A boiler master control system and method for a supercritical unit during primary frequency modulation operation

Abstract

The invention discloses a boiler master control system for a supercritical unit during primary frequency modulation, which belongs to the field of thermal power generation process control and solves the problem of primary frequency modulation parameter overshoot. The invention comprises a dead zone controller, a function generator, an inertia module, an adder, a subtractor, a main control PID, an adder and a fast differential feedforward subsystem. The dead zone controller, the function generator, the inertia module and the adder are connected in series in sequence. The output end of the adder is connected to the subtractor, and the subtractor, the main control PID and the adder are connected in series in sequence. The dead zone controller is connected to the fast differential feedforward subsystem. The control method comprises the following steps: forming a predicted value of the change amount of the main steam pressure and a new main steam pressure setting value, performing a difference between the actual input main steam pressure value and the value, and sending the difference to the main control PID, and then adding the adder and the boiler main control feedforward signal to form a boiler main control output signal to control the action of the boiler. The corrected instruction is obtained through the fast differential feedforward subsystem. The overshoot and overlimit of the parameters in the late stage and after the primary frequency modulation is avoided.

Description

Technical Field

[0001] The invention belongs to the field of thermal power generation process control, and relates to a boiler master control system and method during primary frequency modulation of a supercritical unit. Background Art

[0002] With the access of a series of clean energy such as wind energy and solar energy to the power system, their randomness and volatility have brought great challenges to the stable output of the power grid. For a long time in the future, my country will still be dominated by thermal power generation. This puts higher requirements on the flexibility of the operation of high-parameter and large-capacity thermal power units. The large delay and large inertia on the boiler side of coal-fired thermal power units seriously affect the flexible operation of the unit. Especially when the grid frequency changes, the unit load changes greatly in a short time, resulting in rapid changes in the main steam pressure, and when the grid frequency returns to normal, the main steam pressure will change rapidly in the opposite direction. In this process, the unit pressure controller, that is, the boiler main control PID controller under the coordination mode of the machine and the boiler, will change the output greatly and repeatedly under the proportional and integral action due to the change of the main steam pressure. However, due to the large delay and large inertia characteristics of the boiler side, it often further causes the main steam pressure to overshoot after the frequency is restored, and the unit is unstable. For example, when the grid frequency first drops, the unit load increases and the main steam pressure drops. At this time, the boiler master PID controller increases its output to increase the main steam pressure. Since the proportional and integral effects are slower than the primary frequency modulation speed, the boiler side’s response to the increase in the boiler master output often begins to manifest when the frequency recovers and the main steam pressure rises, which greatly increases the amplitude of the main steam pressure increase. In severe cases, it causes the boiler to be over-pressurized, which is very dangerous. Therefore, for the primary frequency modulation action, the boiler master PID controller is often not required to respond excessively to the main steam pressure. Only relying on the appropriate feedforward effect can meet the role of supplementing the boiler heat storage.

[0003] In the prior art, the Chinese invention patent application "A method, system and medium for optimizing the primary frequency regulation of a thermal power unit" with the application publication number CN110865536A discloses a method, system and medium for optimizing the primary frequency regulation of a thermal power unit. The method of the present invention includes generating an additional pressure setting value according to the primary frequency regulation action and the input status; superimposing the additional pressure setting value on the main steam pressure setting value to obtain a new main steam pressure setting value, and outputting the new main steam pressure setting value as the main steam pressure setting value parameter of the primary frequency regulation control system of the thermal power unit. The present invention flexibly designs the additional setting value of the main steam pressure, appropriately increases the main steam pressure on the basis of normal sliding pressure or constant pressure operation, and quickly acts on fuel, water supply and air volume control through frequency difference, so as to achieve the purpose of heat storage and rapid release of heat load, and maintain the stability of the main steam pressure while meeting the rapid response of the primary frequency regulation, so as to effectively improve the primary frequency regulation capability of the thermal power unit.

[0004] However, the technical solution of the above-mentioned Chinese invention patent application still has the phenomenon of parameter overshoot and over-limit in the later stage and after the end of a frequency modulation. Summary of the invention

[0005] The technical problem to be solved by the present invention is how to effectively avoid the problem of parameter overshoot and overlimit in the late stage and after completion of a frequency modulation.

[0006] The present invention solves the above technical problems through the following technical solutions.

[0007] A boiler master control system for a supercritical unit during primary frequency modulation operation comprises: a dead zone controller (1), a first function generator (2), a first inertia module (3), a first adder (4), a first subtractor (5), a main control PID (6), a second adder (7), and a fast differential feedforward subsystem (8); the dead zone controller (1), the first function generator (2), the first inertia module (3), and the first adder (4) are sequentially connected in series; the output end of the first adder (4) is connected to the first subtractor (5), and the first subtractor (5), the main control PID (6), and the second adder (7) are sequentially connected in series; the dead zone controller (1) is connected to the fast differential feedforward subsystem (8); the control system During a frequency modulation operation, the grid frequency signal passes through the dead zone controller (1) and is sequentially input into the first function generator (2) and the first inertia module (3) to form a predicted value of the change in the main steam pressure, and then passes through the first adder (4) to add the predicted value to the original main steam pressure setting value to form a new main steam pressure setting value; the new main steam pressure setting value is input into the first subtractor (5), and is subtracted from the input actual main steam pressure value, and the difference signal is sent to the main control PID (6), and then passes through the second adder (7) to add the boiler main control feedforward signal to form a boiler main control output signal to control the operation of the boiler; at the same time, the grid frequency signal passes through the dead zone controller (1) and is input into the fast differential feedforward subsystem (8), and is added to the pre-correction instruction to obtain the post-correction instruction.

[0008] During the primary frequency modulation action, the grid frequency signal passes through the function generator to obtain the predicted final change amplitude of the main steam pressure, and then passes through the first-order inertia link to simulate the change process of the main steam pressure, which is first fast and then slow until it stabilizes. The actual main steam pressure is fitted in time, and then added to the original main steam pressure setting value through an adder to obtain a new main steam pressure setting value during the primary frequency modulation action; the new main steam pressure setting value is basically consistent with the direction and amplitude of the actual main steam pressure change. During the primary frequency modulation action, the output of the main PID controller changes little, and the boiler heat storage is basically compensated by the feedforward instruction of the boiler master control, which effectively avoids parameter overshoot and over-limit in the late stage and after the end of the primary frequency modulation.

[0009] As a further improvement of the technical solution of the present invention, the fast differential feedforward subsystem (8) includes a water flow fast differential feedforward subsystem and / or a fuel quantity fast differential feedforward subsystem and / or a total air volume fast differential feedforward subsystem.

[0010] As a further improvement of the technical solution of the present invention, the water supply flow fast differential feedforward subsystem comprises: a second subtractor (80), a second function generator (81), a third adder (82), and a second inertia module (83); the second inertia module (83), the second subtractor (80), the second function generator (81), and the third adder are connected in series in sequence; the power grid frequency signal passes through the dead zone controller (1) and is input into the second inertia module (83) and the second subtractor (80); the signal after passing through the second inertia module (83) is then input into the second subtractor (80), and is subtracted from the power grid frequency signal directly input into the second subtractor 80 after passing through the dead zone controller (1); the difference is input into the second function generator (81), and is added to the water supply flow instruction before correction through the third adder (82) to obtain the water supply flow instruction.

[0011] As a further improvement of the technical solution of the present invention, the fuel quantity fast differential feedforward subsystem comprises: a third subtractor (90), a third function generator (91), a fourth adder (92), and a third inertia module (93); the third inertia module (93), the third subtractor (90), the third function generator (91), and the fourth adder (92) are connected in series in sequence; the grid frequency signal passes through the dead zone controller (1), is input into the third inertia module (93) and the third subtractor (90), and is input into the third subtractor (90) after passing through the third inertia module (93), and is subtracted from the grid frequency signal directly input into the third subtractor (90) after passing through the dead zone controller (1), and the difference is sent to the third function generator (91), and is added to the pre-correction fuel quantity instruction through the fourth adder (92) to obtain the total fuel quantity instruction.

[0012] As a further improvement of the technical solution of the present invention, the total air volume fast differential feedforward subsystem comprises: a fourth subtractor (100), a fourth function generator (101), a fifth adder (102), and a fourth inertia module (103); the fourth inertia module (103), the fourth subtractor (100), the fourth function generator (101), and the fifth adder (102) are connected in series in sequence; the power grid frequency signal passes through the dead zone controller (1), is input into the fourth inertia module (103) and the fourth subtractor (100), passes through the fourth inertia module (103), and is then input into the fourth subtractor (100), where it is subtracted from the power grid frequency signal directly input into the fourth subtractor (100) after passing through the dead zone controller (1), and the difference is input into the fourth function generator (101), and is added to the total air volume instruction before correction through the fifth adder (102) to obtain the total air volume instruction.

[0013] As a further improvement of the technical solution of the present invention, the formula of the first function generator (2) is:

[0014]

[0015] Where x is the input grid frequency signal.

[0016] As a further improvement of the technical solution of the present invention, the transfer function formula of the first inertial module (3) is:

[0017]

[0018] Where G(s) is the transfer function of the inertial module, T is the time constant of the inertial link, and s is the Laplace transform.

[0019] A control method for a boiler master control system when using the primary frequency modulation action of a supercritical unit, comprising the following steps:

[0020] Step 1: During a frequency modulation operation, the grid frequency passes through the dead zone controller (1) and is sequentially input into the first function generator (2) and the first inertia module (3) to form a predicted value of the change in the main steam pressure;

[0021] Step 2: The predicted value of the change in the main steam pressure is then added to the original main steam pressure setting value by the first adder (4) to form a new main steam pressure setting value;

[0022] Step 3: The new main steam pressure setting value is input into the first subtractor (5), and the difference is made with the input actual main steam pressure value. The difference signal is sent to the main control PID (6), and then added to the boiler main control feedforward signal through the second adder (7) to form the boiler main control output signal to control the operation of the boiler;

[0023] Step 4: After the grid frequency signal passes through the dead zone controller (1), it is input into the fast differential feedforward subsystem (8) and added to the pre-correction instruction to obtain the post-correction instruction.

[0024] As a further improvement of the technical solution of the present invention, the formula of the first function generator (2) is:

[0025]

[0026] Where x is the input grid frequency signal.

[0027] As a further improvement of the technical solution of the present invention, the transfer function formula of the first inertial module (3) is:

[0028]

[0029] Where G(s) is the transfer function of the inertial module, T is the time constant of the inertial link, and s is the Laplace transform.

[0030] The advantages of the present invention are:

[0031] (1) During the primary frequency modulation, the grid frequency signal is passed through a function generator to obtain the predicted final change amplitude of the main steam pressure, and then passed through a first-order inertia link to simulate the change process of the main steam pressure, which is first fast and then slow and finally stable. The actual main steam pressure is fitted in time, and then added to the original main steam pressure setting value through an adder to obtain a new main steam pressure setting value during the primary frequency modulation. The new main steam pressure setting value is basically consistent with the direction and amplitude of the actual main steam pressure change. During the primary frequency modulation, the output of the main PID controller changes little, and the boiler heat storage is basically compensated by the feedforward command of the boiler master control, which effectively avoids parameter overshoot and over-limit in the late stage and after the primary frequency modulation.

[0032] (2) The fast differential feedforward subsystem of the primary frequency modulation compensates for the boiler air supply, fuel, and water supply instructions. This feedforward can quickly increase or decrease the output of the corresponding subsystem at the beginning and end of the primary frequency modulation, and can dynamically balance the heat storage disturbance during the primary frequency modulation, further avoiding parameter overshoot and over-limit in the late stage and after the end of the primary frequency modulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a structural diagram of the boiler master control system during the primary frequency modulation action of the supercritical unit according to an embodiment of the present invention;

[0034] Figure 2 It is an implementation structure diagram of a boiler master control system including a feedwater flow rate fast differential feedforward subsystem during a primary frequency modulation action of a supercritical unit according to an embodiment of the present invention;

[0035] Figure 3 It is an implementation structure diagram of a boiler master control system including a fuel quantity fast differential feedforward subsystem during a primary frequency modulation action of a supercritical unit according to an embodiment of the present invention;

[0036] Figure 4 It is a structural diagram of a boiler master control system including a total air volume fast differential feedforward subsystem during a primary frequency modulation action of a supercritical unit according to an embodiment of the present invention;

[0037] Figure 5 It is a structural diagram of a boiler master control system including a feedwater flow rate fast differential feedforward subsystem and a fuel amount fast differential feedforward subsystem during a primary frequency modulation action of a supercritical unit in an embodiment of the present invention;

[0038] Figure 6 It is a structural diagram of a feedwater flow rate fast differential feedforward subsystem and a total air volume fast differential feedforward subsystem of a boiler master control system during a primary frequency modulation action of a supercritical unit in an embodiment of the present invention;

[0039] Figure 7 It is a structural diagram of a fuel quantity fast differential feedforward subsystem and a total air volume fast differential feedforward subsystem of a boiler master control system during a primary frequency modulation action of a supercritical unit in an embodiment of the present invention;

[0040] Figure 8 It is an implementation structure diagram of the boiler master control system during the primary frequency modulation action of the supercritical unit in an embodiment of the present invention, which includes a feed water flow fast differential feedforward subsystem, a fuel quantity fast differential feedforward subsystem, and a total air volume fast differential feedforward subsystem. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0042] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific embodiments:

[0043] Embodiment 1

[0044] like Figure 1As shown, a boiler master control system for a supercritical unit during primary frequency modulation action includes: a dead zone controller 1, a first function generator 2, a first inertia module 3, a first adder 4, a first subtractor 5, a main control PID 6, a second adder 7, and a fast differential feedforward subsystem 8; the dead zone controller 1, the first function generator 2, the first inertia module 3, and the first adder 4 are sequentially connected in series; the output end of the first adder 4 is connected to the first subtractor 5, and the first subtractor 5, the main control PID 6, and the second adder 7 are sequentially connected in series; the dead zone controller 1 is connected to the fast differential feedforward subsystem 8.

[0045] During a frequency modulation action, the grid frequency signal, on the one hand, passes through the dead zone controller 1, and is sequentially input into the first function generator 2 and the first inertia module 3 to form a predicted value of the change in the main steam pressure, and then passes through the first adder 4 to add the predicted value to the original main steam pressure setting value to form a new main steam pressure setting value; the new main steam pressure setting value is input into the first subtractor 5, and is subtracted from the input actual main steam pressure value, and the difference signal is sent to the main control PID 6, and then passes through the second adder 7 to add the boiler main control feedforward signal to form a boiler main control output signal to control the action of the boiler; on the other hand, the grid frequency signal passes through the dead zone controller 1, and is input into the fast differential feedforward subsystem 8, and is added to the pre-correction instruction to obtain the corrected instruction.

[0046] The formula of the function generator is:

[0047]

[0048] Where x is the input grid frequency signal.

[0049] The transfer function formula of the inertial module is:

[0050]

[0051] Where G(s) is the transfer function of the inertial module, T is the time constant of the inertial link, and s is the Laplace transform.

[0052] like Figure 2-8 As shown, the fast differential feedforward subsystem 8 includes three subsystems: a fast differential feedforward subsystem for water flow, a fast differential feedforward subsystem for fuel quantity, and a fast differential feedforward subsystem for total air volume; or the fast differential feedforward subsystem 8 includes any one or two of the three subsystems: a fast differential feedforward subsystem for water flow, a fast differential feedforward subsystem for fuel quantity, and a fast differential feedforward subsystem for total air volume.

[0053] like Figure 2As shown, the water flow fast differential feedforward subsystem includes: a second subtractor 80, a second function generator 81, a third adder 82, and a second inertia module 83; the second inertia module 83, the second subtractor 80, the second function generator 81, and the third adder 82 are connected in series in sequence.

[0054] After passing through the dead zone controller 1, the grid frequency signal is input into the second inertia module 83 and the second subtractor 80. The signal after passing through the second inertia module 83 is then input into the second subtractor 80, and is subtracted from the grid frequency signal after passing through the dead zone controller 1 directly input into the second subtractor 80. The difference is sent to the second function generator 81, and is added to the water supply flow command before correction through the third adder 82 to obtain the water supply flow command.

[0055] like Figure 3 As shown, the fuel quantity fast differential feedforward subsystem includes: a third subtractor 90, a third function generator 91, a fourth adder 92, and a third inertia module 93; the third inertia module 93, the third subtractor 90, the third function generator 91, and the fourth adder 92 are connected in series in sequence.

[0056] After passing through the dead zone controller 1, the grid frequency signal is input into the third inertia module 93 and the third subtractor 90. The signal after passing through the third inertia module 93 is then input into the third subtractor 90, and is subtracted from the grid frequency signal after passing through the dead zone controller 1 directly input into the third subtractor 90. The difference is sent to the third function generator 91, and is added to the pre-correction fuel quantity instruction through the fourth adder 92 to obtain the total fuel quantity instruction.

[0057] like Figure 4 As shown, the total air volume fast differential feedforward subsystem includes: a fourth subtractor 100, a fourth function generator 101, a fifth adder 102, and a fourth inertia module 103; the fourth inertia module 103, the fourth subtractor 100, the fourth function generator 101, and the fifth adder 102 are connected in series in sequence.

[0058] After passing through the dead zone controller 1, the grid frequency signal is input into the fourth inertia module 103 and the fourth subtractor 100. The signal after passing through the fourth inertia module 103 is then input into the fourth subtractor 100, and is subtracted from the grid frequency signal after passing through the dead zone controller 1 directly input into the fourth subtractor 100. The difference is sent to the fourth function generator 101, and is added to the total air volume instruction before correction through the fifth adder 102 to obtain the total air volume instruction.

[0059] During a frequency regulation action, when the grid frequency is at a high frequency (greater than 50.033Hz), the unit load needs to be reduced quickly. At this time, the opening of the high-pressure regulating valve of the steam turbine is reduced, and the change law of the boiler main steam pressure is: first it rises rapidly, and then the rising speed gradually slows down until it is stable. If the grid frequency does not recover, the main steam pressure will gradually return to the starting value (basically equivalent to the set value) under the coordinated control of the unit; when the grid frequency is at a low frequency (less than 49.067Hz), the unit load needs to be increased quickly. At this time, the opening of the high-pressure regulating valve of the steam turbine is increased, and the change law of the boiler main steam pressure is: first it drops rapidly, and then the dropping speed gradually slows down until it is stable. If the grid frequency does not recover, the main steam pressure will gradually return to the starting value (basically equivalent to the set value) under the coordinated control of the unit.

[0060] In fact, the grid frequency will generally recover within 1 to 2 minutes after deviating from the normal value, which is equivalent to two disturbances in the control system. The first is the frequency deviation disturbance, and the second is the frequency recovery disturbance. After the first disturbance, if the main steam pressure set value does not change, the main control PID will quickly adjust the control system. Due to the large delay characteristics of the boiler, the system will aggravate the second disturbance under the influence of the boiler lag.

[0061] During the primary frequency modulation action, the grid frequency signal passes through the function generator to obtain the predicted final change amplitude of the main steam pressure, and then passes through the first-order inertia link to simulate the change process of the main steam pressure, which is first fast and then slow until it stabilizes. The actual main steam pressure is fitted in time, and then added to the original main steam pressure setting value through an adder to obtain a new main steam pressure setting value during the primary frequency modulation action; the new main steam pressure setting value is basically consistent with the direction and amplitude of the actual main steam pressure change. During the primary frequency modulation action, the output of the main PID controller changes little, and the boiler heat storage is basically compensated by the feedforward instruction of the boiler master control, which effectively avoids parameter overshoot and over-limit in the late stage and after the end of the primary frequency modulation.

[0062] The fast differential feedforward subsystem of the primary frequency modulation compensates for the boiler air supply, fuel and water supply instructions. The feedforward can quickly increase or decrease the output of the corresponding subsystem at the beginning and end of the primary frequency modulation, and can dynamically balance the heat storage disturbance during the primary frequency modulation, further avoiding parameter overshoot and over-limit in the late stage and after the end of the primary frequency modulation.

[0063] The present invention also provides a boiler master control method during a primary frequency modulation action of a supercritical unit, comprising the following steps:

[0064] 1) During a frequency modulation action, the grid frequency signal passes through the dead zone controller 1 and is sequentially input into the first function generator 2 and the first inertia module 3 to form a predicted value of the change in the main steam pressure.

[0065] 2) Then the first adder 4 adds the original main steam pressure setting value to form a new main steam pressure setting value;

[0066] 3) The new main steam pressure setting value is input into the first subtractor 5, and the difference is made with the input actual main steam pressure value. The difference signal is sent to the main control PID 6, and then added to the boiler main control feedforward signal through the second adder 7 to form the boiler main control output signal to control the action of the boiler;

[0067] 4) After passing through the dead zone controller 1, the grid frequency signal is input into the fast differential feedforward subsystem 8, and is added to the pre-correction instruction to obtain the post-correction instruction.

[0068] The formula of the function generator is:

[0069]

[0070] Where x is the input grid frequency signal.

[0071] The transfer function formula of the inertial module is:

[0072]

[0073] Where G(s) is the transfer function of the inertial module, T is the time constant of the inertial link, and s is the Laplace transform.

[0074] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A boiler master control system for a supercritical unit during primary frequency modulation, characterized in that: include: A dead zone controller (1), a first function generator (2), a first inertia module (3), a first adder (4), a first subtractor (5), a main control PID (6), a second adder (7), and a fast differential feedforward subsystem (8); the dead zone controller (1), the first function generator (2), the first inertia module (3), and the first adder (4) are sequentially connected in series; the output end of the first adder (4) is connected to the first subtractor (5), and the first subtractor (5), the main control PID (6), and the second adder (7) are sequentially connected in series; the dead zone controller (1) is connected to the fast differential feedforward subsystem (8); during a frequency modulation operation of the control system, the grid frequency signal The signal is input into the first function generator (2) and the first inertia module (3) in sequence after passing through the dead zone controller (1) to form a predicted value of the change in the main steam pressure, and then added to the original main steam pressure setting value through the first adder (4) to form a new main steam pressure setting value; the new main steam pressure setting value is input into the first subtractor (5), and the difference is made with the input actual main steam pressure value, and the difference signal is sent to the main control PID (6), and then added to the boiler main control feedforward signal through the second adder (7) to form a boiler main control output signal to control the operation of the boiler; at the same time, the grid frequency signal is input into the fast differential feedforward subsystem (8) after passing through the dead zone controller (1), and is added to the pre-correction instruction to obtain the post-correction instruction.

2. The boiler master control system for a supercritical unit during primary frequency modulation according to claim 1, characterized in that: The fast differential feedforward subsystem (8) comprises a water flow fast differential feedforward subsystem and / or a fuel quantity fast differential feedforward subsystem and / or a total air volume fast differential feedforward subsystem.

3. The boiler master control system for a supercritical unit during primary frequency modulation according to claim 2, characterized in that: The water supply flow fast differential feedforward subsystem comprises: a second subtractor (80), a second function generator (81), a third adder (82), and a second inertia module (83); the second inertia module (83), the second subtractor (80), the second function generator (81), and the third adder are connected in series in sequence; the power grid frequency signal passes through the dead zone controller (1) and is input into the second inertia module (83) and the second subtractor (80); the signal after passing through the second inertia module (83) is then input into the second subtractor (80), and is subtracted from the power grid frequency signal directly input into the second subtractor 80 after passing through the dead zone controller (1); the difference is input into the second function generator (81), and is added to the water supply flow instruction before correction through the third adder (82) to obtain the water supply flow instruction.

4. The boiler master control system for a supercritical unit during primary frequency modulation according to claim 2, characterized in that: The fuel quantity fast differential feedforward subsystem comprises: a third subtractor (90), a third function generator (91), a fourth adder (92), and a third inertia module (93); the third inertia module (93), the third subtractor (90), the third function generator (91), and the fourth adder (92) are connected in series in sequence; the grid frequency signal passes through the dead zone controller (1), is input into the third inertia module (93) and the third subtractor (90), passes through the third inertia module (93), and is then input into the third subtractor (90), where it is subtracted from the grid frequency signal directly input into the third subtractor (90) after passing through the dead zone controller (1), and the difference is input into the third function generator (91), and is then added to the pre-corrected fuel quantity instruction through the fourth adder (92) to obtain a total fuel quantity instruction.

5. The boiler master control system for a supercritical unit during primary frequency modulation according to claim 2, characterized in that: The total air volume fast differential feedforward subsystem comprises: a fourth subtractor (100), a fourth function generator (101), a fifth adder (102), and a fourth inertia module (103); the fourth inertia module (103), the fourth subtractor (100), the fourth function generator (101), and the fifth adder (102) are sequentially connected in series; the power grid frequency signal passes through the dead zone controller (1), is input into the fourth inertia module (103) and the fourth subtractor (100), passes through the fourth inertia module (103), and is then input into the fourth subtractor (100), where the difference is made with the power grid frequency signal directly input into the fourth subtractor (100) after passing through the dead zone controller (1), and the difference is sent to the fourth function generator (101), and is added to the total air volume instruction before correction through the fifth adder (102) to obtain the total air volume instruction.

6. The boiler master control system for a supercritical unit during primary frequency modulation according to claim 1, characterized in that: The formula of the first function generator (2) is: Where x is the input grid frequency signal.

7. The boiler master control system for a supercritical unit during primary frequency modulation according to claim 1, characterized in that: The transfer function formula of the first inertial module (3) is: Where G(s) is the transfer function of the inertial module, T is the time constant of the inertial link, and s is the Laplace transform.

8. The control method of the boiler master control system during the primary frequency modulation operation of the supercritical unit according to any one of claims 1 to 7 comprises the following steps: Step 1: During a frequency modulation operation, the grid frequency passes through the dead zone controller (1) and is sequentially input into the first function generator (2) and the first inertia module (3) to form a predicted value of the change in the main steam pressure; Step 2: The predicted value of the change in the main steam pressure is then added to the original main steam pressure setting value by the first adder (4) to form a new main steam pressure setting value; Step 3: The new main steam pressure setting value is input into the first subtractor (5), and the difference is made with the input actual main steam pressure value. The difference signal is sent to the main control PID (6), and then added to the boiler main control feedforward signal through the second adder (7) to form the boiler main control output signal to control the operation of the boiler; Step 4: After the grid frequency signal passes through the dead zone controller (1), it is input into the fast differential feedforward subsystem (8) and added to the pre-correction instruction to obtain the post-correction instruction.

9. The control method according to claim 8, characterized in that: The formula of the first function generator (2) is: Where x is the input grid frequency signal.

10. The control method according to claim 8, characterized in that: The transfer function formula of the first inertial module (3) is: Where G(s) is the transfer function of the inertial module, T is the time constant of the inertial link, and s is the Laplace transform.

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