A u-shaped intersection energy-saving central air conditioning unit and control method

Abstract

The present application relates to air conditioning energy saving control technical field, specifically disclose a kind of U-shaped intersection energy-saving central air conditioning unit and control method. By extracting multiple excess oscillation data for analysis, determine heat transfer cliff early warning value and limit valve opening degree, then the heat transfer cliff early warning value is determined as the basis to determine the air supply temperature uncontrolled area, and combined with the limit valve opening degree to develop zoning control strategy. The present application locks the critical point of heat transfer cliff by heat transfer cliff early warning value, combined with limit valve opening degree to force to block the working fluid flow into micro-flow dangerous area, avoid excessive intervention triggered excessive valve-cold cliff-temperature overshoot-again valve vicious cycle, reduce the frequency of invalid valve action, reduce the pump power loss and heat energy offset caused by repeated opening and closing.

Description

Technical Field

[0001] This invention relates to the field of air conditioning energy-saving control technology, specifically to a U-shaped intersecting energy-saving central air conditioning unit and its control method. Background Technology

[0002] Due to phase change heat transfer technology, two sets of heat exchangers are set before and after the surface cooling, respectively. The recovered cold energy is used to pre-cool the fresh air before the surface cooling, and the recovered heat is used to preheat the dehumidified fresh air. In addition, heat pipe regulating valves can be used for regulation and control according to the operating conditions, such as overheat protection.

[0003] In the hot and humid summer, when the outdoor fresh air is hot and humid, the surface temperature of the pre-cooling section (evaporator) is lower than the air dew point, and a large amount of water vapor condenses, releasing vaporization heat to the reheat section (condenser). At this time, the total heat transferred by the heat pipe is much greater than the pure sensible heat, and the temperature of the reheat section is much higher than expected. This causes the heat pipe regulating valve installed on the liquid pipeline from the condenser outlet to the evaporator inlet to be adjusted, reducing the opening degree of the heat pipe regulating valve.

[0004] However, since precooling and reheating originate from the same source and flow, and the heat pipe regulating valve installed on the working fluid pipeline of the U-shaped phase change energy saver is relatively lagging behind the electric regulating valve of the reheat coil in terms of time, the supply air temperature will change directly from overheated to underheated, resulting in low-frequency oscillations with long periods and large amplitudes. At the same time, because the control system forces the working fluid to circulate at an extremely low flow rate after the heat pipe regulating valve is pressed to a very small opening, the heat exchange will drop sharply, completely disregarding the linear or equal percentage relationship between valve opening and flow rate, thus exacerbating the degree of low-frequency oscillation.

[0005] Therefore, the present invention provides a U-shaped intersecting energy-saving central air conditioning unit and a control method thereof. Summary of the Invention

[0006] The purpose of this invention is to provide a U-shaped intersecting energy-saving central air conditioning unit and control method to solve the above-mentioned background problems.

[0007] The objective of this invention can be achieved through the following technical solutions: A control method for a U-shaped intersecting energy-saving central air conditioning unit includes: Set a simulation test cycle to simulate the operation of the central air conditioning unit under high temperature and high humidity summer conditions. Analyze the supply air temperature obtained by monitoring in real time, construct cross-analysis time periods, and combine the valve opening and closing degree of the heat pipe regulating valve to conduct cross-analysis. Under the premise of determining reheat excess, extract the reheat excess starting point. A regular symmetry analysis was performed on the supply air temperature change trend after the reheat excess initiation point. While identifying the low-frequency oscillations caused by reheat excess, the supply air temperature monitoring data was archived as oscillation data caused by excess. Multiple data points on oscillations caused by excess heat were extracted and analyzed to determine the early warning value of heat exchange cliff and the limit valve opening degree. Based on the heat exchange cliff warning value, the uncontrolled zone of supply air temperature is determined, and a zone control strategy is formulated in combination with the limit valve opening degree.

[0008] A U-shaped intersecting energy-saving central air conditioning unit includes: Reheat Excess Analysis Module: Set a simulation test cycle to simulate the operation of the central air conditioning unit under high temperature and high humidity summer conditions. Analyze the supply air temperature obtained by monitoring in real time, construct cross-analysis time periods, and combine the valve opening and closing degree of the heat pipe regulating valve to perform cross-analysis. Under the premise of determining reheat excess, extract the reheat excess starting point. Oscillation Trigger Judgment Module: Performs regularity and symmetry analysis on the supply air temperature change trend after the reheat excess initiation point. While identifying low-frequency oscillations caused by reheat excess, it archives the supply air temperature monitoring data as excess-induced oscillation data. Oscillation-induced analysis module: Extracts and analyzes multiple excess-induced oscillation data to determine the heat exchange cliff warning value and the limit valve opening degree; Strategic Zoning Control Module: Based on the heat exchange cliff warning value, determine the uncontrolled zone of supply air temperature, and formulate zoning control strategies in combination with the limit valve opening degree.

[0009] The beneficial effects of this invention are as follows: 1. This invention sets a simulation test cycle to simulate the operation of a central air conditioning unit under high temperature and humidity conditions in summer. It monitors and acquires the supply air temperature in real time and performs cross-analysis based on the valve opening and closing degree of the heat pipe regulating valve to determine if reheat excess occurs. If reheat excess is detected, the starting point of reheat excess is extracted, and the trend of supply air temperature change after the starting point is analyzed for regularity and symmetry to identify whether reheat excess triggers low-frequency oscillations. The supply air temperature monitoring data within the simulation test cycle where reheat excess triggers low-frequency oscillations are archived as oscillation data caused by excess, avoiding frequent interventions due to misjudgments. This ensures that the heat pipe regulating valve only operates under conditions where there is genuine cooling and heating offset, significantly reducing the dual loss of electrical and thermal energy caused by excessive reheating. It also provides data support for quickly identifying whether current reheat excess triggers low-frequency oscillations.

[0010] 2. This invention extracts and analyzes multiple excess-induced oscillation data to determine the heat exchange cliff warning value and the limit valve opening degree. Based on the heat exchange cliff warning value, the uncontrolled air supply temperature zone is determined. Combined with the limit valve opening degree, a zoned control strategy is formulated. The heat exchange cliff warning value is used to lock the critical point of sudden drop in heat exchange. Combined with the limit valve opening degree, the working fluid flow is forcibly blocked from entering the micro-flow danger zone. This avoids the vicious cycle of excessive valve closure triggered by excessive intervention—cold capacity cliff—temperature overshoot—re-valve closure, reduces the frequency of ineffective valve operation, and reduces pump power loss and heat energy offset caused by repeated opening and closing. Attached Figure Description

[0011] The invention will now be further described with reference to the accompanying drawings.

[0012] Figure 1 This is a flowchart of the steps of a U-shaped intersecting energy-saving central air conditioning unit control method according to the present invention; Figure 2 This is a flowchart illustrating the determination process of a U-shaped intersecting energy-saving central air conditioning unit control method according to the present invention. Figure 3 This is a module flowchart of a U-shaped intersecting energy-saving central air conditioning unit according to the present invention. Detailed Implementation

[0013] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0014] Example 1 like Figure 1 - Figure 2 As shown, the present invention provides a control method for a U-shaped intersecting energy-saving central air conditioning unit, comprising: Step 1: Set the simulation test cycle to simulate the operation of the central air conditioning unit under the high temperature and high humidity summer conditions. While monitoring and obtaining the supply air temperature in real time, combine the valve opening and closing degree of the heat pipe regulating valve to perform cross analysis to determine whether there is reheat excess. If reheat excess is determined to occur, extract the reheat excess starting point. In some embodiments, the simulation test period is divided into several simulation monitoring points, wherein the interval between adjacent simulation monitoring points is equal. The supply air temperature at each simulated monitoring point is obtained and compared with the target set temperature. The process is as follows: If the supply air temperature is less than or equal to the target set temperature, it indicates that the supply air temperature at the current simulated monitoring point has not exceeded the target set temperature, and it is displayed as a continuous monitoring signal; If the supply air temperature is greater than the target set temperature, it indicates that the supply air temperature at the current simulated monitoring point exceeds the target set temperature, generating a cross-analysis signal and triggering a valve opening / closing degree analysis command. When the valve opening degree analysis command is triggered, the simulated monitoring point corresponding to the continuously generated cross-analysis signal is selected as the cross-analysis point, and compared according to the time sequence to extract the earliest and latest cross-analysis points, and then the cross-analysis time period is constructed. During the cross-analysis period, the valve opening degree at each cross-analysis point is obtained, and a valve opening degree change curve is constructed with the X-axis representing time and the Y-axis representing the valve opening degree according to the time sequence. By taking the line segment between adjacent coordinate points on the valve opening change curve as a valve opening change sub-curve, multiple valve opening change sub-curves can be obtained. Substitute the coordinates of the two endpoints of each valve opening change sub-curve into the slope calculation formula to obtain the slope of the single sub-curve. Select valve opening change sub-curves with negative slopes as valve opening / closing adjustment sub-curves, count their number, and calculate the ratio of the number of valve opening / closing adjustment sub-curves to the number of valve opening / closing adjustment sub-curves. The continuous valve opening and closing down-adjustment sub-curves in the time dimension will be merged, and the corresponding length in the time dimension will be obtained. The ratio of the length of the cross-analysis period will be used as the valve opening and closing down-adjustment duration ratio. The sum of the ratio of valve opening / closing reduction quantity to the ratio of valve opening / closing reduction duration is used to obtain the reheat excess judgment value. Understandably, the reheat excess judgment value is used to characterize whether there is excessive reheating in the central air conditioning system under high temperature and high humidity conditions. Under the premise that the supply air temperature is continuously higher than the target set temperature, it is a composite result that integrates two key dimensions: the frequency characteristics and the duration characteristics of valve action. On the one hand, the valve opening and closing reduction ratio reflects the proportion of the sub-curves showing a downward trend in the valve opening change sub-curves formed by all adjacent monitoring points. If the valve opening and closing reduction ratio is larger, the valve opening and closing degree is actively reduced more frequently per unit time, reflecting repeated intervention in the subcooled state and indicating a high frequency of reheating behavior. On the other hand, the valve opening and closing reduction duration ratio reflects the proportion of the total duration of the continuous reduction segment to the entire cross-analysis period. If the valve opening and closing reduction duration ratio is larger, the valve maintains a small opening state for a longer period of time, indicating a strong duration of reheating behavior. If the reheat excess judgment value is greater than the reheat excess judgment threshold, it indicates that reheat excess occurs during the cross-analysis period, and a reheat excess signal is generated. If the reheat excess judgment value is less than or equal to the reheat excess judgment threshold, it indicates that no reheat excess phenomenon has occurred during the cross-analysis period, and a continued monitoring signal is generated. It should be noted that the reheat excess judgment threshold refers to the decision boundary used for switching control strategies. It is used to distinguish between normal reheat regulation and energy-wasting reheat excess. Technicians will collect operating data of the central air conditioning system under multiple typical summer conditions, including supply air temperature fluctuations, valve opening and closing degree change curves, energy consumption records and user feedback. By statistically analyzing the distribution of reheat excess judgment values ​​of all operating cases during the period of continuous supply air temperature exceeding the limit, the 90th quantile or mean + 1 standard deviation is extracted as the initial threshold to ensure that the value can cover the vast majority of normal regulation behaviors, while effectively identifying abnormal high energy consumption modes. The starting point of the first valve opening and closing adjustment curve is taken as the simulated monitoring point on the X-axis as the starting point of reheat excess, and the command to analyze the change in supply air temperature is initiated.

[0015] Step 2: Perform a regularity and symmetry analysis on the supply air temperature change trend after the reheat excess starting point to identify whether the reheat excess causes low-frequency oscillation. Archive the supply air temperature monitoring data during the simulation test cycle of low-frequency oscillation caused by reheat excess as excess-induced oscillation data. To help understand this, the coupling of the heat pipe valve and the reheat valve causes the two control loops to be out of sync, resulting in stable periodic oscillations. Therefore, a small coefficient of variation of the period is a necessary characteristic of coupled oscillations. Moreover, due to thermal inertia, the nonlinearity of the phase change process, and the cliff-like drop in cooling capacity caused by insufficient liquid supply, these physical mechanisms will cause the temperature drop slope to be steep and the rise slope to be gentle, forming an asymmetrical waveform.

[0016] In some embodiments, based on the reheat excess starting point, the supply air temperature of each simulated monitoring point after the reheat excess starting point is extracted, and according to the time sequence, a supply air temperature change curve is constructed with the X-axis as time and the Y-axis as supply air temperature. For example, extract all peak coordinate points of the air supply temperature change curve, and obtain the distance between adjacent peak coordinate points in the X-axis dimension as the adjacent peak time interval. Calculate the standard deviation of all adjacent peak time intervals to obtain the standard deviation of adjacent peak time intervals; The mean of the time intervals between all adjacent peaks is calculated by summing and averaging all the time intervals between adjacent peaks. The standard deviation and mean of the adjacent peak interval are calculated using the coefficient of variation formula to obtain the periodic coefficient of variation value. It should be understood that the period variation coefficient value refers to a relative quantitative index of the stability of the supply air temperature oscillation period after the reheat excess initiation point. It reflects the degree of dispersion of the time interval between adjacent peaks relative to the fluctuation level of its average period. Moreover, it is calculated by the ratio of the standard deviation of the adjacent peak interval to the mean. Essentially, it is a dimensionless relative volatility. Specifically, if the period variation coefficient value is larger, it indicates that the peak interval time fluctuates violently and the oscillation period is unstable, which does not meet the essential definition of coupled oscillation and should be excluded from the typical oscillation mode caused by reheat excess. If the period variation coefficient value is smaller, it indicates that the peak interval time is highly consistent with the adjacent peak interval, and the temperature oscillation exhibits a near-perfect periodicity, which meets the essential definition of coupled oscillation and should be considered as a typical oscillation mode caused by reheat excess. When the value of the period variation coefficient is greater than the period variation coefficient threshold, it indicates that the peak interval time fluctuates violently and the oscillation period is unstable. This does not conform to the essential definition of coupled oscillation and should be excluded from the typical oscillation mode caused by reheat excess, generating a continued monitoring signal. When the value of the period variation coefficient is less than or equal to the period variation coefficient threshold, it indicates that the peak interval duration and the adjacent peak interval duration are highly consistent, and the temperature oscillation exhibits a near-perfect periodicity, which conforms to the essential definition of coupled oscillation. It should be considered as a typical oscillation mode caused by reheat excess, triggering the waveform symmetry analysis command. It should be understood that the periodic variation coefficient threshold is obtained by those skilled in the art based on statistical experience methods driven by engineering data. Specifically, the technicians first conduct long-term simulated operation of the U-shaped intersecting energy-saving central air conditioning unit under multiple typical high-temperature and high-humidity summer operating conditions, collect a large amount of supply air temperature time series data, extract the adjacent peak time interval value sequence within each test cycle, and calculate the corresponding periodic variation coefficient value accordingly. Subsequently, statistical distribution analysis is performed on these measured periodic variation coefficient values, and the 90th quantile or mean plus one standard deviation is used as the basis for setting the initial threshold. This is mainly used as the decision boundary for control strategy switching, realizing the leap from passive response to active diagnosis: when the periodic variation coefficient value exceeds the threshold, the system determines that the oscillation is a random disturbance and does not trigger subsequent analysis to avoid false actions; when the periodic variation coefficient value is lower than the threshold, indicating that the oscillation has the essential characteristic of stable periodicity of coupled oscillation, the waveform symmetry analysis command is initiated to further verify the asymmetric energy imbalance mode with steep decline and gentle rise, and finally confirm the low-frequency oscillation caused by reheat excess and trigger the data archiving process. Extract all the trough coordinates of the air supply temperature change curve, and take the curve segment from peak to trough as a descending waveform analysis line to obtain multiple descending waveform analysis lines. By taking the curve segment from trough to peak as a rising waveform analysis line, multiple rising waveform analysis lines can be obtained. In this case, the peaks and troughs on the curve segment from peak to trough are adjacent, and the troughs and peaks on the curve segment from trough to peak are also adjacent. After connecting each descending waveform analysis line and each ascending waveform analysis line with a straight line, the slope of each descending waveform analysis line and each ascending waveform analysis line is calculated using the slope calculation formula (the actual curve segment between the peak and the trough is linearly fitted, and the slope of the fitted line is used as the representative slope of the segment), thus obtaining the descending waveform slope and the ascending waveform slope. Based on the condition that the falling waveform analysis line and the rising waveform analysis line are in adjacent positions on the supply air temperature change curve, the corresponding falling waveform slope and rising waveform slope are combined to obtain waveform symmetry analysis groups, and multiple waveform symmetry analysis groups are obtained. Within the waveform symmetry analysis group, the absolute values ​​of the slopes of the falling waveform and the rising waveform are processed separately, and their ratios are calculated to obtain the waveform symmetry analysis ratio. The symmetry analysis coefficient values ​​are obtained by averaging the symmetry analysis ratios of all waveforms. It should be understood that the symmetry analysis coefficient value is a comprehensive quantitative indicator that measures the degree of asymmetry in the rising and falling phases of the supply air temperature oscillation waveform caused by reheat excess. Starting from the physical response characteristics of energy transfer, it reveals the dynamic imbalance of the thermal system during the process of a cliff-like drop and slow recovery of cooling capacity. Specifically, when the symmetry analysis coefficient value approaches 1, it indicates that the rates of the falling and rising processes are close, and the waveform tends to be symmetrical. This may be due to the control strategy tending to be coordinated or the system being in a stable operating condition, which does not conform to the characteristics of reheat excess. When the symmetry analysis coefficient value deviates from 1, it indicates that the asymmetric characteristics of rapid decline and slow recovery are continuously exhibited in multiple oscillation cycles, which conforms to the characteristics of low-frequency coupled oscillation caused by reheat excess. When the symmetry analysis coefficient value approaches 1, it indicates that the rates of the descent and ascent processes are close, and the waveform tends to be symmetrical. This may be due to the control strategy becoming more coordinated or the system being in a stable operating condition, which does not meet the characteristics of excess reheat, thus generating a continued monitoring signal. When the symmetry analysis coefficient value deviates from 1, it indicates that the asymmetric characteristics of rapid decline and slow recovery are continuously exhibited in multiple oscillation cycles, which is consistent with the characteristics of low-frequency coupled oscillation caused by reheat excess. An excess-induced oscillation signal is generated, and the supply air temperature and valve opening degree of each simulated monitoring point after the reheat excess start point are archived as excess-induced oscillation data. Specifically, when the symmetry analysis coefficient value falls within the range of 0.8 to 1.2, it is determined to be close to 1; when the symmetry analysis coefficient value is not within the range of 0.8 to 1.2, it is determined to be deviating from 1. The above range is determined based on statistical analysis of at least 50 sets of typical summer operating conditions' supply air temperature oscillation waveforms—under normal regulation conditions without reheat excess, the symmetry analysis coefficient value distribution ranges from 0.82 to 1.18. Taking the upper and lower boundaries of this distribution range and appropriately expanding it, the determination range of 0.8 to 1.2 is obtained. This range can be adjusted according to actual operating conditions. The adjustment method is to re-collect the waveform symmetry analysis ratios of the most recent 100 sets of non-oscillating operating conditions, and take the minimum and maximum values ​​as the new range boundaries. Moreover, the analysis in the above embodiments is based on the analysis of periodic regularity but symmetrical waveform (pure sine wave). This may be a stable fluctuation during normal adjustment of the heat pipe valve and does not constitute harmful oscillation. Therefore, only when both periodic regularity and waveform asymmetry are satisfied should it be judged as excess causing oscillation.

[0017] The proposed solution is as follows: A simulation test cycle is set to simulate the operation of a central air conditioning unit under high temperature and humidity conditions in summer. The supply air temperature is monitored and acquired in real time. Combined with the valve opening and closing degree of the heat pipe regulating valve, cross-analysis is performed to determine whether reheat excess occurs. If reheat excess is determined, the starting point of reheat excess is extracted. The trend of supply air temperature change after the starting point of reheat excess is analyzed for regularity and symmetry to identify whether reheat excess causes low-frequency oscillation. The supply air temperature monitoring data during the simulation test cycle in which reheat excess causes low-frequency oscillation is archived as oscillation data caused by excess, avoiding frequent intervention due to misjudgment. This ensures that the heat pipe regulating valve only operates under conditions where there is actual cooling and heating offset, significantly reducing the double loss of electrical and thermal energy caused by excessive reheat. This provides data support for quickly identifying whether current reheat excess causes low-frequency oscillation.

[0018] Example 2 like Figure 1 - Figure 2 As shown, the present invention provides a control method for a U-shaped intersecting energy-saving central air conditioning unit, specifically including: Step 3: Extract and analyze multiple data points on oscillations caused by excess heat to determine the early warning value for heat exchange cliff and the limit valve opening degree; In some embodiments, the excess oscillation data includes: the supply air temperature at each simulated monitoring point, and the valve opening degree; That is, each simulation test cycle in which an excess-induced oscillation signal is generated is marked as an excess-induced oscillation event. In each excess-induced oscillation event, the valve opening degree of each simulation monitoring point is summed and averaged to obtain the average opening degree of a single event. Similarly, on the supply air temperature change curve, the difference between the supply air temperature values ​​corresponding to the peak and the trough is used to obtain the unit temperature oscillation amplitude value. It should be noted that the peaks and troughs are adjacent on the air supply temperature change curve; The average temperature amplitude of a single event is obtained by summing and averaging the temperature oscillation amplitude values ​​of all units. Extract the symmetric analysis coefficient values ​​for each excess-induced oscillation event; Based on the average opening and closing degree and the average temperature amplitude of a single event within each excess-induced oscillation event, an opening-closing-temperature scatter plot is constructed. Based on the mean value of the opening and closing degree of a single event and the value of the symmetry analysis coefficient within each excess-induced oscillation event, an opening-closing-symmetry scatter plot is constructed. For example, the average opening and closing degree of each single event in all excess-induced oscillation events is sorted in ascending order to form an event opening and closing sequence; On the opening-closing-temperature scatter plot, according to the order of the event opening and closing sequence, the mean of the temperature amplitude of a single event corresponding to two adjacent points is subtracted, and the absolute value is taken to obtain the change in temperature amplitude of the adjacent point. Meanwhile, on the opening-closing symmetric scatter plot, according to the order of the event opening and closing sequence, the difference between the symmetric analysis coefficients corresponding to two adjacent points is calculated, and the absolute value is taken to obtain the symmetric analysis change of the adjacent points. The point where the change in temperature amplitude of neighboring points first exceeds the preset threshold for temperature amplitude change is marked as the starting point of temperature amplitude amplification, and the average opening and closing degree of a single event corresponding to the starting point of temperature amplitude amplification is extracted as the opening and closing value of temperature amplitude amplification. The point where the change in the neighboring point symmetry analysis first exceeds the preset symmetry analysis change threshold is marked as the starting point of symmetry analysis aggravation, and the average opening and closing degree of the single event corresponding to the starting point of symmetry analysis aggravation is extracted as the opening and closing value of symmetry analysis aggravation. If the temperature amplitude amplification opening value is greater than the symmetric analysis amplification opening value, then the temperature amplitude amplification opening value is taken as the limit valve opening degree, and the average temperature amplitude of a single event corresponding to the starting point of temperature amplitude amplification is taken as the heat exchange cliff warning value. If the temperature amplitude amplification opening and closing value is less than the symmetric analysis amplification opening and closing value, then the symmetric analysis amplification opening and closing value will be used as the limit valve opening degree, and the average temperature amplitude of a single event corresponding to the amplification starting point of the symmetric analysis will be used as the heat exchange cliff warning value. If the temperature amplitude amplification opening and closing value is equal to the symmetric analysis amplification opening and closing value, then the temperature amplitude amplification opening and closing value is taken as the limit valve opening degree, and the average temperature amplitude of a single event corresponding to that point is taken as the heat exchange cliff warning value.

[0019] Step 4: Based on the heat exchange cliff warning value, determine the uncontrolled area of ​​the supply air temperature, and formulate a zone control strategy in combination with the limit valve opening degree; In some embodiments, half of the heat exchange cliff warning value is taken as the uncontrolled deviation of the supply air temperature; Extract the current target set temperature, sum the current target set temperature and the uncontrolled deviation of the supply air temperature to obtain the upper limit of the uncontrolled supply air temperature; The difference between the current target set temperature and the uncontrolled deviation of the supply air temperature is calculated to obtain the lower limit of the uncontrolled supply air temperature. Combined with the upper limit of the uncontrolled supply air temperature, the uncontrolled supply air temperature zone is formed. The reason is that the heat exchange cliff warning value is a peak-to-valley difference range. Taking half of it as the allowable upper and lower deviations ensures that when the supply air temperature falls within the dead zone, it will not trigger the adjustment action that would cause the valve to close further. This avoids the valve opening degree from exceeding the limit value, causing heat exchange cliff and oscillation. Moreover, it is determined based on the physical boundary of oscillation caused by reheat excess in actual operating data, which can effectively prevent control loop malfunctions and eliminate low-frequency oscillations. The real-time supply air temperature obtained from the simulated monitoring points is extracted and compared with that of the uncontrolled supply air temperature zone. The process is as follows: When the supply air temperature is in the uncontrolled supply air temperature range, the current opening of the heat pipe regulating valve remains unchanged. When the supply air temperature exceeds the uncontrolled supply air temperature range, it will be displayed as overheating of the supply air temperature. The opening degree of the heat pipe regulating valve will be reduced, but the adjusted opening degree cannot exceed the limit valve opening degree. When the supply air temperature is lower than the supply air temperature uncontrolled zone, it will be displayed as supply air temperature too cold. The control will increase the opening degree of the heat pipe regulating valve, and the limit of the opening degree is that the valve is fully open.

[0020] This embodiment specifically involves: extracting and analyzing multiple excess-induced oscillation data to determine the heat exchange cliff warning value and the limit valve opening degree. Based on the heat exchange cliff warning value, the uncontrolled air supply temperature zone is determined. Combined with the limit valve opening degree, a zoned control strategy is formulated. The heat exchange cliff warning value is used to lock the critical point of sudden drop in heat exchange. Combined with the limit valve opening degree, the working fluid flow is forcibly blocked from entering the micro-flow danger zone. This avoids the vicious cycle of excessive valve closure triggered by excessive intervention—cold capacity cliff—temperature overshoot—re-valve closure, reducing the frequency of ineffective valve operation, and reducing pump power loss and heat energy offset caused by repeated opening and closing.

[0021] Example 3 Please see Figure 3 As shown, the present invention provides a U-shaped intersecting energy-saving central air conditioning unit, comprising: Reheat Excess Analysis Module: Set a simulation test cycle to simulate the operation of the central air conditioning unit under high temperature and high humidity summer conditions. Analyze the supply air temperature obtained by monitoring in real time, construct cross-analysis time periods, and combine the valve opening and closing degree of the heat pipe regulating valve to perform cross-analysis. Under the premise of determining reheat excess, extract the reheat excess starting point. Oscillation Trigger Judgment Module: Performs regularity and symmetry analysis on the supply air temperature change trend after the reheat excess initiation point. While identifying low-frequency oscillations caused by reheat excess, it archives the supply air temperature monitoring data as excess-induced oscillation data. Oscillation-induced analysis module: Extracts and analyzes multiple excess-induced oscillation data to determine the heat exchange cliff warning value and the limit valve opening degree; Strategic Zoning Control Module: Based on the heat exchange cliff warning value, determine the uncontrolled zone of supply air temperature, and formulate zoning control strategies in combination with the limit valve opening degree.

[0022] The foregoing has provided a detailed description of one embodiment of the present invention, but this description is merely a preferred embodiment and should not be construed as limiting the scope of the invention. All equivalent variations and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A control method for a U-shaped intersecting energy-saving central air conditioning unit, characterized in that: Set a simulation test cycle to simulate the operation of the central air conditioning unit under high temperature and high humidity summer conditions. Analyze the supply air temperature obtained by monitoring in real time, construct cross-analysis time periods, and combine the valve opening and closing degree of the heat pipe regulating valve to conduct cross-analysis. Under the premise of determining reheat excess, extract the reheat excess starting point. A regular symmetry analysis was performed on the supply air temperature change trend after the reheat excess initiation point. While identifying the low-frequency oscillations caused by reheat excess, the supply air temperature monitoring data was archived as oscillation data caused by excess. Multiple data points on oscillations caused by excess heat were extracted and analyzed to determine the early warning value of heat exchange cliff and the limit valve opening degree. Based on the heat exchange cliff warning value, the uncontrolled zone of supply air temperature is determined, and a zone control strategy is formulated in combination with the limit valve opening degree.

2. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 1, characterized in that: The process of constructing the cross-analysis time period and combining it with the valve opening degree of the heat pipe regulating valve is as follows: The simulation test cycle is divided into several simulation monitoring points. The air supply temperature of each simulation monitoring point is obtained and compared with the target set temperature. The signal generated when the air supply temperature is greater than the target set temperature is used as the cross-analysis signal. Simulated monitoring points that continuously generate cross-analysis signals are selected as cross-analysis points. The earliest and latest cross-analysis points are extracted in chronological order to construct the cross-analysis time period. Obtain the valve opening degree at each cross-analysis point within the cross-analysis period, construct the valve opening degree change curve in chronological order, take the line segment between adjacent coordinate points on the curve as the valve opening degree change sub-curve, and calculate the slope of each sub-curve to obtain the single sub-line slope.

3. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 2, characterized in that: Once reheat excess is determined, the process of extracting the starting point of reheat excess is as follows: The valve opening change sub-curve with a negative slope is taken as the valve opening and closing downward adjustment sub-curve. The number of valve opening and closing downward adjustment sub-curves is counted, and its ratio to the total number of valve opening change sub-curves is calculated to obtain the valve opening and closing downward adjustment number ratio. By merging the valve opening and closing down-adjustment sub-curves that are continuous in time, and calculating the ratio of the total duration of the merged sub-curve to the duration of the cross-analysis period, the valve opening and closing down-adjustment duration ratio is obtained. The sum of the ratio of valve opening / closing reduction quantity to the ratio of valve opening / closing reduction duration is used to obtain the reheat excess judgment value. When the reheat excess judgment value is greater than the reheat excess judgment threshold, reheat excess is determined to have occurred, and the simulated monitoring point corresponding to the starting coordinate of the first valve opening and closing adjustment curve is taken as the reheat excess starting point.

4. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 1, characterized in that: The process of regularity symmetry analysis includes periodicity analysis, and the following is the process of periodicity analysis: Extract the supply air temperature at each simulated monitoring point after the reheat excess starting point, and construct the supply air temperature change curve in time sequence; Extract all peak coordinates of the air supply temperature change curve and obtain the time interval between adjacent peaks as the adjacent peak time interval. The coefficient of variation is calculated for all adjacent peak time intervals to obtain the periodic coefficient of variation value; When the periodic variation coefficient value is less than or equal to the periodic variation coefficient threshold, a waveform symmetry analysis command is triggered.

5. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 4, characterized in that: The process of regularity symmetry analysis also includes waveform regularity analysis, the process of which is as follows: Extract all trough coordinates of the air supply temperature change curve, take the curve segment from adjacent peak to trough as the falling waveform analysis line, and take the curve segment from adjacent trough to peak as the rising waveform analysis line. For each falling waveform analysis line, perform linear fitting and use the slope of the fitted line as the slope of the falling waveform; For each rising waveform analysis line, perform a linear fit and use the slope of the fitted line as the rising waveform slope.

6. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 5, characterized in that: After determining that the low-frequency oscillation was caused by excess reheat, the data on the oscillation caused by excess were obtained as follows: The adjacent falling waveform analysis lines and rising waveform analysis lines on the supply air temperature change curve are paired to form a waveform symmetry analysis group; Within each waveform symmetry analysis group, the absolute values ​​of the descending waveform slope and the ascending waveform slope are taken and then the ratio is calculated to obtain the waveform symmetry analysis ratio. Calculate the mean of the symmetry analysis ratios for all waveforms to obtain the symmetry analysis coefficient values; When the symmetry analysis coefficient value deviates from 1, it is determined that a low-frequency oscillation caused by reheat excess has occurred. The supply air temperature and valve opening degree of each simulated monitoring point after the reheat excess start point will be archived as the oscillation data caused by excess.

7. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 6, characterized in that: The process of extracting and analyzing multiple excess-induced oscillation data: Each simulation test cycle that generates excess oscillation data is recorded as an excess oscillation event. Calculate the average valve opening degree at all simulated monitoring points in each excess-induced oscillation event to obtain the average opening degree for a single event; On the supply air temperature change curve of each excess-induced oscillation event, calculate the absolute value of the supply air temperature difference between adjacent peaks and troughs to obtain the unit temperature oscillation amplitude value, and calculate the average value of the temperature oscillation amplitude values ​​of all units to obtain the average temperature amplitude of a single event. Extract the symmetric analysis coefficient values ​​for each excess-induced oscillation event; Construct an opening / closing-temperature scatter plot with the average opening / closing degree of a single event as the horizontal axis and the average temperature amplitude of a single event as the vertical axis. An opening-closing scatter plot is constructed with the average opening degree of a single event as the horizontal axis and the symmetry analysis coefficient as the vertical axis.

8. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 7, characterized in that: The process of determining the heat exchange cliff warning value and the limit valve opening degree: Sort all excess-induced oscillation events in ascending order of the average opening and closing degree of a single event to obtain the event opening and closing sequence; On the opening-closing-temperature scatter plot, the absolute value of the difference between the mean values ​​of the single event temperature amplitude of adjacent events is calculated according to the event opening-closing sequence to obtain the change in temperature amplitude of adjacent points. On the opening-closing symmetric scatter plot, the absolute value of the difference between the symmetric analysis coefficients of adjacent events is calculated according to the opening-closing sequence of events to obtain the change in symmetric analysis of adjacent points; The average opening and closing value corresponding to the event where the temperature amplitude change of the first neighboring point is greater than the preset temperature amplitude change threshold is used as the temperature amplitude amplification opening and closing value. The average opening and closing value corresponding to the event where the change in the first neighboring point symmetry analysis is greater than the preset symmetry analysis change threshold is used as the symmetry analysis aggravation value for opening and closing. The larger of the temperature amplitude amplification opening and closing value and the symmetric analysis amplification opening and closing value is taken as the limit valve opening degree, and the average temperature amplitude of the single event corresponding to this opening degree is taken as the heat exchange cliff warning value. If the two are equal, the equal value is taken as the limit valve opening degree, and the average temperature amplitude of the single event corresponding to that point is taken as the heat exchange cliff warning value.

9. The control method for a U-shaped intersecting energy-saving central air conditioning unit according to claim 1, characterized in that: The process of identifying uncontrolled supply air temperature zones and developing zone control strategies: Half of the heat exchange cliff warning value is taken as the uncontrolled deviation of the supply air temperature. The sum of the target set temperature and the uncontrolled deviation of the supply air temperature is taken as the upper limit of the uncontrolled supply air temperature, and the difference between the target set temperature and the uncontrolled deviation of the supply air temperature is taken as the lower limit of the uncontrolled supply air temperature. The upper limit and the lower limit constitute the uncontrolled supply air temperature zone. When the supply air temperature is in the uncontrolled range, keep the opening of the heat pipe regulating valve unchanged; When the supply air temperature is higher than the upper limit of the supply air temperature control, the opening of the heat pipe regulating valve is reduced to reduce the amount of reheat, but the lower limit of the opening is the limit valve opening degree. When the supply air temperature is lower than the lower limit of the supply air temperature control, the opening of the heat pipe regulating valve is increased, with the upper limit of the opening being fully open.

10. A U-shaped intersecting energy-saving central air conditioning unit, based on the control method for a U-shaped intersecting energy-saving central air conditioning unit according to any one of claims 1 to 9, characterized in that: Reheat Excess Analysis Module: Set a simulation test cycle to simulate the operation of the central air conditioning unit under high temperature and high humidity summer conditions. Analyze the supply air temperature obtained by monitoring in real time, construct cross-analysis time periods, and combine the valve opening and closing degree of the heat pipe regulating valve to perform cross-analysis. Under the premise of determining reheat excess, extract the reheat excess starting point. Oscillation Trigger Judgment Module: Performs regularity and symmetry analysis on the supply air temperature change trend after the reheat excess initiation point. While identifying low-frequency oscillations caused by reheat excess, it archives the supply air temperature monitoring data as excess-induced oscillation data. Oscillation-induced analysis module: Extracts and analyzes multiple excess-induced oscillation data to determine the heat exchange cliff warning value and the limit valve opening degree; Strategic Zoning Control Module: Based on the heat exchange cliff warning value, determine the uncontrolled zone of supply air temperature, and formulate zoning control strategies in combination with the limit valve opening degree.

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