Coal-fired unit circulating water pump switching under frequency pump optimization benchmark reconstruction method and system

Abstract

The present application belongs to the field of industrial automation and intelligent control technology of thermal power plant, and relates to a method and system for reconstructing the optimization benchmark of frequency conversion pump under the switching of circulating water pump of coal-fired unit. The method collects the frequency, current, load and back pressure operation data of circulating water system in real time; identifies the operation state of double-speed power frequency circulating water pump according to the low-speed block current and high-speed block current; when the change of operation state or operation mode is detected, the old optimization benchmark data is cleared and the benefit evaluation is suspended; after the system meets the stable condition, the new optimization benchmark under the current operation state is established; based on the new benchmark, the power variation of unit side, the power consumption variation of circulating water pump and the net benefit are calculated, and the frequency adjustment instruction or frequency suggestion value of frequency conversion circulating water pump is output according to the net benefit. The present application can avoid the interference of the start-stop or gear change of double-speed power frequency circulating water pump on the frequency optimization benchmark of frequency conversion circulating water pump, and improve the accuracy and operation stability of frequency optimization judgment.

Description

Technical Field

[0001] This invention belongs to the field of industrial automation and intelligent control technology for thermal power plants, specifically relating to a method and system for reconstructing the optimization benchmark of a variable frequency pump during the switching of circulating water pumps in coal-fired units. Background Technology

[0002] As a core auxiliary equipment in thermal power plants, circulating water pumps primarily supply cooling water to the turbine condenser. They maintain condenser vacuum by absorbing the latent heat of condensation from the turbine exhaust steam, ensuring the safe and economical operation of the turbine. Existing circulating water systems in thermal power units generally employ a combined operation architecture of variable frequency pumps and dual-speed fixed frequency pumps. The variable frequency pumps achieve continuously adjustable circulating water flow through frequency regulation; the dual-speed fixed frequency pumps achieve high and low speed operation by switching the stator winding connection method, and the high and low speeds cannot be operated simultaneously. When unit load or ambient water temperature changes, the circulating water pump operation combination mode needs to be switched to match the condenser cooling demand, avoiding energy waste due to excessive water supply or unit vacuum and output degradation due to insufficient water supply.

[0003] The start-up, shutdown, and high / low speed switching processes of frequency pumps generate significant electrical transients and flow step disturbances, causing drastic changes in total circulating water flow, total pump power consumption, and condenser back pressure. Existing intelligent optimization control technology for variable frequency pumps relies on an economic net benefit evaluation logic to optimize frequency: the system collects operating parameters such as unit load, condenser back pressure, and variable frequency pump operating frequency, calculates the increase in unit power and the change in pump power consumption resulting from frequency adjustment, obtains the economic net benefit through the difference between the two, and determines the direction of frequency adjustment based on the positive or negative sign of the net benefit. This solution exhibits good adaptability under conditions where the variable frequency pump operates independently and the pump combination mode is fixed.

[0004] However, existing optimization control schemes have inherent defects in multi-pump combination mode switching conditions: when the switching of dual-speed power frequency pumps and the switching of high and low speed gears cause a step change in system parameters, the optimization program still uses the historical baseline data before the switching, such as the change in computer group power, pump consumption and net economic benefits. This will incorrectly determine the system disturbance caused by the switching of power frequency pump status as the control effect produced by the frequency adjustment of variable frequency pump.

[0005] If the fixed frequency pump is put into operation, the system circulating water volume increases, the condenser back pressure decreases, and the unit output power increases. The existing optimization logic tends to attribute this positive benefit to the frequency reduction of the variable frequency pump, and then continuously lowers the frequency of the variable frequency pump, which can easily lead to the low-frequency operation of the variable frequency pump and instability of the system. Conversely, when the fixed frequency pump is shut down, the circulating water volume decreases, the back pressure increases, and the unit power decreases. The optimization program will mistakenly judge the deterioration of the operating conditions as the loss caused by the frequency increase of the variable frequency pump, and frequently reverse the frequency of the variable frequency pump.

[0006] The aforementioned misjudgment issues will lead to multiple operational drawbacks: First, the direction of optimization and control will be fundamentally deviated; second, the operating frequency of the variable frequency pump will fluctuate frequently; third, it will be impossible to accurately locate the true economically optimal operating point under the current pump combination mode; fourth, the overall system will have poor operational stability, and the frequency will fluctuate significantly during the pump combination mode switching phase.

[0007] Existing technologies lack a benchmark data update mechanism for pump combination mode switching scenarios. They cannot automatically identify power frequency pump switching and gear shifting disturbance events, and cannot promptly clear the old optimization benchmark before switching and rebuild the optimization benchmark adapted to the current combination mode after the system operating conditions stabilize. It is difficult to eliminate the interference of operating condition step disturbances on the economic optimization results of variable frequency pumps, and there are significant technical shortcomings.

[0008] Therefore, there is an urgent need for a method that can automatically identify switching events, clear old optimization benchmarks, wait for the system to stabilize, and rebuild new optimization benchmarks when the combined pump operating mode is switched, in order to solve the above-mentioned technical problems. Summary of the Invention

[0009] This invention aims to introduce an optimization benchmark reconstruction mechanism into the frequency optimization control of variable frequency circulating water pumps. By identifying changes in the operating status of dual-speed power frequency circulating water pumps or changes in the operating mode of combined pumps, clearing the old benchmark, judging system stability, and reconstructing a new benchmark, the control strategy avoids interference caused by the start-up, shutdown, or gear changes of dual-speed power frequency circulating water pumps on the frequency optimization of variable frequency pumps.

[0010] This invention provides the following technical solution: a method for reconstructing the optimization benchmark of a variable frequency pump during circulating water pump switching in a coal-fired power unit, comprising the following steps: Step S1: Collect real-time operating data of the circulating water system. The operating data should include at least the actual frequency feedback of the variable frequency circulating water pump, the low-speed current of the dual-speed power frequency circulating water pump, the high-speed current of the dual-speed power frequency circulating water pump, the actual load of the unit, and the condenser back pressure.

[0011] Step S2: Identify the operating status of the dual-speed industrial frequency circulating water pump based on the low-speed and high-speed currents of the dual-speed industrial frequency circulating water pump. The operating status includes shutdown status, low-speed operation status, high-speed operation status, and switching status or uncertain status.

[0012] Step S3: Determine the combined pump operating mode based on the operating status of the variable frequency circulating water pump and the dual-speed fixed frequency circulating water pump, and determine whether the current combined pump operating mode has changed compared to the combined pump operating mode under the previous stable operating condition.

[0013] Step S4: When a change in the operating status of the dual-speed power frequency circulating water pump or the operating mode of the combined pump is detected, the optimization benchmark data of the previous stable operating condition is cleared, and the benefit evaluation of the frequency adjustment action of the variable frequency circulating water pump is stopped within the preset stable waiting time.

[0014] Step S5: When the dual-speed power frequency circulating water pump operates stably, the actual frequency feedback of the variable frequency circulating water pump meets the preset frequency stability condition, the actual load of the unit meets the preset load stability condition, and the condenser back pressure meets the preset back pressure stability condition, a new frequency optimization benchmark is established under the current operating condition.

[0015] Step S6: Based on the new frequency optimization benchmark, calculate the change in unit-side power, the change in power consumption of the circulating water pump, and the net benefit before and after the frequency adjustment of the variable frequency circulating water pump, and output the frequency adjustment command or frequency recommendation value of the variable frequency circulating water pump according to the net benefit.

[0016] Preferably, in step S2, identifying the operating status of the dual-speed power frequency circulating water pump specifically includes: When the low-speed current of the dual-speed industrial frequency circulating water pump is within the preset low-speed operating current range and the high-speed current is less than the preset shutdown current threshold, the dual-speed industrial frequency circulating water pump is determined to be in low-speed operation mode.

[0017] When the high-speed current of the dual-speed industrial frequency circulating water pump is within the preset high-speed operating current range and the low-speed current is less than the preset shutdown current threshold, the dual-speed industrial frequency circulating water pump is determined to be in high-speed operation mode.

[0018] When both the low-speed and high-speed currents are less than the preset shutdown current threshold, the dual-speed power frequency circulating water pump is determined to be in a shutdown state.

[0019] When neither the low-speed current nor the high-speed current meets the above criteria, the dual-speed industrial frequency circulating water pump is determined to be in gear switching or in an uncertain state.

[0020] Preferably, in step S3, determining the operating mode of the combined pump specifically includes: When the dual-speed industrial frequency circulating water pump is in a stopped state, the combined pump operation mode is determined to be mode 0.

[0021] When the dual-speed industrial frequency circulating water pump is in low-speed operation mode, the combined pump operation mode is determined to be mode 1.

[0022] When the dual-speed industrial frequency circulating water pump is in high-speed operation, the combined pump operation mode is determined to be mode 2.

[0023] When the dual-speed industrial frequency circulating water pump is in the process of gear switching or in an uncertain state, the combined pump operation mode is determined to be mode 3, and the benefit evaluation is suspended, and no new optimization benchmark is established.

[0024] Preferably, in step S4, clearing the optimization baseline data of the previous stable operating condition specifically includes: Clear the reference frequency, reference back pressure, and reference load of the previous stable operating condition.

[0025] Remove the calculated changes in unit-side power, changes in circulating water pump power consumption, and net revenue.

[0026] Reset the optimization direction flag and reset the trial status flag.

[0027] Clear historical data cache.

[0028] Record the moment of mode switching and set the benchmark reconstruction flag to true to pause the output of profit evaluation and frequency adjustment instructions based on the old benchmark.

[0029] Preferably, in step S5, determining whether the system meets the stability condition specifically includes: Determine whether the operating mode of the combined pump remains unchanged within the preset stable waiting time.

[0030] Determine whether the difference between the actual frequency feedback and the frequency command of the variable frequency pump is less than the preset frequency tolerance.

[0031] The sliding window statistical method is used to determine the unit load fluctuation. When the difference between the maximum and minimum unit load within the preset time window is less than the preset load threshold, the load is determined to be stable.

[0032] The sliding window statistical method is used to determine the condenser back pressure fluctuation. When the difference between the maximum and minimum condenser back pressure within the preset time window is less than the preset back pressure threshold, the back pressure is determined to be stable.

[0033] Based on a comprehensive assessment of all stability conditions, the system is considered to be stable only when all four conditions—combined pump mode stability, frequency stability, load stability, and back pressure stability—are met simultaneously.

[0034] More preferably, the preset stabilization waiting time is 30-300 seconds; the preset frequency tolerance is 0.3-1.0Hz; the preset load threshold is 5-20MW; and the preset back pressure threshold is 0.2-1.0kPa.

[0035] Preferably, in step S5, establishing a new frequency optimization benchmark specifically includes: Collect the current frequency of the variable frequency pump as the new reference frequency.

[0036] The current condenser back pressure is collected as the new reference back pressure.

[0037] Collect the current unit load as the new baseline load.

[0038] Select the corresponding pump consumption curve coefficient based on the current combined pump operating mode.

[0039] Zeroing out changes in unit power, circulating water pump power consumption, and net revenue.

[0040] Clear the baseline reconstruction flag and restore the frequency optimization logic.

[0041] More preferably, the pump consumption curve coefficients vary depending on the operating mode of the combined pump, and different operating modes of the combined pump correspond to different sets of pump consumption curve coefficients; the pump consumption relationship adopts a polynomial form, piecewise fitting, tabular interpolation, or a pump consumption model established from historical operating data.

[0042] Preferably, in step S6, calculating the net benefit and outputting the frequency adjustment instruction or suggested value specifically includes: Based on the changes in current back pressure and new reference back pressure, the change in power on the computer side is calculated through back pressure power correction relationship, unit characteristic curve, radial basis function interpolation model or historical operation data statistical model.

[0043] Based on the changes in the current frequency and the new reference frequency, and combined with the pump consumption curve coefficient corresponding to the current combined pump mode, the change in power consumption of the circulating water pump is calculated.

[0044] The net benefit is calculated as the difference between the change in unit power and the change in power consumption of the circulating water pump.

[0045] Determine whether the net income meets the preset economic conditions. The preset economic conditions include that the net income is greater than the preset economic dead zone, the condenser back pressure is within the preset effective range of back pressure, and the condenser back pressure is less than the preset back pressure high limit protection value.

[0046] When the net income meets the preset economic conditions, continue to adjust the frequency along the current optimization direction; when the net income does not meet the preset economic conditions, execute the frequency rollback, maintain the frequency, or lock the current frequency.

[0047] This invention also discloses a system for reconstructing the optimization benchmark of a variable frequency pump during the switching of a circulating water pump in a coal-fired power unit. This reconstruction system is used to implement the above-mentioned reconstruction method and includes: The data acquisition module is used to collect real-time feedback of the actual frequency of the variable frequency circulating water pump, the low-speed current of the dual-speed power frequency circulating water pump, the high-speed current of the dual-speed power frequency circulating water pump, the actual load of the unit, and the condenser back pressure.

[0048] The status recognition module is used to identify the operating status of the dual-speed power frequency circulating water pump based on the low-speed and high-speed current of the dual-speed power frequency circulating water pump, and to determine the combined pump operating mode based on the operating status of the variable frequency circulating water pump and the dual-speed power frequency circulating water pump.

[0049] The switching detection module is used to compare the current combined pump operating mode with the combined pump operating mode recorded in the previous sampling period to detect whether a mode switch has occurred.

[0050] The baseline clearing module is used to clear the optimization baseline data of the previous stable operating condition and set the baseline reconstruction flag when a change in the operating status of the dual-speed power frequency circulating water pump or a change in the operating mode of the combined pump is detected.

[0051] The stability determination module is used to determine whether the system meets the stability conditions.

[0052] The benchmark reconstruction module is used to collect current operating parameters and select the corresponding pump consumption curve coefficients according to the current combined pump operating mode when the system meets the stability conditions, and establish a new optimization benchmark.

[0053] The frequency optimization module is used to output frequency adjustment commands or frequency recommendations based on the power change of the computer group side, the power consumption change of the circulating water pump, and the net benefit, according to whether the net benefit meets the preset economic conditions.

[0054] The beneficial effects of this invention are: 1. This invention can improve the accuracy of frequency optimization for variable frequency pumps. The invention adds an optimization benchmark reconstruction mechanism, which can accurately identify events such as the start-up and shutdown of dual-speed fixed frequency pumps, high and low speed gear switching, and pump combination operation mode switching. It can promptly clear the old optimization benchmark before the switching, avoid the defect of misjudging the step disturbance of the fixed frequency pump operating condition as the frequency regulation effect of the variable frequency pump, ensure the rationality of the optimization direction judgment logic, and greatly improve the accuracy of the unit's cold end frequency optimization results.

[0055] 2. This invention can improve the operational stability of the circulating water system. Existing optimization methods are prone to problems such as frequent frequency reversals and abnormal adjustments of the variable frequency pump due to misjudgments caused by operating condition disturbances. After switching the pump combination mode, this invention waits for the circulating water system flow rate, pump consumption, and condenser back pressure parameters to stabilize before reconstructing the optimization benchmark. This eliminates the parameter step shock caused by switching on the fixed frequency pump, helps reduce the risk of large fluctuations in the operating frequency of the variable frequency pump, reduces the interference of severe condenser vacuum fluctuations on economic benefit evaluation, and effectively improves the operational stability of the entire circulating water system.

[0056] 3. This invention is adaptable to multi-pump combined operation in all scenarios. The benchmark reconstruction strategy of this invention is compatible with various circulating water pump operation combination modes, covering all actual engineering conditions such as variable frequency pumps operating alone, variable frequency pumps paired with fixed frequency pumps operating at low speed, and variable frequency pumps paired with fixed frequency pumps operating at high speed. Whenever the pump combination operation mode changes, the system can automatically reconstruct an independent optimization benchmark adapted to the current operating condition. Based on the new benchmark, the system performs frequency adjustment economic benefit calculations and optimization control of the variable frequency pumps, resulting in stronger adaptability to operating conditions.

[0057] 4. This invention is highly practical for engineering implementation and requires no additional hardware modification costs. The invention can realize the entire control logic by relying on the existing DCS system of thermal power plants to collect conventional signals. The required measurement points include the original monitoring equipment of the power plant such as unit load measurement points, condenser back pressure measurement points, and circulating water pump current measurement points. There is no need to add new sensors, controllers, or other hardware equipment. The modification investment is low and it is easy to promote and apply in existing thermal power units.

[0058] 5. This invention has a high level of automation, reducing the burden of manual operation and maintenance. The entire optimization benchmark reconstruction process of this invention is fully automated. It can autonomously identify water pump operation status switching events, automatically clear historical optimization benchmarks, automatically determine the stable state of system operation, and autonomously complete the reconstruction and switching of new optimization benchmarks. This reduces manual intervention by operators, effectively reduces the workload of daily monitoring and manual parameter correction by operators, and lowers the cost of manual operation and maintenance.

[0059] 6. This invention has a wide range of applications; This invention is specifically designed for the optimized control scenario of the cold end of thermal power units that are equipped with both variable frequency circulating water pumps and dual-speed industrial frequency circulating water pumps. It can be widely applied to various coal-fired power generating units equipped with this circulating water system architecture. The application scenarios cover various actual production conditions such as unit load changes, ambient water temperature changes, and frequent switching of water pump combination modes. Attached Figure Description

[0060] Figure 1 This is a schematic diagram of the method and system for reconstructing the optimization benchmark of the variable frequency pump during the switching of the circulating water pump in a coal-fired unit according to the present invention; Figure 2 This is a schematic diagram of the combined pump pattern recognition logic according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the timing of the baseline freeze and reconstruction after the operating state of the dual-speed power frequency circulating water pump changes according to an embodiment of the present invention. Detailed Implementation

[0061] The relevant technologies of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0062] like Figures 1-3 As shown, the method for reconstructing the optimization benchmark of the variable frequency pump during the switching of the circulating water pump in a coal-fired unit according to this embodiment includes the following steps: Step S1: Collect real-time operating data of the circulating water system. The operating data includes the actual frequency feedback of the variable frequency circulating water pump, the low-speed current of the dual-speed power frequency circulating water pump, the high-speed current of the dual-speed power frequency circulating water pump, the actual load of the unit, and the condenser back pressure.

[0063] Step S2: Identify the operating status of the dual-speed industrial frequency circulating water pump based on the low-speed and high-speed currents of the dual-speed industrial frequency circulating water pump. The operating status includes shutdown, low-speed operation, high-speed operation, and switching or uncertain status.

[0064] Step S3: Determine the combined pump operating mode based on the operating status of the variable frequency circulating water pump and the dual-speed fixed frequency circulating water pump, and determine whether the current combined pump operating mode has changed compared to the combined pump operating mode under the previous stable operating condition.

[0065] Step S4: When a change in the operating status of the dual-speed power frequency circulating water pump or the operating mode of the combined pump is detected, the optimization benchmark data of the previous stable operating condition is cleared, and the benefit evaluation of the frequency adjustment action of the variable frequency circulating water pump is stopped within the preset stable waiting time.

[0066] Step S5: When the dual-speed power frequency circulating water pump operates stably, the actual frequency feedback of the variable frequency circulating water pump meets the preset frequency stability condition, the actual load of the unit meets the preset load stability condition, and the condenser back pressure meets the preset back pressure stability condition, a new frequency optimization benchmark is established under the current operating condition.

[0067] Step S6: Based on the new frequency optimization benchmark, calculate the change in unit-side power, the change in power consumption of the circulating water pump, and the net benefit before and after the frequency adjustment of the variable frequency circulating water pump, and output the frequency adjustment command or frequency recommendation value of the variable frequency circulating water pump according to the net benefit.

[0068] Furthermore, the data acquisition, status identification, and combined pump mode determination process includes: Step S11: Obtain real-time operating data of the circulating water system from the distributed control system (DCS) or data acquisition system. The operating data includes: actual frequency feedback of the variable frequency circulating water pump, low-speed current of the dual-speed power frequency circulating water pump, high-speed current of the dual-speed power frequency circulating water pump, actual unit load, condenser vacuum or condenser back pressure, atmospheric pressure and other operating parameters.

[0069] Step S12: When the low-speed current of the dual-speed frequency circulating water pump is within the preset low-speed operating current range and the high-speed current is less than the preset shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in low-speed operation mode; when the high-speed current of the dual-speed frequency circulating water pump is within the preset high-speed operating current range and the low-speed current is less than the preset shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in high-speed operation mode; when both the low-speed current and the high-speed current are less than the preset shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in shutdown mode; when neither the low-speed current nor the high-speed current meets the above determination conditions, the dual-speed frequency circulating water pump is determined to be in gear switching or in an uncertain state.

[0070] Step S13: Determine the combined pump operating mode based on the operating status of the variable frequency circulating water pump and the dual-speed fixed frequency circulating water pump; when the dual-speed fixed frequency circulating water pump is stopped, it is determined to be mode 0; when the dual-speed fixed frequency circulating water pump is running at low speed, it is determined to be mode 1; when the dual-speed fixed frequency circulating water pump is running at high speed, it is determined to be mode 2; when the dual-speed fixed frequency circulating water pump is in gear switching or in an uncertain state, it is determined to be mode 3, and the revenue evaluation is suspended, no new benchmark is established, and the status is awaited for confirmation.

[0071] Furthermore, step S4 specifically includes: clearing the reference frequency, reference back pressure, and reference load of the previous stable operating condition; clearing the calculated unit-side power change ΔNd, circulating water pump power consumption change ΔNp, and net gain net_gain; resetting the optimization direction flag and the trial status flag; clearing the historical data cache; recording the mode switching time; setting the reference reconstruction flag to True, and pausing the output of the benefit evaluation and frequency adjustment command based on the old reference.

[0072] Furthermore, in step S5, the method for determining system stability includes: Step S51. Determine whether the combined pump operating mode remains unchanged within the preset stable waiting time. The preset stable waiting time is set to 30-300 seconds, preferably 60 seconds.

[0073] Step S52. Determine whether the difference between the actual frequency feedback and the frequency command of the variable frequency pump is less than the preset frequency tolerance. The preset frequency tolerance is set to 0.3-1.0Hz, preferably 0.5Hz.

[0074] Step S53. Use the sliding window statistical method to judge the unit load fluctuation. When the difference between the maximum and minimum unit load within the preset time window is less than the preset load threshold, the load is determined to be stable. The preset load threshold is set to 5-20MW, preferably 10MW.

[0075] Step S54. Use the sliding window statistical method to determine the condenser back pressure fluctuation. When the difference between the maximum and minimum values ​​of the condenser back pressure within the preset time window is less than the preset back pressure threshold, the back pressure is determined to be stable. The preset back pressure threshold is set to 0.2-1.0 kPa, preferably 0.5 kPa.

[0076] Step S55. Comprehensively judge all stability conditions. Only when the four conditions of stable combined pump mode, stable frequency, stable load, and stable back pressure are met simultaneously can the system be judged to be stable overall and can enter the benchmark reconstruction stage.

[0077] Furthermore, in step S5, establishing a new frequency optimization benchmark specifically includes: Step S56. Collect the current frequency of the variable frequency pump as the new reference frequency base_freq.

[0078] Step S57. Collect the current condenser back pressure as the new reference back pressure base_pressure. The condenser back pressure can be calculated by directly reading the absolute back pressure measurement point of the condenser, or by subtracting the condenser vacuum degree from the atmospheric pressure, or by calculating the average value after taking the values ​​from multiple condenser vacuum degree measurement points.

[0079] Step S58. Collect the current unit load as the new base load base_load.

[0080] Step S59. Select the corresponding pump consumption curve coefficients (h0, h1, h2, h3) according to the current combined pump mode. The pump consumption curve coefficients vary depending on the combined pump operating mode, and different combined pump operating modes correspond to different sets of pump consumption curve coefficients. In this embodiment, the pump consumption relationship adopts a cubic polynomial form: Np = h0 + h1·f + h2·f² + h3·f³. In other embodiments, the pump consumption relationship can also adopt piecewise fitting, tabular interpolation, or a pump consumption model established from historical operating data.

[0081] Step S510. Reset the unit-side power change ΔNd, circulating water pump power consumption change ΔNp, and net gain net_gain.

[0082] Step S511. Clear the reference reconstruction flag to False and restore the frequency optimization logic.

[0083] Furthermore, step S6 specifically includes: Step S61. Based on the changes in current back pressure and new reference back pressure, calculate the change in unit-side power ΔNd using the back pressure power correction relationship, the unit characteristic curve, the radial basis function interpolation model, or the historical operating data statistical model.

[0084] Step S62. Based on the changes in the current frequency current_freq and the new reference frequency base_freq, and combined with the pump consumption curve coefficient corresponding to the current combined pump mode, calculate the change in circulating water pump power consumption ΔNp.

[0085] Step S63. Calculate the net income net_gain = ΔNd - ΔNp.

[0086] Step S64. Determine whether the net income meets the preset economic conditions. The preset economic conditions include: the net income is greater than the preset economic dead zone, the condenser back pressure is within the preset effective range of back pressure, and the condenser back pressure is less than the preset back pressure high limit protection value.

[0087] Step S65. When the net income meets the preset economic conditions, continue to adjust the frequency along the current optimization direction; when the net income does not meet the preset economic conditions, execute the frequency rollback, frequency maintenance, or lock the current frequency.

[0088] The variable frequency pump optimization benchmark reconstruction system for switching circulating water pumps in coal-fired power units of the present invention is used to implement the variable frequency circulating water pump frequency optimization benchmark reconstruction method. The system includes: The data acquisition module is used to collect real-time feedback on the actual frequency of the variable frequency circulating water pump, the low-speed current of the dual-speed fixed-frequency circulating water pump, the high-speed current of the dual-speed fixed-frequency circulating water pump, the actual load of the unit, and the condenser back pressure. This module is connected to the DCS system or data acquisition system via an interface to periodically read operating data.

[0089] The status recognition module is used to identify the shutdown status, low-speed operation status, high-speed operation status, and switching or uncertain status of the dual-speed industrial frequency circulating water pump based on the low-speed and high-speed current of the dual-speed industrial frequency circulating water pump, and to determine the combined pump operation mode based on the operation status of the variable frequency circulating water pump and the dual-speed industrial frequency circulating water pump.

[0090] The switching detection module compares the current combined pump operating mode with the combined pump operating mode recorded in the previous sampling period to detect whether a mode switch has occurred. This module stores the combined pump mode of the previous period and makes a comparison and judgment in each sampling period.

[0091] The baseline clearing module is used to clear the optimization baseline data of the previous stable operating condition and set the baseline reconstruction flag when a change in the operating status of the dual-speed power frequency circulating water pump or the operating mode of the combined pump is detected. This module is responsible for clearing data such as baseline frequency, baseline back pressure, baseline load, ΔNd, ΔNp, and net_gain, and resetting the relevant flags.

[0092] The stability determination module is used to determine whether the system meets the stability conditions. This module uses a sliding window statistical method to determine the stability of the combined pump mode, frequency stability, load stability, and back pressure stability.

[0093] The benchmark reconstruction module is used to collect current operating parameters and select the corresponding pump consumption curve coefficients based on the current combined pump mode when the system meets stability conditions, thereby establishing a new optimization benchmark. This module stores the pump consumption curve coefficient sets corresponding to different combined pump operating modes.

[0094] The frequency optimization module is used to output frequency adjustment commands based on the power change of the computer group side, the power consumption change of the circulating water pump, and the net revenue, according to whether the net revenue meets the preset economic conditions.

[0095] The system is based on the coordinated operation of a data acquisition module, a status recognition module, a switching detection module, a benchmark clearing module, a stability judgment module, a benchmark reconstruction module, and a frequency optimization module. It realizes automatic reconstruction control of the frequency optimization benchmark of the circulating water pump, avoids interference caused by the start-up or shutdown of the dual-speed power frequency circulating water pump or changes in gear status on the frequency optimization of the variable frequency pump, and improves the rationality of the frequency optimization judgment and the stability of system operation.

[0096] Example This embodiment applies to a 350MW thermal power unit. This 350MW thermal power unit is equipped with a circulating water pump system, including one variable frequency circulating water pump A and one dual-speed fixed frequency circulating water pump B. Variable frequency pump A has a frequency range of 3-24.75Hz and a rated power of approximately 1700kW. Fixed frequency pump B uses a dual-speed motor and has two operating modes: high-speed mode (approximately 1700kW) and low-speed mode (approximately 1080kW).

[0097] This embodiment uses historical operating data of the circulating water pump of a coal-fired power unit and the commissioning record of the integrated speed controller for illustration. The historical operating data includes parameters such as unit load, condenser vacuum, main steam flow rate, main steam temperature, main steam pressure, frequency pump current, high-speed current, and low-speed current, used to determine typical operating conditions of the circulating water system, identification conditions for the operating status of the dual-speed frequency circulating water pump, and offline playback conditions. The commissioning record of the integrated speed controller is used to illustrate the current changes of the variable frequency circulating water pump at different frequencies.

[0098] In this embodiment, the shutdown current threshold of the dual-speed power frequency circulating water pump can be set to 20A, the low-speed operating current range can be set to 100-170A, and the high-speed operating current range can be set to 190-230A; the stabilization waiting time can be set to 60s, the tolerance between the actual frequency feedback and the frequency command of the variable frequency circulating water pump can be set to 0.5Hz, the unit load fluctuation threshold can be set to 10MW, and the condenser back pressure fluctuation threshold can be set to 0.5kPa. The above parameters are only one setting method in this embodiment and can be adjusted according to different unit capacities, equipment characteristics, and on-site operating requirements.

[0099] First, the system identifies the operating status of the dual-speed frequency circulating water pump based on the low-speed and high-speed current of the pump. For example... Figure 2As shown, when the low-speed gear current is within the preset low-speed gear operating current range and the high-speed gear current is less than the preset shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in low-speed gear operation mode; when the high-speed gear current is within the preset high-speed gear operating current range and the low-speed gear current is less than the preset shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in high-speed gear operation mode; when both the low-speed gear current and the high-speed gear current are less than the preset shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in shutdown mode; when neither the low-speed gear current nor the high-speed gear current meets the above conditions, the dual-speed frequency circulating water pump is determined to be in gear switching or in an uncertain state.

[0100] The commissioning records show that the motor current decreases relative to the high-speed operating current of the B circulating water pump at different frequencies of the speed control unit. For example, when the speed control unit frequencies are 24.2Hz, 22.219Hz, and 19.832Hz, the corresponding motor currents are 173A, 147.5A, and 118.21A, respectively. Compared to the high-speed operating current of the B circulating water pump (204.9A), the corresponding current decreases are 15.57%, 28.01%, and 42.31%, respectively. These commissioning records demonstrate that the variable frequency circulating water pump possesses the engineering foundation to reduce current and pump consumption through frequency adjustment.

[0101] Table 1. Comparison of current at different frequencies for the speed control unit

[0102] Example of program logic implementation To illustrate the engineering implementation of this invention, this embodiment uses Python to provide the core program logic, which mainly includes parameter initialization, dual-speed power frequency circulating water pump status identification, mode change detection, old baseline clearing, stability judgment, new baseline establishment, and net profit calculation. Other implementation methods can also be implemented using PLC programs, DCS configuration logic, or other equivalent control programs.

[0103] Step 1: System Initialization and Parameter Configuration During the program initialization phase, the current identification thresholds for the low-speed, high-speed, and shutdown states of the dual-speed power frequency circulating water pump are set. The upper and lower limits of the variable frequency circulating water pump frequency, the frequency trial step size, and system stability judgment parameters are also set. Simultaneously, the optimization direction flag, benchmark validity flag, benchmark reconstruction flag, output validity flag, and revenue calculation variables are initialized. The program is as follows:

[0104]

[0105] In the above program, value represents the current optimization direction, where 1 represents the frequency increase direction, -1 represents the frequency decrease direction, and 0 represents that there is no valid optimization direction at present; j represents whether there is a valid optimization benchmark at present, where 0 represents that a valid benchmark has not yet been established, and 1 represents that a new benchmark has been established under the current combined pump operation mode.

[0106] `rebuild_required` indicates whether the benchmark needs to be rebuilt, and `output_valid` indicates whether the current frequency adjustment command or frequency recommendation value is valid. When the combined pump operating mode changes, the program sets `rebuild_required` to `True` and `output_valid` to `False`, causing the system to enter a benchmark rebuild and output freeze state.

[0107] Different pump combination operation modes are configured with corresponding pump consumption curve coefficients. Among them, mode 0 corresponds to the independent operation of the frequency converter circulating water pump, mode 1 corresponds to the combined operation of the frequency converter circulating water pump and the dual-speed power frequency circulating water pump at low speed, and mode 2 corresponds to the combined operation of the frequency converter circulating water pump and the dual-speed power frequency circulating water pump at high speed.

[0108] Step 2: Identification of the operating status of the dual-speed industrial frequency circulating water pump The system reads the high-speed and low-speed currents of the dual-speed industrial frequency circulating water pump in real time and determines the current operating status based on the current range. The program is as follows:

[0109] In the above procedure, when both the high-speed and low-speed currents are less than the shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in a shutdown state; when the low-speed current is within the preset low-speed operating current range and the high-speed current is lower than the shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in a low-speed operating state; when the high-speed current is within the preset high-speed operating current range and the low-speed current is lower than the shutdown current threshold, the dual-speed frequency circulating water pump is determined to be in a high-speed operating state.

[0110] When two current measuring points are missing, the data is empty, the data format is abnormal, or neither current measurement point meets the above-mentioned shutdown, low-speed operation, and high-speed operation conditions, the program returns a status value of 3.0, indicating that the dual-speed power frequency circulating water pump is in the process of shifting gears, the measuring point is abnormal, or the status is uncertain. During the period when the status value is 3.0, the system suspends the output of benefit evaluation and frequency adjustment commands, and does not establish a new optimization benchmark.

[0111] Step 3: State Change Judgment and Baseline Reconstruction Trigger The system compares the operating status of the dual-speed, frequency-controlled circulating water pump identified in the current sampling period with the operating status recorded in the previous sampling period. If the two are inconsistent, it determines that the dual-speed, frequency-controlled circulating water pump has stopped, is in low-speed mode, high-speed mode, or is in an uncertain state, and immediately triggers the optimization benchmark reconstruction. The procedure is as follows:

[0112]

[0113] When the program starts for the first time, it records the current state of the dual-speed, frequency-controlled circulating water pump and enters a stabilization and initial baseline establishment phase, without immediately performing a benefit evaluation. When the operating state changes, the program calls the optimization state reset function to clear the optimization baseline and benefit calculation results before the switch, and records the time of the most recent state change. Subsequent stabilization waiting time is calculated from this time. For example, when the dual-speed, frequency-controlled circulating water pump switches from low speed to high speed, the state may sequentially go through: 1.0-3.0-2.0. The program re-records the change time each time the state changes, so the stabilization waiting time is recalculated after finally entering the high-speed operating state, avoiding the premature establishment of a new baseline before the gear switch is completed. This approach ensures that the stabilization waiting time is calculated from the last state change, avoiding the premature establishment of a new optimization baseline before the gear switch is completed.

[0114] Step 4: Clear old optimization benchmarks and reset frequency optimization status To prevent the frequency records, back pressure references, load references, optimization direction, and revenue calculation results from the previous combined pump operating mode from continuing to affect the judgment in the current mode, the system calls the frequency optimization state reset function to centrally clear the original optimization state. The program is as follows:

[0115] In the above program, base_freq, base_pressure, and base_load represent the reference frequency, reference back pressure, and reference load, respectively; current_stable_mode represents the stable combined pump operation mode corresponding to the establishment of the current effective optimization reference; and current_pump_coefficients represents the pump consumption curve coefficients corresponding to the current combined pump operation mode.

[0116] When the operating status of the dual-speed power frequency circulating water pump changes, the program clears all the aforementioned variables, historical caches, and revenue calculation results, and sets `output_valid` to `False`. During this period, the system can continue to collect operating data, but it will not adjust the revenue based on the old benchmark frequency, nor will it output new valid frequency adjustment commands.

[0117] Step 5: System stability and establishment of new optimization benchmarks After clearing the old optimization benchmark, the system continues to determine whether the current operating conditions meet the conditions for establishing a new benchmark. Stability conditions include stable combined pump operation mode, stable variable frequency circulating water pump frequency, stable unit load, and stable condenser back pressure. The procedure is as follows:

[0118]

[0119]

[0120] In the above procedure, the combined pump operating mode must remain unchanged within the preset stable waiting time after the most recent state change; the difference between the actual frequency feedback and the frequency command of the variable frequency circulating water pump must be less than the preset frequency tolerance; the unit load and condenser back pressure are judged by the sliding window statistical method, and the load and back pressure are determined to be stable only when the difference between the maximum and minimum values ​​in the sliding window is less than the preset load fluctuation threshold and back pressure fluctuation threshold, respectively.

[0121] Once the system meets the above four stability conditions, the program establishes a new optimization benchmark under the current combined pump operating mode. The program is as follows:

[0122]

[0123]

[0124] In the above program, when j=0 and the system meets all stability conditions, the program saves the average unit load current_avg_load within the current stability window as the new base load base_load, the average condenser back pressure avg_pressure as the new base back pressure base_pressure, and the average variable frequency circulating water pump actual frequency avg_freq as the new base frequency base_freq.

[0125] The program selects the corresponding pump consumption curve coefficient based on the current combined pump operating mode. When the dual-speed, fixed-frequency circulating water pump stops, the pump consumption curve coefficient corresponding to mode 0 is used; when the dual-speed, fixed-frequency circulating water pump is running at low speed, the pump consumption curve coefficient corresponding to mode 1 is used; when the dual-speed, fixed-frequency circulating water pump is running at high speed, the pump consumption curve coefficient corresponding to mode 2 is used. When the state value is 3.0, no pump consumption curve is selected, and no new optimization benchmark is established.

[0126] When j is set from 0 to 1, it indicates that a new optimization benchmark has been established under the current combined pump operating mode. Subsequently, the program uses the new benchmark frequency as the starting point and performs the first frequency trial according to the preset frequency step size.

[0127] Step 6: Calculate net income based on the new optimization benchmark After the new optimization benchmark is established, the system calculates the change in power consumption of the circulating water pump based on the change in the current condenser back pressure relative to the benchmark back pressure, and calculates the change in power consumption of the circulating water pump based on the change in the current frequency of the variable frequency circulating water pump relative to the benchmark frequency, and further calculates the net benefit.

[0128] In this embodiment, the power consumption of the circulating water pump is represented by a cubic polynomial: Np = h0+ h1·f + h2·f² + h3·f 3

[0129]

[0130]

[0131] In the above procedure, Delta_Nd represents the change in unit-side power, Delta_Np represents the change in circulating water pump power consumption, and net_gain represents net profit. Wherein:

[0132] When the frequency of the variable frequency circulating water pump is increased, the change in power consumption of the circulating water pump is usually positive; when the frequency of the variable frequency circulating water pump is decreased, the change in power consumption of the circulating water pump is usually negative. Regardless of whether the frequency is increased or decreased, the overall net benefit is calculated by subtracting the change in power consumption of the circulating water pump from the change in power consumption of the unit.

[0133] When the net benefit is greater than the preset economic dead zone, the condenser back pressure is within the preset effective range, and the condenser back pressure is less than the back pressure high limit protection value, the program continues to adjust the frequency along the current optimization direction; when any of the above conditions are not met, the program reverts to the previous effective frequency and executes frequency holding, locking the current frequency, or ending the current frequency trial according to the control requirements.

[0134] As can be seen from the above program logic, this embodiment does not continue to use the optimization benchmark under the previous stable operating condition after detecting a change in the operating status of the dual-speed power frequency circulating water pump or the operating mode of the combined pump. Instead, it immediately clears the old benchmark data, historical data cache and benefit calculation results, resets the frequency optimization direction and trial state, and freezes the frequency adjustment command output.

[0135] Once the operating status of the dual-speed power frequency circulating water pump has not changed again within the preset stable waiting time, and the actual frequency feedback of the variable frequency circulating water pump, the unit load, and the condenser back pressure all meet the stable conditions, the system establishes a new optimization benchmark under the current combined pump operating mode and selects the pump consumption curve coefficient corresponding to the current combined pump operating mode.

[0136] After the new benchmark is established, the system recalculates the power changes on the computer group side, the power consumption changes of the circulating water pump, and the net revenue. Based on the net revenue and back pressure protection conditions, it generates the next frequency adjustment command or frequency suggestion value, thereby avoiding the misjudgment of back pressure changes and pump consumption changes caused by the start-up and shutdown of the dual-speed power frequency circulating water pump or the switching between high and low speeds as the effect of frequency adjustment of the variable frequency circulating water pump. Therefore, this embodiment achieves automatic reconstruction of the frequency optimization benchmark of the variable frequency circulating water pump under the condition of changing operating status of the dual-speed power frequency circulating water pump through combined pump mode recognition, state change detection, old optimization benchmark clearing, revenue evaluation freezing, system stability judgment, establishment of a new optimization benchmark, and re-evaluation of revenue based on the new benchmark.

[0137] In an exemplary offline playback process built upon historical operational data, the system follows... Figure 1 The process is as shown. When the operating status of the dual-speed, fixed-frequency circulating water pump or the combined pump operating mode changes, the system enters a baseline freeze and stabilization waiting phase, suspending the use of data from this phase to evaluate the benefits of frequency adjustment of the variable-frequency circulating water pump. Once the operating status of the dual-speed, fixed-frequency circulating water pump has not changed again within the preset stabilization waiting time, and the actual frequency feedback of the variable-frequency circulating water pump, the actual load of the unit, and the condenser back pressure all meet the stabilization conditions, the system establishes a new frequency optimization baseline and recalculates the unit-side power change, circulating water pump power consumption change, and net benefit based on the pump consumption relationship corresponding to the current combined pump operating mode.

[0138] As can be seen from Table 1 and the above offline playback process, the current of the speed control unit decreases at different frequencies, indicating that the variable frequency circulating water pump has a basic frequency regulation capability. At the same time, when the dual-speed power frequency circulating water pump starts or stops or changes its gear status, this invention can avoid mistaking the changes in back pressure and pump consumption caused by the changes in the status of the dual-speed power frequency circulating water pump as the result of frequency adjustment of the variable frequency circulating water pump by clearing the old optimization benchmark, pausing the benefit evaluation, and rebuilding the new benchmark after stabilization. This reduces the distortion of benefit evaluation caused by the failure of the old benchmark.

[0139] In summary, this invention, through steps such as combined pump pattern recognition, state change detection, old benchmark clearing, benefit evaluation freezing, stability condition judgment, and new benchmark establishment, forms a frequency optimization benchmark reconstruction method for variable frequency circulating water pumps applicable to scenarios involving changes in the operating state of dual-speed power frequency circulating water pumps. This method helps improve the rationality of frequency benefit judgment and the stability of the frequency optimization process under different combined pump operating modes.

[0140] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for reconstructing the optimization benchmark of a variable frequency pump during circulating water pump switching in a coal-fired power unit, characterized in that, Includes the following steps: Step S1: Collect real-time operating data of the circulating water system. The operating data includes at least the actual frequency feedback of the variable frequency circulating water pump, the low-speed current of the dual-speed power frequency circulating water pump, the high-speed current of the dual-speed power frequency circulating water pump, the actual load of the unit, and the condenser back pressure. Step S2: Identify the operating status of the dual-speed industrial frequency circulating water pump based on the low-speed current and high-speed current of the dual-speed industrial frequency circulating water pump. The operating status includes shutdown status, low-speed operation status, high-speed operation status, and switching status or status uncertainty. Step S3: Determine the combined pump operating mode based on the operating status of the variable frequency circulating water pump and the dual-speed fixed frequency circulating water pump, and determine whether the current combined pump operating mode has changed compared to the combined pump operating mode under the previous stable operating condition. Step S4: When a change in the operating status of the dual-speed power frequency circulating water pump or the operating mode of the combined pump is detected, the optimization benchmark data of the previous stable operating condition is cleared, and the benefit evaluation of the frequency adjustment action of the variable frequency circulating water pump is stopped within the preset stable waiting time. Step S5: When the dual-speed power frequency circulating water pump operates stably, the actual frequency feedback of the variable frequency circulating water pump meets the preset frequency stability condition, the actual load of the unit meets the preset load stability condition, and the condenser back pressure meets the preset back pressure stability condition, a new frequency optimization benchmark is established under the current operating condition. Step S6: Based on the new frequency optimization benchmark, calculate the change in unit-side power, the change in power consumption of the circulating water pump, and the net benefit before and after the frequency adjustment of the variable frequency circulating water pump, and output the frequency adjustment command or frequency suggestion value of the variable frequency circulating water pump according to the net benefit.

2. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 1, characterized in that, In step S2, identifying the operating status of the dual-speed power frequency circulating water pump specifically includes: When the low-speed current of the dual-speed industrial frequency circulating water pump is within the preset low-speed operating current range and the high-speed current is less than the preset shutdown current threshold, the dual-speed industrial frequency circulating water pump is determined to be in low-speed operation mode. When the high-speed current of the dual-speed industrial frequency circulating water pump is within the preset high-speed operating current range and the low-speed current is less than the preset shutdown current threshold, the dual-speed industrial frequency circulating water pump is determined to be in high-speed operation mode. When both the low-speed current and the high-speed current are less than the preset shutdown current threshold, the dual-speed industrial frequency circulating water pump is determined to be in a shutdown state. When neither the low-speed current nor the high-speed current meets the above criteria, the dual-speed industrial frequency circulating water pump is determined to be in gear switching or in an uncertain state.

3. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 1, characterized in that, In step S3, determining the operating mode of the combined pump specifically includes: When the dual-speed industrial frequency circulating water pump is in a stopped state, the combined pump operation mode is determined to be mode 0. When the dual-speed industrial frequency circulating water pump is in low-speed operation, the combined pump operation mode is determined to be mode 1. When the dual-speed industrial frequency circulating water pump is in high-speed operation, the combined pump operation mode is determined to be mode 2. When the dual-speed industrial frequency circulating water pump is in the process of gear switching or in an uncertain state, the combined pump operation mode is determined to be mode 3, and the benefit evaluation is suspended, and no new optimization benchmark is established.

4. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 1, characterized in that, In step S4, clearing the optimization baseline data of the previous stable operating condition specifically includes: Clear the reference frequency, reference back pressure, and reference load of the previous stable operating condition; Remove the calculated changes in unit-side power, changes in circulating water pump power consumption, and net revenue; Reset the optimization direction flag and reset the trial status flag; Clear historical data cache; Record the moment of mode switching and set the benchmark reconstruction flag to true to pause the output of profit evaluation and frequency adjustment instructions based on the old benchmark.

5. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 1, characterized in that, In step S5, determining whether the system meets the stability condition specifically includes: Determine whether the combined pump's operating mode remains unchanged within a preset stable waiting time; Determine whether the difference between the actual frequency feedback and the frequency command of the variable frequency pump is less than the preset frequency tolerance; The sliding window statistical method is used to judge the unit load fluctuation. When the difference between the maximum and minimum unit load within the preset time window is less than the preset load threshold, the load is judged to be stable. The sliding window statistical method is used to judge the condenser back pressure fluctuation. When the difference between the maximum and minimum values ​​of the condenser back pressure within the preset time window is less than the preset back pressure threshold, the back pressure is determined to be stable. Based on a comprehensive assessment of all stability conditions, the system is considered to be stable only when all four conditions—combined pump mode stability, frequency stability, load stability, and back pressure stability—are met simultaneously.

6. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 5, characterized in that, The preset stabilization waiting time is 30-300 seconds; the preset frequency tolerance is 0.3-1.0 Hz; the preset load threshold is 5-20 MW; and the preset back pressure threshold is 0.2-1.0 kPa.

7. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 1, characterized in that, In step S5, establishing a new frequency optimization benchmark specifically includes: Collect the current frequency of the variable frequency pump as the new reference frequency; Collect the current condenser back pressure as the new reference back pressure; Collect the current unit load as the new baseline load; Select the corresponding pump consumption curve coefficient based on the current combined pump operating mode; Zeroing out changes in unit power, changes in circulating water pump power consumption, and net revenue; Clear the baseline reconstruction flag and restore the frequency optimization logic.

8. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 7, characterized in that, The pump consumption curve coefficients vary depending on the operating mode of the combined pump, and different operating modes of the combined pump correspond to different sets of pump consumption curve coefficients; the pump consumption relationship adopts a polynomial form, piecewise fitting, tabular interpolation, or a pump consumption model established from historical operating data.

9. The method for reconstructing the optimization benchmark of the variable frequency pump during the switching of circulating water pumps in a coal-fired unit according to claim 1, characterized in that, In step S6, calculating the net benefit and outputting the frequency adjustment instruction or suggested value specifically includes: Based on the changes in current back pressure and new benchmark back pressure, the change in power on the computer side is calculated through back pressure power correction relationship, unit characteristic curve, radial basis function interpolation model or historical operation data statistical model; Based on the changes in the current frequency and the new reference frequency, and combined with the pump consumption curve coefficient corresponding to the current combined pump mode, the change in power consumption of the circulating water pump is calculated. Net benefit is calculated as the difference between the change in unit power and the change in power consumption of circulating water pumps. Determine whether the net income meets the preset economic conditions. The preset economic conditions include that the net income is greater than the preset economic dead zone, the condenser back pressure is within the preset effective range of back pressure, and the condenser back pressure is less than the preset back pressure high limit protection value. When the net income meets the preset economic conditions, continue to adjust the frequency along the current optimization direction; when the net income does not meet the preset economic conditions, execute the frequency rollback, maintain the frequency, or lock the current frequency.

10. A system for reconstructing the optimization benchmark of a variable frequency pump during circulating water pump switching in a coal-fired power unit, characterized in that, The reconstruction system is used to implement the reconstruction method according to any one of claims 1 to 9, and the reconstruction system comprises: The data acquisition module is used to collect real-time feedback of the actual frequency of the variable frequency circulating water pump, the low-speed current of the dual-speed power frequency circulating water pump, the high-speed current of the dual-speed power frequency circulating water pump, the actual load of the unit, and the condenser back pressure. The status recognition module is used to identify the operating status of the dual-speed power frequency circulating water pump based on the low-speed and high-speed current of the dual-speed power frequency circulating water pump, and to determine the combined pump operating mode based on the operating status of the variable frequency circulating water pump and the dual-speed power frequency circulating water pump. The switching detection module is used to compare the current combined pump operating mode with the combined pump operating mode recorded in the previous sampling period to detect whether a mode switch has occurred. The baseline clearing module is used to clear the optimization baseline data of the previous stable operating condition and set the baseline reconstruction flag when a change in the operating status of the dual-speed power frequency circulating water pump or a change in the operating mode of the combined pump is detected. The stability determination module is used to determine whether the system meets the stability conditions; The benchmark reconstruction module is used to collect current operating parameters and select the corresponding pump consumption curve coefficient according to the current combined pump operating mode when the system meets the stability conditions, and establish a new optimization benchmark. The frequency optimization module is used to output frequency adjustment commands or frequency recommendations based on the power change of the computer group side, the power consumption change of the circulating water pump, and the net benefit, according to whether the net benefit meets the preset economic conditions.

Images