Control method for variable dew point air supply of all-air air conditioning system in summer

Abstract

The invention relates to a variable dew point control method of an all-air air conditioning system, belongs to the technical field of heating ventilation air conditioners, and solves the technical problems of temperature and humidity coupling in the prior art and difficulty in landing of a chilled water temperature resetting technology. The control method comprises the steps of S1, parameter initialization, S2, system starting and stabilizing, S3, air supply dew point dynamic adjustment and cold water valve control, S4, temperature and air supply amount control and S5, fresh air optimization and air valve control. The water supply temperature is adjusted by dynamically adjusting the air supply dew point and dynamically increasing the temperature of the outlet of the surface air cooler, the energy efficiency of the unit is remarkably improved, and the system is suitable for the chilled water temperature resetting technology and compatible with the application of the medium-temperature water supply technology.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of heating, ventilation and air conditioning, and particularly relates to a control method for summer variable dew point air supply of a full-air air conditioning system. BACKGROUND

[0002] In the technical field of heating, ventilation and air conditioning, full-air air conditioning systems are widely used in large public buildings such as office buildings, shopping malls and exhibition centers. In particular, under the condition of high temperature and high humidity in summer, the demand for air treatment and temperature and humidity control is particularly prominent. At present, the fixed dew point control is the mainstream operation mode of the full-air air conditioning system. The core logic is based on the summer heat and humidity load calculation results in the building design stage, and a fixed machine dew point temperature is preset. Regardless of the fluctuation of indoor sensible heat load and wet load in actual operation, the air conditioning unit needs to process the mixed air of fresh air and return air to the fixed machine dew point temperature. If the supply air temperature is lower than the minimum indoor supply air temperature requirement, the supply air temperature needs to be adjusted by reheating or air mixing to meet the demand. Although the fixed dew point control has the advantages of simple logic and easy implementation, it has significant shortcomings in energy saving, especially in contradiction with the energy saving demand of high-efficiency machine room cold source system. The energy efficiency ratio of the water chiller is positively related to the supply water temperature. The energy efficiency ratio of the water chiller can be increased by 3% for every 1℃ increase in the supply water temperature. However, under the fixed dew point control mode, the supply water temperature of the water chiller needs to match the fixed dew point supply air demand and cannot be dynamically adjusted according to the actual load. Even if the indoor wet load decreases, the water chiller still needs to maintain a low supply water temperature, resulting in long-term low-efficiency operation of the water chiller and energy waste.

[0003] At the same time, the fixed dew point control also has the problem of temperature and humidity coupling, and the cooling and dehumidifying capacity are mutually restricted, resulting in significant humidity deviation under different heat and humidity conditions. For example, under the condition of high sensible heat load and low wet load, the fixed low dew point supply air will cause excessive dehumidification, and the low-temperature dry air often needs to be reheated to meet the temperature requirement, forming the energy offset phenomenon of "cooling first and then heating", which seriously affects the comfort and energy efficiency.

[0004] In addition, the high-efficiency machine room cold source system generally adopts chilled water supply temperature resetting technology to improve the energy efficiency of the unit by dynamically increasing the supply water temperature. However, due to the fixed dew point control of the terminal all-air air conditioning system, if the supply water temperature is increased, the outlet temperature of the cooling coil cannot meet the fixed dew point supply air requirement, making it difficult to implement the chilled water temperature resetting technology, losing the core energy saving benefits, and forming the pain point of "incompatible energy saving technology". Moreover, in order to maintain the fixed dew point temperature, the system must continuously provide chilled water at a lower temperature, limiting the application of key energy saving strategies such as chilled water temperature resetting, resulting in long-term operation of the chiller unit in the low evaporation temperature region, low efficiency, low system seasonal performance coefficient, and significant energy waste. Moreover, in the season with low outdoor air humidity, the fixed dew point control still requires the supply air to be processed to the design dew point temperature, and cannot intelligently judge and preferentially utilize outdoor fresh air for free dehumidification and cooling, missing the important opportunity to utilize natural cold source to reduce system energy consumption.

[0005] Therefore, it is of great technical significance and application value to develop a variable dew point control method for an all-air air conditioning system, which can realize temperature and humidity decoupling control, improve the energy efficiency of the cold source side, and maximize the utilization of natural cold source. SUMMARY

[0006] To solve the above technical problems, the present application provides the following technical solutions:

[0007] The present application provides a variable dew point control method for an all-air air conditioning system, which is based on a variable dew point control system, the system comprising an air conditioning unit and its piping system, a sensor detection unit, an actuator, and an intelligent controller.

[0008] The method comprises the following steps:

[0009] S1, parameter initialization: set the indoor target temperature, target relative humidity, upper limit value of carbon dioxide concentration, and allowable fluctuation range, and calculate the initial supply air temperature based on the design condition;

[0010] S2, system startup and stabilization: after the system is started, the supply air is performed at the initial supply air temperature or the temperature set based on the supply air temperature difference, and the fan is started and operated; after a predetermined time of stable operation, the return air temperature, return air humidity, cooling coil outlet supply air temperature, supply air temperature, and supply air humidity are collected by the sensor detection unit;

[0011] S3, dynamic adjustment of supply air dew point and control of chilled water valve: the intelligent controller compares the return air humidity with the target humidity and the allowable fluctuation range, adjusts the cooling coil outlet supply air set temperature, and adjusts the opening degree of the air conditioning chilled water valve actuator;

[0012] S4, temperature and supply air volume control: dynamically adjust the fan frequency to control the supply air volume according to the real-time monitoring data of the indoor temperature;

[0013] S5, fresh air optimization and damper control: based on the return air carbon dioxide concentration to optimize the fresh air volume and coordinate the control of fresh air valve, return air valve and exhaust air valve opening degree.

[0014] Further, in step S3, if the return air humidity exceeds the target humidity plus the upper limit of the allowable fluctuation, the cooling coil outlet supply air set temperature is reduced by a magnitude of Kx0.3℃; if the return air humidity is lower than the target humidity minus the lower limit of the allowable fluctuation, the cooling coil outlet supply air set temperature is increased by a magnitude of Kx0.5℃; if the return air humidity is within the allowable range, the cooling coil outlet supply air set temperature is maintained unchanged, wherein K is a regulation coefficient positively related to the absolute value of the difference between the return air humidity and the target humidity.

[0015] Further, in step S4, if the indoor temperature is higher than the indoor target temperature plus the allowable fluctuation range, the fan frequency is increased to increase the supply air volume; if the indoor temperature is lower than the indoor target temperature minus the allowable fluctuation range, the fan frequency is reduced to reduce the supply air volume.

[0016] Further, in step S5, if the return air carbon dioxide concentration exceeds the upper limit value of the carbon dioxide concentration, the fresh air valve opening degree is increased, and the return air valve and the exhaust air valve are coordinated to increase the fresh air volume; if the return air carbon dioxide concentration is lower than the upper limit value of the carbon dioxide concentration minus the allowable fluctuation range, the fresh air volume is reduced.

[0017] Further, the execution period of the supply air dew point dynamic adjustment in step S3 is set to 10-15 minutes.

[0018] Further, it further includes a feedforward control step: introducing outdoor temperature and fresh air enthalpy value as feedforward signals, when the outdoor temperature or enthalpy value continuously rises, the opening degree of the air conditioning cold water valve actuator is increased in advance; when the outdoor temperature or enthalpy value continuously decreases, the opening degree is reduced in advance.

[0019] Further, it further includes a supply air temperature protection step: setting a lower limit value of the supply air temperature, which is not lower than the design working condition supply air temperature.

[0020] Further, it further includes a fan frequency protection step: setting a lower limit value of the fan frequency converter.

[0021] Further, it further includes step S6, data recording and adaptive optimization: after the system runs stably, the system automatically collects the current outdoor temperature and humidity, return air parameters and corresponding supply air dew point temperature, and stores them into a historical database; through a similar working condition matching algorithm, the relevance of the current running condition and the historical data is identified, the optimal control parameter initial value is dynamically called, and then fine tuning is performed in combination with real-time feedback.

[0022] Further, it also includes judging whether to update the control parameters in the historical database according to the set threshold; if the current energy efficiency improvement exceeds the preset reference or the indoor temperature and humidity deviation continuously decreases, the current operation data is marked as an optimization sample for subsequent policy iteration.

[0023] In order to further balance energy consumption and indoor comfort, the present application further provides a variable dew point control method for a full-air air conditioning system, wherein the air conditioning system serves multiple zones, and each zone is provided with an electric reheating device; the method comprises the following steps:

[0024] S1, parameter initialization: setting the indoor target temperature of each zone, the unified target relative humidity, the upper limit value of carbon dioxide concentration and the allowable fluctuation range; comparing the indoor target temperatures of each zone, selecting the lowest value as the unified air supply reference temperature of the air conditioning unit, and calculating the initial air supply temperature;

[0025] S2, system startup and stabilization: after the system is started, air supply is carried out at the initial air supply temperature, and the fan is started to run; after a preset time of stable operation, the return air temperature, return air humidity, supply air temperature and supply air humidity are collected;

[0026] S3, dynamic adjustment of supply air dew point and control of cold water valve: the intelligent controller compares the return air humidity with the target humidity and the allowable fluctuation range, adjusts the outlet supply air set temperature of the cooling coil, and adjusts the opening degree of the air conditioning cold water valve actuator;

[0027] S4, zone temperature control: comprising the following sub-steps:

[0028] S41, reference air supply temperature determination: comparing the target temperatures of each zone in real time, and selecting the lowest value as the current unified air supply reference temperature;

[0029] S42, zone electric reheating adjustment: for the zone whose required supply air temperature is higher than the unified air supply reference temperature, adjusting the power of the zone electric reheating device according to the deviation of the indoor temperature and the target temperature;

[0030] S5, temperature and air supply amount control: dynamically adjusting the fan frequency to control the air supply amount according to the real-time monitoring data of the indoor temperature;

[0031] S6, fresh air optimization and air valve control: optimizing the fresh air amount based on the return air carbon dioxide concentration and cooperatively controlling the opening degrees of the fresh air valve, return air valve and exhaust air valve.

[0032] Further, in step S42, the specific method of the zone electric reheating adjustment is:

[0033] calculating the temperature deviation of the zone;

[0034] If the temperature deviation is lower than the lower limit of the allowed fluctuation range of the target temperature, the power of the partition electric reheating device is proportionally increased, wherein the increase proportion is positively correlated with the absolute value of the temperature deviation of each partition;

[0035] If the temperature deviation is higher than the upper limit of the allowed fluctuation range of the target temperature, the power of the partition electric reheating device is reduced or turned off.

[0036] If the temperature deviation is within the allowed fluctuation range of the target temperature, the current electric reheating power is maintained.

[0037] Further, step S4 further comprises:

[0038] S43, cooperative control with the main system: when the power of the electric reheating device of a certain partition continuously exceeds the high power threshold and the temperature deviation is still lower than the lower limit of the allowed fluctuation range, the intelligent controller triggers the upward adjustment of the unified air supply reference temperature; when the power of the electric reheating device of most partitions continuously is lower than a low power threshold, the intelligent controller triggers the downward adjustment of the unified air supply reference temperature.

[0039] Further, step S3, dynamic adjustment of the air supply dew point and control of the cold water valve, further comprises the following steps: estimating the standard heat radiation intensity in the partition according to the number of people in the partition to obtain a preset standard value of the heat radiation intensity, and calculating the preset standard value of the electric current flow according to the rated power of the equipment and the estimated use frequency.

[0040] Comparing the heat radiation intensity data obtained by the partition infrared people number sensor with the preset standard value to obtain a comparison coefficient P1, and obtaining a comparison coefficient P2 by comparing the measured electric current flow with the preset standard value. A final revision coefficient P is obtained according to P1 and P2, which is used to dynamically correct the dew point setting value; wherein P=P1*P2.

[0041] Further, when P>1, the regional heat load is higher than expected, at this time the system increases the air supply setting temperature at the outlet of the surface cooler, which can be selected to increase by 0.5-1℃.

[0042] When P<1, the air supply setting temperature at the outlet of the surface cooler is correspondingly reduced, which can be selected to reduce by 0.5-1℃.

[0043] The present application can at least achieve one of the following beneficial effects:

[0044] (1) The step of dynamic adjustment of the air supply dew point solves the problem of temperature and humidity coupling, dynamically adjusts the dehumidification intensity through humidity feedback, avoids excessive dehumidification or insufficient dehumidification, and adjusts the supply water temperature through dynamic upward adjustment of the surface cooler outlet temperature, significantly improves the unit energy efficiency, and is suitable for the cold water temperature reset technology, and compatible with the application of medium temperature water supply technology.

[0045] (2) Through the construction of control strategy database, when the system faces similar working conditions again, the controller can quickly match the optimal control parameters based on the database to realize adaptive adjustment. Through long-term accumulation and learning, the system gradually adapts to the actual load characteristics of the building and the climate trend, significantly improves the operation efficiency, significantly reduces the debugging cost, and improves the long-term operation stability.

[0046] (3) Through dynamic adjustment of the supply air dew point and accurate partition reheating control, the system maximizes the reduction of energy waste caused by cold and heat offset while meeting the thermal and humid demands of each area; based on the real-time feedback and deviation driven collaborative regulation mechanism, the stability of environmental comfort is improved. Moreover, the adjustment of electric reheating only acts on the branch air supply, which does not affect the unified supply air reference temperature and dew point control logic of the air conditioning unit, ensuring that the main system can still realize efficient dehumidification and cold source optimization through variable dew point.

[0047] (4) Based on the real-time thermal load estimation results of personnel and equipment, the set value of the set temperature of the cooling coil outlet supply air is dynamically adjusted to avoid excessive dehumidification and waste of cold energy, realizing precise humidity regulation driven by load prediction, and improving the system energy efficiency on the premise of ensuring comfort.

[0048] In the present application, the above technical solutions can be combined with each other to realize more preferred combination schemes. Other features and advantages of the present application will be described in the subsequent content, and some advantages will become apparent from the description or by implementing the present application. The purpose and other advantages of the present application can be achieved and obtained by the content specifically pointed out in the text and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0049] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings: BRIEF DESCRIPTION OF DRAWINGS

[0050] Figure 1 It is a whole structure schematic diagram of the variable dew point supply air control system of the all-air air conditioning system in the embodiment one of the present application;

[0051] Figure 2 It is a flow chart of the variable dew point supply air control method of the all-air air conditioning system in the embodiment one of the present application;

[0052] Figure 3 It is a whole structure schematic diagram of the variable dew point supply air control system of the all-air air conditioning system with partition in the embodiment three and the embodiment four of the present application;

[0053] Figure 4 It is a flow chart of the variable dew point supply air control method of the all-air air conditioning system in the embodiment three of the present application.

[0054] The reference signs are as follows:

[0055] 1, fresh air inlet; 2, coarse filter section; 3, return air inlet; 4, mixed air section; 5, medium filter section; 6, surface cooling section; 7, fan section; 8, main air supply pipe; 9, air supply branch pipe; 10, indoor temperature and humidity sensor; 11, outdoor temperature and humidity sensor; 12, return air parameter sensor; 13, surface cooler outlet temperature sensor; 14, air supply parameter sensor; 15, differential pressure sensor; 16, static pressure sensor; 17, fan frequency converter; 18, air conditioning cold water valve actuator; 19, fresh air valve; 20, return air valve; 21, electric reheating device; 22, infrared people counting sensor. DETAILED DESCRIPTION

[0056] Example 1

[0057] The present application provides a variable dew point control method for a full-air air conditioning system, which is based on a variable dew point control system. Specifically, as shown in Figure 1 the variable dew point control system includes an air conditioning unit and its piping system, a sensor detection unit, an actuator, and an intelligent controller. The piping system includes a fresh air inlet 1, a coarse filter section 2, a return air inlet 3, a mixed air section 4, a medium filter section 5, a surface cooling section 6, a fan section 7, a main air supply pipe 8, and an air supply branch pipe 9. During operation, outdoor air (OA) enters the system through the fresh air inlet 1, is purified by the coarse filter section 2, and is fully mixed with indoor return air (RA) from the return air inlet 3 in the mixed air section 4 to form mixed air. The mixed air passes through the medium filter section 5 and the surface cooling section 6 in sequence, and is subjected to heat and humidity treatment in the surface cooling section 6 by chilled water. The treatment state is determined by the chilled water temperature and the heat exchange efficiency. The fan section 7 delivers the treated air to the use area through the main air supply pipe 8 and the air supply branch pipe 9.

[0058] Specifically, the coarse filter section 2 is mainly used to remove large-particle pollutants from outdoor air to ensure the cleanliness of the system. The medium filter section 5 further filters out fine particles to ensure the quality of the air supply. The mixed air section 4 is responsible for uniformly mixing fresh air and return air in a set proportion to avoid air flow short circuiting or local overheating and overhumidification, ensuring the stability and accuracy of subsequent heat and humidity treatment. The surface cooling section 6 dynamically controls the cooling and dehumidification of air by adjusting the chilled water flow or valve opening, achieving flexible regulation of the air supply state point. The fan section 7 provides sufficient air flow power to ensure that the treated air can be stably delivered to the air supply area, thereby ensuring the reliability of the overall system operation and the uniformity of the air supply. The main air supply pipe 8 precisely distributes the air supply (SA) to each use area through a variable air volume terminal device.

[0059] The sensor detection unit comprises an outdoor temperature and humidity sensor 11, an indoor temperature and humidity sensor 10, a return air parameter sensor 12 and a supply air parameter sensor 14. The outdoor temperature and humidity sensor 11 is used to monitor the outdoor air temperature T0 and relative humidity The indoor temperature and humidity sensor 10 is arranged in the use area and is used to monitor the indoor air temperature T n and relative humidity The return air parameter sensor 12 is used to collect the return air temperature T h , return air relative humidity and carbon dioxide concentration C h in the return air; the cooling coil outlet temperature sensor 13 is located behind the cooling coil in the air conditioning unit and is used to measure the cooling coil outlet supply air temperature T sc ; the supply air parameter sensor 14 is arranged in the supply air duct and is used to measure the air conditioning unit supply air temperature T s and supply air relative humidity

[0060] In addition, the coarse filter section 2 and the medium filter section 5 are respectively provided with differential pressure sensors 15 for monitoring the filter screen blockage in real time and issuing a replacement alarm when the resistance exceeds the standard, so as to ensure long-term high-efficiency operation of the system; the static pressure sensor 16 is arranged in the main supply air duct 8 and is used to feed back the air duct pressure change, cooperate with the variable frequency fan to adjust the air volume output and maintain the stable supply air.

[0061] The actuator at least comprises a fan frequency converter 17, an air conditioning cold water valve actuator 18, a fresh air valve 19, a return air valve 20 and an exhaust air valve actuator. The fan frequency converter 17 is arranged in the fan section 7 and adjusts the motor speed through the frequency converter to realize continuous and accurate control of the air volume to adapt to the load change under different working conditions; the air conditioning cold water valve actuator 18 dynamically adjusts the refrigerated water flow according to the deviation of the cooling section 6 outlet air temperature from the set value to ensure the heat and humidity treatment accuracy; the fresh air valve 19, the return air valve 20 and the exhaust air valve actuator cooperate to adjust the opening degree of each air valve according to the indoor and outdoor air quality and temperature and humidity parameters, maintain the stable air mixing ratio, and optimize the energy consumption and ventilation efficiency.

[0062] The intelligent controller is configured to receive all sensor signals and output control instructions to each actuator after preset logic operation. The control logic comprises steps of supply air dew point dynamic adjustment, temperature and supply air volume control, fresh air optimization and air valve control, so as to ensure the stable operation and high energy efficiency of the system under different working conditions.

[0063] As shown in Figure 2 , the variable dew point control method provided by the application comprises the following specific steps:

[0064] S1, parameter initialization: set the indoor target temperature T n_set , target relative humidity and upper limit value of carbon dioxide concentration Cmax and the allowable fluctuation range; calculate the initial supply air temperature T s_ini .

[0065] In this embodiment, the indoor target temperature T n_set is set to 24℃, the target relative humidity is set to 50%, the upper limit of carbon dioxide concentration C max is set to 800ppm, and the allowable fluctuation range of humidity, temperature and carbon dioxide concentration is set to ±5%, ΔT is ±1℃, and ΔC is 100ppm. The initial supply air temperature T s_ini is calculated based on the design condition to be 16℃, and the supply air temperature T sc and the supply air relative humidity at the outlet of the cooling coil are monitored in real time by the outlet temperature sensor of the cooling coil.

[0066] This step ensures that the system has a clear control target and reference parameter, laying the foundation for subsequent dynamic control.

[0067] S2, system startup and stabilization: when the system starts, the initial supply air is performed at T s_ini , and in addition, the supply air temperature difference can also be selected to perform the initial supply air, for example, the temperature difference can be set to 5℃; the fan runs at the power frequency. After the pre-set time of stable operation, for example, after running for 10 minutes, the return air temperature T h , the return air humidity , the supply air temperature T sc at the outlet of the cooling coil, the supply air temperature T s and the humidity are collected.

[0068] S3, dynamic adjustment of supply air dew point and control of cold water valve: the intelligent controller compares the return air humidity with the target humidity and the allowable fluctuation range, adjusts the supply air set temperature at the outlet of the cooling coil, and adjusts the opening degree of the air conditioning cold water valve actuator;

[0069] Specifically, if the return air humidity exceeds the target humidity plus the allowable fluctuation upper limit , the supply air set temperature T sc_set at the outlet of the cooling coil is reduced by the amplitude K×0.3℃. If is lower than , T sc_set is increased by the amplitude K×0.5℃; if is within the allowable range, T sc_set remains unchanged.

[0070] Wherein, K is a regulation coefficient positively related to the humidity deviation, the larger the K value, the stronger the regulation strength;

[0071] Adjusting the opening of the cold water valve to make the outlet air temperature T sc Reaching T sc_set .

[0072] The air supply dew point dynamic adjustment is the core step of the present application, which solves the temperature and humidity coupling problem through the step of air supply dew point dynamic adjustment, dynamically adjusts the dehumidification intensity through humidity feedback, avoids excessive dehumidification or insufficient dehumidification, and adjusts the supply water temperature through dynamic adjustment of the outlet temperature of the cooling coil, significantly improves the energy efficiency of the unit, and is suitable for the chilled water temperature reset technology, and compatible with the application of medium temperature water supply technology.

[0073] S4, temperature and air supply amount control: dynamically adjusting the frequency of the fan according to real-time monitoring data of indoor temperature to control the air supply amount;

[0074] Specifically, if the indoor temperature T n is higher than T n_set + ΔT, the frequency of the fan is increased to increase the air supply amount; if T n is lower than T n_set - ΔT, the frequency of the fan is reduced to reduce the air supply amount. This step realizes accurate temperature control and decouples from humidity control, ensuring that the indoor environment temperature always remains within the comfortable range.

[0075] S5, fresh air optimization and air valve control: optimizing the fresh air amount based on the return air carbon dioxide concentration and cooperatively controlling the opening of the fresh air valve, return air valve and exhaust air valve;

[0076] Specifically, if the return air carbon dioxide concentration C h exceeds the upper limit value C max of the carbon dioxide concentration, the opening of the fresh air valve is increased, and the return air valve and the exhaust air valve are cooperatively controlled to increase the fresh air amount; if the return air carbon dioxide concentration C h is lower than C max - ΔC, the fresh air amount is reduced.

[0077] Specifically, the upper limit value C max of the carbon dioxide concentration is 800 ppm, and ΔC is 100 ppm, at this time, the intelligent controller monitors the return air carbon dioxide concentration C h through the return air parameter sensor and makes a judgment. If C h is 900 ppm, which is higher than the set upper limit value C max of the carbon dioxide concentration of 800 ppm, the opening of the fresh air valve is increased, and the return air valve and the exhaust air valve are cooperatively controlled to increase the fresh air amount. Conversely, if C h is 600 ppm, and the lower limit value C max - ΔC is set to 700 ppm, C h is lower than C max- AC, thus reducing the fresh air volume.

[0078] Further, if in the transition season, when the outdoor air enthalpy is lower than the indoor air enthalpy, the system preferentially adopts the maximum fresh air ratio or even full fresh air operation, using outdoor low-temperature and low-humidity air for free cooling and dehumidification. This significantly reduces the energy consumption of the refrigeration unit and fully utilizes the natural cold source.

[0079] Further, in order to avoid frequent disturbances leading to system oscillation, the set supply air temperature adjustment period can be set to 10-15 minutes;

[0080] Further, before step S3, the outdoor temperature and fresh air enthalpy can also be introduced as a feedforward signal to correct the water valve control, that is, when the outdoor temperature or enthalpy continues to rise, the load is predicted to increase, and the water valve opening is increased in advance; otherwise, it is reduced in advance.

[0081] In addition, a lower limit of the supply air temperature protection can be set, and the lower limit temperature is not lower than the design working condition supply air temperature, and a lower limit of the fan frequency protection is preferably not lower than 25Hz, thereby ensuring the safe operation of the system.

[0082] Example two:

[0083] On the basis of example one, the intelligent controller in this embodiment further includes a historical operation data recording module for continuously recording the optimal supply air dew point temperature under different outdoor weather conditions and indoor loads, forming a control strategy database. When the system faces similar working conditions again, the controller can quickly match the optimal control parameters based on the database to realize adaptive adjustment.

[0084] The module analyzes historical data through machine learning algorithms, dynamically optimizes humidity and temperature control curves, and improves system response speed and energy efficiency. This method significantly reduces the debugging cost and improves the long-term operation stability. For example, when the historical data shows that the outdoor temperature is 22℃ and the relative humidity is 65%, the optimal supply air dew point temperature of the system is recorded as 13.5℃, and the controller will automatically call this parameter combination and adjust it in combination with the current return air temperature and humidity feedback. Under the condition of outdoor temperature of 30℃ and relative humidity of 60%, the optimal supply air dew point temperature is recorded as 12℃.

[0085] At this time, the corresponding variable dew point control method further includes steps S6, data recording and adaptive optimization: specifically, after the system runs stably, the system automatically collects the current outdoor temperature and humidity, return air parameters and corresponding supply air dew point temperature, and stores them in the historical database; through a similar condition matching algorithm, the relevance of the current operating condition and the historical data is identified, the optimal control parameter initial value is dynamically called, and then it is fine-tuned in combination with real-time feedback. This process is continuously iterated, so that the control strategy is continuously optimized over time, improving energy efficiency and comfort, while reducing energy consumption fluctuations.

[0086] Specifically, the system can perform data sampling and strategy evaluation every 15 minutes or other set intervals, and determine whether to update the control parameters in the historical database according to the set threshold. If the current energy efficiency is improved by more than the preset benchmark or the indoor temperature and humidity deviation continues to decrease, the current operation data is marked as an optimized sample for subsequent strategy iteration.

[0087] Through long-term accumulation and learning, the system gradually adapts to the actual load characteristics of the building and the climate trend, significantly improving the operation efficiency. When the outdoor meteorological conditions are similar to a certain working condition in the historical database with a similarity of 85% or more, the controller automatically loads the corresponding dew point temperature set value as the initial instruction and starts the real-time feedback fine-tuning mechanism. At this time, the controller combines the real-time return air humidity deviation for proportional integral adjustment to ensure that the supply air dew point temperature dynamically approaches the optimal value. Based on the historical operation data in the control strategy database, the proportional and integral coefficients can be dynamically adjusted according to the temperature and humidity change rate, automatically adjusting the PID parameters to optimize the control accuracy. When the temperature and humidity change rate is high, the proportional coefficient is appropriately increased to speed up the response; when the change rate is low, the proportional coefficient is reduced to avoid excessive adjustment.

[0088] Embodiment Three:

[0089] On the basis of Embodiment One and Embodiment Two, in order to further balance energy consumption and indoor comfort, the control method of variable dew point is further optimized for multi-zone air conditioning systems in this embodiment.

[0090] Specifically, as shown in Figure 3 , for the supply air temperature control of multiple air conditioning areas, due to the differences in temperature and humidity load characteristics in the partitioned use areas, at this time, according to the specific number requirements of the partitioned areas, an independent supply air branch pipe is set up in each partitioned area, and the number of supply air branch pipes is multiple. Further, the actuator further includes an electric reheating device 21, and an independent electric reheating device 21 is installed on the supply air branch pipe 9 of each partitioned area, and the electric heating device can select an electric heating coil, and is matched with a power adjustment actuator, which supports 0-100% continuous adjustment, for secondary heating of the supply air of the supply air branch pipe 9, to realize independent and accurate regulation and control of the supply air temperature of each partition.

[0091] At this time, an independent indoor temperature and humidity sensor 10 needs to be set up in each partitioned area to detect the indoor temperature T ni and indoor humidity of each partition, where i = 1, 2,..., n, and n is the number of partitions.

[0092] At this time, as shown in Figure 4 , for this embodiment, the variable dew point control method includes the following steps:

[0093] S1, parameter initialization: set the indoor target temperature T of each zone ni_set , target relative humidity , upper limit value C of carbon dioxide concentration max , and allowable fluctuation range; among the indoor target temperatures T of each zone ni_set , the lowest value is selected as the unified supply air reference temperature T of the air conditioning unit s_base , and the initial supply air temperature T is calculated based on the unified supply air reference temperature T s_base design condition s_ini .

[0094] S2, system startup and stabilization: when the system starts, the initial supply air is performed at T s_ini , in addition, the supply air temperature difference can also be selected to perform the initial supply air, for example, the temperature difference can be set to 5°C; the fan operates at the power frequency. After the preset time of stable operation, for example, after 10 minutes of operation, the return air temperature T h , return air humidity , supply air temperature T s , and humidity

[0095] S3, dynamic adjustment of supply air dew point and control of cold water valve: dynamic adjustment of supply air dew point and control of cold water valve: the intelligent controller compares the return air humidity with the target humidity and the allowable fluctuation range, adjusts the table cooler outlet supply air set temperature, and adjusts the opening degree of the air conditioning cold water valve actuator;

[0096] Specifically, if the return air humidity is higher than the target humidity plus the allowable fluctuation upper limit , the table cooler outlet supply air set temperature T sc_set is reduced by the amplitude Kx0.3°C. If the return air humidity is lower than , the table cooler outlet supply air set temperature T sc_set is increased by the amplitude Kx0.5°C; if the return air humidity is within the allowable range, T sc_set remains unchanged.

[0097] Among them, K is a regulation coefficient positively related to , specifically, Among them, a is a working condition regulation coefficient, the specific value can be determined according to the actual design condition, and specifically can be selected as 0.5-1.5, so that the greater the humidity deviation, the higher the K value, and the stronger the regulation strength;

[0098] The opening degree of the cold water valve is adjusted so that the table cooler outlet supply air temperature T sc reaches T sc_set .

[0099] S4. The steps for zoned temperature control include the following specific steps:

[0100] S41. Determination of reference supply air temperature:

[0101] The control system compares the indoor target temperature T in each zone in real time. ni_set The requirements are as follows, and the lowest value among them is selected as the unified supply air reference temperature T for the air conditioning unit. s_base This unified air supply reference temperature T s_base The set temperature T of the supply air at the outlet of the surface cooler sc_set The control objective is to unify the supply air reference temperature T. s_base This ensures that the supply air temperature requirements of the zones with the most stringent temperature control needs are met, while reserving space for electric reheat control in other zones.

[0102] S42, Zoned Electric Reheat Regulation:

[0103] For indoor target temperature T ni_set Required supply air temperature T s Higher than the unified supply air reference temperature T s_base Zone i: Real-time calculation of indoor temperature T in zone i ni With target temperature T ni_set deviation ΔT i =T ni -T ni_set ;

[0104] If the deviation ΔT i If the temperature deviation is less than or equal to ΔT, meaning the deviation is below the lower limit of the allowable fluctuation range of the target temperature, then the power of the electric reheat actuator for that zone is increased proportionally. This zone's electric reheat actuator uses PID control, and the proportional coefficient is related to |ΔT|. i | Shows a positive correlation, increasing indoor temperature through heated branch pipes for air supply;

[0105] If the deviation ΔT i If the temperature deviation is greater than +ΔT, meaning the deviation is higher than the upper limit of the allowable fluctuation range of the target temperature, then the electric reheat power is reduced to a minimum of 0%, and the indoor temperature is lowered by using the reference low temperature air supply.

[0106] If the deviation ΔT i If the temperature deviation is within the allowable range, meaning the deviation is within the allowable fluctuation range of the target temperature, then maintain the current electric reheat power.

[0107] By dynamically adjusting the supply air dew point and accurate zoned reheating control, the system maximizes the reduction of energy waste caused by cold and heat offset while meeting the thermal and moisture demand of each zone; the collaborative control mechanism based on real-time feedback and deviation driving improves the stability of environmental comfort. And since the regulation of electric reheating only affects the branch air supply, it does not affect the uniform air supply reference temperature T s_base and dew point control logic, ensuring that the main system can still achieve efficient dehumidification and cold source optimization through variable dew point;

[0108] Further, step S4 also includes S43, cooperative control with the main system: when a zone continuously runs at high power due to electric reheating, such as exceeding 80% of the rated power, and ΔT i is still <-ΔT, the system determines that the deviation of the zone from the reference air supply temperature is too large, triggering the adaptive upward adjustment of the uniform air supply reference temperature T s_base , with an adjustment amplitude ≤1℃ / time to avoid excessive energy consumption of electric reheating; on the contrary, if the electric reheating power of most zones is less than 20% for a long time, such as more than 60% of the zones having electric reheating power less than 20% of the rated power, the system will lower the uniform air supply reference temperature T s_base by ≤0.5℃ / time, thereby improving the refrigeration efficiency of the main system.

[0109] S5, temperature and air supply control: dynamically adjust the fan frequency to control the air supply according to real-time indoor temperature monitoring data; specifically, if the indoor temperature T ni is higher than the indoor target temperature T ni_set +ΔT, increase the fan frequency to increase the air supply; if the indoor temperature T ni is lower than the indoor target temperature T ni_set -ΔT, reduce the fan frequency to reduce the air supply. This step realizes accurate temperature control and decouples humidity control, ensuring that the indoor environment temperature always remains within the comfortable range.

[0110] S6, fresh air optimization and damper control: optimize the fresh air volume based on the return air carbon dioxide concentration and cooperatively control the new air valve, return air valve and exhaust air valve opening; specifically, if the return air carbon dioxide concentration C h exceeds C max , increase the new air valve opening while cooperatively controlling the return air valve and exhaust air valve to increase the fresh air volume; if C h is lower than C max -ΔC, reduce the fresh air volume.

[0111] Embodiment Four

[0112] On the basis of Embodiments One to Three, the current basis for dynamic dew point adjustment is based on the return air temperature T h , return air humidity monitoring data. To further improve the accuracy of the dew point selection, the embodiment also includes a step of estimating and correcting the heat of the personnel and equipment by the sensor.

[0113] As shown in Figure 3 , the sensor detection unit also includes a partition infrared people sensor 22 and an electric current monitoring sensor for real-time collection of the thermal radiation intensity of personnel activities in each partition and the equipment operating current value. Therefore, it can be determined whether to adjust the dew point by comparing the thermal radiation intensity and the electric current.

[0114] Specifically, the variable dew point control method S3, air supply dew point dynamic adjustment and cold water valve control, further includes the following steps: estimating the standard thermal radiation intensity in the partition according to the number of personnel in the partition, obtaining the preset standard value of the thermal radiation intensity; calculating the preset standard value of the electric current according to the rated power of the equipment and the estimated usage frequency.

[0115] The thermal radiation intensity data obtained by the partition infrared people sensor is compared with the preset standard value to obtain a comparison coefficient P1, and the comparison coefficient P2 is obtained by comparing the measured electric current with the preset standard value. The final revision coefficient P is obtained according to P1 and P2, which is used to dynamically correct the dew point setting value, wherein P = P1 x P2.

[0116] When P > 1, the regional heat load is higher than expected, at which time the system increases T sc_set , which can be selected to increase by 0.5-1℃.

[0117] When P < 1, the corresponding T sc_set , which can be selected to decrease by 0.5-1℃. The correction mechanism cooperates with the partition reheating to further improve the accuracy of temperature and humidity control and the energy efficiency balance.

[0118] Based on the real-time heat load estimation results of personnel and equipment, the set value of the cooling coil outlet air supply set temperature T sc_set is dynamically adjusted. When the personnel density or equipment heat generation of a certain partition significantly increases, the system adaptively increases the air supply dew point control target of the region to avoid excessive dehumidification and waste of cold energy. This method realizes precise humidity regulation driven by load prediction, and improves system energy efficiency on the premise of ensuring comfort.

[0119] The above is only the preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application.

Claims

1. A method for controlling the dew point of an all-air air conditioning system, characterized in that, This method is based on a variable dew point control system, which includes an air conditioning unit and its piping system, a sensor detection unit, an actuator, and an intelligent controller; the method includes the following steps: S1. Parameter initialization: Set the target indoor temperature, target relative humidity, upper limit of carbon dioxide concentration and allowable fluctuation range, and calculate the initial supply air temperature based on the design conditions; S2. System Start-up and Stabilization: After the system starts up, it supplies air at the initial supply air temperature or the temperature set based on the supply air temperature difference, and the fan starts running. After stabilizing for a preset time, the return air temperature, return air humidity, surface cooler outlet supply air temperature, supply air temperature and supply air humidity are collected by the sensor detection unit. S3. Dynamic adjustment of supply air dew point and control of chilled water valve: The intelligent controller compares the return air humidity with the target humidity and the allowable fluctuation range, adjusts the set temperature of the supply air at the outlet of the surface cooler, and adjusts the opening of the air conditioning chilled water valve actuator. S4. Temperature and air volume control: The fan frequency is dynamically adjusted to control the air volume based on real-time indoor temperature monitoring data. S5. Fresh air optimization and damper control: Optimize fresh air volume based on return air carbon dioxide concentration and coordinate the opening of fresh air valve, return air valve and exhaust valve.

2. The method for controlling the dew point of an all-air air conditioning system according to claim 1, characterized in that, In step S3, if the return air humidity exceeds the target humidity plus the upper limit of allowable fluctuation, the outlet air supply temperature of the surface cooler is reduced by an amount of K × 0.3℃; if the return air humidity is lower than the target humidity minus the lower limit of allowable fluctuation, the outlet air supply temperature of the surface cooler is increased by an amount of K × 0.5℃; if the return air humidity is within the allowable range, the outlet air supply temperature of the surface cooler is kept unchanged, where K is an adjustment coefficient that is positively correlated with the absolute value of the difference between the return air humidity and the target humidity.

3. The method for controlling the dew point of an all-air air conditioning system according to claim 2, characterized in that, In step S4, if the indoor temperature is higher than the indoor target temperature plus the allowable fluctuation range, the fan frequency is increased to increase the air supply volume; if the indoor temperature is lower than the indoor target temperature minus the allowable fluctuation range, the fan frequency is decreased to reduce the air supply volume.

4. The method for controlling the dew point of an all-air air conditioning system according to claim 1, characterized in that, In step S5, if the return air carbon dioxide concentration exceeds the upper limit of carbon dioxide concentration, the opening of the fresh air valve is increased, and the return air valve and exhaust air valve are controlled in a coordinated manner to increase the fresh air volume; if the return air carbon dioxide concentration is lower than the upper limit of carbon dioxide concentration minus the allowable fluctuation range, the fresh air volume is reduced.

5. The method for controlling the dew point of an all-air air conditioning system according to claim 1, characterized in that, In step S3, the execution cycle for the dynamic adjustment of the supply air dew point is set to 10-15 minutes.

6. The method for controlling the dew point of an all-air air conditioning system according to claim 1, characterized in that, Before step S3, a feedforward control step is also included: the outdoor temperature and the enthalpy of the fresh air are introduced as feedforward signals. When the outdoor temperature or enthalpy continues to rise, the opening of the air conditioning chilled water valve actuator is increased in advance; when the outdoor temperature or enthalpy continues to fall, the opening is decreased in advance.

7. The method for controlling the dew point of an all-air air conditioning system according to claim 1, characterized in that, It also includes a supply air temperature protection step: setting a lower limit value for the supply air temperature, which is not lower than the supply air temperature under design conditions.

8. The method for controlling the dew point of an all-air air conditioning system according to claim 1, characterized in that, It also includes a fan frequency protection step: setting the lower limit value of the fan frequency converter's frequency.

9. The method for controlling the dew point of an all-air air conditioning system according to any one of claims 1 to 8, characterized in that, It also includes step S6, data recording, and adaptive optimization: After the system is running stably, the system automatically collects the current outdoor temperature and humidity, return air parameters, and corresponding supply air dew point temperature, and stores them in the historical database; through a similar operating condition matching algorithm, it identifies the correlation between the current operating conditions and historical data, dynamically calls the optimal initial value of the control parameters, and then makes fine adjustments in combination with real-time feedback.

10. The method for controlling the dew point of an all-air air conditioning system according to claim 9, characterized in that, It also includes determining whether to update the control parameters in the historical database based on a set threshold; if the current energy efficiency improvement exceeds the preset benchmark or the indoor temperature and humidity deviation continues to decrease, the current operation data will be marked as an optimization sample for subsequent strategy iterations.

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