A composite heat exchange air conditioning fresh air system with temperature and humidity independent control

Abstract

The present application belongs to air conditioning technical field, disclose a kind of temperature and humidity independent control's composite heat exchange air conditioning fresh air system, comprising: each return air branch pipe imports total pipe before collecting temperature and humidity data, to calculate the net sensible heat load and net latent heat load of system, and according to this decoupled load information differentiation control physical separation heat exchange coil;System also calculates the acceleration of latent heat load variation, when the acceleration reaches the determination value, then compare the absolute moisture content of indoor and outdoor air, then execute the instantaneous disturbance suppression operation of increasing fresh air dilution or turning into internal circulation strong dehumidification, the present application is decoded to un-mixed load information before energy processing, and energy is accurately distributed to the load type dominated as needed, thereby avoid structural overcooling and invalid reheating caused by unknown load nature, and the disturbance suppression mechanism based on load acceleration and indoor and outdoor humidity comparison is used to avoid decision-making error in extreme weather.

Description

TECHNICAL FIELD

[0001] The present application relates to a kind of composite heat exchange air conditioning fresh air systems of temperature and humidity independent control, belong to air conditioning technical field. BACKGROUND

[0002] In the current air conditioning and ventilation engineering practice, for the system needing to handle fresh air and return air centrally, a commonly used technical method is to first physically collect return air streams carrying different temperature and humidity loads from different functional areas, and fully mix with the introduced fresh air in the mixing box, and then send the airflow whose temperature and humidity has been averaged to a unified air handling unit for centralized processing such as cooling and dehumidification. This operation architecture of mixing first and then processing has been widely recognized and widely applied in the industry in terms of convenience of system design and operation management, because it can simplify the system control model and convert complex multivariable indoor loads into a single centralized processing object.

[0003] However, when dealing with dynamic and non-uniform load changes in modern buildings, the inherent cost or technical limitations of the above operation mode begin to appear. The sensible heat load and latent heat load generated by the activities of personnel, equipment operation, and changes in sunlight in each area of the building often change dramatically and asynchronously. Mixing the return air stream containing accurate information about the source and nature of the load first results in the loss of distribution information of indoor load. The system can only passively respond to the temperature and humidity signals of the airflow that has been averaged, and can only respond to the average signal that has been contaminated and blurred. The direct consequence is that the system has to adopt a lower uniform supply air temperature to cope with the possible highest load, which will cause excessive cooling and energy waste in areas with low latent heat load, and may not be able to effectively reduce humidity in areas with high latent heat load, resulting in a decline in indoor environmental quality. This information cost paid for the convenience of operation ultimately compensates for the long-term structural high energy consumption and low accuracy of the system.

[0004] To improve this situation, one intuitive idea is to try to optimize the mixed airflow processing link, such as using more advanced sensors or implementing more complex control algorithms, but these attempts are all patching under the premise that the information has been destroyed, no matter how complex the subsequent algorithm is, it cannot restore the distribution information about the real structure of the indoor load that has been erased by the physical averaging process; Another idea is to configure an independent air conditioning system for each independent area, but this will sharply increase the initial investment of the system, occupy a large amount of building space and make the maintenance work extremely complex, which is contrary to the original intention of central air conditioning system intensification, and thus there are practical obstacles in economy and scale application; Specifically, the existing technology mainly has the following deficiencies: 1. The system lacks a mechanism for separating and independently measuring the sensible heat and latent heat components of the total indoor load at the source of control decision, resulting in a lack of clear target orientation for energy distribution; 2. The temperature and humidity signals on which the control system is based are the results of physical mixing of multiple source loads, and their information value has been diluted, and they cannot truly reflect the instantaneous partition load state inside the building; 3. The output mode of energy is single and fixed, and cannot dynamically differentiate resource allocation between sensible heat treatment and latent heat treatment according to the dynamic changes of load properties. Therefore, how to establish a new system operation mode that can decode and separate the unphysically mixed temperature and humidity load information carried by the system before energy processing, and based on this, realize the targeted allocation of refrigeration resources to avoid energy waste, becomes a technical problem to be solved by the present application. SUMMARY

[0005] The present application provides a temperature and humidity independent control composite heat exchange air conditioning fresh air system, which mainly aims to solve the problem of how to accurately decode and separate the unphysically mixed temperature and humidity load information before energy processing without complex modification of the system hardware, and based on this, realize the predictive and targeted allocation of refrigeration resources.

[0006] To achieve the above purpose, the present application provides a temperature and humidity independent control composite heat exchange air conditioning fresh air system, which is applied to an air handling unit having a return air main pipe for collecting multiple return air branch pipe airflows, an adjustable fresh air and return air mixing device, and a first heat exchange coil and a second heat exchange coil, the system comprising a control module configured to perform the following operations:

[0007] Step a. In each control cycle, before the multiple return air branch pipes flow into the return air main pipe, the temperature and humidity data in each return air branch pipe are collected, and based on the temperature and humidity data and the weight factor corresponding to each return air branch pipe, the net sensible heat load and the net latent heat load carried by the current system are calculated and obtained;

[0008] Step b, based on the calculated sensible heat load and latent heat load, determine a cold distribution coefficient, and drive the first heat exchange coil and the second heat exchange coil to operate according to the cold distribution coefficient;

[0009] Step c, calculate the time-varying acceleration of the latent heat load, when the value of the time-varying acceleration reaches a disturbance determination threshold, execute a transient disturbance suppression procedure, which includes: collecting and comparing the absolute humidity of outdoor fresh air and the absolute humidity of indoor return air; if the absolute humidity of outdoor fresh air is lower than the absolute humidity of indoor return air, instruct the fresh air and return air mixing device to operate at the upper limit value of fresh air ratio for a first time length; if the absolute humidity of outdoor fresh air is not lower than the absolute humidity of indoor return air, instruct the fresh air and return air mixing device to operate at the lower limit value of fresh air ratio for a second time length, and instruct the refrigerant supply amount of the second heat exchange coil to increase.

[0010] Preferably, the control module is configured to calculate the time-varying acceleration of the latent heat load, specifically by: recording a sequence of values of the latent heat load within a calculation window composed of a plurality of consecutive control periods, and obtaining a quantitative value of the time-varying acceleration by performing a second-order difference operation on the sequence of values; the second-order difference operation follows: , wherein, is the quantitative value of the time-varying acceleration at the current time, is the value of the latent heat load at the current control period, and are the values of the latent heat load at the first and second preceding control periods, respectively.

[0011] Preferably, the control module is further configured to: update the fresh air ratio of the fresh air and return air mixing device according to the ratio of the sensible heat load and the latent heat load calculated in step a, on the premise that the indoor air quality meets the air quality standard; and after the transient disturbance suppression procedure is executed, the control module is configured to restore the fresh air ratio to the value determined by the aforementioned ratio.

[0012] Preferably, the first heat exchange coil is a pre-cooling coil, and the second heat exchange coil is a deep dehumidification coil; the control module is configured to drive the first heat exchange coil and the second heat exchange coil to operate according to the cold distribution coefficient, specifically by: adjusting the refrigerant flow through the pre-cooling coil and the deep dehumidification coil, and adjusting the refrigerant temperature supplied to the deep dehumidification coil.

[0013] Preferably, the air handling unit comprises at least a variable frequency fan; the control module is further configured to perform a self-diagnosis procedure of the health status of the system air path, which comprises: in the initial calibration stage of the system, collecting the working current waveform of the variable frequency fan under the calibration working condition, performing Fourier transform on the working current waveform, extracting the harmonic characteristic thereof, and establishing the harmonic characteristic as a set of reference harmonic characteristics and storing the same; during the operation of the system, periodically repeating the foregoing process to obtain real-time harmonic characteristics; calculating the deviation metric value between the real-time harmonic characteristics and the set of reference harmonic characteristics; when the numerical value of the deviation metric value continuously exceeds the maintenance judgment threshold value, generating and outputting maintenance warning information representing the progressive blockage of the system air path.

[0014] Preferably, the control module is configured to perform the self-diagnosis procedure of the health status of the system air path, which further comprises: performing high-pass filtering processing on the continuously collected variable frequency fan working current harmonic characteristic data stream to monitor whether the harmonic characteristic has a step change; recording all control instructions issued by the control module itself; when a step change in the harmonic characteristic is monitored and the control instructions recorded by the control module do not contain any instructions capable of causing a change in the system air resistance, it is determined that a physical air resistance mutation event has occurred in the system air path, and a corresponding fault alarm is generated.

[0015] Preferably, the system further comprises a variable frequency fan cooperating with the first heat exchange coil and the second heat exchange coil in the air handling unit; the control module is further configured to adjust the rotating speed of the variable frequency fan according to the relative proportion of the sensible heat load and the latent heat load calculated in step a.

[0016] Preferably, the control module is further configured to perform effectiveness verification on the temperature and humidity data collected in step a in each return air branch pipe; when it is determined that the sensor data of a certain return air branch pipe is invalid data, the control module is configured to exclude the invalid data from the current load calculation, and generate substitute data through an interpolation estimation algorithm according to the historical data associated with the return air branch pipe and the effective data of the remaining return air branch pipes collected at the same time, to complete the calculation.

[0017] Preferably, the weight factor corresponding to each return air branch pipe in step a is determined according to the design fresh air volume or the building area of the functional area corresponding to each return air branch pipe.

[0018] Preferably, the control module is configured to perform the instantaneous disturbance suppression procedure, and after the first time length or the second time length of the procedure ends, it is further configured to perform an exit judgment: continuously monitoring the time variation acceleration of the latent heat load until its numerical value falls below the disturbance judgment threshold value and maintains a stable time length, and then restoring the system to the operating state determined by the rules of step b.

[0019] Compared with the prior art, the present application has the following advantages:

[0020] 1、The present application establishes a system operation mode by collecting and analyzing the temperature and humidity data of each return air branch before it converges into the main pipe, then separating and calculating the current net sensible heat load and net latent heat load carried by the system, and differentially regulating the physically separated sensible heat and latent heat treatment units according to the decoupled load information. In this mode, the basis for control decision is no longer the single air flow state blurred by the averaged information after the return air is mixed, but is changed into the direct interpretation and response to the real-time generated and multi-dimensional load distribution thermodynamic map inside the building. The system thereby avoids performing refrigeration operation according to the general temperature signal, but allocates energy to the currently dominant load type as needed, so that the energy consumption link inherent in the traditional mode, such as excessive cooling or invalid reheating caused by unknown load nature, is no longer a problem to be considered in the operation process of the present application;

[0021] 2、The present application further extends the analysis of net latent heat load from the state and first-order trend level to the real-time calculation of its change acceleration, and uses an acceleration signal exceeding a preset threshold as a feedforward instruction to trigger the instantaneous disturbance suppression operation. After receiving this instruction, the system does not immediately start the energy consumption unit, but first compares and decides the absolute moisture content of indoor and outdoor air. When the outdoor air is drier, the dilution operation of increasing fresh air ratio is preferentially performed, otherwise the fresh air is immediately reduced to the minimum and the internal circulation dehumidification is activated. This response mechanism based on the pre-decision of the internal and external entropy difference makes the system have the ability to resolve the impact when facing sudden increase of personnel and other latent heat impact, and thereby avoids the risk of exacerbating indoor environmental deterioration due to the wrong introduction of higher humidity air in extreme weather such as wet fresh air.

[0022] 3、The present application also uses the harmonic characteristics of the working current of the variable frequency fan in the system as an information source, analyzes the health fingerprint steady-state drift in a long time scale to identify the gradually increasing state of system air resistance caused by filter or coil dust accumulation. At the same time, the system also high-pass filters the real-time data stream of this harmonic characteristic to capture any sudden stepwise transient jump, and cross-compares it with the instruction log issued by the controller itself. When a non-instructional jump occurs, it can be judged that there is a physical air resistance mutation event such as air valve jamming or accidental closing in the air path. This mechanism converts a signal that was originally considered as electrical noise into an internal sensing capability without additional hardware that can diagnose both chronic health decline and acute physical failure of the system, providing a warning based on the actual state for system maintenance, rather than relying on fixed time periods or additional sensors. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The logical architecture diagram for load decoupling control of the system of the present application.

[0024] Figure 2 Flow chart for off-line calibration of self-diagnosis and disturbance rejection procedure of the present invention.

[0025] Figure 3 Schematic diagram of physical components and control information flow of the present invention.

[0026] Figure 4 Timing diagram for dynamic control response based on load type of the present invention. DETAILED DESCRIPTION

[0027] In order to make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be described below in detail with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention. Based on the embodiments of the present invention, all the other embodiments obtained by a person of ordinary skill in the art without creative effort shall fall within the protection scope of the present invention.

[0028] The application discloses a composite heat exchange air conditioner fresh air system with independent temperature and humidity control, which is applied to a central air conditioning system provided with an air handling unit. The air handling unit comprises a return air branch pipe and a return air main pipe for collecting air flows of multiple functional areas in a building, a device for adjusting a mixing ratio of fresh air and return air, and a first heat exchange coil and a second heat exchange coil which are physically separated. The core of system operation is a control module which is configured to execute specific information processing and control logic, decodes each return air information before physical mixing of the return air, realizes separated calculation and target adjustment of the internal load of the building, and integrates adaptive procedures for sudden disturbance and system physical state. In a specific application scenario, such as a building comprising an open office area and multiple independent conference rooms, the sensible heat and latent heat loads of each area present the characteristics of non-uniform asynchronous change due to different personnel activities and equipment running states. The conventional post-mixing processing mode has the problem of reduced energy efficiency when dealing with such changes due to the loss of control information. To solve this challenge, the control module of the present application first collects the temperature and humidity data of each return air through the temperature and humidity sensors arranged in the return air branch pipes before the return air branch pipes flow into the return air main pipe in each control cycle. In order to reflect the different proportions of each functional area in the load composition, the system presets a weight factor for each return air branch pipe, and the value of the weight factor can be determined according to the designed fresh air volume or the building area of the corresponding functional area. The control module calculates the net sensible heat load and the net latent heat load value of the current system based on the collected temperature and humidity data of each return air and the corresponding weight factor. This separated calculation of load information before energy processing provides a quantitative decision basis for subsequent energy distribution. In order to ensure the continuity of the above load calculation process in actual operation, the system is configured to perform effectiveness verification on the collected temperature and humidity data of each return air branch pipe. The verification procedure is configured as follows: when it is determined that the sensor data of a return air branch pipe is invalid due to failure or communication interruption, for example, the reading is out of the preset physical reasonable range or has no change in multiple continuous cycles, the control module will exclude the invalid data from the current load calculation, and generate a replacement data through an interpolation estimation algorithm based on the stored historical data associated with the return air branch pipe and the data of the remaining effective return air branch pipes collected at the same time, to complete the load calculation, and send a corresponding maintenance alarm to the building automation system. The data verification and repair mechanism can provide continuous data input for load calculation under the condition of local sensor failure, thereby ensuring the stable operation of the main control logic.

[0029] After obtaining the separated sensible and latent heat load data, the system drives the physically separated first and second heat exchange coils to operate differently in order to allocate the cooling capacity according to the load properties. In this scheme, the first heat exchange coil is a pre-cooling coil, which mainly undertakes sensible heat treatment function, and the second heat exchange coil is a deep dehumidification coil, which mainly undertakes latent heat treatment function. The control module determines the cooling capacity allocation coefficient based on the relative size of the calculated sensible and latent heat loads, and drives the pre-cooling coil and the deep dehumidification coil to operate according to the coefficient. The driving methods include adjusting the refrigerant flow through the two coils, and adjusting the refrigerant temperature supplied to the deep dehumidification coil. For example, when the calculation result shows that the current main contradiction is high latent heat load, the cooling capacity allocation coefficient will instruct to supply more or lower temperature refrigerant to the deep dehumidification coil, while the cooling capacity supply of the pre-cooling coil is correspondingly weakened. Correspondingly, the control module can also adjust the frequency fan speed in the air handling unit according to the relative proportion of the calculated sensible and latent heat loads. For example, when dealing with high latent heat load, the air speed can be reduced to increase the contact time of air and the deep dehumidification coil, and to improve the dehumidification efficiency. In other words, under the premise of meeting the indoor air quality standard, the control module also adjusts the mixing ratio of fresh air and return air according to the proportion of sensible and latent heat loads. When the indoor latent heat load dominates, the fresh air ratio can be reduced and the internal circulation air volume can be increased to accelerate the processing of indoor accumulated moisture load.

[0030] When dealing with scenarios such as sudden increase of people in a conference room, the indoor latent heat load may show explosive growth. To deal with such nonlinear mutant load, the system is configured to execute a transient disturbance suppression procedure. The starting basis of this procedure is the time change acceleration of the net latent heat load. The control module records a sequence of values of the net latent heat load in a calculation window composed of a plurality of consecutive control cycles, and obtains a quantitative value of the time change acceleration by performing a second-order difference operation on the sequence , which follows: , where is the quantitative value of the time change acceleration at the current time, is the value of the net latent heat load in the current control cycle, and are the values of the net latent heat load in the first and second previous control cycles, respectively; when When the value of the time change acceleration of the net latent heat load reaches a disturbance determination threshold determined according to the building characteristics in the system debugging stage, the procedure is triggered, at which time the system first performs a feasibility decision, that is, the absolute humidity of the outdoor fresh air and the absolute humidity of the indoor return air are collected and compared; this decision step is used to avoid the risk of introducing fresh air to exacerbate the deterioration of the indoor environment in high-humidity outdoor weather; if the decision result is that the absolute humidity of the outdoor fresh air is lower than the indoor return air, the system instructs the fresh air and return air mixing device to run at the upper limit value of the fresh air ratio for a first time length; if the absolute humidity of the outdoor fresh air is not lower than the indoor return air, the system instructs the fresh air and return air mixing device to run at the lower limit value of the fresh air ratio for a second time length, and simultaneously increases the refrigerant supply amount of the second heat exchange coil; after the first time length or the second time length ends, the control module continues to monitor the time change acceleration of the net latent heat load until its value falls below the disturbance determination threshold and maintains a stable time length, and then the system is restored to the operating state determined by the conventional load ratio.

[0031] In addition, in order to realize the monitoring of the health state of the system air path, the present scheme uses the variable frequency fan in the air handling unit to perform a self-diagnosis procedure of the health state of the system air path without adding additional hardware sensors; the implementation manner is that the harmonic signal of the variable frequency fan working current is used as a kind of information source capable of reflecting the aerodynamic characteristics of the system air path; in the initial calibration stage of the system, the control module collects the working current waveform of the variable frequency fan under a set of calibration conditions, performs fast Fourier transform on the waveform data, extracts the amplitude distribution of the characteristic harmonics, and establishes the harmonic characteristics as a set of reference harmonic characteristics and stores them; during the subsequent operation of the system, the control module periodically repeats this process to obtain real-time harmonic characteristics, and quantifies the change trend of the system air resistance by calculating the deviation measure value between the real-time harmonic characteristics and the set of reference harmonic characteristics; when the value of the deviation measure value continuously exceeds a maintenance determination threshold, the control module generates and outputs maintenance warning information representing that the system air path has progressive blockage; at the same time, in order to capture sudden events such as accidental jamming of the air valve, the self-diagnosis procedure is further configured to perform high-pass filtering processing on the continuously collected variable frequency fan working current harmonic characteristic data stream to monitor whether the harmonic characteristics have a step change, and cross-compare with the instruction log issued by the control module itself; when a step change in the harmonic characteristics is monitored, and there is no instruction in the instruction log that can cause a corresponding change in the system air resistance, the system determines that a physical air resistance sudden event has occurred in the air path, and generates a corresponding fault alarm.

[0032] In this embodiment, the system is faced with a dynamic non-uniform load change condition at 3 pm on a summer weekday in a building comprising a large open office area, a 50-person large conference room and a 10-person small conference room. At this time, the meeting in the 10-person small conference room has ended and the participants have dispersed, while the 50-person large conference room is just starting a discussion with a high concentration of participants. Meanwhile, the personnel density and equipment operating status in the open office area remain stable. Under this condition, the return air streams from the three functional areas carry different types and trends of temperature and humidity loads. The load in the small conference room is decreasing, while the sensible heat and latent heat loads in the large conference room are rapidly increasing. The control module of the technical solution does not physically mix the return air from the three areas, but first performs the step of collecting temperature and humidity data of each return air before it enters the return air main. The control module analyzes the three un-mixed data streams and calculates the net latent heat load of the large conference room, which is higher than the net sensible heat load and both are increasing, while the load in the small conference room is lower and decreasing, and the load in the open office area remains stable. Based on this separated load data, the control module determines that the latent heat load contributed by the large conference room is the dominant part of the total load carried by the system, and then adjusts the cold distribution coefficient according to this judgment, directing the refrigerant supply to the second heat exchange coil for handling latent heat load, while maintaining a basic cold supply to the first heat exchange coil for handling sensible heat load. This operation process reflects the functional association between the load information collection and energy distribution technical features, i.e. separating the load information before mixing, providing quantitative decision basis for differentiated operation of physically separated heat exchange coils, and the separated coils providing a physical execution path for this targeted energy supply based on information.

[0033] This operation mode is different from the mode of uniformly reducing the temperature of the total supply air when dealing with non-uniform loads. In the working condition of this embodiment, since the cold is targeted for enhancing the operation of the deep dehumidification coil, the humidity of the system's supply air is effectively controlled without excessively reducing the temperature, thereby avoiding unnecessary cold input to the small conference room where the participants have dispersed and the open office area with stable load while meeting the dehumidification demand of the large conference room. The system distributes cold to the dominant load type based on the separated load calculation. Finally, in the dynamic process of asynchronous load changes in each area of the building, the system operates in a state where the environmental parameters in each functional area are maintained within the set range, and the total energy consumption corresponds to the real-time total load.

[0034] Example 2: To verify the operation effect of the technical solution in response to dynamic non-uniform load, an experimental platform including two identical environment simulation cabins is established, each simulation cabin is divided into three sub-regions where temperature and humidity load can be independently applied and monitored, to simulate the internal space of a building including a large conference room, a small conference room and an open office area; the experimental platform sets two sets of air conditioning systems, one set as a control group, which adopts an air treatment mode of physically mixing the return air of each region first and then centrally cooling by a single cooling coil; the other set as a test group, which follows the technical solution described in the foregoing specific embodiments in configuration and control logic; the specifications and performance parameters of the hardware devices such as fans and heat exchange coils of the two sets of systems are consistent to exclude the interference of hardware differences on the test results; the test adopts a dynamic load loading procedure with a total duration of 120 minutes, and the recording period of all temperature, humidity and energy consumption data is set to 1 minute, which is the result of balancing between ensuring the ability to capture minute-level load change trend and avoiding excessive data processing load of the control system; the test procedure is divided into three stages, 0 to 30 minutes as the initial stable stage, all regions maintain a low basic load; 30 to 90 minutes as the non-uniform load impact stage, the sensible heat and latent heat load of the large conference room region is increased to the peak value, while the load of the small conference room region is reduced to near zero, and the load of the open office area remains unchanged; 90 to 120 minutes as the load subsiding stage, all regions return to the initial low load state; during the entire test process, the outlet water temperature of the cooling coil of the control group is constantly controlled at a set value sufficient to cope with the peak latent heat load, while the test group operates independently according to its internal load decoupling and distribution logic.

[0035] At the midpoint of the non-uniform load impact stage, i.e. at 60 minutes, the operation states of the two sets of systems show significant differences; the control group suppresses the high humidity in the mixed air, and the total instantaneous energy consumption reaches 18.5 kW, but since the cooling mode is undifferentiated, the relative humidity of the large conference room region is still 68.2% RH, and at the same time, the temperature of the small conference room region which has subsided the load is excessively cooled to 22.1°C; in contrast, the total instantaneous energy consumption of the test group at the same time is 15.6 kW, and its control module allocates the cooling capacity to the second heat exchange coil responsible for latent heat treatment, so that the relative humidity of the large conference room region is controlled at 54.5% RH, and the temperature of the small conference room region is maintained at 24.8°C, without overcooling phenomenon; this data difference directly reflects the operation mode of the test group, which separates the load information before energy treatment and allocates the cooling capacity to the dominant load type as needed, thereby reducing the total energy consumption of the system while improving the indoor environment quality control capability under complex load conditions.

[0036] Example 3: This example combines Figures 1 to 4A description of a composite heat exchange air conditioning fresh air system with independent temperature and humidity control, such as... Figure 1 As shown in the diagram, the system begins with a multi-source information acquisition module, which collects temperature and humidity data before mixing in each return air branch and transmits it to the central control module. The central control module performs load separation calculations and cooling capacity allocation decisions, and then differentiates the pre-cooling of the first heat exchange coil used for sensible heat treatment and the deep dehumidification of the second heat exchange coil used for latent heat treatment. It also adjusts the speed of the variable frequency fan according to the load ratio. At the same time, the central control module executes instantaneous disturbance suppression procedures based on the latent heat load data stream and uses the motor current harmonic signal obtained from the variable frequency fan to execute a self-diagnosis procedure for the health status of the system airflow, so as to realize maintenance early warning or fault alarm.

[0037] like Figure 2 As shown, the program comprises two parallel branches: wind path health self-diagnosis procedure calibration and instantaneous disturbance suppression procedure tuning. In the wind path health self-diagnosis procedure calibration, the system is placed in calibration mode and runs at all speed platforms. Harmonic features are extracted by acquiring and performing Fourier Transform (FFT) data, thereby establishing and storing a reference harmonic feature set. Subsequently, by applying known additional resistance and repeating the scanning process, deviation metrics are recorded, and finally, a maintenance judgment threshold is calculated and set. In the instantaneous disturbance suppression procedure tuning, an adjustable humidifier is used to simulate the growth process of latent heat load, and the peak acceleration is calculated and recorded. This is used to set the disturbance judgment threshold, thereby completing the entire calibration and tuning procedure.

[0038] like Figure 3 As shown, it includes a central controller with embedded independent temperature and humidity control software, and communicates with multiple temperature and humidity sensors of return air branch pipes and outdoor fresh air inlets deployed in the building space via a sensor bus. The central controller is connected to the air handling unit (AHU) via a control bus. The air handling unit includes at least a first heat exchange coil, a second heat exchange coil, and a variable frequency fan, thus forming a closed-loop control system of data acquisition, central decision-making, and terminal execution.

[0039] like Figure 4 As shown, within each control cycle, the control module first collects temperature and humidity data from the temperature and humidity sensors of each return air branch pipe. Then, it applies weighting factors to calculate the separated net sensible heat load and net latent heat load, and uses this as a basis to determine the cooling capacity distribution coefficient. Under the condition that the sensible heat load is dominant, the system increases the refrigerant flow rate to the first heat exchange coil and maintains the basic cooling capacity of the second heat exchange coil. Conversely, under the condition that the latent heat load is dominant, the system increases the refrigerant flow rate to the second heat exchange coil and decreases the refrigerant temperature, while reducing the refrigerant flow rate to the first heat exchange coil, and instructs the variable frequency fan to adjust its speed to match the current load characteristics.

[0040] Example 4: Before the completion of physical installation and the first operation of the composite heat exchange air conditioning fresh air system with independent temperature and humidity control, a set of systematic offline calibration and parameter setting procedures need to be performed to enable the internal self-diagnosis and disturbance suppression procedures to operate in a specific building environment. The necessity of this procedure lies in the fact that some core control parameters, such as the maintenance decision threshold for judging air path blockage and the disturbance decision threshold for triggering strong dehumidification, are directly related to the specific physical characteristics of the installed system, and therefore require a calibration process to determine their quantitative values. The calibration procedure first targets the self-diagnosis procedure for the health status of the system air path. In the initial state where the system filter is clean and all air valves are in the designed open position, the control module is placed in calibration mode. In this mode, the control module drives the variable frequency fan in the air handling unit to gradually increase from its lowest operating speed to the highest speed at a preset step of 5%, and maintains operation at each stable speed platform for 120 seconds. In the latter half of each stable speed platform period, the control module collects the operating current waveform of the variable frequency fan, performs a fast Fourier transform on it, and extracts the amplitudes of the 3rd, 5th and 7th characteristic harmonics to form a multi-dimensional vector corresponding to the speed. After completing the scanning of all speed platforms, the set of harmonic characteristic vectors corresponding to each speed platform collected is stored in the reference harmonic characteristic set in the control module. On this basis, the calculation method of the deviation measure value between the real-time harmonic characteristic and the reference harmonic characteristic set is determined as follows: at any time, when the variable frequency fan is operating at a certain speed, the Euclidean distance between its real-time harmonic characteristic vector and the reference vector corresponding to that speed stored in the reference harmonic characteristic set is the deviation measure value To determine the maintenance decision threshold, a adjustable damper is used to impose a known additional resistance equivalent to 50% of the final resistance of the filter to simulate progressive blockage of the filter, and the aforementioned scanning process is repeated under this condition, recording the deviation measure values corresponding to each speed platform and taking their average The final maintenance decision threshold is set to 70% of .

[0041] Subsequently, the procedure sets the disturbance decision threshold in the instantaneous disturbance suppression procedure. In a main return air branch of the system, a power adjustable ultrasonic humidifier is used to humidify at a known humidification rate, thereby reproducing the accelerated growth event of latent heat load under controlled conditions. The control module continuously calculates the time-varying acceleration of net latent heat load with a minimum control period of 10 seconds during this process, and records its peak value in the humidification event. This test is repeated to obtain a stable acceleration peak average The final disturbance decision threshold is set to 80%; meanwhile, during the calibration stage, the weight factor corresponding to each return air branch is calculated and normalized according to the as-built drawings or air volume balance report, and the interpolation estimation algorithm for sensor failure is configured to adopt the weighted average of the readings of the two effective sensors adjacent to the failed sensor in physical position; after the above calibration and setting procedures, the key parameters in the system control module are assigned values corresponding to the physical environment in which they are deployed, providing quantitative parameters corresponding to the physical environment for the operation of the system air path health status self-diagnosis procedure and instantaneous disturbance suppression procedure.

[0042] Example 5: In order to avoid the system frequently switching between the two operating modes when the absolute humidity value difference between outdoor fresh air and indoor return air is within the inherent noise range of the sensor, the control module is configured to include a hysteresis interval in the determination logic when performing the indoor and outdoor humidity comparison decision in the instantaneous disturbance suppression procedure; the logic enables an asymmetric double-threshold comparison rule, i.e. only when the absolute humidity of outdoor fresh air is lower than that of indoor return air, and the difference is greater than a first humidity difference threshold , the dilution operation of increasing fresh air ratio is performed.

[0043] If the system is currently in the dilution operation mode of increasing fresh air, it will only exit this mode when the absolute humidity of outdoor fresh air rises to not less than that of indoor return air; the core parameter of this determination mechanism with hysteresis interval is determined during the system calibration stage, and its determination basis is to continuously read the installed temperature and humidity sensor under stable working conditions, to calculate the noise amplitude of its data output, and to set the value of to 1.5 times the maximum noise amplitude; this determination mechanism helps the system avoid invalid switching between the two different operating modes under critical humidity conditions, thus contributing to the stable operation of the actuator such as the air valve.

[0044] Example 6: After the calibration procedure is completed and the reference harmonic feature set is established for the system, the control module continuously executes an online harmonic feature anomaly detection and instruction correlation analysis procedure for real-time monitoring of physical wind resistance sudden changes such as air valve sticking or accidental closing in the air path when the system enters the normal operating state; this procedure aims to effectively distinguish between a wind resistance sudden change caused by a real physical fault and a wind resistance change caused by normal system adjustment instructions; during the procedure, the control module performs a first-order difference operation on the data stream of the deviation metric value calculated continuously at a frequency of once per second to obtain its change rate And the rate of change data stream is high-pass filtered to filter out the slow drift caused by filter dust and other factors, so as to obtain a filtered signal capable of reflecting the rapid change of the wind resistance.

[0045] The control module continuously compares the absolute value of the filtered signal with a step determination threshold, which is determined in the calibration stage by statistically calculating the background noise standard deviation of the filtered signal when the system is normally running under different stable working conditions, and multiplying the standard deviation by a coefficient greater than 3; when the absolute value of the filtered signal continuously exceeds the step determination threshold for a duration of 3 seconds, the system preliminarily determines that a potential step change event occurs; after the event is preliminarily determined, the control module immediately retrieves its internal control instruction log to query whether there is any control instruction issued by itself within a very short time window containing the event occurrence time point, which can cause the system wind path physical wind resistance to change, including variable frequency fan speed regulation instruction and zone variable air volume terminal device air valve opening regulation instruction; if no such related instruction is found within the time window, the step change event is finally confirmed as a physical wind resistance mutation event, and a corresponding fault alarm is generated; such online monitoring and correlation analysis procedure provides a method for the system to distinguish between instruction-induced changes and non-instruction-induced mutations of the wind resistance during operation.

[0046] In the present application, the calculation of the sensible heat load and the latent heat load is based on thermodynamic principles, and is obtained by analyzing the temperature and humidity data collected from each return air branch. The calculation procedure is as follows: in each control period, the system first compares the temperature and absolute humidity data collected from each return air branch with the indoor set point temperature and absolute humidity, respectively, to determine the sensible heat load component and the latent heat load component of each branch; then, the load components of each branch are weighted and summed with the corresponding weight factor determined according to the building area or design fresh air volume of the area served by the branch, to obtain the total sensible heat load and the total latent heat load of the system. The mathematical expressions are as follows: ​​​​​​​​​​​​​​​Then, the control module will determine the cooling capacity distribution coefficient based on the relative magnitudes of the two values ​​using a preset control function. This coefficient is defined as the proportion of total latent heat load in the total load, i.e. and based on The value is mapped to the refrigerant flow regulation command of the first and second heat exchange coils through a lookup table or piecewise function, while the latent heat load dominates ( Greater than the preset threshold When the sensible heat load is dominant, the second heat exchange coil is instructed to lower the refrigerant temperature. Less than the preset threshold When the refrigerant flow rate of the first heat exchange coil is increased, this method enables precise on-demand delivery of cooling resources.

[0047] To ensure the effectiveness and reproducibility of the system's self-diagnostic function for airflow health, during the offline calibration phase, the control module employed a rigorous calibration procedure to determine the maintenance judgment threshold for identifying gradual increases in airflow resistance and the step judgment threshold for capturing sudden changes in airflow resistance. Specifically, under the initial clean and resistance-free state of the system, the variable frequency fan was driven to operate across the entire speed range at preset step sizes, and the operating current waveform at each stable speed platform was collected. A Fast Fourier Transform (FFT) was performed on the waveforms, and the harmonic feature vectors at each speed were extracted and stored. A reference harmonic feature set is formed; then, a known additional resistance simulating filter blockage is applied at the system's fresh air inlet, and the above full-speed scan procedure is repeated to obtain the harmonic feature vector under the resistance state. And through calculation and Euclidean distance between ,Right now Obtain deviation metrics at each rotational speed; finally, maintain the judgment threshold. Set as the deviation metric at all speeds average A certain percentage (e.g., 70%), i.e. For step detection threshold This refers to the deviation measurement value under normal system operation. The data stream is subjected to high-pass filtering, and the standard deviation of its background noise is calculated. and will Set as A multiple greater than 3 is used to ensure that the threshold can effectively distinguish between slow drift and transient mutation.

[0048] When the system is in normal operating mode, the control module continuously executes the online harmonic characteristic anomaly detection procedure, which includes two parallel subtasks: First, it periodically calculates the real-time harmonic characteristic vector. With reference harmonic characteristic set Euclidean distance of the reference vector corresponding to the rotational speed and compare it with the maintenance judgment threshold. When comparing, consistently higher At that time, the system issues a maintenance warning message indicating progressive blockage of the air duct; secondly, it continuously collects data... The data stream undergoes first-order differential and high-pass filtering to obtain a filtered signal that reflects rapid changes in wind resistance. and its absolute value is compared with the step threshold. Conduct continuous comparisons, when consecutively exceeding When a preset duration (e.g., 3 seconds) is reached, the system initially determines that a step change event has occurred. At this time, the control module immediately searches its internal control command log. If no self-command that can cause a corresponding change in the system's wind resistance is found in the log within a very short time window containing the time of the event, the event is finally confirmed as a physical wind resistance change event, and a corresponding fault alarm is generated. This procedure enables the system to achieve comprehensive and self-diagnostic assessment of the wind path health without additional hardware, which greatly improves the reliability and maintainability of the system in practical engineering applications.

[0049] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A composite heat exchange air conditioning fresh air system with independent temperature and humidity control, the system being applied to an air handling unit having a return air main duct for collecting airflow from multiple return air branch ducts, an adjustable fresh air and return air mixing device, and a first heat exchange coil and a second heat exchange coil, characterized in that, The system includes a control module, which is configured to perform the following operations: Step a: In each control cycle, before multiple return air branch pipes merge into the return air main pipe, collect temperature and humidity data in each return air branch pipe, and calculate the net sensible heat load and net latent heat load carried by the current system based on the temperature and humidity data and the weighting factor corresponding to each return air branch pipe. Step b: Based on the net sensible heat load and net latent heat load calculated in step a, determine the cooling capacity distribution coefficient, and drive the first heat exchange coil and the second heat exchange coil to operate according to the cooling capacity distribution coefficient. Step c: Calculate the time-varying acceleration of the net latent heat load. When the value of the time-varying acceleration reaches the disturbance judgment threshold, the instantaneous disturbance suppression procedure is executed. This procedure includes: collecting and comparing the absolute moisture content of the outdoor fresh air with the absolute moisture content of the indoor return air; if the absolute moisture content of the outdoor fresh air is lower than the absolute moisture content of the indoor return air, the fresh air and return air mixing device is instructed to operate for a first duration at the upper limit of the fresh air ratio; if the absolute moisture content of the outdoor fresh air is not lower than the absolute moisture content of the indoor return air, the fresh air and return air mixing device is instructed to operate for a second duration at the lower limit of the fresh air ratio, and the refrigerant supply of the second heat exchange coil is instructed to increase. The control module is configured to calculate the time-varying acceleration of the net latent heat load. Specifically, within a calculation window consisting of multiple consecutive control cycles, a numerical sequence of the net latent heat load is recorded, and the quantized value of the time-varying acceleration is obtained by performing a second-order difference operation on the numerical sequence. The second-order difference operation follows the following rules: ,in, This is the quantized value of the acceleration due to time change at the current moment. This represents the net latent heat load value for the current control cycle. and These are the net latent heat load values ​​for the first and second control cycles, respectively.

2. The composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 1, characterized in that, The control module is also configured to: update the fresh air ratio of the fresh air and return air mixing device according to the ratio of net sensible heat load to net latent heat load calculated in step a, provided that the indoor air quality meets the air quality standards; and, after the instantaneous disturbance suppression procedure is completed, the control module is configured to restore the fresh air ratio to the value determined by the aforementioned ratio.

3. The composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 1, characterized in that, The first heat exchange coil is a precooling coil, and the second heat exchange coil is a deep dehumidification coil. The control module is configured to drive the first heat exchange coil and the second heat exchange coil to operate according to the cooling capacity distribution coefficient. Specifically, this is done by adjusting the refrigerant flow rate through the precooling coil and the deep dehumidification coil, and adjusting the refrigerant temperature supplied to the deep dehumidification coil.

4. The composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 1, characterized in that, The air handling unit includes at least a variable frequency fan; the control module is also configured to execute a self-diagnostic procedure for the health status of the system airflow, which includes: during the initial calibration phase of the system, acquiring the operating current waveform of the variable frequency fan under calibration conditions, performing a Fourier transform on the operating current waveform to extract its harmonic features, and establishing and storing the harmonic features as a reference harmonic feature set; during system operation, periodically repeating the aforementioned process to obtain real-time harmonic features; calculating the deviation metric between the real-time harmonic features and the reference harmonic feature set; when the value of the deviation metric is continuously higher than the maintenance judgment threshold, generating and outputting maintenance warning information characterizing the progressive blockage of the system airflow.

5. A composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 4, characterized in that, The control module is configured to execute a self-diagnostic procedure for the health status of the system airflow, which further includes: performing high-pass filtering on the continuously acquired harmonic characteristic data stream of the variable frequency fan operating current to monitor whether there is a step change in the harmonic characteristics; recording all control commands issued by the control module itself; when a step change in the harmonic characteristics is detected, and the control commands recorded by the control module do not contain any commands that can cause changes in the system airflow resistance, it is determined that a physical airflow resistance change event has occurred in the system airflow, and a corresponding fault alarm is generated.

6. The composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 1, characterized in that, The system also includes a variable frequency fan that works in conjunction with the first and second heat exchange coils in the air handling unit; the control module is also configured to adjust the speed of the variable frequency fan based on the relative proportion of net sensible heat load to net latent heat load calculated in step a.

7. A composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 1, characterized in that, The control module is also configured to: perform validity checks on the temperature and humidity data collected in each return air branch pipe in step a; when the sensor data of a certain return air branch pipe is determined to be invalid data, the control module is configured to: remove the invalid data from the current load calculation, and generate replacement data through an interpolation estimation algorithm based on the historical data associated with the return air branch pipe and the valid data of the other return air branch pipes collected at the same time, so as to complete the calculation.

8. A composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 1, characterized in that, The weighting factor corresponding to each return air branch in step a is determined based on the design fresh air volume or building area of ​​the functional area corresponding to each return air branch.

9. A composite heat exchange air conditioning fresh air system with independent temperature and humidity control according to claim 1, characterized in that, The control module is configured to execute a transient disturbance suppression procedure. After the first or second duration of the procedure, it is also configured to execute an exit decision: continuously monitor the acceleration of the time change of the net latent heat load until its value falls below the disturbance decision threshold and remains stable for a certain duration, before restoring the system to the operating state determined by the rule in step b.

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