A method and system for controlling the power of an electric boiler

Abstract

The application provides an electric boiler power control method and a control system. The electric boiler comprises an electric boiler inner cylinder, an electric boiler outer cylinder and a circulating pump. One end of the circulating pump is connected to the electric boiler outer cylinder, and the other end is connected to the electric boiler inner cylinder, which is used for guiding water in the electric boiler outer cylinder into the electric boiler inner cylinder to adjust the water level of the electric boiler inner cylinder. The method comprises the following steps: when detecting that the steam output demand of the electric boiler changes, obtaining a current pressure value of the electric boiler; calculating a pressure deviation value between the current pressure value and a preset target pressure value, and determining an inner cylinder water level demand according to the pressure deviation value; and adjusting the inner cylinder water level, the outer cylinder water level and the working frequency of the circulating pump according to the inner cylinder water level demand to realize the control of the electric boiler power. The electric boiler power control method and the control system provided by the application take the inner cylinder water level demand as a control signal, adjust the inner and outer cylinder water levels and the working frequency of the circulating pump, and quickly adjust the electric boiler power.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automatic control, in particular to a power control method and control system of an electric boiler. BACKGROUND

[0002] In a nuclear power plant, in order to continue production when the unit is cold started or shut down, steam is often provided by an electric boiler. The electric boiler has high working efficiency, and its clean electric energy can be used as input energy, which plays a certain role in protecting the natural environment. At present, the power control system of the electric boiler is relatively complex, often involving temperature control, pressure control, chemical control and electrical control and other influencing factors.

[0003] In the prior art, the power of the electric boiler is usually controlled by injecting chemicals to change the conductivity of the boiler water. However, due to the large water volume of the electric boiler in the nuclear power plant, the rate of chemical injection is limited, so when the power of the electric boiler changes rapidly, this adjustment method has a large hysteresis. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the hysteresis problem of adjusting the power of the electric boiler by conductivity in the prior art, thereby providing a power control method and control system of an electric boiler.

[0005] According to a first aspect, the present application provides a power control method of an electric boiler, the electric boiler comprising an electric boiler inner cylinder, an electric boiler outer cylinder and a circulating pump, one end of the circulating pump being connected to the electric boiler outer cylinder, the other end being connected to the electric boiler inner cylinder, for guiding water in the electric boiler outer cylinder into the electric boiler inner cylinder to adjust the water level of the electric boiler inner cylinder, the method comprising:

[0006] When it is detected that the steam output demand of the electric boiler changes, a current pressure value of the electric boiler is obtained;

[0007] A pressure deviation value between the current pressure value and a preset target pressure value is calculated, and an inner cylinder water level demand is determined according to the pressure deviation value;

[0008] The inner cylinder water level, the outer cylinder water level and the working frequency of the circulating pump are adjusted according to the inner cylinder water level demand, so as to control the power of the electric boiler.

[0009] In an embodiment, the inner cylinder water level demand is generated according to the pressure deviation value, comprising:

[0010] If the pressure deviation is within a preset pressure difference interval, the current inner cylinder water level demand is maintained unchanged.

[0011] In an embodiment, the generating the inner drum water level demand according to the pressure deviation value further comprises:

[0012] If the pressure deviation exceeds the maximum value of the preset pressure deviation interval, increasing the current inner drum water level demand.

[0013] In an embodiment, the generating the inner drum water level demand according to the pressure deviation value further comprises:

[0014] If the pressure deviation is lower than the minimum value of the preset pressure deviation interval, decreasing the current inner drum water level demand.

[0015] In an embodiment, the electric boiler further comprises a chemical dosing system for adjusting the conductivity of the boiler water in the inner drum of the electric boiler, and after the inner drum water level, the outer drum water level and the working frequency of the circulating pump are adjusted according to the inner drum water level demand, the method further comprises:

[0016] detecting a current water level value of the electric boiler and determining whether the current water level value is within a preset water level interval;

[0017] If the current water level value is within the preset water level interval, adjusting the conductivity of the boiler water in the inner drum of the electric boiler by the chemical dosing system.

[0018] In an embodiment, the method further comprises:

[0019] If the current water level value is not within the preset water level interval, returning to the step of acquiring the current pressure value of the electric boiler.

[0020] According to a second aspect, the present application provides an electric boiler power control system, comprising an electric boiler and a controller connected to the electric boiler, the electric boiler comprising an electric boiler inner drum, an electric boiler outer drum and a circulating pump, wherein,

[0021] One end of the circulating pump is connected to the electric boiler outer drum, and the other end is connected to the electric boiler inner drum, for guiding the water in the electric boiler outer drum into the electric boiler inner drum to adjust the water level of the electric boiler inner drum;

[0022] The controller is used to execute the electric boiler power control method of the first aspect and any one of the optional embodiments thereof.

[0023] In an embodiment, the system further comprises a chemical dosing system, one end of the chemical dosing system being connected to the electric boiler inner drum, and the chemical dosing system being used to adjust the conductivity of the boiler water in the electric boiler inner drum.

[0024] In an embodiment, the system further comprises a feedwater regulating valve, one end of the feedwater regulating valve being connected to the feedwater pump, and the feedwater regulating valve being used to adjust the water level of the electric boiler outer drum.

[0025] In an embodiment, the system further comprises a recirculation orifice plate and a circulation regulating valve, one end of the recirculation orifice plate is connected to the outer cylinder of the electric boiler, the other end is connected to the circulation pump and the circulation regulating valve respectively, the other end of the circulation regulating valve is connected to the inner cylinder of the electric boiler, and the recirculation orifice plate and the circulation regulating valve are used to regulate the water level of the inner cylinder of the electric boiler.

[0026] The technical scheme has the following advantages:

[0027] The embodiment of the present application provides an electric boiler power control method, which detects the pressure value of the electric boiler, calculates the pressure deviation value between the current pressure value and the preset target pressure value, monitors the pressure value of the electric boiler in real time, converts the pressure deviation value into inner cylinder water level demand as a control signal, adjusts the inner cylinder water level, the outer cylinder water level and the working frequency of the circulation pump, and realizes the rapid adjustment of the electric boiler power. The water level demand is used as the control signal, the stability and tracking performance of the system are enhanced, and the power and pressure are prevented from generating more overshoot and fluctuation caused by the multi-parameter control mode.

[0028] The embodiment of the present application provides an electric boiler power control system, which adjusts the water level of the inner cylinder of the electric boiler through the circulation pump, controls through the controller, realizes the rapid adjustment of the electric boiler power, uses the water level demand as the control signal, enhances the stability and tracking performance of the system, and avoids the power and pressure from generating more overshoot and fluctuation caused by the multi-parameter control mode. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the specific embodiments of the present application or the technical scheme in the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0030] Figure 1 is a structural block diagram of an electric boiler power control system proposed by the embodiment of the present application;

[0031] Figure 2 is a structural schematic diagram of an electric boiler proposed by the embodiment of the present application;

[0032] Figure 3 is a flow chart of an electric boiler power control method proposed by the embodiment of the present application;

[0033] Figure 4This is a schematic diagram illustrating the relationship between pressure deviation and water level as proposed in an embodiment of the present invention.

[0034] Explanation of reference numerals in the attached figures:

[0035] 1. Electric boiler; 11. Electric boiler inner cylinder; 12. Electric boiler outer cylinder; 13. Circulation pump; 14. Chemical dosing system; 15. Feed water regulating valve; 16. Feed water pump; 17. Recirculation orifice plate; 18. Circulation regulating valve; 19. Drain valve; 2. Controller; 3. Water level sensor; 4. Three-phase electrode; 5. Steam pressure sensor; 6. Steam regulating valve. Detailed Implementation

[0036] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The power control system of electric boilers in nuclear power plants is quite complex, influenced by various factors such as temperature control, pressure control, chemical control, and electrical control. During the power control process, rapid power adjustments are frequently encountered, and the multi-parameter control mode makes it easy for power and pressure to experience significant overshoot and large fluctuations.

[0038] In existing technologies, a single chemical control method is often used, which controls power by changing the conductivity of the boiler water. However, due to the large water volume of electric boilers and the limitation on the chemical injection rate, this method has a significant lag and is only suitable for processes with slow load changes in electric boilers. When dealing with rapid changes in boiler power, the power adjustment is relatively slow. If a liquid level signal is used as the control input, the change in liquid level also lags behind the change in steam flow.

[0039] To achieve rapid adjustment of electric boiler power, this invention provides an electric boiler power control system, such as... Figure 1 As shown, it includes an electric boiler 1 and a controller 2, which are connected. Specifically, as... Figure 2 As shown, the electric boiler 1 includes an inner cylinder 11, an outer cylinder 12, and a circulating pump 13.

[0040] One end of the circulating pump 13 is connected to the outer cylinder 12 of the electric boiler, and the other end is connected to the inner cylinder 11 of the electric boiler. It is used to introduce water from the outer cylinder 12 of the electric boiler into the inner cylinder 11 of the electric boiler to regulate the water level in the inner cylinder 11 of the electric boiler.

[0041] In this embodiment of the invention, during the stable operation of the electric boiler, the circulating pump maintains operation at a certain frequency to control the water level in the inner cylinder of the electric boiler to remain stable. When the pressure deviation of the electric boiler exceeds the maximum value of the preset pressure difference range, the frequency of the circulating pump increases as the pressure deviation increases. When the pressure deviation of the electric boiler is lower than the minimum value of the preset pressure difference range, the frequency of the circulating pump decreases as the pressure deviation decreases.

[0042] Through the above embodiments, the water level in the inner cylinder of the electric boiler is adjusted by a circulating pump and controlled by a controller to achieve rapid adjustment of the electric boiler power. Using water level demand as the control signal enhances the stability and tracking performance of the system, while avoiding excessive overshoot and fluctuations in power and pressure caused by multi-parameter control modes.

[0043] Specifically, in one embodiment, the control system further includes a chemical dosing system 14, one end of which is connected to the inner cylinder 11 of the electric boiler. The chemical dosing system 14 is used to adjust the conductivity of the boiler water in the inner cylinder 11 of the electric boiler.

[0044] In this embodiment of the invention, the chemical dosing system can adjust the pH value and conductivity of the boiler water in the inner cylinder of the electric boiler. The chemical dosing system is used as a compensation for the rapid adjustment of the pressure mode, so as to further realize the control of the power of the electric boiler.

[0045] The conductivity of boiler water reflects the degree of evaporation and concentration in the boiler water circulation system. Therefore, when the power of the electric boiler changes slowly, adjusting the conductivity can effectively control the power of the electric boiler. Adjusting the conductivity of boiler water through a chemical dosing system is existing technology and will not be elaborated upon here.

[0046] Specifically, in one embodiment, the control system further includes a water supply regulating valve 15, one end of which is connected to a water supply pump 16. The water supply regulating valve 15 is used to regulate the water level of the outer casing 12 of the electric boiler.

[0047] In this embodiment of the invention, the feedwater pump tracks the frequency of the circulating pump and adjusts the water level in the outer casing of the electric boiler through a feedwater regulating valve. When the water level is within a preset range, the feedwater regulating valve maintains the water level in the outer casing of the electric boiler at a certain level.

[0048] Specifically, in one embodiment, the control system further includes a recirculation orifice plate 17 and a circulation regulating valve 18. One end of the recirculation orifice plate 17 is connected to the outer cylinder 12 of the electric boiler, and the other end is connected to the circulation pump 13 and the circulation regulating valve 18 respectively. The other end of the circulation regulating valve 18 is connected to the inner cylinder 11 of the electric boiler. The recirculation orifice plate 17 and the circulation regulating valve 18 are used to regulate the water level in the inner cylinder of the electric boiler.

[0049] In this embodiment of the invention, when the pressure deviation is within a preset differential pressure range, the water level in the inner cylinder of the electric boiler is maintained at a certain water level value through the recirculation orifice plate and the circulation regulating valve.

[0050] Specifically, in one embodiment, the control system further includes a drain valve 19 connected to the inner cylinder 11 of the electric boiler. When the pressure deviation is lower than the minimum value of the preset pressure difference range, the drain valve 19 is opened to quickly reduce the water level in the inner cylinder 11 of the electric boiler.

[0051] Specifically, in one embodiment, the control system further includes a water level sensor 3, which is disposed in the inner cylinder 11 of the electric boiler and measures the water level in the inner cylinder 11 of the electric boiler.

[0052] In this embodiment of the invention, when the water level sensor measures the water level in the inner cylinder of the electric boiler to reach a height of L3, or when the frequency of the circulating pump reaches the rated full frequency, or when the pressure deviation is within the preset differential pressure range, the controller controls the frequency of the circulating pump to maintain stable operation, so that the water level in the inner cylinder of the electric boiler remains stable.

[0053] When the water level sensor measures the water level in the inner cylinder of the electric boiler to reach height L1, or when the frequency of the circulating pump reaches its minimum, or when the pressure deviation value is within the preset differential pressure range, the frequency of the circulating pump is controlled to maintain stable operation, so that the water level in the inner cylinder of the electric boiler remains stable.

[0054] L1 is the minimum water level limit of the inner cylinder of the electric boiler. When the water level in the inner cylinder of the electric boiler reaches the height of L1, the electric boiler operates at the minimum load.

[0055] Specifically, in one embodiment, the control system further includes a three-phase electrode 4, a steam pressure sensor 5, and a steam regulating valve 6. During the period when the electric boiler is operating at a stable power, the three-phase electrode 4 is put into operation, the steam pressure sensor 5 detects the steam pressure at the outlet of the electric boiler, and the steam regulating valve 6 maintains a certain opening to continuously supply steam to downstream users.

[0056] This invention also provides a power control method for an electric boiler, such as... Figure 3 As shown, the method includes the following steps S101 to S103.

[0057] Step S101: When a change in the steam output demand of the electric boiler is detected, the current pressure value of the electric boiler is obtained.

[0058] In this embodiment of the invention, the current pressure value of the electric boiler is the steam pressure at the boiler outlet. When the steam output of the electric boiler changes, the steam output demand changes accordingly, requiring adjustments to the water level and power of the electric boiler. The steam output demand of the electric boiler can be detected by monitoring the valve opening; when the valve opening changes, the steam output of the electric boiler will change.

[0059] Step S102: Calculate the pressure deviation between the current pressure value and the preset target pressure value, and determine the inner cylinder water level requirement based on the pressure deviation value.

[0060] In this embodiment of the invention, the preset target pressure value Ps is the pressure value of the electric boiler during steady-state operation. The pressure deviation value ΔP between the current pressure value Pt and the preset target pressure value Ps is calculated, where ΔP = Ps - Pt. The larger the steam volume of the downstream users of the electric boiler and the faster the rate of change, the more obvious the change in the current pressure value Pt of the electric boiler, the larger the pressure deviation value, and the greater the demand for the inner cylinder water level.

[0061] Step S103: Adjust the water level of the inner cylinder, the water level of the outer cylinder, and the operating frequency of the circulating pump according to the water level requirements of the inner cylinder to control the power of the electric boiler.

[0062] In this embodiment of the invention, when the pressure deviation value is not within the preset pressure difference range, the water level of the inner cylinder and the water level of the outer cylinder are adjusted to compensate for the increased steam flow rate, and the operating frequency of the circulating pump is adjusted to adjust the speed of the circulating pump accordingly, thereby realizing the control of the power of the electric boiler.

[0063] Through the above embodiments, the pressure value of the electric boiler is detected, and the pressure deviation between the current pressure value and the preset target pressure value is calculated to monitor the pressure value of the electric boiler in real time. The pressure deviation value is converted into the inner cylinder water level demand, which is used as a control signal to adjust the inner cylinder water level, outer cylinder water level, and the operating frequency of the circulating pump, so as to realize the rapid adjustment of the electric boiler power. Using the water level demand as the control signal enhances the stability and tracking performance of the system, while avoiding the large overshoot and fluctuations in power and pressure caused by multi-parameter control mode.

[0064] Specifically, in one embodiment, the step S102 above, which determines the inner cylinder water level requirement based on the pressure deviation value, includes the following steps:

[0065] Step S1021: If the pressure deviation is within the preset pressure difference range, then maintain the current inner cylinder water level requirement unchanged.

[0066] In this embodiment of the invention, the preset pressure difference range is ΔP1~ΔP2. If ΔP1<ΔP<ΔP2, that is, the pressure deviation is within the preset pressure difference range and the water level in the inner cylinder is within the preset water level range, then the current water level in the inner cylinder is maintained at the current water level and the frequency of the circulating pump is maintained at the current frequency.

[0067] During the period when the electric boiler is operating at a stable power level, the three-phase motor is put into operation, and the steam regulating valve is kept at a certain opening position to continuously supply steam to downstream users.

[0068] Specifically, in one embodiment, the step S102 above, which determines the inner cylinder water level requirement based on the pressure deviation value, further includes the following steps:

[0069] Step S1022: If the pressure deviation exceeds the maximum value of the preset pressure difference range, increase the current water level requirement of the inner cylinder.

[0070] In this embodiment of the invention, when the downstream user of the electric boiler increases the amount of steam, the valve opening of the steam regulating valve increases, the current pressure value of the electric boiler decreases, and the pressure deviation exceeds ΔP2. It is necessary to quickly raise the water level in the inner cylinder of the electric boiler and increase the power of the electric boiler to compensate for the increased steam flow.

[0071] For example, the correspondence between pressure deviation values ​​and inner cylinder water level requirements is as follows: Figure 4 As shown, L1 is the minimum water level limit for the inner cylinder of the electric boiler. When the water level is at L1, the electric boiler operates at the minimum load. L3 is the maximum water level limit for the electric boiler, serving as a buffer zone for water level fluctuations.

[0072] Specifically, in one embodiment, the step S102 above, which determines the inner cylinder water level requirement based on the pressure deviation value, further includes the following steps:

[0073] Step S1023: If the pressure deviation is lower than the minimum value of the preset pressure difference range, then reduce the current water level requirement of the inner cylinder.

[0074] In this embodiment of the invention, when the steam demand of downstream users of the electric boiler decreases, the opening of the steam regulating valve decreases, the outlet steam pressure of the electric boiler increases, the current pressure value rises, and the pressure deviation becomes negative. It is necessary to quickly lower the water level in the inner cylinder of the electric boiler to compensate for the reduced steam flow and prevent the electric boiler from overpressured. The smaller the steam demand of downstream users, the faster the pressure decreases, the more significant the rise in the current pressure value, and the larger the negative pressure deviation.

[0075] When the pressure deviation is lower than the minimum value of the preset pressure difference range, the frequency of the circulation pump needs to be reduced to the lowest frequency, and the circulation regulating valve needs to be closed to quickly reduce the water supply to the inner cylinder of the electric boiler. At the same time, the inner cylinder drain valve should be opened quickly to lower the water level in the inner cylinder of the electric boiler.

[0076] Specifically, in one embodiment, the electric boiler power control method provided by the present invention further includes the following steps:

[0077] Step S104: Detect the current water level of the electric boiler and determine whether the current water level is within the preset water level range.

[0078] Step S105: If the current water level is within the preset water level range, the chemical dosing system is controlled to adjust the conductivity of the boiler water in the inner cylinder of the electric boiler.

[0079] In this embodiment of the invention, if the water level of the electric boiler is within a preset water level range, the electric boiler is in a steady-state operating condition, and the pressure deviation is within a preset pressure difference range. The chemical dosing system is controlled to maintain the pH value and conductivity of the boiler water in the inner drum of the electric boiler, so as to achieve slow adjustment of the power of the electric boiler.

[0080] Specifically, in one embodiment, the electric boiler power control method provided by the present invention further includes the following steps:

[0081] Step S106: If the current water level is not within the preset water level range, return to step S101.

[0082] In this embodiment of the invention, the water level of the inner cylinder of the electric boiler is detected in real time. When the current water level is not within the preset water level range, the current pressure of the electric boiler is detected to achieve real-time control of the power of the electric boiler.

[0083] It should be noted that the controller in the electric boiler power control system is used to execute the above-mentioned electric boiler power control method. During the operation of the electric boiler, the controller adjusts the water level in the inner cylinder, the water level in the outer cylinder, and the operating frequency of the circulating pump accordingly.

[0084] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A power control method for an electric boiler, the electric boiler comprising: The electric boiler comprises an inner cylinder, an outer cylinder, and a circulating pump, wherein one end of the circulating pump is connected to the outer cylinder and the other end is connected to the inner cylinder, and is used to introduce water from the outer cylinder into the inner cylinder to regulate the water level in the inner cylinder. The method includes: When a change in the steam output demand of the electric boiler is detected, the current pressure value of the electric boiler is obtained; Calculate the pressure deviation between the current pressure value and the preset target pressure value, and determine the inner cylinder water level requirement based on the pressure deviation value; The water levels of the inner and outer cylinders, as well as the operating frequency of the circulating pump, are adjusted according to the water level requirements of the inner cylinder to control the power of the electric boiler. The electric boiler also includes a chemical dosing system, which is used to adjust the conductivity of the boiler water in the inner cylinder. After adjusting the inner cylinder water level, outer cylinder water level, and operating frequency of the circulating pump according to the inner cylinder water level requirements, the method further includes: The current water level of the electric boiler is detected, and it is determined whether the current water level is within a preset water level range. If the current water level is within a preset water level range, the chemical dosing system is controlled to adjust the conductivity of the boiler water in the inner cylinder of the electric boiler. If the current water level is not within the preset water level range, return to the step of obtaining the current pressure value of the electric boiler; Based on the pressure deviation value, the required water level in the inner cylinder is determined, including: If the pressure deviation value is within the preset pressure difference range, the current inner cylinder water level requirement will remain unchanged. If the pressure deviation value exceeds the maximum value of the preset pressure difference range, the current inner cylinder water level requirement will be increased; If the pressure deviation value is lower than the minimum value of the preset pressure difference range, the current water level requirement of the inner cylinder will be reduced.

2. A power control system for an electric boiler, characterized in that, The system includes an electric boiler and a controller connected to the electric boiler. The electric boiler includes: an inner boiler cylinder, an outer boiler cylinder, and a circulating pump. One end of the circulating pump is connected to the outer cylinder of the electric boiler, and the other end is connected to the inner cylinder of the electric boiler. It is used to introduce water from the outer cylinder of the electric boiler into the inner cylinder of the electric boiler to regulate the water level in the inner cylinder of the electric boiler. The controller is used to execute the electric boiler power control method according to claim 1.

3. The system according to claim 2, characterized in that, It also includes a chemical dosing system, one end of which is connected to the inner cylinder of the electric boiler. The chemical dosing system is used to adjust the conductivity of the boiler water in the inner cylinder of the electric boiler.

4. The system according to claim 2, characterized in that, It also includes a water supply regulating valve, one end of which is connected to a water supply pump, and the water supply regulating valve is used to regulate the water level in the outer cylinder of the electric boiler.

5. The system according to claim 2, characterized in that, It also includes a recirculation orifice plate and a circulation regulating valve. One end of the recirculation orifice plate is connected to the outer cylinder of the electric boiler, and the other end is connected to the circulation pump and the circulation regulating valve respectively. The other end of the circulation regulating valve is connected to the inner cylinder of the electric boiler. The recirculation orifice plate and the circulation regulating valve are used to regulate the water level in the inner cylinder of the electric boiler.

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