Control system and method for suppressing main steam pressure fluctuation of primary frequency modulation considering feedwater feedforward

Abstract

The present invention belongs to the field of optimized operation of secondary reheat units, and specifically relates to a control system and method for suppressing main steam pressure fluctuations in primary frequency modulation using feed-forward feedwater. The present invention alters the primary frequency modulation control logic, mathematically processing the primary frequency modulation action amount in conjunction with the current main steam pressure deviation and important boiler-side parameters before feed-forwarding it to the steam pump for feed-water control. This allows for preemptive adjustments to steam pressure fluctuations caused by primary frequency modulation, rather than passively adjusting after steam pressure fluctuations are detected. This achieves preemptive and accurate suppression of steam pressure fluctuations generated by the secondary reheat unit during its participation in the primary frequency modulation of the power grid, reduces the amplitude of main steam pressure fluctuations, shortens the adjustment time for the main steam pressure to stabilize, and maintains safe and economical operation of the unit while ensuring primary frequency modulation performance.

Description

Technical Field

[0001] The present invention belongs to the field of optimized operation of secondary reheat units, and in particular relates to a control system and method for suppressing main steam pressure fluctuations of a primary frequency modulation system considering feedwater feedforward. Background Art

[0002] The emergence of boiler secondary reheat technology has significantly improved the main steam and reheat steam parameters of thermal power units, greatly enhancing the design thermal efficiency of thermal power units. This is of great significance to the development of thermal power units themselves, as well as to alleviating the shortage of fossil energy and reducing the carbon emissions of power generation enterprises. However, as the temperature and pressure parameters of the main steam and reheat steam increase, the heat storage capacity of the secondary reheat unit decreases, the fluctuation of the main steam pressure with the change of the steam valve opening becomes larger, the action of the main steam pressure deviation correction loop increases, and the primary frequency regulation performance deteriorates. At the same time, due to the emergence of the need for synchronous coordinated control of the primary and secondary reheat steam of the secondary reheat unit, the difficulty of main steam pressure regulation in the primary frequency regulation increases sharply, and the main steam pressure stability deteriorates. Therefore, it is of practical value to study the control system and method for suppressing the main steam pressure fluctuation in the primary frequency regulation of the secondary reheat unit.

[0003] There have been studies in China on suppressing main steam pressure fluctuations in primary frequency regulation through feedforward signals. The published Chinese invention application "A control system and method for improving the performance indicators of primary frequency regulation of thermal power units" (publication number: CN114844060A) proposes feeding the primary frequency regulation load command forward to the steam turbine main control system to increase the main steam pressure deviation correction value and maintain the function, thereby improving the accuracy of primary frequency regulation. However, this will increase the main steam pressure fluctuations in the primary frequency regulation, affecting the safety and economy of the unit operation. The published Chinese invention application "A primary frequency regulation based on feedforward pressure automatic control system" (publication number: CN114216115A) proposes feeding the main steam pressure deviation signal forward to the boiler main control for fuel control. However, the adjustment must begin after the pressure deviation signal is collected, and the fuel adjustment process is slow, affecting the effect of suppressing the main steam pressure fluctuations. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides a control system and method for suppressing main steam pressure fluctuations by primary frequency modulation considering feedwater feedforward. The present invention proposes to feedforward the primary frequency modulation signal to the steam pump of the boiler master control to adjust the boiler feedwater flow rate, and quantitatively adjust the steam flow rate in advance before the pressure deviation is measured, thereby reducing the main steam pressure fluctuation amplitude and shortening the adjustment time for the main steam pressure to return to stability, ensuring the primary frequency modulation performance while maintaining the safe and economical operation of the unit.

[0005] The specific technical solutions are as follows:

[0006] Considering the feedwater feedforward primary frequency regulation main steam pressure fluctuation suppression control system, it includes:

[0007] A single pulse generator (2), wherein an input terminal of the single pulse generator (2) inputs a primary frequency modulation input (DEH) input signal (1);

[0008] A soft keyboard (5), wherein an input end of the soft keyboard (5) inputs a CCS primary frequency modulation switching instruction input (4);

[0009] a first logic OR unit (3), wherein a first input end of the first logic OR unit (3) is connected to an output end of the single pulse generator (2), and a second input end of the second logic OR unit (3) is connected to a first output end of the soft keyboard (5);

[0010] A first logical NOT unit (9), wherein an input terminal of the first logical NOT unit (9) inputs a frequency difference quality bad input signal (7);

[0011] A time-delay disconnection algorithm (10), wherein the input end of the time-delay disconnection algorithm (10) is connected to the output end of the logical NOT unit (9);

[0012] A second logical NOT unit (11), wherein an input terminal of the second logical NOT unit (11) inputs an RB action input signal (8);

[0013] A logic AND unit (12), wherein a first input terminal of the logic AND unit (12) inputs a coordination mode CCS input signal (6), a second input terminal of the logic AND unit (12) is connected to an output terminal of the delayed disconnection algorithm (10), and a third input terminal of the logic AND unit (12) is connected to an output terminal of the second logic NOT unit (11);

[0014] a third logical NOT unit (13), wherein an input end of the third logical NOT unit (13) is connected to an output end of the logical AND unit (12);

[0015] a second logic OR unit (14), wherein a first input end of the second logic OR unit (14) is connected to a second output end of the soft keyboard (5), and a second input end of the second logic OR unit (14) is connected to an output end of the third logic NOT unit (13);

[0016] An RS trigger (15), wherein an S terminal of the RS trigger (15) is connected to an output terminal of the first logic OR unit (3), and an R terminal of the RS trigger (15) is connected to an output terminal of the second logic OR unit (14);

[0017] an analog quantity switching selector (23), wherein an input end of the analog quantity switching selector (23) is connected to a first output end of the RS trigger (15);

[0018] An analog quantity generator (19), wherein the analog quantity generator (19) is connected to the N terminal of the analog quantity switching selector (23),

[0019] A linear converter (21), wherein the frequency difference signal (20) is input to an input end of the linear converter (21);

[0020] a first piecewise linear function generator (22), wherein the input end of the first piecewise linear function generator (22) is connected to the output end of the linear converter (21), and the output end is connected to the Y end of the analog switching selector (23);

[0021] An output speed regulator (24), wherein an input end of the output speed regulator (24) is connected to an output end of the analog switching selector (23);

[0022] A second piecewise linear function generator (27), wherein an input end of the second piecewise linear function generator (27) inputs a boiler master control corresponding load output signal (25);

[0023] A third piecewise linear function generator (28), wherein the input end of the third piecewise linear function generator (28) receives a main steam pressure deviation input signal (26);

[0024] an adder (29), wherein a first input end of the adder (29) is connected to an output end of the third piecewise linear function generator (28), a second input end is connected to an output end of the second piecewise linear function generator (27), and a third input end is connected to an output end of the output speed controller (24);

[0025] a fourth piecewise linear function generator (31), wherein the generator power signal (30) is input to an input end of the fourth piecewise linear function generator (31);

[0026] A maximizer (32) has a first input end connected to the output end of the adder (29), a second input end connected to the output end of the fourth piecewise linear function generator (31), and an output end outputting a steam pump instruction to be fed forward to the water supply pump.

[0027] Preferably, the system further comprises a fourth logical NOT unit (17), the input end of the fourth logical NOT unit (17) is connected to the second output end of the RS trigger (15), and the output end outputs a frequency modulation exit output signal (18).

[0028] Preferably, the RS trigger (15) further includes a third output terminal, and the third output terminal of the RS trigger (15) outputs a frequency modulation input output signal (16).

[0029] Preferably, a single pulser (2) is provided, and when the primary frequency modulation input (DEH) input signal (1) is 1, a signal 1 is input to the first input terminal of the first logic OR unit (3).

[0030] Preferably, a delayed disconnection algorithm (10) is set, and when the frequency difference quality that has not been collected has bad data, the frequency difference quality bad input signal (7) is input as 0; or when the frequency difference quality that has been collected has bad data, the frequency difference quality bad input signal (7) is input as 1 but continues for no longer than the time limit set by the delayed disconnection algorithm (10).

[0031] Preferably, the output speed regulator (24) is set according to the operating state of the unit so that the speed regulation rate of the primary frequency modulation instruction is within the operating boundary.

[0032] Preferably, the fourth piecewise linear function generator (31) limits the minimum water flow value of the motor power signal (30).

[0033] The control method for suppressing main steam pressure fluctuations in primary frequency modulation with feedwater feedforward consideration includes the following steps:

[0034] Step S1, setting a single pulser (2), when a frequency modulation input (DEH) input signal (1) is 1, inputting a signal 1 to a first input terminal of a first logic OR unit (3);

[0035] Step S2, setting the CCS primary frequency modulation switching instruction input (4) to 1, inputting a signal 1 to the first input terminal of the second logic OR unit (14); inputting a signal 1 to the second input terminal of the first logic OR unit (3); the first logic OR unit (3) performs an OR operation on its first input terminal and the second input terminal, and when one or both of the input signals of the first input terminal and the second input terminal of the first logic OR unit (3) are 1, inputting a signal 1 to the S terminal of the RS trigger (15);

[0036] S3, set the coordination mode CCS input signal (6) to 1, input signal 1 to the first input terminal of the logic and unit (12); set the delayed disconnection algorithm (10), when the frequency difference quality that has not been collected has bad data, the frequency difference quality bad input signal (7) is input to 0, and after being inverted by the first logic negation unit (9), input signal 1 to the second input terminal of the logic and unit (12); or when the frequency difference quality that has been collected has bad data, the frequency difference quality bad input signal (7) is input to 1 but does not exceed the time limit set by the delayed disconnection algorithm (10), input signal 1 to the second input terminal of the logic and unit (12);

[0037] When the auxiliary machine operates normally and no load shedding occurs, the RB action input signal (8) is 0, and after being negated by the second logic negation unit (11), a signal 1 is input to the third input terminal of the logic AND unit (12); when the input signals of the three input terminals of the logic AND unit (12) are all 1, a signal 1 is input to the second input terminal of the second logic OR unit (14) via the logic AND unit (12) and the third logic negation unit (13);

[0038] When one or both of the first input terminal and the second input terminal of the second logic OR unit (14) are 1, a signal 1 is input to the S terminal of the RS trigger (15), otherwise a signal 0 is input; when the S terminal input of the RS trigger is 0 and the R terminal input is 1, the primary frequency modulation input output signal (16) output by the RS trigger (15) is 1, and after the fourth logic NOT unit (17) takes negation, the primary frequency modulation exit output signal (18) is 0; the primary frequency modulation is put into use, and the signal is input to the analog switching selector (23);

[0039] S4, setting the analog quantity generator (19), when the primary frequency modulation is not put into use, the analog quantity switching selector (23) outputs the primary frequency modulation quantity instruction of this analog quantity generator (19);

[0040] S5, a linear converter (21) is set according to the results of the on-site primary frequency regulation test, and a first piecewise linear function generator (22) is set according to the requirements of the power grid. The frequency difference signal (20) is converted into a water flow instruction corresponding to the primary frequency regulation amount within the operating boundary of the unit through the linear converter (21) and the first piecewise linear function generator (22); when the unit is in the primary frequency regulation function, the analog switching selector (23) outputs the water flow instruction corresponding to the primary frequency regulation amount;

[0041] S6, setting the output speed regulator (24) according to the operating state of the unit so that the speed regulation rate of the primary frequency modulation instruction is within the operating boundary, and outputting the water flow rate instruction corresponding to the primary frequency modulation amount at this time, and inputting it into the third input terminal of the adder (29);

[0042] S7, setting a second piecewise linear function generator (27) according to the relationship between the actual load of the unit and the feed water flow in the boiler factory manual; setting a third piecewise linear function generator (28) according to the relationship between the main steam pressure deviation and the feed water flow; converting the boiler master control corresponding load output signal (25) into a corresponding feed water flow signal 1 through the second piecewise linear function generator (27); converting the main steam pressure deviation input signal (26) into a corresponding feed water flow signal 2 through the third piecewise linear function generator (28); adding the primary frequency modulation action amount and the feed water flow signal 1 / 2, and outputting the feed water flow set value;

[0043] S8, setting a fourth piecewise linear function generator (31); the fourth piecewise linear function generator (31) limits the minimum water flow value of the generator power signal (30); and compares it with the water flow set value obtained in step S7, taking the larger value as the final water flow signal to be fed forward to the water pump.

[0044] The beneficial effects of the present invention are as follows: the present invention changes the primary frequency modulation control logic, combines the primary frequency modulation action amount with the current main steam pressure deviation and important parameters on the boiler side for mathematical processing, and then feeds it forward to the steam pump for water supply control, so as to adjust the steam pressure fluctuation caused by the primary frequency modulation in advance, rather than passively adjusting it after monitoring the steam pressure fluctuation, thereby achieving early and accurate suppression of the steam pressure fluctuation generated by the secondary reheat unit in the process of participating in the primary frequency modulation of the power grid, reducing the main steam pressure fluctuation amplitude, shortening the adjustment time for the main steam pressure to return to stability, ensuring the primary frequency modulation performance while maintaining the safe and economical operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly describes the drawings required for the specific embodiments or the description of the prior art. Similar elements or parts are generally identified by similar reference numerals throughout the drawings. Elements or parts in the drawings are not necessarily drawn to scale.

[0046] Figure 1 It is the system principle diagram of the present invention;

[0047] Figure 2 is a flow chart of the method of the present invention;

[0048] Figure 3 The following is a comparison diagram of the main steam pressure before and after the optimization of the present invention;

[0049] Figure 4 This is a comparison diagram of the main steam pressure before and after the optimization of the present invention under working condition 2. DETAILED DESCRIPTION

[0050] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0051] It will be understood that when used in this specification and the appended claims, the terms “comprises” and “comprising” indicate the presence of described features, integers, steps, operations, elements and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0052] It should also be understood that the terms used in the present specification are only for the purpose of describing particular embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms unless the context clearly indicates otherwise.

[0053] It should be further understood that the term "and / or" used in the present description and appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0054] The steam turbine used in this embodiment is a 1000MW ultra-supercritical, double-reheat, single-shaft, five-cylinder, four-exhaust, double-back-pressure condensing steam turbine, model N1000-31 / 600 / 620 / 620. The main design parameters of the unit are shown in Table 1 below. The pressures (or vacuums) mentioned throughout the text are all absolute pressures.

[0055] The generator used in the embodiment is a water-hydrogen-hydrogen cooling steam turbine generator manufactured by Shanghai Electric Group Co., Ltd., model QFSN-100-2.

[0056] The host DCS specifically adopted in the embodiment is the EDPF-NT PLUS3.4 distributed control system of Guoneng Zhishen Control Technology Co., Ltd., and the DEH adopts the Ovation.3.7 distributed control system of Emerson Process Management Co., Ltd.

[0057] like Figure 1 As shown, a specific embodiment of the present invention provides a main steam pressure fluctuation suppression control system considering feedwater feedforward primary frequency modulation, including:

[0058] A single pulse generator (2), wherein an input terminal of the single pulse generator (2) inputs a primary frequency modulation input (DEH) input signal (1);

[0059] A soft keyboard (5), wherein an input end of the soft keyboard (5) inputs a CCS primary frequency modulation switching instruction input (4);

[0060] a first logic OR unit (3), wherein a first input end of the first logic OR unit (3) is connected to an output end of the single pulse generator (2), and a second input end of the second logic OR unit (3) is connected to a first output end of the soft keyboard (5);

[0061] A first logical NOT unit (9), wherein an input terminal of the first logical NOT unit (9) inputs a frequency difference quality bad input signal (7);

[0062] A time-delay disconnection algorithm (10), wherein the input end of the time-delay disconnection algorithm (10) is connected to the output end of the logical NOT unit (9);

[0063] A second logical NOT unit (11), wherein an input terminal of the second logical NOT unit (11) inputs an RB action input signal (8);

[0064] A logic AND unit (12), wherein a first input terminal of the logic AND unit (12) inputs a coordination mode CCS input signal (6), a second input terminal of the logic AND unit (12) is connected to an output terminal of the delayed disconnection algorithm (10), and a third input terminal of the logic AND unit (12) is connected to an output terminal of the second logic NOT unit (11);

[0065] a third logical NOT unit (13), wherein an input end of the third logical NOT unit (13) is connected to an output end of the logical AND unit (12);

[0066] a second logic OR unit (14), wherein a first input end of the second logic OR unit (14) is connected to a second output end of the soft keyboard (5), and a second input end of the second logic OR unit (14) is connected to an output end of the third logic NOT unit (13);

[0067] An RS trigger (15), wherein an S terminal of the RS trigger (15) is connected to an output terminal of the first logic OR unit (3), and an R terminal of the RS trigger (15) is connected to an output terminal of the second logic OR unit (14);

[0068] an analog quantity switching selector (23), wherein an input end of the analog quantity switching selector (23) is connected to a first output end of the RS trigger (15);

[0069] An analog quantity generator (19), wherein the analog quantity generator (19) is connected to the N terminal of the analog quantity switching selector (23),

[0070] A linear converter (21), wherein the frequency difference signal (20) is input to an input end of the linear converter (21);

[0071] a first piecewise linear function generator (22), wherein the input end of the first piecewise linear function generator (22) is connected to the output end of the linear converter (21), and the output end is connected to the Y end of the analog switching selector (23);

[0072] An output speed regulator (24), wherein an input end of the output speed regulator (24) is connected to an output end of the analog switching selector (23);

[0073] A second piecewise linear function generator (27), wherein an input end of the second piecewise linear function generator (27) inputs a boiler master control corresponding load output signal (25);

[0074] A third piecewise linear function generator (28), wherein the input end of the third piecewise linear function generator (28) receives a main steam pressure deviation input signal (26);

[0075] an adder (29), wherein a first input end of the adder (29) is connected to an output end of the third piecewise linear function generator (28), a second input end is connected to an output end of the second piecewise linear function generator (27), and a third input end is connected to an output end of the output speed controller (24);

[0076] a fourth piecewise linear function generator (31), wherein the generator power signal (30) is input to an input end of the fourth piecewise linear function generator (31);

[0077] A maximizer (32) has a first input end connected to the output end of the adder (29), a second input end connected to the output end of the fourth piecewise linear function generator (31), and an output end outputting a steam pump instruction to be fed forward to the water supply pump.

[0078] The system further comprises a fourth logical NOT unit (17), the input end of the fourth logical NOT unit (17) being connected to the second output end of the RS trigger (15), and the output end outputting a frequency modulation exit output signal (18). The RS trigger (15) further comprises a third output end, and the third output end of the RS trigger (15) outputs a frequency modulation input output signal (16).

[0079] A single pulser (2) is provided, and when the primary frequency modulation input (DEH) input signal (1) is 1, a signal 1 is input to the first input terminal of the first logic or unit (3). A delayed disconnection algorithm (10) is provided, and when the frequency difference quality data not collected is bad, the frequency difference quality bad input signal (7) is input as 0; or when the frequency difference quality data collected is bad, the frequency difference quality bad input signal (7) is input as 1 but does not last longer than the time limit set by the delayed disconnection algorithm (10). An output speed regulator (24) is provided according to the operating state of the unit so that the speed regulation rate of the primary frequency modulation instruction is within the operating boundary. The fourth piecewise linear function generator (31) limits the minimum water flow value of the motor power signal (30).

[0080] like Figure 2 As shown, the specific embodiment of the present invention also provides a main steam pressure fluctuation suppression control method considering feedwater feedforward primary frequency modulation, including the following steps:

[0081] Step S1, setting the default initial value of the single pulser (2) to 3S, and when the primary frequency modulation input (DEH) input signal (1) is 1, inputting a signal 1 to the first input terminal of the first logic OR unit (3);

[0082] Step S2, setting the CCS primary frequency modulation switching instruction input (4) to 1, inputting a signal 1 to the first input terminal of the second logic OR unit (14); inputting a signal 1 to the second input terminal of the first logic OR unit (3); the first logic OR unit (3) performs an OR operation on its first input terminal and the second input terminal, and when one or both of the input signals of the first input terminal and the second input terminal of the first logic OR unit (3) are 1, inputting a signal 1 to the S terminal of the RS trigger (15);

[0083] S3, set the coordination mode CCS input signal (6) to 1, input signal 1 to the first input terminal of the logic and unit (12); set the default initial value of the delay disconnection algorithm (10) to 3S, when the frequency difference quality that has not been collected has bad data, the frequency difference quality bad input signal (7) is input to 0, and after being inverted by the first logic negation unit (9), input signal 1 to the second input terminal of the logic and unit (12); or when the frequency difference quality that has been collected has bad data, the frequency difference quality bad input signal (7) is input to 1 but does not exceed the time limit set by the delay disconnection algorithm (10), input signal 1 to the second input terminal of the logic and unit (12);

[0084] When the auxiliary machine operates normally and no load shedding occurs, the RB action input signal (8) is 0, and after being negated by the second logic negation unit (11), a signal 1 is input to the third input terminal of the logic AND unit (12); when the input signals of the three input terminals of the logic AND unit (12) are all 1, a signal 1 is input to the second input terminal of the second logic OR unit (14) via the logic AND unit (12) and the third logic negation unit (13);

[0085] When one or both of the first input terminal and the second input terminal of the second logic OR unit (14) are 1, a signal 1 is input to the S terminal of the RS trigger (15), otherwise a signal 0 is input; when the S terminal input of the RS trigger is 0 and the R terminal input is 1, the primary frequency modulation input output signal (16) output by the RS trigger (15) is 1, and after the fourth logic NOT unit (17) takes negation, the primary frequency modulation exit output signal (18) is 0; the primary frequency modulation is put into use, and the signal is input to the analog switching selector (23);

[0086] S4, set the analog generator (19) to 0. When the primary frequency regulation is not put into operation, the analog switching selector (23) outputs the primary frequency regulation instruction of the analog generator (19). If the unit requires the primary frequency regulation function to be exited, 0 power adjustment can be performed.

[0087] S5, according to the results of the on-site primary frequency modulation test, the linear converter (21) is set, the primary frequency modulation coefficient K is set to 2, and the frequency difference signal is converted into a primary frequency modulation instruction within the unit operation boundary;

[0088] According to the requirements of the power grid, a first piecewise linear function generator (22) is set, and the set points are (286 t / h, 2800 r / min), (573 t / h, 2800 r / min), (1450 t / h, 3760 r / min), and (2660 t / h, 5223 r / min), and the primary frequency modulation instruction is converted into the corresponding water flow rate;

[0089] The frequency difference signal (20) is converted into a water flow instruction corresponding to the primary frequency modulation amount within the unit operation boundary through a linear converter (21) and a first piecewise linear function generator (22); when the unit is in the primary frequency modulation function, the analog switching selector (23) outputs the water flow instruction corresponding to the primary frequency modulation amount;

[0090] S6, according to the operating state of the unit, the output speed regulator (24) is set to 1000 r / min, so that the speed regulation rate of the primary frequency modulation instruction is within the operating boundary, and the water flow rate instruction corresponding to the primary frequency modulation amount at this time is output and input into the third input terminal of the adder (29);

[0091] S7, according to the relationship between the actual load and feed water volume of the unit in the boiler factory manual, set the second piecewise linear function generator (27), and set the points to (0MW, 738 t / h), (300MW, 738 t / h), (400MW, 972 t / h), (500MW, 1212 t / h), (750MW, 1866 t / h), (1000MW, 2533 t / h), (1050MW, 2658 t / h), (1100MW, 2770 t / h);

[0092] According to the relationship between the main steam pressure deviation and the feed water flow rate, a third piecewise linear function generator (28) is set, and the set points are (-2MPa, -40 t / h), (-1MPa, -35 t / h), (-0.5MPa, -25 t / h), (-0.2MPa, 0t / h), (0.2MPa, 0t / h), (0.5MPa, 25 t / h), (1MPa, 35 t / h), (2MPa, 40 t / h);

[0093] The boiler master control corresponding load output signal (25) is converted into a corresponding feedwater flow signal 1 by a second piecewise linear function generator (27); the main steam pressure deviation input signal (26) is converted into a corresponding feedwater flow signal 2 by a third piecewise linear function generator (28); the primary frequency modulation action amount is added to the feedwater flow signal 1 / 2, and the feedwater flow set value is output;

[0094] S8, set the fourth piecewise linear function generator (31), set the points to be (0MW, 700 t / h), (200MW, 700 t / h), (250MW, 700 t / h), (300MW, 840 t / h), (1100MW, 840 t / h); the fourth piecewise linear function generator (31) limits the minimum water flow value of the generator power signal (30); compares it with the water flow set value obtained in step S7, takes the larger value, and feeds it forward to the water pump as the final water flow signal.

[0095] Before and after applying the feedwater feedforward primary frequency modulation main steam pressure fluctuation suppression control system and method proposed in the present invention, a frequency modulation test was carried out to verify the effectiveness of the present invention, with the load variation range of ±60WM, the dead zone of ±0.033Hz, and the speed variation rate of 5%.

[0096] 1. The experimental steps of applying the present invention are as follows:

[0097] (1) Set parameters according to steps S1-S8 of the above method, start coordinated control, adjust the unit load to 80% Pe (800MW) under CCS control mode, and operate stably for 10 minutes;

[0098] (2) In the frequency regulation calculation logic, the forced speed difference is 10r / min, corresponding to a frequency difference of 0.167Hz. At this time, the corresponding primary frequency regulation load correction target is -53.2MW, waiting for the unit load to transition to a stable state;

[0099] (3) In the frequency regulation calculation logic, the speed difference is forced to be 0 r / min, corresponding to a frequency difference of 0 Hz. At this time, the corresponding primary frequency regulation load correction target is 0 MW, waiting for the unit load to transition to a stable state;

[0100] (4) In the frequency regulation calculation logic, the forced speed difference is -10r / min, corresponding to a frequency difference of -0.167Hz. At this time, the corresponding primary frequency regulation load correction target is 53.2MW, waiting for the unit load to transition to a stable state;

[0101] (5) In the frequency regulation calculation logic, the speed difference is forced to be 0 r / min, corresponding to a frequency difference of 0 Hz. At this time, the corresponding primary frequency regulation load correction target is 0 MW, waiting for the unit load to transition to a stable state;

[0102] (6) The fluctuation of the main steam pressure of the printer group is named after optimization.

[0103] 2. The test steps without using the control system and method proposed by the present invention are as follows:

[0104] (1) Start coordinated control and adjust the unit load to 80% Pe (800MW) under CCS control mode and operate stably for 10 minutes;

[0105] (2) In the frequency regulation calculation logic, the forced speed difference is 10r / min, corresponding to a frequency difference of 0.167Hz. At this time, the corresponding primary frequency regulation load correction target is -53.2MW, waiting for the unit load to transition to a stable state;

[0106] (3) In the frequency regulation calculation logic, the speed difference is forced to be 0 r / min, corresponding to a frequency difference of 0 Hz. At this time, the corresponding primary frequency regulation load correction target is 0 MW, waiting for the unit load to transition to a stable state;

[0107] (4) In the frequency regulation calculation logic, the forced speed difference is -10r / min, corresponding to a frequency difference of -0.167Hz. At this time, the corresponding primary frequency regulation load correction target is 53.2MW, waiting for the unit load to transition to a stable state;

[0108] (5) In the frequency regulation calculation logic, the speed difference is forced to be 0 r / min, corresponding to a frequency difference of 0 Hz. At this time, the corresponding primary frequency regulation load correction target is 0 MW, waiting for the unit load to transition to a stable state;

[0109] (6) Fluctuation of the main steam pressure of the printer group, named before optimization.

[0110] The forced speed difference of the unit before and after the optimization using the present invention is 10r / min, corresponding to a frequency difference of 0.167Hz. The comparison of the main steam pressure fluctuation under this working condition is shown in the figure. Figure 3 shown.

[0111] Depend on Figure 3 It can be seen that when the frequency difference is 0.167Hz, the maximum pressure fluctuation before optimization reaches 3.382MPa, and the adjustment time is 5 minutes and 20 seconds. After optimization, the maximum pressure fluctuation is 1.798MPa, and the adjustment time is 3 minutes and 12 seconds. Through optimization, the pressure fluctuation amplitude is reduced by 46.8%, and the adjustment time is shortened by 40%.

[0112] The forced speed difference of the unit before and after the optimization of the present invention is -10r / min, corresponding to a frequency difference of -0.167Hz. The main steam pressure fluctuation comparison under this working condition is as follows: Figure 4 shown.

[0113] Depend on Figure 4It can be seen that when the frequency difference is -0.167Hz, the maximum pressure fluctuation reaches 2.875MPa before optimization, and the adjustment time is 7 minutes and 30 seconds. After optimization, it becomes 2.089MPa, and the adjustment time is 3 minutes and 7 seconds. Through optimization, the pressure fluctuation amplitude is reduced by 27.3%, and the adjustment time is shortened by 58.4%.

[0114] The present invention can effectively suppress the main steam pressure fluctuation in the primary frequency regulation of the secondary reheat unit, so that the pressure fluctuation after the frequency regulation is reduced and restored to stability as soon as possible, thereby reducing the reverse regulation load of the main steam pressure deviation change to ensure the primary frequency regulation performance, and maintaining the safety and economy of the unit operation.

[0115] Those skilled in the art will appreciate that the units of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition of each example has been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0116] In the embodiments provided in the present application, it should be understood that the division of units is merely a logical function division, and there may be other division methods in actual implementation, for example, multiple units can be combined into one unit, one unit can be split into multiple units, or some features can be ignored, etc.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and description of the present invention.

Claims

1. Considering the feedwater feedforward primary frequency modulation main steam pressure fluctuation suppression control system, the characteristics are: include: A single pulse generator (2), wherein an input terminal of the single pulse generator (2) inputs a primary frequency modulation input (DEH) input signal (1); A soft keyboard (5), wherein an input end of the soft keyboard (5) inputs a CCS primary frequency modulation switching instruction input (4); a first logic OR unit (3), wherein a first input end of the first logic OR unit (3) is connected to an output end of the single pulse generator (2), and a second input end of the second logic OR unit (3) is connected to a first output end of the soft keyboard (5); A first logical NOT unit (9), wherein an input terminal of the first logical NOT unit (9) inputs a frequency difference quality bad input signal (7); A time-delay disconnection algorithm (10), wherein the input end of the time-delay disconnection algorithm (10) is connected to the output end of the logical NOT unit (9); A second logical NOT unit (11), wherein an input terminal of the second logical NOT unit (11) inputs an RB action input signal (8); A logic AND unit (12), wherein a first input terminal of the logic AND unit (12) inputs a coordination mode CCS input signal (6), a second input terminal of the logic AND unit (12) is connected to an output terminal of the delayed disconnection algorithm (10), and a third input terminal of the logic AND unit (12) is connected to an output terminal of the second logic NOT unit (11); a third logical NOT unit (13), wherein an input end of the third logical NOT unit (13) is connected to an output end of the logical AND unit (12); a second logic OR unit (14), wherein a first input end of the second logic OR unit (14) is connected to a second output end of the soft keyboard (5), and a second input end of the second logic OR unit (14) is connected to an output end of the third logic NOT unit (13); An RS trigger (15), wherein an S terminal of the RS trigger (15) is connected to an output terminal of the first logic OR unit (3), and an R terminal of the RS trigger (15) is connected to an output terminal of the second logic OR unit (14); an analog quantity switching selector (23), wherein an input end of the analog quantity switching selector (23) is connected to a first output end of the RS trigger (15); An analog quantity generator (19), wherein the analog quantity generator (19) is connected to the N terminal of the analog quantity switching selector (23), A linear converter (21), wherein the frequency difference signal (20) is input to an input end of the linear converter (21); a first piecewise linear function generator (22), wherein the input end of the first piecewise linear function generator (22) is connected to the output end of the linear converter (21), and the output end is connected to the Y end of the analog switching selector (23); An output speed regulator (24), wherein an input end of the output speed regulator (24) is connected to an output end of the analog switching selector (23); A second piecewise linear function generator (27), wherein an input end of the second piecewise linear function generator (27) inputs a boiler master control corresponding load output signal (25); A third piecewise linear function generator (28), wherein the input end of the third piecewise linear function generator (28) receives a main steam pressure deviation input signal (26); an adder (29), wherein a first input end of the adder (29) is connected to an output end of the third piecewise linear function generator (28), a second input end is connected to an output end of the second piecewise linear function generator (27), and a third input end is connected to an output end of the output speed controller (24); a fourth piecewise linear function generator (31), wherein the generator power signal (30) is input to an input end of the fourth piecewise linear function generator (31); A maximizer (32) has a first input end connected to the output end of the adder (29), a second input end connected to the output end of the fourth piecewise linear function generator (31), and an output end outputting a steam pump instruction to be fed forward to the water supply pump.

2. The main steam pressure fluctuation suppression control system considering feedwater feedforward primary frequency modulation according to claim 1 is characterized in that: The system further comprises a fourth logical NOT unit (17), the input end of the fourth logical NOT unit (17) being connected to the second output end of the RS trigger (15), and the output end outputting a frequency modulation exit output signal (18).

3. The main steam pressure fluctuation suppression control system considering feedwater feedforward primary frequency modulation according to claim 2 is characterized in that: The RS trigger (15) further comprises a third output terminal, and the third output terminal of the RS trigger (15) outputs a primary frequency modulation input output signal (16).

4. The main steam pressure fluctuation suppression control system considering feedwater feedforward primary frequency modulation according to claim 1 is characterized in that: A single pulser (2) is provided, and when a frequency modulation input (DEH) input signal (1) is 1, a signal 1 is input to a first input terminal of a first logic OR unit (3).

5. The main steam pressure fluctuation suppression control system considering feedwater feedforward primary frequency modulation according to claim 1 is characterized in that: A delay disconnection algorithm (10) is set, and when the frequency difference quality that has not been collected has bad data, the frequency difference quality bad input signal (7) is input to 0; or when the frequency difference quality that has been collected has bad data, the frequency difference quality bad input signal (7) is input to 1 but continues for no longer than the time limit set by the delay disconnection algorithm (10).

6. The main steam pressure fluctuation suppression control system considering feedwater feedforward primary frequency modulation according to claim 1 is characterized in that: The output speed regulator (24) is set according to the operating state of the unit so that the speed regulation rate of the primary frequency modulation instruction is within the operating boundary.

7. The main steam pressure fluctuation suppression control system considering feedwater feedforward primary frequency modulation according to claim 1 is characterized in that: The fourth piecewise linear function generator (31) limits the minimum water flow value of the motor power signal (30).

8. Considering the feedwater feedforward primary frequency modulation main steam pressure fluctuation suppression control method, the characteristics are: The following steps are involved: Step S1, setting a single pulser (2), when a frequency modulation input (DEH) input signal (1) is 1, inputting a signal 1 to a first input terminal of a first logic OR unit (3); Step S2, setting the CCS primary frequency modulation switching instruction input (4) to 1, inputting a signal 1 to the first input terminal of the second logic OR unit (14); inputting a signal 1 to the second input terminal of the first logic OR unit (3); the first logic OR unit (3) performs an OR operation on its first input terminal and the second input terminal, and when one or both of the input signals of the first input terminal and the second input terminal of the first logic OR unit (3) are 1, inputting a signal 1 to the S terminal of the RS trigger (15); S3, setting the coordination mode CCS input signal (6) to 1, inputting signal 1 to the first input terminal of the logic AND unit (12); A delayed disconnection algorithm (10) is set, and when the frequency difference quality data that has not been collected is bad, the frequency difference quality bad input signal (7) is input as 0, and after being inverted by the first logical NOT unit (9), a signal 1 is input to the second input end of the logical AND unit (12); or when the frequency difference quality data that has been collected is bad, the frequency difference quality bad input signal (7) is input as 1 but continues for a period that does not exceed the time limit set by the delayed disconnection algorithm (10), a signal 1 is input to the second input end of the logical AND unit (12); When the auxiliary machine operates normally and no load shedding occurs, the RB action input signal (8) is 0, and after being negated by the second logic negation unit (11), a signal 1 is input to the third input terminal of the logic AND unit (12); when the input signals of the three input terminals of the logic AND unit (12) are all 1, a signal 1 is input to the second input terminal of the second logic OR unit (14) via the logic AND unit (12) and the third logic negation unit (13); When one or both of the first input terminal and the second input terminal of the second logic OR unit (14) are 1, a signal 1 is input to the S terminal of the RS trigger (15), otherwise a signal 0 is input; when the S terminal input of the RS trigger is 0 and the R terminal input is 1, the primary frequency modulation input output signal (16) output by the RS trigger (15) is 1, and after the fourth logic NOT unit (17) takes negation, the primary frequency modulation exit output signal (18) is 0; the primary frequency modulation is put into use, and the signal is input to the analog switching selector (23); S4, setting the analog quantity generator (19), when the primary frequency modulation is not put into use, the analog quantity switching selector (23) outputs the primary frequency modulation quantity instruction of this analog quantity generator (19); S5, a linear converter (21) is set according to the results of the on-site primary frequency regulation test, and a first piecewise linear function generator (22) is set according to the requirements of the power grid. The frequency difference signal (20) is converted into a water flow instruction corresponding to the primary frequency regulation amount within the operating boundary of the unit through the linear converter (21) and the first piecewise linear function generator (22); when the unit is in the primary frequency regulation function, the analog switching selector (23) outputs the water flow instruction corresponding to the primary frequency regulation amount; S6, setting the output speed regulator (24) according to the operating state of the unit so that the speed regulation rate of the primary frequency modulation instruction is within the operating boundary, and outputting the water flow rate instruction corresponding to the primary frequency modulation amount at this time, and inputting it into the third input terminal of the adder (29); S7, setting a second piecewise linear function generator (27) according to the relationship between the actual load of the unit and the feed water flow in the boiler factory manual; setting a third piecewise linear function generator (28) according to the relationship between the main steam pressure deviation and the feed water flow; converting the boiler master control corresponding load output signal (25) into a corresponding feed water flow signal 1 through the second piecewise linear function generator (27); converting the main steam pressure deviation input signal (26) into a corresponding feed water flow signal 2 through the third piecewise linear function generator (28); adding the primary frequency modulation action amount and the feed water flow signal 1 / 2, and outputting the feed water flow set value; S8, setting a fourth piecewise linear function generator (31); the fourth piecewise linear function generator (31) limits the minimum water flow value of the generator power signal (30); and compares it with the water flow set value obtained in step S7, taking the larger value as the final water flow signal to be fed forward to the water pump.

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