command unit 006 is used to control the water supply command after it has been calculated by the first inertial module 018;

[0058] The first function module 007 is used to perform a linear interpolation function with the input value of the boiler instruction unit 005 and then output the corresponding output value.

[0059] The second function module 008 is used to perform a linear interpolation function on the input value of the rate afterload command 001 and then output the corresponding output value.

[0060] The third function module 009 is used to perform a linear interpolation function with the input value of the rate afterload command 001 and then output the corresponding output value.

[0061] The fourth function module 010 is used to perform a linear interpolation function on the input value of the rate afterload command 001 and then output the corresponding output value.

[0062] The fifth function module 011 is used to perform a linear interpolation function with the input value of the variable load feedforward 003 and then output the corresponding output value.

[0063] The sixth function module 012 is used to perform a linear interpolation function with the input value of the variable load feedforward 003 and then output the corresponding output value.

[0064] The first switching module 013 is used to output the output value of the fourth function module 010 when the load increase state unit 002 is 1, and to output the output value of the third function module 009 when the load increase state unit 002 is 0.

[0065] The second switching module 014 is used to output the output value of the sixth function module 012 when the variable load state unit 004 is 1, and to output the output value of the fifth function module 011 when the variable load state unit 004 is 0.

[0066] The third switching module 015 is used to output the output value of the first multiplication module 016 when its trigger terminal is 1, and to output the output value of the second function module 008 when it is 0.

[0067] The first multiplication module 016 is used to obtain the output value after multiplication between the output of the first switching module 013 and the second switching module 014;

[0068] The first rate module 017 is used by the first function module 007 to obtain the output value after its rate judgment.

[0069] The first inertial module 018 is used to obtain the output value after the first rate module 017 and the third switching module 015 are applied to the inertial judgment.

[0070] The rate-afterload command unit 001 is connected to the second function module 008, the third function module 009, and the fourth function module 010, respectively; the output terminals of the load increase state unit 002, the fourth function module 010, and the third function module 009 are respectively connected to the trigger terminal, the "Y" terminal, and the "N" terminal of the first switching module 013; the variable load feedforward unit 003 is connected to the fifth function module 011 and the sixth function module 012, respectively; the output terminals of the variable load state unit 004, the sixth function module 012, and the fifth function module 011 are respectively connected to the trigger terminal of the second switching module 014. The output terminals of the first switching module 013 and the second switching module 014 are connected to the first multiplication module 016; the output terminals of the first multiplication module 016 and the second function module 008 are respectively connected to the "Y" terminal and the "N" terminal of the third switching module 015; the boiler instruction unit 005 is sequentially connected to the first function module 007 and the first rate module 017; the output terminals of the first rate module 017 and the third switching module 015 are both connected to the first inertia module 018, and the output terminal of the first inertia module 018 is connected to the water supply instruction unit 006;

[0071] The coal feeder calculation module is used to multiply the coal quantity input value and calorific value input value of each coal feeder by the output value of the seventh function module to obtain the output value.

[0072] The coal feeder calculation module includes coal feeders A, B, C, D, E, and F, wherein the coal feeder A calculation module includes:

[0073] A coal feeder coal quantity unit 019 is used to apply the input value to one of the input terminals of the second multiplication module 029;

[0074] A coal feeder calorific value unit 020 is used to apply the input value to the input terminal of the seventh function module 028;

[0075] The seventh function module 028 is used to apply the input value to one of the input terminals of the second multiplication module 029;

[0076] The second multiplication module 029 is used to perform multiplication calculations between the coal quantity 019 of the A coal feeder and the output of the seventh function module 028 to obtain the output value;

[0077] The calculation method for B is the same as that for A. Unit 021 (B coal feeder calculation module) is used to apply the input value to one of the input terminals of the first addition module 030.

[0078] The calculation method for C is the same as that for A. Unit 022 (C coal feeder calculation module) is used to apply the input value to one of the input terminals of the first addition module 030.

[0079] The calculation method for D is the same as that for A. Unit 023 (D coal feeder calculation module) is used to apply the input value to one of the input terminals of the first addition module 030.

[0080] The calculation method for E is the same as that for A. Unit 024 (E coal feeder calculation module) is used to apply the input value to one of the input terminals of the first addition module 030.

[0081] The calculation method for F is the same as that for A. Unit 025 (F coal feeder calculation module) is used to apply the input value to one of the input terminals of the first addition module 030.

[0082] BTU correction instruction unit 026 is used to apply the input value to one of the input terminals of the first multiplication module 031;

[0083] Fuel command unit 027 is used to apply the input value to the SP input terminal of the first PID control module 032;

[0084] The first addition module 030 is used to perform addition calculations on the output terminal of the second multiplication module 029 of each coal feeder calculation module to obtain the output value;

[0085] The first multiplication module 031 is used to perform multiplication calculations between the output of the first addition module 030 and the BTU correction instruction 026 to obtain the output value.

[0086] The first PID control module 032 is used to apply the fuel command unit 027 to the SP input terminal, and the output terminal of the first multiplication module 031 is applied to the PV input terminal to obtain the output value after PID calculation.

[0087] The A-F coal feeder instruction unit 033 is used to calculate the output value after the first PID adjustment module 032.

[0088] The A feeder calorific value unit 020 is connected to the seventh function module 028. The output terminals of the A feeder coal quantity unit 019 and the seventh function module 028 are both connected to the second multiplication module 029. The output terminal of the second multiplication module 029, the B calculation method is the same as A unit 021, the C calculation method is the same as A unit 022, the D calculation method is the same as A unit 023, the E calculation method is the same as A unit 024, and the F calculation method is the same as A unit 025 are all connected to the first addition module 030. The output terminal of the first addition module 030 and the BTU correction command unit 026 are both connected to the first multiplication module 031. The output terminal of the first multiplication module 031 and the fuel command unit 027 are respectively connected to the "PV" terminal and the "SP" terminal of the first PID adjustment module 032. The output terminal of the first PID adjustment module 032 is connected to the A-F feeder command units 033.

[0089] A method for controlling the stable steam temperature of a thermal power unit by co-firing economical coal includes the following steps:

[0090] (1) The feedwater command is automatically adjusted according to the changes in the inlet steam temperature of the separator and the different load increases and decreases. The process is as follows:

[0091] When the load increase state unit 002 is 1, the first switching module 013 outputs the calculated value of the fourth function module 010; when the load increase state unit 002 is 0, the first switching module 013 outputs the calculated value of the third function module 009. When the load change state unit 004 is 1, the second switching module 014 outputs the calculated value of the sixth function module 012; when the load change state unit 004 is 0, the second switching module 014 outputs the calculated value of the fifth function module 011. The output terminal of the first switching module 013 is connected to the second switching module 014. The output of the switching module 014 performs a multiplication calculation to obtain the output of the first multiplication module 016. When the trigger of the third switching module 015 is 1, the third switching module 015 outputs the calculated value of the first multiplication module 016. The boiler instruction unit 005 obtains the calculated value of the first rate module 017 after judgment by the first function module 007 and the first rate module 017. The output of the third switching module 015 and the calculated value of the first rate module 017 jointly trigger the first inertia module 018, and finally obtain the water supply instruction.

[0092] (2) The coal feeder is automatically adjusted according to the change in the calorific value of economic coal. The process is as follows:

[0093] After the calorific value unit 020 of feeder A is calculated by the seventh function module 028, it is multiplied by the coal quantity 019 of feeder A to obtain the correction value of feeder A. The remaining correction values ​​of feeders BCDEF are calculated in the same way as A, and finally the correction values ​​of feeders A, B, C, D, E, and F are obtained. The above 6 results are added together to obtain the total feeder correction value from A to F. Then, it is multiplied by the BTU correction instruction unit 026. The result is the output of the first multiplication module 031 and is applied to the "PV" terminal of the first PID adjustment module 032. The fuel instruction 027 is applied to the "SP" terminal of the first PID adjustment module 032. Finally, after the first PID adjustment module 032 calculates, the feeder instructions from A to F are obtained.

[0094] The Figure 1 and Figure 2This document describes a control method and system schematic for stabilizing steam temperature in thermal power units using blended economic coal. Specifically, it includes: load command 001, load increase state 002, load change feedforward 003, load change state 004, boiler command 005, feedwater command 006, first function module 007, second function module 008, third function module 009, fourth function module 010, fifth function module 011, sixth function module 012, first switching module 013, second switching module 014, third switching module 015, first multiplication module 016, first rate module 017, and first inertia module. Module 018, Coal quantity of feeder A; 019, Calorific value of feeder A; 020, Calculation method of B is the same as A; 021, Calculation method of C is the same as A; 022, Calculation method of D is the same as A; 023, Calculation method of E is the same as A; 024, Calculation method of F is the same as A; 025, BTU correction instruction; 026, Fuel instruction; 027, Seventh function module; 028, Second multiplication module; 029, First addition module; 030, First multiplication module; 031, First PID adjustment module; 032, Feeder instructions A to F; 033. Figure 1 The control strategy logic includes the following parts:

[0095] The rate-afterload command 001 is connected to the second function module 008, the third function module 009, and the fourth function module 010, respectively; the load increase state 002, the output terminals of the fourth function module 010, and the third function module 009 are respectively connected to the trigger terminal, the "Y" terminal, and the "N" terminal of the first switching module 013; the variable load feedforward 003 is connected to the fifth function module 011 and the sixth function module 012, respectively; the variable load state 004, the output terminal of the sixth function module 012, and the fifth function module 011 are respectively connected to the second switching module 014. The output terminals of the first switching module 013 and the second switching module 014 are both connected to the first multiplication module 016; the output terminals of the first multiplication module 016 and the second function module 008 are respectively connected to the "Y" terminal and the "N" terminal of the third switching module 015; the boiler command 005 is connected to the first function module 007 and the first rate module 017 in sequence; the output terminals of the first rate module 017 and the third switching module 015 are both connected to the first inertia module 018, and the output terminal of the first inertia module 018 is connected to the water supply command 006.

[0096] Figure 2 The control strategy logic includes the following parts:

[0097] The calorific value of feeder A (020) is connected to the seventh function module (028). The output of feeder A (019) and the seventh function module (028) is connected to the second multiplication module (029). The output of the second multiplication module (029), the calculation method of B (021), the calculation method of C (022), the calculation method of D (023), the calculation method of E (024), and the calculation method of F (025) are all connected to the first addition module (030). The output of the first addition module (030) and the BTU correction command (026) are both connected to the first multiplication module (031). The output of the first multiplication module (031) and the fuel command (027) are respectively connected to the "PV" and "SP" terminals of the first PID control module (032). The output of the first PID control module (032) is connected to the feeder commands (033) of feeders A through F.

[0098] The control function operation steps in this embodiment are as follows:

[0099] (1) When the load increase state 002 is 1, the first switching module 013 outputs the calculated value of the fourth function module 010; when the load increase state 002 is 0, the first switching module 013 outputs the calculated value of the third function module 009; when the load change state 004 is 1, the second switching module 014 outputs the calculated value of the sixth function module 012; when the load change state 004 is 0, the second switching module 014 outputs the calculated value of the fifth function module 011; the output terminal of the first switching module 013 is connected to the second switching module 014. The output of module 014 performs a multiplication calculation to obtain the output of the first multiplication module 016. When the trigger of the third switching module 015 is 1, the third switching module 015 outputs the calculated value of the first multiplication module 016. The boiler command 005, after being judged by the first function module 007 and the first rate module 017, obtains the calculated value of the first rate module 017. The output of the third switching module 015 and the calculated value of the first rate module 017 jointly trigger the first inertia module 018, ultimately obtaining the feedwater command 006. This technical approach achieves the goal of automatically adjusting the inertia time of the feedwater command according to the changes in the separator inlet steam temperature and the different load increases and decreases.

[0100] (2) The calorific value 020 of feeder A is calculated by the seventh function module 028 and then multiplied by the coal quantity 019 of feeder A to obtain the correction value of feeder A. The remaining correction values ​​of feeders B, C, D, E, and F are calculated in the same way as A, finally obtaining the correction values ​​of feeders A, B, C, D, E, and F. These six results are added together to obtain the total feeder correction value from A to F. Then, it is multiplied by the BTU correction instruction 026, and the result is output of the first multiplication module 031, which is applied to the "PV" terminal of the first PID control module 032. The fuel instruction 027 is applied to the "SP" terminal of the first PID control module 032. Finally, after calculation by the first PID control module 032, the feeder instructions 033 from A to F are obtained. This technical route realizes the goal of automatically correcting the coal quantity of the feeder according to the change of the calorific value of economic coal and using it as the check coal quantity.

[0101] (3) The above technical routes have achieved the following: based on the change in the calorific value of the coal entering the warehouse and the pre-set calorific value of the economic coal, the calorific value of the coal compartment is corrected in the calculation of the main control coal quantity of fuel, and the calorific value of the coal compartment is quickly approached; during the load change process, the feedwater command inertia time is dynamically corrected according to the change in the inlet steam temperature of the separator, and the transient water-coal balance is achieved during the load change process of the unit, and the main steam temperature is stabilized by suppressing the change in the wall temperature of the large screen superheater; the unit load is quickly responded to the grid load demand and the main steam pressure of the unit is stable and controllable.

[0102] The embodiments described in this specification are merely examples of implementations of the inventive concept and are for illustrative purposes only. The scope of protection of this invention should not be considered limited to the specific forms described in these embodiments; rather, it extends to equivalent technical means conceived by those skilled in the art based on the inventive concept.

Claims

1. A control system for stabilizing steam temperature in thermal power units by co-firing economical coal, characterized in that, The control system includes: The rate afterload instruction unit (001) is used to act on the second function module (008), the third function module (009), and the fourth function module (010) respectively, and the corresponding output values ​​are obtained after being converted by each function module; The load increase state unit (002) is used to act on the trigger terminal of the first switching module (013). When the load increase state unit (002) is 1, the output value of the fourth function module (010) is output. When the load increase state unit (002) is 0, the output value of the third function module (009) is output. The variable load feedforward unit (003) is used to act on the fifth function module (011) and the sixth function module (012) respectively, and the corresponding output values ​​are obtained after being converted by each function module; The variable load state unit (004) is used to act on the trigger terminal of the second switching module (014). When the variable load state unit (004) is 1, the output value of the sixth function module (012) is output. When the variable load state unit (004) is 0, the output value of the fifth function module (011) is output. The boiler instruction unit (005) is used to act on the first function module (007), and after being converted by the function module, the corresponding output values ​​are obtained respectively. The water supply command unit (006) is used to control the water supply command after it has been calculated by the first inertial module (018); The first function module (007) is used to perform a linear interpolation function with the input value of the boiler instruction unit (005) and then output the corresponding output value. The second function module (008) is used to perform a linear interpolation function with the input value of the rate afterload instruction (001) and then output the corresponding output value. The third function module (009) is used to perform a linear interpolation function with the input value of the rate afterload instruction (001) and then output the corresponding output value. The fourth function module (010) is used to perform a linear interpolation function with the input value of the rate afterload instruction (001) and then output the corresponding output value. The fifth function module (011) is used to perform a linear interpolation function with the input value of the variable load feedforward (003) and then output the corresponding output value. The sixth function module (012) is used to perform a linear interpolation function with the input value of the variable load feedforward (003) and then output the corresponding output value. The first switching module (013) is used to output the output value of the fourth function module (010) when the load increase state unit (002) is 1, and to output the output value of the third function module (009) when the load increase state unit (002) is 0. The second switching module (014) is used to output the output value of the sixth function module (012) when the variable load state unit (004) is 1, and to output the output value of the fifth function module (011) when the variable load state unit (004) is 0. The third switching module (015) is used to output the output value of the first multiplication module (016) when the trigger terminal is 1, and to output the output value of the second function module (008) when it is 0. The first multiplication module (016) is used to multiply the output of the first switching module (013) and the second switching module (014) to obtain the output value; The first rate module (017) is used to obtain the output value of the first function module (007) after its maximum rate limit; The first inertial module (018) is used to obtain the output value after the first rate module (017) and the third switching module (015) are applied to the inertial time; The rate-afterload command unit (001) is connected to the second function module (008), the third function module (009), and the fourth function module (010), respectively; the output terminals of the load increase state unit (002), the fourth function module (010), and the third function module (009) are connected to the trigger terminal, the "Y" terminal, and the "N" terminal of the first switching module (013), respectively; the variable load feedforward unit (003) is connected to the fifth function module (011) and the sixth function module (012), respectively; the output terminals of the variable load state unit (004), the sixth function module (012), and the fifth function module (011) are connected to the trigger terminal of the second switching module (014). The output terminals of the first switching module (013) and the second switching module (014) are connected to the first multiplication module (016); the output terminals of the first multiplication module (016) and the second function module (008) are respectively connected to the "Y" terminal and the "N" terminal of the third switching module (015); the boiler instruction unit (005) is connected in sequence to the first function module (007) and the first rate module (017); the output terminals of the first rate module (017) and the third switching module (015) are both connected to the first inertial module (018), and the output terminal of the first inertial module (018) is connected to the water supply instruction unit (006).

2. The control system for stabilizing steam temperature in a thermal power unit by blending economical coal as described in claim 1, characterized in that, The control system further includes: The coal feeder calculation module is used to calculate the output value by multiplying the coal quantity input value and calorific value input value of all coal feeders with the output value of the seventh function module. The first addition module (030) is used to add the output values ​​of each coal feeder calculation module to obtain the output value; The first multiplication module (031) is used to perform multiplication calculations between the output of the first addition module (030) and the BTU correction command (026) to obtain the output value; The first PID control module (032) is used to apply the fuel command unit (027) to the SP input terminal and the output terminal of the first multiplication module (031) to the PV input terminal, and the output value is obtained after PID calculation; The coal feeder instruction unit (033) is used to transmit the output value calculated by the first PID control module (032) to each coal feeder; The output value of the coal feeder calculation module is connected to the first addition module (030); the output end of the first addition module (030) and the BTU correction command unit (026) are both connected to the first multiplication module (031); the output end of the first multiplication module (031) and the fuel command unit (027) are respectively connected to the "PV" end and the "SP" end of the first PID adjustment module (032); the output end of the first PID adjustment module (032) is connected to the coal feeder command unit (033).

3. The control system for stabilizing steam temperature in a thermal power unit by blending economical coal as described in claim 2, characterized in that, The coal feeder calculation module includes coal feeders A, B, C, D, E, and F, wherein the coal feeder A calculation module includes: A coal feeder coal quantity unit (019) is used to apply the input value to one of the input terminals of the second multiplication module (029); A coal feeder calorific value unit (020) is used to apply the input value to the input terminal of the seventh function module (028); The seventh function module (028) is used to convert the input value into a design coal calorific value correction coefficient, which is applied to one of the input terminals of the second multiplication module (029); The second multiplication module (029) is used to perform multiplication calculations between the coal quantity of the A coal feeder (019) and the output of the seventh function module (028) to obtain the output value.

4. A control method for implementing the control system for stabilizing steam temperature in a thermal power unit by blending economic coal as described in claim 1, characterized in that, The control method includes the following steps: (1) The feedwater command is automatically adjusted according to the changes in the inlet steam temperature of the separator and the different load increases and decreases. The process is as follows: When the load increase state unit (002) is 1, the first switching module (013) outputs the calculated value of the fourth function module (010); when the load increase state unit (002) is 0, the first switching module (013) outputs the calculated value of the third function module (009); when the load change state unit (004) is 1, the second switching module (014) outputs the calculated value of the sixth function module (012); when the load change state unit (004) is 0, the second switching module (014) outputs the calculated value of the fifth function module (011); the output terminal of the first switching module (013) is connected to the second The output of the switching module (014) performs a multiplication calculation to obtain the output of the first multiplication module (016); when the trigger of the third switching module (015) is 1, the third switching module (015) outputs the calculated value of the first multiplication module (016); the boiler instruction unit (005) obtains the calculated value of the first rate module (017) after the judgment of the first function module (007) and the first rate module (017); the output of the third switching module (015) and the calculated value of the first rate module (017) jointly trigger the first inertial module (018) to finally obtain the water supply instruction.

5. The control method as described in claim 4, characterized in that, The method further includes the following steps: (2) The coal feeder is automatically adjusted according to the change in the calorific value of economic coal. The process is as follows: The output values ​​of the coal feeder calculation module are added together to obtain the coal feeder correction value. Then, it is multiplied by the BTU correction instruction unit (026). The result is the output of the first multiplication module (031), which is applied to the "PV" terminal of the first PID control module (032). The fuel instruction (027) is applied to the "SP" terminal of the first PID control module (032). Finally, the coal feeder instructions A to F are obtained after calculation by the first PID control module (032).

6. The control method as described in claim 4, characterized in that, The coal feeders include feeder A, feeder B, feeder C, feeder D, feeder E, and feeder F. The calorific value unit (020) of feeder A is calculated by the seventh function module (028) and then multiplied by the coal quantity (019) of feeder A to obtain the correction value of feeder A. The correction values ​​of feeders BCDEF are calculated in the same way as those of feeder A. Finally, the correction values ​​of feeders A, B, C, D, E, and F are obtained, and the above 6 results are added together.

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