A time-sharing variable frequency refrigeration equipment defrosting energy-saving control method and system

Abstract

The application relates to the technical field of energy-saving control, and discloses a refrigeration equipment time-sharing variable-frequency cooperative defrosting energy-saving control method and system, wherein the refrigeration equipment time-sharing variable-frequency cooperative defrosting energy-saving control method comprises the following steps: collecting operation parameters, activating a cooperative defrosting process, estimating the object temperature estimation value of a first temperature zone and a second temperature zone based on an object temperature estimation model and constructing a steady state quantity; calculating a defrosting index, setting an upper limit of a dynamic time length based on the operation parameters and the steady state quantity, determining immediate defrosting or delayed defrosting; starting defrosting, ending defrosting when a defrosting interruption condition is triggered; adjusting a cold quantity distribution ratio and a circulating fan rotating speed; judging whether to exit the cooperative defrosting process based on the current frost risk index and the steady state quantity; the application matches the defrosting time and the defrosting time length with the actual state of the double-temperature zone, thereby avoiding early, late, excessive or insufficient defrosting, reducing the object temperature fluctuation during defrosting, and improving the object temperature stability of the double-temperature zone.

Description

Technical Field

[0001] This application relates to the field of energy-saving control technology, and more specifically, it relates to a time-sharing frequency conversion coordinated defrosting energy-saving control method and system for refrigeration equipment. Background Technology

[0002] Refrigeration equipment requires high temperature stability for stored items. To meet the diverse needs of different stored items in terms of short-term access, pre-cooling, and tiered storage, existing refrigeration equipment typically features a first and second temperature zone, with corresponding temperature control achieved through components such as compressors, evaporators, fans, and temperature sensors. For single refrigeration systems or products with strong coupling between the two temperature zones, the set temperatures of the two zones are usually not completely independent due to the correlation in cold energy supply, airflow distribution, and temperature difference formation mechanisms. Therefore, basic temperature control attainability and operational stability are often ensured through temperature linkage, setpoint correction, or temperature difference constraints.

[0003] The existing patent announcement number CN107131715B discloses a temperature control method, control system, and computer device for a dual-temperature wine cabinet. The method involves setting the operating temperature of a first temperature chamber, obtaining the temperature range of a second temperature chamber corresponding to the operating temperature of the first temperature chamber, setting the operating temperature of the second temperature chamber, determining whether the operating temperature of the second temperature chamber is within the temperature range corresponding to the operating temperature of the first temperature chamber, and correcting the operating temperature of the first temperature chamber when the operating temperature of the second temperature chamber is not within the temperature range corresponding to the operating temperature of the first temperature chamber.

[0004] However, existing technologies primarily focus on the static matching and setpoint correction of target temperatures in both temperature zones, neglecting the dynamic frosting conditions of refrigeration equipment under high humidity. Especially when the humidity inside the unit is high, the door is frequently opened, and there is significant air exchange between the inside and outside, frost easily forms on the evaporator surface. Accumulated frost leads to decreased heat exchange efficiency, increased air resistance, imbalanced cooling capacity distribution, and a slower temperature recovery rate. In such cases, if a control method primarily based on setpoint temperature correction is still used, while it can maintain the setpoint relationship between the two temperature zones to some extent, it is difficult to simultaneously address the appropriate selection of defrosting timing, the stability of the temperature in both zones during defrosting, and the recovery control after defrosting. Furthermore, existing defrosting control in refrigeration equipment often employs fixed strategies such as timed defrosting, defrosting based on cumulative running time, or defrosting based on evaporator temperature thresholds. These strategies typically do not adequately consider factors such as ambient temperature and humidity, door opening frequency, actual heat load differences between the two temperature zones, storage loading rate, storage thermal inertia, and time-of-use electricity pricing for comprehensive adjustment. Consequently, issues such as mismatch between defrosting trigger timing and actual operating requirements, large temperature fluctuations during defrosting, asynchronous recovery after defrosting, and high overall energy consumption may arise. Summary of the Invention

[0005] The purpose of this application is to overcome the shortcomings of the existing technology and provide a time-sharing variable frequency collaborative defrosting energy-saving control method and system for refrigeration equipment, so as to solve the problems of unreasonable defrosting triggering time, large temperature fluctuation during defrosting, asynchronous recovery after defrosting, and difficulty in achieving energy-saving operation in existing refrigeration equipment under high humidity and easy frosting conditions.

[0006] This application provides a time-sharing variable frequency coordinated defrosting energy-saving control method for refrigeration equipment, including the following steps:

[0007] The main controller collects operating parameters, normalizes the operating parameters, and then calculates the weighted sum to obtain the frost risk index. When the frost risk index is greater than or equal to the preset risk threshold, the collaborative defrosting process is activated. Based on the material temperature estimation model, the material temperature estimates of the first and second temperature zones are estimated and a steady state quantity is constructed.

[0008] The defrost index is calculated based on the steady state quantity. The defrost index is compared with a preset window threshold to determine whether to defrost immediately or delay defrosting.

[0009] When it is determined to defrost immediately or to exit delayed defrost, the estimated temperature of each temperature zone is reduced to the pre-stabilized temperature target and then defrost is started. The upper limit of dynamic duration is set based on the operating parameters and stable state quantities. During the defrost process, the estimated temperature is continuously monitored and the defrost interruption condition is determined according to the upper limit of dynamic duration. When the defrost interruption condition is triggered, the defrost ends.

[0010] After defrosting, the recovery coefficient is calculated based on the steady-state quantities, and the cooling capacity distribution ratio and circulating fan speed are adjusted according to the recovery coefficient of each temperature zone.

[0011] The main controller recalculates the current frost risk index and steady-state quantity, and determines whether to exit the collaborative defrosting process based on the current frost risk index and steady-state quantity.

[0012] Furthermore, methods for obtaining material temperature estimates include:

[0013] Based on the current loading rate provided by the loading status detection unit, the thermal response coefficient is obtained by looking up the pre-stored table of correspondence between thermal response coefficient and loading rate.

[0014] When the current load rate is between two adjacent calibrated load rates, the corresponding thermal response coefficient is obtained by linear interpolation.

[0015] The material temperature estimation model calculates the estimated material temperature for each temperature zone based on the thermal response coefficient.

[0016] Furthermore, methods for constructing steady-state variables include:

[0017] Calculate the material temperature deviation for each temperature zone, specifically by subtracting the preset target temperature of the temperature zone from the estimated material temperature of that zone.

[0018] The main controller assigns preset temperature zone weights according to the intended use of each temperature zone;

[0019] The steady-state quantity is constructed by using the temperature deviation of each temperature zone and the preset application weight of each temperature zone as constraints.

[0020] Furthermore, methods for calculating the defrost index include:

[0021] The defrosting economic weight for the current period is determined based on the preset electricity price level corresponding to the current period.

[0022] The predicted value of user door opening activity within the future preset prediction time window is determined by the arithmetic mean of the door opening frequency data of the same historical period.

[0023] The recovery difficulty index after defrosting is determined based on the temperature deviation of each temperature zone in the steady state quantity and the ambient temperature outside the refrigeration equipment.

[0024] The defrost index is obtained by weighting and summing the defrost economic weight, the first reverse activity value, and the second reverse recovery difficulty value; where the first reverse activity value is one minus the predicted user door opening activity value, and the second reverse recovery difficulty value is one minus the recovery difficulty index after defrosting.

[0025] Furthermore, methods for performing delayed defrosting include:

[0026] When the defrosting index is less than the preset window threshold, the delayed defrosting stage is entered, limiting the operating frequency of the variable frequency compressor to a preset restricted variable frequency range;

[0027] The target cooling capacity distribution ratio for delayed defrosting is calculated based on the temperature deviation of each of the two temperature zones and the preset temperature zone usage weights. The opening of the electric proportional damper in the refrigeration equipment is then adjusted according to the target cooling capacity distribution ratio.

[0028] During the delayed defrosting phase, the main controller continuously and periodically calculates the defrosting index until the defrosting index is greater than or equal to a preset window threshold, at which point it exits the delayed defrosting phase.

[0029] Furthermore, methods for setting a dynamic duration limit include:

[0030] Divide the evaporator inlet and outlet temperature difference in the current operating parameters by the preset maximum reference value of the evaporator inlet and outlet temperature difference and perform amplitude limiting to obtain the frosting characteristic quantity.

[0031] Based on the preset baseline defrosting time, the product of the preset frost degree adjustment coefficient and the frost characteristic quantity is added, and then the product of the maximum value of the positive material temperature deviation between the two temperature zones and the preset material temperature deviation adjustment coefficient is subtracted to obtain the upper limit of the dynamic time; wherein, the positive material temperature deviation is the difference between the estimated material temperature value and the corresponding preset target temperature. When the estimated material temperature value is less than or equal to the corresponding preset target temperature, the positive material temperature deviation is zero.

[0032] Furthermore, methods for determining defrosting interruption conditions include:

[0033] The calculation of the temperature rise increment includes: the main controller records the estimated temperature of the temperature zone with a larger application weight at the time of defrosting start as the defrosting start temperature reference value; during the defrosting process, the difference between the current estimated temperature of the temperature zone and the defrosting start temperature reference value is continuously calculated to obtain the temperature rise increment.

[0034] Defrosting interruption conditions include defrosting execution time being greater than or equal to the dynamic duration limit, evaporator surface temperature being greater than or equal to the preset defrosting termination temperature, or the temperature rise increment being greater than or equal to the preset defrosting interruption temperature rise threshold.

[0035] The defrost interruption condition is triggered when any one of the defrost interruption conditions is met.

[0036] Furthermore, methods for obtaining the coefficient of restitution include:

[0037] When the temperature deviation is greater than zero, the temperature deviation of each temperature zone after defrosting is normalized and limited based on the preset maximum reference value of the temperature deviation to obtain the normalized temperature deviation characteristic quantity; when the temperature deviation is less than or equal to zero, the normalized temperature deviation characteristic quantity is zero.

[0038] The recovery slope requirement is calculated based on the temperature deviation of each temperature zone. The recovery slope requirement of each temperature zone is normalized and limited based on the preset maximum reference value of the recovery slope to obtain the normalized recovery slope characteristic quantity.

[0039] When the temperature deviation of the material in the temperature zone is greater than zero, the normalized temperature deviation characteristic, the application weight of the temperature zone, and the normalized recovery slope characteristic are weighted and summed to obtain the recovery coefficient of the temperature zone; when the temperature deviation of the material in the temperature zone is less than or equal to zero, the recovery coefficient of the temperature zone is determined to be zero.

[0040] Furthermore, methods for determining whether to exit the collaborative defrosting process include:

[0041] Set a preset recovery threshold, which is a preset risk threshold multiplied by a preset hysteresis coefficient;

[0042] When the frost risk index is less than the preset recovery threshold, and the absolute value of the temperature deviation in each temperature zone is less than or equal to the preset allowable bandwidth of the temperature deviation, the main controller exits the collaborative defrosting process and resumes the conventional time-sharing variable frequency energy-saving control mode. The conventional time-sharing variable frequency energy-saving control mode adjusts the operating frequency of the variable frequency compressor according to the preset electricity price level corresponding to the current time period.

[0043] This application provides a time-sharing variable frequency collaborative defrosting energy-saving control system for refrigeration equipment, used to execute the aforementioned time-sharing variable frequency collaborative defrosting energy-saving control method for refrigeration equipment; the system includes:

[0044] The material temperature status module is used to collect operating parameters, normalize the operating parameters and then perform a weighted summation to obtain the frost risk index. When the frost risk index is greater than or equal to the preset risk threshold, the collaborative defrosting process is activated. Based on the material temperature estimation model, the material temperature estimates of the first and second temperature zones are estimated and a steady state quantity is constructed.

[0045] The defrost determination module is used to calculate the defrost index based on the steady state quantity, compare the defrost index with the preset window threshold, and determine whether to defrost immediately or delay defrost.

[0046] The defrost start module is used to start defrost after reducing the estimated temperature of each temperature zone to the pre-stabilized temperature target when it is determined that it is to defrost immediately or to exit delayed defrost. The module sets the upper limit of dynamic duration based on the operating parameters and stable state quantities. During the defrost process, the estimated temperature of the material is continuously monitored and the defrost interruption condition is determined according to the upper limit of dynamic duration. When the defrost interruption condition is triggered, the defrost ends.

[0047] The defrost recovery module is used to calculate the recovery coefficient based on the steady state quantity after defrosting, and adjust the cooling capacity distribution ratio and the circulating fan speed according to the recovery coefficient of each temperature zone.

[0048] The defrost exit module is used by the main controller to recalculate the current frost risk index and steady-state quantity, and determine whether to exit the collaborative defrost process based on the current frost risk index and steady-state quantity.

[0049] The beneficial effects of this application are as follows: This application collects operating parameters and constructs a frosting risk index through a main controller. When the frosting risk reaches a preset risk threshold, it further obtains estimated material temperatures for two temperature zones based on a material temperature estimation model and constructs steady-state variables. This expands the control basis from a simple temperature zone setpoint to a synergistic representation of the evaporator frosting state and the actual material temperature state in both temperature zones. Therefore, it can more accurately reflect the coupling relationship between frosting risk and material temperature requirements in both temperature zones under high humidity conditions, improving the control targeting and adaptability of refrigeration equipment under complex operating conditions.

[0050] This application calculates a defrost index based on steady-state quantities and compares the defrost index with a preset window threshold to determine whether to defrost immediately or delay defrosting. When defrosting needs to be initiated, the estimated temperature values ​​of each temperature zone are first reduced to the pre-stabilized temperature target. Then, a dynamic duration upper limit is set based on operating parameters and steady-state quantities. During the defrosting process, the estimated temperature values ​​are continuously monitored to determine the defrosting interruption conditions based on the dynamic duration upper limit. Compared with the fixed control methods of timed defrosting, cumulative running time defrosting, or single threshold defrosting in the prior art, this application can match the defrosting timing and duration with the actual state of the two temperature zones, thereby helping to avoid defrosting too early, too late, excessive, or insufficient, reducing temperature fluctuations during defrosting, and improving the temperature stability of the two temperature zones.

[0051] After defrosting, this application calculates the recovery coefficient based on steady-state quantities and adjusts the cooling capacity distribution ratio and circulating fan speed according to the recovery coefficients of each temperature zone. Then, it recalculates the current frost risk index and steady-state quantities to determine whether to exit the collaborative defrosting process. This allows for differentiated recovery control based on the actual recovery needs of the two temperature zones after defrosting, and exits the collaborative defrosting process only after reaching a suitable state. This helps to improve the problems of asynchronous recovery between the two temperature zones, unbalanced cooling capacity distribution, and increased energy consumption after defrosting. While ensuring stable material temperatures in both short-term access and long-term storage zones, it achieves better energy-saving operation. Attached Figure Description

[0052] Figure 1 This is a flowchart illustrating a time-sharing frequency conversion coordinated defrosting energy-saving control method for refrigeration equipment according to this application;

[0053] Figure 2 This is an example diagram illustrating the defrosting end judgment of a time-sharing frequency conversion coordinated defrosting energy-saving control method for refrigeration equipment according to this application;

[0054] Figure 3 This is a module example diagram of a time-sharing frequency conversion collaborative defrosting energy-saving control system for refrigeration equipment according to this application. Detailed Implementation

[0055] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, features described in some examples may be combined in other examples.

[0056] A time-sharing variable frequency collaborative defrosting energy-saving control method and system for refrigeration equipment includes the following embodiments:

[0057] Example 1:

[0058] A time-sharing variable frequency collaborative defrosting energy-saving control method for refrigeration equipment, wherein the refrigeration equipment includes a first temperature zone and a second temperature zone, wherein the first temperature zone is used for short-term storage temperature control and the second temperature zone is used for long-term storage temperature control; the refrigeration equipment also includes a main controller, a variable frequency compressor, a first temperature zone circulating fan, a second temperature zone circulating fan, an evaporator, a defrosting execution unit, an air duct distribution execution unit, a temperature and humidity acquisition unit, a door opening detection unit, a loading status detection unit, and a parameter storage and calculation unit.

[0059] The main controller is communicatively connected to the variable frequency compressor, the first temperature zone circulating fan, the second temperature zone circulating fan, the defrosting execution unit, the air duct distribution execution unit, the temperature and humidity acquisition unit, the door opening detection unit, the loading status detection unit, and the parameter storage and calculation unit. The temperature and humidity acquisition unit is used to collect the air temperature of the first temperature zone, the air temperature of the second temperature zone, the evaporator surface temperature, the temperature difference between the evaporator inlet and outlet, the humidity inside the chamber, and the ambient temperature. The temperature and humidity acquisition unit includes temperature and humidity sensors respectively installed in the first and second temperature zones, a temperature sensor installed on the evaporator surface, temperature sensors installed on the air inlet and outlet sides of the evaporator, a temperature sensor installed at the return air vent, and an ambient temperature sensor installed outside the unit. The humidity inside the chamber is the maximum value of the relative humidity of the first and second temperature zones. In an optional embodiment, the humidity inside the chamber is the humidity value obtained by weighting the relative humidity of the first and second temperature zones according to the cooling capacity distribution ratio. The door opening detection unit is used to detect the door opening status, the door opening duration, and the door opening frequency per unit time.

[0060] The loading status detection unit is used to detect the storage loading rate of each temperature zone. This unit uses weight sensors installed on the shelves in each temperature zone to measure the load-bearing capacity of each shelf and compare it with a preset standard weight for a single item to obtain the loading rate of each temperature zone. The parameter storage and calculation unit is used to store historical operating data and calculate intermediate quantities such as the frost risk index and defrost index. The air duct distribution execution unit includes an electrically operated proportional air valve installed in the air duct between the first and second temperature zones. This electrically operated proportional air valve is driven by an analog control signal output from the main controller and can continuously adjust its opening from fully closed to fully open, thereby achieving continuous adjustment of the cooling capacity distribution ratio between the first and second temperature zones. The cooling capacity distribution ratio refers to the proportion of total cooling capacity generated by the evaporator. The ratio of cooling capacity allocated to a specific temperature zone to the total cooling capacity is equal to the sum of the cooling capacity allocation ratios of the first and second temperature zones. The cooling capacity allocation ratio is determined by the opening degree of the electric proportional damper. The larger the opening degree of the electric proportional damper, the more cooling air enters the first temperature zone through the air duct, resulting in a larger cooling capacity allocation ratio for the first temperature zone and a smaller cooling capacity allocation ratio for the second temperature zone. The main controller outputs corresponding analog control signals to adjust the opening degree of the electric proportional damper according to the temperature control requirements of each temperature zone, thereby changing the cooling capacity allocation ratio between the two temperature zones. Under normal operating conditions, the main controller comprehensively determines the opening degree of the electric proportional damper based on the temperature deviation of each temperature zone and the preset temperature zone usage weights, so that the cooling capacity allocation ratio matches the cooling demand of each temperature zone.

[0061] The control method is as follows Figure 1 As shown, it includes the following steps:

[0062] Step S1: The main controller collects operating parameters, normalizes the operating parameters, and then performs a weighted summation to obtain the frost risk index. When the frost risk index is greater than or equal to the preset risk threshold, the collaborative defrosting process is activated. Based on the material temperature estimation model, the material temperature estimates of the first and second temperature zones are estimated, and a steady state quantity is constructed.

[0063] The main controller periodically collects operating parameters through the temperature and humidity acquisition unit and the door opening detection unit. The operating parameters include ambient temperature, internal humidity, air temperature of the first temperature zone, air temperature of the second temperature zone, evaporator surface temperature, evaporator inlet and outlet temperature difference, door opening status, door opening duration, door opening frequency per unit time, and the current operating frequency and cumulative continuous operating time of the variable frequency compressor. The main controller also obtains the current loading rate of each temperature zone through the loading status detection unit. Specifically, the loading rate of each temperature zone is equal to the sum of the measured load-bearing capacity of all shelves in that temperature zone divided by the theoretical total load-bearing capacity of all shelves in that temperature zone when fully loaded. The theoretical total load-bearing capacity is equal to the sum of the rated storage capacity of each shelf in that temperature zone multiplied by the preset standard weight per unit. The preset standard weight per unit is set according to the full load weight of the standard storage unit. The loading rate ranges from zero to one, including zero and one. A loading rate of zero indicates that there is no storage in the temperature zone, and a loading rate of one indicates that the storage in the temperature zone is fully loaded.

[0064] The main controller calculates the frosting risk index based on the collected operating parameters through the parameter storage and calculation unit. Before calculating the frosting risk index, the main controller first normalizes each operating parameter, mapping physical quantities of different dimensions to a dimensionless range of zero to one. Normalization is used because the physical dimensions and numerical ranges of the aforementioned operating parameters differ significantly. For example, the dimension of the evaporator inlet and outlet temperature difference is degrees Celsius, the dimension of the humidity inside the chamber is percentage relative humidity, the dimension of door opening frequency is times per unit time, the dimension of door opening duration is time, and the dimension of the compressor's cumulative continuous operating time is also time. Directly weighting and summing these physical quantities with different dimensions and numerical ranges will cause parameters with larger numerical ranges to dominate the summation result, masking the contribution of parameters with smaller numerical ranges that still have a significant impact on frost risk. This results in the frost risk index failing to accurately reflect the true contribution of each influencing factor. By uniformly mapping each parameter to the dimensionless interval of zero to one, the influence of differences in dimensions and numerical ranges is eliminated. This ensures that the contribution of each parameter in the subsequent weighted summation process is entirely determined by its corresponding weight coefficient, thereby guaranteeing that the frost risk index can comprehensively assess the actual importance of each influencing factor.

[0065] Furthermore, the normalization process constrains the frosting risk index to a range of zero to one, facilitating direct comparison and judgment with preset risk thresholds. Specifically, the normalization method is as follows: for the evaporator inlet and outlet temperature difference, a preset maximum reference value for the evaporator inlet and outlet temperature difference is used as a benchmark. The current evaporator inlet and outlet temperature difference is divided by this maximum reference value, and the quotient is the normalized evaporator inlet and outlet temperature difference characteristic. If the quotient is greater than one, it is rounded down to one. For the chamber humidity, a 100% relative humidity is used as a benchmark. The current chamber humidity value is divided by one hundred, and the quotient is the normalized chamber humidity characteristic. For the door opening frequency per unit time, a preset maximum reference value for the door opening frequency per unit time is used as a benchmark. The current door opening frequency per unit time is divided by this maximum reference value, and the quotient is the normalized value. The normalized door opening frequency characteristic is calculated as follows: if the quotient is greater than one, then one is taken. For door opening duration, the maximum reference value for door opening duration is used as a benchmark. The cumulative door opening duration within the current statistical period is divided by this maximum reference value, and the resulting quotient is the normalized door opening duration characteristic. If the quotient is greater than one, then one is taken. For the cumulative continuous running time of the variable frequency compressor, the maximum reference value for the cumulative continuous running time of the compressor is used as a benchmark. The current cumulative continuous running time is divided by this maximum reference value, and the resulting quotient is the normalized compressor running time characteristic. If the quotient is greater than one, then one is taken. The above maximum reference values ​​are determined by multi-condition experiments based on the maximum reasonable values ​​that each physical quantity may encounter in actual operation during the system design phase, and are stored in the parameter storage and calculation unit.

[0066] The frosting risk index is calculated as follows: The normalized evaporator inlet and outlet temperature difference characteristic is multiplied by a preset first weighting coefficient; the normalized internal humidity characteristic is multiplied by a preset second weighting coefficient; the normalized door opening frequency characteristic is multiplied by a preset third weighting coefficient; the normalized door opening duration characteristic is multiplied by a preset fourth weighting coefficient; and the normalized compressor running time characteristic is multiplied by a preset fifth weighting coefficient. The sum of these values ​​is the frosting risk index. The reason for using a weighted summation method to calculate the frosting risk index is that evaporator frosting is the result of multiple factors working together. A single parameter cannot fully reflect the true level of frosting risk, while the weighted summation method can combine the contributions of multiple influencing factors into a single scalar value through linear superposition. The index retains the independent contribution information of each factor and reflects the relative importance of each factor to the frost risk through weighting coefficients. The above five operating parameters were selected as input features of the frost risk index because these five parameters characterize the main physical mechanisms affecting evaporator frost from five dimensions: the degree of evaporator heat exchange performance degradation, the water vapor content in the chamber, the frequency of external hot and humid air intrusion, the total amount of external hot and humid air intrusion, and the cumulative effect of continuous low-temperature operation of the evaporator. The temperature difference between the evaporator inlet and outlet directly reflects the degree of wind resistance increase and heat exchange area reduction caused by frost accumulation between the evaporator fins, and is the most direct characterization parameter of the degree of frost. The humidity in the chamber reflects the saturation of water vapor in the air within the temperature zone. The higher the humidity, the greater the driving force for water vapor to condense into frost on the low-temperature surface of the evaporator.

[0067] Door opening frequency and duration characterize the degree of intrusion of high-temperature and high-humidity external air into the chamber from two dimensions: frequency and duration. Each door opening introduces a large amount of warm and humid ambient air, significantly increasing the humidity inside the chamber and the frosting load on the evaporator. The cumulative continuous running time of the compressor reflects the duration of continuous operation of the evaporator at low temperatures. The longer the running time, the longer the evaporator surface remains at a low temperature, resulting in more continuous condensation and frost accumulation. These five parameters together constitute a comprehensive characterization of the evaporator frosting risk; the absence of any one parameter will lead to a blind spot in the frosting risk assessment. Due to the various input characteristics... All parameters have been normalized to the range of zero to one, and the sum of all weighting coefficients is one. Therefore, the range of the frosting risk index is between zero and one, including zero and one. The evaporator inlet and outlet temperature difference refers to the difference between the evaporator inlet and outlet temperatures. A larger value indicates a more severe decrease in the evaporator's heat exchange capacity and a higher probability of frosting. The humidity characteristic of the chamber is represented by the normalized humidity value directly measured by the temperature and humidity acquisition unit. The door opening frequency per unit time is obtained by the number of door opening events accumulated by the door opening detection unit within a preset statistical period. The door opening duration is obtained by the total door opening duration accumulated by the door opening detection unit within a preset statistical period. It was found that the longer the door is open, the greater the intrusion of hot and humid external air, and the stronger the effect on evaporator frosting. The cumulative continuous running time of the variable frequency compressor refers to the duration of uninterrupted operation since the compressor's most recent start-up. The aforementioned preset first, second, third, fourth, and fifth weighting coefficients correspond to the contributions of evaporator temperature difference, internal humidity, door opening frequency, door opening duration, and compressor running time, respectively. The sum of the five weighting coefficients is one. The initial values ​​of each weighting coefficient are determined during the system design phase based on various influencing factors. The contribution of each independent variable to the risk of frost was determined through multi-condition experiments. The initial values ​​of each weight coefficient were determined by multiple regression analysis. This method was chosen because, given a dataset of observations between multiple independent variables and a dependent variable, multiple regression analysis can solve for the optimal linear contribution coefficient of each independent variable to the dependent variable by minimizing the sum of squared residuals between the predicted and actual observed values. This method has the advantages of mature calculation process, unique solution, and statistically significant optimality, and is suitable for modeling the linear mapping relationship between multiple normalized feature quantities and the frost risk determination result in this scenario.

[0068] The specific calibration steps are as follows: First, during the system design phase, a refrigeration equipment experimental platform consistent with the actual product is built, and a complete temperature and humidity acquisition unit, door opening detection unit, and evaporator monitoring device are configured. Then, experimental schemes covering various typical operating conditions are designed, including combinations of different ambient temperature levels, different humidity levels inside the chamber, different door opening frequencies, and different door opening durations. Multiple repeated experiments are conducted under each combination of conditions to ensure the statistical reliability of the data. During each experimental group, time-series data of the evaporator inlet and outlet temperature difference, chamber humidity, door opening frequency, door opening duration, and the compressor's cumulative continuous operating time are recorded simultaneously. Simultaneously, the experimenters visually observe the frost thickness on the evaporator fins or measure the frost mass by weighing, recording whether the evaporator has reached the required defrosting level at each moment. This determination result is used as the observed value of the dependent variable. The moment when the required defrosting level is reached is marked as a positive frost sample, and the moment when it is not reached is marked as a negative frost sample. Next, the data collected under all experimental conditions are summarized, and each operating parameter is processed according to the aforementioned normalization method to obtain the normalized data. Five characteristic quantities are used as independent variables, and the frosting judgment result is used as the dependent variable to construct a multiple linear regression model. The least squares method is used to estimate the parameters of the regression model, and the five regression coefficients that minimize the sum of squared residuals are solved. The obtained regression coefficients are normalized so that their sum is one, and the result is the initial value of the five weight coefficients. Finally, the calibrated frosting risk index is verified using the reserved validation dataset. The accuracy of distinguishing between frosting and non-frosting conditions on the validation dataset is calculated. If the accuracy meets the preset calibration accuracy requirements, the calibration result is confirmed to be valid. Otherwise, the experimental condition combination is increased or the experimental conditions are adjusted and recalibrated. The initial values ​​of each weight coefficient are stored in the parameter storage and calculation unit and can be corrected in the subsequent step S5 based on historical operating data. The reason for adopting the online correction mechanism is that the laboratory calibration conditions cannot fully cover all operating condition combinations in actual use by users. By gradually adjusting the weight coefficients based on the defrosting effect feedback in actual operation, the frosting risk assessment can be gradually adapted to the usage habits and environmental conditions of specific users, thereby improving the long-term accuracy of frosting risk judgment.

[0069] The main controller compares the calculated frost risk index with a preset risk threshold. The preset risk threshold is determined during the system design phase based on multi-condition frost test data. A critical value is selected that can trigger the collaborative defrosting process in a timely manner at the beginning of frost without being too sensitive and causing frequent false triggers. Since the frost risk index ranges from zero to one, the preset risk threshold also ranges from zero to one and is stored in the parameter storage and calculation unit. When the frost risk index is less than the preset risk threshold, the main controller maintains the conventional time-sharing frequency conversion energy-saving control mode and continues to periodically perform the monitoring and calculation of this step. When the frost risk index is greater than or equal to the preset risk threshold, the main controller determines that the system has entered a high-humidity frost risk state, activates the collaborative defrosting process, and continues to construct the following stable state quantities.

[0070] The steady-state quantities refer to a set of state parameters used to characterize the degree of deviation of the storage temperature in the dual-temperature zones from their respective preset target temperatures, and the importance of each temperature zone in temperature control. This set of state parameters includes the temperature deviation of each temperature zone and the preset application weight of each temperature zone. The reason for constructing steady-state quantities is that the collaborative defrosting process involves multiple stages, such as defrosting timing determination, pre-stabilized temperature storage control, defrosting process monitoring, and differentiated recovery control after defrosting. Each stage needs to understand the current temperature deviation and importance information of each temperature zone to make control decisions. If this information is collected and calculated independently in each stage, it not only increases computational redundancy but may also lead to inconsistencies in control decisions due to differences in the timing of data collection at different stages. When the collaborative defrosting process is initiated, a stable state quantity is uniformly constructed and used as a temperature stability constraint throughout the entire process. This ensures that control decisions at each stage are based on consistent state information, improving the overall coordination and consistency of the collaborative defrosting process. Specifically, the temperature deviation of each temperature zone reflects the difference between the current storage temperature and the preset target temperature, while the preset temperature zone usage weight reflects the importance of that temperature zone in temperature control priority. The stable state quantity serves as the temperature stability constraint for subsequent steps such as defrosting timing determination, pre-stabilized temperature storage control, and post-defrosting differentiated recovery control, and is used throughout the entire collaborative defrosting process. The construction process of the stable state quantity includes three stages: temperature estimation, temperature deviation calculation, and temperature zone usage weight assignment, as detailed below.

[0071] The main controller estimates the material temperature of the first temperature zone and the material temperature of the second temperature zone based on the air temperature of the first temperature zone, the air temperature of the second temperature zone, the loading rate of each temperature zone provided by the loading status detection unit, and the material temperature estimate of each temperature zone recorded in the parameter storage and calculation unit in the previous sampling period.

[0072] The estimated temperature is obtained through a temperature estimation model based on a lumped parameter thermal equilibrium method. This method is used because the Biot number of the contents inside the storage unit is small, meaning the thermal resistance inside the contents is much smaller than the convective thermal resistance between the outer surface of the storage unit and the air in the temperature zone. Under these conditions, the temperature distribution inside the contents can be approximated as uniform. There is no need to solve for the temperature field distribution inside the contents; simply analyzing the entire storage unit as a lumped heat body with a uniform temperature is sufficient to obtain a sufficiently accurate temperature estimation result. Compared to distributed parameter models and finite element numerical simulation methods, this method requires very little computation, only one... The material temperature update for a single sampling period can be completed with only one multiplication and one addition, making it perfectly suitable for real-time operation on the embedded computing platform of the main controller without consuming excessive computing resources and storage space. At the same time, the model structure of this method is simple, containing only one parameter that needs to be calibrated, namely the thermal response coefficient. The calibration process is simple and the physical meaning of the calibration results is clear, which facilitates the establishment of parameter lookup tables for online adaptive adjustment under different loading rates. Its basic principle is that the storage unit is regarded as a lumped heat body with a certain heat capacity. The storage unit and the air in the temperature zone exchange heat through convection. The rate of change of the storage temperature is proportional to the difference between the storage temperature and the temperature of the air in the temperature zone.

[0073] The specific calculation method of the material temperature estimation model is as follows: the estimated material temperature value of a certain temperature zone in the current sampling period is equal to the estimated material temperature value of the same temperature zone in the previous sampling period, plus the product of the thermal response coefficient of the temperature zone and the difference between the air temperature of the same temperature zone measured by the temperature and humidity acquisition unit in the current sampling period and the estimated material temperature value of the previous sampling period. The effect of this recursive calculation method is that when the air temperature of the temperature zone is higher than the current estimated material temperature value, the difference is positive, and the estimated material temperature value gradually increases, simulating the physical process of the storage unit absorbing heat from the air and rising in temperature. When the air temperature of the temperature zone is lower than the current estimated material temperature value, the difference is negative, and the estimated material temperature value gradually decreases, simulating the physical process of the storage unit releasing heat to the air and cooling down. The thermal response coefficient controls the rate at which the material temperature approaches the air temperature in each sampling period, thus accurately reflecting different loading rates and storage conditions. The difference in thermal inertia of storage units under volume conditions; the material temperature estimation model needs to set an initial material temperature estimate when the system is first powered on or reset. This initial material temperature estimate is the arithmetic mean of the air temperature in the temperature zone within the first ten sampling periods continuously collected by the temperature and humidity acquisition unit after the system is powered on. The reason for using the arithmetic mean of multiple sampling periods instead of a single sampling value as the initial value is that the single sampling value of the temperature sensor is affected by sensor noise, local air temperature fluctuations and accidental factors at the sampling time, which may deviate from the true average temperature of the air in the temperature zone. By taking the arithmetic mean of the measurement values ​​of ten consecutive sampling periods, the above random fluctuations can be effectively smoothed, and an initial estimate closer to the true temperature of the air in the temperature zone can be obtained, thereby reducing the estimation error of the material temperature estimation model in the initial stage of startup and enabling the model to converge to an accurate material temperature tracking state more quickly.

[0074] The thermal response coefficient reflects the heat exchange rate between the storage unit and the air in the temperature zone, and its value is related to the loading rate and storage volume of the storage unit within the temperature zone. The thermal response coefficient is determined by a combination of offline calibration and online table lookup. This method is used because the value of the thermal response coefficient is significantly affected by the loading rate. When the loading rate is different, the total heat capacity of the storage unit in the temperature zone and the airflow distribution between the storage units change, resulting in a change in the thermal response coefficient. The relationship between the thermal response coefficient and the loading rate is difficult to derive analytically through theoretical derivation, so it is necessary to establish the correspondence between the two through experimental calibration. Offline calibration can obtain high-precision calibration data under controlled experimental conditions, while online table lookup can quickly obtain the corresponding thermal response coefficient value based on the real-time changes in the loading rate during actual operation. The combination of the two methods ensures both calibration accuracy and real-time requirements.

[0075] During the system design phase, a standard liquid temperature pack was used as the reference measurement device for material temperature. The standard liquid temperature pack is a sealed container containing a standard liquid with a heat capacity similar to that of the stored contents and an internal temperature sensor. The standard liquid temperature pack was placed at a representative position on the temperature zone shelf, and multiple sets of heating and cooling experiments were conducted under different loading rates. The specific calibration steps are as follows: First, several calibration loading rate levels covering the complete range from zero to one were selected. At each calibration loading rate level, a corresponding number of standard storage units and standard liquid temperature packs were placed on the temperature zone shelf, with the standard liquid temperature pack placed at the center of the shelf to represent the average material temperature response characteristics under that loading rate condition. Then, heating and cooling experiments were conducted at each calibration loading rate level. In the heating experiment, the temperature of the air in the temperature zone was increased from a low steady state to a high steady state; in the cooling experiment, the temperature of the air in the temperature zone was decreased from a high steady state. To reach a low-temperature steady state, in each experimental group, time-series data of the air temperature in the temperature zone and the measured temperature of the standard liquid temperature bulb were recorded simultaneously, with the measured temperature of the standard liquid temperature bulb serving as the true reference value for the material temperature. Next, for the experimental data at each calibrated loading rate level, the theoretical output of the material temperature estimation model was compared with the measured temperature of the standard liquid temperature bulb. The least squares method was used to minimize the mean square error between the two, thereby determining the calibrated value of the thermal response coefficient under that loading rate condition. The reason for using the least squares method is that it determines the model parameters by minimizing the sum of squared errors between the model's predicted and measured values. This method possesses the statistical characteristics of optimal unbiased estimation in linear parameter estimation problems, enabling the acquisition of parameter values ​​that maximize the model's prediction accuracy given experimental data. Furthermore, the calculation process is simple, requiring only the solution of a univariate optimization problem concerning the thermal response coefficient, making it suitable for calibrating single-parameter models.

[0076] By repeating the above calibration process at multiple different loading rate levels, a correspondence table between the thermal response coefficient and the loading rate is established. This correspondence table is stored in the parameter storage and calculation unit. During actual operation, the main controller looks up the corresponding thermal response coefficient value in the above correspondence table based on the current loading rate provided by the loading status detection unit. If the current loading rate is between two adjacent calibration loading rates, the corresponding thermal response coefficient is obtained using a linear interpolation method. The reason for using the linear interpolation method is that the thermal response coefficient changes approximately linearly with the loading rate between adjacent calibration points. The linear interpolation method can achieve a smaller interpolation rate without adding additional calibration experiments. The method obtains an estimated value of the thermal response coefficient for any loading rate with minimal computational complexity, requiring only one multiplication and one addition, making it suitable for real-time execution in the main controller. The thermal response coefficient ranges from greater than zero to less than one. The higher the loading rate or the larger the storage volume, the smaller the thermal response coefficient, indicating greater thermal inertia and slower temperature response of the storage unit. The physical meaning of this characteristic is that the higher the loading rate, the greater the total heat capacity of the storage unit within the temperature zone. Under the same air temperature change conditions, the rate of change of the storage temperature is slower. The temperature estimation model accurately reflects this physical law through a smaller thermal response coefficient. The above calculation method is applicable to the first and second temperature zones, respectively.

[0077] The main controller calculates the temperature deviation of the first temperature zone and the temperature deviation of the second temperature zone based on the estimated temperatures of the first and second temperature zones, respectively. The temperature deviation of the first temperature zone is equal to the estimated temperature of the first temperature zone minus the preset target temperature of the first temperature zone, and the temperature deviation of the second temperature zone is equal to the estimated temperature of the second temperature zone minus the preset target temperature of the second temperature zone. The preset target temperature of the first temperature zone is a short-term storage temperature setting value, which is set by the user through the operation panel according to the type of stored item and stored in the parameter storage and calculation unit. The preset target temperature of the second temperature zone is a long-term storage temperature setting value, which is set by the user through the operation panel according to the long-term storage requirements of the stored item and stored in the parameter storage and calculation unit. A positive temperature deviation indicates that the temperature of the item is higher than the preset target temperature, and a negative temperature deviation indicates that the temperature of the item is lower than the preset target temperature.

[0078] The main controller assigns preset usage weights to the two temperature zones based on their intended use. Since the first temperature zone is for short-term access, users are more sensitive to short-term access temperatures than to long-term storage temperatures. Therefore, the preset usage weight for the first temperature zone is set to be greater than that for the second temperature zone. The preset usage weights for the first and second temperature zones are determined during the system design phase based on the difference in sensitivity of the short-term access and long-term storage temperature zones to temperature deviations. The short-term access temperature zone is given a higher weight because it directly affects the user's immediate experience, while the long-term storage temperature zone is given a lower weight because the stored items are more tolerant to short-term temperature fluctuations. The sum of the usage weights for the two temperature zones is one, and its value is pre-stored in the parameter storage and calculation unit.

[0079] At this point, the construction of the steady-state variables is complete. The main controller uses the temperature deviation of the first temperature zone and the temperature deviation of the second temperature zone obtained in this step, along with the preset application weights of the first and second temperature zones, to form the steady-state variables, which serve as the temperature stability constraints for subsequent steps, and then proceeds to step S2.

[0080] Step S2: Calculate the defrost index based on the steady state quantity, compare the defrost index with the preset window threshold, and determine whether to defrost immediately or delay defrosting.

[0081] After the main controller completes the construction of the steady state variables in step S1, it further calculates the defrost index to determine whether it is suitable to perform defrost operation at the current moment. The purpose of this step to determine whether to perform defrost immediately or delay defrost is that the risk of evaporator frosting has been confirmed in step S1 to reach the level that requires defrosting. However, the defrost operation itself will cause the evaporator to stop cooling and cause the temperature zone to rise. Therefore, it is not suitable to perform defrost immediately at all times. It is necessary to comprehensively consider three dimensions: the current electricity price economy, the user door opening activity in the short period of time in the future, and the difficulty of temperature zone recovery after defrost. The time with the least comprehensive impact on system energy consumption, user interference, and material temperature stability should be selected to perform defrost.

[0082] When the defrost index reaches the preset window threshold, it indicates that the current situation is relatively favorable in all three dimensions mentioned above. The main controller determines to defrost immediately and directly enters step S3 to perform pre-stabilized temperature storage and defrosting actions. When the defrost index does not reach the preset window threshold, it indicates that the current situation is unfavorable in one or more dimensions of electricity price economy, user activity, or recovery difficulty. The main controller determines to delay defrosting and enters the delayed defrosting stage. During this stage, basic cooling is maintained at a limited frequency, and the system continues to wait for a more favorable defrosting opportunity until the defrost index reaches the preset window threshold before entering step S3. Therefore, regardless of whether the determination result is immediate defrosting or delayed defrosting, the pre-stabilized temperature storage and defrosting actions are ultimately performed through step S3. The difference between the two is that under the immediate defrosting path, the main controller directly enters step S3 after the determination is completed, while under the delayed defrosting path, the main controller needs to go through a limited operation waiting stage before entering step S3 after the conditions are met. Before calculating the defrost index, the main controller first determines the normalized value of each component.

[0083] The defrosting economic weight for the current time period is determined by the preset electricity price level corresponding to the current time period. The preset electricity price level is divided into several levels by the system according to the time-of-use electricity price policy published by the local power department. The electricity value corresponding to each level is pre-stored in the parameter storage and calculation unit. Users can also manually set or update the electricity price level information for each time period through the operation panel. The specific value of the defrosting economic weight is obtained by mapping each electricity price level to the range of zero to one in a linear normalization manner. That is, the highest electricity price level corresponding to the pre-stored value is used as the normalization benchmark, the highest electricity price level is mapped to zero, the lowest electricity price level is mapped to one, and the intermediate levels are mapped in a linear proportion. The lower the electricity price, the greater the defrosting economic weight, indicating that the defrosting is more economical during low electricity price periods.

[0084] The predicted user door-opening activity within the preset prediction time window is obtained by the parameter storage and calculation unit through statistical averaging of historical door-opening frequency data recorded by the door-opening detection unit. The reason for using the historical averaging method for prediction is that user door-opening behavior has significant time periodic characteristics. The same user usually has similar door-opening habits at the same time of day. For example, the frequency of door opening before and after meals is usually higher than at night. This periodicity makes it reasonable to use the statistical average of historical data to predict door-opening activity in the short term. This method does not require the establishment of a complex user behavior prediction model. It can obtain a prediction result with practical reference value through simple arithmetic averaging. The computational load is minimal and does not rely on a large amount of training data, making it suitable for real-time execution on the embedded computing platform of the main controller. The prediction time window is set and stored by the system according to the door-opening statistical cycle.

[0085] Specifically, the parameter storage and calculation unit records the door opening frequency data within the same time window as the current period over the past several days, calculates its arithmetic mean, and then normalizes it based on a preset maximum reference value for door opening activity. The average value is divided by the preset maximum reference value for door opening activity, and the resulting quotient is the predicted value of user door opening activity within the preset prediction time window in the future. If the quotient is greater than one, it is rounded down to one. The value ranges from zero to one, including zero and one. The larger the value, the higher the probability of users opening the door in the predicted short period of time. At this time, defrosting will face greater temperature interference. The effect of incorporating the predicted value into the defrosting index calculation is that the system can avoid performing defrosting during periods of active user door opening, reducing the additional interference of external humid and hot air intrusion caused by user door opening during the defrosting process on the temperature of the temperature zone, thereby reducing the difficulty and energy consumption of temperature recovery after defrosting.

[0086] The calculation method for the post-defrost recovery difficulty index is as follows: First, the two components are normalized. The reason for using the positive material temperature deviation and environmental heat load as the two components to calculate the post-defrost recovery difficulty index is that the difficulty of temperature recovery in the temperature zone after defrost mainly depends on two aspects. One is the degree to which the material temperature in each temperature zone is higher than the preset target temperature before defrost. The greater the difference between the material temperature and the preset target temperature, the greater the temperature difference that needs to be restored after defrost, and the more cooling capacity and recovery time are required. The other is the level of the ambient temperature relative to the preset target temperature of the temperature zone. The higher the ambient temperature, the more heat penetrates into the temperature zone through the cabinet wall and seals. The refrigeration system needs to overcome an additional environmental heat load during the recovery process, and the slower the recovery speed. These two components comprehensively characterize the main influencing factors of post-defrost recovery difficulty from the perspectives of the internal state of the system and the external environmental conditions, respectively.

[0087] The maximum positive temperature deviation between the two temperature zones is used as the characteristic quantity of temperature recovery requirement. The positive temperature deviation, rather than its absolute value, is used here because the recovery difficulty after defrosting is only related to the degree to which the temperature exceeds the preset target temperature. When the temperature is below the preset target temperature, the temperature deviation is negative, and this temperature zone has actually formed a cold storage buffer. The temperature rise after defrosting is precisely the process of returning to the preset target temperature, and does not constitute a recovery difficulty; on the contrary, it is conducive to temperature stability after defrosting. Therefore, the recovery difficulty only depends on the temperature exceeding the preset target temperature. It generates a positive contribution; the positive material temperature deviation of each temperature zone refers to the difference between the estimated material temperature of that temperature zone and the corresponding preset target temperature. When the estimated material temperature of that temperature zone is less than or equal to the corresponding preset target temperature, the positive material temperature deviation of that temperature zone is zero. The reason for selecting the maximum value of the positive material temperature deviation of two temperature zones as the representative value is that the recovery difficulty should be based on the state of the most unfavorable temperature zone. If the average value of the two temperature zones is used as the standard, the recovery difficulty may be underestimated, resulting in defrosting still being triggered under unfavorable conditions. The preset maximum reference value of material temperature deviation is used. Normalization is performed based on the baseline by dividing the maximum positive temperature deviation between the two temperature zones by the preset maximum reference value for temperature deviation. The quotient is the normalized temperature deviation characteristic quantity. If the quotient is greater than one, it is rounded to one. The difference between the ambient temperature and the average preset target temperature of the two temperature zones is calculated by subtracting half the sum of the preset target temperatures of the first and second temperature zones from the ambient temperature measured by the temperature and humidity acquisition unit. A negative difference indicates that the ambient temperature is lower than the average target temperature, meaning the ambient heat load is lower and recovery is easier. Therefore, the difference is normalized by taking the larger value between the difference and zero. That is, if the difference is less than zero, it is taken as zero. Based on the preset maximum reference value of the ambient temperature difference, the difference after zeroing is divided by the preset maximum reference value of the ambient temperature difference. The quotient is the normalized ambient heat load characteristic quantity. If the quotient is greater than one, it is taken as one. The preset maximum reference value of the material temperature deviation and the preset maximum reference value of the ambient temperature difference are determined by the system design stage through multi-condition experiments based on the maximum reasonable values ​​that may occur in actual operation, and are stored in the parameter storage and calculation unit.

[0088] The normalized material temperature deviation characteristic is multiplied by a preset first recovery difficulty weighting coefficient, and the normalized environmental heat load characteristic is multiplied by a preset second recovery difficulty weighting coefficient. The sum is the post-defrost recovery difficulty index. Since all input characteristic quantities have been normalized to the range of zero to one, and the sum of the preset first recovery difficulty weighting coefficient and the preset second recovery difficulty weighting coefficient is one, the value range of the post-defrost recovery difficulty index is between zero and one, including zero and one. The preset first recovery difficulty weighting coefficient and the preset second recovery difficulty weighting coefficient are calibrated by the system design stage according to the degree of influence of material temperature deviation and environmental heat load on the post-defrost recovery difficulty. The sum of the two is one, and their value is stored in the parameter storage and calculation unit.

[0089] The defrost index is calculated by multiplying the defrost economic weight of the current period by a preset first window weight coefficient, adding the product of the first reverse activity value multiplied by a preset second window weight coefficient, and adding the product of the second reverse recovery difficulty value multiplied by a preset third window weight coefficient. The sum is the defrost index. The first reverse activity value is one minus the predicted user door opening activity value, and the second reverse recovery difficulty value is one minus the post-defrost recovery difficulty index. The reason for using these three dimensions as inputs for the defrost index is that the timing of defrosting needs to achieve a balance between energy consumption economy, user experience, and temperature stability. The defrost economic weight reflects the electricity cost of defrosting in the current period. Performing defrosting during periods of low electricity prices can reduce the electricity cost of the defrosting process itself and the post-defrost temperature recovery process. For refrigeration equipment that operates for a long time, the cumulative energy-saving effect is significant. The predicted user door opening activity reflects the likelihood of interference from user door opening during the defrosting process. Performing defrosting during periods of low user door opening activity can reduce the interference of external hot and humid air intrusion on the defrosting effect and temperature zone, improve defrosting efficiency, and reduce the difficulty of temperature recovery after defrosting. The post-defrosting recovery difficulty index reflects the time and energy required to restore the temperature zone to the preset target temperature after defrosting. Performing defrosting under conditions of low recovery difficulty can shorten the recovery time, reduce the duration of temperature deviation from the preset target temperature, and ensure the temperature quality of stored items. The reason for subtracting the predicted user door opening activity and the post-defrosting recovery difficulty index from each is that the larger the original values ​​of these two components, the more unfavorable the conditions for defrosting. The design intent of the defrosting index is that the larger the value, the more suitable the defrosting is. Therefore, it is necessary to perform an inverse mapping of these two components so that the smaller the value, the greater the positive contribution to the defrosting index.

[0090] Since the defrosting economy weight, the predicted value of user door opening activity, and the post-defrosting recovery difficulty index have all been normalized to the range of zero to one, and the sum of the preset first window weight coefficient, the preset second window weight coefficient, and the preset third window weight coefficient is one, the value range of the defrosting index is between zero and one, including zero and one. The aforementioned preset first window weight coefficient, preset second window weight coefficient, and preset third window weight coefficient correspond to the defrosting economy contribution, user activity contribution, and recovery difficulty contribution, respectively. Their values ​​are determined by the system design stage through a comprehensive evaluation based on the importance of the defrosting timing selection in three dimensions: defrosting economy, user usage interference, and recovery difficulty, and are stored in the parameter storage and calculation unit.

[0091] The main controller compares the calculated defrost index with a preset window threshold. The preset window threshold is determined by the system design phase based on multi-condition operation experiments. The threshold value that can trigger defrost under the optimal conditions of defrosting economy, user interference and recovery difficulty is selected as the preset window threshold. Since the value range of the defrost index is from zero to one, the preset window threshold is also between zero and one. This value is stored in the parameter storage and calculation unit and can be corrected in step S5 based on historical operation data.

[0092] When the defrosting index is greater than or equal to the preset window threshold, the main controller determines to defrost immediately. That is, the current moment is favorable in terms of the three dimensions of electricity price economy, user activity and recovery difficulty, and is suitable as a defrosting window. The main controller directly enters step S3 to perform pre-stabilized temperature storage and defrosting actions.

[0093] When the defrost index is less than the preset window threshold, the main controller determines that defrosting is delayed, indicating unfavorable conditions at the current moment, and enters the delayed defrost stage. During the delayed defrost stage, the main controller limits the operating frequency of the inverter compressor to a preset restricted frequency range. The lower limit of the restricted frequency range is the preset minimum allowable operating frequency of the compressor, and the upper limit is the preset upper limit of the delayed defrost stage frequency. The preset minimum allowable operating frequency of the compressor is determined by the technical specifications provided by the compressor manufacturer and is the minimum frequency value to ensure stable operation of the compressor. The preset upper limit of the delayed defrost stage frequency is less than the rated maximum frequency of the compressor. Its value is determined by the system design stage based on the balance requirement of maintaining basic cooling capacity and limiting the rate of evaporator frosting during the delayed defrost stage, and is stored in the parameter storage and calculation unit. At the same time, the main controller adjusts the opening of the electric proportional damper through the air duct distribution execution unit to provide slight supplemental cooling to the preset temperature zone with a higher application weight, that is, to increase the proportion of cooling capacity distribution in that temperature zone.

[0094] Specifically, the main controller first calculates the target cooling capacity allocation ratio for the delayed defrost stage based on the temperature deviation of each of the two temperature zones and the preset temperature zone usage weights. The main controller then determines the direction of the temperature deviation for each temperature zone and calculates the supplementary cooling demand for that zone. Since a positive temperature deviation indicates that the temperature is higher than the preset target temperature, there is a cooling demand in that zone, while a negative temperature deviation indicates that the temperature is lower than the preset target temperature, there is no supplementary cooling demand. Therefore, the supplementary cooling demand for each temperature zone is determined as follows: when the temperature deviation of a temperature zone is greater than zero, the supplementary cooling demand for that zone is equal to the temperature deviation multiplied by the preset temperature zone usage weight. The reason for using the product of the temperature deviation and the temperature zone usage weight as the supplementary cooling demand is that the supplementary cooling demand needs to reflect two aspects simultaneously: one is the degree to which the temperature of the zone deviates from the preset target temperature; a larger temperature deviation indicates a larger cooling gap in that zone, requiring more supplementary cooling capacity. The other aspect... The first aspect represents the importance of the temperature zone in temperature control. A higher usage weight for a temperature zone indicates a greater impact of its temperature stability on user experience, and it should be prioritized during the delayed defrost phase when cooling resources are limited. Multiplying these two factors ensures that the demand for supplemental cooling is only high when both the object temperature deviation and the temperature zone usage weight are large. This avoids over-allocation of cooling capacity due to a high usage weight but a small object temperature deviation, and also avoids neglecting high-priority temperature zones due to a large object temperature deviation but a low usage weight. This achieves a comprehensive balance between the urgency of cooling needs and the importance of the temperature zone. A higher demand for supplemental cooling indicates a greater degree to which the object temperature in that temperature zone exceeds the target temperature, and a higher importance for temperature control in that zone. It should be prioritized for cooling replenishment during the delayed defrost phase. When the object temperature deviation in a temperature zone is less than or equal to zero, the object temperature in that zone is already at or below the preset target temperature, and no additional cooling is required. The demand for supplemental cooling in that temperature zone is zero.

[0095] The main controller compares the cooling demand of the two temperature zones and prioritizes the zone with the higher cooling demand. When the cooling demand of both temperature zones is zero, meaning the object temperature in both zones is at or below the preset target temperature, the main controller maintains the current cooling capacity allocation ratio. When the cooling demand of the two temperature zones is not zero, the main controller determines the adjustment range of the cooling capacity allocation ratio based on the difference in cooling demand between the two temperature zones. This adjustment range is equal to the quotient obtained by multiplying the preset delayed defrost cooling benchmark allocation increment by the cooling demand of the priority cooling zone and dividing by the sum of the cooling demands of the two temperature zones. The preset delayed defrost cooling benchmark allocation increment is determined during the system design phase based on the maximum additional cooling capacity percentage required to maintain temperature stability in the priority temperature zone during the delayed defrost phase. This value is obtained through multi-condition experimental calibration and stored in the parameter storage. In the calculation unit, the adjustment range is greater than zero and less than or equal to the preset delayed defrost cooling supplementary allocation increment. When only one temperature zone has a cooling supplementary demand greater than zero and the other temperature zone has a cooling supplementary demand of zero, the adjustment range is equal to the preset delayed defrost cooling supplementary allocation increment. When both temperature zones have a cooling supplementary demand greater than zero and the cooling supplementary demand of the priority cooling supplementary temperature zone is much greater than that of the other temperature zone, the adjustment range approaches the preset delayed defrost cooling supplementary allocation increment. When the cooling supplementary demand of the two temperature zones is close, the adjustment range is about half of the preset delayed defrost cooling supplementary allocation increment. The target cooling capacity allocation ratio is determined by increasing the cooling capacity allocation ratio of the priority cooling supplementary temperature zone by the above adjustment range based on the current value, and correspondingly decreasing the cooling capacity allocation ratio of the other temperature zone by the same adjustment range, so that the sum of the cooling capacity allocation ratios of the two temperature zones is still one.

[0096] Based on the target cooling capacity allocation ratio, the main controller adjusts the opening of the electric proportional damper to favor the priority cooling zone by outputting corresponding analog control signals. Since the opening of the electric proportional damper is positively correlated with the cooling capacity allocation ratio of the first temperature zone, when the priority cooling zone is the first temperature zone, the main controller increases the opening of the electric proportional damper; when the priority cooling zone is the second temperature zone, the main controller decreases the opening of the electric proportional damper, thereby increasing the proportion of cooling capacity obtained by the priority cooling zone to the total cooling capacity, thus prioritizing the maintenance of temperature stability in this zone during the delayed defrosting phase. During the delayed defrosting phase, the main controller continuously and periodically recalculates the defrosting index until the defrosting index is greater than or equal to the preset window threshold, at which point it exits the delayed defrosting phase and proceeds to step S3 to perform pre-stabilized temperature storage and defrosting actions.

[0097] Step S3: When it is determined that defrosting should be done immediately or delayed defrosting should be stopped, the estimated temperature of each temperature zone is reduced to the pre-stabilized temperature target before defrosting is started. A dynamic duration upper limit is set based on operating parameters and stable state quantities. During defrosting, the estimated temperature is continuously monitored, and defrosting interruption conditions are determined according to the dynamic duration upper limit. Defrosting ends when the defrosting interruption conditions are triggered. Specifically, as follows... Figure 2 As shown.

[0098] In step S2, regardless of whether the main controller enters this step directly via the immediate defrost path or enters it after exiting the delayed defrost stage, it first enters the pre-temperature stabilization stage. The purpose of the pre-temperature stabilization stage is to pre-lower the temperature zone to a level below the preset target temperature by utilizing the thermal inertia of the contents before defrosting begins, forming a cold storage buffer so that the temperature can still be maintained within an acceptable range when the temperature rises during the subsequent defrosting process. The reason for adopting the pre-temperature stabilization cold storage strategy is that during the defrosting process, the evaporator stops cooling and the defrosting execution unit releases heat to the evaporator, and the air temperature in the temperature zone inevitably rises. Due to the large thermal inertia of the storage unit, the temperature rise is delayed but lasts for a long time. If pre-cooling is not performed before defrosting, the temperature will rise from the preset target temperature during the defrosting process. Temperature fluctuations can easily exceed the user's acceptable range, affecting the short-term access quality and long-term preservation quality of stored items. By pre-cooling the items to below the preset target temperature before defrosting, it's equivalent to pre-storing a certain amount of cold energy in the storage unit. Although the item temperature rises during defrosting, because the starting temperature is lower than the preset target temperature, there is a greater temperature margin during the rise, allowing it to remain within an acceptable range near the preset target temperature for a longer period. This effectively reduces the impact of defrosting on the temperature quality of stored items. The effect of this strategy is that it transforms the inevitable temperature rise during defrosting into a recovery from below the preset target temperature towards the preset target temperature, rather than a deviation from the preset target temperature towards a higher temperature, significantly improving the temperature stability of items during defrosting.

[0099] The main controller determines the pre-stabilization targets for the first and second temperature zones based on the preset temperature zone application weights and material temperature deviations in the steady-state quantities constructed in step S1. The pre-stabilization target for each temperature zone is equal to the preset target temperature of that zone minus the pre-cooling compensation amount. The pre-cooling compensation amount represents the extent to which the material temperature needs to be reduced below the preset target temperature during the pre-stabilization stage. The pre-cooling compensation amount for each temperature zone is calculated by multiplying the preset baseline pre-cooling compensation amount by the preset application weight of that temperature zone, and then dividing by the larger of the preset application weights of the two temperature zones. The quotient is the pre-cooling compensation amount for that temperature zone. The preset baseline pre-cooling compensation amount is determined by... During the system design phase, the average rise in air temperature in the temperature zone during a typical defrost process of the evaporator is determined. A preset proportion of the maximum rise in air temperature in the temperature zone during a typical defrost process is taken as the initial value of the benchmark precooling compensation amount. This initial value is stored in the parameter storage and calculation unit and can be corrected in step S5 based on historical operating data. The precooling compensation amount is positively correlated with the preset temperature zone usage weight, that is, the larger the preset temperature zone usage weight, the larger its precooling compensation amount. Since the preset first temperature zone usage weight is set to be greater than the preset second temperature zone usage weight in step S1, the precooling compensation amount of the first temperature zone is greater than the precooling compensation amount of the second temperature zone.

[0100] During the pre-stabilization phase, the main controller increases the operating frequency of the variable frequency compressor to a preset pre-stabilization frequency. This preset pre-stabilization frequency is higher than the normal operating frequency. Its value is determined during the system design phase based on the cooling capacity required for the compressor to reduce the temperature zone to the pre-stabilization target within a short time. The selected frequency value, which meets the pre-stabilization aging requirements without exceeding the compressor's rated maximum frequency, is stored in the parameter storage and calculation unit. Simultaneously, the main controller adjusts the opening of the electric proportional damper through the air duct distribution execution unit, increasing the cooling capacity allocation ratio of the temperature zone with a higher preset application weight, thus prioritizing that temperature zone to reach the pre-stabilization target. Specifically, the main controller increases the cooling capacity allocation ratio of the temperature zone with a higher application weight by a preset pre-stabilization cold storage allocation increment based on the current value, while correspondingly decreasing the cooling capacity allocation ratio of the other temperature zone by the same increment, ensuring that the sum of the cooling capacity allocation ratios of the two temperature zones remains one.

[0101] The preset pre-stabilized temperature storage cold distribution increment is determined during the system design phase based on the proportion of additional cooling capacity required for the priority temperature zone to quickly reach the pre-stabilized temperature target within the pre-stabilized temperature phase. This value is obtained through multi-condition experimental calibration and stored in the parameter storage and calculation unit. The main controller adjusts the opening of the electric proportional air valve by outputting corresponding analog control signals according to the adjusted cooling capacity distribution ratio. Since the opening of the electric proportional air valve is positively correlated with the cooling capacity distribution ratio of the first temperature zone, when the temperature zone with a higher preset application weight is the first temperature zone, the main controller increases the opening of the electric proportional air valve. When the temperature zone with a higher preset application weight is the second temperature zone, the main controller decreases the opening of the electric proportional air valve. This allows the temperature zone with a higher preset application weight to receive more cooling capacity, accelerating the temperature drop of the material in that temperature zone to the pre-stabilized temperature target.

[0102] The main controller continuously monitors the estimated material temperature values ​​of the two temperature zones. When the estimated material temperature value of the temperature zone with the greater application weight reaches its pre-stabilization target, that is, when the estimated material temperature value of the first temperature zone is less than or equal to the pre-stabilization target of the first temperature zone, the main controller determines that the pre-stabilization is completed and then starts the defrosting execution unit to defrost the evaporator. The defrosting execution unit can adopt electric heating defrosting or hot gas bypass defrosting.

[0103] While initiating defrosting, the main controller sets a dynamic upper limit for the current defrosting duration based on the current degree of frost on the evaporator and the temperature deviations of the first and second temperature zones in the steady-state quantities established in step S1. The reason for using a dynamic upper limit instead of a fixed defrosting duration is that the actual degree of frost on the evaporator and the temperature deviations of each temperature zone differ in different defrosting cycles. Using a fixed defrosting duration would lead to unnecessary over-defrosting when frost is light, wasting energy and increasing temperature fluctuations in the zones, while it could cause problems when frost is heavy. Insufficient defrosting results in ineffective removal of frost. By dynamically adjusting the upper limit of defrosting time based on the current degree of frost and temperature deviation, the defrosting time can be shortened as much as possible while ensuring defrosting effectiveness, reducing the impact of defrosting on temperature stability, and achieving an optimal balance between sufficient defrosting and temperature stability. The current degree of frost on the evaporator is characterized by a frost characteristic quantity, which is calculated by dividing the current temperature difference between the evaporator inlet and outlet by a preset maximum reference value. The quotient is the frost characteristic quantity; if the quotient is greater than one, it is rounded to one. The value of this characteristic quantity ranges from zero to one, including zero and one. A larger value indicates more severe frost. The reason for choosing the evaporator inlet and outlet temperature difference as the parameter for representing the degree of frost is that the accumulation of frost between the evaporator fins increases the resistance of airflow through the evaporator and reduces the effective heat exchange area, leading to an increase in the temperature difference between the air inlet and outlet sides of the evaporator. Therefore, the evaporator inlet and outlet temperature difference can indirectly but sensitively reflect the actual degree of frost on the evaporator, and this parameter can be directly obtained through existing temperature and humidity acquisition units without the need for additional sensors. The calculation method for the upper limit of dynamic duration is as follows: based on the preset baseline defrosting duration, add the product of the preset frost degree adjustment coefficient and the frost characteristic quantity, and then subtract the product of the preset material temperature deviation adjustment coefficient and the maximum value of the positive material temperature deviations of the two temperature zones. The resulting value is the upper limit of dynamic duration. Among them, the positive material temperature deviation of each temperature zone refers to the difference between the estimated material temperature of the temperature zone and the preset target temperature corresponding to the temperature zone. When the estimated material temperature of the temperature zone is less than or equal to the preset target temperature corresponding to the temperature zone, the positive material temperature deviation of the temperature zone is zero.

[0104] For example, the formula for calculating the dynamic duration limit is expressed as:

[0105] ;

[0106] in, This is a dynamic duration limit; This is the preset baseline defrosting time; This is the preset frosting level adjustment coefficient; For frosting characteristic quantities; This is the preset temperature deviation adjustment coefficient; It represents the maximum value of the positive temperature deviation between the two temperature zones.

[0107] The formula for calculating the characteristic value of frosting is:

[0108] ;

[0109] in, This represents the current temperature difference between the inlet and outlet of the evaporator. This is the preset maximum reference value for the temperature difference between the evaporator inlet and outlet. To obtain The smaller value among 1.

[0110] The positive temperature deviation of each temperature zone is defined as follows:

[0111] ;

[0112] in, For the first Positive temperature deviation in the temperature range; For the first Estimated material temperature in the temperature range; For the first The preset target temperature of the temperature zone To obtain The larger of 0.

[0113] The maximum value of the positive temperature deviation between the two temperature zones is:

[0114] ;

[0115] in, This represents the positive temperature deviation of the first temperature zone. This represents the positive temperature deviation in the second temperature zone. To obtain and The larger value in the range.

[0116] Meanwhile, the upper limit of dynamic duration has a minimum constraint:

[0117] ;

[0118] in, This is the preset minimum defrosting time.

[0119] The effect of this calculation method is that the more severe the frost, the longer the upper limit of the dynamic duration, ensuring sufficient time for defrosting under severe frost conditions. Conversely, the greater the temperature deviation, the shorter the upper limit of the dynamic duration, limiting the further adverse effects of defrosting on the material temperature when it has already deviated significantly. The superposition of these two adjustment terms allows the upper limit of the dynamic duration to automatically find a balance between sufficient defrosting and material temperature protection based on the current operating conditions. The preset frost severity adjustment coefficient physically represents the maximum extent to which the defrosting time needs to be extended as the frost characteristic value increases from zero to one. Since the frost characteristic value is a normalized dimensionless value, its range is between zero and one. Therefore, the preset frost severity adjustment coefficient represents the maximum extension of the defrosting time required for each increase in the frost characteristic value by one unit. When normalized to dimensionless units, the amount of time required to extend the defrosting time is defined as the total range from zero to one. This coefficient, with dimensions of time, was obtained through multi-condition experimental calibration during the system design phase. This value is stored in the parameter storage and calculation unit. The more severe the frost, the larger the frost characteristic value and the longer the upper limit of the dynamic duration, ensuring sufficient defrosting. The preset material temperature deviation adjustment coefficient is the amount of time required to shorten the defrosting time for every one degree Celsius increase in the positive material temperature deviation. This coefficient, with dimensions of time per degree Celsius, was obtained through multi-condition experimental calibration during the system design phase. This value is stored in the parameter storage and calculation unit. The larger the positive material temperature deviation, the shorter the upper limit of the dynamic duration, reducing the impact of defrosting on the material temperature.

[0120] The preset baseline defrosting time is determined during the system design phase based on the average time required for the evaporator to complete complete defrosting under typical frosting conditions. This value is stored in the parameter storage and calculation unit and can be corrected in step S5 based on historical operating data. The maximum value of the positive material temperature deviation between the two temperature zones is taken as the larger of the positive material temperature deviation of the first and second temperature zones in the steady-state quantities constructed in step S1. The positive material temperature deviation is used here instead of the absolute value of the material temperature deviation because the adjustment of the upper limit of the dynamic duration should only be applied when the material temperature is higher than the preset target temperature. The purpose of this pre-stabilization and cold storage strategy is to limit the further adverse effects of defrosting on the material temperature when the material temperature is already too high. When the material temperature is below or equal to the preset target temperature, the temperature deviation is negative or zero, indicating that the temperature zone is already in a cold storage state and has sufficient temperature buffer margin to withstand the temperature rise during defrosting. At this time, the defrosting time should not be shortened due to sufficient cold storage, otherwise it will contradict the purpose of the pre-stabilization and cold storage strategy, that is, the pre-stabilization stage deliberately lowers the material temperature to form a cold storage buffer. If the negative deviation caused by cold storage shortens the defrosting time, the effect of the cold storage buffer will be weakened and its full potential cannot be realized. The defrosting process plays a crucial role in maintaining stable material temperature. Therefore, the positive material temperature deviation when the estimated material temperature is less than or equal to the corresponding preset target temperature is set to zero. This ensures that the defrosting duration is only shortened when the material temperature is indeed higher than the preset target temperature, guaranteeing the consistency between the dynamic duration upper limit adjustment logic and the pre-stabilized temperature storage strategy. In an optional implementation, the maximum value of the positive material temperature deviation between the two temperature zones can also be replaced by a weighted sum of the positive material temperature deviations of the two temperature zones, with their respective preset temperature zone usage weights as coefficients. This weighted sum can comprehensively reflect the temperature of both temperature zones. The degree of positive deviation and its importance are different, providing a smoother adjustment effect when the positive material temperature deviations in both temperature zones are greater than zero and the difference is large; the upper limit of dynamic duration has a minimum lower limit, that is, the upper limit of dynamic duration shall not be lower than the preset minimum defrosting duration. When the upper limit of dynamic duration is less than the preset minimum defrosting duration, the upper limit of dynamic duration is set to the preset minimum defrosting duration. The preset minimum defrosting duration is determined by the system design stage based on the shortest time required for the evaporator to complete the minimum effective defrosting, so as to ensure the basic effectiveness of defrosting. This value is stored in the parameter storage and calculation unit.

[0121] During the defrosting process, the main controller continuously monitors the air temperature of the first temperature zone and the air temperature of the second temperature zone through the temperature and humidity acquisition unit, and continuously updates the estimated values ​​of the material temperature in the first temperature zone and the material temperature in the second temperature zone through the material temperature estimation model in step S1, and calculates the material temperature deviation in the first temperature zone and the material temperature deviation in the second temperature zone in real time.

[0122] The main controller sets defrost interruption conditions; these conditions include any one of the following three scenarios: The first scenario is when the defrost execution time reaches its upper limit, i.e., the defrost execution time is greater than or equal to the dynamic duration upper limit, indicating that the current defrost has reached the maximum allowable defrost time determined based on the current degree of frost formation and the temperature deviation of the material. Continuing defrost will adversely affect the stability of the material temperature. The second scenario is when the evaporator surface temperature reaches the termination temperature, i.e., the evaporator surface temperature is greater than or equal to the preset defrost termination temperature, indicating that the frost layer on the evaporator surface has fully melted. Continuing heating has no practical defrosting significance and will cause unnecessary energy consumption and temperature rise in the affected area. The preset defrost termination temperature is determined during the system design phase based on the temperature required for complete melting of the frost layer on the evaporator surface. It is typically a temperature value slightly above zero degrees Celsius to ensure sufficient melting of the frost layer. This value is stored in the parameter storage and calculation unit. The third scenario... In one scenario, the temperature rise increment reaches the allowable range. Specifically, the main controller records the estimated temperature value of the temperature zone with the highest pre-set usage weight at the start of defrosting as the defrosting baseline temperature. During defrosting, the difference between the current estimated temperature value of that zone and the defrosting baseline temperature is continuously calculated. This difference represents the temperature rise increment during defrosting relative to the initial defrosting temperature. If this temperature rise increment is greater than or equal to a pre-set defrosting interruption temperature rise threshold, the temperature rise increment is determined to be within the allowable range. The pre-set defrosting interruption temperature rise threshold is determined during the system design phase based on the maximum acceptable temperature rise during defrosting for the stored items in short-term access scenarios. Furthermore, the pre-set defrosting interruption temperature rise threshold is greater than a pre-set baseline pre-cooling compensation amount to ensure that the cold storage buffer formed during the pre-stabilization phase does not trigger an interruption immediately upon defrosting startup. This value is stored in the parameter storage and calculation unit.

[0123] When any of the defrosting interruption conditions are met, the main controller shuts down the defrosting execution unit, the defrosting action ends, and the process proceeds to step S4.

[0124] Step S4: After defrosting, calculate the recovery coefficient based on the steady state quantity, and adjust the cooling capacity distribution ratio and circulating fan speed according to the recovery coefficient of each temperature zone.

[0125] After the defrosting operation is completed, the main controller re-obtains the current estimated values ​​of the first and second temperature zones through the material temperature estimation model in step S1, and calculates the material temperature deviation of the first and second temperature zones after defrosting.

[0126] The main controller calculates the recovery coefficient for each temperature zone based on the temperature deviation, the preset application weights of each temperature zone, and the recovery slope requirements for each temperature zone. Because the evaporator stops cooling and the defrosting unit releases heat during defrosting, the air temperature in each zone rises, and the object temperature increases accordingly. Therefore, the temperature deviation in each temperature zone after defrosting is usually positive, meaning the object temperature is higher than the preset target temperature. In this case, cooling is needed to restore the object temperature to the preset target temperature. However, under certain operating conditions, if sufficient cold storage is achieved during the pre-stabilization stage and the defrosting time is short, the object temperature in some temperature zones may rise after defrosting. If the temperature is still below the preset target temperature, the temperature deviation is negative. For temperature zones with negative temperature deviations, the temperature of the material in that zone is already below the preset target temperature and does not need to be restored through cooling. The temperature of the material will gradually approach the preset target temperature as the air temperature in the zone naturally rises. Therefore, no additional cooling capacity should be allocated to this temperature zone. Based on the above analysis, when calculating the recovery coefficient, the main controller only calculates the effective recovery coefficient for temperature zones with positive temperature deviations. For temperature zones with temperature deviations less than or equal to zero, the recovery coefficient is directly set to zero, indicating that the temperature zone does not need to be restored through cooling.

[0127] Before calculating the recovery coefficient, the main controller first normalizes each component. For the temperature deviation after defrosting in each temperature zone, when the temperature deviation is greater than zero, normalization is performed based on the preset maximum reference value for temperature deviation. The temperature deviation is divided by the preset maximum reference value for temperature deviation, and the quotient is the normalized temperature deviation characteristic. If the quotient is greater than one, it is set to one. When the temperature deviation is less than or equal to zero, the normalized temperature deviation characteristic is set to zero. For the preset application weights of each temperature zone, since the sum of the application weights of the two temperature zones is one and each weight value is already between zero and one, no additional normalization is required. For the recovery slope requirement of each temperature zone, when the temperature deviation is greater than zero, it is set to the rate of temperature change required for the temperature zone to recover the temperature deviation to within the preset allowable bandwidth of the temperature deviation within the preset target recovery time. The calculation method is to... The recovery slope requirement for a given temperature zone is calculated by subtracting the preset allowable bandwidth from the temperature deviation and then dividing by the preset target recovery time. When the temperature deviation of the zone is less than or equal to the preset allowable bandwidth, the recovery slope requirement is zero, indicating that the temperature deviation is within the allowable range and recovery is unnecessary. The recovery slope requirement is normalized by dividing the preset maximum reference value of the recovery slope by the preset maximum reference value. The quotient is the normalized recovery slope characteristic; if the quotient is greater than one, it is set to one. The preset maximum reference value of the recovery slope is determined during the system design phase based on the maximum temperature recovery rate achievable by the compressor and fan under rated operating conditions and is stored in the parameter storage and calculation unit.

[0128] The calculation method for the recovery coefficient of each temperature zone is determined according to the direction of the material temperature deviation in that temperature zone. When the material temperature deviation of that temperature zone is greater than zero, the normalized material temperature deviation characteristic of that temperature zone is multiplied by a preset first recovery weight coefficient, plus the preset application weight of that temperature zone multiplied by a preset second recovery weight coefficient, plus the normalized recovery slope characteristic of that temperature zone multiplied by a preset third recovery weight coefficient. The sum of the results is the recovery coefficient of that temperature zone. When the material temperature deviation of that temperature zone is less than or equal to zero, the recovery coefficient of that temperature zone is set to zero, indicating that no refrigeration recovery is required for that temperature zone.

[0129] The reason for using the above-mentioned conditions to determine the recovery coefficient is that for temperature zones with a temperature deviation less than or equal to zero, the temperature of the material is already at or below the preset target temperature and does not need to be restored through refrigeration. If the temperature deviation direction is not distinguished and a uniform weighted sum is performed, the temperature zone usage weight, as a constant, will still result in a non-zero recovery coefficient for temperature zones with a temperature deviation less than or equal to zero, leading to unnecessary allocation of cooling capacity to these temperature zones, which contradicts the conclusion that no refrigeration recovery is needed. By directly determining the recovery coefficient to zero when the temperature deviation is less than or equal to zero, the consistency between the calculation result of the recovery coefficient and the logic of determining the temperature deviation direction is ensured. For temperature zones with a temperature deviation greater than zero, the reason for using a three-dimensional weighted sum to calculate the recovery coefficient is that the recovery priority of each temperature zone after defrosting needs to comprehensively consider three factors: the temperature deviation characteristic reflects the absolute degree of deviation of the current material temperature from the preset target temperature; the larger the deviation, the more urgent the temperature recovery need of the temperature zone, and the more urgent the allocation of cooling capacity should be; the temperature zone usage weight reflects the importance of the temperature zone in the user's usage scenario, and short-term storage temperature... Zones with higher recovery priority due to their direct impact on the user's immediate experience should be recovered first, even if their temperature deviation is the same as that of long-term storage zones. The recovery slope characteristic reflects the rate of temperature change required for a zone to recover its temperature within a specified time. A larger value indicates a more urgent recovery task, requiring more cooling support to complete recovery within the preset target recovery time. The effect of combining the three dimensions into a single recovery coefficient through weighted summation is that the main controller can directly compare the recovery priorities of two zones based on a single scalar value, without having to compare and judge multiple dimensions separately, simplifying the implementation of control logic. At the same time, the relative importance of the three dimensions can be flexibly adjusted by setting the weight coefficients to adapt to the needs of different application scenarios. Since each input characteristic is within the range of zero to one, and the sum of the preset first recovery weight coefficient, the preset second recovery weight coefficient, and the preset third recovery weight coefficient is one, the range of the recovery coefficient is greater than zero and less than or equal to one when the temperature deviation is greater than zero, and zero when the temperature deviation is less than or equal to zero.

[0130] The preset target recovery time is determined during the system design phase based on the user's expected waiting time for the temperature zone to recover to the normal temperature range after defrosting, and is comprehensively set in conjunction with the maximum cooling recovery capacity of the compressor and fan under rated operating conditions. This value is stored in the parameter storage and calculation unit. The preset allowable bandwidth for material temperature deviation is determined during the system design phase based on the acceptable temperature fluctuation range of the stored item near the target temperature. The same allowable bandwidth value is used for short-term access temperature zones and long-term storage temperature zones. This value is stored in the parameter storage and calculation unit. The preset first recovery weight coefficient, preset second recovery weight coefficient, and preset third recovery weight coefficient correspond to the material temperature deviation contribution, temperature zone usage contribution, and recovery slope contribution, respectively. Their values ​​are determined during the system design phase through comprehensive evaluation based on the degree of influence of the material temperature deviation, the importance of the temperature zone usage, and the urgency of recovery on the recovery priority, and are stored in the parameter storage and calculation unit. The above calculation methods are applicable to the first temperature zone and the second temperature zone, respectively.

[0131] The main controller compares the recovery coefficients of the first and second temperature zones to determine the temperature zone with higher recovery priority. The reason for using a differentiated recovery control strategy instead of equal recovery for both temperature zones is that after defrosting, the temperature deviation, the importance of the zone's purpose, and the urgency of recovery typically differ between the two zones. If cooling capacity and fan resources are allocated equally between the two zones, the zone with higher recovery demand may recover slowly due to insufficient cooling capacity, while the zone with lower recovery demand may over-cool due to excess cooling capacity, resulting in energy waste. By differentiating cooling capacity and adjusting fan speed based on the recovery coefficient, limited cooling resources can be prioritized for the temperature zone with the most urgent recovery demand, accelerating its temperature recovery, while appropriately reducing resource allocation to the zone with lower recovery demand, achieving an optimal balance between recovery efficiency and energy consumption overall. The main controller executes differentiated recovery control according to the following strategy.

[0132] For temperature zones with a high recovery coefficient, the main controller adjusts the opening of the electric proportional air valve through the air duct distribution execution unit to increase the cooling capacity distribution ratio of that temperature zone. Specifically, the main controller increases the cooling capacity distribution ratio of the temperature zone with a high recovery coefficient by a preset recovery stage cooling capacity distribution increment based on the current value, and correspondingly decreases the cooling capacity distribution ratio of the temperature zone with a low recovery coefficient by the same increment, so that the sum of the cooling capacity distribution ratios of the two temperature zones remains one. The preset recovery stage cooling capacity distribution increment is determined by the system design stage based on the proportion of additional cooling capacity required for accelerated temperature recovery in the priority temperature zone during the recovery stage, and is obtained through multi-condition experimental calibration. This value is stored in the parameter storage and calculation unit.

[0133] Based on the adjusted cooling capacity distribution ratio, the main controller adjusts the opening of the electric proportional damper by outputting corresponding analog control signals. Since the opening of the electric proportional damper is positively correlated with the cooling capacity distribution ratio of the first temperature zone, when the temperature zone with a larger coefficient of restitution is the first temperature zone, the main controller increases the opening of the electric proportional damper; when the temperature zone with a larger coefficient of restitution is the second temperature zone, the main controller decreases the opening of the electric proportional damper, thereby allowing the temperature zone with the larger coefficient of restitution to receive more cooling capacity. Simultaneously, the main controller increases the speed of the circulating fan corresponding to the temperature zone with the larger coefficient of restitution, specifically in the following manner: The main controller increases the rotational speed of the circulating fan corresponding to the temperature zone by a preset recovery phase fan speed increment based on the current value. The preset recovery phase fan speed increment is determined during the system design phase based on the fan speed increase required to accelerate air circulation within the temperature zone to improve heat exchange efficiency. It is obtained through multi-condition experimental calibration without exceeding the rated maximum speed of the circulating fan, and this value is stored in the parameter storage and calculation unit. The increase in the circulating fan speed accelerates the air flow speed within the temperature zone, enhances the convective heat transfer intensity between the cold air and the storage unit, thereby accelerating the temperature recovery of the temperature zone.

[0134] For temperature zones with a low recovery coefficient, the main controller maintains or appropriately reduces the cooling capacity allocation ratio and circulating fan speed in that zone. Specifically, since the cooling capacity allocation ratio for temperature zones with a high recovery coefficient has increased, the cooling capacity allocation ratio for temperature zones with a low recovery coefficient has decreased accordingly, and the main controller does not need to make additional adjustments to the opening of the electric proportional damper for that zone. For the circulating fan speed corresponding to that temperature zone, the main controller reduces it by a preset recovery phase fan speed reduction based on the current value. This preset recovery phase fan speed reduction is determined during the system design phase based on the requirement to moderately reduce fan power consumption while ensuring basic air circulation in that temperature zone, and is within a certain range. The value is obtained through multi-condition testing under the premise of the minimum stable operating speed of the circulating fan, and is stored in the parameter storage and calculation unit. When the recovery coefficient of the temperature zone with the smaller recovery coefficient is zero, that is, the temperature deviation of the material in the temperature zone is less than or equal to zero or the absolute value of the temperature deviation of the material in the temperature zone is less than or equal to the preset allowable bandwidth of the temperature deviation, the temperature zone does not need to be cooled for recovery, and the main controller maintains the current speed of the circulating fan in the temperature zone unchanged. When the recovery coefficients of both temperature zones are zero, that is, neither temperature zone needs to be cooled for recovery, the main controller maintains the current cooling capacity distribution ratio and the current speed of the circulating fans in the two temperature zones unchanged, and waits for the material temperature in each temperature zone to naturally approach the preset target temperature.

[0135] During the recovery phase, the main controller applies a slope limit to the frequency regulation of the variable frequency compressor, ensuring that the rate of change of the compressor frequency does not exceed the preset maximum frequency change slope. The reason for employing this slope limit strategy is that when the variable frequency compressor experiences rapid frequency changes, the motor speed and refrigerant flow need a transition process to reach a new steady state. If the frequency change rate is too fast, the mechanical stress and electrical shock inside the compressor increase. Long-term, frequent, and large-amplitude frequency adjustments will accelerate the wear of the compressor's mechanical components and shorten its service life. Simultaneously, rapid changes in the compressor frequency cause drastic fluctuations in the evaporator's cooling capacity, leading to oscillations in the air temperature of the temperature zone. These temperature oscillations are transmitted to the estimated material temperature through the material temperature estimation model, potentially causing frequent changes in the recovery coefficient and repeated adjustments to the cooling capacity distribution ratio, resulting in oscillations in the control system, which are detrimental to the temperature zone. Smooth temperature recovery: By applying a slope limit, the change in compressor frequency is constrained into a gradual process, protecting the mechanical and electrical safety of the compressor while avoiding drastic fluctuations in cooling capacity. This results in a smooth downward trend in the temperature zone during the recovery process, improving the stability and energy efficiency of the recovery process. The effect of this strategy is that it achieves improved compressor operational reliability and a smoother temperature recovery process at the cost of slightly extending the recovery time. For refrigeration equipment that requires long-term stable operation, this trade-off is reasonable and necessary. The preset maximum frequency change slope is determined during the system design phase based on the mechanical and electrical characteristics of the variable frequency compressor. The maximum allowable frequency change rate is selected under the premise of ensuring the stability and service life of the compressor, and this value is stored in the parameter storage and calculation unit.

[0136] The main controller continuously monitors the temperature deviation between the two temperature zones. When the absolute value of the temperature deviation in the first temperature zone and the absolute value of the temperature deviation in the second temperature zone are both less than or equal to the preset allowable bandwidth of temperature deviation, the recovery is determined to be complete, and the process proceeds to step S5.

[0137] Step S5: The main controller recalculates the current frost risk index and steady state quantity, and determines whether to exit the collaborative defrosting process based on the current frost risk index and steady state quantity.

[0138] After recovery, the main controller records the operation data of this collaborative defrosting process through the parameter storage and calculation unit, including the temperature difference between the inlet and outlet of the evaporator before defrosting, the temperature difference between the inlet and outlet of the evaporator after defrosting, the actual execution time of this defrosting, the actual time consumed in the recovery phase, the maximum temperature fluctuation range of the first temperature zone and the maximum temperature fluctuation range of the second temperature zone in the recovery phase, and the total energy consumption of this process.

[0139] The main controller evaluates the defrosting effect based on the recorded data; the defrosting effect evaluation includes the following criteria.

[0140] Criterion 1: If the actual recovery time exceeds a preset multiple of the target recovery time, the recovery time is deemed too long. The preset multiple is determined by the system design phase based on the maximum allowable timeout ratio of the recovery phase, and this value is stored in the parameter storage and calculation unit.

[0141] Criterion 2: If the maximum temperature fluctuation of any temperature zone exceeds the preset maximum allowable fluctuation range, the temperature fluctuation is deemed to be too large. The preset maximum allowable fluctuation range is determined by the system design stage based on the upper limit of the tolerance of the stored items to temperature fluctuations, and this value is stored in the parameter storage and calculation unit.

[0142] Criterion 3: The main controller determines the adequacy of defrosting. The specific determination method is divided into two scenarios based on the temperature difference between the evaporator inlet and outlet before defrosting: When the temperature difference between the evaporator inlet and outlet before defrosting is greater than the preset lower limit for temperature difference calculation, the ratio of the temperature difference between the evaporator inlet and outlet after defrosting to the temperature difference before defrosting is calculated. If this ratio is greater than the preset threshold for insufficient defrosting, then the defrosting is deemed insufficient, and the frost layer on the evaporator has not been effectively removed. When the temperature difference between the evaporator inlet and outlet before defrosting is less than or equal to the preset lower limit for temperature difference calculation, directly calculating the ratio would lead to distorted results or calculation anomalies due to an excessively small divisor, therefore, the ratio of the temperature difference between the evaporator inlet and outlet before defrosting to the temperature difference after defrosting is used. The temperature difference is used to determine the adequacy of defrosting. If the difference is less than the preset minimum effective temperature difference improvement value for defrosting, the defrosting is deemed insufficient. The preset lower limit for temperature difference calculation is determined during the system design phase based on the requirements for the measurement accuracy and ratio calculation stability of the evaporator inlet and outlet temperature difference, and this value is stored in the parameter storage and calculation unit. The preset minimum effective temperature difference improvement value for defrosting is determined during the system design phase based on the minimum absolute amount that the evaporator inlet and outlet temperature difference should improve after effective defrosting, and this value is stored in the parameter storage and calculation unit. The preset threshold for determining insufficient defrosting is determined during the system design phase based on the proportion by which the evaporator inlet and outlet temperature difference should return to normal levels after effective defrosting, and this value is stored in the parameter storage and calculation unit.

[0143] When either criterion one or criterion two is met, and criterion three is not met, the main controller executes the first type of parameter self-correction. The reason for adopting this parameter self-correction mechanism is that the preset parameters calibrated during the system design phase are based on limited experimental conditions and cannot fully cover all combinations of environmental conditions, loading states, and usage habits that users may encounter in actual use. Therefore, the defrosting effect may be unsatisfactory in actual operation. By making small, gradual corrections to key parameters based on the actual operating effect of each collaborative defrosting process, the system can gradually adapt to the actual usage scenarios of specific users. After multiple defrosting cycles, each parameter approaches the optimal value under that usage scenario, achieving adaptive optimization of the defrosting control strategy. The first type of parameter self-correction targets situations where defrosting itself is sufficient but the recovery process is unsatisfactory, i.e., the frost layer has been effectively removed but the recovery time is too long. Excessive temperature fluctuations or long defrost durations indicate insufficient pre-stabilization and cold storage, excessive defrost time, or unsuitable defrost timing. Therefore, the correction strategy aims to enhance the pre-stabilization and cold storage effect, shorten the defrost time, and improve the defrost window entry conditions. Specifically, the strategy involves increasing the preset pre-cooling compensation step size of the next pre-stabilization stage's baseline pre-cooling compensation amount based on the current value. This means updating the preset baseline pre-cooling compensation amount to the current preset baseline pre-cooling compensation amount plus the preset pre-cooling compensation step size. This enhances the pre-stabilization and cold storage effect. Increasing the pre-cooling compensation amount lowers the material temperature to a lower level before the next defrost, providing a greater buffer margin for temperature rise during defrost and reducing the possibility of the material temperature exceeding the acceptable range during defrost. Simultaneously, the preset baseline pre-cooling compensation amount must not exceed the preset upper limit.

[0144] The preset baseline defrost time for the next defrost cycle is reduced by a preset defrost time correction step size from the current value. This means the preset baseline defrost time is updated to the current preset baseline defrost time minus the preset defrost time correction step size. Shortening the defrost time reduces the impact on the object temperature. The effect of shortening the defrost time is to reduce the duration the evaporator stops cooling, thereby reducing the rise in air temperature and the fluctuation range of the object temperature. Simultaneously, the preset baseline defrost time must not be lower than the preset minimum defrost time. The preset window threshold is increased by a preset window threshold correction step size from the current value. This means the preset window threshold is updated to the current preset window threshold plus the preset window threshold correction step size. This improves the entry conditions for the defrost window, allowing defrosting to occur more frequently. Executing at a favorable time and increasing the window threshold aims to require the defrost index to reach a higher level before triggering defrost. This allows defrosting to be performed when electricity prices are lower, user activity is lower, or recovery is easier, thus improving the recovery effect after defrosting. At the same time, the preset window threshold must not exceed the preset upper limit of the window threshold. The aforementioned preset upper limit of the baseline precooling compensation amount and the preset upper limit of the window threshold are determined during the system design phase and stored in the parameter storage and calculation unit. The reason for setting the upper limit is to prevent the parameters from exceeding the reasonable range after multiple unidirectional corrections. For example, excessive precooling compensation amount will lead to overcooling during the pre-stabilization stage, causing unnecessary energy waste. An excessively high window threshold will cause the system to be unable to find a defrost window that meets the conditions for a long time, thus delaying defrosting.

[0145] When criterion three is met, regardless of whether criterions one and two are met, the main controller executes the second type of parameter self-correction. This second type of parameter self-correction addresses insufficient defrosting, meaning the frost layer on the evaporator has not been effectively removed. This indicates that the defrosting time is insufficient to fully melt the frost, therefore the correction strategy is to extend the defrosting time. The reason for prioritizing the second type of parameter self-correction over the first type is that insufficient defrosting means the evaporator's heat exchange capacity has not been effectively restored. Residual frost will continue to accumulate and worsen during subsequent operation. If the insufficient defrosting time is not corrected in time, the evaporator's cooling efficiency will continue to decline, potentially leading to the temperature zone failing to maintain within the preset target temperature range, which could damage stored items. Quality issues can cause irreversible damage, so even if extending the defrosting time may increase recovery time or temperature fluctuations, ensuring adequate defrosting must be prioritized. The specific correction strategy is to increase the preset baseline defrosting time for the next defrost cycle by a preset defrosting time correction step, i.e., updating the preset baseline defrosting time to the current preset baseline defrosting time plus the preset defrosting time correction step. This extends the defrosting time to ensure adequate defrosting, while the preset baseline defrosting time must not exceed a preset upper limit. This preset upper limit is determined during the system design phase based on the longest reasonable time required for the evaporator to complete defrosting under the most severe frosting conditions, and this value is stored in the parameter storage and calculation unit.

[0146] Simultaneously, the main controller corrects the frost risk weight coefficients in step S1 based on the operational data of this collaborative defrosting process. The reason for online correction of the frost risk weight coefficients is that the initial values ​​of each weight coefficient in step S1 were obtained through multiple regression analysis based on limited experimental conditions during the system design phase. In actual operation, differences in user habits, installation environment, and storage item loading methods may lead to deviations between the actual contribution of each influencing factor to frost risk and the initial calibration values. By making small, gradual corrections to the weight coefficients based on the actual defrosting effect feedback, the frost risk assessment model can gradually adapt to the actual operating conditions of specific users, improving the accuracy of frost risk judgment and reducing unnecessary defrosting due to overestimation of frost risk or defrosting delays due to underestimation of frost risk. The frost risk weight coefficients include preset first weight coefficients, preset third weight coefficients, preset fourth weight coefficients, and preset fifth weight coefficients. The specific correction method is as follows: the main controller… The controller compares the temperature difference between the evaporator inlet and outlet before and after defrosting. This difference reflects the actual amount of frost removed during the defrosting process. If this difference is less than the preset effective defrosting temperature difference improvement threshold, it indicates that the actual degree of frost on the evaporator was relatively light when defrosting was triggered, and the frost risk index tends to be overestimated. In this case, the correction direction is to increase the weight of the evaporator temperature difference factor and decrease the weight of the door opening frequency, door opening duration, and compressor running time factors. The reason is that the evaporator inlet and outlet temperature difference is the parameter that most directly reflects the actual degree of frost. Increasing its weight can make the frost risk index rely more on direct evidence of actual frost rather than indirect influencing factors, thereby reducing the tendency to overestimate the frost risk. The main controller increases the preset weight correction step size of the preset first weight coefficient based on the current value, and decreases the preset third, fourth, and fifth weight coefficients according to the preset allocation ratio. After correction, the five weight coefficients are re-normalized so that the sum of the five weight coefficients is one.

[0147] If the difference is greater than or equal to the preset effective defrost temperature difference improvement threshold, the current frost risk weight coefficient remains unchanged. The preset effective defrost temperature difference improvement threshold and the preset weight correction step size are obtained through multi-condition experiment calibration during the system design phase and stored in the parameter storage and calculation unit. The value of the above weight correction step size should be small enough to ensure that the adjustment of the weight coefficient is gradual. The reason for using small step size gradual correction is that the operation data of a single defrost cycle may be affected by accidental factors and is not universally representative. If the single correction range is too large, it may cause the weight coefficient to shift drastically due to individual abnormal operating conditions, which will reduce the accuracy of frost risk assessment. Small step size correction can gradually accumulate the correction effect in multiple defrost cycles, so that the adjustment direction of the weight coefficient is determined by the statistical trend of multiple operation data, which has better robustness.

[0148] The preset precooling compensation step size is determined during the system design phase based on the expected improvement of the pre-stabilized temperature and cold storage effect of a single correction. A value that is too large will lead to excessive cooling during the pre-stabilized temperature stage, resulting in energy waste; a value that is too small will result in an insignificant correction effect. This value is obtained through multi-condition experimental calibration and stored in the parameter storage and calculation unit. The preset defrost duration correction step size is determined during the system design phase based on the expected adjustment of the defrost duration of a single correction. A value that is too large will lead to drastic changes in defrost duration, affecting system stability; a value that is too small will result in an insignificant correction effect. This value is obtained through multi-condition experimental calibration and stored in the parameter storage and calculation unit. The preset window threshold correction step size is determined during the system design phase based on the expected improvement of the defrost window admission conditions of a single correction. This value is obtained through multi-condition experimental calibration and stored in the parameter storage and calculation unit.

[0149] When criteria one, criteria two, and criteria three are all invalid, the main controller maintains the current parameters unchanged.

[0150] In an optional implementation, the defrosting effect evaluation can also include a fourth criterion as a supplementary judgment condition. The fourth criterion is that if the total energy consumption of the current collaborative defrosting process exceeds the preset upper limit of energy consumption for a single defrosting process, then the energy efficiency of this defrosting process is deemed poor. The preset upper limit of energy consumption for a single defrosting process is determined during the system design phase by multiplying the average total energy consumption of a typical defrosting process under normal operating conditions by a preset energy consumption exceedance multiple. This value is stored in the parameter storage and calculation unit. When the fourth criterion is met and the third criterion is not met, the main controller executes a third type of parameter self-correction. This third type of parameter self-correction addresses the situation where defrosting is sufficient but the overall process energy consumption is too high, indicating that the compressor operating frequency or duration is too long during the pre-stabilization or recovery phases. Therefore, the correction strategy is to appropriately reduce the cold storage depth during the pre-stabilization phase to shorten the pre-stabilization time. Specific corrections are as follows: The strategy involves reducing the preset baseline precooling compensation amount by a preset correction step size based on the current value. Simultaneously, the preset baseline precooling compensation amount must not be lower than a preset lower limit. This preset lower limit is determined during the system design phase based on the minimum cold storage depth required to ensure the material temperature does not exceed the acceptable range during defrosting. This value is stored in the parameter storage and calculation unit. The reason for using energy consumption criteria as a supplementary evaluation condition is that criteria one and two only evaluate the defrosting effect from the perspectives of recovery time and material temperature fluctuation, without considering energy consumption. Under certain operating conditions, both recovery time and material temperature fluctuation are within acceptable ranges, but the total energy consumption is significantly high. In this case, by appropriately reducing the precooling compensation amount to shorten the high-frequency operation time of the pre-stabilization stage, the overall process energy consumption can be reduced without significantly affecting the material temperature stability.

[0151] The corrected preset baseline precooling compensation amount, preset baseline defrosting time, preset window threshold, and each frost risk weight coefficient are stored in the parameter storage and calculation unit for use in the next collaborative defrosting process.

[0152] After the parameters are self-corrected, the main controller recalculates the current frost risk index and the temperature deviation between the two temperature zones.

[0153] The main controller determines the exit condition of the process. When the frost risk index drops below the recovery threshold (i.e., the frost risk index is less than the recovery threshold), and the absolute values ​​of the temperature deviations in the first and second temperature zones are both less than or equal to the preset allowable bandwidth for temperature deviations, the main controller exits the collaborative defrosting process and resumes the normal time-sharing variable frequency energy-saving control mode. The recovery threshold is less than the preset risk threshold in step S1 to form a hysteresis characteristic. The reason for using the hysteresis characteristic design is that if the entry and exit thresholds of the collaborative defrosting process are the same, when the frost risk index fluctuates slightly around this threshold, the system will frequently switch between the collaborative defrosting process and the normal operating mode. Each switch involves operations such as compressor frequency adjustment, damper opening adjustment, and control mode conversion. Frequent switching not only increases the computational burden of the control system but also causes frequent actions of the compressor and dampers, accelerating mechanical... Wear and tear and unnecessary energy consumption are generated. By setting the exit threshold to a recovery threshold lower than the entry threshold, an insensitive interval is formed between the entry threshold and the recovery threshold. The frost risk index must drop below the recovery threshold to exit the collaborative defrosting process, and after exiting, it must rise above the preset risk threshold to re-enter. This effectively avoids frequent switching of the system near the threshold and improves the operational stability of the control system. The recovery threshold is obtained by multiplying the preset risk threshold by a preset hysteresis coefficient during the system design phase. The preset hysteresis coefficient has a value range of greater than zero and less than one. Its value is determined by the system design phase based on the stability requirements of the system's state switching near the frost risk threshold. The smaller the hysteresis coefficient, the larger the interval between the recovery threshold and the preset risk threshold, and the stronger the resistance to frequent switching. However, the conditions for exiting the collaborative defrosting process are also more stringent. This value is stored in the parameter storage and calculation unit.

[0154] In the conventional time-sharing variable frequency energy-saving control mode, the main controller adjusts the operating frequency of the variable frequency compressor according to the preset electricity price level corresponding to the current time period, setting the operating frequency of the variable frequency compressor to the corresponding preset high frequency or preset low frequency. The preset high frequency corresponds to low electricity price periods, and its purpose is to fully utilize the low electricity price window, allowing the compressor to operate at a frequency higher than the normal cooling demand, quickly and excessively storing cold for the storage unit. The preset high frequency is determined during the system design phase based on the compressor's performance curve, the maximum cooling capacity of the refrigeration system, and the duration of typical low electricity price periods. It should ensure that effective cold storage can be completed within this period without exceeding the compressor's rated maximum frequency, while avoiding excessively high frequencies that could lead to... The system's energy efficiency ratio drops significantly or abnormal noise occurs; the specific values ​​are stored in the parameter storage and calculation unit. The preset low frequency corresponds to periods of high electricity prices. Its purpose is to limit energy consumption, allowing the compressor to maintain operation at a lower frequency or operate intermittently. It prioritizes the use of the cooling capacity stored in the storage unit during previous periods to smooth out the temperature rise in the temperature zone. The preset low frequency is determined during the system design phase based on the minimum cooling capacity required to maintain the temperature zone within an acceptable fluctuation range and the stable operating characteristics of the compressor at low frequencies. It should not be lower than the minimum stable operating frequency specified by the compressor manufacturer to ensure the reliability of system operation and avoid additional energy loss and mechanical shock caused by frequent start-stop. Its specific values ​​are stored in the parameter storage and calculation unit.

[0155] The reason for adopting the time-sharing variable frequency control strategy is that the temperature control of stored items in refrigeration equipment is an application scenario with relatively relaxed requirements for temperature response timeliness. The large thermal inertia of the storage unit means that the temperature zone temperature will not rise rapidly during the compressor's reduced frequency operation. This characteristic provides conditions for optimizing energy consumption by utilizing time-sharing electricity price differences. During periods of low electricity price, the compressor runs at a higher frequency to reduce the temperature zone temperature to a level slightly below the preset target temperature, which is equivalent to pre-storing cold energy in the storage unit. During subsequent periods of high electricity price, the compressor's operating frequency is reduced or even temporarily stopped, using the cold energy stored in the storage unit to maintain the temperature zone temperature within an acceptable range. This transfers some of the electricity consumption during periods of high electricity price to periods of low electricity price, reducing the total electricity cost while ensuring temperature control effectiveness. At the same time, the main controller continuously monitors the humidity inside the cabinet and door opening behavior through the temperature and humidity acquisition unit and the door opening detection unit, and periodically calculates the frost risk index. When the frost risk index is greater than or equal to the preset risk threshold again, it re-enters step S1 and starts the collaborative defrosting process.

[0156] Example 2:

[0157] See Figure 3 As shown, a time-sharing variable frequency collaborative defrosting energy-saving control system for refrigeration equipment is provided, used to execute the aforementioned time-sharing variable frequency collaborative defrosting energy-saving control method for refrigeration equipment. The system includes:

[0158] The material temperature status module 101 is used to collect operating parameters, normalize the operating parameters and then sum them by weight to obtain the frost risk index. When the frost risk index is greater than or equal to the preset risk threshold, the collaborative defrosting process is activated. Based on the material temperature estimation model, the material temperature estimates of the first and second temperature zones are estimated and a steady state quantity is constructed.

[0159] The defrosting determination module 102 is used to calculate the defrosting index based on the steady state quantity, compare the defrosting index with the preset window threshold, and determine whether to defrost immediately or delay defrosting.

[0160] The defrosting start module 103 is used to start defrosting after reducing the estimated temperature of each temperature zone to the pre-stabilized temperature target when it is determined to defrost immediately or exit delayed defrosting. It sets a dynamic time limit based on the operating parameters and stable state quantities, continuously monitors the estimated temperature of the material during the defrosting process, and determines the defrosting interruption condition according to the dynamic time limit. When the defrosting interruption condition is triggered, the defrosting ends.

[0161] The defrost recovery module 104 is used to calculate the recovery coefficient based on the steady state quantity after defrosting, and adjust the cooling capacity distribution ratio and the circulating fan speed according to the recovery coefficient of each temperature zone.

[0162] The defrost exit module 105 is used by the main controller to recalculate the current frost risk index and steady state quantity, and determine whether to exit the collaborative defrost process based on the current frost risk index and steady state quantity.

[0163] The embodiments of this application have been described above, but these embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments based on the guidance of these embodiments, and all of them are within the protection scope of these embodiments.

Claims

1. A time-sharing variable frequency collaborative defrosting energy-saving control method for refrigeration equipment, wherein the refrigeration equipment includes a first temperature zone, a second temperature zone, a circulating fan, and a main controller, characterized in that, Includes the following steps: The main controller collects operating parameters, normalizes the operating parameters, and then calculates a weighted sum to obtain a frosting risk index. When the frosting risk index is greater than or equal to a preset risk threshold, the collaborative defrosting process is activated. Based on the material temperature estimation model, the estimated material temperature values ​​of the first and second temperature zones are estimated, and a steady-state quantity is constructed. The frosting risk index is calculated by multiplying the normalized evaporator inlet and outlet temperature difference characteristic by a preset first weighting coefficient, adding the normalized chamber humidity characteristic by a preset second weighting coefficient, adding the normalized door opening frequency characteristic by a preset third weighting coefficient, adding the normalized door opening duration characteristic by a preset fourth weighting coefficient, and adding the normalized compressor running time characteristic by a preset fifth weighting coefficient. The sum of these results is the frosting risk index. Methods for obtaining estimated material temperature include: Based on the current loading rate provided by the loading status detection unit, the thermal response coefficient is obtained by looking up the pre-stored table of correspondence between thermal response coefficient and loading rate. When the current load rate is between two adjacent calibrated load rates, the corresponding thermal response coefficient is obtained by linear interpolation. The material temperature estimation model calculates the estimated material temperature for each temperature zone based on the thermal response coefficient; methods for constructing steady-state quantities include: Calculate the material temperature deviation for each temperature zone, specifically by subtracting the preset target temperature of the temperature zone from the estimated material temperature of that zone. The main controller assigns preset temperature zone weights according to the intended use of each temperature zone; The steady-state quantity is constructed by using the temperature deviation of each temperature zone and the preset application weight of each temperature zone as constraints. The defrost index is calculated based on steady-state variables. The defrost index is then compared with a preset window threshold to determine whether immediate or delayed defrosting is necessary. Methods for calculating the defrost index include: The defrosting economic weight for the current period is determined based on the preset electricity price level corresponding to the current period. The predicted value of user door opening activity within the future preset prediction time window is determined by the arithmetic mean of the door opening frequency data of the same historical period. The recovery difficulty index after defrosting is determined based on the temperature deviation of each temperature zone in the steady state quantity and the ambient temperature outside the refrigeration equipment. The defrost index is obtained by weighting and summing the defrost economic weight, the first reverse activity value, and the second reverse recovery difficulty value; where the first reverse activity value is one minus the predicted user door opening activity value, and the second reverse recovery difficulty value is one minus the recovery difficulty index after defrosting. When it is determined to defrost immediately or to exit delayed defrost, the estimated temperature of each temperature zone is reduced to the pre-stabilized temperature target and then defrost is started. The upper limit of dynamic duration is set based on the operating parameters and stable state quantities. During the defrost process, the estimated temperature is continuously monitored and the defrost interruption condition is determined according to the upper limit of dynamic duration. When the defrost interruption condition is triggered, the defrost ends. After defrosting, the recovery coefficient is calculated based on the steady-state quantities, and the cooling capacity distribution ratio and circulating fan speed are adjusted according to the recovery coefficient of each temperature zone. The main controller recalculates the current frost risk index and steady-state quantity, and determines whether to exit the collaborative defrosting process based on the current frost risk index and steady-state quantity.

2. The energy-saving control method for time-sharing variable frequency coordinated defrosting of refrigeration equipment according to claim 1, characterized in that, Methods for performing delayed defrosting include: When the defrosting index is less than the preset window threshold, the delayed defrosting stage is entered, limiting the operating frequency of the variable frequency compressor to a preset restricted variable frequency range; The target cooling capacity distribution ratio for delayed defrosting is calculated based on the temperature deviation of each of the two temperature zones and the preset temperature zone usage weights. The opening of the electric proportional damper in the refrigeration equipment is then adjusted according to the target cooling capacity distribution ratio. During the delayed defrosting phase, the main controller continuously and periodically calculates the defrosting index until the defrosting index is greater than or equal to a preset window threshold, at which point it exits the delayed defrosting phase.

3. The energy-saving control method for time-sharing variable frequency coordinated defrosting of refrigeration equipment according to claim 1, characterized in that, Methods for setting a dynamic duration limit include: Divide the evaporator inlet and outlet temperature difference in the current operating parameters by the preset maximum reference value of the evaporator inlet and outlet temperature difference and perform amplitude limiting to obtain the frosting characteristic quantity. Based on the preset baseline defrosting time, the product of the preset frost degree adjustment coefficient and the frost characteristic quantity is added, and then the product of the maximum value of the positive material temperature deviation between the two temperature zones and the preset material temperature deviation adjustment coefficient is subtracted to obtain the upper limit of the dynamic time; wherein, the positive material temperature deviation is the difference between the estimated material temperature value and the corresponding preset target temperature. When the estimated material temperature value is less than or equal to the corresponding preset target temperature, the positive material temperature deviation is zero.

4. The energy-saving control method for time-sharing variable frequency coordinated defrosting of refrigeration equipment according to claim 3, characterized in that, Methods for determining defrosting interruption conditions include: The calculation of the temperature rise increment includes: the main controller records the estimated temperature of the temperature zone with a larger application weight at the time of defrosting start as the defrosting start temperature reference value; during the defrosting process, the difference between the current estimated temperature of the temperature zone and the defrosting start temperature reference value is continuously calculated to obtain the temperature rise increment. Defrosting interruption conditions include defrosting execution time being greater than or equal to the dynamic duration limit, evaporator surface temperature being greater than or equal to the preset defrosting termination temperature, or the temperature rise increment being greater than or equal to the preset defrosting interruption temperature rise threshold. The defrost interruption condition is triggered when any one of the defrost interruption conditions is met.

5. The energy-saving control method for time-sharing variable frequency coordinated defrosting of refrigeration equipment according to claim 1, characterized in that, Methods for obtaining the coefficient of recovery include: When the temperature deviation is greater than zero, the temperature deviation of each temperature zone after defrosting is normalized and limited based on the preset maximum reference value of the temperature deviation to obtain the normalized temperature deviation characteristic quantity; when the temperature deviation is less than or equal to zero, the normalized temperature deviation characteristic quantity is zero. The recovery slope requirement is calculated based on the temperature deviation of each temperature zone. The recovery slope requirement of each temperature zone is normalized and limited based on the preset maximum reference value of the recovery slope to obtain the normalized recovery slope characteristic quantity. When the temperature deviation of the material in the temperature zone is greater than zero, the normalized temperature deviation characteristic, the application weight of the temperature zone, and the normalized recovery slope characteristic are weighted and summed to obtain the recovery coefficient of the temperature zone; when the temperature deviation of the material in the temperature zone is less than or equal to zero, the recovery coefficient of the temperature zone is determined to be zero.

6. The energy-saving control method for time-sharing variable frequency coordinated defrosting of refrigeration equipment according to claim 1, characterized in that, Methods for determining whether to exit the collaborative defrosting process include: Set a preset recovery threshold, which is a preset risk threshold multiplied by a preset hysteresis coefficient; When the frost risk index is less than the preset recovery threshold, and the absolute value of the temperature deviation in each temperature zone is less than or equal to the preset allowable bandwidth of the temperature deviation, the main controller exits the collaborative defrosting process and resumes the conventional time-sharing variable frequency energy-saving control mode. The conventional time-sharing variable frequency energy-saving control mode adjusts the operating frequency of the variable frequency compressor according to the preset electricity price level corresponding to the current time period.

7. A time-sharing frequency conversion coordinated defrosting energy-saving control system for refrigeration equipment, characterized in that, A system for performing a time-sharing variable frequency coordinated defrosting energy-saving control method for refrigeration equipment as described in any one of claims 1-6; the system includes: The material temperature status module is used to collect operating parameters, normalize the operating parameters and then perform a weighted summation to obtain the frost risk index. When the frost risk index is greater than or equal to the preset risk threshold, the collaborative defrosting process is activated. Based on the material temperature estimation model, the material temperature estimates of the first and second temperature zones are estimated and a steady state quantity is constructed. The defrost determination module is used to calculate the defrost index based on the steady state quantity, compare the defrost index with the preset window threshold, and determine whether to defrost immediately or delay defrost. The defrost start module is used to start defrost after reducing the estimated temperature of each temperature zone to the pre-stabilized temperature target when it is determined that it is to defrost immediately or to exit delayed defrost. The module sets the upper limit of dynamic duration based on the operating parameters and stable state quantities. During the defrost process, the estimated temperature of the material is continuously monitored and the defrost interruption condition is determined according to the upper limit of dynamic duration. When the defrost interruption condition is triggered, the defrost ends. The defrost recovery module is used to calculate the recovery coefficient based on the steady state quantity after defrosting, and adjust the cooling capacity distribution ratio and the circulating fan speed according to the recovery coefficient of each temperature zone. The defrost exit module is used by the main controller to recalculate the current frost risk index and steady-state quantity, and determine whether to exit the collaborative defrost process based on the current frost risk index and steady-state quantity.

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