A deep peak-shaving adaptive minimum flow control method and system based on feed water pump configuration

Abstract

The application discloses a kind of based on the configuration of feed water pump depth peak-shaving adaptive minimum flow control method and system, belong to thermal power plant automatic control and energy-saving technical field.The application is according to whether pre-pump and main feed water pump are coaxial drive, select corresponding minimum flow control mode: critical cavitation safety flow is dynamically calculated based on real-time operating parameter in coaxial drive system, as the basis for recirculation valve opening;Pre-pump independent drive system uses main feed water pump real-time temperature rise as control basis, and temperature rise is lower than safety threshold when it is allowed to run below fixed flow threshold value.Simultaneously, vibration and metal temperature parameters are monitored in real time, and when the limit is exceeded, the recirculation valve is opened by over-ride.The application solves the contradiction between safety and economy by configuration adaptive identification and differentiated control strategy, which ensures the safety of feed water pump while significantly improving the economy of unit deep peak-shaving operation.

Description

Technical Field

[0001] This invention belongs to the field of automatic control and energy-saving technology for thermal power plants, specifically relating to a deep peak-shaving adaptive minimum flow control method and system based on feedwater pump configuration. Background Technology

[0002] Against the backdrop of energy structure transformation, coal-fired power generating units need to undertake deep peak-shaving tasks, often operating at loads far below their design limits. During this process, boiler feedwater flow is significantly reduced, and feedwater pumps, especially high-pressure main feedwater pumps, are highly susceptible to operating below their minimum design flow rate. This can lead to two serious consequences: first, vaporization of the liquid inside the pump causes cavitation, damaging the impeller; second, excessive temperature rise of the liquid inside the pump due to friction during operation leads to pump body deformation and seal failure. To address this, feedwater pumps are equipped with a minimum flow recirculation system. When the flow rate is detected to be too low, the recirculation valve automatically opens, diverting a portion of the high-pressure outlet water back to the deaerator, thereby ensuring that the flow rate through the pump does not fall below the safe value.

[0003] Currently, the activation of this recirculation valve is generally based on a fixed lower flow limit setting (e.g., 25%-30% of the main pump's rated flow). However, this "one-size-fits-all" control strategy has significant drawbacks and cannot adapt to different types of feedwater pump system configurations, especially under extreme operating conditions such as deep peak shaving.

[0004] In systems where the booster pump and main feedwater pump are coaxially driven (typically by a steam turbine or variable frequency motor), the main pump speed decreases under low load, causing a simultaneous and significant drop in the booster pump outlet pressure (i.e., the main pump inlet pressure). At this point, the main pump's effective net positive suction head (NPSHa) decreases drastically, making cavitation risk the primary concern. Traditional fixed threshold control may be slow to react and unable to provide timely protection before the main pump inlet conditions deteriorate.

[0005] For systems where the booster pump is driven by an independent industrial frequency motor, the booster pump operates at a constant speed under low load, maintaining a relatively high inlet pressure for the main pump and minimizing the risk of cavitation. At this point, the primary constraint limiting the main pump's low-flow operation is the temperature rise of the working fluid within the pump. If a higher fixed flow threshold is still used for recirculation, a large amount of high-temperature, high-pressure feedwater that has already performed its work will flow back, resulting in significant energy loss and severely weakening the economic efficiency of deep peak shaving for the unit.

[0006] Therefore, existing technologies lack a solution that can intelligently identify system characteristics and dynamically optimize minimum flow control strategies, resulting in either insufficient security or poor cost-effectiveness in deep peak shaving scenarios. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a deep peak shaving adaptive minimum flow control method and system based on the configuration of the feedwater pump, so as to solve the problem that the existing fixed threshold control cannot take into account the contradiction between safety and economy in different types of feedwater pump systems during deep peak shaving.

[0008] To achieve the above objectives, the present invention employs the following technical solution: This invention discloses a deep peak-shaving adaptive minimum flow control method based on feedwater pump configuration, comprising: S1, acquire the measurement parameters of the main feed water pump and the real-time data of the power coupling relationship of the booster pump; S2, based on the power coupling relationship of the booster pump in the water supply system, determine whether the booster pump and the main water supply pump are coaxially driven, and select the corresponding minimum flow control mode based on the determination result; S3. If it is a coaxial drive system, the critical cavitation safety flow rate under the current operating condition is dynamically calculated based on the real-time operating parameters of the main feed water pump, and the critical cavitation safety flow rate is used as the basis for controlling the opening of the recirculation valve. If it is a pre-pump independent drive system, the real-time temperature rise of the main feed water pump is used as the basis for controlling the opening of the recirculation valve. When the real-time temperature rise is lower than the safety threshold, the main feed water pump is allowed to operate under conditions lower than the preset fixed flow threshold without opening or partially opening the recirculation valve. S4. Monitor the vibration parameters and metal temperature parameters of the main water pump in real time. When any parameter exceeds the corresponding safety limit, the override control opens the recirculation valve.

[0009] A further improvement of the present invention is that: Preferably, in S1, the main feed water pump measurement parameters include the main feed water pump speed, flow rate, inlet pressure, outlet pressure, and temperature.

[0010] Preferably, in S2, the method for determining whether the booster pump and the main feed water pump are coaxially driven includes at least one of the following: Read the design configuration signal stored in the distributed control system (DCS), and determine the power coupling relationship of the booster pump based on the design configuration signal; The real-time speed data of the booster pump and the main feed water pump are obtained. If the speed of the booster pump and the speed of the main feed water pump change synchronously during the unit load change, it is determined to be coaxial drive; if the speed of the main feed water pump changes with the load while the speed of the booster pump remains constant, it is determined to be independent drive of the booster pump.

[0011] Preferably, in S3, the formula for calculating the critical cavitation safety flow rate is: Qcritical = f ( n , P in ) in, n Real-time speed of the main feed water pump P in The function refers to the real-time inlet pressure of the main feedwater pump. f It was determined by the cavitation similarity law of the pump and the fitting of characteristic curves.

[0012] Preferably, the process of using the critical cavitation safety flow rate as the basis for controlling the opening of the recirculation valve is as follows: a feedback control loop is formed with the critical cavitation safety flow rate as the set value and the actual flow rate of the main pump as the process value; at the same time, the rate of change of the main feed water pump speed and / or the rate of change of the inlet pressure are introduced as feedforward signals.

[0013] Preferably, the real-time temperature rise of the main feedwater pump is obtained through any of the following methods: The real-time temperature rise is calculated based on a real-time thermal balance model, which calculates the real-time temperature rise according to the estimated pump shaft power, the hydraulic power obtained by the fluid, the specific heat capacity of water, and the mass flow rate of the feed water. The temperature is obtained directly by measuring the temperature of the pump casing, sealing cavity, or inlet / outlet medium of the main feed water pump.

[0014] Preferably, the real-time temperature rise of the main feedwater pump is used as the basis for controlling the opening of the recirculation valve. During the control process, when Δ T <Δ T warn When Δ T warn ≤ Δ T <Δ T trip At that time, adjust the opening of the recirculation valve to make Δ T Falling back to Δ T warn The following; when Δ T >Δ T trip At that time, the overdrive fully opens the recirculation valve and triggers the pump unit protection interlock; among which, Δ T For real-time temperature rise, Δ T warn The temperature rise warning value is Δ. T trip This is the temperature rise trip value.

[0015] Preferably, the temperature rise warning value Δ T warn The temperature rise is 60% to 80% of the maximum allowable temperature rise by the pump manufacturer; the temperature rise trip value Δ T tripThe value shall not be less than the manufacturer's maximum allowable temperature rise.

[0016] 9. A deep peak-shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 1, characterized in that the override control includes: Acquire vibration and temperature over-limit signals from independent safety monitoring instruments; When any of the aforementioned over-limit signals is received, the recirculation valve is forcibly opened to the fully open position with the highest priority.

[0017] A deep peak-shaving adaptive minimum flow control system based on feedwater pump configuration includes: The data acquisition module is used to acquire the measurement parameters of the main feed water pump and the real-time data of the power coupling relationship of the booster pump; The configuration identification module is used to determine whether the pre-pump and the main water supply pump are coaxially driven based on the power coupling relationship of the pre-pump in the water supply system, and select the corresponding minimum flow control mode based on the determination result. The strategy control module is used to execute the minimum flow control mode. If it is a coaxial drive system, it dynamically calculates the critical cavitation safety flow under the current operating conditions based on the real-time operating parameters of the main feed water pump, and uses the critical cavitation safety flow as the basis for controlling the opening of the recirculation valve. If it is a pre-pump independent drive system, the real-time temperature rise of the main feed water pump is used as the basis for controlling the opening of the recirculation valve. When the real-time temperature rise is lower than the safety threshold, the main feed water pump is allowed to operate under conditions lower than the preset fixed flow threshold without opening or partially opening the recirculation valve. The execution and protection module is used to monitor the vibration parameters and metal temperature parameters of the main feed water pump in real time. When any parameter exceeds the corresponding safety limit, the override control opens the recirculation valve.

[0018] Compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method and system for deep peak shaving adaptive minimum flow control based on feedwater pump configuration. The method includes: firstly, identifying whether the booster pump and the main feedwater pump are coaxially driven; if coaxially driven, cavitation prevention priority mode is activated, dynamically calculating and increasing the recirculation valve opening threshold based on the main pump speed and inlet pressure to prevent cavitation in advance; if independently driven, thermal control optimization mode is activated, using the real-time temperature rise of the main pump as the main criterion, allowing recirculation to be pushed back or reduced within the safe temperature rise range to reduce energy loss; simultaneously, a safety boundary protection is set, with priority given to control actions, prioritizing unit safety. The system includes corresponding data acquisition, configuration identification, strategy control, and execution modules. This invention achieves adaptive matching of the control strategy to equipment characteristics, and can adaptively switch between cavitation prevention priority and thermal control optimization modes based on the differences in the transmission configuration of the booster pump and the main feedwater pump, significantly improving the economic efficiency of deep peak shaving operation of the unit while ensuring the inherent safety of the feedwater pump. This invention, while ensuring the absolute safety of the feedwater pump, minimizes useless recirculation flow under deep peak-shaving conditions, thereby improving unit operating efficiency and peak-shaving benefits. The method of this invention is continuously executed in a loop during unit operation. The method of this invention also has the following advantages: (1) For the fragile coaxial system, by dynamically predicting the risk of cavitation and providing advanced protection, the major risk of damage to the main feedwater pump due to cavitation during deep peak shaving is fundamentally avoided.

[0019] (2) For efficient independent drive systems, by replacing blind recirculation with on-demand cooling, the recirculation flow during deep peak shaving (especially in the 30%-50% load range) can be significantly reduced, reducing plant power consumption and heat loss. According to preliminary estimates, the net efficiency of the unit under this operating condition can be increased by 0.1%-0.4%, and the peak shaving benefits can be significantly increased.

[0020] (3) This method can automatically identify and adapt to the feedwater pump configuration of different power plants and different units without manual setting or switching, which improves the universality and ease of use of advanced control strategies. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the overall process of the method of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings: Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0023] It should be noted that the cavitation risk of this invention specifically refers to the backflow cavitation and rotational stall phenomenon caused by impeller inlet backflow under low flow conditions. The risk increases significantly with decreasing speed and deteriorating inlet pressure, which is manifested in the pump's minimum continuous stable flow rate (MCSF) increasing with changes in operating conditions.

[0024] The first aspect of this invention discloses a deep peak-shaving adaptive minimum flow control method based on feedwater pump configuration. After system power-on initialization, the method first performs configuration identification by reading preset configuration parameters or analyzing real-time operating data (to determine whether the speed of the upstream pump is strictly synchronized with the speed of the main pump). The identification result is used as a global variable to guide the program into the corresponding control branch. Specifically, the method includes the following steps: S1 acquires real-time data including the main feed water pump speed, flow rate, inlet and outlet pressure, temperature, and the power coupling relationship signal of the booster pump.

[0025] The temperature measurement point is a metal measuring point on the pump casing or sealed cavity, which can measure the inlet or outlet temperature as needed. The power coupling relationship signal of the booster pump includes the design configuration signal, booster pump speed, main feed pump speed, and load stored in the distributed control system (DCS) or plant-level monitoring information system.

[0026] S2, System Configuration Identification Step, where the power coupling relationship of the booster pump includes coaxial drive between the booster pump and the main feedwater pump, and drive by an independent industrial frequency motor. Based on the power coupling relationship between the booster pump and the main feedwater pump in the feedwater system, it is determined whether they are coaxially driven. During this process, the power coupling relationship of the booster pump remains fixed during unit operation; this step is an online confirmation and error-proofing check of the fixed configuration. In this process, by reading the design configuration signals in the unit's DCS, or analyzing real-time data on the speed correlation between the booster pump and the main pump, it is automatically determined whether the current system is coaxially driven by the booster pump and the main pump, or independently driven by the booster pump.

[0027] For example, it is possible to identify whether the booster pump and the main feedwater pump are coaxially driven by configuration signals. This is done by reading the design configuration signals stored in the distributed control system (DCS) or the plant-level monitoring information system. Specifically, a configuration identifier bit is pre-set in the configuration database of the control system. For example, a first value indicates that the booster pump and the main feedwater pump are coaxially driven (including coaxial arrangements driven by a steam turbine and coaxial arrangements driven by a variable frequency motor), and a second value indicates that the booster pump is driven by an independent fixed frequency motor. Configuration identification can be completed by reading this identifier bit during system initialization. This method is simple to implement, yields reliable results, and is suitable for situations where the unit design data is complete.

[0028] For example, it is possible to identify whether the booster pump and the main feedwater pump are coaxially driven by operational data. In the absence of a preset configuration signal or when the configuration signal is invalid, the configuration is automatically identified by analyzing the real-time operational data of the booster pump and the main feedwater pump. The criteria are as follows: during unit load changes, if the booster pump speed and the main feedwater pump speed always change synchronously, i.e., the speed ratio between the two is basically constant, for example, if the deviation of the speed ratio from its initial value is consistently less than a preset threshold (this preset threshold can be set to ±2% to ±5%, and the continuous judgment time can be set to 30s to 120s), then it is determined to be a coaxial drive system; if the main feedwater pump speed changes with the load while the booster pump speed remains constant at the operating frequency, then it is determined to be a booster pump independent drive system. Optionally, the current signal and frequency signal of the booster pump drive motor, or the steam inlet parameter signal of the drive turbine, can be used for auxiliary verification to further improve the reliability of the identification results.

[0029] S3, Control Strategy Switching Step: Based on the results of the system configuration identification step, select the corresponding minimum flow control mode; if identified as a coaxial drive system, execute S31; if identified as a pre-pump independent drive system, execute S32.

[0030] S31, activating the anti-cavitation priority mode. For this type of system, the main pump speed decreases under low load, causing a simultaneous and significant drop in the outlet pressure of the booster pump (i.e., the inlet pressure of the main pump). This drastically reduces the effective net positive suction head (NPSH) of the main pump, making cavitation risk the primary concern. The critical cavitation safety flow rate is dynamically calculated based on the real-time operating parameters of the main feedwater pump, and this dynamic flow rate value is used as the main basis for controlling the opening of the recirculation valve.

[0031] According to the cavitation similarity law of pumps, under the condition that the cavitation specific speed remains constant, the required net positive suction head (NPSH) of the pump changes with the speed according to a specific similarity relationship; at the same time, the effective NPSH of the main feedwater pump depends on its inlet pressure. Therefore, the critical safe cavitation flow rate to ensure that the main pump does not cavitate is... Q critical This can represent the real-time speed of the main pump. n With real-time inlet pressure P in The function. In the cavitation prevention priority mode, the dynamic calculation of the critical cavitation safety flow rate ( Q critical The functional relationship of ) is: Q critical = f ( n , P in ),in n Real-time speed of the main feed water pump P in The function is the real-time inlet pressure of the main feedwater pump. fThe relationship is determined through the pump's cavitation similarity law and characteristic curve fitting. This relationship is then embedded into the DCS control logic in real time for dynamic calculation. Q critical The fixed threshold is replaced as the basis for opening the recirculation valve, and it is linked with the pre-pump-main pump configuration identification.

[0032] Furthermore, the critical cavitation safety flow rate Q critical According to the cavitation similarity law of pumps, the real-time speed of the main feedwater pump is determined. n and real-time ingress pressure P in The fitting function is determined by means of a cavitation characteristic curve data provided by the pump manufacturer, obtained through polynomial fitting or table lookup interpolation, and satisfies the following: when n Reduce or P in When it decreases, Q critical The pattern of increasing accordingly.

[0033] When the actual flow rate Q of the main pump drops to Q critical When Q is within the range of 1.05 to 1.10 times, a quick-opening command for the recirculation valve is issued (e.g., quick-opening to 30% to 50% opening); when Q is lower than Q critical At that time, continuous PID adjustment is performed according to the deviation to ensure that the flow rate quickly crosses the cavitation danger zone. This process can open the recirculation valve in advance and quickly to ensure that the flow rate in the pump quickly crosses the cavitation danger zone.

[0034] In some embodiments, the function f can be fitted to the following example form: ,in k 1. k 2. k 3 represents the fitting coefficient.

[0035] Those skilled in the art will understand that, depending on the specific pump type, the function f can also be other linear or nonlinear fitting forms, such as polynomial form, piecewise linear form, or lookup table interpolation form, and the present invention does not limit it in this regard.

[0036] In anti-cavitation priority mode, the control loop is based on Q critical A single-loop regulation is constructed using the setpoint and the actual flow rate Q of the main pump as the process value. Preferably, the proportional gain of this loop is set relatively large, enabling the recirculation valve to operate quickly when the actual flow rate approaches the cavitation danger zone; simultaneously... Q criticalThe deviation signal from Q is introduced into the feedforward channel to further enhance the response speed. In some embodiments, the recirculation valve operates using a graded strategy: when Q approaches... Q critical When this is done, first quickly open the recirculation valve to the preset opening degree (e.g., 30% to 50%) to allow the flow rate in the pump to quickly pass through the cavitation danger zone, and then switch to continuous regulation to avoid frequent small valve movements, thus balancing safety and valve life.

[0037] Furthermore, the accuracy of dynamic calculations depends on the inlet pressure. P in For measurement accuracy, a high-precision pressure transmitter is preferably installed on the inlet pipe of the main feed water pump (e.g., at the straight pipe section after the inlet filter), with an accuracy class preferably of 0.075 or better than 0.1. The real-time speed n of the main pump can be obtained by a key phase sensor or speed transmitter. The feed water flow signal can be obtained by a flow measurement device (such as a flow nozzle or differential pressure flow meter) after temperature and pressure compensation.

[0038] The core of this mode is to change the recirculation valve's trigger logic from a minimum flow rate to a safe flow rate to mitigate cavitation risk. This is achieved by monitoring the main pump speed in real time. n and inlet pressure P in According to the pump's cavitation similarity criterion (e.g., cavitation specific speed), C (Maintaining a constant flow rate) dynamically calculates the critical safe flow rate to ensure no cavitation under current operating conditions. Q critical This value typically varies with rotational speed. n The decrease leads to an increase; this model sacrifices a small amount of economic efficiency in exchange for high security of critical equipment.

[0039] S32, Activate Thermal Control Optimization Mode. For this type of system, the booster pump operates at a constant speed under low load, maintaining a high inlet pressure for the main pump and minimizing cavitation risk. The main constraint limiting the main pump's low-flow operation is the temperature rise of the working fluid within the pump. The core of this mode is to shift the control objective from maintaining a fixed flow rate to controlling the pump body temperature rise, minimizing ineffective recirculation while ensuring thermal safety. The real-time temperature rise of the main feedwater pump serves as the primary basis for controlling the opening of the recirculation valve. When the real-time temperature rise is below a safety threshold, the main feedwater pump is allowed to operate below a preset fixed flow rate threshold without opening or with only partial opening of the recirculation valve.

[0040] In the thermal control optimization mode, the control logic includes: when Δ T <Δ T warn When Δ T warn ≤Δ T <ΔT trip At that time, adjust the opening of the recirculation valve to make Δ T Falling back to Δ T warn The following; where Δ T warn The temperature rise warning value is Δ. T trip The temperature rise trip value, and Δ T trip >Δ T warn When Δ T >Δ T trip At that time, regardless of the flow rate and the calculated temperature rise, the overdrive fully opens the recirculation valve and triggers the pump unit protection interlock.

[0041] In the thermal control optimization mode, the real-time temperature rise ΔT of the main feedwater pump can be obtained through one or a combination of the following two methods.

[0042] Method 1, the real-time temperature rise Δ of the main feedwater pump T The calculation was obtained through a thermal balance model, and the formula is as follows:

[0043] in, Real-time temperature rise calculation, K; W shaft The estimated pump shaft power, W; W hydraulic Hydraulic power obtained from the fluid, W; c p is the specific heat capacity of water, J / (kg·K); m The mass flow rate is measured in kg / s; or it can be obtained directly by measuring the temperature at a point set on the pump casing or sealing cavity.

[0044] Method 2, direct measurement: The temperature rise of the medium is directly measured by a temperature sensing element installed near the pump casing, sealing cavity, or non-drive end bearing to obtain the real-time temperature rise measurement value Δ. T direc The temperature rise of the medium is calculated from the difference between the pump inlet and outlet feed water temperature measuring points to reflect the most unfavorable heat concentration location inside the pump. Preferably, the temperature measuring points include thermocouples set near the bearing at the non-drive end of the pump and at the sealing gland to reflect the thermal state of the most unfavorable location inside the pump.

[0045] More preferably, it can simultaneously consider both the real-time temperature rise calculation value and the real-time temperature rise calculation value, and include Δ T calc As the primary monitoring target, Δ T direcFor verification and backup: When the deviation between the two exceeds a preset deviation value (e.g., 5℃), an alarm for abnormal measurement point is issued. When Δ T direc When the temperature rise trip value is reached, regardless of Δ T calc Regardless of the flow rate, the recirculation valve will be fully opened immediately.

[0046] Furthermore, the temperature rise warning value Δ T warn The preferred setting is 60% to 80% of the maximum temperature rise allowed by the pump manufacturer; the temperature rise trip value Δ T trip Preferably, the value is set to be no less than the manufacturer's maximum allowable temperature rise, and Δ T trip Greater than Δ T warn For example, when the manufacturer allows a maximum temperature rise of 20°C, Δ T warn It can be set to 15℃; considering the heat transfer lag and local heat concentration at the metal temperature measuring point, Δ T trip The temperature can be set to 30℃. The above values ​​are for illustrative purposes only and can be adjusted according to the pump type and manufacturer's requirements in actual applications. This invention does not limit these adjustments.

[0047] By establishing a real-time thermal balance model of the main pump (using pump inlet and outlet parameters to calculate temperature rise Δ) T Alternatively, the pump casing temperature can be directly measured to monitor the pump's thermal state in real time. The process control logic is set to: as long as the real-time temperature rise Δ... T If the main pump flow rate is lower than the preset safety warning value, even if the main pump flow rate is lower than the preset safety warning value. Q This is already below the traditional fixed threshold, allowing the recirculation valve to remain closed or only slightly open. When Δ T Approaching Δ T warn Then, the recirculation valve is adjusted proportionally to control the temperature rise by introducing cooling water flow. This mode, while ensuring equipment safety, minimizes ineffective backflow and improves economic efficiency.

[0048] Specifically, when ΔT < 0.9ΔT warn When, keep the recirculation valve closed; when 0.9ΔT warn ≤ΔT<ΔT warn At that time, the recirculation valve is slightly opened according to a preset slope for pre-cooling; when ΔT warn ≤ΔT<ΔT trip At that time, the PID control is performed by adjusting the opening of the recirculation valve to bring ΔT back to 0.9ΔT. warn The following applies when ΔT ≥ ΔT trip Immediately overdrive and fully open the recirculation valve.

[0049] To prevent protection failure due to thermal balance model failure or temperature measurement point malfunction, preferably, an absolute minimum flow rate value much lower than the traditional fixed flow rate threshold is still set in thermal control optimization mode. Q floor (For example, 10% to 15% of the rated flow of the main pump), when the actual flow of the main pump is lower than Q floor In this mode, the recirculation valve is activated regardless of the real-time temperature rise, serving as a final safety net.

[0050] S4, safety boundary protection, real-time monitoring of the vibration and metal temperature parameters of the main feed water pump, when any parameter exceeds the safety limit, the override control opens the recirculation valve.

[0051] Regardless of the operating mode, a final safety barrier based on direct physical quantity monitoring is established. The main pump's bearing vibration, shaft displacement, and critical metal temperatures are continuously monitored. If any parameter exceeds the trip value, an override signal is immediately triggered, forcing the recirculation valve to fully open to ensure equipment safety. Bearing vibration includes two mutually perpendicular directions, and shaft displacement and critical metal temperatures include thrust bearing bearing temperature, pump casing temperature, and sealing water temperature. These monitoring signals preferably originate from safety monitoring instruments independent of the control system (e.g., a turbine safety monitoring system (TSI)) and are hardwired to the override terminal of the recirculation valve control output channel with the highest priority.

[0052] A second aspect of the present invention discloses a deep peak-shaving adaptive minimum flow control system based on a feedwater pump configuration, comprising: The data acquisition module is used to acquire real-time data including the main feed water pump speed, flow rate, inlet and outlet pressure, temperature, and the power coupling relationship signal of the booster pump; The configuration identification module, connected to the data acquisition module, is used to determine the system configuration based on the power coupling relationship signal of the pre-pump; this module acts as the "brain" of the entire system and is responsible for system type determination.

[0053] The strategy control module, connected to the configuration identification module, has embedded anti-cavitation priority control algorithm and thermal control optimization control algorithm. It is used to call the corresponding control algorithm according to the output of the configuration identification module and generate recirculation valve control instructions. This module serves as a "strategy library" and has embedded two sets of parallel optimization control algorithms.

[0054] The execution and protection module includes a recirculation regulating valve for receiving control commands from the strategy control module.

[0055] The execution and protection module also receives vibration and temperature over-limit signals from an independent safety monitoring instrument, and can override and open the recirculation regulating valve when it receives such signals.

[0056] In some embodiments of the present invention, the data acquisition module further includes a high-precision pressure transmitter installed on the inlet pipeline of the main feedwater pump for accurately measuring the inlet pressure. P in ).

[0057] The following description, in conjunction with specific embodiments, provides further details.

[0058] Example 1 Implementation of a Coaxial Drive System: A 600MW unit uses a steam-driven feedwater pump, with the booster pump and main pump coaxial. To implement this invention, the following work is required: 1. Hardware Enhancement: Install a high-precision, high-reliability pressure transmitter (e.g., accuracy class 0.075) after the main pump inlet filter to ensure the inlet pressure. P in Accurate measurement is the foundation of dynamic calculation.

[0059] 2. Model Calibration: During unit overhaul, the critical cavitation safety flow function was determined through data fitting, using the cavitation performance curves (NPSHr curve family) provided by the pump manufacturer.

[0060] (This is just an example; the actual relationship may be more complex and non-linear.) k 1, k 2, k 3 represents the fitting coefficient.

[0061] 3. Logic configuration: Control loops are configured with... Q critical The set value is based on the actual flow rate of the main pump. Q This forms a single-loop control system, with the process value as the reference value. The proportional gain can be set relatively large, allowing the recirculation valve to act quickly when the flow rate approaches the danger zone. Simultaneously, [the following text appears to be incomplete and requires further context: "...and..."] Q critical and Q The deviation signal is introduced into the feedforward to further enhance the response speed.

[0062] 4. Effect: After implementation, when the unit drops to 40% load, traditional control may activate when the flow rate drops to 28% of the rated flow rate, while this method may start recirculation in advance when the flow rate drops to 35%, thus completely avoiding the risk of cavitation at low speed and low inlet pressure.

[0063] Example 2 Implementation of an independent drive system (A 300MW unit uses an electric feedwater pump, with the booster pump driven by an independent industrial frequency motor. Implementing this invention mainly involves software upgrades:) 1. Utilization and Supplementation of Measuring Points: Existing pressure, temperature, and flow measurement points at the inlet and outlet of the main pump are utilized. For greater reliability, two metal thermocouples are added near the bearing on the non-drive end of the pump and at the sealing gland, serving as Δ... T direct The measured value.

[0064] 2. Thermal Model Establishment: A simplified real-time thermal balance calculation module is established in the DCS. Pump shaft power. W shaft Estimated from motor current, voltage, and efficiency curves. Hydraulic power. W hydraulic From Δ P Q Calculation. Calculated temperature rise Δ T calc As the primary monitoring target, the directly measured value Δ T direct Used for verification and backup.

[0065] 3. Logic configuration: Set two levels of thresholds: warning value Δ T warn =15°C (20°C lower than the manufacturer's maximum allowable temperature), trip value Δ T trip =30°C. During normal operation, the controller monitors Δ T calc When the flow rate decreases, Δ T calc When the temperature rises to 14°C, the controller begins to slightly open the recirculation valve for "pre-cooling"; if Δ T calc Continue to rise to Δ T warn Then it enters the proportional adjustment mode, and Δ T calc Keep the temperature below 15°C. If Δ T direct If the measured temperature reaches 30°C, the recirculation valve should be fully opened immediately, regardless of the calculated value and flow rate.

[0066] 4. Benefits: After implementation, the recirculation valve remains closed most of the time below 50% load, only adjusting briefly during rapid load fluctuations. Statistics show that the average flow rate in the recirculation pipeline decreases by approximately 70%, resulting in a significant reduction in power consumption for the feedwater pump unit. Deep peak-shaving power supply coal consumption is improved by approximately 0.2 grams per kilowatt-hour, leading to annual cost savings exceeding one million yuan.

[0067] System Implementation The system of this invention is integrated as an advanced application (APP) into the existing distributed control system (DCS) of the power plant. The data acquisition module utilizes the DCS's I / O cards to acquire all necessary signals. The configuration identification module and strategy control module are implemented in the DCS control station in the form of function blocks or scripts. The output commands of the execution and protection module are sent to the positioner of the recirculation valve through the DCS's analog output (AO) channel. Simultaneously, the vibration over-limit hardwired signal from the TSI (Turbine Safety Monitoring System) is directly connected to the override terminal of the AO channel with the highest priority. The entire system is seamlessly integrated with the original DCS and works collaboratively.

[0068] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, features defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. In the description of this invention, "above" or "below" a second feature may include direct contact between the first and second features, or it may include contact between the first and second features not being in direct contact but through another feature between them.

[0069] In the description of this invention, the terms "above," "over," and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicating that the first feature is at a higher horizontal level than the second feature.

[0070] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0071] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0072] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A deep peak-shaving adaptive minimum flow control method based on feedwater pump configuration, characterized in that, include: S1, acquire the measurement parameters of the main feed water pump and the real-time data of the power coupling relationship of the booster pump; S2, based on the power coupling relationship of the booster pump in the water supply system, determine whether the booster pump and the main water supply pump are coaxially driven, and select the corresponding minimum flow control mode based on the determination result; S3. If it is a coaxial drive system, the critical cavitation safety flow rate under the current operating condition is dynamically calculated based on the real-time operating parameters of the main feed water pump, and the critical cavitation safety flow rate is used as the basis for controlling the opening of the recirculation valve. If it is a pre-pump independent drive system, the real-time temperature rise of the main feed water pump is used as the basis for controlling the opening of the recirculation valve. When the real-time temperature rise is lower than the safety threshold, the main feed water pump is allowed to operate under conditions lower than the preset fixed flow threshold without opening or partially opening the recirculation valve. S4. Monitor the vibration parameters and metal temperature parameters of the main water pump in real time. When any parameter exceeds the corresponding safety limit, the override control opens the recirculation valve.

2. The deep peak shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 1, characterized in that, In S1, the main feed water pump measurement parameters include the main feed water pump speed, flow rate, inlet pressure, outlet pressure, and temperature.

3. The deep peak shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 1, characterized in that, In S2, the method for determining whether the booster pump and the main feed water pump are coaxially driven includes at least one of the following: Read the design configuration signal stored in the distributed control system (DCS), and determine the power coupling relationship of the booster pump based on the design configuration signal; The real-time speed data of the booster pump and the main feed water pump are obtained. If the speed of the booster pump and the speed of the main feed water pump change synchronously during the unit load change, it is determined to be coaxial drive; if the speed of the main feed water pump changes with the load while the speed of the booster pump remains constant, it is determined to be independent drive of the booster pump.

4. The deep peak shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 1, characterized in that, In S3, the formula for calculating the critical cavitation safety flow rate is: Q critical = f ( n , P in ) in, n Real-time speed of the main feed water pump P in The main feedwater pump's real-time inlet pressure; the function f It was determined by the cavitation similarity law of the pump and the fitting of characteristic curves.

5. The deep peak shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 4, characterized in that, The process of using the critical cavitation safety flow rate as the basis for controlling the opening of the recirculation valve is as follows: a feedback control loop is formed with the critical cavitation safety flow rate as the set value and the actual flow rate of the main pump as the process value; at the same time, the rate of change of the main feed water pump speed and / or the rate of change of the inlet pressure are introduced as feedforward signals.

6. The deep peak shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 1, characterized in that, The real-time temperature rise of the main feedwater pump is obtained through any of the following methods: The real-time temperature rise is calculated based on a real-time thermal balance model, which calculates the real-time temperature rise according to the estimated pump shaft power, the hydraulic power obtained by the fluid, the specific heat capacity of water, and the mass flow rate of the feed water. The temperature is obtained directly by measuring the temperature of the pump casing, sealing cavity, or inlet / outlet medium of the main feed water pump.

7. The deep peak shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 6, characterized in that, Using the real-time temperature rise of the main feedwater pump as the basis for controlling the opening of the recirculation valve, during the control process, when Δ T <Δ T warn When Δ T warn ≤ Δ T <Δ T trip At that time, adjust the opening of the recirculation valve to make Δ T Falling back to Δ T warn The following; when Δ T >Δ T trip At that time, the overdrive fully opens the recirculation valve and triggers the pump unit protection interlock; among which, Δ T For real-time temperature rise, Δ T warn The temperature rise warning value is Δ. T trip This is the temperature rise trip value.

8. The deep peak shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 7, characterized in that, The temperature rise warning value Δ T warn The temperature rise is 60% to 80% of the maximum allowable temperature rise by the pump manufacturer; the temperature rise trip value Δ T trip The value shall not be less than the manufacturer's maximum allowable temperature rise.

9. The deep peak-shaving adaptive minimum flow control method based on feedwater pump configuration according to claim 1, characterized in that, The override control includes: Acquire vibration and temperature over-limit signals from independent safety monitoring instruments; When any of the aforementioned over-limit signals is received, the recirculation valve is forcibly opened to the fully open position with the highest priority.

10. A deep peak-shaving adaptive minimum flow control system based on a feedwater pump configuration, characterized in that, include: The data acquisition module is used to acquire the measurement parameters of the main feed water pump and the real-time data of the power coupling relationship of the booster pump; The configuration identification module is used to determine whether the pre-pump and the main water supply pump are coaxially driven based on the power coupling relationship of the pre-pump in the water supply system, and select the corresponding minimum flow control mode based on the determination result. The strategy control module is used to execute the minimum flow control mode. If it is a coaxial drive system, it dynamically calculates the critical cavitation safety flow under the current operating conditions based on the real-time operating parameters of the main feed water pump, and uses the critical cavitation safety flow as the basis for controlling the opening of the recirculation valve. If it is a pre-pump independent drive system, the real-time temperature rise of the main feed water pump is used as the basis for controlling the opening of the recirculation valve. When the real-time temperature rise is lower than the safety threshold, the main feed water pump is allowed to operate under conditions lower than the preset fixed flow threshold without opening or partially opening the recirculation valve. The execution and protection module is used to monitor the vibration parameters and metal temperature parameters of the main feed water pump in real time. When any parameter exceeds the corresponding safety limit, the override control opens the recirculation valve.

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