Intelligent control system for cold storage based on variable frequency multi-split unit

Abstract

This invention relates to the field of cold storage control technology, and more particularly to an intelligent control system for cold storage based on a variable frequency multi-split air conditioning unit (VFD), comprising a cold storage data acquisition module, a temperature zone analysis module, an identification module, a main unit control module, and a control compensation module. It collects operational data, calculates correlation coefficients for three cold storage states, predicts refrigeration and defrosting demands, and identifies refrigeration-defrosting conflicts, defrosting recovery conflicts, and combined conflicts. For different conflict types, it matches corresponding collaborative scheduling strategies, adjusting the defrosting execution queue to adjust the defrosting sequence, reducing the cold load impact during the recovery phase by adjusting the pre-cooling temperature reduction, and preventing overlapping interference from multiple air coolers by limiting the number of simultaneous defrosting operations and alternating defrosting in adjacent temperature zones. This invention achieves global collaborative scheduling of refrigeration and defrosting, improving system operating efficiency while ensuring stable temperature zones.

Description

Technical Field

[0001] This invention relates to the field of cold storage control technology, and in particular to an intelligent control system for cold storage based on a variable frequency multi-split host. Background Technology

[0002] In existing multi-split cold storage systems, refrigeration control and defrosting control are typically executed by separate logic, lacking an effective coordination mechanism. In actual operation, the defrosting action of the air coolers is often triggered according to a preset fixed cycle or simple threshold, without considering the real-time refrigeration demand of each temperature zone. This can easily lead to situations where a high-priority temperature zone urgently needs cooling, but the system is using the compressor's heating capacity for defrosting, resulting in insufficient cooling and excessive temperature in that zone. Furthermore, existing systems lack proactive management of the recovery phase after defrosting. After defrosting, the temperature zone often needs a rapid replenishment of large amounts of cooling capacity to restore to the target temperature. If multiple temperature zones finish defrosting successively at the same time, the concentrated surge in cooling demand can easily cause a short-term overload impact on the compressor, leading to temperature fluctuations throughout the entire cold storage facility and affecting the storage safety of each zone. Furthermore, existing systems generally do not employ differentiated compensation control for defrosting and non-defrosting temperature zones before and after defrosting. The heat load introduced during defrosting is directly transferred to the storage room, and there is a lack of smooth cooling recovery transition after defrosting. This results in significant temperature drift throughout the defrosting process, posing a considerable risk to goods with strict storage quality requirements. Summary of the Invention

[0003] To address this issue, the present invention provides an intelligent control system for cold storage based on a variable frequency multi-split host, which overcomes the problem in the prior art where the refrigeration and defrosting needs of cold storage are executed independently without prior coordination, resulting in mutual interference between defrosting and refrigeration peaks, leading to temperature fluctuations and high energy consumption.

[0004] To achieve the above objectives, the present invention provides an intelligent control system for cold storage based on a variable frequency multi-split compressor, comprising a multi-split variable frequency compressor, several indoor units and corresponding air coolers and defrosting valve assemblies, and further comprising: The cold storage data acquisition module is used to collect operating data of each temperature zone in the cold storage and the outdoor temperature, and to determine the operating parameters of the air cooler in each temperature zone; The operating data includes temperature setpoint, return air temperature, outlet air temperature, and refrigerant flow rate. The operating parameters of the air cooler include the refrigerant temperature difference between the evaporator inlet and outlet and the air pressure difference between the inlet and outlet. The temperature zone analysis module is used to determine the corresponding temperature zone thermal inertia coefficient based on the operating data of each temperature zone and the outdoor temperature, determine the defrosting urgency index and defrosting thermal shock coefficient based on the operating parameters of each air cooler, predict the cooling demand of the corresponding temperature zone based on the return air temperature, outlet air temperature and outdoor temperature of each temperature zone, and predict the defrosting demand of the corresponding air cooler during the control period based on the defrosting urgency index of each temperature zone. The identification module is used to determine the energy conflict of the corresponding temperature zone based on the cooling demand and defrosting demand. The energy conflict includes cooling-defrosting conflict, defrosting recovery conflict and compound conflict. In response to the existence of energy conflicts, the host control module determines a collaborative scheduling strategy based on the type of energy conflict, including: determining a defrosting execution queue according to the defrosting urgency index and thermal inertia coefficient of each temperature zone; determining the pre-cooling and temperature reduction range of each temperature zone in the queue before defrosting according to the defrosting thermal shock coefficient; and determining the number of air coolers that can perform defrosting simultaneously according to the heating capacity of the multi-split inverter compressor and alternating defrosting of adjacent temperature zones.

[0005] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-split host, the temperature zone analysis module is configured to determine the temperature change rate under the current operating state based on the return air temperature and the outlet air temperature of each temperature zone, and to determine the temperature zone thermal inertia coefficient of the temperature zone in combination with the refrigerant flow rate of the temperature zone. Furthermore, the defrosting urgency index of the air cooler is determined based on the temperature difference between the inlet and outlet refrigerant of the evaporator and the pressure difference between the inlet and outlet air pressure of the air cooler; the corresponding defrosting thermal shock coefficient is calculated based on the temperature zone thermal inertia coefficient of each temperature zone and the corresponding air pressure difference between the inlet and outlet air pressure of the air cooler.

[0006] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-split host, the temperature zone analysis module is also configured to predict the cooling demand of the corresponding temperature zone during the control period based on the temperature change rate and the outdoor temperature. Furthermore, based on the changing trend of the defrosting urgency index of each air cooler, the defrosting demand of the corresponding air cooler during the control period is predicted.

[0007] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-split host, the identification module is configured within the control period to determine the period when the cooling demand value of each temperature zone exceeds the basic cooling capacity as the peak cooling demand period of that temperature zone, the period when the defrosting urgency index of each air cooler reaches the defrosting trigger threshold as the defrosting demand period, and the period immediately following the defrosting demand period as the defrosting recovery period.

[0008] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-split air conditioning unit, the identification module is further configured to determine the energy conflict of the corresponding temperature zone based on the refrigeration demand and defrosting demand, including: If the identification result shows that the defrosting demand period overlaps with the peak cooling demand period of any temperature zone, it is determined that there is a cooling defrosting conflict. If the defrost recovery period overlaps with the peak cooling demand period of any temperature zone, then the defrost recovery period is determined to be conflicting. In response to the identification results of no time period overlap, it is determined that there is no energy conflict.

[0009] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-split host, the identification module is further configured to determine the energy conflict during the period when refrigeration defrosting conflict and defrosting recovery conflict coexist, as a composite conflict.

[0010] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-unit host, the host control module determines a corresponding cooperative scheduling strategy in response to the type of energy conflict, wherein: In response to the aforementioned cooling and defrosting conflict, the determined collaborative scheduling strategy is to determine the defrosting execution queue based on the defrosting urgency index of each temperature zone and the thermal inertia coefficient of the temperature zone. In response to the defrost recovery conflict or the combined conflict, the determined collaborative scheduling strategy includes: The defrosting execution queue is determined based on the defrosting urgency index of each temperature zone and the thermal inertia coefficient of each temperature zone. The pre-cooling and temperature reduction range before defrosting in each temperature zone in the queue is determined based on the defrosting thermal shock coefficient. The number of air coolers that perform defrosting simultaneously is determined and alternating defrosting is adopted in adjacent temperature zones. In the aforementioned compound conflict, the air cooler awaiting defrosting has a high priority in the defrosting execution queue.

[0011] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-split host, the host control module responds to any of the energy conflict determination results, obtains the defrosting urgency index of the air cooler to be defrosted and the temperature zone thermal inertia coefficient of its temperature zone, sorts the defrosting urgency indices from high to low, and sorts the air coolers in the same preset urgency interval of the defrosting urgency index from large to small according to the temperature zone thermal inertia coefficient. The sorting result is used as the defrosting execution queue.

[0012] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-unit host, the pre-cooling temperature reduction range determined by the host control module is positively correlated with the defrosting thermal shock coefficient.

[0013] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-unit host, the host control module obtains the current available heating capacity limit of the multi-unit variable frequency compressor, determines the upper limit of the number of air coolers that can be defrosted simultaneously based on the amount of heat required for defrosting a single air cooler, and selects air coolers not exceeding the upper limit in the defrosting execution queue as the same batch of defrosting targets. Among the items to be defrosted in the same batch, there are no air coolers belonging to adjacent temperature zones.

[0014] As a preferred technical solution for a cold storage intelligent control system based on a variable frequency multi-split compressor, the control compensation module is configured to, in response to the defrosting process, adjust the speed of the multi-split variable frequency compressor according to the difference between the return air temperature of the non-defrosting temperature zone and the set value, and increase the opening of the electronic expansion valve of the corresponding indoor unit according to the difference between the refrigerant flow rate of the non-defrosting temperature zone and the basic flow rate required to maintain the set value. In addition, in response to the completion of defrosting, the upper limit of the temperature recovery rate is determined according to the defrosting thermal shock coefficient of the defrosting temperature zone, and the opening of the electronic expansion valve of the corresponding indoor unit is controlled until the deviation between the return air temperature of the temperature zone and the set value is reduced to the preset range.

[0015] Compared with existing technologies, the advantages of this invention are as follows: The cold storage data acquisition module comprehensively collects operating parameters of each temperature zone and outdoor environmental parameters, obtaining the operating parameters of the air cooler, providing reliable data support for the entire system control process; the temperature zone analysis module quantitatively calculates the thermal inertia coefficient, defrosting urgency index, and defrosting thermal shock coefficient of each temperature zone based on thermodynamic laws, and accurately predicts the cooling demand of each temperature zone and the defrosting demand of the air cooler during the control period, achieving proactive prediction and quantitative analysis of the system's operating status; the identification module accurately identifies conflict types, clearly defines the conflict type, the involved temperature zone, and the time of occurrence, providing clear decision-making basis; and the main control module... Differentiated collaborative scheduling strategies are matched to different types of energy conflicts. The defrosting execution queue, the pre-cooling reduction range before defrosting, and the number of simultaneous defrosting air coolers are reasonably determined, and adjacent temperature zones are defrosted alternately. This achieves overall coordination between defrosting operations and the cooling demand of multiple temperature zones, effectively balancing the cooling supply between defrosting and non-defrosting temperature zones. It can fundamentally avoid the problem of system overload and drastic temperature fluctuations caused by the superposition of defrosting and cooling demands. It significantly improves the operational stability, temperature control accuracy, and control continuity of the variable frequency multi-split cold storage system, ensures the orderly adaptation of the refrigeration and defrosting processes in multi-temperature cold storage, and optimizes the overall intelligent control level and operational reliability of the system. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the intelligent control system for cold storage based on a variable frequency multi-split host according to an embodiment of the present invention; Figure 2This is a logic diagram of the identification module in an embodiment of the present invention for determining energy conflicts in each temperature zone; Figure 3 This is a sequence diagram showing how the host control module determines the conflict defrosting execution queue in an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0018] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0019] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0020] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0021] Please see Figures 1-3 As shown, this is an intelligent control system for cold storage based on a variable frequency multi-split compressor, comprising a multi-split variable frequency compressor, several indoor units and corresponding air coolers, and a defrosting valve assembly, and further including: The cold storage data acquisition module is used to collect operating data of each temperature zone in the cold storage and the outdoor temperature, and to determine the operating parameters of the air cooler in each temperature zone; The operating data includes temperature setpoint, return air temperature, outlet air temperature, and refrigerant flow rate. The operating parameters of the air cooler include the refrigerant temperature difference between the evaporator inlet and outlet and the air pressure difference between the inlet and outlet. The temperature zone analysis module is used to determine the corresponding temperature zone thermal inertia coefficient based on the operating data of each temperature zone and the outdoor temperature, determine the defrosting urgency index and defrosting thermal shock coefficient based on the operating parameters of each air cooler, predict the cooling demand of the corresponding temperature zone based on the return air temperature, outlet air temperature and outdoor temperature of each temperature zone, and predict the defrosting demand of the corresponding air cooler during the control period based on the defrosting urgency index of each temperature zone. The identification module is used to determine the energy conflict of the corresponding temperature zone based on the cooling demand and defrosting demand. The energy conflict includes cooling-defrosting conflict, defrosting recovery conflict and compound conflict. In response to the existence of energy conflicts, the host control module determines a collaborative scheduling strategy based on the type of energy conflict, including: determining the defrosting execution queue according to the defrosting urgency index and thermal inertia coefficient of each temperature zone, determining the pre-cooling and temperature reduction range of each temperature zone in the queue before defrosting according to the defrosting thermal shock coefficient, and determining the number of air coolers that can perform defrosting simultaneously according to the heating capacity of the multi-split inverter compressor and alternating defrosting of adjacent temperature zones. The control compensation module is used to adjust the speed of the multi-split inverter compressor according to the return air temperature, and to cool the defrost temperature zone using a low return rate in response to defrosting completion.

[0022] In implementation, the temperature setpoints for each temperature zone are read directly. Return air and outlet air temperatures are collected using PT100 platinum resistance temperature sensors. The return air temperature sensor is installed in the middle of the return air side of each indoor unit where airflow is uniform, and the outlet air temperature sensor is installed in the middle of the outlet air side of each indoor unit. Refrigerant flow rates for each temperature zone are collected using vortex flow sensors, which are installed between the electronic expansion valve and the air cooler in each temperature zone's refrigerant branch. Outdoor temperature is collected by a temperature sensor located near the outdoor condenser. Outdoor temperature directly affects the condensing pressure, which in turn affects the compressor's actual upper limit of cooling output.

[0023] It is understandable that the temperature difference between the inlet and outlet of the evaporator directly corresponds to the change in the heat absorbed by the refrigerant in the air cooler, characterizing the degree of degradation of the heat exchange capacity on the refrigerant side; the air pressure difference between the inlet and outlet corresponds to the change in the flow resistance of air flowing through the fins, characterizing the degree of increase in frost thickness and thermal resistance on the air side. The two parameters complement each other from the refrigerant side and the air side to characterize the frost state, avoiding misjudgment caused by interference from a single parameter such as filter blockage and fan speed fluctuations.

[0024] In practice, Class A PT100 platinum resistance temperature sensors are installed on the inlet and outlet pipes of the evaporator of the air cooler, and micro differential pressure sensors with a range of 0-200Pa are installed on the outer side of the fins at the air inlet and outlet of the air cooler. The sampling period of the temperature sensors is set to 30 seconds, and the sampling period of the micro differential pressure sensors is set to 5 seconds. When the air cooler is first put into operation, and the fins are clean and frost-free and the temperature zone is closed and in a stable state, the system collects sensor data for 10 consecutive minutes at each operating level, takes the average value as the frost-free reference value for the corresponding level, and stores it.

[0025] The data collected by the aforementioned sensors are continuously uploaded to the cold storage data acquisition module at preset sampling intervals. The sampling interval for temperature data can be set to the tens of seconds, while the sampling interval for refrigerant flow and pressure difference data can be set to the several seconds.

[0026] In this invention, by continuously tracking the temperature difference between the inlet and outlet refrigerant and the pressure difference between the inlet and outlet air pressure of the evaporator of each air cooler, the evolution trend of the frosting process can be captured, providing trend information for predicting the defrosting urgency index.

[0027] Based on fundamental thermodynamic laws, characteristic coefficients reflecting the inherent properties and real-time state of the system are derived through measurable operating parameters. During implementation, the temperature zone analysis module acquires the return air temperature and outlet air temperature of the temperature zone at the current moment. During system commissioning, a cooling step test is conducted on each temperature zone. Before the test, it is ensured that the temperature zone is sealed without external thermal interference, the air cooler is running at its rated speed, and the loading status of the goods in the warehouse is stable and the loading rate is known. The opening of the electronic expansion valve of the indoor unit of the temperature zone is fixed to the fixed opening specified during commissioning, allowing the refrigerant branch of the temperature zone to supply refrigerant at a constant flow rate. Timing is started simultaneously, and return air temperature data is continuously recorded. After the return air temperature stabilizes at a specified initial value, the fixed refrigerant flow rate is maintained for continuous cooling, and the complete time for the return air temperature to decrease from the specified initial value to the specified final value is recorded as the cooling response time under this condition. The above test is repeated, and the average value is taken. Combined with the theoretical volume of the temperature zone and the known loading rate at the time, a corresponding benchmark relationship between the cooling response time and the thermal inertia coefficient of the temperature zone is established and stored in the system.

[0028] After being put into use, the refrigerant flow rate of the temperature zone is acquired in real time, and the change in return air temperature between adjacent sampling times is recorded. The temperature change rate is obtained by dividing the change rate by the sampling interval, and then the temperature change rate is divided by the corresponding refrigerant flow rate to obtain the temperature response rate caused by a unit refrigerant supply. The current temperature response rate is compared with the benchmark correspondence obtained from the refrigeration step test, and the current temperature zone thermal inertia coefficient is calculated proportionally. The value of the temperature zone thermal inertia coefficient ranges from 0.05 to 5.0. When the refrigeration in the temperature zone is interrupted or the refrigeration capacity changes, the larger the temperature zone thermal inertia coefficient, the smoother the rate of temperature rise or fall.

[0029] Understandably, the inlet and outlet refrigerant temperature difference reflects the proportion of degradation in the current actual heat exchange capacity of the evaporative cooler relative to its frost-free state, while the inlet and outlet air pressure difference reflects the degree to which the frost layer itself obstructs the heat transfer path. By weighting and combining the proportion of the decrease in the inlet and outlet refrigerant temperature difference with the proportion of the increase in the inlet and outlet air pressure difference, a dimensionless index is obtained that comprehensively characterizes the degree of degradation in current heat exchange performance; this is the defrosting urgency index. The higher the value of the defrosting urgency index, the more severe the current frost buildup on the evaporative cooler.

[0030] The fusion weight of the inlet and outlet refrigerant temperature difference and the inlet and outlet air pressure difference was determined by recording the change curves of the two parameters from slight frost to severe frost under different evaporator models and temperature zone settings. The optimization objective was to minimize the time and energy consumption required for the evaporator to return to normal heat exchange state after defrosting, and the optimal fusion coefficient was obtained.

[0031] The temperature zone analysis module obtains the calculated thermal inertia coefficient of the temperature zone where the evaporative cooler is located, and obtains the inlet and outlet air pressure difference of the evaporative cooler from the cold storage data acquisition module. The larger the inlet and outlet air pressure difference, the greater the jump in the heat exchange capacity of the evaporative cooler before and after defrosting. After defrosting, the evaporative cooler will be able to deliver much more cooling capacity to the temperature zone per unit time than before defrosting, forming a concentrated release of short-term cooling demand. On the other hand, the smaller the thermal inertia coefficient of the temperature zone, the faster the temperature drops during the concentrated release of cooling capacity. The system must quickly allocate sufficient compressor cooling capacity to respond, otherwise it will squeeze the normal cooling supply of other temperature zones.

[0032] Therefore, the ratio of the inlet and outlet air pressure difference to the thermal inertia coefficient of the temperature zone is calculated, and the ratio obtained by dividing the inlet and outlet air pressure difference by the thermal inertia coefficient of the temperature zone is used as the defrosting thermal shock coefficient. This ratio quantifies the magnitude of the defrosting heat transfer capacity jump that a unit temperature zone buffer capacity can withstand, eliminating the influence of differences in thermal characteristics between different temperature zones on the assessment of shock intensity, and achieving a unified quantitative assessment of defrosting thermal shock across temperature zones. A larger defrosting thermal shock coefficient indicates a stronger instantaneous cooling demand impact on the system after defrosting, requiring more sufficient cooling capacity margin or more significant pre-cooling measures during coordinated scheduling.

[0033] It should be understood that the deviation between the return air temperature and the set value reflects the current cooling demand in that temperature zone. The larger the deviation, the more priority that temperature zone needs to obtain cooling resources. The difference between the outlet air temperature and the return air temperature reflects the actual cooling intensity output by the air cooler. Simultaneously, the system tracks the rate of temperature change in each temperature zone over multiple consecutive sampling times and calculates the average slope of the return air temperature change over several adjacent sampling periods. If the return air temperature of a certain temperature zone is rapidly approaching the set value, even if the current temperature difference still exists, the system can predict that its cooling demand will decrease in a short period of time. Conversely, if the return air temperature of a certain temperature zone rises instead of falling due to frequent door openings or the arrival of new goods, the system predicts that its cooling demand will continue to increase in the future.

[0034] Based on the return air temperature, the setpoint temperature, and the rate of temperature change for each temperature zone, and considering the constraint of outdoor temperature on the compressor's cooling capacity, the system generates cooling demand values ​​for each time point within the control period for each temperature zone. The baseline cooling capacity for each temperature zone is the standard cooling capacity required per unit time when the zone is sealed without external interference and the return air temperature is stably maintained at the setpoint, serving as the benchmark value for cooling demand. During real-time operation, the system collects the temperature difference between the current temperature zone's return air temperature and the setpoint, as well as the rate of change of the return air temperature within a continuous sampling period. If the temperature is rising at a relatively rapid rate, it indicates that the cooling capacity gap will continue to widen in the future; conversely, the gap will gradually narrow. Combining the temperature difference and the rate of temperature change, the system calculates the real-time cooling capacity gap at the current moment. Based on the cooling capacity gap data from the most recent five consecutive sampling periods, a linear extrapolation method is used to extrapolate the cooling capacity gap change trend corresponding to each time step within the future control period.

[0035] Based on this, according to the performance curve calibrated at the factory of the multi-split inverter compressor, the upper limit of the maximum cooling capacity that the compressor can output under the current outdoor temperature is determined. If the sum of the predicted cooling capacity shortfall and the basic cooling capacity at a certain time point exceeds this upper limit, the upper limit of the compressor's maximum cooling capacity is used as the cooling demand value for that point to avoid exceeding the compressor's load capacity. Finally, the basic cooling capacity and the corresponding predicted cooling capacity shortfall at each time point are added together to obtain the cooling demand value for each time point within the control period.

[0036] The system continuously tracks the defrosting urgency index of each evaporative air cooler, synchronously recording the index value at each moment according to a preset sampling period. It then uses a moving average method to calculate the average rate of increase of the defrosting urgency index over the most recent six consecutive sampling periods, thus characterizing the development trend of the evaporative air cooler's frosting process. Starting from the current defrosting urgency index, the system performs linear extrapolation based on the calculated average rate of increase to predict the time point at which the index reaches the pre-calibrated defrosting trigger threshold.

[0037] The defrost trigger threshold is set differently depending on the temperature zone type. The threshold for the freezing zone is higher than that for the refrigeration zone. The range of the defrost trigger threshold is 0.3 to 0.8. Generally, it is 0.6 to 0.8 for the freezing zone and 0.3 to 0.5 for the refrigeration zone. This threshold is determined by recording the defrost urgency index corresponding to the heat exchange efficiency of the air cooler dropping to 70% of the rated value under different temperature zone settings. This index is the defrost trigger threshold for that temperature zone.

[0038] If the defrosting urgency index shows a significantly faster rate of increase over two consecutive sampling periods, the evaporative cooler is determined to have entered the rapid frosting phase. The system will add it to the defrosting queue 10% in advance to prevent excessive frosting from causing a sharp decline in heat exchange performance. Simultaneously, the system sets a maximum defrosting interval fallback mechanism for each evaporative cooler. When the continuous operating time of the cooler reaches the preset maximum interval threshold, it will be forcibly marked as awaiting defrosting, regardless of whether the current defrosting urgency index has reached the trigger threshold. This prevents prolonged periods without defrosting due to sensor drift or abnormal frosting rates under special operating conditions.

[0039] The specific length of the control period can be set according to the actual operating characteristics and control response cycle of the cold storage, for example, on the order of tens of minutes. The length of this control period can be calibrated by observing the time constant of the temperature response in the temperature zone during the step refrigeration test at the beginning of the cold storage operation.

[0040] In this invention, multi-dimensional characteristic parameters are calculated based on the collected data, and the thermal inertia, defrosting urgency and defrosting thermal shock intensity of each temperature zone are quantitatively characterized. The cooling demand and defrosting demand are accurately predicted by relying on thermodynamic laws and trend prediction methods, so that the system can perceive potential operational contradictions in advance, transforming passive control into active prediction, and providing a scientific and quantitative decision-making basis for energy conflict identification and coordinated scheduling.

[0041] It should be understood that the base cooling capacity refers to the cooling capacity required per unit time to maintain the return air temperature at the set value under stable operating conditions and without external disturbances in that temperature zone. The identification module compares the cooling demand value at each time point with the base cooling capacity one by one, and determines the continuous time interval where the cooling demand value exceeds the base cooling capacity as the peak cooling demand period for that temperature zone. The value of the base cooling capacity can be determined during the system commissioning phase. During the period when each temperature zone is in steady-state operation and there is no door opening operation, the average value of the refrigerant flow rate is recorded, and the cooling capacity corresponding to this average value is taken as the base cooling capacity for that temperature zone.

[0042] The system continuously tracks the defrosting urgency index of each evaporative air cooler, synchronously recording the index value at each moment according to a preset sampling period. It calculates the average rate of change of the defrosting urgency index over the most recent five consecutive sampling periods using a sliding window method, thus characterizing the overall development trend of the air cooler's frosting process. Using the current defrosting urgency index as a baseline value, the system performs linear extrapolation based on the calculated average rate of change to obtain the predicted defrosting urgency index value for each preset time step within the entire control period. This predicted value is directly used as the defrosting demand intensity value for the corresponding time step; a higher value indicates a more urgent defrosting demand for the air cooler at that moment. Finally, the system generates a defrosting demand intensity sequence for each air cooler, covering the entire control period and divided according to preset time steps, and outputs it to the identification module for subsequent energy conflict determination.

[0043] To determine the defrost recovery period, the identification module directly uses the end time of the defrost requirement period as the starting point, defining the duration immediately following the defrost requirement period as the defrost recovery period. This duration can be set to match the typical transition time required for the evaporative air cooler to return to normal cooling after defrosting, for example, 5 to 15 minutes. The specific duration can be determined during system debugging by recording the time from the end of defrosting to the return air temperature returning to near the set value after the first defrosting of each evaporative air cooler.

[0044] Understandably, the defrosting process requires diverting some of the compressor's output capacity to provide defrosting heat, resulting in a decrease in the system's total available cooling capacity. During the defrosting recovery process, the evaporative cooler's heat exchange capacity recovers instantaneously, generating concentrated cooling demand. When these two processes overlap with peak cooling demand, the compressor's available cooling capacity may be insufficient to meet the total cooling demand during the same period, causing temperature fluctuations in the temperature zone.

[0045] In implementation, the identification module compares the defrosting demand period of each air cooler with the peak cooling demand periods of other temperature zones (excluding the air cooler itself) over time. If the defrosting demand period of an air cooler overlaps with the peak cooling demand period of any other temperature zone within the control period, the identification module determines that a defrosting conflict exists and records the temperature zone of the air cooler, the other temperature zone involved in the conflict, and the overlapping time range as a defrosting conflict event. The principle behind this determination is that when an air cooler enters its defrosting demand period, the system needs to provide the compressor's heating capacity required for hot refrigerant defrosting. If another temperature zone is currently experiencing a peak cooling demand period, the compressor's cooling and heating outputs will compete for resources. If this is not avoided in advance, it will result in insufficient cooling in the temperature zone during the peak cooling demand period.

[0046] To determine defrost recovery conflicts, the identification module compares the defrost recovery period of each air cooler with the peak cooling demand periods of all temperature zones on a timeline. The determination of defrost recovery conflicts does not exclude the temperature zone itself; that is, if the defrost recovery period of a certain air cooler overlaps with the peak cooling demand periods of its own temperature zone or other temperature zones, it is determined to be a defrost recovery conflict.

[0047] Understandably, after the evaporative air cooler finishes defrosting, its heat exchange capacity jumps from a frosted state to a frost-free state. When it resumes cooling, it will deliver a large amount of cooling capacity to the corresponding temperature zone in a short period of time, forming a concentrated demand for cooling. If any temperature zone is in the peak period of cooling demand at this time, the total cooling capacity of the compressor will face the dual pressure of the defrosting recovery demand and the original peak cooling demand, which may easily cause compressor overload or temperature fluctuations throughout the warehouse.

[0048] Understandably, multiple energy conflicts within the same time period can affect each other, requiring unified coordination from a global perspective. In implementation, the identification module groups all identified energy conflicts within the control period by time node, with each group corresponding to a continuous time interval. For each time interval, it counts the number of cooling / defrosting conflicts and defrosting recovery conflicts. If at least one cooling / defrosting conflict and at least one defrosting recovery conflict exist simultaneously within the interval, these conflicts are merged into a composite conflict, and all temperature zones and air coolers involved in this composite conflict are marked. Finally, all conflicts are organized into a conflict list in chronological order and transmitted to the main control module. The main control module then formulates corresponding collaborative scheduling strategies based on the conflict type and priority.

[0049] In this invention, based on the predicted cooling and defrosting demands, the system accurately distinguishes between cooling-defrosting conflicts, defrosting recovery conflicts, and compound conflicts. It completes the collection, classification, and merging of conflict information, clearly defines the conflict type, the temperature range involved, and the time range, enabling the system to accurately locate operational contradictions and output clear and complete conflict judgment results to the host control module, thereby improving the pertinence and effectiveness of the scheduling strategy.

[0050] Understandably, when the conflict type is a cooling-defrosting conflict, the core issue is that the defrosting demand period of one air cooler overlaps with the peak cooling demand period of another temperature zone. The compressor's heating capacity required for defrosting will reduce the cooling capacity. This conflict can be resolved by adjusting the defrosting execution queue to postpone the defrosting operation until after the peak cooling period, without needing to use pre-cooling or quantity restriction measures.

[0051] When the conflict type is a defrost-to-recovery conflict, the core contradiction lies in the surge in heat exchange capacity of a certain evaporative cooler after defrosting, leading to a concentrated demand for cooling as it resumes operation. This demand overlaps with the peak cooling demand in another temperature zone. Simply adjusting the defrosting sequence is insufficient to eliminate the impact of the recovery phase. It is also necessary to pre-cool the temperature zone where the evaporative cooler is located to reduce the peak demand, and to prevent the cumulative impact of multiple evaporative coolers resuming operation by limiting the number of simultaneous defrost cycles and alternating between adjacent defrost cycles.

[0052] When the conflict type is a compound conflict, the defrosting conflict and the defrosting recovery conflict exist simultaneously within the same time period, making the contradiction the most complex. In addition, the air coolers involved in the compound conflict that are waiting to be defrosted are given the highest priority in the defrosting execution queue because the two conflicts overlap during their time period. If they are not handled in time, they will cause more serious system capacity shortages. Prioritizing defrosting can resolve the source of the conflict as soon as possible and shorten the time the system is in a high-risk state.

[0053] Quantitative calculations are performed based on the inherent physical characteristics of temperature zones and air coolers, enabling scheduling decisions to objectively reflect the actual operating status of the system. In implementation, the main control module obtains a list of air coolers awaiting defrosting from the identification module and acquires the defrosting urgency index and the temperature zone thermal inertia coefficient of each air cooler from the temperature zone analysis module. Sorting is primarily based on the defrosting urgency index; air coolers with higher urgency indices are prioritized because they experience the most severe frosting, and further delays will lead to further deterioration of heat exchange performance or even frosting blockage. When the defrosting urgency indices of multiple air coolers fall within the same preset urgency range, the temperature zone thermal inertia coefficient is used as a secondary sorting criterion. Temperature zones with higher thermal inertia coefficients experience slower temperature increases during defrosting and can be prioritized for defrosting without causing the storage temperature to exceed the limit. The range for determining the same preset urgency range for the defrosting urgency index can be determined through system debugging; for example, the entire range of the defrosting urgency index can be divided into several intervals, with those falling within the same interval considered identical.

[0054] To determine the pre-cooling temperature reduction range, the main control module obtains the defrosting thermal shock coefficient of the air cooler to be defrosted. The pre-cooling temperature reduction range is positively correlated with the defrosting thermal shock coefficient. The larger the defrosting thermal shock coefficient, the stronger the impact on the system when the air cooler resumes cooling after defrosting. Therefore, the temperature in this zone needs to be reduced to a level lower than the set value before defrosting begins, allowing for a larger temperature rise margin to offset the temperature rise during defrosting. The specific pre-cooling relationship can be determined during system commissioning by testing the temperature rise of air coolers with different defrosting thermal shock coefficients during defrosting under the same operating conditions. The pre-cooling temperature reduction range required for each defrosting thermal shock coefficient is obtained, with the constraint that the temperature rise during defrosting does not exceed the allowable upper limit.

[0055] Different air coolers have different defrosting thermal shock coefficients. Air coolers with a larger thermal shock coefficient will generate a greater cooling demand after defrosting. If multiple units defrost at the same time, it will exceed the compressor's load capacity. In order to avoid mutual interference of cooling capacity between adjacent temperature zones due to simultaneous defrosting or simultaneous resumption of cooling, it is necessary to dynamically adjust the actual number of units defrosting at the same time.

[0056] During implementation, the main control module obtains the upper limit of the current available heating capacity of the multi-split inverter compressor. This upper limit is obtained by subtracting the cooling output of the currently operating non-defrost temperature zone from the compressor's total rated capacity. The amount of heat required for defrosting a single evaporative air cooler is determined by the model and specifications of that air cooler, and is stored as equipment parameters in the main control module when the system is put into operation. For example, the defrosting heat requirement of a certain model of air cooler can be found in the equipment manual or calibrated through the initial defrost test. The upper limit of the compressor's current available heating capacity is divided by the amount of heat required for defrosting a single air cooler, and the integer part is taken as the upper limit of the number of air coolers that can be defrosted simultaneously.

[0057] The main control module selects air coolers sequentially from the defrosting queue as the defrosting targets for the same batch, with the number selected not exceeding the aforementioned upper limit. During the selection process, it checks whether each candidate air cooler belongs to an adjacent temperature zone with any air coolers already selected in the same batch. If they belong to adjacent temperature zones, the air cooler is skipped, and the selection continues to the next air cooler. The skipped air cooler remains in its original position in the queue, waiting to participate in the selection in the next batch. The determination of adjacent temperature zones is based on the physical layout number of each temperature zone in the cold storage; temperature zones with adjacent numbers are considered adjacent temperature zones. It is understandable that the thermal resistance of the partition walls between adjacent temperature zones is limited. If adjacent temperature zones defrost simultaneously, the heat introduced during defrosting will be conducted between them through the partition walls, exacerbating the temperature rise between them. At the same time, after defrosting, both adjacent temperature zones resume cooling simultaneously, and the concentrated release of cooling demand will exacerbate local load fluctuations.

[0058] In this invention, a coordinated scheduling strategy is matched to different types of energy conflicts. The defrosting execution queue, pre-cooling range, and number of simultaneous defrosting are reasonably determined, and alternating defrosting is performed in adjacent temperature zones. This achieves global coordination between defrosting actions and cooling demands, avoids resource competition, overload, and temperature fluctuations in the system, and enables the multi-split unit to maintain an orderly, stable, and efficient operating state under complex conditions.

[0059] During defrosting, some compressor capacity is used to provide defrosting heat, resulting in a corresponding reduction in cooling capacity available in non-defrosting temperature zones. The control compensation module continuously monitors the difference between the return air temperature and the set value for each non-defrosting temperature zone. When the difference widens, it indicates insufficient cooling supply in that zone. In this case, the speed of the multi-split inverter compressor is increased to increase the total cooling output and compensate for the capacity occupied by defrosting. Simultaneously, the control compensation module obtains the current refrigerant flow rate in each non-defrosting temperature zone and compares it with the baseline flow rate required to maintain the set value in that zone. The baseline flow rate can be determined by recording the average refrigerant flow rate of each zone when the return air temperature equals the set value during steady-state system operation. When the actual flow rate is lower than the baseline flow rate, the opening of the electronic expansion valve of the indoor unit in that zone is increased to increase the refrigerant flow rate, restoring the cooling supply to the non-defrosting temperature zone to normal levels and preventing temperature drift during defrosting.

[0060] After defrosting, the heat exchange capacity of the evaporative cooler jumps from a frosted state to a frost-free state. If the temperature zone is then cooled at the normal cooling rate, the cooling demand will be released all at once, impacting the compressor and other temperature zones. The control compensation module obtains the defrosting thermal shock coefficient of the defrosting temperature zone from the temperature zone analysis module and determines a lower upper limit for the temperature recovery rate than during normal cooling. The higher the defrosting thermal shock coefficient, the lower the upper limit for the temperature recovery rate, allowing for a smoother, gradual cooling process. The control compensation module limits the opening of the electronic expansion valve of the indoor unit in that temperature zone, ensuring that the cooling rate corresponding to the refrigerant flow does not exceed the upper limit for the temperature recovery rate, until the deviation between the return air temperature of that temperature zone and the set value is reduced to a preset range. The preset range is generally 0.3℃ to 0.8℃, determined through a limited number of tests and calibrated, and adjusted according to the temperature control accuracy requirements of the temperature zone.

[0061] In this invention, the compressor output is dynamically adjusted and the refrigerant distribution is optimized. Precise flow compensation is performed for the non-defrost temperature zone. At the same time, the cooling process of the defrost temperature zone is controlled in a smooth manner. This effectively balances the refrigeration supply between the defrost and non-defrost temperature zones, suppresses temperature shocks and load fluctuations, ensures stable and reliable temperature control throughout the warehouse, and improves the overall operational stability and control accuracy of the system.

[0062] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0063] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A cold storage intelligent control system based on a variable frequency multi-split compressor, comprising a multi-split variable frequency compressor, several indoor units and corresponding air coolers and defrosting valve assemblies, characterized in that, Also includes: The cold storage data acquisition module is used to collect operating data of each temperature zone in the cold storage and the outdoor temperature, and to determine the operating parameters of the air cooler in each temperature zone; The operating data includes temperature setpoint, return air temperature, outlet air temperature, and refrigerant flow rate. The operating parameters of the air cooler include the refrigerant temperature difference between the evaporator inlet and outlet and the air pressure difference between the inlet and outlet. The temperature zone analysis module is used to determine the corresponding temperature zone thermal inertia coefficient based on the operating data of each temperature zone and the outdoor temperature, determine the defrosting urgency index and defrosting thermal shock coefficient based on the operating parameters of each air cooler, predict the cooling demand of the corresponding temperature zone based on the return air temperature, outlet air temperature and outdoor temperature of each temperature zone, and predict the defrosting demand of the corresponding air cooler during the control period based on the defrosting urgency index of each temperature zone. The identification module is used to determine the energy conflict of the corresponding temperature zone based on the cooling demand and defrosting demand. The energy conflict includes cooling-defrosting conflict, defrosting recovery conflict and compound conflict. In response to the existence of energy conflicts, the host control module determines a collaborative scheduling strategy based on the type of energy conflict, including: determining a defrosting execution queue according to the defrosting urgency index and thermal inertia coefficient of each temperature zone; determining the pre-cooling and temperature reduction range of each temperature zone in the queue before defrosting according to the defrosting thermal shock coefficient; and determining the number of air coolers that can perform defrosting simultaneously according to the heating capacity of the multi-split inverter compressor and alternating defrosting of adjacent temperature zones.

2. The intelligent control system for cold storage based on a variable frequency multi-unit chiller as described in claim 1, characterized in that, The temperature zone analysis module is configured to determine the rate of temperature change under the current operating condition based on the return air temperature and the outlet air temperature of each temperature zone, and to determine the temperature zone thermal inertia coefficient of that temperature zone in conjunction with the refrigerant flow rate of that temperature zone. Furthermore, the defrosting urgency index of the air cooler is determined based on the temperature difference between the inlet and outlet refrigerant of the evaporator and the pressure difference between the inlet and outlet air pressure of the air cooler; the corresponding defrosting thermal shock coefficient is calculated based on the temperature zone thermal inertia coefficient of each temperature zone and the corresponding air pressure difference between the inlet and outlet air pressure of the air cooler.

3. The intelligent control system for cold storage based on a variable frequency multi-unit chiller according to claim 2, characterized in that, The temperature zone analysis module is also configured to predict the cooling demand of the corresponding temperature zone during the control period based on the temperature change rate and the outdoor temperature. Furthermore, based on the changing trend of the defrosting urgency index of each air cooler, the defrosting demand of the corresponding air cooler during the control period is predicted.

4. The intelligent control system for cold storage based on a variable frequency multi-unit chiller according to claim 3, characterized in that, The identification module is configured during the control period to determine the period when the cooling demand value of each temperature zone exceeds the basic cooling capacity as the peak cooling demand period of that temperature zone, to determine the period when the defrosting urgency index of each air cooler reaches the defrosting trigger threshold as the defrosting demand period, and to determine the period immediately following the defrosting demand period as the defrosting recovery period.

5. The intelligent control system for cold storage based on a variable frequency multi-unit chiller according to claim 4, characterized in that, The identification module is further configured to determine the energy conflict in the corresponding temperature zone based on the cooling and defrosting requirements, including: If the identification result shows that the defrosting demand period overlaps with the peak cooling demand period of any temperature zone, it is determined that there is a cooling defrosting conflict. If the defrost recovery period overlaps with the peak cooling demand period of any temperature zone, then the defrost recovery period is determined to be conflicting. In response to the identification results of no time period overlap, it is determined that there is no energy conflict.

6. The intelligent control system for cold storage based on a variable frequency multi-unit chiller according to claim 5, characterized in that, The identification module is also configured to determine the energy conflict during the period when both the cooling defrost conflict and the defrost recovery conflict exist simultaneously as a composite conflict.

7. The intelligent control system for cold storage based on a variable frequency multi-unit main unit according to claim 6, characterized in that, The host control module determines the corresponding cooperative scheduling strategy in response to the type of energy conflict, wherein: In response to the aforementioned cooling and defrosting conflict, the determined collaborative scheduling strategy is to determine the defrosting execution queue based on the defrosting urgency index of each temperature zone and the thermal inertia coefficient of the temperature zone. In response to the defrost recovery conflict or the combined conflict, the determined collaborative scheduling strategy includes: The defrosting execution queue is determined based on the defrosting urgency index of each temperature zone and the thermal inertia coefficient of each temperature zone. The pre-cooling and temperature reduction range before defrosting in each temperature zone in the queue is determined based on the defrosting thermal shock coefficient. The number of air coolers that perform defrosting simultaneously is determined and alternating defrosting is adopted in adjacent temperature zones. In the aforementioned compound conflict, the air cooler awaiting defrosting has a high priority in the defrosting execution queue.

8. The intelligent control system for cold storage based on a variable frequency multi-unit chiller according to claim 7, characterized in that, In response to any of the energy conflict determination results, the host control module obtains the defrosting urgency index and the temperature zone thermal inertia coefficient of the air cooler to be defrosted, sorts the defrosting urgency index from high to low, and sorts the air coolers in the same preset urgency interval of the defrosting urgency index from large to small according to the temperature zone thermal inertia coefficient. The sorting result is used as the defrosting execution queue.

9. The intelligent control system for cold storage based on a variable frequency multi-unit chiller according to claim 1, characterized in that, The pre-cooling temperature drop determined by the host control module is positively correlated with the defrosting thermal shock coefficient.

10. The intelligent control system for cold storage based on a variable frequency multi-unit host according to claim 7, characterized in that, The host control module obtains the current available heating capacity limit of the multi-split inverter compressor, determines the maximum number of air coolers that can be defrosted simultaneously based on the amount of heat required for defrosting a single air cooler, and selects air coolers in the defrosting execution queue that do not exceed the maximum number as the same batch of defrosting targets. Among the items to be defrosted in the same batch, there are no air coolers belonging to adjacent temperature zones.

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