Method and system for constant speed fan dry cooler outlet temperature control based on equivalent refrigeration correction and sequential array

Abstract

The application provides a constant-speed fan dry cooler outlet temperature control method and system based on equivalent cold correction and sequential array, and relates to the technical field of industrial cooling automatic control. The method comprises the following steps: collecting the dry cooler outlet medium temperature, obtaining the original load demand through PID operation; mapping the load demand to the target fan operation quantity, and confirming through partition delay; starting the non-fault non-operating fan according to the cycle start index, or stopping the operating fan according to the continuous sequential number; generating the equivalent cold compensation after the single fan switching, forming the compensated load demand, and maintaining the current operation quantity during the switching; and updating the sequential array and supplementing the standby fan for the fault fan. The system comprises temperature collection, fault detection, a controller and constant-speed fans. The scheme helps to reduce the repeated change of the number of constant-speed fans in the switching process, and facilitates the maintenance of the fan start-stop sequence and the fault state.

Description

Technical Field

[0001] This invention relates to the field of industrial cooling automatic control technology, and more specifically, to a method and system for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array. Background Technology

[0002] A dry cooler is a cooling device that uses air to exchange heat with a circulating medium. It typically includes heat exchange coils, circulating medium piping, and fans positioned around the heat exchange coils. During operation, the circulating medium flows within the coils, and the fans drive air to flow across the outer surface of the coils, thus carrying away the heat from the circulating medium. The outlet medium temperature of the dry cooler is affected by factors such as ambient temperature, circulating medium flow rate, the heat load of the cooled equipment, the degree of dust accumulation on the heat exchange coils, and the fan operating status. In applications such as data centers, auxiliary cooling of industrial equipment, thermal management of energy storage equipment, and process cooling, it is usually necessary to adjust the number of fans operating based on the outlet medium temperature to maintain the outlet medium temperature within a preset range.

[0003] Existing dry cooler fans can be variable frequency fans, EC speed-regulating fans, or fixed speed fans. Fixed speed fans typically change the ventilation volume by starting or stopping, and the airflow and heat exchange capacity of a single fan exhibit a relatively fixed step-like variation near the rated operating conditions. For dry coolers using multiple fixed speed fans, a common control method is to collect the outlet medium temperature and output the load demand through a PID controller. When the outlet medium temperature deviates from the target temperature, the controller increases or decreases the number of operating fans according to the change in load demand.

[0004] However, the start and stop of constant-speed fans is a discrete control. When a single fan starts, the airflow and heat exchange capacity on the heat exchanger side change; when a single fan stops, the heat exchange capacity decreases accordingly. When the heat load, ambient temperature, or medium temperature is changing, the temperature response after the fan is switched on or off usually exhibits a certain lag. If the controller continuously executes the start and stop of multiple fans in a short period of time, it may cause significant changes in cooling capacity, leading to fluctuations in the outlet medium temperature around the target temperature. Especially when the load demand is close to the boundary range corresponding to the number of adjacent operating fans, the PID output may repeatedly cross the boundary value with temperature fluctuations, resulting in frequent changes in the fan start and stop commands.

[0005] To mitigate the aforementioned issues, a single delay timer can be used, requiring the load demand to remain stable for a certain period before fan switching is initiated. This method can mitigate the impact of instantaneous fluctuations triggering start-stop operations to some extent. However, when the load demand spans multiple intervals or varies between adjacent intervals, the adaptability of the single delay logic to different switching processes is limited. On the other hand, if the target number of fans is determined solely based on the PID output, and the next switching decision is immediately made based on the uncorrected load demand after a fan switching operation, it may fail to adequately reflect the changes in heat exchange capacity brought about by newly activated or deactivated fans.

[0006] Furthermore, multi-fan dry coolers also need to consider the rotation operation and fault handling of each fan. Some existing solutions record the cumulative runtime of each fan and use this cumulative runtime as the basis for start-stop selection. This method requires continuous recording and comparison of the operating status and duration information of multiple fans. In application scenarios with a large number of fans or limited controller resources, the related data maintenance and comparison process increases the complexity of the control program. If the status of the operating fans and the subsequent start-stop sequence are not updated in a timely manner when a fan experiences overload, contactor malfunction, or feedback signal anomalies, it may also affect the achievement of the target number of operating fans.

[0007] Therefore, it is necessary to provide an outlet temperature control method suitable for dry coolers with multiple constant speed fans, so as to handle the changes in equivalent cooling capacity caused by fan switching based on the adjustment of the number of fans according to the temperature load requirements, and to improve the stability and maintainability of the constant speed fan array adjustment process by combining control processes such as individual fan switching, post-switching maintenance, fan sequence maintenance and fault status update. Summary of the Invention

[0008] The present invention aims to solve at least one of the aforementioned technical problems existing in the prior art.

[0009] Therefore, the first aspect of the present invention provides a method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array.

[0010] The second aspect of the present invention provides a constant speed fan dry cooler outlet temperature control system based on equivalent cooling capacity correction and sequential array.

[0011] This invention provides a method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array. The dry cooler is equipped with M constant-speed fans, where M is a positive integer. The method includes: Collect the outlet medium temperature of the dry cooler, compare the outlet medium temperature with the target temperature, and obtain the original load demand signal through PID calculation; The target number of operating fans is determined based on the original load demand signal or the compensated load demand signal obtained after equivalent cooling capacity correction. After the load demand signal has been continuously in the corresponding load range for a preset delay threshold, the number of target wind turbines in operation is compared with the number of currently effective wind turbines in operation. When the number of target fans in operation is greater than the number of currently active fans, start one fault-free and non-operating constant-speed fan; when the number of target fans in operation is less than the number of currently active fans, stop one operating fan. After each start-up or stop of a fixed-speed fan, a compensation amount is generated based on the equivalent cooling capacity of the fixed-speed fan. When the fixed-speed fan is started, the compensation amount is used to reduce the original load demand signal to obtain the compensated load demand signal. When the fixed-speed fan is stopped, the compensation amount is used to increase the original load demand signal to obtain the compensated load demand signal. During the preset post-switching hold period, the number of currently effective operating wind turbines obtained after the switching is maintained, and after the post-switching hold period ends, the target number of operating wind turbines is determined and the next start-up and shutdown of a single wind turbine is executed using the compensated load demand signal. The original load demand signal is not rewritten by the compensation amount, the compensation amount is maintained or attenuated during the preset compensation period, and becomes invalid after the compensation period ends. Each time a fixed-speed fan is started, the fault-free and non-operating fixed-speed fans are cyclically screened starting from the position indicated by the cycle start index, and a continuous sequence number is assigned to the operating fans after startup; each time a fixed-speed fan is stopped, the operating fan with the smallest continuous sequence number is stopped, and the continuous sequence numbers of the remaining operating fans are moved forward to update.

[0012] The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array according to the above-described technical solution of the present invention may also have the following additional technical features: In the above technical solution, the number of target wind turbines in operation is determined according to M+1 consecutive non-overlapping load intervals; When the load demand signal is less than or equal to 100% / (M+1), the number of target wind turbines in operation is 0; When k×100% / (M+1)<the load demand signal≤(k+1)×100% / (M+1), the number of target wind turbines in operation is k, where k is an integer from 1 to M.

[0013] In the above technical solution, the compensation amount is determined based on the design cooling capacity, air volume parameters, or equivalent cooling capacity of the switched constant speed fan as a proportion of the total cooling capacity of all constant speed fans; for constant speed fans with the same equivalent cooling capacity, the compensation amount is set according to a value corresponding to the width of a load gear.

[0014] In the above technical solution, the compensation amount maintains the initial compensation value during the compensation period, or gradually decreases to zero according to a preset attenuation rule; after the end of the post-switching maintenance period, the direction of the next start-up and shutdown of a single wind turbine is determined based on the post-compensation load demand signal that is still in an effective state.

[0015] In the above technical solution, a delay timer is configured for each load interval; when the load demand signal leaves the corresponding load interval, the corresponding delay timer is reset; the corresponding target number of wind turbines is output only when the load demand signal continuously resides in the same load interval and reaches the corresponding delay threshold.

[0016] In the above technical solution, the cyclic start index is updated to the position after the started constant speed fan after each start of the constant speed fan; the continuous sequence number is arranged continuously starting from 1 in the current set of running fans, and the cumulative running time of each constant speed fan is not stored.

[0017] In the above technical solution, the fault signals of each constant-speed fan are acquired in real time; when a running fan fails, the faulty fan is stopped and its consecutive sequence number is cleared, and the consecutive sequence numbers of the remaining running fans whose consecutive sequence numbers are greater than the consecutive sequence number of the faulty fan are moved forward in sequence; when there is a faultless and non-running constant-speed fan, and the number of currently effective running fans is less than the target number of running fans, one of the faultless and non-running constant-speed fans is started.

[0018] In the above technical solution, the method has a manual control mode; in the manual control mode, the number of target wind turbines in operation is received from the outside and limited from 0 to M, the start and stop of a single wind turbine is executed according to the cyclic start index and continuous sequence number, and the shutdown processing of the faulty wind turbine is retained.

[0019] The present invention provides an outlet temperature control system for a constant speed fan dry cooler based on equivalent cooling capacity correction and sequential array, comprising a dry cooler, M constant speed fans, an outlet temperature acquisition module, a fan fault detection module and a controller. The outlet temperature acquisition module is used to acquire the outlet medium temperature of the dry cooler; the fan fault detection module is used to output fault signals for each constant speed fan. The controller is connected to the outlet temperature acquisition module, the fan fault detection module and the M fixed-speed fans respectively. The controller includes a PID control unit, an equivalent cooling capacity correction unit, a load classification mapping unit, a delay anti-shake unit and a sequential start / stop and array maintenance unit. The PID control unit is used to generate the original load demand signal based on the outlet medium temperature and the target temperature. The equivalent cooling capacity correction unit is used to generate a compensation amount after a single constant speed fan starts or stops, and to generate a compensated load demand signal based on the original load demand signal and the compensation amount. The load grading mapping unit is used to determine the target number of operating wind turbines based on the original load demand signal or the compensated load demand signal. The delay anti-shake unit is used to maintain the number of currently effective operating wind turbines during the hold period after switching on; The sequential start / stop and array maintenance unit is used to adjust the number of fixed-speed fans in single-unit switching mode, select the start fan according to the cyclic start index, select the stop fan according to the continuous sequence number, and maintain the continuous sequence number.

[0020] In the above technical solution, the controller further includes an automatic / manual mode switching unit and an alarm unit; the automatic / manual mode switching unit is used to switch between automatic control mode and manual control mode; the alarm unit is used to output alarm information for fan failure, outlet medium temperature exceeding the tolerance, or frequent load demand signal skipping.

[0021] In summary, due to the adoption of the above-mentioned technical features, the beneficial effects of the present invention are: This invention distinguishes between the raw load demand signal obtained from PID calculations and the compensated load demand signal used for fan switching decisions. After a single constant-speed fan starts or stops, a compensation amount is generated based on the equivalent cooling capacity corresponding to that fan, and this compensation amount is used to correct the load demand signal used to determine the number of subsequent fans. Therefore, the impact of increased or decreased heat exchange capacity on control decisions can be reflected after fan switching, reducing continuous same-direction or reverse switching caused by directly using uncorrected load demand.

[0022] This invention adjusts the number of operating fans by sequentially switching on and off individual fans and maintaining this switching status. When there is a difference between the target number of operating fans and the current number of effectively operating fans, only one fan is started or stopped at a time. After completing this switching operation, the current number of effectively operating fans is maintained, and the next judgment is made after the maintenance period ends. This method decomposes the large change in cooling capacity caused by the simultaneous switching on and off of multiple fans into multiple single-fan switching processes, which helps to gradually change the outlet medium temperature towards the target temperature and reduces the possibility of repeated changes in the number of fans in a short period of time.

[0023] This invention employs a delay confirmation mechanism for different load ranges. The corresponding target number of operating fans is only output after the load demand signal has continuously resided within the same load range for a specified delay threshold. This mechanism can filter out short-term fluctuations in outlet medium temperature, disturbances in the acquired signal, and critical changes in load demand, ensuring that fan switching commands correspond to continuous load changes.

[0024] This invention determines the wind turbine start-up and shutdown targets through a cyclic start-up index and consecutive sequential numbering. During start-up, a fault-free and non-operating wind turbine is selected according to the cyclic start-up index; during shutdown, the operating wind turbine with the smaller consecutive sequential number is selected, and the sequential numbers of the remaining operating wind turbines are updated after shutdown. This method does not rely on continuously recording and comparing the cumulative operating time of each wind turbine, simplifying the maintenance process of wind turbine start-up and shutdown sequence while meeting the requirements of rotational operation.

[0025] This invention updates the operating status and sequence number of the faulty wind turbine when a fault occurs, and starts the backup wind turbine when there is an available backup wind turbine and the effective number of operating turbines is lower than the target number. Therefore, the subsequent wind turbine start-up and shutdown logic can continue to execute based on the updated actual operating status, which is convenient for maintaining the effective number of operating wind turbines in the array and supports operation management under fault conditions.

[0026] This invention also provides automatic control mode and manual control mode. In automatic control mode, fan adjustment is performed according to the outlet medium temperature and load requirements; in manual control mode, fan control can be performed according to the externally set target number of fans in operation, while retaining fault protection processing. This setting facilitates control switching under different operating conditions such as normal operation, commissioning, maintenance, or abnormal handling.

[0027] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a flowchart of an embodiment of the present invention of a method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array; Figure 2 This is a schematic diagram of the start-stop logic of the fan sequential array in a method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array, according to an embodiment of the present invention. Detailed Implementation

[0029] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0030] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0031] The following reference Figures 1 to 2 This invention describes a method and system for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array, according to some embodiments of the present invention.

[0032] Some embodiments of this application provide a method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array. The technical solution of this application is further described below with reference to the accompanying drawings. It should be understood that the following embodiments are used to illustrate the technical concept and implementability of this application and do not constitute a limitation on the scope of protection. Those skilled in the art can set the temperature sampling period, PID parameters, delay threshold, compensation parameters, and hold time according to the structure of the dry cooler, the number of fans, the medium flow rate, the heat exchange capacity, the controller type, and the on-site operating conditions.

[0033] This application applies to a dry cooler composed of multiple constant-speed fans. When a constant-speed fan starts or stops, the corresponding airflow and heat exchange capacity change discretely. The outlet medium temperature of the dry cooler is also affected by factors such as ambient temperature, circulating medium flow rate, heat load of the cooled equipment, heat exchange coil status, and fan operating status. To adapt to the discrete adjustment characteristics of constant-speed fans, this application formulates load demand based on the outlet medium temperature and performs equivalent cooling capacity correction on the load demand used to determine the number of subsequent fans after a single fan is switched on or off. Simultaneously, it adjusts the number of operating fans by switching them on and off sequentially and maintaining the fan start-up and shutdown sequence through a cyclic start index and continuous sequential numbering.

[0034] In some embodiments, the dry cooler includes heat exchange coils and M constant-speed fans, where M is a positive integer. The M constant-speed fans can be arranged in the same heat exchange unit or distributed across multiple parallel heat exchange units. Each constant-speed fan can be driven by a power frequency motor and started and stopped via a contactor, soft starter, or other on / off control components suitable for constant-speed fans. Each fan can have an operating feedback signal, a fault feedback signal, or both. The fault feedback signal may include an overload protection activation signal, a thermal relay activation signal, a contactor status abnormality signal, an operating feedback abnormality signal, or other signals indicating that the fan cannot be put into normal operation.

[0035] In some embodiments, an outlet temperature acquisition module is installed in the outlet pipeline of the dry cooler to acquire the outlet circulating medium temperature. The outlet temperature acquisition module can employ a PT100 temperature sensor, thermocouple, thermistor temperature sensor, or other industrial temperature sensor. The signal acquired by the temperature sensor can be transmitted to the controller via a temperature transmitter, isolator, or analog input module. The controller can be a PLC, DCS controller, industrial controller, embedded controller, or computing device with corresponding input / output interfaces.

[0036] like Figure 1 As shown, Figure 1 The present application illustrates the outlet temperature control process for a constant-speed fan dry cooler according to this application. This process includes temperature acquisition, load demand calculation, load range determination, delay confirmation, target number of operating units determination, comparison of current effective number of operating units, single fan switching, equivalent cooling capacity correction, post-switching hold, sequential array maintenance, and fault detection and handling.

[0037] In automatic control mode, the controller periodically collects the outlet medium temperature of the dry cooler. Let the actual outlet medium temperature be T, and the target temperature be Tset, then the temperature deviation can be expressed as e = T - Tset. When the actual outlet medium temperature is higher than the target temperature, the temperature deviation is positive, and the controller increases the cooling demand accordingly; when the actual outlet medium temperature is lower than the target temperature, the temperature deviation is negative, and the controller reduces the cooling demand accordingly.

[0038] The controller performs PID calculations on the temperature deviation to obtain the original load demand signal. This original load demand signal can be normalized to a continuous signal from 0% to 100%. 0% indicates that the controller determines the cooling demand to be at the minimum level, while 100% indicates that the controller determines the cooling demand to be at or near the maximum level corresponding to the operation of all fans. The PID controller can employ positional PID, incremental PID, or other conventional PID control structures.

[0039] In some embodiments, the PID controller can be configured with integral limiting, derivative filtering, and output limiting functions to adapt to controlled objects where the outlet medium temperature has a certain thermal inertia. The PID parameters can be tuned based on the heat exchange capacity of the dry cooler, the flow rate of the circulating medium, the temperature sampling period, and the response to changes in the outlet temperature. The PID calculation can be performed within each control cycle or according to a preset control cycle.

[0040] In one specific embodiment, the original load demand signal It can be obtained using the following formula:

[0041] in, , and These are the proportional coefficient, integral coefficient, and differential coefficient, respectively. This represents a limiting function that restricts the calculation result to between 0% and 100%. This expression is only used to illustrate that the original load demand signal can be obtained using conventional PID calculations, and does not require the PID controller to use this mathematical form.

[0042] The controller maps the current effective load demand signal to the target operating number of fans. The current effective load demand signal is the original load demand signal when no effective compensation amount is generated; and is the compensated load demand signal after a single fan is switched on or off and the compensation amount is in an effective state. The current number of effectively operating fans is denoted as Na, where Na represents the number of constant-speed fans that are currently in operation and have not been detected with a fault; the target operating number of fans is denoted as N. The controller determines whether it is necessary to increase or decrease the number of operating fans by comparing the magnitude relationship between N and Na.

[0043] In some embodiments, the controller divides the load demand range from 0% to 100% into M+1 consecutive and non-overlapping load intervals, and associates each load interval with a different target operating number of fans. Specifically, when the current effective load demand signal is less than or equal to 100% / (M+1), the target operating number of fans N is 0; when k×100% / (M+1) < the current effective load demand signal ≤ (k+1)×100% / (M+1), the target operating number of fans N is k, where k is an integer from 1 to M.

[0044] In a specific embodiment, the dry cooler is equipped with 10 constant-speed fans, M is 10, the load demand range is divided into 11 load intervals, and the width of each load interval is approximately 9.09%. When the current effective load demand signal is 55%, 55% is greater than 6×100% / 11 and less than or equal to 7×100% / 11, and the corresponding target operating number of fans is 6. This example is used to illustrate the mapping relationship between the load intervals and the target operating number of fans, and in practical applications, M is determined according to the number of fans matched with the dry cooler.

[0045] To avoid short-term changes of the load demand signal near the boundary of adjacent load intervals from directly causing fan switching, a delay timer is respectively set for each load interval. When the current effective load demand signal enters a certain load interval, the delay timer corresponding to this interval starts timing; when the current effective load demand signal leaves this interval, the corresponding delay timer resets. Only after the current effective load demand signal continuously stays in the same load interval for the corresponding delay threshold, the controller confirms the target operating number of fans corresponding to this load interval.

[0046] In some embodiments, the delay thresholds of the respective load intervals may be the same, or may be set separately according to different working conditions. The gear positions close to the commonly used operating load interval can be set with a relatively long delay threshold to reduce fan switching caused by short-term fluctuations in outlet temperature; the gear positions that require a faster response can be set with a relatively short delay threshold.

[0047] In one specific embodiment, the delay threshold can be set in the range of 30 seconds to 300 seconds. The specific value of the delay threshold can be set according to the heat exchange capacity of the dry cooler, the flow rate of the circulating medium, the sampling frequency of the outlet temperature, the rate of change of the ambient temperature, and the allowable temperature change range of the object being cooled.

[0048] Figure 1 The delay confirmation step includes: reading the current effective load demand signal, determining the load interval where the signal is located, resetting the timer corresponding to the interval other than the current interval, timing the timer corresponding to the current interval, determining whether the timing result has reached the corresponding delay threshold, and outputting the target number of operating wind turbines after reaching the delay threshold. If the current effective load demand signal enters another load interval during the timing process, the timing result of the original load interval will not be used as the basis for outputting the number of effective wind turbines.

[0049] When the target number of operating fans N is greater than the current number of operating fans Na, the controller needs to increase the number of operating fans. When the target number of operating fans N is less than the current number of operating fans Na, the controller needs to decrease the number of operating fans. When N equals Na, the controller maintains the current number of operating fans.

[0050] In some embodiments, when N is greater than Na, the delay confirmation condition is met, and the system is not in a post-switching hold state, the controller starts only one fault-free and non-operating constant-speed fan. After the start command is issued, the controller can confirm whether the fan has entered the operating state based on the fan operation feedback signal; if no operation feedback signal is set, the controller can also determine whether the fan can be counted as a validly operating fan in Na after a preset start confirmation time, combined with the fault signal.

[0051] In some embodiments, when N is less than Na, the delay confirmation condition is met, and the system is not in a post-switching hold state, the controller stops only one operating fan. After the stop command is issued, the controller can confirm that the fan has exited the operating state based on the operation feedback signal, the contactor status signal, or the preset stop confirmation time.

[0052] This application does not simultaneously start or stop multiple fans within the same regular adjustment cycle. After completing the start or stop of a single fan, the controller updates Na and enters a hold state after switching. During the hold period, the controller continues to collect the outlet medium temperature and perform PID calculations, but does not immediately adjust the number of fans based on changes in regular load demand. After the hold period ends, the controller re-determines the target number of operating fans; if the target number of operating fans is still inconsistent with the currently effective number of operating fans, the next single fan switching is performed according to the current status.

[0053] After a single fan starts or stops, the corresponding change in heat exchange capacity takes a certain amount of time to be fully reflected in the outlet medium temperature. To reflect the equivalent cooling capacity corresponding to the fans that have been switched on or off during this process, this implementation generates a compensation amount after each fan is switched on or off. When a fan is started, the increased airflow and heat exchange capacity will be reflected in the subsequent temperature response, so the controller generates a compensation amount to reduce the subsequent load demand judgment result; when a fan is stopped, the reduced airflow and heat exchange capacity will be reflected in the subsequent temperature response, so the controller generates a compensation amount to improve the subsequent load demand judgment result.

[0054] In some embodiments, the controller retains the original load demand signal. and in accordance with Forming a compensated load demand signal The compensation value 'b' is negative after the fan starts and positive after the fan stops. The absolute value of 'b' corresponds to the equivalent cooling capacity of the fan being switched on or off. Original load demand signal. The load demand signal is not rewritten due to the compensation amount b. Used to determine the number of wind turbines in operation later.

[0055] The control implications of the above compensation method are as follows: after starting a fan, the controller includes the equivalent cooling capacity provided by the newly added fan in the subsequent number of fans determination, so as to avoid continuously adding fans before the new heat exchange capacity is fully reflected in the outlet temperature; after stopping a fan, the controller includes the reduced equivalent cooling capacity in the subsequent number of fans determination, so as to avoid continuously reducing the number of fans before the reduced heat exchange capacity is fully reflected in the outlet temperature.

[0056] In some embodiments, the compensation amount can be determined based on the design cooling capacity, rated air volume, heat exchange contribution ratio, or equivalent cooling capacity of the switched-on constant-speed fan relative to the total cooling capacity of all constant-speed fans. For constant-speed fans of different specifications, air volumes, or locations, compensation parameters corresponding to each fan can be established separately. For constant-speed fans of the same specifications, similar air volumes, and basically identical arrangement conditions, the same compensation parameters can be used.

[0057] In one specific embodiment, for M constant-speed fans with the same equivalent cooling capacity, the initial compensation amount for a single fan can be set to a load range width, i.e., 100% / (M+1), or set to the load range width multiplied by a correction factor obtained through on-site tuning. The correction factor can be determined based on the response speed of the outlet medium temperature after the single fan starts, the heat exchange area of ​​the dry cooler, the circulating medium flow rate, and the ambient temperature.

[0058] In some embodiments, the compensation amount is valid for a preset compensation period. The compensation period can begin timing from the time the fan starts, stops, or a fan starts / stops command is issued. The post-switching hold period is used to temporarily maintain the number of currently active fans, while the compensation period is used to allow the compensated load demand signal to participate in subsequent fan count determination. After the hold period ends, if the compensation amount is still valid, the controller determines the next start / stop direction for a single fan based on the compensated load demand signal; after the compensation period ends, the compensation amount becomes invalid, and the controller resumes determining the fan count based on the original load demand signal.

[0059] In some embodiments, the compensation amount can remain at its initial value during the compensation period, or it can be gradually reduced to zero using linear decay, exponential decay, piecewise step decay, or a lookup table method. The hold-up period after switching can be shorter than the compensation period, so that after the hold-up period ends, the post-compensation load demand signal formed by the effective compensation amount can still be used for the next unit count determination. The compensation period and the hold-up period after switching can be set based on the heat exchange response time of the dry cooler, the circulation time of the circulating medium, the temperature sampling period, and the results of on-site commissioning.

[0060] In one specific embodiment, the dry cooler is equipped with 10 constant-speed fans. Currently, 4 fans are actively operating, the original load demand signal is 55%, and the target number of operating fans, mapped according to the load range, is 6. After meeting the delay confirmation condition, the controller first starts one fault-free and non-operating fan, bringing Na to 5. The controller then generates a compensation amount corresponding to the equivalent cooling capacity of the newly added fan and enters a hold state after switching. After the hold state ends, the controller again determines whether to increase the number of operating fans based on the compensated load demand signal. If the outlet medium temperature still causes the controller to determine that the number of operating fans needs to be increased, then another fan is started, bringing Na to 6. This process decomposes the adjustment process, which might have involved starting two fans simultaneously, into two single-fan start-up processes.

[0061] In another specific embodiment, the current number of operating fans is 6, while the target number of operating fans confirmed by load range mapping is 3. The controller first stops only one operating fan, making Na a total of 5 fans; then it generates a compensation amount corresponding to the stopped fan and enters a hold state after switching. After the hold state ends, the controller again determines whether to continue reducing the number of fans. If there is still a difference in the number of fans, the next single-fan shutdown is executed. Thus, the process of adjusting 6 fans to 3 fans is decomposed into multiple single-fan shutdown processes.

[0062] This application also maintains the sequence of starting and stopping the operating fans. For example... Figure 2 As shown, Figure 2 The upper part can show the sequential startup process. Figure 2The lower section can show the sequential stopping process. The controller sets a cyclic start index, which indicates the priority retrieval position when adding a new fan. Each constant-speed fan can be numbered according to its physical number F1, F2, ..., FM, and the value range of the cyclic start index can be from 1 to M.

[0063] In some embodiments, when a fan needs to be started, the controller starts by cyclically searching for the fan indicated by the cyclic start index, following an ascending order of physical numbers. During the search, running fans and fans in a faulty state are skipped; when a fault-free and non-running fan is found, the controller starts that fan. If no startable fan is found by the time the search reaches FM, the search continues from F1 until a startable fan is found or the search of all fans is completed.

[0064] Newly started wind turbines are assigned sequential numbers within the currently operating turbine set. These sequential numbers indicate the order in which each turbine was put into operation within the current set, not the number of times it has been permanently started in the past. For example, if there are currently four operating turbines with sequential numbers 1, 2, 3, and 4, when the fifth turbine is started, it is assigned the sequential number 5. After startup, the cyclic startup index is updated to the physical number position following the already started turbines; if this position exceeds M, the cyclic startup index wraps back to 1.

[0065] In some embodiments, when it is necessary to stop a running fan, the controller selects the fan with the smallest consecutive sequential number in the current set of running fans to perform the shutdown. After shutdown, the consecutive sequential number of the stopped fan is cleared to zero; the consecutive sequential numbers of the remaining running fans with consecutive sequential numbers greater than the number of the stopped fan are decremented by 1 or equivalently shifted forward, so that the sequential numbers in the current set of running fans are restored to a consecutive sequence starting from 1.

[0066] In one specific embodiment, the currently operating fan set contains 6 fans, whose sequential numbers are 1, 2, 3, 4, 5, and 6. When it is necessary to remove one operating fan, the controller stops the fan with the sequential number 1 and updates the remaining operating fans, originally numbered 2, 3, 4, 5, and 6, to 1, 2, 3, 4, and 5 respectively. Subsequent times when it is necessary to stop a fan, the controller stops the fan with the updated sequential number 1.

[0067] In some embodiments, when the system is first powered on, the controller is reset, or all fans are stopped, the cyclic start index is initialized to 1, the currently running fan set is empty, and the sequential number of each fan is 0. When a fan needs to be started subsequently, the controller searches for fault-free and non-running fans starting from F1. The cyclic start index can also be initialized according to a preset initial number, the index position before the last shutdown, or other configurable initial values.

[0068] The sequential array maintenance in this application does not require continuous storage and comparison of the cumulative runtime of each wind turbine. Wind turbine rotation is achieved through cyclic retrieval of the cyclic start index and a first-to-first-to-stop rule. In some embodiments, to meet equipment maintenance management needs, the cumulative runtime, number of starts, or maintenance status of the wind turbines can be additionally stored in the controller or host computer, but this additional information does not affect the basic process of performing start-stop control based on the cyclic start index and consecutive sequential numbering.

[0069] The controller acquires fault signals from each constant-speed fan in real time or periodically. When a fault is detected in a fan that is in operation, the controller marks the fan as faulty and controls it to stop or remain stopped. The priority of fan fault handling can be higher than that of conventional on / off hold control to ensure that the faulty fan does not continue to operate.

[0070] In some embodiments, after a faulty fan stops, the controller clears the sequential number of that faulty fan. If the original sequential number of the faulty fan was j, then the sequential numbers of the remaining operating fans with sequential numbers greater than j are decremented by 1 in sequence, so that the sequential numbers within the set of operating fans remain continuous. For example, if the current sequential numbers of the operating fans are 1, 2, 3, 4, 5, 6, and the fan with sequential number 4 fails and stops operating, then that fan's number is cleared to zero, and the fans originally numbered 5 and 6 are updated to 4 and 5 respectively.

[0071] After a faulty fan is taken out of service, the controller updates Na. If Na is less than N, and there are still fault-free and non-operating standby fans, the controller selects a fault-free and non-operating fan according to the cyclic start index and starts it to replenish the number of valid operating fans. After starting the standby fan, it is assigned the next consecutive sequential number from the currently operating fan set, and the cyclic start index is updated.

[0072] In some embodiments, when no standby fans are available, the controller maintains the status of the existing operational fans and outputs an alarm message indicating insufficient fan quantity or fan failure. The closed-loop calculation of outlet medium temperature and load demand can still be performed, and the controller performs subsequent control based on the actual number of available fans. After manual repair, fault reset, or restoration of operating conditions, a faulty fan can be reinstated as a candidate fan for subsequent cycle startup searches if it is not currently in operation and is fault-free.

[0073] In some embodiments, the controller has an automatic control mode and a manual control mode. In automatic control mode, the controller performs processes such as temperature acquisition, PID load demand calculation, load range mapping, delay confirmation, equivalent cooling capacity correction, post-switching hold, and sequential array maintenance.

[0074] In manual control mode, the operator, host computer, or external control system inputs the target number of operating fans, Nm, to the controller. The controller limits Nm from 0 to M and uses the limited Nm as the target number of operating fans. When Nm is greater than Na, the controller starts the fault-free and non-operating fans one by one according to the cyclic start index; when Nm is less than Na, the controller stops the operating fans one by one according to their sequential numbers.

[0075] In some embodiments, the manual control mode bypasses the PID load demand calculation, load range mapping, automatic delay confirmation, and automatic equivalent cooling capacity correction processes based on the outlet medium temperature; fan fault detection, faulty fan shutdown, and necessary electrical protection logic are still retained. The manual control mode is suitable for equipment commissioning, maintenance, trial operation, or situations where the number of fans operating needs to be specified by an external system. When switching from manual control mode to automatic control mode, the controller can use the currently active number of fans, the current cycle start index, and the current sequential number as the initial state for automatic control mode, and continue executing the automatic control process.

[0076] Other embodiments of this implementation also provide a constant-speed fan dry cooler outlet temperature control system for performing the above control method, applied to the method described in any of the above embodiments. The system includes a dry cooler, M constant-speed fans, an outlet temperature acquisition module, a fan fault detection module, a controller, an automatic / manual mode switching unit, and an alarm unit.

[0077] In some embodiments, the outlet temperature acquisition module is used to acquire the outlet medium temperature of the dry cooler and send the temperature signal to the controller. The fan fault detection module is used to acquire the fault status of each constant-speed fan and output a fault signal to the controller. The controller is connected to the outlet temperature acquisition module, the fan fault detection module, and the start / stop control loop of each constant-speed fan.

[0078] The controller includes a PID control unit, an equivalent cooling capacity correction unit, a load grading mapping unit, a delay anti-jitter unit, and a sequential start / stop and array maintenance unit. The PID control unit generates the original load demand signal based on the outlet medium temperature and the target temperature; the equivalent cooling capacity correction unit generates a compensation amount after a single fan starts or stops, and forms a compensated load demand signal based on the original load demand signal and the compensation amount; the load grading mapping unit determines the target number of operating fans based on the current effective load demand signal; the delay anti-jitter unit confirms the dwell time of the load interval and maintains the number of currently effective operating fans during the hold period after switching; the sequential start / stop and array maintenance unit adjusts the number of operating fans in a single-fan switching manner, selects the starting fan according to the cyclic start index, selects the stopping fan according to the continuous sequence number, and updates the continuous sequence number after a fan stops or malfunctions.

[0079] In some embodiments, the aforementioned units can be implemented using independent hardware circuits, PLC function blocks, controller software modules, program tasks, register variables, state machines, or combinations thereof. For example, the PID control unit, equivalent cooling capacity correction unit, load grading mapping unit, and delay anti-jitter unit can be implemented by a control program executed periodically by the controller; the sequential start / stop and array maintenance unit can be implemented using a fan status table, a cyclic start index variable, a consecutive sequence number variable, and corresponding logical judgment programs. Data can be transferred between units through controller internal variables, memory addresses, communication messages, or function calls.

[0080] In some embodiments, the automatic / manual mode switching unit is used to switch between automatic control mode and manual control mode. The alarm unit outputs alarm information such as fan failure, outlet medium temperature exceeding the preset allowable range, frequent shifts in load demand signal, insufficient number of available fans, abnormal temperature sensor, or abnormal controller communication. The criterion for frequent shifts is that within a specified time window, the PID output repeatedly crosses the threshold value due to temperature fluctuations, causing the fan start / stop command to change more frequently than the rated number of times. Alarm information can be displayed through relay outputs, indicator lights, buzzers, industrial communication interfaces, human-machine interfaces, or a host computer monitoring platform.

[0081] Through the above system structure, the controller can obtain the outlet medium temperature and the status of each constant speed fan, and perform load demand calculation, equivalent cooling capacity correction, load range mapping, delay confirmation, one-by-one switching, post-switching hold, sequential array maintenance and fault handling processes, thereby realizing the outlet temperature control of multiple constant speed fan dry coolers.

[0082] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0083] Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.

Claims

1. A method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array, characterized in that, The dry cooler is equipped with M constant-speed fans, where M is a positive integer. The method includes: Collect the outlet medium temperature of the dry cooler, compare the outlet medium temperature with the target temperature, and obtain the original load demand signal through PID calculation; The target number of operating fans is determined based on the original load demand signal or the compensated load demand signal obtained after equivalent cooling capacity correction. After the load demand signal has been continuously in the corresponding load range for a preset delay threshold, the number of target wind turbines in operation is compared with the number of currently effective wind turbines in operation. When the number of target fans in operation is greater than the number of currently active fans, start one fault-free and non-operating constant-speed fan; when the number of target fans in operation is less than the number of currently active fans, stop one operating fan. After each start-up or stop of a fixed-speed fan, a compensation amount is generated based on the equivalent cooling capacity of the fixed-speed fan. When the fixed-speed fan is started, the compensation amount is used to reduce the original load demand signal to obtain the compensated load demand signal. When the fixed-speed fan is stopped, the compensation amount is used to increase the original load demand signal to obtain the compensated load demand signal. During the preset post-switching hold period, the number of currently effective operating wind turbines obtained after the switching is maintained, and after the post-switching hold period ends, the target number of operating wind turbines is determined and the next start-up and shutdown of a single wind turbine is executed using the compensated load demand signal. The original load demand signal is not rewritten by the compensation amount, the compensation amount is maintained or attenuated during the preset compensation period, and becomes invalid after the compensation period ends. Each time a fixed-speed fan is started, the fault-free and non-operating fixed-speed fans are cyclically screened starting from the position indicated by the cycle start index, and a continuous sequence number is assigned to the operating fans after startup; each time a fixed-speed fan is stopped, the operating fan with the smallest continuous sequence number is stopped, and the continuous sequence numbers of the remaining operating fans are moved forward to update.

2. The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array as described in claim 1, characterized in that, The number of target wind turbines in operation is determined according to M+1 consecutive non-overlapping load intervals; When the load demand signal is less than or equal to 100% / (M+1), the number of target wind turbines in operation is 0; When k×100% / (M+1)<the load demand signal≤(k+1)×100% / (M+1), the number of target wind turbines in operation is k, where k is an integer from 1 to M.

3. The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array as described in claim 1, characterized in that, The compensation amount is determined based on the design cooling capacity, air volume parameters, or equivalent cooling capacity of the switched constant-speed fan as a proportion of the total cooling capacity of all constant-speed fans; for constant-speed fans with the same equivalent cooling capacity, the compensation amount is set according to a value corresponding to the width of a load gear.

4. The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array as described in claim 1, characterized in that, The compensation amount remains at its initial compensation value during the compensation period, or gradually decreases to zero according to a preset attenuation rule; after the end of the post-switching holding period, the direction of the next start-up and shutdown of a single wind turbine is determined based on the post-compensation load demand signal that is still in an effective state.

5. The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array according to claim 1, characterized in that, A delay timer is configured for each load interval; when the load demand signal leaves the corresponding load interval, the corresponding delay timer is reset; the corresponding target number of operating wind turbines is output only when the load demand signal continuously resides in the same load interval and reaches the corresponding delay threshold.

6. The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array according to claim 1, characterized in that, The cyclic start index is updated to the position after the started constant speed fan after each start of the constant speed fan; the continuous sequence number is arranged continuously starting from 1 in the current set of running fans, and the cumulative running time of each constant speed fan is not stored.

7. The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array according to claim 1, characterized in that, The system acquires fault signals from each constant-speed fan in real time. When a running fan fails, it stops the faulty fan and clears its sequential number. The sequential numbers of the remaining running fans whose sequential numbers are greater than those of the faulty fan are then moved forward in sequence. If there is a fault-free and non-running constant-speed fan, and the number of currently active running fans is less than the target number of running fans, one of the fault-free and non-running constant-speed fans is started.

8. The method for controlling the outlet temperature of a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array according to claim 1, characterized in that, The method has a manual control mode; in the manual control mode, the target number of operating wind turbines is received from the outside and limited from 0 to M, and the start and stop of a single wind turbine is executed according to the cyclic start index and continuous sequence number, while retaining the shutdown processing of the faulty wind turbine.

9. A constant-speed fan dry cooler outlet temperature control system based on equivalent cooling capacity correction and sequential array, characterized in that, Includes a dry cooler, M constant-speed fans, an outlet temperature acquisition module, a fan fault detection module, and a controller; The outlet temperature acquisition module is used to acquire the outlet medium temperature of the dry cooler; the fan fault detection module is used to output fault signals for each constant speed fan. The controller is connected to the outlet temperature acquisition module, the fan fault detection module and the M fixed-speed fans respectively. The controller includes a PID control unit, an equivalent cooling capacity correction unit, a load classification mapping unit, a delay anti-shake unit and a sequential start / stop and array maintenance unit. The PID control unit is used to generate the original load demand signal based on the outlet medium temperature and the target temperature. The equivalent cooling capacity correction unit is used to generate a compensation amount after a single constant speed fan starts or stops, and to generate a compensated load demand signal based on the original load demand signal and the compensation amount. The load grading mapping unit is used to determine the target number of operating wind turbines based on the original load demand signal or the compensated load demand signal. The delay anti-shake unit is used to maintain the number of currently effective operating wind turbines during the hold period after switching on; The sequential start / stop and array maintenance unit is used to adjust the number of fixed-speed fans in single-unit switching mode, select the start fan according to the cyclic start index, select the stop fan according to the continuous sequence number, and maintain the continuous sequence number.

10. The outlet temperature control system for a constant-speed fan dry cooler based on equivalent cooling capacity correction and sequential array according to claim 9, characterized in that, The controller also includes an automatic / manual mode switching unit and an alarm unit; the automatic / manual mode switching unit is used to switch between automatic control mode and manual control mode; the alarm unit is used to output alarm information for fan failure, outlet medium temperature exceeding the tolerance, or frequent overshooting of load demand signal.

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