A multi-mode adaptive air conditioning and fresh air composite control system

Abstract

This invention relates to the field of air conditioning and ventilation control technology, specifically to a multi-mode adaptive air conditioning and fresh air composite control system. The controller estimates the rate of change and extrapolates the boundary variables such as indoor and outdoor enthalpy difference, carbon dioxide concentration margin, and winter frost margin to obtain the predicted dwell time when the boundary conditions of the candidate operating mode are first violated. The costs of compressor start-up and shutdown, damper and fan transition, core reconstruction, and air supply recovery are combined into a switching cost. The shortest effective dwell time is obtained by dividing the switching cost by the time-varying net benefit of the candidate operating mode. Switching is performed only when the predicted dwell time is not less than the shortest effective dwell time, thereby reducing the frequency of mode switching and the total power consumption throughout the cycle, and improving equipment durability and indoor thermal environment stability.

Description

Technical Field

[0001] This invention relates to the field of air conditioning and ventilation control technology, and more specifically, to a multi-mode adaptive air conditioning and fresh air composite control system. Background Technology

[0002] Existing air conditioning and fresh air combined control systems typically feature multiple operating modes, including internal circulation temperature control, total heat recovery fresh air, free cooling, and mixed air temperature control. The controller selects the operating mode based on a comparison of parameters such as indoor carbon dioxide concentration, indoor-outdoor air enthalpy difference, and fresh air temperature with preset thresholds. It also includes a fixed-time protection mechanism during the inverter compressor shutdown and restart phase. This control method can achieve coordinated fresh air supply and energy recovery under relatively stable outdoor meteorological parameters and indoor occupancy conditions. However, in actual operation, outdoor air enthalpy and temperature fluctuate continuously due to cloud cover, sunlight, day-night cycles, and gusts. Indoor carbon dioxide concentration changes with occupancy and the opening and closing of doors and windows. Boundary parameters repeatedly cross the mode switching threshold. Each time the threshold is crossed, the controller performs a switch based on the single comparison result at the current moment. A single switch includes the startup power consumption and mechanical fatigue of the inverter compressor during shutdown and restart, the additional power consumption during the operation of the fresh air valve and return air valve and the transition of each fan speed, and the additional power consumption of the coils during the reconstruction of the temperature and humidity field of the total heat recovery core. The recovery energy required for the load and supply air temperature and humidity to return to the set state is limited. If the boundary conditions reverse within a short period of time after the switch is completed, it is necessary to switch back to the original mode. The fixed-time protection only limits the shortest interval between two starts of the variable frequency compressor. It does not judge whether the duration that the proposed operating mode can be maintained after the switch is sufficient to compensate for the energy cost and equipment wear of a single switch. It also does not adjust according to the type of operating mode, the cumulative number of starts and stops of the variable frequency compressor, and the trend of boundary parameter changes. As a result, in transitional seasons and places with frequent personnel flow, there are phenomena such as short-cycle starts and stops of variable frequency compressors, repeated operation of air valves, and periodic deviations of supply air temperature and humidity from the set state. The total power consumption increases and the wear of moving parts such as variable frequency compressors is accelerated. How to match the benefits obtained from a single mode switch within the expected duration of the proposed operating mode with the cost of the switch itself has become a technical problem that needs to be solved in the actual operation of the air conditioning and fresh air composite control system. In order to solve this technical problem, we provide a multi-mode adaptive air conditioning and fresh air composite control system. Summary of the Invention

[0003] The purpose of this invention is to provide a multi-mode adaptive air conditioning and fresh air composite control system to solve the problems mentioned in the background art.

[0004] To achieve the above objectives, a multi-mode adaptive air conditioning fresh air composite control system is provided, including a fresh air duct, a return air duct, an exhaust air duct, and a supply air duct. A fresh air valve is installed in the fresh air duct, and a return air valve is installed in the return air duct. The fresh air valve and the return air valve are linked together.

[0005] The total heat recovery core and the core bypass ventilation valve are arranged at the intersection of the fresh air duct and the exhaust air duct. The core bypass ventilation valve is used to allow outdoor fresh air to bypass the total heat recovery core.

[0006] Fresh air fan, exhaust fan and circulating fan, refrigeration circuit, including variable frequency compressor, condenser, electronic expansion valve and evaporator connected in sequence, the evaporator is arranged in the air supply duct, sensor group, including outdoor temperature and humidity sensor, return air temperature and humidity sensor, carbon dioxide sensor and supply air temperature and humidity sensor.

[0007] The controller is electrically connected to the fresh air valve, return air valve, core bypass ventilation valve, fresh air fan, exhaust fan, circulating fan, variable frequency compressor, and sensor group. The controller is configured with internal circulation temperature control mode, total heat recovery fresh air mode, free cooling mode, and mixed air temperature control mode, and is configured as follows:

[0008] The enthalpy difference between outdoor air and return air, the carbon dioxide concentration margin and its rate of change are calculated in real time based on the detection values ​​of the sensor group. The total heat exchange efficiency is identified online based on the temperature and humidity of four measuring points: fresh air inlet, fresh air outlet, exhaust air inlet and exhaust air outlet of the total heat recovery core.

[0009] The predicted dwell time is obtained by extrapolating the current values ​​and rate of change of enthalpy difference and carbon dioxide concentration margin to predict the moment when the feasible region of the candidate operating mode is first violated.

[0010] The shortest effective residence time is calculated online based on the ratio of the switching cost of a single mode switch to the steady-state net benefit of the candidate mode. The steady-state net benefit is updated with the identification value of the total heat exchange efficiency. The switching cost includes the energy consumption of a single start-up and shutdown of the variable frequency compressor and the life loss amortized according to the number of allowable start-ups and shutdowns.

[0011] Only when the boundary conditions of the candidate mode are met and the predicted dwell time is not less than the shortest effective dwell time, will the fresh air valve, the core bypass ventilation valve, each fan and the variable frequency compressor be switched to the candidate mode. Otherwise, the current mode will be maintained and the hysteresis bandwidth of the mode switching will be adjusted online by superimposing the product of the rate of change of the boundary variable and the shortest effective dwell time.

[0012] When the carbon dioxide sensor detects a value that meets the hard constraint limit, the controller waives the dwell time determination, controls the fresh air valve to open with a limited opening ramp, and switches to the mixed air temperature control mode.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] This invention estimates the rate of change and extrapolates the boundary variables such as indoor and outdoor enthalpy difference, carbon dioxide concentration margin, and winter frost margin before mode switching. It finds the moment when each boundary condition of the candidate operating mode is first violated and uses the minimum value as the predicted dwell time. At the same time, it combines the additional power consumption and life loss equivalent of the variable frequency compressor start-up and shutdown, the transition power consumption of the air valve and fan, and the reconstruction load and recovery energy consumption of the temperature and humidity field of the total heat recovery core into a switching cost. The shortest effective dwell time is obtained by dividing the switching cost by the time-varying net benefit of the candidate operating mode. Switching is only performed when the predicted dwell time is not less than the shortest effective dwell time. This solves the problem of invalid switching when the boundary is repeatedly crossed when the existing technology triggers switching based on the threshold comparison at the current time.

[0015] The short-cycle start-stop of the variable frequency compressor and the repeated operation of the air valve are suppressed by predictive gating, which reduces the blindness and frequency of mode switching, reduces the power consumption of the system throughout the cycle, and improves the durability of moving parts.

[0016] The reliable total heat transfer efficiency is identified online and the enthalpy difference boundary is corrected on a time-by-time basis, which improves the adaptability of the model decision to core performance degradation and weather condition drift.

[0017] Hygiene hard constraint exemption and ramp-free transition reduce supply air temperature and humidity fluctuations while ensuring indoor air quality and improving the stability of the room's thermal environment. Attached Figure Description

[0018] Figure 1 This is an overall block diagram of the present invention;

[0019] Figure 2 This is a graph showing the online identification results of the total heat transfer efficiency of this invention.

[0020] Figure 3 This is a comparison chart of outdoor air enthalpy on a typical day during the transition season and the switching events of the two control strategy modes according to the present invention.

[0021] Figure 4 This is the timing diagram for the gating of predicted dwell time and shortest effective dwell time in this invention;

[0022] Figure 5 This is a graph showing the relationship between the energy payback time of this invention and the steady-state net profit.

[0023] Figure 6 This is a timing diagram of the frost margin prediction and anti-frost action in the winter heating condition of this invention.

[0024] Figure 1 The meanings of each symbol in the text are as follows:

[0025] 1. Total heat recovery core; 2. Core bypass ventilation valve; 3. Fresh air valve; 4. Return air valve; 5. Fresh air fan; 6. Exhaust fan; 7. Circulating fan; 8. Evaporator; 9. Variable frequency compressor; 10. Condenser; 11. Electronic expansion valve; 12. Outdoor temperature and humidity sensor; 13. Return air temperature and humidity sensor; 14. Carbon dioxide sensor; 15. Supply air temperature and humidity sensor; 16. Controller. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] This invention provides a multi-mode adaptive air conditioning and fresh air combined control system. Please refer to [link / reference]. Figure 1 As shown, it includes a fresh air duct, a return air duct, an exhaust air duct and a supply air duct. A fresh air valve 3 is installed in the fresh air duct and a return air valve 4 is installed in the return air duct. The fresh air valve 3 and the return air valve 4 are linked together.

[0028] The total heat recovery core 1 and the core bypass ventilation valve 2 are arranged at the intersection of the fresh air duct and the exhaust air duct. The core bypass ventilation valve 2 is used to allow outdoor fresh air to bypass the total heat recovery core 1.

[0029] The system includes a fresh air fan 5, an exhaust fan 6, and a circulating fan 7; a refrigeration circuit including a variable frequency compressor 9, a condenser 10, an electronic expansion valve 11, and an evaporator 8 connected in sequence; the evaporator 8 is arranged in the air supply duct; and a sensor group including an outdoor temperature and humidity sensor 12, a return air temperature and humidity sensor 13, a carbon dioxide sensor 14, and an air supply temperature and humidity sensor 15.

[0030] The controller 16 is electrically connected to the fresh air valve 3, return air valve 4, core bypass ventilation valve 2, fresh air fan 5, exhaust fan 6, circulating fan 7, variable frequency compressor 9, and sensor group, respectively. The controller 16 is configured with an internal circulation temperature control mode, a total heat recovery fresh air mode, a free cooling mode, and a mixed air temperature control mode, and is configured as follows:

[0031] The enthalpy difference between outdoor air and return air, the carbon dioxide concentration margin and its rate of change are calculated in real time based on the detection values ​​of the sensor group. The total heat exchange efficiency is identified online based on the temperature and humidity of four measuring points: fresh air inlet, fresh air outlet, exhaust air inlet and exhaust air outlet of the total heat recovery core 1.

[0032] The predicted dwell time is obtained by extrapolating the current values ​​and rate of change of enthalpy difference and carbon dioxide concentration margin to predict the moment when the feasible region of the candidate operating mode is first violated.

[0033] The shortest effective residence time is calculated online based on the ratio of the switching cost of a single mode switch to the steady-state net benefit of the candidate mode. The steady-state net benefit is updated with the identification value of the total heat exchange efficiency. The switching cost includes the energy consumption of a single start-up and shutdown of the variable frequency compressor 9 and the life loss amortized according to the number of allowable start-ups and shutdowns.

[0034] Only when the boundary conditions of the candidate mode are met and the predicted dwell time is not less than the shortest effective dwell time, the fresh air valve 3, the core bypass ventilation valve 2, each fan and the variable frequency compressor 9 are switched to the candidate mode. Otherwise, the current mode is maintained and the hysteresis bandwidth of the mode switching is adjusted online by superimposing the product of the rate of change of the boundary variable and the shortest effective dwell time.

[0035] When the carbon dioxide sensor 14 detects a value that reaches the hard constraint limit, the controller 16 exempts the dwell time determination, controls the fresh air valve 3 to open with a limited opening ramp and switch to the mixed air temperature control mode.

[0036] In this invention, temperature sensors and relative humidity sensors are respectively installed at the fresh air inlet, fresh air outlet, exhaust air inlet, and exhaust air outlet of the total heat recovery core 1. The four measuring points are sequentially labeled as the first measuring point, the second measuring point, the third measuring point, and the fourth measuring point. The controller 16 operates at a sampling period of... Temperature and relative humidity were collected at four measurement points, with a sampling period of [missing information]. Taking values ​​between 10s and 30s, the controller 16 first calculates the moisture content from the relative humidity for any measuring point. ( Moisture content according to

[0037]

[0038] Calculate, where For measuring points Moisture content, For measuring points relative humidity, For temperature The partial pressure of saturated water vapor under certain conditions is determined by the relationship between the partial pressures of saturated water vapor. Given the local atmospheric pressure, controller 16 then adjusts the enthalpy relationship of moist air.

[0039]

[0040] Calculate the enthalpy of air at four measuring points. , , and ,in For the enthalpy of the fresh air intake, The enthalpy of the fresh air outlet. The enthalpy of the exhaust inlet air. To measure the enthalpy of the exhaust air, while collecting temperature and humidity data, controller 16 reads the speed feedback and measured electrical power of the fresh air fan 5 and the exhaust fan 6, and calculates the fresh air mass flow rate from the speed and air volume calibration relationship. and exhaust mass flow rate The controller 16 is set with a steady-state identification window. When both the fresh air fan 5 and the exhaust fan 6 are running, the change in the opening of the fresh air valve 3 is less than 2%, the speed fluctuation of both fans is less than 2% of the rated speed, and the absolute value of the rate of change of the difference between the enthalpy of the fresh air inlet and the enthalpy of the exhaust air inlet meets the following conditions:

[0041]

[0042] and duration ,in Pick , After 300 seconds, controller 16 determines that the total heat recovery core 1 is in a steady-state heat transfer process and opens the identification window. The purpose of the steady-state identification window is to eliminate the contamination of efficiency identification by the mode switching transition process and meteorological abrupt changes, so that the identification result reflects the steady-state heat transfer capacity of the total heat recovery core 1. Within the steady-state identification window, controller 16 uses a method with a forgetting factor. The recursive least squares method is used to identify the total heat transfer efficiency online, and the heat transfer observations at each sampling time are written in linear form.

[0043]

[0044] In the formula This is the sampling time sequence number. The absolute value of the actual enthalpy difference of the fresh air flowing through the total heat recovery core 1. This represents the absolute value of the inlet enthalpy difference between the fresh air and exhaust air. To observe the residuals, For the total heat transfer efficiency to be identified, recursively update according to

[0045]

[0046]

[0047]

[0048] Execution, in the formula To identify gain, To estimate covariance, the forgetting factor A forgetting factor, with a value between 0.95 and 0.99, ensures that the identification results track the slow degradation caused by filter dust accumulation and membrane aging, while suppressing sensor noise at a single moment. That is, the first The total heat exchange efficiency identification value at any given time; the controller 16 is rated at the nameplate total heat exchange efficiency at the time of manufacture. As The initial value of .

[0049] After each iteration, controller 16 performs a confidence level determination, as follows:

[0050] Require Between 0.40 and 0.95, controller 16 estimates the residual sequence recursively. Standard deviation And require Less than the preset value corresponding to the enthalpy measurement uncertainty Controller 16

[0051]

[0052] Calculate the energy non-closure degree of the two airflows And require When the value is less than 0.10 and all three conditions are met, controller 16 will... Confirmed as a reliable total heat transfer efficiency If any condition is not met, controller 16 discards the current observation and does not update the reliable total heat transfer efficiency.

[0053] Reliable total heat transfer efficiency After acquisition, controller 16 immediately corrects the enthalpy difference boundary of the total heat recovery fresh air mode using the reliable total heat exchange efficiency. When the total heat recovery fresh air mode is put into operation, the energy recovered by the total heat recovery core 1 from the exhaust air per unit time is... When this portion of energy is handled by the refrigeration circuit, the corresponding compressor power saving is... In the formula, COP is the performance coefficient of the refrigeration circuit. When the total heat recovery core 1 is engaged, wind resistance is generated. The controller 16 uses the difference between the sum of the measured electrical power of the fresh air fan 5 and the exhaust fan 6 in the total heat recovery engaged state and the core bypass state. This represents the additional fan power of the total heat recovery fresh air mode. Therefore, the steady-state net benefit of the total heat recovery fresh air mode relative to the mixed air temperature control mode is...

[0054]

[0055] Setting the steady-state net return to zero yields the enthalpy boundary of profit and loss.

[0056]

[0057] For the critical indoor-outdoor enthalpy difference where the total heat recovery fresh air mode transitions from energy-saving to energy-consuming compared to the mixed air temperature control mode, controller 16 will... As a feasible enthalpy condition for the total heat recovery fresh air mode, when the reliable total heat exchange efficiency is... When the enthalpy difference decreases due to dust accumulation on the filter element, the enthalpy difference boundary is... As the resistance of the total heat recovery fresh air mode increases, the feasible enthalpy range shrinks. This is because an increase in the air resistance of the total heat recovery core 1 leads to a decrease in the power consumption of the additional fan. When it rises, the enthalpy difference boundary The synchronous increase ensures that the feasible region of the model is consistent with the actual heat transfer and wind resistance conditions of the total heat recovery core 1.

[0058] Controller 16 executes according to the above result branch in each sampling cycle. When the steady-state identification window is not satisfied, controller 16 freezes the recursive least squares update and maintains the reliable total heat transfer efficiency. and the boundary of profit and loss enthalpy difference The controller 16 retains the previous reliable total heat transfer efficiency when the confidence level fails to pass the assessment and a historical reliable value exists. When the confidence level fails to pass the assessment and no historical reliable value exists, the controller 16 uses the previous reliable total heat transfer efficiency. As a conservative and reliable efficiency measure, and issuing sensor self-check prompts, when the steady-state net gain... Greater than zero and Greater than the profit and loss enthalpy boundary At that time, controller 16 allows the total heat recovery fresh air mode to be included as a candidate mode in the dwell time determination, when the steady-state net benefit When the temperature is less than or equal to zero and the system is not operating in total heat recovery fresh air mode, controller 16 is prohibited from switching to total heat recovery fresh air mode and maintains mixed air temperature control mode or internal circulation temperature control mode. When the system is already operating in total heat recovery fresh air mode and the steady-state net benefit is... The duration less than or equal to zero reaches the exit delay. ,in After 180 seconds, controller 16 exits the total heat recovery fresh air mode and switches to the mixed air temperature control mode, while simultaneously opening the core bypass ventilation valve 2. The system then re-enters the system, requiring steady-state net profit to recover to the re-entry threshold. above, A hysteresis of 0.05kW is used, with the difference between the exit threshold and the re-entry threshold forming a hysteresis, to prevent frequent mode switching in critical states.

[0059] The controller 16 is adjusted to differentiate the reasons for performance degradation under winter heating conditions, when the reliable total heat transfer efficiency is... The temperature drop exceeded 0.10 within 10 minutes and the temperature at the fourth measuring point was... air dew point temperature at the third measuring point When the temperature difference is less than 2°C, the controller 16 determines that micro-frost has appeared on the total heat recovery core 1. At this time, the controller 16 does not include the efficiency decrease in the dust accumulation decay and activates the ventilation valve 2 next to the core to perform anti-frost operation. After the frost is removed and the reliable total heat exchange efficiency recovers, the enthalpy difference boundary automatically recovers. When the decay rate... When the air quality flow rate exceeds 0.20 and does not exhibit micro-frost characteristics, the controller 16 issues a filter cleaning or replacement prompt. When the fan speed is adjusted, the controller 16 recalculates the enthalpy difference boundary based on the changed fresh air mass flow rate. The larger the fresh air mass flow rate, the smaller the enthalpy difference boundary, which correspondingly expands the feasible enthalpy range of the total heat recovery fresh air mode under the condition of large fresh air volume. Through the above steps, the input and output of the total heat recovery fresh air mode are determined at each moment based on the currently measurable heat exchange capacity and wind resistance cost of the total heat recovery core 1. When the filter element is dusty, the membrane material is aging, or micro-frost occurs, resulting in insufficient recovered energy to compensate for the additional fan power, the total heat recovery fresh air mode is automatically stopped. It is automatically restarted after the heat exchange capacity is restored, and provides a quantitative trigger basis for filter element maintenance. The temperature and humidity data of the four measuring points are used simultaneously for total heat exchange efficiency identification and frosting determination.

[0060] Controller 16 in reliable total heat transfer efficiency After the update is completed, the steady-state net benefit of the total heat recovery fresh air mode is calculated. Then, using the steady-state net benefit as input, the predicted residence time of the candidate operating modes is calculated. The amount of heat recovered by the total heat recovery core from the exhaust air per unit time is calculated as follows:

[0061]

[0062] Calculate, where The fresh air mass flow rate is calculated from the relationship between the fresh air fan speed and the air volume calibration. The reliable total heat transfer efficiency is confirmed by a confidence level determination. For the enthalpy of the fresh air intake, The enthalpy of the exhaust inlet air is used, and the absolute value of the enthalpy difference is taken so that the same formula holds true under both cooling and heating conditions. Under cooling conditions... This indicates that the fresh air is cooled by the exhaust air during heating operation. This indicates that the fresh air is heated by the exhaust air, and the heat recovery rate is... The power saving of the compressor when the refrigeration circuit handles the load is calculated as follows: In the formula, COP is the coefficient of performance of the refrigeration circuit under the current operating conditions. The refrigeration performance coefficient value is taken for the refrigeration operation, and the heat pump heating performance coefficient value is taken for the heating operation. After the total heat recovery core 1 is put into operation, wind resistance is generated in both the fresh air flow channel and the exhaust air flow channel. The controller 16 collects the power of the fresh air fan 5 under the total heat recovery operation state. And exhaust fan 6 power And the power of the fresh air fan 5 in the core bypass state And exhaust fan 6 power ,according to

[0063]

[0064] Calculate the additional fan power for the total heat recovery fresh air mode. When the unit is not equipped with fan power measurement, the additional fan power is given by the calibration table relationship between fan speed and core resistance. Therefore, the steady-state net benefit of the total heat recovery fresh air mode relative to the mixed air temperature control mode is calculated according to...

[0065]

[0066] After calculating and obtaining the steady-state net benefit, the controller 16 quantifies the direction of change of the steady-state net benefit. When the reliable total heat transfer efficiency is... decay to At that time, the decrease in steady-state net income is At the same time, dust accumulation on the filter element increases the air resistance of the filter element, adding to the power consumption of the fan. As the temperature rises, the steady-state net benefit decreases simultaneously from two directions: reduced heat exchange benefit and increased fan cost. Controller 16 will adjust the steady-state net benefit... As input to the unit time benefit term in the calculation of the shortest effective stay time, and Together Together, these are necessary conditions for the feasibility of a total heat recovery fresh air mode, among which... The enthalpy difference boundary is used to ensure that the profit and loss assessment of the total heat recovery fresh air mode remains consistent with the current heat exchange capacity and current wind resistance cost of the total heat recovery core 1 at every moment.

[0067] After determining the steady-state net benefit, controller 16 further determines whether the benefit of the candidate operating mode can be sustained. Controller 16 sets enthalpy difference boundary variables, carbon dioxide margin boundary variables, and frost margin boundary variables. The enthalpy difference boundary variable is denoted as... The boundary variable for the carbon dioxide balance is denoted as ,in Indoor carbon dioxide concentration, The setpoint for carbon dioxide concentration, and the boundary variable for frost margin, are denoted as... ,in The temperature at the fourth measuring point. The air dew point temperature at the third measuring point is denoted as [missing information]. All three types of boundary variables are uniformly denoted as [missing information]. subscript Pick , , .

[0068] Controller 16 independently performs weighted recursive least squares estimation for each boundary variable within a sliding time window, the sliding time window containing At the sampling time, the first sampling point within the window The relative time corresponding to each sampling moment is The regression vector is taken The parameter vector to be estimated is taken ,in For the intercept term, The coefficient of the linear term, The coefficients of the quadratic term are denoted as , and the exponential weighted coefficients are denoted as . Furthermore, values ​​between 0.95 and 0.99 are used to give greater weight to observations at closer times, and the recursive process follows...

[0069]

[0070]

[0071]

[0072] Execution, in the formula For recursive gain, Let covariance be the parameter. As the identity matrix, controller 16 extracts the first-order rate of change from the parameter vector at the end of the sliding time window. and second-order acceleration The uncertainty of the first-order rate of change is extracted from the parametric covariance matrix. ,in The controller 16 takes a one-sided upper bound for the standard deviation of the fitted residuals within the window and for the first-order rate of change tending toward the direction of violating the boundary conditions. As the extrapolated rate of change, the confidence coefficient Taking 1.645 as the 95% confidence level for one side, the second-order acceleration is retained for extrapolation when it points towards the boundary conditions, and is set to zero when it deviates from the boundary conditions. This yields the conservative extrapolation trajectory of the boundary variables.

[0073]

[0074] In the formula The current value of the boundary variable. The predicted time is from the current moment forward.

[0075] Controller 16 presets a feasible region for each candidate operating mode. The feasible region consists of the enthalpy condition, carbon dioxide condition, and frosting condition that the mode must satisfy, expressed as a boundary condition function. express, Indicating candidate operating modes, controller 16 solves the equations for each boundary condition. The smallest non-negative real root is obtained, and the boundary conditions are derived. Candidate operating modes The moment of the first violation Taking the enthalpy condition of the free cooling mode as an example, the free cooling mode requires... ,in By incorporating a margin for the enthalpy of the economizer and taking values ​​between 0.5 kJ / kg and 1.5 kJ / kg, and substituting these values ​​into the extrapolation trajectory, we obtain the equation. ,when First violation time

[0076]

[0077] Take the smallest non-negative real root, when Press at time The calculation shows that if the square root is negative or the resulting root is negative, it indicates that the boundary condition is not violated in the extrapolated time domain. The time of the first violation is taken from the predicted time domain. Predicting the time domain Take 60 to 90 minutes.

[0078] For the carbon dioxide boundary variable, controller 16 does not use polynomial extrapolation but instead uses a room carbon dioxide mass balance model to calculate the time of the first violation. The net room volume is denoted as... The volume and air volume of fresh air are recorded as follows: Outdoor carbon dioxide concentration is recorded as The amount of carbon dioxide generated per person is recorded as And take a value between 0.015 m³ / (h·person) and 0.020 m³ / (h·person), the rated number of people is recorded as The mass balance equation is Its full-capacity steady-state concentration is The controller 16 is configured with two conservative ascent rates: one for personnel step ascent and one for conservative ascent rate. The calculation represents the most unfavorable rate of increase in carbon dioxide concentration when the rated number of passengers suddenly reaches full capacity, without considering fresh air dilution. The historical rate of increase during the same period is obtained by storing historical concentration change rates by controller 16 according to week number and intraday time period, and taking the 90th percentile, denoted as . The controller 16 takes the larger of the conservative step rate of increase in personnel and the historical rate of increase during the same period as the rate of increase in carbon dioxide concentration. When the number of people in the room is measured, the measured number of people in the room is used instead of the rated number of people. Based on this, the controller 16 directly solves the mass balance equation to obtain the carbon dioxide concentration limit. The moment of the first violation

[0079]

[0080] In the formula The current value of carbon dioxide concentration is the steady-state concentration at full capacity. Less than or equal to the limit The time indicates that the fresh air volume is sufficient to dilute the full load, and the first violation time is taken from the predicted time domain. When the current value It is greater than or equal to the limit. When the first violation occurs, the time is set to 0 and the process transitions to a hard constraint exemption procedure. Controller 16 will then select the candidate operating mode. The minimum value among all the first violations of the boundary conditions is determined as the predicted dwell time.

[0081]

[0082] The predicted dwell time means the longest time that the candidate operating mode can continuously satisfy the feasible domain of the model under the current meteorological and personnel trends. When the number of samples in the sliding time window is insufficient after the controller 16 is turned on, the first-order rate of change and the second-order acceleration are set to zero. The carbon dioxide boundary variable is calculated using the conservative step rate of increase of personnel. When the standard deviation of the fitting residual of any boundary condition exceeds the preset value, the controller 16 uses the unfavorable quantile of the rate of change of the same period in history to extrapolate the boundary variable.

[0083] After obtaining the predicted dwell time, controller 16 will predict the dwell time. With the shortest effective stay In comparison, the shortest effective dwell time is calculated by dividing the cost of a single switch by the net benefit including steady-state gains. The net return per unit time for the candidate operating modes, including those included, is obtained when When, the candidate running mode is allowed to enter the switching execution, when At this time, controller 16 maintains the current operating mode and abandons this switch.

[0084] Through the above steps, the mode switching decision is based on two calculable quantities: the magnitude of the benefit and the duration of the benefit. The quadratic extrapolation captures the trend turning point of outdoor enthalpy, and the one-sided confidence upper bound avoids overly optimistic trend prediction. The carbon dioxide mass balance model can still give the moment of exceeding the limit when the personnel suddenly reach full capacity without relying on the recurrence of historical data. The minimum value of multiple boundary conditions ensures that the stay will terminate when any constraint fails, thus maintaining the continuous operation of the model when the weather is stable and suppressing ineffective switching when the weather and personnel are hovering near the boundary.

[0085] After determining the steady-state net benefit of the candidate operating mode, controller 16 further calculates the switching cost incurred in a mode switch, which consists of the sum of starting additional power consumption, life loss equivalent, damper and fan transition additional power consumption, core temperature and humidity field reconstruction additional coil load, and recovery energy consumption. Controller 16 first determines the difference in actuator action between the candidate operating mode and the current operating mode and sets two indicators. When the candidate operating mode requires the variable frequency compressor 9 to undergo a shutdown and restart process, the compressor start / stop indicator... Take 1, when the variable frequency compressor 9 only changes its operating frequency while maintaining power supply, the compressor start / stop indicator value is 1. Set to 0, when the candidate operating mode requires the total heat recovery core 1 to be engaged from the bypass state, the core engagement indicator is set to 0. Take 1, and for the remaining switching paths, the core input indicator quantity. Set to 0, where the first item is the additional power consumption during startup. After the variable frequency compressor 9 stops, the pressure on the high and low pressure sides of the refrigeration circuit gradually balances. When restarting, the starting current reaches several times the rated current, and the actual performance coefficient is lower than the steady-state performance coefficient during the period when the high and low pressures of the refrigeration circuit are re-established after startup. The controller 16 divides the additional power consumption during startup into a current surge stage and an inefficient rebuild stage. The power consumption in the current surge stage is calculated as follows: Calculation, where The average excess power during the duration of the starting current surge. The duration of the current surge is taken as 1 to 5 seconds, and the power consumption of the inefficient rebuilding section is calculated as follows: Calculation, where The average excess power during the pressure reconstruction period. To determine the duration of the pressure reconstruction period, which is set to 180 to 300 seconds, additional power consumption is activated.

[0086]

[0087] The controller 16 records the power curve of the restart period after each actual restart of the variable frequency compressor 9 and integrates the excess power. It updates the average excess power and the duration of the pressure rebuild period in a sliding average manner, so that the additional power consumption during startup can be automatically corrected as the variable frequency compressor 9 ages and the refrigerant quantity changes.

[0088] The second component is the equivalent of life loss. The life loss equivalent represents the cost, expressed in energy units, of the mechanical and thermal fatigue caused by the start-stop cycle to the moving bearings, windings, and seals of the variable frequency compressor 9. The controller 16 records the cumulative number of start-stop cycles of the variable frequency compressor 9 in a non-volatile memory. The variable frequency compressor 9 is not lost after power failure and is reset after maintenance or replacement. The total number of permissible start-stop cycles is recorded as follows: The purchase and replacement cost of the inverter compressor 9 is recorded as the data written from the machine model test bench. Electricity price is recorded as The basic amortization monetary cost for a single start-stop cycle is ,according to The equivalent of basic life loss is calculated.

[0089]

[0090] Considering that the marginal fatigue loss of the variable frequency compressor 9 increases with each start-stop operation near the end of its lifespan, and that the lubricating film cannot be rebuilt in time when the start-stop frequency is too high, the controller 16 applies a weighting factor to the basic lifespan loss equivalent. The start-stop frequency per unit time within the near sliding statistical window is denoted as... The manufacturer-permitted frequency of continuous start-stop operations is recorded as follows: Weighting factors are calculated as follows:

[0091]

[0092] Calculate, where and These are weighting coefficients, each taking values ​​between 1.0 and 0.5 and 1.0 respectively. The terminal acceleration index is set to a value between 2 and 3, and the lifetime loss equivalent is calculated as follows:

[0093]

[0094] Calculations show that the equivalent life loss increases with the increase of the proportion of cumulative start-stop times to the total number of allowable start-stop times, and also increases with the start-stop frequency per unit time exceeding the allowable continuous start-stop frequency.

[0095] The third item is the additional power consumption during the transition of the air valve and fan. The duration of the transition state during mode switching is denoted as During the transition, the fresh air valve 3 and return air valve 4 operate at a speed-limited ramp, and the fresh air fan 5, exhaust fan 6, and circulating fan 7 deviate from the steady-state high-efficiency operating point. The additional power consumption during the transition is calculated according to...

[0096]

[0097] Calculate, where The sum of the measured electrical power of each fan in the transition state is the average excess of the fan power in the steady state of the candidate operating mode relative to the fan power in the candidate operating mode. It is given by looking up the table based on the fan frequency conversion curve and the valve stroke calibration relationship.

[0098] The fourth sub-item is the additional coil load for core temperature and humidity field reconstruction. When the total heat recovery core 1 is put into operation from the bypass state, the temperature and moisture content of the core material need a rebuilding time to transition from the idle state to the heat transfer steady state. During the rebuilding period, the total heat transfer efficiency decreases from the initial efficiency. The reliable total heat transfer efficiency approaches the exponential law. The efficiency expression for any time within the reconstruction period is: ,in The time constant for reconstructing the temperature and humidity field of the total heat recovery core 1 is taken as 60s to 90s. The load that is not recovered and falls onto the coil during the reconstruction period is integrated and then...

[0099]

[0100] Calculate, where For fresh air quality flow rate, For the enthalpy of the fresh air intake, The enthalpy of the exhaust inlet air is given; COP is the coefficient of performance of the refrigeration circuit under current operating conditions; and the initial efficiency of the total heat recovery core 1 after long-term bypass suspension is given. Set to 0, initial efficiency when switching from mixed-air temperature control mode for a short period of time. Take 0.5 times the reliable total heat transfer efficiency;

[0101] The fifth item is energy recovery. Transitional state internal air supply enthalpy Relative setting of air supply enthalpy The deviation varies with the supply air mass flow rate Entering the room creates a cumulative energy imbalance

[0102]

[0103] Controller 16 treats the room as a first-order thermal inertial object, and the equivalent heat capacity of the room is denoted as... The equivalent thermal inertia time constant of the room is denoted as The initial deviation of room temperature caused by the switch is The energy consumption for restoring the deviated energy to the set state is calculated according to...

[0104]

[0105] After calculating and obtaining the five sub-items, controller 16 synthesizes candidate operating modes based on the differences in actuator actions. Switching cost

[0106]

[0107] When the switching path does not include the shutdown and restart of the variable frequency compressor 9, the additional power consumption and life loss equivalent are both taken as 0. When the switching path does not include the operation of the total heat recovery core 1, the additional coil load for the reconstruction of the core temperature and humidity field is taken as 0. For the shutdown of the variable frequency compressor 9 caused by switching to the free cooling mode, the controller 16 will pre-calculate the additional power consumption and life loss equivalent of the restart corresponding to the shutdown into the switching cost, so as to avoid postponing the start-stop fatigue cost to the next decision.

[0108] After obtaining the switching cost, controller 16 divides the switching cost by the steady-state net gain of the candidate operating mode. The minimum effective dwell time is calculated by adding the energy payback period and the comfort recovery period. The comfort recovery period is calculated as the initial room temperature deviation decays to half the width of the comfort zone using first-order inertia. Time required, when Press at time

[0109]

[0110] Calculate, when The comfort recovery time is set to 0, therefore the shortest effective dwell time is calculated as follows:

[0111]

[0112] Calculate the steady-state net income. When the minimum effective dwell time is less than or equal to 0, the minimum effective dwell time is set to infinity and switching to the candidate running mode is prohibited.

[0113] Taking the transitional season's free cooling mode as an example, the purchase and replacement cost of the variable frequency compressor 9 is taken as 1500 yuan, the total number of allowable start-stop cycles is taken as 100,000, the electricity price is taken as 0.6 yuan / (kW·h), the basic lifespan loss equivalent is 90kJ, the current surge power consumption is taken as 6kJ, the average excess power during the pressure reconstruction period is taken as 0.4kW and the pressure reconstruction period duration is taken as 240s, the additional power consumption during startup is 102kJ, the additional power consumption during the transition of the air valve and fan is 3kJ, and the recovery energy consumption is 5kJ. Since the free cooling mode does not involve the total heat recovery core 1, the additional coil load for core temperature and humidity field reconstruction is taken as 0. Initial operation... The weighting factor is approximately 1, and the total switching cost is approximately 206kJ. When the steady-state net benefit of the free cooling mode is 0.05kW, the energy payback time is approximately 4120s, or 69min. When the cumulative number of start-stops reaches 0.8 times the total number of allowable start-stops and the start-stop frequency per unit time reaches 8 times / h, the weighting factor increases to 1.85, the life loss equivalent increases to 167kJ, and the shortest effective residence time is correspondingly extended. When the start-stop frequency per unit time exceeds the allowable continuous start-stop frequency, the controller 16, in addition to increasing the life loss equivalent, also limits the minimum start-stop interval of the variable frequency compressor 9 and issues a maintenance reminder.

[0114] Through the above steps, the cost of mode switching is changed from fixed-time protection to energy account calculated item by item according to the actuator action path and varying with the degree of equipment aging and the recent frequency of start-ups and shutdowns. The shortest effective residence time varies depending on the operating mode. The free cooling mode has a longer shortest effective residence time because it includes the start-stop provision of the variable frequency compressor 9. The mixed air temperature control mode that only adjusts the fresh air ratio has a shorter shortest effective residence time because it does not start or stop the variable frequency compressor 9. After comparing the switching cost with the predicted residence time, ineffective switching near the boundary is suppressed from both the energy recovery and fatigue life dimensions.

[0115] Controller 16 operates a hysteresis bandwidth tuning loop in parallel outside the residence time gating loop. Controller 16 sets an entry line and an exit line for each boundary variable. The entry line is the boundary variable value that allows the current operating mode to switch to a candidate operating mode, and the exit line is the boundary variable value that allows exiting during the operation of the candidate operating mode. The width of the interval between the entry and exit lines is the hysteresis bandwidth. When the boundary variable is within the hysteresis bandwidth, controller 16 maintains the current operating mode. The hysteresis bandwidth is set separately for each boundary variable, including the enthalpy difference boundary variable. The hysteresis bandwidth is denoted as carbon dioxide balance boundary variables The hysteresis bandwidth is denoted as Frost margin boundary variables The hysteresis bandwidth is denoted as The three types of hysteresis bandwidth are uniformly denoted as , Pick , , .

[0116] Controller 16 during bandwidth update cycle Internal reading of first-order rate of change and the shortest effective dwell time of candidate operating modes The first term of the hysteresis bandwidth is determined by the travel-time constraint, and the time required for the boundary variable to travel through the hysteresis bandwidth at the current first-order rate of change is... Controller 16 requires the travel time to be no less than the minimum effective dwell time, i.e. Thus, the trend term value of the hysteresis bandwidth is obtained. Under current weather or human trends, even if a candidate operating mode is granted entry permission, it will not be crossed in reverse by the boundary variables within the shortest effective residence time.

[0117] The second term of the hysteresis bandwidth is the noise margin. Controller 16 measures boundary variables within the bandwidth statistics window. of Calculate the standard deviation of the recent time period for each sample value.

[0118]

[0119] In the formula The mean of the boundary variables within the bandwidth statistical window is used, with a window duration of 30 minutes. The recent time period standard deviation includes sensor measurement noise and natural outdoor weather fluctuations. Controller 16 takes a noise margin proportional to the recent time period standard deviation. Noise margin factor Take a value between 1.5 and 2, and then the hysteresis bandwidth setting value is...

[0120]

[0121] The controller 16 calculates and sets the hysteresis bandwidth setting value to the preset lower bandwidth limit. and preset bandwidth limit Limiting output between, i.e.

[0122]

[0123] The purpose of the limiting is to ensure that when the first-order rate of change increases abnormally, the hysteresis bandwidth does not exceed the upper limit of the bandwidth and loses its responsiveness, while when the first-order rate of change approaches zero, the hysteresis bandwidth does not fall below the lower limit of the bandwidth and retains the ability to suppress measurement noise. The controller 16 applies a bandwidth change rate limit to the difference between the hysteresis bandwidths of two adjacent outputs, so that the hysteresis bandwidth is updated in a ramp manner without generating a step.

[0124] When the first rate of change When the trend term is 0, the hysteresis bandwidth degenerates into noise margin and is taken as the lower limit of bandwidth after limiting. The mode switching maintains sensitivity to the slow drift of boundary variables. When the steady-state net benefit of the candidate operating mode is less than or equal to zero, making the shortest effective dwell time infinite, the controller 16 closes the entry permission of the candidate operating mode and keeps the current hysteresis bandwidth unchanged.

[0125] After obtaining the hysteresis bandwidth, controller 16 performs a switching decision based on the enthalpy condition of the free cooling mode, and switches to the appropriate line. Cut out the line ,in To provide an enthalpy margin for the economizer, when the boundary variable crosses the cut-in line from top to bottom and the dwell time gating is met, the controller 16 switches to the free cooling mode. During the operation of the free cooling mode, the controller 16 is only allowed to exit when the boundary variable crosses the cut-out line from bottom to top. The free cooling mode is maintained when the boundary variable travels back and forth between the cut-in line and the cut-out line.

[0126] In the transitional season example, the first rate of change is taken as... The shortest effective residence time for the free cooling mode is 69 minutes, and the trend term is set to [value missing]. The standard deviation of the recent period is taken as The noise margin factor is taken as 1.5, and the noise margin is... Hysteresis bandwidth setting value The limited range is taken to The output hysteresis bandwidth is When the weather is stable, the first-order rate of change decreases to The hysteresis bandwidth setting value was reduced to And the lower limit of bandwidth is obtained after amplitude limiting. The mode switching restores the response to slow changes in outdoor enthalpy.

[0127] Controller 16 simultaneously accumulates the excess integral during the period when the dwell time determination is not met and the current operating mode is maintained. The excess integral of carbon dioxide concentration is calculated as follows:

[0128]

[0129] Calculate, where Indoor carbon dioxide concentration, For carbon dioxide concentration limits, the integral for exceeding the temperature limit is calculated as follows:

[0130]

[0131] Calculate, where Return air temperature, Set the temperature value. For the comfort zone half-width, humidity exceeding the limit is integrated according to...

[0132]

[0133] Calculate, where The relative humidity of the return air. Set the relative humidity value. To determine the relative humidity tolerance, controller 16 divides the three types of out-of-limit integrals by their respective limits and then assigns them weights accordingly. , , Synthetic normalized overlimit integral

[0134]

[0135] Normalized inverse integral The unit is min, representing the accumulated indoor air quality and comfort violation time for the gated system to maintain the current operating mode. The violation score is only accumulated during the period when the dwell time judgment is not met and the switch is abandoned. It is not accumulated during the normal operation of the candidate operating mode. When the normalized violation score exceeds the violation score threshold... At that time, controller 16 pressed

[0136]

[0137] Inversely narrowing the hysteresis bandwidth, where The narrowing coefficients are calibrated according to the dimensions of the boundary variables. Reverse narrowing brings the cut-in line and the cut-out line closer to each other, making it easier for candidate operating modes to obtain cut-in permission in subsequent sampling periods. When the indoor carbon dioxide concentration reaches the hard limit value, the controller 16 enters the hard constraint exemption process. The over-limit integral is cleared to zero after the controller 16 performs switching or the over-limit state is eliminated and the continuous reset time is maintained. This avoids the historical over-limit from suppressing the hysteresis bandwidth for a long time. The hysteresis bandwidth is automatically widened by the shortest effective residence time to suppress mode ping-pong switching when the weather fluctuates drastically and the switching cost is high. When the gate maintenance causes the indoor air quality or comfort to continuously violate the rules, the normalized over-limit integral is automatically narrowed to restore the mode response. The widening and narrowing form a closed-loop self-balancing. The noise margin is taken according to the standard deviation of the on-site measurement to make the hysteresis bandwidth adapt to the sensor installation environment.

[0138] While executing residence time gating, controller 16 performs parallel hard constraint determination of hygiene indicators. The hard constraint determination has higher priority than residence time gating. The hard constraint limit consists of a hard limit for carbon dioxide concentration and a minimum fresh air volume. Controller 16 first calculates the minimum fresh air volume that meets the room's hygiene requirements. The minimum fresh air volume is calculated using both the number of people method and the air change rate method, and the larger value is taken.

[0139]

[0140] In the formula The minimum fresh air volume for a single person is taken as 30 m³ / (h·person). Design the number of people in the room. The minimum air exchange rate is set to 0.5 times / h. To determine the room's net volume, controller 16 converts the minimum fresh air volume into the minimum opening of fresh air valve 3 by referring to the fresh air valve 3 opening and the fresh air volume calibration curve. The opening degree of fresh air valve 3 is expressed as the fresh air ratio, and the sum of the opening degree of fresh air valve 3 and the opening degree of return air valve 4 is always equal to 1, that is, the opening degree of fresh air valve 3 is... Return air valve 4 opening degree is .

[0141] Controller 16 further calculates the required fresh air volume based on the carbon dioxide mass balance to maintain the carbon dioxide concentration setpoint. Steady-state demand for fresh air volume according to

[0142]

[0143] Calculate, where The carbon dioxide emission per person is taken as 0.018 m³ / (h·person). For the number of people in the room, if the actual number of people in the room is measured, the measured value shall be used; if the actual number of people in the room is not measured, the rated number of people shall be used. , Take 1000 ppm, To determine the outdoor carbon dioxide concentration, the required fresh air volume is obtained by pressing button 16 on the controller.

[0144]

[0145] Calculate the opening degree of the target fresh air valve 3, where This refers to the total air supply volume. This means that the result will be limited to the minimum opening degree of fresh air valve 3 and 1.

[0146] Two hard constraint trigger conditions are set, the first being the current value of indoor carbon dioxide concentration. Reaching the hard limit for carbon dioxide concentration , The value is 1500ppm. The second value is the actual fresh air volume given by the fresh air fan speed 5 RPM model. Below the minimum fresh air volume If any one of the conditions is met and the de-shaking time continues... and If the time is between 30s and 60s, the controller 16 will be exempted from the dwell time gating and enter the hard constraint response. The de-jitter time is used to eliminate false triggers caused by people passing by the sensor and single sampling anomalies.

[0147] Upon entering a hard constraint response, controller 16 does not allow the fresh air valve 3 to perform a step action. The fresh air valve 3 opens at a rate-limited ramp, and the valve position change rate is...

[0148]

[0149] Calculate, where The full stroke time of fresh air valve 3 is taken as 30s to 60s. The allowable valve position change per second, during the ramp process, the opening degree of fresh air valve 3 is as follows: Changes, among which The opening degree of fresh air valve 3 at the start of the ramp, and the return air valve 4 at... When the system shuts down in tandem, the fresh air fan 5 and the exhaust fan 6 simultaneously perform speed feedforward compensation to ensure the total air volume is adjusted. Keep it constant.

[0150] As the fresh air valve 3 opens, the controller 16 adjusts the fresh air load feedforward of the variable frequency compressor 9. The feedforward amount of the compressor power corresponding to the increased fresh air load is adjusted according to...

[0151]

[0152] Calculate, where For fresh air quality flow rate, For the enthalpy of the fresh air intake, The enthalpy of the exhaust inlet air is given, and the Coefficient of Performance (COP) is the performance coefficient of the refrigeration circuit under the current operating conditions. The operating frequency of the variable frequency compressor 9 and the opening degree of the electronic expansion valve 11 are adjusted by adding supply air temperature feedback correction to the power feedforward, so that the supply air temperature deviation does not exceed the comfort zone half-width described in Section 10. .

[0153] In terms of operating mode selection, controller 16 prioritizes switching to the mixed air temperature control mode. In the mixed air temperature control mode, the variable frequency compressor 9 continues to run and undertakes temperature and humidity control. The fresh air ratio is continuously adjusted under the slope constraint. Controller 16 prohibits step switching to the free cooling mode because the free cooling mode requires the variable frequency compressor 9 to stop and the fresh air ratio to step to 1. When the carbon dioxide concentration exceeds the limit but the outdoor air enthalpy is unfavorable, the fresh air will cause the indoor temperature and humidity to exceed the limit at the same time, and the hygiene index and thermal comfort index cannot be met at the same time.

[0154] Controller 16 continuously verifies the carbon dioxide concentration pullback time during the ramp process. The full-occupancy steady-state concentration corresponding to the target fresh air valve 3 opening degree is: The carbon dioxide concentration has changed from the current value. Return to set value Required pullback time as

[0155]

[0156] Calculate the steady-state concentration when full capacity is reached. Greater than or equal to the set value The logarithmic solution does not exist. Controller 16 determines that the opening of the target fresh air valve 3 is insufficient to maintain the hygiene index in steady state. After increasing the opening of the target fresh air valve 3 by one level, it recalculates the pull-back time. When the opening of the target fresh air valve 3 is increased to level 1, the pull-back time is still greater than the allowable pull-back time. and Take 10 to 15 minutes, or the current carbon dioxide concentration. Reaching emergency limits and Take 2000ppm, controller 16 performs graded upgrade, if the enthalpy condition of the free cooling mode is... If the conditions are met, the controller 16 is allowed to upgrade to the free cooling mode as the fresh air valve 3 continues to ramp up to full opening. If the enthalpy conditions of the free cooling mode are not met, the controller 16 will upgrade to the full fresh air operation mode of the total heat recovery fresh air mode and issue a capacity shortage warning. The upgrade process is also completed along the ramp and is not allowed to jump.

[0157] When the actual fresh air volume If the fresh air volume is still lower than the required fresh air volume and the deviation exceeds 10% after the fresh air valve 3 reaches the commanded opening, the controller 16 determines that the resistance of the fresh air flow channel has increased. It first increases the speed of the fresh air fan 5 to compensate. If the speed is increased to the upper limit and still does not meet the requirements, it issues a prompt to clean or replace the filter.

[0158] The exit hysteresis of the hard constraint response is set when the carbon dioxide concentration is at its current value. Falling back to the lifting limit and Take below 1100 ppm and continue to remove for a period of time. and From 120s to 300s, controller 16 controls the fresh air valve 3 to limit the slope to fall back to the opening required for economic operation at the same rate. The return air valve 4 opens in conjunction with this, and then the dwell time gating is re-enabled. The operation mode selection returns to the normal judgment process. The difference between the limit value and the hard limit value of carbon dioxide concentration constitutes the exit hysteresis band, which prevents the hard constraint response from repeatedly entering and exiting when the carbon dioxide concentration fluctuates near the hard limit value.

[0159] During normal operation without triggering hard constraint responses, the minimum fresh air volume serves as the execution lower limit for any operating mode. When the economical operating fresh air volume given by the dwell time gating is lower than the minimum fresh air volume, the controller 16 executes according to the minimum fresh air volume. When the carbon dioxide sensor 14 malfunctions or its data fails, the controller 16 operates at a minimum opening degree of the fresh air valve 3 corresponding to the minimum fresh air volume and issues a sensor fault warning. This ensures that hygiene indicators maintain an execution bottom line that cannot be suppressed by gating under any meteorological trend and any economic judgment. The required fresh air volume is calculated by quality balance to ensure that the opening range of the fresh air valve 3 corresponds to the actual personnel load, thus avoiding energy waste caused by opening it all at once. The ramp rate limit and the linkage of the return air valve 4, as well as the compressor power feedforward, ensure that the total supply air volume and supply air temperature remain continuous during the increase of fresh air volume. The priority of the mixed air temperature control mode and the prohibition of step switching in the free cooling mode ensure that the indoor air quality recovery process does not sacrifice temperature and humidity control. The graded upgrade and exit hysteresis ensure that the controller 16 has a definite execution branch under extreme personnel density conditions and sensor abnormal conditions.

[0160] When the dwell time gating allows a switch from the current operating mode to a candidate operating mode, controller 16 enters a transition state. The transition state is an actuator-coordinated transition process between the current operating mode and the candidate operating mode. During the transition state, controller 16 freezes the dwell time determination and no longer responds to new mode switching requests. Hard constraint responses are not within the frozen range. The start time of the transition state is denoted as [time value missing]. The opening degree of the fresh air valve 3 corresponding to the current operating mode is recorded as: The opening degree of the fresh air valve 3 corresponding to the candidate operating mode is recorded as the target opening degree. The sum of the opening degrees of the fresh air valve 3 and the return air valve 4 is always equal to 1, and the controller 16 controls the valve position change rate. Generate the opening trajectory of the fresh air valve 3 for rate limiting.

[0161]

[0162] In the formula The transition period is the time when the opening trajectory of fresh air valve 3 reaches the target opening. After holding, press return air valve 4. Linkage, transition state duration satisfies .

[0163] After the opening trajectory of the fresh air valve 3 is generated, the controller 16 performs speed feedforward compensation on the fresh air fan 5, exhaust fan 6 and circulating fan 7 to keep the total supply air volume constant. The fresh air volumetric airflow remains constant throughout the transition state, and at any given time is: Exhaust volume air volume ,in The differential air volume required to maintain a slightly positive pressure in the room is: The controller 16 provides the feedforward speed of the three fans based on the factory-calibrated correspondence between fan speed, air volume, and static pressure. The speed of the fresh air fan 5 is calculated according to... Calculations show that the exhaust fan operates at speed 6. Calculations are made based on the 7-speed rotation of the circulating fan. Calculate, where , and These are the speed and air volume mapping relationships for the three fans. The resistance state of the total heat recovery core 1 is determined by the position of the core bypass ventilation valve 2. When the total heat recovery core 1 is in operation, the speed of the fresh air fan 5 is mapped to the high-resistance branch, and when the core is bypassed, the low-resistance branch is mapped. The controller 16 simultaneously uses the measured value of the total supply air volume airflow. Feedback correction is performed on the speed of circulating fan 7, and the correction amount is as follows: calculate, The air volume feedback coefficient ensures that the total air volume at the air outlet does not change with the fresh air ratio during the opening of the fresh air valve 3.

[0164] While the fan speed is fed forward, the controller 16 adjusts the variable frequency compressor 9 and electronic expansion valve 11 according to the fresh air load change rate. When the total heat recovery core 1 is put into operation, the fresh air is induced by the enthalpy of the fresh air outlet air. When entering the mixing section, the fresh air bypasses the core and uses the enthalpy of the fresh air inlet. Entering the mixing section, the enthalpy of the exhaust inlet air is recorded as follows: Mixed wind enthalpy

[0165]

[0166] Calculate the moisture content of the mixed air according to Calculate, where and The moisture content of the air at the fresh air outlet and exhaust air inlet are respectively, and the handling load that the coil needs to bear is calculated according to...

[0167]

[0168] Calculate, where For air supply quality flow rate, To set the supply air enthalpy, the rate of change of the coil handling load with the opening degree of fresh air valve 3 is as follows:

[0169]

[0170] The controller 16 calculates the capacity curve of the variable frequency compressor 9. Map the coil handling load to the compressor frequency feedforward. ,in The operating frequency and capacity curve of the variable frequency compressor 9. The compressor frequency command is obtained by superimposing the supply air temperature feedback on the frequency feedforward, using the coil handling load and condensing temperature as inputs.

[0171]

[0172] In the formula For supply air temperature, The supply air temperature setpoint. , and As the feedback coefficient, the opening command of the electronic expansion valve 11 is based on... Calculate, where The expansion valve feedforward opening is given by the compressor frequency. This is the measured value of the intake superheat. Set the intake superheat value. As the superheat feedback coefficient, the compressor frequency feedforward and the opening trajectory of the fresh air valve 3 are aligned on the same time axis. As the fresh air load increases, the compressor capacity increases synchronously, ensuring that the supply air temperature deviation meets the requirements.

[0173]

[0174] In the formula For the comfort zone half-width and 1.5℃, controller 16 performs condensation safety constraint verification throughout the transition state, based on the moisture content of the mixed air. and mixed wind enthalpy Determine the mixed air state point and obtain the mixed air dew point temperature by referring to the saturated air relationship. The required supply air temperature is to meet the following requirements. ,in To ensure a safety margin for condensation, a range of 1°C to 2°C is taken. When the calibration is not met, the controller 16 locks the opening trajectory of the fresh air valve 3, and the fresh air valve 3 remains at the current opening. The circulating fan 7 and the variable frequency compressor 9 continue to adjust the coil processing capacity according to the supply air temperature feedback. Once the supply air temperature is higher than the sum of the mixed air dew point temperature and the condensation safety margin, the lock is released and the fresh air valve 3 continues to open. Thus, the fresh air valve 3 reaches the target opening in a step-by-step manner under the temperature and humidity safety constraints.

[0175] When the candidate operating mode is the total heat recovery fresh air mode, the controller 16 executes the core preset timing sequence. After the switch starts, the fresh air valve 3 remains closed. The controller 16 first starts the exhaust fan 6 to establish airflow on the exhaust side of the total heat recovery core 1. The exhaust air flows through the core, causing the temperature and humidity fields of the core material to shift from a static state to an exhaust state. The preset completion criterion is the temperature at the fourth measuring point. Temperature at the third measuring point The absolute value of the difference is less than the preset temperature difference. and Set the temperature to 1℃, or set the preset duration to the preset time. and The preset time is set to 90 seconds. If either of the two conditions is met, the preset is considered complete. During the preset period, the indoor air supply is maintained by the recirculating fan 7 drawing in return air, and the total air supply volume is equal to the air volume. Without interruption, after the preset is completed, the controller 16 will start the fresh air fan 5 and open it to the target opening degree according to the opening trajectory of the fresh air valve 3. The core is pre-set so that when fresh air enters the core, both airflows and the core temperature and humidity field are established, avoiding sudden jumps in supply air temperature and humidity caused by fresh air directly penetrating without being recovered. When switching from the total heat recovery fresh air mode to the core bypass operation mode, the controller 16 first opens the core bypass ventilation valve 2 and then adjusts the opening of the fresh air valve 3. The exit sequence is the opposite of the entry sequence.

[0176] The controller 16 ends the transition state when all three conditions for exiting the transition state are met simultaneously. The first condition is that the opening degree of the fresh air valve 3 reaches the target opening degree. The second requirement is that the air supply temperature deviation should not exceed half the width of the comfort zone. Furthermore, the condensation safety constraint is satisfied and the steady-state confirmation time is maintained. and Take 60 seconds. The third item is the compressor frequency and the opening degree of electronic expansion valve 11. After the transition state ends, the residence time determines whether to re-enable. If the duration of the transition state exceeds the transition state timeout, the system will be activated. and If the exit condition is not met after 300 seconds, the controller 16 returns to the internal circulation temperature control mode and maintains the minimum fresh air volume while issuing a fault prompt. When the hard constraint is triggered during the transition state, the controller 16 releases the dwell time judgment freeze and enters the hard constraint response process. The core preset and the opening of the fresh air valve 3 are changed to be executed in parallel to shorten the time for fresh air to reach the room. Through the above steps, the mode switching is changed from the actuator step action to a coordinated process of valve position trajectory, fan speed trajectory and compressor capacity trajectory on the same time axis. The constant total air volume eliminates the change in the airflow sensation caused by the air volume step. The feedforward of the fresh air load change rate makes the compressor capacity adjustment occur before the supply air temperature deviation. The condensation margin lockout and the core temperature field preset judgment incorporate humidity safety and heat exchange establishment state into the switching sequence. The transition state freeze avoids the actuator back and forth action caused by continuous switching. The hard constraint priority branch ensures that the hygiene indicators can still respond in time during the transition state.

[0177] In winter heating mode, controller 16 incorporates the frosting risk of the total heat recovery core 1 as a boundary condition of the mode feasible region into the residence time calculation. During winter operation, the indoor exhaust air is based on the exhaust air inlet temperature. Moisture content of exhaust air inlet The outdoor fresh air enters the total heat recovery core 1 in a state where the outdoor fresh air is at the fresh air inlet temperature. The air enters the total heat recovery core 1 and is heated by the exhaust air. The exhaust air is cooled within the core. When the exhaust air outlet temperature drops to the exhaust air inlet dew point temperature... At this point, condensation begins on the exhaust side. When the exhaust outlet temperature continues to drop below 0°C, the condensation freezes into frost. The frost layer increases the flow resistance of the core and reduces the reliable total heat transfer efficiency. decline.

[0178] The controller 16 uses a four-point steady-state identification process to identify the reliable temperature heat transfer efficiency online, replacing enthalpy with temperature. Temperature heat exchange efficiency under winter operating conditions is calculated according to

[0179]

[0180] Definition, in the formula For fresh air outlet temperature, reliable temperature heat exchange efficiency The recursive identification follows the steady-state identification window and the recursive least squares with forgetting factor and confidence determination process. The controller 16 calculates the exhaust outlet temperature from the reliable temperature heat transfer efficiency.

[0181]

[0182] In the formula The fourth measuring point is the exhaust outlet temperature. Controller 16 is constrained by the exhaust outlet temperature not being lower than the sum of the exhaust inlet air dew point temperature and the frosting safety margin. The frosting safety margin is denoted as... And take 1℃ to 2℃, let The inverse solution yields the critical fresh air temperature for condensation.

[0183]

[0184] Critical fresh air temperature for condensation This means that when the fresh air inlet temperature drops to the critical fresh air temperature for condensation, the exhaust outlet temperature reaches the condensation warning line. Simultaneously, controller 16 uses the constraint that the exhaust outlet temperature equals 0℃ to inversely solve for the critical fresh air temperature for frosting. When the heat transfer efficiency at the reliable temperature When the condensation critical fresh air temperature decreases due to dust accumulation or initial frost on the filter element, Critical fresh air temperature for frosting All values ​​shift towards higher values, meaning that the worse the core performance, the higher the outdoor temperature required to trigger defrost. The frosting boundary is corrected moment by moment according to the measured state of the core. Controller 16 estimates the first-order rate of change of the fresh air inlet temperature using a weighted recursive least squares process. and second-order acceleration , and according to

[0185]

[0186] Predict the trajectory of the fresh air inlet temperature, where This is the current value of the fresh air inlet temperature. For the prediction time preceding the current moment, controller 16 sets the predicted fresh air inlet temperature to equal the critical fresh air temperature for condensation, i.e., solving the equation. ,when First violation of the time limit for frosting margin

[0187]

[0188] Take the smallest non-negative real root, when Press at time The calculation indicates that if the square root is negative or the resulting root is negative, it means that the exhaust outlet temperature in the prediction time domain does not reach the condensate warning line, and the first violation of the frost margin is taken from the prediction time domain. Controller 16 will trigger the first violation of the frosting margin. The predicted residence time of the total heat recovery fresh air mode is updated by taking the minimum value of the first violation time of enthalpy and carbon dioxide conditions.

[0189]

[0190] After obtaining the updated predicted residence time, controller 16 will compare the predicted residence time with the shortest effective residence time of the total heat recovery fresh air mode. Comparison, when the frosting margin first violates the time. Less than the shortest effective residence time of the total heat recovery fresh air mode When the system has not yet switched to the total heat recovery fresh air mode, controller 16 prohibits switching to the total heat recovery fresh air mode. The candidate operating mode is changed to mixed air temperature control mode, and the fresh air enters the coil through the core bypass ventilation path, where the variable frequency compressor 9 handles the temperature control. When the system is already in the total heat recovery fresh air mode and the first violation time of the frost margin is less than the remaining residence requirement, controller 16 exits the total heat recovery fresh air mode in advance and activates the core bypass ventilation valve 2 to perform anti-frost operation. The anti-frost operation adopts bypass ratio graded control, and the bypass ratio is denoted as... And it is defined as the proportion of fresh air that bypasses the total heat recovery core 1, and the fresh air volume flowing through the core during partial bypass is: In the formula For fresh air volume, the exhaust air volume remains constant, and controller 16 uses the exhaust outlet temperature to meet the requirements. To constrain the reverse frost bypass ratio, the temperature heat transfer efficiency under partial bypass conditions is determined by the bench calibration relationship between the core airflow ratio and the temperature heat transfer efficiency. The constraints are obtained from the table and written as follows:

[0191]

[0192] Controller 16 bypass ratio The bypass ratio is increased in increments of 0.05, and the calibration relationship is checked sequentially. Until the temperature heat transfer efficiency in partial bypass mode does not exceed the upper limit of allowable efficiency. Thus, the frost bypass ratio is obtained. When the anti-frost bypass ratio is not greater than the maximum allowable bypass ratio and When the value is 0.5, the controller 16 opens the core bypass ventilation valve 2 to the anti-frost bypass ratio and maintains the operation in the total heat recovery fresh air mode. The temperature of the fresh air after the bypass fresh air and the core fresh air are mixed is as follows: The calculations are as follows: the subsequent coil load and frequency feedforward of the variable frequency compressor 9 are recalculated based on the mixed fresh air state. When the anti-frost bypass ratio is greater than the maximum allowable bypass ratio, or when the exhaust outlet temperature is still lower than the sum of the exhaust inlet air dew point temperature and the frost safety margin after operating at the anti-frost bypass ratio, the controller 16 will fully open the core bypass ventilation valve 2 and exit the total heat recovery fresh air mode to switch to the mixed air temperature control mode. When the exhaust outlet temperature drops below 0℃ and frost continues for a certain period of time, the controller will confirm the operation. and After 60 seconds, controller 16 determines that the core has been frosted and executes the defrosting procedure. During the defrosting procedure, all ventilation valves 2 around the core are opened, the fresh air fan 5 is turned off or reduced to its lowest speed, and the exhaust fan 6 continues to run so that the indoor exhaust air carries residual heat and flows through the core to melt the frost layer. When the temperature at the exhaust outlet rises to less than 2°C compared with the temperature at the exhaust inlet, the defrosting confirmation time continues. and After 300 seconds, the defrosting process ends. The re-entry setting for the total heat recovery fresh air mode is a re-entry hysteresis. This hysteresis occurs when the fresh air inlet temperature rises above the sum of the fresh air temperature and the re-entry temperature margin, which is higher than the condensation critical fresh air temperature margin. Set the temperature to 2℃ and continuously re-enter to confirm the time. and After 600 seconds, controller 16 allows the total heat recovery fresh air mode to re-enter the residence time gate. When the reliable temperature heat exchange efficiency cannot recover to 0.8 times the rated value after the defrosting program ends, controller 16 issues a filter check prompt. When the carbon dioxide hard constraint is triggered during the anti-frost operation, the hygiene indicators are executed first. In the hard constraint response, controller 16 adopts the maximum allowable fresh air volume at that time and applies the anti-frost bypass ratio at the same time. This ensures that the decision to switch to the total heat recovery fresh air mode in winter excludes the operating range that will be temporarily withdrawn due to frost before execution. The critical fresh air temperature for condensation and the critical fresh air temperature for frost move with the online identified temperature heat exchange efficiency and the measured exhaust dew point every moment. The bypass ratio is quantitatively decomposed by the condensate constraint and responds in three levels: partial bypass, full bypass, and defrosting. The re-entry hysteresis avoids the mode from being switched on and off repeatedly near the frost boundary. This ensures that the total heat recovery core 1 retains the exhaust heat during the recoverable period in winter and avoids air volume loss and defrosting energy consumption after frost formation.

[0193] To verify the actual effect of the above control method, a simulation model of the air conditioning and fresh air combined control system was established in the Matlab / Simulink environment. The simulation object is an office room in a certain region with a net volume of 180m³, a rated capacity of 12 people, a total supply air volume of 2000m³ / h, a designed fresh air volume of 360m³ / h, a fresh air mass flow rate of approximately 0.1kg / s, a variable frequency compressor 9 with a cooling capacity of 3.5kW, a cooling performance coefficient of 3.2, a total heat recovery core 1 with a rated total heat exchange efficiency of 0.72, meteorological parameters using typical meteorological year data of a certain region, an indoor carbon dioxide concentration setpoint of 1000ppm, a return air state set at a temperature of 26℃ and a relative humidity of 50%, a controller 16 sampling period of 20s, a sliding time window of 30min, and a prediction time domain of 90min. The data in the following examples were all obtained by running the simulation model under the same meteorological boundary and the same personnel working and rest conditions.

[0194] Example 1: Online identification of total heat transfer efficiency and correction of enthalpy difference boundary.

[0195] In the simulation model, the total heat transfer efficiency of the total heat recovery core 1 is set to decrease from 0.72 to 0.61 with the dust accumulation time of the filter element, simulating the decay process over 150 days of continuous operation. The controller 16 updates the reliable total heat transfer efficiency time-by-time using a recursive least squares method with a forgetting factor within the steady-state identification window. The forgetting factor is set to 0.98. The identification results are as follows: Figure 2 As shown, the maximum deviation between the identified value and the true value does not exceed 0.01, and the identification result can track the slow decay of the total heat exchange efficiency without being affected by the meteorological fluctuations at a single moment. The controller 16 corrects the enthalpy difference boundary time by time with the reliable total heat exchange efficiency and the measured additional fan power. The correction results are shown in Table 1. As the reliable total heat exchange efficiency decays from 0.72 to 0.61, the enthalpy difference boundary increases from 1.33 kJ / kg to 2.26 kJ / kg, and the feasible enthalpy range of the total heat recovery fresh air mode shrinks accordingly. When the enthalpy difference between the outdoor air and the return air is less than the enthalpy difference boundary, the controller 16 prohibits switching to the total heat recovery fresh air mode, thus avoiding the problem of negative benefits caused by still engaging total heat recovery after dust accumulation on the filter element when the rated efficiency is controlled according to the nameplate.

[0196] Table 1: Identification values ​​of total heat transfer efficiency and correction results for the enthalpy difference boundary.

[0197]

[0198] Example 2: Comparative experiment of two control strategies on a typical day during the transition season.

[0199] On a typical meteorological day in September in a certain region, the outdoor air enthalpy was consistently below the enthalpy cutoff line of 51.5 kJ / kg for free cooling from 0:00 to 6:00 and after 21:00. From 16:00 to 20:00, the air repeatedly crossed the enthalpy cutoff line due to gusts of wind. Figure 3 As shown in the figure above, under the same meteorological boundaries and the same personnel work and rest conditions, a fixed threshold strategy was used as a comparative example, and the dwell time gating strategy of this invention was used as an example. The comparative example switched the operating mode each time the outdoor air enthalpy crossed the enthalpy cut-in line and was only protected for a fixed time of 3 minutes. The strategy of this invention performed a second extrapolation on the enthalpy difference boundary variable to obtain the predicted dwell time and compared it with the shortest effective dwell time. The predicted dwell times for each crossing from 16:00 to 20:00 were 24 minutes, 40 minutes, 33 minutes and 47 minutes, respectively, all of which were less than the shortest effective dwell time of 69 minutes in the free cooling mode. All four switching requests were rejected. Figure 4 As indicated by the cross mark, the predicted dwell time increases to over 180 minutes after 21:00, and controller 16... Figure 4 The time marked by the middle circle allows switching to the free cooling mode and continuous operation until the early morning of the next day. The results of the two strategies throughout the day are shown in Table 2. The total number of mode switching times of the strategy of this invention was reduced from 18 times to 6 times, the number of start-stop times of the inverter compressor 9 was reduced from 9 times to 2 times, and the total power consumption of the system throughout the day was reduced from 12.84 kWh to 11.21 kWh, a reduction of 12.7%. The time of carbon dioxide concentration exceeding the standard and the time of supply air temperature exceeding the limit were shortened at the same time, indicating that the residence time gating suppressed the ineffective switching near the boundary without sacrificing indoor air quality and thermal comfort.

[0200] Table 2: Comparison of the operational results of the two control strategies on typical days during the transition season

[0201]

[0202] Example 3: Switching cost calibration and energy recovery experiment.

[0203] In the simulation model, the power of the variable frequency compressor 9 and the power of each fan were recorded during a complete switching process to the free cooling mode. The current surge lasted for 3 seconds, and the power consumption during the current surge was 12 kJ based on the excess power integration. The average excess power during the pressure reconstruction period was 0.4 kW and lasted for 240 seconds, with a power consumption of 96 kJ. The total additional power consumption during startup was 108 kJ. Based on the purchase and replacement cost of 1500 yuan for the variable frequency compressor 9, the allowable total number of start-stop cycles of 100,000, and the basic life loss equivalent amortized at an electricity price of 0.6 yuan / (kW·h), the additional power consumption during the transition of the air valve and fan was 3 kJ. Under the free cooling mode, the additional coil load for the core temperature and humidity field reconstruction due to the bypass of the total heat recovery core 1 was 0, and the recovery energy consumption was 5 kJ. The breakdown of the switching costs is shown in Table 3, with a total switching cost of 206 kJ. Controller 16 obtains the energy payback time by dividing the switching cost by the steady-state net benefit. The relationship between the energy payback time and the steady-state net benefit is as follows: Figure 5 As shown, the energy payback time is 69 minutes when the steady-state net benefit is 0.05 kW, and shortens to 34 minutes when the steady-state net benefit is 0.10 kW. When the cumulative start-stop count of the variable frequency compressor 9 reaches 0.8 times the total allowable start-stop count, the weighting factor increases to 1.85, the switching cost increases to 283 kJ, and the energy payback time is extended by approximately 37% under the same steady-state net benefit. Figure 5 The difference between the two curves is the quantitative result of the tightening of gating at the end of the lifespan. Based on this, the controller 16 abandons the switching request that the steady-state net benefit is insufficient to complete the energy payback within the predicted residence time.

[0204] Table 3: Scoring Results of Switching Costs to Free Cooling Mode

[0205]

[0206] Example 4: Frost prediction and anti-frost experiment under winter heating conditions.

[0207] The return air temperature is set to 20℃, the dew point temperature of the exhaust air at the return air moisture content is 8℃, the reliable temperature heat transfer efficiency identification value is 0.70, and the frosting safety margin is taken as 1.5℃. Controller 16 calculates the critical fresh air temperature for condensation to be 5℃ and the critical fresh air temperature for frosting to be −8.6℃. A simulated cold wave process causes the fresh air inlet temperature to decrease from 8℃ to −9℃ within 6 hours. Controller 16 extrapolates the fresh air inlet temperature using a first-order rate of change of −2.5℃ / h and a second-order acceleration. When the fresh air inlet temperature is 6℃, the predicted first violation time of the frosting margin is 30 minutes, which is less than the minimum effective residence time of 45 minutes for the total heat recovery fresh air mode. Therefore, controller 16 prohibits switching to the total heat recovery fresh air mode. During the fresh air recovery mode, controller 16 uses the exhaust outlet temperature to satisfy the condensation warning constraint and inversely solves the frost bypass ratio. The calculation results and controller 16 actions at different fresh air inlet temperatures are shown in Table 4. When the fresh air inlet temperature drops to 2℃, the frost bypass ratio is 0.20; when the fresh air inlet temperature drops to −3℃, the frost bypass ratio increases to 0.42; when the fresh air inlet temperature drops to −6℃, the required frost bypass ratio exceeds the maximum allowable bypass ratio of 0.5. Controller 16 then fully opens the core bypass ventilation valve 2 and exits the total heat recovery fresh air mode. When the fresh air inlet temperature drops to around −8.5℃ and the exhaust outlet temperature is close to 0℃, controller 16 executes the waste heat defrosting procedure. The frost margin prediction trajectory, threshold line, and frost bypass ratio action sequence are as follows: Figure 6 As shown, the total heat recovery core 1 did not experience frost blockage during the entire cold wave. After the fresh air inlet temperature rose and met the re-entry hysteresis condition, the controller 16 automatically resumed the total heat recovery fresh air mode.

[0208] Table 4: Frosting Allowance and Anti-frost Action at Different Fresh Air Inlet Temperatures in Winter

[0209]

[0210] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multi-mode adaptive fresh air composite regulation system for air conditioning, characterized in that, It includes a fresh air duct, a return air duct, an exhaust air duct and a supply air duct. The fresh air duct is equipped with a fresh air valve (3) and the return air duct is equipped with a return air valve (4). The fresh air valve (3) and the return air valve (4) are linked together. The total heat recovery core (1) and the core bypass ventilation valve (2) are arranged at the intersection of the fresh air duct and the exhaust air duct. The core bypass ventilation valve (2) is used to allow the outdoor fresh air to bypass the total heat recovery core (1). The system includes a fresh air fan (5), an exhaust fan (6) and a circulating fan (7), a refrigeration circuit including a variable frequency compressor (9), a condenser (10), an electronic expansion valve (11) and an evaporator (8) connected in sequence, the evaporator (8) being arranged in the air supply duct, and a sensor group including an outdoor temperature and humidity sensor (12), a return air temperature and humidity sensor (13), a carbon dioxide sensor (14) and an air supply temperature and humidity sensor (15). The controller (16) is electrically connected to the fresh air valve (3), return air valve (4), core bypass ventilation valve (2), fresh air fan (5), exhaust fan (6), circulating fan (7), variable frequency compressor (9), and sensor group, respectively. The controller (16) is configured with internal circulation temperature control mode, total heat recovery fresh air mode, free cooling mode, and mixed air temperature control mode, and is configured as follows: The enthalpy difference between outdoor air and return air, the carbon dioxide concentration margin and its rate of change are calculated in real time based on the detection values ​​of the sensor group. The total heat exchange efficiency is identified online based on the temperature and humidity of the four measuring points of the fresh air inlet, fresh air outlet, exhaust air inlet and exhaust air outlet of the total heat recovery core (1). The predicted dwell time is obtained by extrapolating the current values ​​and rate of change of enthalpy difference and carbon dioxide concentration margin to predict the moment when the feasible region of the candidate operating mode is first violated. The shortest effective residence time is calculated online based on the ratio of the switching cost of a single mode switch to the steady-state net benefit of the candidate mode. The steady-state net benefit is updated with the identification value of the total heat exchange efficiency. The switching cost includes the energy consumption of a single start-up and shutdown of the variable frequency compressor (9) and the life loss amortized according to the number of allowed start-ups and shutdowns. Only when the boundary conditions of the candidate mode are met and the predicted dwell time is not less than the shortest effective dwell time, the linkage fresh air valve (3), core side ventilation valve (2), each fan and variable frequency compressor (9) are switched to the candidate mode; otherwise, the current mode is maintained and the hysteresis bandwidth of the mode switching is determined online by superimposing the product of the rate of change of the boundary variable and the shortest effective dwell time. When the detection value of the carbon dioxide sensor (14) reaches the hard constraint limit, the controller (16) exempts the dwell time determination, controls the fresh air valve (3) to open with a limited opening ramp and switch to the mixed air temperature control mode.

2. The multi-mode adaptive fresh air composite regulation system of claim 1, wherein: Within a time window during which both the fresh air fan (5) and the exhaust fan (6) are running stably and the rate of change of the enthalpy difference is less than a preset steady-state threshold, the controller (16) identifies the total heat exchange efficiency of the total heat recovery core (1) online based on the temperature and humidity of the four measuring points and using a recursive least squares method with a forgetting factor. The controller (16) then uses the identified total heat exchange efficiency to correct the enthalpy difference boundary between the total heat recovery fresh air mode and the mixed air temperature control mode. When the steady-state net benefit of the total heat recovery fresh air mode is less than or equal to zero, the controller (16) prohibits switching to the total heat recovery fresh air mode.

3. The multi-mode adaptive fresh air composite regulation system of claim 2, wherein: The steady-state net benefit of the total heat recovery fresh air mode is determined based on the fresh air mass flow rate, the identified total heat exchange efficiency, the enthalpy difference between outdoor air and return air, the performance coefficient of the cooling circuit, and the additional power consumption of the exhaust fan (6), and decreases as the total heat exchange efficiency decreases.

4. The multi-mode adaptive fresh air composite regulation system of claim 1, wherein: The controller (16) estimates the first-order rate of change and second-order acceleration of each boundary variable using the weighted recursive least squares method within the sliding time window. Based on the current value, the first-order rate of change and the second-order acceleration, the boundary variables are extrapolated twice to find the moment when each boundary condition of the candidate operating mode is first violated, and the minimum value among them is taken as the predicted dwell time. The carbon dioxide concentration margin is extrapolated by replacing the fitted rate of change with the conservative step increase rate of personnel determined according to the full number of rated personnel or the quantile value of the concentration change rate of the same period in history.

5. The multi-mode adaptive fresh air composite conditioning system of claim 1, wherein: The switching cost includes the additional power consumption and life loss equivalent of a single start-up and shutdown of the variable frequency compressor (9), the additional power consumption during the operation of the fresh air valve (3) and return air valve (4) and the transition of the speed of each fan, the additional coil load during the reconstruction of the temperature and humidity field of the total heat recovery core (1), and the recovery energy consumption for the supply air temperature and humidity to return to the comfort zone. The life loss equivalent is calculated by amortizing the total number of allowable start-ups and shutdowns of the variable frequency compressor (9) per cycle, and increases with the increase of the cumulative number of start-ups and shutdowns or the start-up and shutdown frequency per unit time.

6. The multi-mode adaptive fresh air composite conditioning system of claim 1, wherein: The controller (16) determines the hysteresis bandwidth by multiplying the absolute value of the rate of change of the boundary variable with the shortest effective residence time and then adding a noise margin proportional to the recent standard deviation of the boundary variable. The controller (16) also limits the output between the preset lower and upper limits of the bandwidth. The controller (16) also accumulates the carbon dioxide concentration over-limit integral and the temperature and humidity over-limit integral during the period when the residence time determination is not met. When the over-limit integral exceeds the preset threshold, the hysteresis bandwidth is narrowed in reverse.

7. The multi-mode adaptive fresh air composite conditioning system of claim 1, wherein: The hard constraint limits include the hard limit of carbon dioxide concentration and the minimum fresh air volume to meet the room hygiene requirements. When the hard constraint limits are reached, the controller (16) controls the fresh air valve (3) to open at a preset rate and the return air valve (4) to close in conjunction with it. It also prioritizes switching to the mixed air temperature regulation mode to continuously adjust the fresh air ratio, while prohibiting step switching to the free cooling mode.

8. The multi-mode adaptive fresh air composite conditioning system of claim 1, wherein: After being granted permission to switch to the candidate operating mode, the controller (16) enters a transition state and freezes the dwell time determination during the transition state: The fresh air valve (3) restricts the ramp action according to the rate determined by its full stroke time. The return air valve (4) is linked. The fresh air fan (5), exhaust fan (6) and circulating fan (7) perform speed feedforward compensation according to the constant total air volume. The frequency of the variable frequency compressor (9) and the opening of the electronic expansion valve (11) are adjusted according to the fresh air load change rate and the air supply temperature feedback is superimposed to ensure that the air supply temperature deviation does not exceed the preset temperature difference and the air supply relative humidity is kept outside the safe margin of the condensation line. When switching to the total heat recovery fresh air mode, the exhaust fan (6) is started first to establish the two airflows of the total heat recovery core (1) and preset the preset time. Then, the fresh air valve (3) is controlled to open to the target opening.

9. The multi-mode adaptive air conditioning and fresh air composite control system according to claim 1, characterized in that: In winter heating mode, the controller (16) will also include the difference between the predicted temperature of the exhaust outlet and the exhaust dew point temperature as the frost margin boundary variable in the calculation of the predicted residence time. When the predicted frost margin boundary variable is violated within the shortest effective residence time, the controller will prohibit switching into or exiting the total heat recovery fresh air mode in advance, and will link the core side ventilation valve (2) to perform anti-frost operation.

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