A variable load back pressure adjustment method and system for a direct air-cooled unit

Abstract

The application provides a direct air-cooled unit variable load back pressure adjustment method and system, and belongs to the technical field of cold end control of thermal power generating units. The method aims at the mutual superposition of back pressure changes caused by load changes in the unit variable load process and back pressure responses generated by air-cooled fan adjustment, and the problem that the adjustment benefit judgment is inaccurate due to the mismatch between regional response time and available evaluation time. According to the unit load change information, the back pressure background response and the remaining evaluation time when the fan operation state remains unchanged are determined, and the to-be-adjusted air-cooled region and fan adjustment action are determined according to the regional response time of the candidate air-cooled region. The incremental back pressure response is determined according to the actual condenser back pressure and the back pressure background response, the adjustment benefit is determined by combining the incremental output of the steam turbine and the active power change of the fan, and the fan control instruction is output accordingly. The application can improve the accuracy of fan adjustment effect identification and benefit evaluation under variable load conditions, and realize closed-loop adjustment of the back pressure of the air-cooled unit.

Description

Technical Field

[0001] This invention belongs to the field of cold-end control technology for thermal power generating units, specifically relating to a method and system for adjusting back pressure under variable load in direct air-cooled units. Background Technology

[0002] During operation, thermal power generating units require adjustments such as load increases, decreases, and load maintenance based on grid dispatch requirements and system load demands. For thermal power generating units using direct air-cooled systems, turbine exhaust steam exchanges heat with ambient air through a direct air-cooled condenser. Air-cooled fans drive airflow through the heat exchange tube bundle to maintain the condenser's heat exchange capacity. Condenser back pressure is a crucial parameter affecting the turbine's operational economy. Reducing condenser back pressure can improve the turbine's work capacity under certain conditions, but it typically requires increasing the operating frequency, speed, or number of air-cooled fans, thus increasing plant power consumption. Therefore, during the operation of direct air-cooled units, it is necessary to comprehensively consider changes in turbine output and air-cooled fan power consumption to ensure that the condenser back pressure adapts to the current unit load and environmental conditions.

[0003] The operating status of a direct air-cooled condenser is influenced by a variety of factors, including unit load, turbine exhaust steam volume, ambient temperature, ambient wind, air conditions at the condenser inlet and outlet, and the operating status of the air-cooled fans. When the unit load changes, the turbine exhaust heat load changes accordingly, resulting in a corresponding dynamic change in the condenser back pressure. Simultaneously, altering the operating status of the air-cooled fans can change the airflow and heat exchange capacity through the condenser, thereby regulating the condenser back pressure. Since there is a trade-off between the turbine output gain gained from reducing back pressure and the increased power consumption of the air-cooled fans, existing direct air-cooled units typically determine the economical operating back pressure based on operating parameters such as unit load, environmental conditions, and condenser back pressure, using test curves, historical operating data, or online adjustments. Back pressure regulation is then achieved by changing the air-cooled fan frequency, speed, or the operating status of the air-cooling unit. Some operation control methods also divide the air-cooled fans into different zones. By changing the operating status of the fans in the corresponding zones in turn and observing the changes in condenser back pressure, the changes in turbine output and fan power consumption before and after the fan adjustment are compared to evaluate whether the corresponding adjustment is conducive to the economic operation of the unit.

[0004] However, during unit load increases or decreases, changes in condenser back pressure are not solely caused by air-cooled fan adjustments. Changes in turbine exhaust steam volume and exhaust heat load due to unit load variations can themselves alter condenser back pressure, and air-cooled fan adjustments simultaneously affect this back pressure. If the difference in condenser back pressure before and after fan adjustments is directly used to evaluate the fan adjustment effect, the back pressure change caused by unit load variations is easily included in the back pressure response generated by fan adjustments. This makes it difficult to accurately identify the actual incremental effect of fan adjustments, thus affecting the assessment of turbine incremental output and the economic viability of adjustments. Some existing control methods, to mitigate these effects, require waiting for the unit to reach a relatively stable state before adjusting fans and evaluating benefits. However, this approach contradicts the actual operating conditions of thermal power units frequently participating in Automatic Generation Control (AGC) regulation and continuous load changes, and may not be able to complete back pressure adjustments in a timely manner during continuous load changes.

[0005] Furthermore, direct air-cooled systems possess a certain thermal inertia and dynamic response process. The time required for different air-cooled zones to form a response suitable for back pressure adjustment evaluation after changes in fan operating status may vary. When adjustments are made using fixed time intervals, fixed time periods, or according to a predetermined zone sequence, if the available time for back pressure adjustment is insufficient to cover the response process of the corresponding air-cooled zone, a benefit assessment may be conducted before the back pressure response has fully formed. Additionally, if new load commands arrive during the evaluation process, the unit operating baseline before and after the evaluation may change, thereby reducing the reliability of the adjustment results.

[0006] Therefore, the existing back pressure adjustment technology for direct air-cooled units still needs to address the difficulty in distinguishing between the back pressure background changes caused by load changes and the incremental back pressure response caused by the adjustment of the air-cooled fan during load changes, as well as the mismatch between the dynamic response time of the air-cooled area and the actual available adjustment time, in order to improve the accuracy and feasibility of back pressure adjustment results under load changes. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems existing in the prior art, and to provide a method and system for adjusting the back pressure of a direct air-cooled unit under variable load.

[0008] This invention provides a method for adjusting the back pressure of a direct air-cooled unit under varying load, comprising the following steps: S1. Obtain unit load change information, condenser back pressure and fan operating status of each air-cooled area. Based on the unit load change information, take the condenser back pressure as the starting reference, determine the back pressure background response corresponding to the current load change when the fan operating status remains unchanged, and determine the remaining evaluation time for fan adjustment and response evaluation during the current load change process. S2, obtain the regional response time required for each candidate air-cooled region to form a back pressure response for benefit evaluation from the implementation of fan adjustment; determine the air-cooled region to be adjusted and the corresponding fan adjustment action from the candidate air-cooled regions whose regional response time is not greater than the remaining evaluation time, based on the fan operation status of each candidate air-cooled region. S3, implement the fan adjustment action in the air-cooled area to be adjusted, obtain the actual condenser back pressure and fan active power during the evaluation period covering the response time of the area, and determine the incremental back pressure response generated by the fan adjustment action based on the actual condenser back pressure and the back pressure background response at the corresponding time. S4. Determine the incremental output of the steam turbine based on the incremental back pressure response and the unit load change information; determine the change in the active power of the fan based on the change in the active power of the fan before and after implementing the fan adjustment action; determine the adjustment benefit based on the incremental output of the steam turbine and the change in the active power of the fan; determine the fan operating status of the air-cooled area to be adjusted based on the adjustment benefit; and output the corresponding control command to the fan drive device or air-cooled unit control device of the air-cooled area to be adjusted.

[0009] Furthermore, the unit load change information includes load commands, actual unit load, and operating parameters characterizing the turbine exhaust heat load; the back pressure background response is determined based on a pre-established correspondence between unit load changes and condenser back pressure dynamic response.

[0010] Specifically, the regional response time is determined based on the historical fan adjustment response data or test response data of the corresponding air-cooled region.

[0011] Specifically, the fan adjustment action includes changing the fan frequency, speed, or power setting value of the air-cooled area to be adjusted within the allowable adjustment range of the fan and the allowable back pressure of the condenser.

[0012] Preferably, when the adjustment benefit is greater than a preset benefit threshold, the fan operating state of the air-cooled area to be adjusted after the fan adjustment action is maintained; when the adjustment benefit is not greater than the preset benefit threshold, the air-cooled area to be adjusted is restored to the fan operating state before the fan adjustment action is performed.

[0013] Specifically, after the air-cooled area to be adjusted is restored to the operating state of the fan before the fan adjustment action is implemented, the subsequent air-cooled areas to be adjusted are determined from the candidate air-cooled areas where the benefit evaluation has not been completed and the response time of the area is not greater than the remaining evaluation time; when the load command is updated, the current benefit evaluation is terminated, and the back pressure background response and the remaining evaluation time are re-determined according to the updated load command.

[0014] Furthermore, during the evaluation period, the incremental output of the steam turbine is integrated over time to obtain the incremental output energy of the steam turbine, and the change in the active power of the wind turbine is integrated over time to obtain the incremental energy consumption of the wind turbine. The difference between the incremental output energy of the steam turbine and the incremental energy consumption of the wind turbine is used as the adjustment benefit.

[0015] Another aspect of the present invention provides a variable load back pressure adjustment system for a direct air-cooled unit, comprising: The status acquisition module is used to acquire information on unit load changes, condenser back pressure, fan operating status in each air-cooled zone, and the remaining evaluation time allowed for back pressure adjustment under the current load command. The background response determination module is connected to the state acquisition module and is used to determine the back pressure background response corresponding to the current load change when the fan operating state remains unchanged, based on the unit load change information and the condenser back pressure. The region determination module, connected to the status acquisition module, is used to determine the air-cooled region to be adjusted and the fan adjustment action for the air-cooled region to be adjusted based on the region response time of each candidate air-cooled region and the remaining evaluation time. A back pressure adjustment execution module, connected to the area determination module, and with its control output connected to the fan drive device or air-cooling unit control device of each air-cooled area, is used to execute the fan adjustment action; and The response evaluation module is connected to the status acquisition module, the background response determination module, and the back pressure adjustment execution module, respectively. It is used to determine the incremental back pressure response based on the actual condenser back pressure after the implementation of the fan adjustment action and the back pressure background response at the corresponding time, and to determine the adjustment benefit based on the incremental back pressure response, the unit load change information, and the fan active power before and after the implementation of the fan adjustment action, and to send the adjustment benefit to the back pressure adjustment execution module. The back pressure adjustment execution module is also used to determine the fan operating status of the air-cooled area to be adjusted based on the adjustment benefit, and output control commands to the corresponding fan drive device or air-cooled unit control device.

[0016] Furthermore, the status acquisition module is connected to the unit control system, the condenser back pressure detection device, and the fan drive device of each air-cooled zone; the active power of the fan is determined by the active power signal of the fan drive device or the corresponding power metering signal.

[0017] Specifically, the system also includes a safety constraint module, which is connected to the status acquisition module and the back pressure adjustment execution module, respectively, and is used to determine safe operating conditions based on condenser back pressure, antifreeze status and fan operating status; the back pressure adjustment execution module outputs a control command to restore the fan operating status of the air-cooled area to be adjusted when the adjustment benefit does not reach the preset benefit condition, and stops executing the fan adjustment action when the safe operating conditions are not met.

[0018] The beneficial effects of this invention are as follows: This invention determines the back pressure background response of the air-cooled fan while maintaining its original operating state during load changes and compares it with the actual condenser back pressure after fan adjustment. This separates the back pressure effects of load changes and fan adjustments, improving the accuracy of fan adjustment effect and economic benefit assessment. Simultaneously, it filters the adjustment area based on the air-cooled zone response time and remaining evaluation time, avoiding adjustments that cannot be effectively evaluated within the limited load change time. By combining the turbine's incremental output and fan active power changes, it determines the adjustment benefits and outputs fan control commands, thereby achieving closed-loop economic adjustment of back pressure during load changes in direct air-cooled units. Attached Figure Description

[0019] Figure 1 The flowchart illustrates the operation control of a variable load back pressure adjustment method for a direct air-cooled unit according to a specific embodiment of the present invention. Figure 2 This is a schematic diagram of the signal and control connections of a variable load back pressure adjustment system for a direct air-cooled unit according to a specific embodiment of the present invention. Figure 3 This is a schematic diagram illustrating the relationship between condenser back pressure and slight increase in turbine output under different unit loads, representing a specific embodiment of the present invention. Detailed Implementation

[0020] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] like Figure 1 As shown in the figure, a method for adjusting the back pressure of a direct air-cooled unit under variable load, provided by a specific embodiment of the present invention, includes the following steps: S1. Obtain unit load change information, condenser back pressure and fan operating status of each air-cooled area. Based on the unit load change information, take the condenser back pressure as the starting reference, determine the back pressure background response corresponding to the current load change when the fan operating status remains unchanged, and determine the remaining evaluation time for fan adjustment and response evaluation during the current load change process. S2, obtain the regional response time required for each candidate air-cooled region to form a back pressure response for benefit evaluation from the implementation of fan adjustment; determine the air-cooled region to be adjusted and the corresponding fan adjustment action from the candidate air-cooled regions whose regional response time is not greater than the remaining evaluation time, based on the fan operation status of each candidate air-cooled region. S3, implement the fan adjustment action in the air-cooled area to be adjusted, obtain the actual condenser back pressure and fan active power during the evaluation period covering the response time of the area, and determine the incremental back pressure response generated by the fan adjustment action based on the actual condenser back pressure and the back pressure background response at the corresponding time. S4. Determine the incremental output of the steam turbine based on the incremental back pressure response and the unit load change information; determine the change in the active power of the fan based on the change in the active power of the fan before and after implementing the fan adjustment action; determine the adjustment benefit based on the incremental output of the steam turbine and the change in the active power of the fan; determine the fan operating status of the air-cooled area to be adjusted based on the adjustment benefit; and output the corresponding control command to the fan drive device or air-cooled unit control device of the air-cooled area to be adjusted.

[0022] In one embodiment, the condenser back pressure refers to the condenser steam side pressure corresponding to the turbine exhaust side. In this invention, the condenser back pressure and condenser pressure are used to characterize the same cold-end operating state. Each air-cooled zone consists of one or more air-cooled units capable of unified fan control. The specific number of air-cooled zones is not limited, nor is the number of air-cooled units contained in each air-cooled zone limited.

[0023] Specifically, the fan operating status is used to represent the cooling capacity control status of the corresponding air-cooled area before the implementation of this fan adjustment, including the fan's running and stopped status, and at least one of the frequency, speed, or power setting status of the fan in the running state. The statement that the fan operating status remains unchanged means that when determining the back pressure background response, the air-cooled side control status before the implementation of this fan adjustment is used as a benchmark, and the changes in cooling capacity caused by the current fan adjustment are not introduced.

[0024] Furthermore, the back pressure background response represents the dynamic change process of condenser back pressure during the current load change, when the air-cooled side maintains the aforementioned baseline operating state, caused by the changes in unit load and exhaust steam heat load related to the unit load change. The back pressure background response is a time-varying back pressure baseline sequence or back pressure change trajectory, rather than a single fixed back pressure value. In subsequent evaluation periods, the actual condenser back pressure at each sampling time is compared with the back pressure background response at the same time to avoid attributing all back pressure changes caused by unit load increases or decreases to fan adjustments.

[0025] Based on the above basic implementation method, the unit load change information includes load command, actual unit load, and operating parameters characterizing the turbine exhaust heat load; the back pressure background response is determined according to the pre-established correspondence between unit load change and condenser back pressure dynamic response.

[0026] Furthermore, the operating parameters characterizing the turbine exhaust heat load are used to reflect the changing trend of the exhaust steam flow rate or exhaust heat load entering the condenser as the unit load changes. These parameters can be the turbine exhaust steam flow rate, the main steam flow rate, or equivalent exhaust heat load parameters determined by existing unit operating parameters. The purpose of using these parameters is to characterize the impact of load changes on the condenser heat load, and it is not necessary to set up a separate exhaust steam flow rate measurement device.

[0027] Furthermore, the correspondence between the unit load change and the dynamic response of the condenser back pressure can be established based on historical unit operating data or pre-conducted variable load test data. Variable load operating data where the air-cooled fan operating status has not undergone active adjustment is selected, and a dynamic correspondence between unit load change and condenser back pressure change is established according to load level, load change direction, and load change degree. During actual operation, the matching dynamic correspondence is invoked based on the current load change information, and the current measured condenser back pressure is used as the starting reference to obtain the back pressure background response corresponding to the current load change process. When establishing or invoking the dynamic correspondence, historical operating data or test data are also matched according to the air-cooled side reference operating status before the current fan adjustment. When the influence of environmental conditions on the condenser back pressure is not negligible, the corresponding dynamic relationship is selected based on the current environmental conditions, or environmental condition compensation is performed on the back pressure background response. The air-cooled side reference operating state is used to maintain the same cooling capacity conditions as the fan being evaluated, except for the fan adjustment in this case. Specifically, the unit load, load change rate, air-cooled side reference operating state, and environmental conditions can be divided into several operating intervals, and the condenser back pressure change sequence over time when the fan state does not change actively can be stored for each operating interval. During actual operation, the corresponding operating interval is selected according to the current operating parameters, and the back pressure change sequence under the current load change conditions is obtained by interpolating the data of adjacent operating intervals. The back pressure background response is formed with the current condenser back pressure as the starting reference. In one implementation, at least one of the air-cooled condenser inlet air temperature, ambient temperature, and ambient wind conditions is used to determine whether the dynamic correspondence is applicable to the current evaluation process. When the change in the environmental condition during the evaluation period does not exceed a preset allowable range, the current back pressure background response continues to be used; when the change in the environmental condition causes the current back pressure background response to no longer represent the baseline back pressure change corresponding to the load change, the current benefit evaluation is terminated. This avoids misinterpreting sudden changes in the environmental condition as incremental back pressure responses caused by fan adjustments.

[0028] Specifically, the remaining evaluation time represents the remaining evaluation time from the current moment, under the current load change state, during which one turbine adjustment, back pressure response acquisition, and revenue evaluation can be completed. The remaining evaluation time is not limited to a fixed load command cycle, nor is it limited to a fixed time period, but is determined based on the effective operating phase corresponding to the current load command or the time range within which the unit control system allows for cold-end economic adjustments.

[0029] Furthermore, when the unit control system can obtain the effective time range of the current load command, the remaining evaluation time is determined based on the time difference between the current time and the end time of the effective time range. When the load command does not have a fixed holding period, an evaluation window that allows back pressure adjustment is pre-set according to the current load change stage, and the remaining evaluation time of the evaluation window is used as the remaining evaluation time. Therefore, this embodiment does not require dividing the power grid dispatching cycle into several equal-length time periods.

[0030] In one specific implementation, the regional response time is determined based on historical fan adjustment response data or test response data of the corresponding air-cooled region.

[0031] In this embodiment, the regional response time refers to the time required from the issuance of a fan adjustment command to the corresponding air-cooled region until the condenser back pressure forms an effective response sufficient to determine the effect of the fan adjustment. The regional response time at least covers the back pressure response delay after the actual change in fan operating status and the sampling process required to form effective evaluation data; it does not require the condenser back pressure to reach a completely static stable state. The effective response refers to a back pressure change, after deducting the back pressure background response, that meets the data validity conditions pre-determined based on back pressure detection accuracy, background response residuals, and natural operational fluctuations, and can be used for adjustment benefit calculation within a continuous sampling period. The evaluation period refers to the time interval from the start of the fan adjustment action or the actual change in fan operating status until the completion of the evaluation of the adjustment benefit. The evaluation period at least covers the regional response time of the corresponding air-cooled region and does not exceed the current remaining evaluation time.

[0032] Furthermore, operating events involving changes in fan frequency, speed, or power in the corresponding air-cooled area can be extracted from the unit's historical database. The time relationship between the fan adjustment time and the formation of an identifiable response in the condenser back pressure can be statistically analyzed to determine the regional response time of the air-cooled area under different operating conditions. Alternatively, under the unit's permissible commissioning conditions, controlled fan adjustments can be implemented in the corresponding air-cooled area, and the regional response time can be determined based on the obtained back pressure response curve.

[0033] Furthermore, the regional response time is allowed to differ for different air-cooled zones, and the regional response time for the same air-cooled zone is also allowed to differ under different unit loads or environmental conditions. During actual operation, the regional response time corresponding to the current operating condition is selected. When the regional response time of a candidate air-cooled zone is greater than the remaining evaluation time, fan adjustments for that candidate air-cooled zone will not be initiated during the current evaluation process to avoid entering the benefit judgment stage before effective evaluation data for the back pressure response has been generated.

[0034] In another specific embodiment, the fan adjustment action includes changing the fan frequency, speed, or power setting value of the air-cooled area to be adjusted within the allowable adjustment range of the fan and the allowable back pressure of the condenser.

[0035] In this embodiment, the fan adjustment action can be a positive adjustment to increase the fan's cooling capacity or a negative adjustment to decrease the fan's cooling capacity. Increasing the fan's frequency, speed, or power setting increases the airflow in the corresponding air-cooled area, typically enhancing the heat exchange capacity of the air-cooled condenser. Decreasing the corresponding setting reduces the fan plant's power consumption, but may simultaneously increase the condenser back pressure. Therefore, this embodiment evaluates both adjustment directions uniformly through subsequent adjustments, rather than pre-setting increasing or decreasing fan power as the sole optimal direction.

[0036] Specifically, the allowable adjustment range of the fan is determined based on the allowable operating range of the fan and its driving equipment, and the allowable back pressure range of the condenser is determined based on the operating requirements of the turbine and condenser. The fan adjustment actions do not require fixed frequency change values, speed change values, or power change values. Under the condition of satisfying the constraints of fan operation and condenser back pressure, the feasible adjustment direction and adjustment amount are determined based on the current fan operating status.

[0037] Furthermore, for air-cooled fans equipped with variable frequency drive devices, the frequency or speed of the fan is adjusted first to achieve continuous changes in cooling capacity; for systems that allow changes in cooling capacity by engaging or disengaging the air-cooling unit, the fan adjustment action can also be implemented by changing the operating state of the air-cooling unit, provided that the corresponding start-up and shutdown conditions and operating constraints are met. In another specific embodiment, after the fan adjustment action is performed, the actual condenser back pressure is collected according to the same time reference as the back pressure background response. Let the actual condenser back pressure at any moment within the evaluation period be the measured back pressure value, and the back pressure background response at the corresponding moment be the background back pressure value. The difference between the two is used to characterize the incremental back pressure response generated by the fan adjustment action under the current variable load background.

[0038] Furthermore, when the actual condenser back pressure is lower than the background back pressure at the corresponding moment, it indicates that the current fan adjustment has a back pressure reduction effect relative to maintaining the original fan operating state; when the actual condenser back pressure is higher than the background back pressure at the corresponding moment, it indicates that the current fan adjustment has a back pressure increase effect relative to the background state. The incremental back pressure response retains directional information for subsequent determination of the turbine's incremental output.

[0039] Specifically, to reduce the impact of the fixed bias of the background response model itself on the incremental back pressure response, an initial bias can be determined based on the deviation between the measured condenser back pressure and the corresponding background back pressure within a certain period before the implementation of the fan adjustment, and this initial bias can be subtracted when determining the incremental back pressure response. This bias handling is a correction measure during the use of the background response and does not change the basic technical relationship of using the difference between the actual condenser back pressure and the back pressure background response to separate the fan adjustment effect.

[0040] Furthermore, the incremental turbine output is not simply determined by the difference in measured active power of the generator before and after the fan adjustment. When the unit participates in load control, the coordinated control system may maintain power generation tracking the load command by changing fuel quantity, steam flow rate, or regulating valve status. Therefore, directly comparing generator power may not fully reflect the change in turbine work capacity caused by reducing or increasing condenser back pressure. This embodiment determines the incremental turbine output corresponding to the current fan adjustment by invoking the corresponding turbine micro-increase output relationship based on the incremental back pressure response and the current unit load.

[0041] In this embodiment, the incremental turbine output relationship can be obtained through incremental output tests under different loads, or it can be established using back pressure and output relationship data provided by the turbine manufacturer. Under different unit loads, the correspondence between condenser back pressure changes and turbine output changes is determined. During actual operation, interpolation or referencing the corresponding relationship is performed based on the current unit load and the incremental back pressure response to obtain the incremental turbine output.

[0042] Furthermore, the active power of the fan is preferably obtained directly from the fan drive device or the corresponding power metering device. When the unit control system does not directly provide the active power of the fan, the input active power of the fan can be determined based on electrical parameters such as fan voltage, current, and power factor. The active power of the fan is used to represent the actual power consumption of the air-cooled fan undertaken by the unit, and the fan shaft power is not a necessary evaluation quantity.

[0043] Specifically, the active power of the fans before and after the adjustment is implemented is statistically analyzed using the same air-cooled area or the same group of fans involved in the adjustment. The difference between the two is used to determine the change in active power. When the fan power is increased, the change can be positive; when the fan power is decreased, the change can be negative. This allows for a unified method to evaluate the benefits of both increasing and decreasing the fan cooling capacity.

[0044] In another specific embodiment, when the adjustment benefit is greater than a preset benefit threshold, the fan operation state of the air-cooled area to be adjusted after the fan adjustment action is maintained; when the adjustment benefit is not greater than the preset benefit threshold, the air-cooled area to be adjusted is restored to the fan operation state before the fan adjustment action is implemented.

[0045] Furthermore, the preset revenue threshold is used to avoid repeated fluctuations in adjustment revenue around zero due to condenser back pressure measurement fluctuations, fan active power measurement errors, and unit operation fluctuations. The preset revenue threshold is determined based on the adjustment revenue evaluation metric used and has the same dimensions as the adjustment revenue; when power revenue is used as the evaluation metric, the preset revenue threshold is a power threshold; when cumulative energy is used as the evaluation metric, the preset revenue threshold is an energy threshold.

[0046] Specifically, maintaining the fan operating state means continuing to use the frequency, speed, and power settings or the air-cooled unit operating state established after the fan adjustment action was performed; restoring the fan operating state to the state before the fan adjustment action was performed means returning the corresponding fan or air-cooled unit to the baseline operating state recorded before the start of this adjustment. This avoids fan adjustments that do not yield effective economic benefits from continuously affecting unit operation.

[0047] In another specific embodiment, after the air-cooled area to be adjusted is restored to the fan operating state before the fan adjustment action is implemented, the subsequent air-cooled areas to be adjusted are determined from the candidate air-cooled areas where the benefit evaluation has not been completed and the response time of the area is not greater than the remaining evaluation time; when the load command is updated, the current benefit evaluation is terminated, and the back pressure background response and the remaining evaluation time are re-determined according to the updated load command.

[0048] Specifically, if the adjustment benefit of an air-cooled zone fails to reach the stated benefit threshold, it only indicates that the adjustment of that air-cooled zone under the current unit operating conditions and wind turbine operating status has not yielded effective benefits, and does not mean that other air-cooled zones lack effective adjustment potential. Therefore, after restoring the current air-cooled zones to be adjusted, other candidate air-cooled zones that have not yet been evaluated are retained, and air-cooled zones that can complete the response evaluation in the current evaluation process are re-selected according to the zone response time and remaining evaluation time.

[0049] Furthermore, air-cooled areas that have already completed benefit evaluation, air-cooled areas that currently lack fan adjustment margin, air-cooled areas with fan malfunctions, and air-cooled areas restricted by safe operating conditions will not be considered as air-cooled areas to be adjusted in the future. Air-cooled areas that have not completed evaluation in the current evaluation process will maintain their original fan operating status and can re-enter the candidate air-cooled area set when the evaluation conditions are met in the future.

[0050] Furthermore, when a new load command arrives, the exhaust heat load change process corresponding to the original load command changes, and the original back pressure background response is no longer used as the evaluation benchmark under the new load change state. Therefore, the determination of adjustment benefits using the response in the current evaluation period is terminated, and the back pressure background response is re-established based on the updated load command and the current measured unit status, while the remaining evaluation time is re-determined. Evaluation data terminated due to load command updates are not considered valid evaluation results for the current air-cooled zone adjustment benefits.

[0051] In another specific embodiment, during the evaluation period, the incremental output of the steam turbine is integrated over time to obtain the incremental output energy of the steam turbine, and the change in the active power of the wind turbine is integrated over time to obtain the incremental energy consumption of the wind turbine. The difference between the incremental output energy of the steam turbine and the incremental energy consumption of the wind turbine is used as the adjustment benefit.

[0052] Furthermore, when using cumulative energy evaluation, the evaluation begins from the start of the fan adjustment action or from the moment the fan's operating state actually changes, and continues until the end of the current evaluation period. The incremental turbine output energy reflects the cumulative turbine work gain generated during the evaluation period by changing the condenser back pressure through fan adjustment, and the incremental fan energy consumption reflects the increase or decrease in fan plant power consumption during the same evaluation period due to the implementation of the fan adjustment action.

[0053] Specifically, since the change in the active power of the air-cooled fan after the change in its operating state usually precedes the establishment of the condenser back pressure and the turbine output response, the aforementioned cumulative energy evaluation can incorporate the power change in the initial stage of fan adjustment and the subsequent gradually formed back pressure response into the same evaluation process, rather than simply comparing the instantaneous power of the two steady-state operating points.

[0054] In this embodiment, when the incremental output energy of the steam turbine is greater than the incremental energy consumption of the wind turbine and exceeds the corresponding revenue threshold, it indicates that the current wind turbine adjustment has generated positive cumulative revenue during the evaluation period; otherwise, it indicates that the adjustment has not generated enough cumulative revenue to maintain the current wind turbine operating state.

[0055] In one specific implementation, such as Figure 2 As shown, a variable load back pressure adjustment system for a direct air-cooled unit is provided, comprising: The status acquisition module is used to acquire information on unit load changes, condenser back pressure, fan operating status in each air-cooled zone, and the remaining evaluation time allowed for back pressure adjustment under the current load command. The background response determination module is connected to the state acquisition module and is used to determine the back pressure background response corresponding to the current load change when the fan operating state remains unchanged, based on the unit load change information and the condenser back pressure. The region determination module, connected to the status acquisition module, is used to determine the air-cooled region to be adjusted and the fan adjustment action for the air-cooled region to be adjusted based on the region response time of each candidate air-cooled region and the remaining evaluation time. A back pressure adjustment execution module, connected to the area determination module, and with its control output connected to the fan drive device or air-cooling unit control device of each air-cooled area, is used to execute the fan adjustment action; and The response evaluation module is connected to the status acquisition module, the background response determination module, and the back pressure adjustment execution module, respectively. It is used to determine the incremental back pressure response based on the actual condenser back pressure after the implementation of the fan adjustment action and the back pressure background response at the corresponding time, and to determine the adjustment benefit based on the incremental back pressure response, the unit load change information, and the fan active power before and after the implementation of the fan adjustment action, and to send the adjustment benefit to the back pressure adjustment execution module. The back pressure adjustment execution module is also used to determine the fan operating status of the air-cooled area to be adjusted based on the adjustment benefit, and output control commands to the corresponding fan drive device or air-cooled unit control device.

[0056] In this embodiment, each module is a functional unit divided according to data processing and control functions. Each module can be integrated into the existing control system of the unit, or it can be partially set in an independent control device. The functional division of each module does not mean that it must be implemented by an independent physical controller, as long as it can complete the corresponding data acquisition, data processing and control output relationships.

[0057] Specifically, the status acquisition module obtains real-time operating data from the unit side and the air-cooled side, and sends the unit load change information and condenser back pressure to the background response determination module, and sends the remaining evaluation time to the area determination module; the area determination module generates the air-cooled area to be adjusted and the fan adjustment action, and then sends it to the back pressure adjustment execution module; the back pressure adjustment execution module outputs control commands to the actual fan drive device or air-cooled unit control device. The changes in condenser back pressure and fan active power caused by the change in fan operating status are obtained by the status acquisition module and evaluated by the response evaluation module. This forms a closed-loop signal chain from operating status acquisition, fan adjustment, physical response acquisition, benefit evaluation to fan control.

[0058] In one specific embodiment, the status acquisition module is connected to the unit control system, the condenser back pressure detection device, and the fan drive device of each air-cooled zone; the active power of the fan is determined by the active power signal of the fan drive device or the corresponding power metering signal.

[0059] Furthermore, the unit control system can be an existing distributed control system of the unit or a control system with corresponding operational data output capabilities, used to provide load commands, actual unit load, and operational data related to changes in unit load. The condenser back pressure detection device is used to provide real-time condenser back pressure, and the fan drive device is used to provide the fan operating status of each air-cooled zone and receive fan control commands output by the back pressure adjustment execution module.

[0060] Furthermore, when the fan drive device is a variable frequency drive device, the back pressure adjustment execution module can output frequency or speed setting commands to the fan drive device; when other drive methods capable of changing the cooling capacity of the air-cooled fan are used, it outputs power or operating status control commands corresponding to that drive method. This invention is not limited to specific controllers, communication protocols, or fan drive device models.

[0061] In one specific implementation, the system further includes a safety constraint module, which is connected to the status acquisition module and the back pressure adjustment execution module respectively. The safety constraint module is used to determine safe operating conditions based on the condenser back pressure, antifreeze status, and fan operating status. When the adjustment benefit does not reach the preset benefit condition, the back pressure adjustment execution module outputs a control command to restore the fan operating status of the air-cooled area to be adjusted, and stops executing the fan adjustment action when the safe operating conditions are not met.

[0062] Specifically, the safety operating conditions take precedence over economic adjustments. When the condenser back pressure reaches the permissible operating boundary of the turbine or condenser, when the air-cooled system has antifreeze constraints, or when the fan to be adjusted reaches the permissible frequency, speed, power, or start / stop state boundary, the current fan adjustment action will no longer be expanded based on economic benefits. When an already issued economic adjustment command conflicts with the safety operating requirements, the control state that satisfies the safety operating requirements will be used as the output state of the back pressure adjustment execution module.

[0063] Furthermore, the anti-freezing status is determined based on the existing anti-freezing control conditions of the air-cooled system, and the fan operating status includes at least the fan fault status and the fan's allowable adjustment range. When using the start-up and shutdown of the air-cooled unit as an adjustment action, the allowable start-up and shutdown conditions and the minimum start-up and shutdown interval of the air-cooled unit can also be included in the safe operating conditions. The specific limits of the safe operating conditions are determined based on the design parameters and operating procedures of the corresponding unit, turbine, air-cooled condenser, and fan equipment, and are not limited to uniform fixed values.

[0064] In one specific implementation, this embodiment uses a direct air-cooled thermal power generating unit as an example to illustrate the variable load back pressure adjustment process of the present invention. The direct air-cooling system of the unit is divided into six air-cooling zones, each equipped with an air-cooled fan capable of independently adjusting its operating status. The unit control system can obtain load commands, actual unit load, condenser back pressure, and the operating status and active power of the fans in each air-cooling zone. A correspondence between unit load changes and condenser back pressure dynamic responses under different load variations is established in advance based on historical unit operating data, and the zone response time of each air-cooling zone is determined based on historical fan adjustment data.

[0065] In this embodiment, the unit's current actual load is 285MW. Upon receiving a load command to increase the load to 300MW, the unit enters the load increase process. At the start of this back pressure adjustment, the measured condenser back pressure is 9.80kPa, and the fans in each air-cooled zone are all in normal operating condition.

[0066] Specifically, the current load command, actual unit load, condenser back pressure, and fan operating status of the six air-cooled zones are obtained. Based on the current load increase process, the dynamic response relationship corresponding to the current operating condition is obtained from the pre-established correspondence between unit load changes and condenser back pressure dynamic response. Using the current measured condenser back pressure of 9.80 kPa as the initial state, the back pressure background response is determined when the fan operating status of each air-cooled zone remains unchanged.

[0067] The back pressure background response is used to represent the change in condenser back pressure caused solely by the current unit load increase, assuming no active fan adjustment is implemented. In this embodiment, based on the dynamic response relationship, the back pressure background responses at 30s, 60s, 90s, and 110s after the start of this evaluation are 9.86kPa, 9.93kPa, 10.00kPa, and 10.05kPa, respectively. This indicates that, while maintaining the current air-cooled fan status, the condenser back pressure tends to gradually increase as the unit load increases.

[0068] Meanwhile, based on the effective adjustment phase corresponding to the current load change process, it is determined that there are still 190 seconds from the current moment that can be used to implement wind turbine adjustments and obtain the corresponding back pressure response. Therefore, 190 seconds is determined as the remaining evaluation time used in this regional screening.

[0069] The response times of the six air-cooled zones are read. In this embodiment, to illustrate the control process of the present invention, the response times of the six air-cooled zones are set to 80s, 110s, 140s, 175s, 210s and 240s respectively.

[0070] Since the remaining evaluation time is 190s, the first four air-cooled regions with response times of 80s, 110s, 140s, and 175s respectively can all form back pressure responses for benefit evaluation within the current remaining evaluation time. The fifth and sixth air-cooled regions with response times of 210s and 240s respectively will not initiate fan disturbances during this adjustment process. When used for candidate region screening, the remaining evaluation time should also meet the safety exit or recovery control margin requirements reserved by the current control system.

[0071] For candidate air-cooled areas that meet the time requirements, their current fan operating status and adjustment margin are further checked. In this embodiment, the fans in the second air-cooled area are in normal operation and have upward adjustment margin, therefore, the second air-cooled area is identified as the air-cooled area to be adjusted. At this time, all fans in the second air-cooled area are operating normally, with a fan frequency of 40Hz and upward adjustment space. Therefore, the fan adjustment action is determined to be to increase the fan frequency of the second air-cooled area from 40Hz to 43Hz. The frequency adjustment amount is within the allowable adjustment range of the fans, and based on the current condenser back pressure status, increasing the cooling capacity of this area will not cause the condenser back pressure to exceed the allowable operating range.

[0072] A frequency adjustment command is output to the fan drive device corresponding to the second air-cooled zone, so that the fan frequency in the second air-cooled zone is increased from 40Hz to 43Hz, and the response evaluation begins when the actual operation status of the fan changes.

[0073] During the 110s evaluation period, the actual condenser back pressure and the active power of the corresponding fans in the second air-cooled area were continuously acquired. Before the fan adjustment, the total active power of the fans in the second air-cooled area involved in this adjustment was 780kW; after increasing the fan frequency, the total active power of the fans stabilized at around 840kW. Therefore, the increase in active power of the fans corresponding to this fan adjustment was approximately 60kW.

[0074] At 30s, 60s, 90s, and 110s after the start of the evaluation, the actual measured condenser back pressures were 9.82kPa, 9.84kPa, 9.86kPa, and 9.87kPa, respectively. Comparison with the back pressure background response determined in S1 at the same time points shows that the actual condenser back pressure decreased by approximately 0.04kPa, 0.09kPa, 0.14kPa, and 0.18kPa, respectively, at each of these times.

[0075] Therefore, this embodiment does not consider the direct change between 9.80 kPa and 9.87 kPa as the effect of the fan adjustment. Although the actual condenser back pressure increased from 9.80 kPa to 9.87 kPa, without the background of this fan adjustment, the condenser back pressure at 110 s would have been expected to have increased to 10.05 kPa. The actual condenser back pressure decreased by 0.18 kPa relative to the background back pressure response, indicating that the fan adjustment in the second air-cooled zone actually offset part of the back pressure increase caused by the increase in exhaust heat load during the load increase process.

[0076] The incremental back pressure response corresponding to this turbine adjustment is obtained from the difference between the actual condenser back pressure and the back pressure background response at the corresponding moment. In this embodiment, the direction of reducing condenser back pressure is taken as the direction that is conducive to increasing turbine output. Therefore, the effective back pressure reduction caused by the turbine adjustment at 110s is 0.18kPa.

[0077] Furthermore, the incremental turbine output corresponding to the incremental back pressure response is determined based on the current unit load and the pre-established turbine micro-output relationship. In this embodiment, within the current load range, according to the corresponding relationship obtained from the unit micro-output test, the equivalent incremental turbine output corresponding to each 1 kPa decrease in condenser back pressure is approximately 0.90 MW.

[0078] Therefore, when the effective back pressure reduction at the end of the evaluation period is 0.18 kPa, the corresponding incremental turbine output is approximately 0.162 MW, or 162 kW. The active power of the second air-cooled area fan increases from 780 kW to 840 kW, a change of 60 kW. When evaluated based on the power state at the end of the evaluation period, the net power gain corresponding to this adjustment is approximately 102 kW, indicating that after increasing the cooling capacity of the second air-cooled area fan, the equivalent incremental output obtained by the turbine side is greater than the increase in plant power consumption by the fan.

[0079] When further evaluating using cumulative net energy, the incremental turbine output gradually formed with the incremental back pressure response during the evaluation period is integrated over time, as is the change in active power of the wind turbine. Since the increase in wind turbine power is formed relatively quickly after the start of the adjustment, while the incremental turbine output is gradually established with the condenser back pressure response, the cumulative net energy evaluation simultaneously includes the increase in plant power consumption in the initial stage of wind turbine adjustment and the subsequent turbine output gains.

[0080] When the difference between the incremental output energy of the steam turbine and the incremental energy consumption of the fan obtained from the evaluation period is greater than the preset benefit threshold, the adjusted 43Hz fan operating state of the second air-cooled zone is taken as the target fan operating state of the current zone, and the back pressure adjustment execution module maintains the corresponding fan frequency setting value.

[0081] Therefore, in this embodiment, when the unit continues to increase load and the condenser back pressure itself has an upward trend, it does not use the two back pressure values ​​before and after the fan adjustment to directly evaluate the fan effect. Instead, it first establishes the back pressure background response when maintaining the original fan operation state, and then compares the actual condenser back pressure with the background back pressure at the same time to separate the incremental back pressure response generated by the fan adjustment in the second air-cooled area. The turbine revenue and fan power consumption corresponding to the incremental response are used to jointly determine whether to maintain the current fan adjustment.

[0082] In another operating scenario, if, after adjusting the fan in a certain air-cooled zone to be adjusted, the incremental turbine output determined by the incremental back pressure response is insufficient to compensate for the increase in the fan's active power, causing the adjustment benefit to be no greater than a preset benefit threshold, then a recovery command is output to the fan drive device of that air-cooled zone, causing the fan to return to the frequency, speed, or power setting state recorded before the start of this adjustment. The evaluation result of no effective benefit in this instance is only used to indicate that this adjustment of the air-cooled zone under the current operating condition is not worth retaining, and does not directly terminate the evaluation of other candidate air-cooled zones.

[0083] After restoring the air-cooled area, candidate air-cooled areas that have not yet completed benefit evaluation are re-screened based on the remaining evaluation time. If the regional response time of another candidate air-cooled area is not greater than the current remaining evaluation time, it will continue to be identified as a subsequent air-cooled area to be adjusted; if the regional response time of all unevaluated air-cooled areas is greater than the remaining evaluation time, no new wind turbine adjustments will be initiated, and the currently confirmed wind turbine operating status will be maintained.

[0084] In the evaluation process of this embodiment, if the power grid dispatch sends a new load command, causing the unit to transition from the original load increase process to a new load change process, the original back pressure background response will no longer be used as the benchmark for benefit evaluation. The control system terminates the currently incomplete benefit evaluation, does not use the data obtained during this evaluation period to determine the current regional adjustment benefit, and re-determines the back pressure background response and remaining evaluation time based on the new load command, the current actual unit load, and the current condenser back pressure. Then, it performs regional screening and back pressure adjustment according to the new operating conditions.

[0085] Furthermore, if during the evaluation process, the condenser back pressure approaches the allowable operating boundary, the air-cooled system's antifreeze conditions are not met, or the fan to be adjusted reaches the allowable operating boundary, the current economic fan adjustment will be stopped, and the air-cooled fan operating status will be maintained or adjusted according to the unit's existing safety control requirements. In this embodiment, the economic back pressure adjustment does not change the original safety protection logic of the turbine and air-cooled system, and the control priority of safe operating conditions is higher than the selection of fan operating status based on adjustment benefits; Figure 3 The turbine output of the steam turbine is slightly increased, with the unit output corresponding to the preset reference back pressure as the zero reference. The relative output decrease caused by the back pressure being higher than the reference back pressure is represented by a negative value. When actually determining the turbine output increase corresponding to the fan adjustment, it is determined based on the output difference or local change relationship corresponding to the corresponding back pressure point before and after the adjustment.

[0086] In summary, this embodiment has at least the following technical effects: Improve the accuracy of identifying the fan adjustment effect during load changes.

[0087] This invention determines the back pressure background response when the air-cooled fan's operating state remains unchanged based on unit load change information, and compares the actual condenser back pressure after fan adjustment with the corresponding back pressure background response to obtain the incremental back pressure response generated by fan adjustment. This reduces the interference of back pressure changes caused by unit load increases or decreases on the judgment of fan adjustment effects, and avoids response aliasing when directly evaluating fan adjustment based on the back pressure difference. This invention selects air-cooled regions to be adjusted based on the regional response time required for each candidate air-cooled region to form a back pressure response that can be used for benefit evaluation, and the remaining evaluation time during the current load change process. This avoids initiating regional adjustments that cannot complete effective response evaluation when there is insufficient remaining evaluation time, and overcomes the problem that fixed time period or fixed region sequence control is difficult to adapt to the dynamic response differences of different regions. This invention uses the incremental back pressure response obtained by separation to determine the incremental output of the steam turbine, and combines the change in the active power of the fan to determine the adjustment benefit. This allows the evaluation results to simultaneously reflect the impact of fan adjustment on the steam turbine's work capacity and the power consumption of the air-cooled fan plant, avoiding the use of the degree of condenser back pressure reduction or the change in fan power consumption as the basis for control. This invention integrates the incremental output of the steam turbine and the change in the active power of the fan during the evaluation period, and evaluates the adjustment benefits based on the difference between the incremental output energy of the steam turbine and the incremental energy consumption of the fan. It can incorporate the time delay between the change in fan power and the response of the condenser back pressure into the same evaluation process, making the benefit judgment more consistent with the dynamic operating characteristics of the direct air-cooled system. This invention determines the fan operating status of the air-cooled area to be adjusted based on the adjustment benefit, and outputs corresponding control commands to the fan drive device or air-cooled unit control device; for adjustments that do not meet the benefit conditions, it can also restore the original fan operating status of the corresponding area and continue to evaluate other candidate areas that meet the conditions, thereby forming a closed-loop control relationship from operating status acquisition, area selection, fan adjustment, response acquisition, benefit evaluation to control execution; This invention does not rely on a fixed number of air-cooled zones, a fixed evaluation duration, a fixed fan adjustment range, or a fixed load command cycle. The response time, fan adjustment method, and evaluation process of each zone can be determined based on the unit's current load and the actual operating status of the air-cooled system. Therefore, it is applicable to units of different capacities, different air-cooled zone layouts, and different variable load operating conditions. Meanwhile, economic adjustments are constrained by condenser back pressure, anti-freezing requirements, and fan operating boundaries, without altering the unit's original safety protection logic.

[0088] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for adjusting the back pressure of a direct air-cooled unit under variable load, characterized in that, Includes the following steps: S1. Obtain unit load change information, condenser back pressure and fan operating status of each air-cooled area. Based on the unit load change information, with the condenser back pressure as the starting reference, determine the back pressure background response corresponding to the current load change under the condition that the fan operating status remains unchanged, and determine the remaining evaluation time for fan adjustment and response evaluation during the current load change process. S2, obtain the regional response time required for each candidate air-cooled region to form a back pressure response for benefit evaluation from the implementation of fan adjustment; determine the air-cooled region to be adjusted and the corresponding fan adjustment action from the candidate air-cooled regions whose regional response time is not greater than the remaining evaluation time, based on the fan operation status of each candidate air-cooled region. S3, implement the fan adjustment action in the air-cooled area to be adjusted, obtain the actual condenser back pressure and fan active power during the evaluation period covering the response time of the area, and determine the incremental back pressure response generated by the fan adjustment action based on the actual condenser back pressure and the back pressure background response at the corresponding time. S4. Determine the incremental output of the steam turbine based on the incremental back pressure response and the unit load change information; determine the change in the active power of the fan based on the change in the active power of the fan before and after implementing the fan adjustment action; determine the adjustment benefit based on the incremental output of the steam turbine and the change in the active power of the fan; determine the fan operating status of the air-cooled area to be adjusted based on the adjustment benefit; and output the corresponding control command to the fan drive device or air-cooled unit control device of the air-cooled area to be adjusted.

2. The method for adjusting the back pressure of a direct air-cooled unit under varying loads according to claim 1, characterized in that, The unit load change information includes load commands, actual unit load, and operating parameters characterizing the turbine exhaust heat load; the back pressure background response is determined based on a pre-established correspondence between unit load changes and condenser back pressure dynamic response.

3. The method for adjusting the back pressure of a direct air-cooled unit under varying loads according to claim 1, characterized in that, The regional response time is determined based on the historical fan adjustment response data or test response data of the corresponding air-cooled region.

4. The method for adjusting the back pressure of a direct air-cooled unit under varying loads according to claim 3, characterized in that, The fan adjustment action includes changing the fan frequency, speed, or power setting value of the air-cooled area to be adjusted within the allowable adjustment range of the fan and the allowable back pressure of the condenser.

5. The method for adjusting the back pressure of a direct air-cooled unit under varying loads according to claim 1, characterized in that, When the adjustment benefit is greater than the preset benefit threshold, the fan operation state of the air-cooled area to be adjusted after the fan adjustment action is maintained; when the adjustment benefit is not greater than the preset benefit threshold, the air-cooled area to be adjusted is restored to the fan operation state before the fan adjustment action is implemented.

6. The method for adjusting the back pressure of a direct air-cooled unit under varying loads according to claim 5, characterized in that, After the air-cooled area to be adjusted is restored to the operating state of the fan before the fan adjustment action is implemented, the subsequent air-cooled areas to be adjusted are determined from the candidate air-cooled areas where the benefit evaluation has not been completed and the response time of the area is not greater than the remaining evaluation time; when the load command is updated, the current benefit evaluation is terminated, and the back pressure background response and the remaining evaluation time are re-determined according to the updated load command.

7. The method for adjusting the back pressure of a direct air-cooled unit under variable load according to any one of claims 1 to 6, characterized in that, During the evaluation period, the incremental output of the steam turbine is integrated over time to obtain the incremental output energy of the steam turbine, and the change in the active power of the wind turbine is integrated over time to obtain the incremental energy consumption of the wind turbine. The difference between the incremental output energy of the steam turbine and the incremental energy consumption of the wind turbine is used as the adjustment benefit.

8. A variable load back pressure adjustment system for a direct air-cooled unit, characterized in that, include: The status acquisition module is used to acquire information on unit load changes, condenser back pressure, fan operating status in each air-cooled zone, and the remaining evaluation time allowed for back pressure adjustment under the current load command. The background response determination module is connected to the state acquisition module and is used to determine the back pressure background response corresponding to the current load change under the condition that the fan operating state remains unchanged, based on the unit load change information and the condenser back pressure. The region determination module, connected to the status acquisition module, is used to determine the air-cooled region to be adjusted and the fan adjustment action for the air-cooled region to be adjusted based on the region response time of each candidate air-cooled region and the remaining evaluation time. The back pressure adjustment execution module is connected to the area determination module, and its control output terminal is connected to the fan drive device or air-cooling unit control device of each air-cooled area, for executing the fan adjustment action; as well as The response evaluation module is connected to the status acquisition module, the background response determination module, and the back pressure adjustment execution module, respectively. It is used to determine the incremental back pressure response based on the actual condenser back pressure after the implementation of the fan adjustment action and the back pressure background response at the corresponding time, and to determine the adjustment benefit based on the incremental back pressure response, the unit load change information, and the fan active power before and after the implementation of the fan adjustment action, and to send the adjustment benefit to the back pressure adjustment execution module. The back pressure adjustment execution module is also used to determine the fan operating status of the air-cooled area to be adjusted based on the adjustment benefit, and output control commands to the corresponding fan drive device or air-cooled unit control device.

9. The variable load back pressure adjustment system for direct air-cooled units according to claim 8, characterized in that, The status acquisition module is connected to the unit control system, the condenser back pressure detection device, and the fan drive device of each air-cooled zone; the active power of the fan is determined by the active power signal of the fan drive device or the corresponding power metering signal.

10. The variable load back pressure adjustment system for a direct air-cooled unit according to claim 8, characterized in that, The system also includes a safety constraint module, which is connected to the status acquisition module and the back pressure adjustment execution module respectively, and is used to determine safe operating conditions based on condenser back pressure, antifreeze status and fan operating status. When the adjustment benefit does not reach the preset benefit condition, the back pressure adjustment execution module outputs a control command to restore the operating state of the fan in the air-cooled area to be adjusted, and stops executing the fan adjustment action when the safe operating condition is not met.

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