Negative acceleration device, method of water level control signal, and boiler water level control system

Abstract

The present application discloses a negative acceleration device, method and boiler water level control system for water level control signals. The negative acceleration device includes a positive feedback accelerator, a differentiator and a negative output controller; the positive feedback accelerator is used to accelerate the water level control signal to obtain an acceleration signal; the differentiator is used to convert the acceleration signal to generate a differential signal; the negative output controller is used to extract the negative acceleration signal in the differential signal. The negative acceleration device performs negative acceleration on the water level control signal, so that the negative pole signal with a downward trend in the water level control signal is output in advance, thereby performing negative over-water level control in advance. That is, the positive feedback accelerator can play a role in signal acceleration, so as to accompany the acceleration effect at the beginning of zero deviation, reduce control lag, and thus solve the negative over-water level problem existing in the boiler water level control system and enhance the control effect.

Description

Technical Field

[0001] This application relates to the technical field of process control of thermal power units, and particularly to a negative acceleration device and method for water level control signals and a boiler water level control system. Background Art

[0002] In the practice of process control of thermal power units, in the boiler water level control system of thermal power units, the problem of over-water level of the boiler water level often occurs. Relatively speaking, the problem of negative over-water level (i.e., the boiler water level is lower than the given value) is more serious. If the water level is too low, it will damage the steam-water cycle and may cause the boiler to explode in severe cases.

[0003] Currently, for the problem of negative over-water level of the boiler water level, the existing technology adopts a one-position control method. When the negative deviation of the boiler water level exceeds a certain amplitude, that is, when the boiler water level reaches the low liquid level, the water supply valve increases an opening degree to control the water level balance. However, it takes a certain amount of time for the boiler water level to change from zero deviation to a certain negative deviation, resulting in control lag and limited control effect. Summary of the Invention

[0004] This application provides a negative acceleration device, method for water level control signals and a boiler water level control system to solve the technical problem of current boiler water level control lag.

[0005] To solve the above technical problem, in the first aspect, this application provides a negative acceleration device for water level control signals, including a positive feedback accelerator, a differentiator and a negative output controller;

[0006] The positive feedback accelerator is used to accelerate the water level control signal to obtain an acceleration signal;

[0007] The differentiator is used to convert the acceleration signal to generate a differential signal;

[0008] The negative output controller is used to extract the negative acceleration signal from the differential signal.

[0009] Preferably, the water level control signal is the deviation signal between the boiler water level signal and the boiler water level given signal of the boiler water level control system.

[0010] Preferably, the positive feedback accelerator includes a positive feedback link, an integral accelerator and an integral limiter;

[0011] The positive feedback link is used to control the acceleration of the integral accelerator;

[0012] The integral accelerator is used to accelerate the water level control signal to generate an acceleration signal;

[0013] The integral limiter is used to limit the acceleration signal output by the integral accelerator.

[0014] Preferably, the integral accelerator is:

[0015]

[0016] where I(s) is the transfer function of the integral accelerator, s is the Laplace operator, and T I is the integral time constant of the integral accelerator.

[0017] The integral limiter is:

[0018]

[0019] where I(t) is the output signal of the integral accelerator, and PV IN (t) is the water level control signal.

[0020] Preferably, the differentiator:

[0021]

[0022] where D(s) is the transfer function of the differentiator, T D is the differentiation time constant of the differentiator, s is the Laplace operator, and K D is the gain of the differentiator.

[0023] Preferably, the negative output controller is:

[0024]

[0025] where NOC(t) is the output signal of the negative output controller, and D(t) is the output signal of the differentiator.

[0026] In a second aspect, the present application provides a method for observing the negative acceleration of a water level control signal, including:

[0027] Input a unit step water level control signal into a fifth-order inertial process to obtain a water level control signal;

[0028] Input the water level control signal into the negative acceleration device of the water level control signal as described in the first aspect to obtain a target acceleration signal.

[0029] In a third aspect, the present application provides a boiler water level control system, including a controller, and the controller includes a cascade proportional controller, an engineering fastest integrator, and the negative acceleration device of the water level control signal as described in the first aspect;

[0030] The cascade proportional controller is respectively connected to the engineering fastest integrator and the negative acceleration device. The water level control signal of the cascade proportional controller is the water level control signal, and the water level control signal is the deviation signal between the boiler water level signal and the boiler water level set signal of the boiler water level control system;

[0031] The controller is:

[0032] C(s) = K cpc [EFI(s) + PNA(s)];

[0033] where C(s) is the transfer function of the controller, EFI(s) is the transfer function of the engineering fastest integrator, PNA(s) is the transfer function of the negative acceleration device, and K cpc is the gain of the cascade proportional controller.

[0034] Preferably, the transfer function of the engineering fastest integrator is:

[0035]

[0036] where EFI(s) is the transfer function of the engineering fastest integrator, s is the Laplace operator, n is the order of the engineering fastest integrator, and T EFI is the time constant of the working fastest integrator.

[0037] Preferably, the transfer function of the negative acceleration device is:

[0038]

[0039] where T I is the integral time constant of the integral accelerator, s is the Laplace operator, T D is the differential time constant of the differentiator, K D is the gain of the differentiator, I(t) is the output signal of the integral accelerator, D(t) is the output signal of the differentiator, and PV IN (t) is the water level control signal.

[0040] Compared with the prior art, the present application has at least the following beneficial effects:

[0041] The negative acceleration device of the present application includes a positive feedback accelerator, a differentiator, and a negative output controller; the positive feedback accelerator is used to accelerate the water level control signal to obtain an acceleration signal; the differentiator is used to convert the acceleration signal to generate a differential signal; the negative output controller is used to extract the negative acceleration signal in the differential signal.

[0042] This application performs negative acceleration on the water level control signal through a negative acceleration device, so that the negative signal with a downward trend in the water level control signal is output in advance, thereby performing negative over-water level control in advance. That is, the positive feedback accelerator can play a role in signal acceleration, with an acceleration effect starting at zero deviation, reducing control lag, and thus being able to solve the problem of negative over-water level in the boiler water level control system and enhancing the control effect. Description of the Drawings

[0043] Figure 1 It is a schematic structural diagram of the negative acceleration device for the water level control signal shown in an embodiment of this application;

[0044] Figure 2 It is a schematic structural diagram of the negative acceleration device for the water level control signal shown in another embodiment of this application;

[0045] Figure 3 It is a schematic structural diagram of the negative acceleration method for the water level control signal shown in an embodiment of this application;

[0046] Figure 4 It is a schematic diagram of the extraction result of the negative acceleration device shown in an embodiment of this application;

[0047] Figure 5 It is a schematic structural diagram of the boiler water level control system shown in an embodiment of this application;

[0048] Figure 6 It is a schematic diagram of the control result of the boiler water level control system shown in an embodiment of this application. Detailed Embodiments

[0049] Next, the technical solutions in the embodiments of this application will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of this application.

[0050] It should be understood that the step numbers used in the text are only for convenient description and do not limit the execution order of the steps.

[0051] It should be understood that the terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. As used in the specification of this application and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include the plural forms.

[0052] The terms "comprising" and "including" indicate the presence of the described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their combinations.

[0053] The term "and / or" refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0054] Any process or method description described in this application can be understood to represent a module, segment or part of code including one or more executable instructions for implementing a specific logical function or process, and the scope of the preferred embodiments of this application includes additional implementations, where the functions may be executed not in the order shown or discussed, including in a substantially simultaneous manner or in the reverse order according to the functions involved, which should be understood by those skilled in the technical field to which the embodiments of this application belong.

[0055] The logic and / or steps described in this application, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, apparatus or device (such as a computer-based system, a system including a processor, or other systems that can fetch and execute instructions from the instruction execution system, apparatus or device), or used in combination with these instruction execution systems, apparatuses or devices. For the purposes of this specification, a "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by or in combination with an instruction execution system, apparatus or device.

[0056] Please refer to Figure 1 , Figure 1 FIG. is a schematic structural diagram of a negative acceleration device for a water level control signal provided by an embodiment of this application. The negative acceleration device for a water level control signal of the embodiment of this application can be mounted on a computer device, and the computer device includes but is not limited to devices such as smart phones, laptop computers, tablet computers, desktop computers, physical servers and cloud servers. As Figure 1 shown, the negative acceleration device for a water level control signal of this embodiment includes a positive feedback accelerator 11, a differentiator 12 and a negative output controller 13;

[0057] The positive feedback accelerator 11 is used to accelerate the water level control signal to obtain an acceleration signal;

[0058] The differentiator 12 is used to convert the acceleration signal to generate a differential signal;

[0059] The negative output controller 13 is used to extract the negative acceleration signal from the differential signal.

[0060] In this embodiment, the water level control signal is accelerated and observed by a positive feedback accelerator, which can stably and quickly suppress the negative deviation of the given system process. Taking a thermal power unit as an example, it takes a certain amount of time for the boiler water level to change from zero deviation to a certain negative deviation. The positive feedback accelerator of the present application has an accelerating effect, so that the boiler water level eliminates the control lag problem with the acceleration of the positive feedback accelerator after starting from zero deviation. Therefore, it has a good effect on suppressing the boiler water level of the boiler water level control system.

[0061] It should be noted that the negative direction in this embodiment represents a negative signal, such as -1.

[0062] Optionally, the water level control signal is a deviation signal between the boiler water level signal of the boiler water level control system and the boiler water level set signal.

[0063] In some embodiments, as Figure 2 shown, the positive feedback accelerator 11 includes a positive feedback link 111, an integral accelerator 112, and an integral limiter 113;

[0064] The positive feedback link is used to control the acceleration of the integral accelerator;

[0065] The integral accelerator is used to accelerate the water level control signal to generate an acceleration signal;

[0066] The integral limiter is used to limit the acceleration signal output by the integral accelerator.

[0067] In this embodiment, an integral limiter is introduced on the basis of the integral accelerator to avoid the problem of non-convergence when the integral accelerator controls the output in the positive feedback link, and ensure the convergence of the signal output.

[0068] Optionally, the integral accelerator is:

[0069]

[0070] where I(s) is the transfer function of the integral accelerator, s is the Laplace operator, and T I is the integral time constant of the integral accelerator.

[0071] The integral limiter is:

[0072]

[0073] where I(t) is the output signal of the integral accelerator, and PV IN (t) is the water level control signal.

[0074] Optionally, the differentiator:

[0075]

[0076] Among them, D(s) is the transfer function of the differentiator, T D is the differentiation time constant of the differentiator, s is the Laplace operator, K D is the gain of the differentiator.

[0077] Optionally, the negative output controller is:

[0078]

[0079] Among them, NOC(t) is the output signal of the negative output controller, and D(t) is the output signal of the differentiator.

[0080] Please refer to Figure 3 , this application provides a flow schematic diagram of a negative acceleration observation method for a water level control signal. As Figure 3 shown, this method includes:

[0081] Step S301, input a unit step water level control signal into a fifth-order inertia process to obtain a water level control signal;

[0082] Step S302, input the water level control signal into the negative acceleration device of the water level control signal as Figure 1 or Figure 2 shown to obtain a target acceleration signal.

[0083] In this embodiment, a negative acceleration observation of the PNA process is performed on the process output signal of the fifth-order inertia process (Five Order Inertia process, FOIP) under a unit step input.

[0084] Optionally, the fifth-order inertia process FOIP is:

[0085]

[0086] Among them, FOIP(s) is the transfer function of the fifth-order inertia process FOIP, T FOIP is the FOIP time constant, with the unit of s.

[0087] As an example rather than a limitation, at T I = 200 s, T D = 200 s, T FOIP = 200 s, K D = 4, with the FOIP input being a unit step water level control signal, the observation result of the process negative accelerator PNA output signal of the FOIP process output signal is obtained, as Figure 4 shown. PV FOIP(t) is the process output signal of the 5th-order inertial process FOIP for a unit step input, PV PNA (t) is the output signal of the negative acceleration device PNA. As can be seen from Figure 4 it, the process output signal of PNA significantly leads the process output signal of FOIP, objectively playing the role of leading observation of the negative water level control signal, being able to advance the negative control quantity, and having a good effect on suppressing the negative over-water level of the boiler water level control system.

[0088] Please refer to Figure 5 this application also provides a structural schematic diagram of a boiler water level control system. As shown in Figure 5 it, the system includes a controller (Controller, C) and a control process (Controller Process, CP). The controller includes a cascade proportional controller CPC, an engineering fastest integrator EFI, and a negative acceleration device PNA for the water level control signal as shown in Figure 1 or Figure 2 it;

[0089] The cascade proportional controller is respectively connected to the engineering fastest integrator and the negative acceleration device. The water level control signal of the cascade proportional controller is the water level control signal, and the water level control signal is the deviation signal between the boiler water level signal and the boiler water level set signal of the boiler water level control system;

[0090] The controller is:

[0091] C(s) = K cpc [EFI(s) + PNA(s)];

[0092] where C(s) is the transfer function of the controller, EFI(s) is the transfer function of the engineering fastest integrator, PNA(s) is the transfer function of the negative acceleration device, and K cpc is the gain of the cascade proportional controller.

[0093] Preferably, the transfer function of the engineering fastest integrator is:

[0094]

[0095] where EFI(s) is the transfer function of the engineering fastest integrator, s is the Laplace operator, n is the order of the engineering fastest integrator, and T EFI is the time constant of the engineering fastest integrator.

[0096] Preferably, the transfer function of the negative acceleration device is:

[0097]

[0098] where TI is the integration time constant of the integration accelerator, s is the Laplace operator, and T D is the differentiation time constant of the differentiator, and K D is the gain of the differentiator, I(t) is the output signal of the integration accelerator, D(t) is the output signal of the differentiator, and PV IN (t) is the water level control signal.

[0099] By way of example and not limitation, applying the controller C to the boiler water level control system of a 1000MW ultra-supercritical thermal power unit in a certain power plant, the control results are obtained as Figure 6 shown. After adding the process negative accelerator PNA at 10:00, before adding PNA, the maximum negative deviation of the boiler water level relative to the boiler water level set value is 9.45mm; after adding PNA, the maximum negative deviation of the boiler water level is 5.47mm. It can be seen that PNA has a good effect on suppressing the negative deviation of the boiler water level.

[0100] In several embodiments provided in the present application, it can be understood that each block in the flowchart or block diagram may represent a module, a program segment, or a part of code, and the module, program segment, or part of code includes one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the blocks may occur in a different order from that marked in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in the reverse order, depending on the functions involved.

[0101] If the described function is implemented in the form of a software functional module and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or a part of this technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions for causing a terminal device to execute all or part of the steps of the methods described in various embodiments of the present application. The aforementioned storage medium includes: USB flash drives, mobile hard disks, read-only memories (ROM, Read-Only Memory), random access memories (RAM, Random Access Memory), magnetic disks, or optical discs, etc., all of which can store program codes.

[0102] The specific embodiments described above further elaborate on the purpose, technical solutions, and beneficial effects of the present application. It should be understood that the above are only specific embodiments of the present application and are not used to limit the protection scope of the present application. In particular, for those skilled in the art, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A negative acceleration device for a water level control signal, characterized in that, It includes a positive feedback accelerator, a differentiator, and a negative output controller; The positive feedback accelerator is used to accelerate the water level control signal to obtain an acceleration signal; The differentiator is used to convert the acceleration signal to generate a differential signal; The negative output controller is used to extract the negative acceleration signal from the differential signal. The negative output controller is: where NOC(t) is the output signal of the negative output controller, and D(t) is the output signal of the differentiator.

2. The negative acceleration device for the water level control signal according to claim 1, characterized in that The water level control signal is the deviation signal between the boiler water level signal and the boiler water level set signal of the boiler water level control system.

3. The negative acceleration device for the water level control signal according to claim 1, characterized in that, The positive feedback accelerator includes a positive feedback link, an integral accelerator, and an integral limiter; The positive feedback link is used to control the acceleration of the integral accelerator; The integral accelerator is used to accelerate the water level control signal to generate an acceleration signal; The integral limiter is used to limit the acceleration signal output by the integral accelerator.

4. The negative acceleration device for the water level control signal according to claim 3, characterized in that, The integral accelerator is: where I(s) is the transfer function of the integrating accelerator, s is the Laplace operator, and T I is the integration time constant of the integrating accelerator; The integral limiter is: where I(t) is the output signal of the integral accelerator, and PV IN (t) is the water level control signal.

5. The negative acceleration device for the water level control signal according to claim 1, characterized in that, The differentiator: where D(s) is the transfer function of the differentiator, T D is the differentiation time constant of the differentiator, s is the Laplace operator, K D is the gain of the differentiator.

6. A negative acceleration observation method for a water level control signal, characterized in that, includes: Input a unit step input signal into a fifth-order inertial process to obtain a water level control signal; Input the water level control signal into the negative acceleration device of the water level control signal as described in any one of claims 1 to 5 to obtain a target acceleration signal.

7. A boiler water level control system, characterized in that, It includes a controller, and the controller includes a cascade proportional controller, an engineering fastest integrator, and the negative acceleration device of the water level control signal as described in any one of claims 1 to 5; The cascade proportional controller is respectively connected to the engineering fastest integrator and the negative acceleration device. The water level control signal of the cascade proportional controller is the water level control signal, and the water level control signal is the deviation signal between the boiler water level signal and the boiler water level set signal of the boiler water level control system; The controller is: C(s) = K cpc [EFI(s) + PNA(s)]; Among them, C(s) is the transfer function of the controller, EFI(s) is the transfer function of the engineering fastest integrator, PNA(s) is the transfer function of the negative acceleration device, and K cpc is the gain of the cascade proportional controller.

8. The boiler water level control system according to claim 7, characterized in that, The transfer function of the engineering fastest integrator is: Among them, EFI(s) is the transfer function of the engineering fastest integrator, s is the Laplace operator, n is the order of the engineering fastest integrator, and T EFI is the time constant of the working fastest integrator.

9. The boiler water level control system according to claim 7, characterized in that, The transfer function of the negative acceleration device is: where T I is the integration time constant of the integrator, s is the Laplace operator, T D is the differentiation time constant of the differentiator, K D is the gain of the differentiator, I(t) is the output signal of the integrator, D(t) is the output signal of the differentiator, PV IN (t) is the water level control signal.

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