Air conditioner having multiple defrost modes

Abstract

This invention relates to the field of home appliance technology, specifically to an air conditioner with multiple defrosting modes. The air conditioner includes a refrigerant circulation loop, an outdoor ambient temperature sensor, an outdoor coil temperature sensor, and a controller. After the air conditioner is turned on for heating and the compressor starts, the controller acquires the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity. It determines the dew point temperature based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship. It determines the target temperature difference based on the dew point temperature and the outdoor coil temperature. It determines the frost thickness based on the compressor running time and the target temperature difference. Based on the frost thickness, outdoor ambient temperature, and compressor running time, the controller controls the air conditioner to enter the corresponding target defrosting mode. This improves the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner, thereby improving the accuracy of defrosting intervention and the reliability of the air conditioner.

Description

Technical Field

[0001] This invention relates to the field of home appliance technology, and in particular to an air conditioner with multiple defrosting modes. Background Technology

[0002] When air conditioners are operating in heating mode during winter, the outdoor heat exchanger is prone to frost formation due to the temperature difference with the environment. If not handled promptly, the accumulated frost will not only reduce heat exchange efficiency but may even damage the equipment in severe cases. Currently, the main defrosting technologies are reverse defrosting and hot gas defrosting. Reverse defrosting is primarily for thick frost conditions, where heating capacity has significantly decreased. This technology switches to the refrigeration cycle via a four-way valve, using the high-temperature, high-pressure gaseous refrigerant discharged from the compressor to directly defrost. While highly efficient, this process involves fan shutdown, four-way valve switching causing refrigerant impact noise and energy loss. Furthermore, the room temperature drop after defrosting typically exceeds 7°C, and the recovery time is relatively long. Hot gas defrosting, on the other hand, is suitable for light frost conditions. It does not require four-way valve switching and uses high-temperature, high-pressure refrigerant on the indoor side for defrosting. While avoiding the noise and energy consumption associated with switching, and limiting the room temperature drop to around 3°C, the recovery speed is relatively slower.

[0003] In addition, a defrosting method for mild frost conditions is proposed in the related technologies. This method keeps the four-way valve from reversing, reduces the compressor frequency, increases the expansion valve opening, and adjusts the speed of the indoor and outdoor fans. Because the noise from the four-way valve reversing is avoided, and the indoor fan continues to run to maintain heating, the room temperature drop is only about 1°C (significantly lower than hot air defrosting), and the temperature recovery speed after defrosting is more than twice that of hot air defrosting.

[0004] When the outdoor ambient temperature is above 0℃, the defrosting frequency of micro-frost defrosting is higher than that of hot air defrosting and reverse defrosting. However, the indoor temperature drop is less significant with micro-frost defrosting and reverse defrosting, resulting in better overall heat exchange efficiency and performance. Therefore, it is crucial to select the most appropriate defrosting method based on environmental conditions and the degree of frost buildup on the outdoor heat exchanger. An inappropriate defrosting method may not only fail to deliver its advantages but could also produce the opposite effect, even impacting the reliability of the air conditioner.

[0005] However, the existing defrosting logic lacks the accuracy to determine the thickness of the frost layer, making it difficult to support a differentiated defrosting strategy based on precise thickness. This may lead to delayed defrosting or incomplete defrosting. The residual water-frost mixture will quickly solidify into an ice layer when heating is resumed, creating a vicious cycle that increases the difficulty of subsequent defrosting and severely restricts the reliability and energy efficiency of air conditioners in low-temperature and high-humidity environments. Summary of the Invention

[0006] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0007] Therefore, the purpose of this invention is to propose an air conditioner with multiple defrosting modes. This air conditioner can dynamically calculate the frost thickness according to changes in the outdoor environment, improving the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner. Furthermore, after controlling the air conditioner to enter the micro-frost defrosting mode, it controls the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range of the outdoor environment. This involves using a highly efficient strategy for rapid defrosting in high-temperature ranges and a conservative strategy to prevent icing in low-temperature ranges, ensuring the efficiency and safety of micro-frost defrosting under various operating conditions. This effectively avoids incomplete defrosting or secondary icing caused by excessively low ambient temperatures, while minimizing indoor temperature fluctuations, thereby improving the heating reliability and user comfort of the air conditioner in low-temperature and high-humidity environments.

[0008] This invention provides an air conditioner with multiple defrosting modes. The air conditioner includes a refrigerant circulation loop, in which the refrigerant circulates in a loop consisting of a compressor, a condenser, an expansion valve, and an evaporator. One of the condenser and the evaporator is an outdoor heat exchanger, and the other is an indoor heat exchanger. Outdoor ambient temperature sensor, used to detect outdoor ambient temperature; Outdoor coil temperature sensor, used to detect the temperature of outdoor coil; The controller is configured to: After the air conditioner is turned on for heating and the compressor is started, the outdoor ambient temperature, the outdoor coil temperature, the compressor running time, and the outdoor relative humidity are obtained. The dew point temperature is determined based on the outdoor ambient temperature, the outdoor relative humidity, and a preset mapping relationship, wherein the preset mapping relationship includes multiple sets of correspondences between outdoor ambient temperature, outdoor relative humidity, and dew point temperature. The target temperature difference is determined based on the dew point temperature and the outdoor coil temperature. The frost thickness of the air conditioner is determined based on the compressor's operating time and the target temperature difference. Based on the frost thickness, the outdoor ambient temperature, and the compressor's operating time, the air conditioner is controlled to enter the corresponding target defrosting mode, wherein the target defrosting mode includes a micro-frost defrosting mode, a hot air defrosting mode, and a reverse defrosting mode. Wherein, after controlling the air conditioner to enter the micro-frost defrosting mode, the controller is configured to: Based on the target temperature range of the outdoor ambient temperature, the air conditioner is controlled to execute a micro-frost defrosting strategy corresponding to the target temperature range. Different temperature ranges correspond to different micro-frost defrosting strategies, and the conditions for triggering the compressor to reduce its frequency are different under different micro-frost defrosting strategies.

[0009] The above technical solution has the following advantages or beneficial effects: After the air conditioner is turned on for heating and the compressor starts, the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity are acquired. The dew point temperature is determined based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship. Then, the target temperature difference is calculated based on the dew point temperature and the outdoor coil temperature. This difference is then integrated based on the compressor running time and the target temperature difference to calculate the frost thickness of the air conditioner. This allows for dynamic calculation of frost thickness based on changes in the outdoor environment, improving the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner. After calculating the frost thickness, the air conditioner is controlled to enter one of three modes: micro-frost defrosting, hot gas defrosting, or reverse defrosting, thereby improving the accuracy of defrosting intervention and the reliability of the air conditioner. After the air conditioner enters the micro-frost defrosting mode, it executes a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature. This strategy employs a high-efficiency approach for rapid defrosting in high-temperature ranges and a conservative approach to prevent icing in low-temperature ranges. This ensures the efficiency and safety of micro-frost defrosting under various operating conditions, effectively avoiding incomplete defrosting or secondary icing caused by excessively low ambient temperatures. At the same time, it minimizes indoor temperature fluctuations, thereby improving the heating reliability and user comfort of the air conditioner in low-temperature and high-humidity environments.

[0010] In addition, the air conditioner with multiple defrosting modes according to embodiments of the present invention may also have the following additional technical features: Furthermore, when determining the frost thickness of the air conditioner based on the compressor's operating time and the target temperature difference, the controller is configured to: determine the frost thickness of the air conditioner according to the compressor's operating time and the target temperature difference, and according to a preset algorithm, wherein the frost thickness is positively correlated with the target temperature difference and the compressor's operating time; the preset algorithm includes: Where H represents the frost thickness, t_js represents the compressor running time, △TL represents the target temperature difference, and k is a preset constant.

[0011] The above technical solution has the following advantages or beneficial effects: it can dynamically calculate the frost thickness based on changes in the outdoor environment, thereby improving the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner.

[0012] Furthermore, based on the frost thickness, the outdoor ambient temperature, and the compressor's operating time, the air conditioner is controlled to enter the corresponding target defrosting mode. The controller is configured to: acquire the continuous operating time of the air conditioner executing the micro-frost defrosting mode, the cumulative operating time of executing the hot air defrosting mode, and the cumulative operating time of executing the reverse defrosting mode; when the frost thickness is greater than or equal to a first frost thickness threshold and less than a second frost thickness threshold, and the outdoor ambient temperature is greater than a first outdoor ambient temperature threshold, and the first outdoor ambient temperature threshold is greater than a first preset temperature threshold. When the continuous running time of the micro-frost defrosting mode is greater than or equal to the running time of the compressor, the air conditioner is controlled to enter the micro-frost defrosting mode; when the frost thickness is greater than or equal to the second frost thickness threshold and less than the third frost thickness threshold, and the outdoor ambient temperature is greater than or equal to the second outdoor ambient temperature threshold, and the cumulative running time of the hot air defrosting mode is greater than or equal to the running time of the compressor, the air conditioner is controlled to enter the hot air defrosting mode; when the frost thickness is greater than or equal to the third frost thickness threshold, the air conditioner is controlled to enter the reverse defrosting mode.

[0013] The above technical solution has the following advantages or beneficial effects: it achieves precise matching of defrosting modes under different frost levels and environmental conditions: the micro-frost defrosting mode is used in the micro-frost stage to avoid over-defrosting, the hot gas defrosting mode is used in the medium frost stage to balance defrosting efficiency and heating continuity, and the reverse defrosting mode is used in the thick frost stage to ensure thorough defrosting. This not only improves the targeting and energy efficiency of the defrosting process, but also reduces unnecessary mode switching, ensuring the heating stability and operational reliability of the air conditioner.

[0014] Furthermore, when acquiring the outdoor relative humidity, the controller is configured to: when the air conditioner includes an outdoor humidity sensor and the outdoor humidity sensor is functioning normally, use the humidity value detected by the outdoor humidity sensor as the outdoor relative humidity; or, when the air conditioner does not include the outdoor humidity sensor or the air conditioner includes the outdoor humidity sensor but the outdoor humidity sensor is not functioning normally, use the humidity value predicted based on the outdoor ambient temperature, the operating parameters of the air conditioner, and a pre-trained humidity prediction model as the outdoor relative humidity.

[0015] The above technical solution has the following advantages or beneficial effects: By directly using the measured data of a high-precision humidity sensor as the control basis, the accuracy and real-time nature of humidity acquisition can be ensured, providing reliable data support for the subsequent start and stop judgment of the micro-frost defrosting mode, thereby improving the air conditioner's adaptability in different environments and the accuracy of defrosting control; or, by predicting humidity values ​​through a humidity prediction model, while ensuring comparable accuracy, it can be lower in cost, more environmentally resistant, and faster in response to different temperatures than a physical humidity sensor, and has higher stability even when exposed to indoor and outdoor environments for a long time, thus enabling accurate prediction of outdoor relative humidity.

[0016] Furthermore, when using the humidity value predicted based on the outdoor ambient temperature, the air conditioner's operating parameters, and a pre-trained humidity prediction model as the outdoor relative humidity, the controller is configured to: update the outdoor relative humidity according to preset update conditions; wherein, the preset update conditions include: when the compressor's operating time is greater than or equal to a first preset operating time, acquiring the compressor's operating frequency change value and the indoor heat exchange temperature difference every second preset operating time, wherein the indoor heat exchange temperature difference is determined based on the difference between the outdoor ambient temperature and the outdoor coil temperature; when the compressor's operating frequency change value is less than or equal to a preset frequency change value, and the indoor heat exchange temperature difference is less than a preset heat exchange temperature difference threshold, updating the outdoor relative humidity once every second preset operating time. The outdoor relative humidity; or, the heating operation time of the air conditioner in heating mode is obtained, and when the heating operation time is greater than or equal to a third preset operation time, the outdoor relative humidity is updated every fourth preset operation time; or, when the air conditioner is in a stopped state or enters the corresponding target defrost mode, the update of the outdoor relative humidity is paused; when updating the outdoor relative humidity according to the preset update conditions, the controller is also configured to: when the air conditioner is in an operating state that does not meet the preset update conditions, maintain the outdoor relative humidity at the humidity value determined when the preset update conditions were met last time, until the operating state of the air conditioner meets the preset update conditions again, and then redetermine and update the outdoor relative humidity.

[0017] The above technical solution has the following advantages or beneficial effects: it ensures the reliability and accuracy of outdoor relative humidity data, avoids erroneous humidity data caused by the failure of the humidity prediction model during the non-steady-state operation of the air conditioner, prevents control deviations such as false defrosting and frequent defrosting caused by abnormal fluctuations in humidity data, ensures the continuity and reliability of outdoor relative humidity data, and provides stable environmental parameter support for the precise defrosting control and efficient heating operation of the air conditioner.

[0018] Furthermore, the controller is also configured to: if the compressor is starting up for the first time, and the initial start-up time of the compressor is less than a fifth preset running time, and / or, when the air conditioner enters the corresponding target defrost mode, pause the prediction of the outdoor relative humidity, and determine the dew point temperature based on the outdoor relative humidity obtained from the last prediction before the pause prediction; when the compressor stops and restarts after meeting the shutdown conditions, and the shutdown time of the compressor is less than a sixth preset running time, and the running time after the compressor restarts is less than the fifth preset running time, determine the dew point temperature based on the outdoor relative humidity before the compressor stops, wherein the shutdown conditions include compressor failure or the compressor reaching a set temperature; if the shutdown time of the compressor is greater than or equal to the sixth preset running time, then the current start of the compressor is taken as the first start-up, and the step of the compressor being the first start-up is executed.

[0019] The above technical solution has the following advantages or beneficial effects: it can ensure the reliability of humidity data and significantly improve the accuracy of defrosting determination.

[0020] Furthermore, the air conditioner also includes: an indoor coil temperature sensor for detecting the indoor coil temperature; an indoor fan for rotating to drive indoor air through the indoor heat exchanger, so that the indoor heat exchanger exchanges heat with the indoor air; and an outdoor fan for rotating to drive outdoor air through the outdoor heat exchanger, so that the air exchanges heat with the outdoor heat exchanger through its temperature, thus defrosting the outdoor heat exchanger. When controlling the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the controller is configured to: when the outdoor ambient temperature is greater than a certain threshold... When the outdoor ambient temperature is less than or equal to a third preset temperature threshold, the air conditioner is controlled to execute a first micro-frost defrosting strategy. When the air conditioner executes the first micro-frost defrosting strategy, the controller is configured to: control the air conditioner to enter the first defrosting stage, and during the first defrosting stage, control the indoor fan to reduce its speed from its current speed to a target speed corresponding to the current micro-frost defrosting strategy, control the four-way valve to maintain its current reversing state, control the compressor to maintain its current operating frequency, control the expansion valve to adjust its opening to a preset maximum opening, and control the outdoor fan to stop operating; obtain the... The air conditioner performs the first defrost stage for a first operating time, with a first indoor coil temperature and a first outdoor coil temperature. Based on the first indoor coil temperature, the first outdoor coil temperature, and the first operating time, it is determined whether the air conditioner meets a first preset condition. If so, the air conditioner is controlled to exit the first defrost stage and enter a second defrost stage. The first preset condition includes one of the following: the first operating time reaches a first preset maximum operating time; the first indoor coil temperature is less than or equal to a preset minimum indoor coil temperature threshold, and the first outdoor coil temperature is greater than or equal to a first preset outdoor coil temperature threshold. The temperature threshold is set, and the temperature of the first outdoor coil is less than or equal to the second preset outdoor coil temperature threshold. After entering the second defrosting stage, the controller is configured to: control the compressor to reduce its frequency to the first target operating frequency according to the first preset frequency reduction rate; control the indoor fan to maintain the target speed corresponding to the current micro-frost defrosting strategy; control the opening of the expansion valve to maintain the preset maximum opening; control the four-way valve to maintain the current reversing state unchanged; and control the outdoor fan to operate at the heating operating speed or increase the speed by the first preset speed at the heating operating speed, wherein the first target operating frequency is greater than or equal to the preset minimum operating frequency.

[0021] The above technical solution has the following advantages or beneficial effects: while ensuring the defrosting effect, it effectively reduces energy consumption and improves the stability of system operation.

[0022] Furthermore, when controlling the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the controller is also configured to: control the air conditioner to execute a second micro-frost defrosting strategy when the outdoor ambient temperature is greater than the third preset temperature threshold; when controlling the air conditioner to execute the second micro-frost defrosting strategy, the controller is configured to: control the indoor fan to reduce its speed from the current speed to the target speed corresponding to the current micro-frost defrosting strategy, control the four-way valve to maintain its current reversing state, control the compressor to maintain its current operating frequency, control the expansion valve to maintain its current opening, and control the outdoor fan to maintain its current speed; obtain the... The air conditioner executes the second micro-frost defrosting strategy for a second operating time and at a second indoor coil temperature. When the second indoor coil temperature is greater than or equal to a preset maximum indoor coil temperature threshold, or when the second operating time reaches a second preset maximum operating time, the compressor is controlled to reduce its frequency from the current operating frequency to the second target operating frequency according to a second preset frequency reduction rate. The outdoor fan is controlled to maintain its current speed or to increase its speed by a second preset speed. The expansion valve is controlled to adjust its opening from the current opening to the preset maximum opening. The indoor fan is controlled to maintain its target speed corresponding to the current micro-frost defrosting strategy. The second preset target frequency is greater than or equal to the preset minimum operating frequency.

[0023] The above technical solution has the following advantages or beneficial effects: executing the second micro-frost defrosting strategy in the high-efficiency temperature range of micro-frost defrosting effectively improves the defrosting efficiency of micro-frost defrosting in the low-efficiency temperature range and greatly expands the temperature range that micro-frost defrosting can be applied to.

[0024] Furthermore, the controller is also configured to: during the execution of the first micro-frost defrosting strategy, acquire a second outdoor coil temperature and a third operating time for executing the first micro-frost defrosting strategy; determine a first temperature difference threshold based on the outdoor relative humidity and the outdoor ambient temperature; determine a second temperature difference threshold between the third preset temperature threshold and the first temperature difference threshold; when the air conditioner is determined to meet the first micro-frost defrosting exit condition based on the third operating time, the second outdoor coil temperature, and the second temperature difference threshold, control the air conditioner to exit the micro-frost defrosting mode; and during the execution of the second micro-frost defrosting strategy, acquire a third outdoor coil temperature and a fourth operating time for executing the second micro-frost defrosting; when the air conditioner is determined to meet the second micro-frost defrosting exit condition based on the third outdoor coil temperature and the fourth operating time, control the air conditioner to exit the micro-frost defrosting mode; the first micro-frost defrosting exit condition includes one of the following: The third operating time reaches the third preset maximum operating time; the second outdoor coil temperature is greater than or equal to the second temperature difference threshold, and the third operating time reaches the first preset operating time; the second micro-frost defrosting exit condition includes one of the following: the fourth operating time reaches the fourth preset maximum operating time; the third outdoor coil temperature is greater than or equal to the third preset temperature threshold, and the fourth operating time reaches the second preset operating time; wherein, after controlling the air conditioner to exit the micro-frost defrosting mode, the controller is configured to: control the compressor to increase according to a preset frequency increase rate, and after a first preset time delay, control the expansion valve, the indoor fan and the outdoor fan to return to the heating operation state; after controlling the air conditioner to exit the micro-frost defrosting mode, the controller is also configured to: when the time after the air conditioner exits the micro-frost defrosting mode is less than a preset time, suspend the execution of the entry judgment of the reverse defrosting mode.

[0025] The above technical solution has the following advantages or beneficial effects: By introducing a relative humidity-corrected temperature difference threshold, it can more accurately match the frosting characteristics under different humidity environments, ensuring timely exit after the frost layer has completely melted, avoiding ineffective operation; and, by combining temperature judgment and time protection, it can ensure rapid recovery of heating when the frost layer has completely melted, improving comfort, and prevent defrosting dead loops caused by sensor failure or extreme operating conditions, thereby ensuring the reliability and safety of air conditioner operation; at the same time, a protective delay mechanism is set up, which can effectively avoid the unstable stage of drastic fluctuations in outdoor heat exchanger tube temperature during the initial stage of compressor frequency rise, preventing misjudgment of outdoor heat exchange temperature difference caused by transient temperature changes, thereby avoiding the system from erroneously triggering the reverse defrosting mode just after the micro-frost defrosting ends, ensuring the accuracy of defrosting logic, and reducing the impact of unnecessary mode switching on system stability and user comfort.

[0026] Furthermore, when determining the target temperature difference based on the dew point temperature and the outdoor coil temperature, the controller is configured to: determine the difference between the dew point temperature and the outdoor coil temperature; when the difference is greater than a fourth preset temperature threshold and the outdoor coil temperature is less than the fourth preset temperature threshold, use the difference as the target temperature difference; when the difference is less than or equal to the fourth preset temperature threshold, or when the outdoor coil temperature is greater than or equal to the fourth preset temperature threshold, correct the target temperature difference to the fourth preset temperature threshold.

[0027] The above technical solution has the following advantages or beneficial effects: by limiting the lower limit of the target temperature difference, it ensures that the effective calculation of frost thickness is only performed under working conditions with actual frost risk, avoiding invalid calculations and improving the accuracy of defrosting control.

[0028] To address the aforementioned problems, this invention also proposes a defrosting control method for the aforementioned air conditioner, comprising: after the air conditioner is turned on for heating and the compressor starts, acquiring the outdoor ambient temperature, the outdoor coil temperature, the compressor's operating time, and the outdoor relative humidity; determining the dew point temperature based on the outdoor ambient temperature, the outdoor relative humidity, and a preset mapping relationship, wherein the preset mapping relationship includes multiple sets of correspondences between outdoor ambient temperature, outdoor relative humidity, and dew point temperature; determining a target temperature difference based on the dew point temperature and the outdoor coil temperature; and determining the target temperature difference based on the compressor's operating time and the target temperature difference. The frost thickness of the air conditioner is described; based on the frost thickness, the outdoor ambient temperature, and the compressor's operating time, the air conditioner is controlled to enter a corresponding target defrosting mode, wherein the target defrosting mode includes a micro-frost defrosting mode, a hot air defrosting mode, and a reverse defrosting mode; wherein, after controlling the air conditioner to enter the micro-frost defrosting mode, the process includes: based on the target temperature range of the outdoor ambient temperature, controlling the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range, wherein different temperature ranges correspond to different micro-frost defrosting strategies, and under different micro-frost defrosting strategies, the conditions for triggering the compressor to reduce its frequency are different.

[0029] According to the defrosting control method of an air conditioner according to an embodiment of the present invention, after the air conditioner is turned on for heating and the compressor starts, the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity are acquired. The dew point temperature is determined based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship. Then, the target temperature difference is calculated based on the dew point temperature and the outdoor coil temperature, and integrated based on the compressor running time and the target temperature difference to calculate the frost thickness of the air conditioner. This allows for dynamic calculation of the frost thickness based on changes in the outdoor environment, improving the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner. After calculating the frost thickness, the air conditioner is controlled to enter one of three modes: micro-frost defrosting mode, hot gas defrosting mode, and reverse defrosting mode, thereby improving the accuracy of defrosting intervention and the reliability of the air conditioner. After the air conditioner enters the micro-frost defrosting mode, it executes a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature. This strategy employs a high-efficiency approach for rapid defrosting in high-temperature ranges and a conservative approach to prevent icing in low-temperature ranges. This ensures the efficiency and safety of micro-frost defrosting under various operating conditions, effectively avoiding incomplete defrosting or secondary icing caused by excessively low ambient temperatures. At the same time, it minimizes indoor temperature fluctuations, thereby improving the heating reliability and user comfort of the air conditioner in low-temperature and high-humidity environments.

[0030] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0031] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the refrigeration cycle system of an air conditioner according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the controller according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure of an air conditioner according to another embodiment of the present invention; Figure 4 This is a schematic diagram of the frosting process during heating operation according to an embodiment of the present invention; Figure 5 This is a schematic diagram of an outdoor heat exchange temperature difference curve according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the temperature change of the outdoor coil of an air conditioner according to an embodiment of the present invention; Figure 7 This is a schematic diagram of heat convection generated by an outdoor fan according to an embodiment of the present invention; Figure 8 This is a schematic diagram of the heat and mass transfer process that occurs when humid air passes over the surface of a heat exchanger according to an embodiment of the present invention. Figure 9 This is a schematic diagram of a humidity prediction model according to an embodiment of the present invention; Figure 10 This is a schematic diagram of the outdoor relative humidity update method when using hot air defrosting and micro-frost melting according to an embodiment of the present invention; Figure 11 This is a schematic diagram of the outdoor relative humidity update method when using reverse defrosting according to an embodiment of the present invention; Figure 12 This is a schematic diagram of the control logic for micro-frost defrosting in a low-efficiency temperature range according to an embodiment of the present invention; Figure 13 This is a schematic diagram of the control logic for micro-frost defrosting in a high-efficiency temperature range according to an embodiment of the present invention; Figure 14 This is a flowchart of a defrosting control method for an air conditioner according to an embodiment of the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] like Figure 1 As shown, one of the indoor heat exchangers and the other of the outdoor heat exchanger is a condenser, and the other is an evaporator. In this invention, the air conditioner performs a refrigeration cycle by using a compressor, a condenser, an expansion valve, an evaporator, and a four-way valve. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation, and supplies refrigerant to the conditioned and heat-exchanged air.

[0034] The compressor compresses the refrigerant gas, which is in a high-temperature, high-pressure state and enters through the return pipe, and then discharges the compressed refrigerant gas through the exhaust pipe. The discharged refrigerant gas flows into the condenser through the condenser inlet pipe. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0035] The indoor and outdoor heat exchangers function as either condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air conditioner functions as a heater in heating mode; when the indoor heat exchanger is used as an evaporator, the air conditioner functions as a cooler in cooling mode.

[0036] The expansion valve expands the high-temperature, high-pressure liquid refrigerant, which condenses in the condenser and is discharged through the condenser outlet pipe, into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the expansion valve and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves a cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cycle, the air conditioner regulates the temperature of the indoor space.

[0037] In the embodiments shown in this application, the air conditioner also includes a controller 71. The controller 71 is a device that can generate operation control signals according to instruction operation codes and timing signals to instruct the air conditioner to execute control commands. For example, in response to a power-on or power-off command issued by a user, the controller 71 can perform an operation related to the object selected by the power-on or power-off command.

[0038] This application embodiment also provides a hardware structure diagram of the controller 71, such as... Figure 2 As shown, the controller 71 includes a processor 83, and optionally, a memory 82 and a communication interface 84 connected to the processor 83. The processor 83, memory 82, and communication interface 84 are connected via a bus 81.

[0039] Processor 83 can be a central processing unit (CPU), a general-purpose processor (NP), a network processor (NP), a digital signal processor (DSP), a microprocessor (Microcontroller), a programmable logic device (PLD), or any combination thereof. Processor 83 can also be any other device with processing capabilities, such as a circuit, device, or software module. Processor 83 can also include multiple CPUs, and processor 83 can be a single-core processor. CPU) processor 83, or multi-core (multi) CPU) Processor 83. Here, processor 83 may refer to one or more devices, circuits, or processing cores used to process data (such as computer program instructions).

[0040] Memory 82 can be a read-only memory 82 (read ROM (Read-Only Memory) or other types of static storage devices capable of storing static information and instructions; random access memory (RAM) or other types of dynamic storage devices capable of storing information and instructions; or electrically erasable programmable read-only memory (EEPROM). EEPROM (Electronic EPROM) and Compact Disc Retrieval System (CD-ROM) are both memory-only systems. Only memory, CD The storage medium can be ROM or other optical disc storage, optical disk storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and accessible by a computer. This application embodiment does not impose any limitations on this. The memory 82 can exist independently or be integrated with the processor 83. The memory 82 may contain computer program code. The processor 83 is used to execute the computer program code stored in the memory 82, thereby implementing the air conditioner control method provided in this application embodiment.

[0041] The communication interface 84 can be used to communicate with other devices or communication networks (such as Ethernet, radio access network (RAN), wireless local area networks (WLAN), etc.). The communication interface 84 can be a module, circuit, transceiver, or any device capable of communication.

[0042] Bus 81 can be a peripheral component interconnect (PCI) bus 81 or an extended industry standard architecture (EISA) bus 81, etc. Bus 81 can be divided into address bus 81, data bus 81, control bus 81, etc.

[0043] The following is combined Figures 3-13 An air conditioner with multiple defrosting modes according to an embodiment of the present invention is described.

[0044] Figure 3 This is a schematic diagram of the structure of an air conditioner according to an embodiment of the present invention, as shown below. Figure 3 As shown, an air conditioner 10 includes: a refrigerant circulation loop, an outdoor ambient temperature sensor 16, and an outdoor coil temperature sensor 17.

[0045] The refrigerant circulation loop allows the refrigerant to circulate in a loop consisting of compressor 12, condenser, expansion valve 13, and evaporator. One of the condensers and the evaporator is an outdoor heat exchanger 14, and the other is an indoor heat exchanger 15. The outdoor ambient temperature sensor 16 is used to detect the outdoor ambient temperature. The outdoor coil temperature sensor 17 is used to detect the outdoor coil temperature.

[0046] Household air conditioners generally use reverse defrosting. Once defrosting conditions are met, they enter reverse defrosting mode, where the four-way valve switches to cooling (during defrosting, the outdoor fan stops, the expansion valve opens to a preset degree (this is not the case for capillary tube air conditioners), and the indoor fan stops after blowing away residual heat). The high-temperature, high-pressure gaseous refrigerant discharged from the compressor directly enters the outdoor heat exchanger. Therefore, reverse defrosting is highly efficient and quick. However, because the indoor temperature drops significantly during defrosting, it affects comfort.

[0047] There is a non-stop defrosting technology called hot gas defrosting. During defrosting, the four-way valve does not switch, the compressor does not stop, the outdoor motor stops, the indoor motor's speed is controlled by anti-cold air logic, and the expansion valve is fully open. The essence of hot gas defrosting is uninterrupted and continuous heating. Its advantages are small room temperature fluctuations, no impact noise from the four-way valve switching, and no refrigerant flow noise or thermal expansion and contraction noise during defrosting. Moreover, the room temperature will recover quickly after defrosting. However, even if the expansion valve is fully open, its small diameter will inevitably cause throttling. Therefore, the temperature of the refrigerant throttled by the expansion valve will be further reduced, thus significantly reducing defrosting efficiency. Therefore, hot gas defrosting has many limitations. Only a thin layer of frost can be defrosted cleanly. Once the frost layer is thick, the actual defrosting time is significantly longer than that of reverse defrosting. Moreover, because the outdoor expansion valve is fully open and the outdoor motor stops during hot gas defrosting, prolonged operation can easily lead to liquid return. The refrigerant entering the compressor will dilute the lubricating oil, causing poor compressor lubrication and wear, and creating a risk of liquid slugging.

[0048] The root cause of these defrosting technology bottlenecks is related to the physical mechanism of frost formation on outdoor air conditioning units. Specifically, frost formation on an outdoor air conditioning unit requires the simultaneous fulfillment of three key necessary conditions: first, a low-temperature surface, meaning the temperature of the heat exchanger fins and pipe walls must be below 0°C; second, the ambient air must contain water vapor (i.e., the air humidity is not zero); and most importantly, the fin surface temperature must be below the dew point temperature of the air. The dew point temperature is the temperature at which air is cooled to saturation (100% relative humidity) under constant pressure. This causes water vapor to condense, and because the surface temperature is simultaneously below the freezing point, the condensed water droplets freeze rapidly, thus distinguishing them from ordinary liquid condensate.

[0049] This process goes through four microscopic stages: When moist air comes into contact with the cold fins, the air layer close to the surface is cooled to saturation, and water vapor condenses into tiny supercooled droplets (the temperature is below 0°C but still in a liquid state); these unstable droplets then freeze on tiny protrusions, impurities, or dust on the fin surface, forming initial ice crystal nuclei; subsequently, subsequent water vapor molecules preferentially sublimate directly on these ice crystal nuclei (the gaseous state directly becomes solid) or attach and freeze on the supercooled droplets, causing ice crystals to grow along the fin surface and toward the air side; as time goes on, the ice crystals continue to accumulate and merge, the frost layer gradually thickens, and eventually may form "frost bridges" in the gaps between the fins, completely blocking the air passages and causing heat exchange failure.

[0050] The rate and morphology of frost formation are mainly constrained by three environmental factors: the relative humidity of outdoor air is the most critical factor. The higher the humidity, the greater the pressure difference between the water vapor partial pressure and the saturated vapor pressure of the ice surface, the stronger the mass transfer driving force, and the faster and more severe the frost formation. The lower the fin surface temperature (evaporation temperature), the greater the temperature difference with the air, the stronger the heat transfer driving force, and the easier it is for condensate to freeze, often forming a denser frost layer. The influence of outdoor air temperature is more complex. Although low temperature increases the heat exchange temperature difference, the saturated moisture content of the air is extremely low at extremely low temperatures, and the water vapor content is reduced, which may actually slow down the frost formation rate.

[0051] Table 1 shows the mapping relationship between outdoor ambient temperature, outdoor relative humidity, and dew point temperature.

[0052]

[0053] Table 1 Based on the defrosting principle and the data in Table 1, it can be seen that the higher the outdoor relative humidity, the higher the dew point temperature, and the greater the difference between the dew point temperature and the outdoor heat exchanger tube temperature (when it is less than 0℃), the easier it is for frost to form.

[0054] However, during defrosting, there are many different scenarios in the actual outdoor environment. For example, air temperature is categorized into low-temperature zones (frost begins to form below 6°C) and ultra-low-temperature zones (below -7°C), and humidity is categorized into high humidity, medium humidity, and low humidity. In high-humidity environments, outdoor heat exchangers are extremely prone to frost formation, and the frost formation is very rapid. In low-humidity environments, the evaporation temperature is below the dew point temperature, and outdoor heat exchangers are basically frost-free. Typical frost-prone temperature and humidity ranges include outdoor temperatures of -7°C to 5°C and relative humidity above 90%, while typical frost-resistant humidity ranges include -7°C to 5°C and relative humidity below 50%. Other scenarios include freezing rain, heavy snowfall where outdoor fans attract snowflakes onto the heat exchanger's outer surface, and drastic temperature drops.

[0055] When the outdoor ambient temperature is above 0℃, the defrosting frequency of micro-frost defrosting is higher than that of hot air defrosting and reverse defrosting. However, the indoor temperature drop is less significant with micro-frost defrosting and reverse defrosting, resulting in better overall heat exchange efficiency and performance. Therefore, it is crucial to select the most appropriate defrosting method based on environmental conditions and the degree of frost buildup on the outdoor heat exchanger. An inappropriate defrosting method may not only fail to deliver its advantages but could also produce the opposite effect, even impacting the reliability of the air conditioner.

[0056] Therefore, based on the advantages and disadvantages of micro-frost defrosting (only applicable to frost scenarios with outdoor temperatures above 0℃ and moderate humidity), hot air defrosting, and reverse defrosting, it is crucial to understand that micro-frost defrosting, in particular, has unique advantages, but its disadvantages are also very obvious. Therefore, accurately identifying the frost thickness and determining the appropriate time to initiate micro-frost defrosting is essential to providing users with a truly comfortable experience; otherwise, it may have the opposite effect.

[0057] In a specific embodiment, the outdoor ambient temperature and outdoor relative humidity are environmental parameters, while the outdoor coil temperature is determined by a combination of factors such as the size of the outdoor heat exchanger, the surface wind speed of the heat exchanger, the operating frequency of the compressor, and the throttling of the expansion valve.

[0058] Figure 4 This is a schematic diagram of the frosting process during heating operation according to an embodiment of the present invention, as shown below. Figure 4 As shown, in response to the above-mentioned problems, the air conditioner 10 provided in this embodiment of the invention first divides the frosting process of heating operation into the following steps before control: Figure 1 The three intervals shown are the frost-free or slightly frost zone, the thin frost zone, and the thick frost zone. The outdoor heat exchange temperature difference in the frost-free or slightly frost zone is defined as the standard heat exchange temperature difference ΔTout_st (outdoor ambient temperature Tout - outdoor coil temperature Te_st). The end of the thin frost zone is the appropriate time to initiate hot air defrosting, and its outdoor heat exchange temperature difference is the hot air defrosting temperature difference ΔTout_rq (outdoor ambient temperature Tout - outdoor coil temperature Te_rq). The end of the thick frost zone is the appropriate time to initiate reverse defrosting, and its outdoor heat exchange temperature difference is the reverse defrosting temperature difference ΔTout_nx (outdoor ambient temperature Tout - outdoor coil temperature Te_nx). Clearly, ΔTout_st < ΔTout_rq < ΔTout_nx. Specifically, the actual experimental results are from... Figure 4 It can also be seen that △Tout_rq is only 0.5℃~3℃ larger than △Tout_st.

[0059] As the frost layer on the outdoor heat exchanger thickens, its air resistance (thermal resistance) also increases. This is reflected in a gradual decrease in the outdoor coil temperature (i.e., evaporation temperature), a decline in heat exchange capacity, and a gradual increase in the outdoor heat exchange temperature difference (outdoor ambient temperature - outdoor coil temperature). Therefore, when the outdoor heat exchange temperature difference gradually increases, exceeds a preset threshold, and the outdoor coil temperature is below 0℃ (a necessary condition for frosting), the frost layer on the outdoor heat exchanger is judged to be either thin or thick. This judgment method requires a sensor accuracy of at least 0.5℃, typically using a sensor with 1℃ accuracy. For high humidity, the frosting rate of the outdoor heat exchanger is significantly faster than for moderate humidity, manifested as a pronounced increasing trend in the outdoor heat exchange temperature difference. Figure 5 As shown. Figure 4 The time spent in the frost-free zone, light frost zone, thin frost zone, and thick frost zone is very short when the humidity is high, and the outdoor heat exchange temperature difference is increasing rapidly, so it is not possible to enter the light frost zone for defrosting.

[0060] As mentioned earlier, under microfrost conditions, only a very thin layer of frost adheres to the surface of the outdoor heat exchanger, and its heat exchange capacity does not decrease or almost does not decrease. The outdoor heat exchange temperature difference can only be observed gradually and slightly increasing in a laboratory environment using high-precision thermocouples, or confirmed manually through video camera observation. Ordinary sensors with an accuracy of 0.5℃ or 1℃ cannot effectively detect such minute changes; higher-precision sensors (such as 0.1℃ or 0.2℃) are required for monitoring, but this increases costs significantly.

[0061] To solve the above problems, the air conditioner 10 provided in this embodiment of the invention controls the air conditioner 10 according to the following steps: The controller 71 is configured to: after the air conditioner 10 starts heating operation and the compressor starts, acquire the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity; determine the dew point temperature based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship, wherein the preset mapping relationship includes multiple sets of correspondences between outdoor ambient temperature, outdoor relative humidity, and dew point temperature; determine the target temperature difference based on the dew point temperature and the outdoor coil temperature; determine the frost thickness of the air conditioner based on the compressor running time and the target temperature difference; and control the air conditioner to enter the corresponding target defrosting mode based on the frost thickness, outdoor ambient temperature, and compressor running time, wherein the target defrosting mode includes a micro-frost defrosting mode, a hot gas defrosting mode, and a reverse defrosting mode.

[0062] After the air conditioner 10 is controlled to enter the defrosting mode, the controller 71 is configured to: control the air conditioner 10 to execute the defrosting strategy corresponding to the target temperature range based on the target temperature range of the outdoor ambient temperature. Different temperature ranges correspond to different defrosting strategies, and the conditions for triggering compressor frequency reduction are different under different defrosting strategies.

[0063] In this embodiment, after the air conditioner 10 is turned on for heating and the compressor is started, the outdoor ambient temperature is obtained from the outdoor ambient temperature sensor 16, the outdoor coil temperature is obtained from the outdoor coil temperature sensor 17, and the continuous running time of the compressor and the outdoor relative humidity are also obtained.

[0064] Furthermore, the dew point temperature is determined based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship. For example, referring to Table 1, when the outdoor ambient temperature is 6℃ and the outdoor relative humidity is 75%, the target temperature difference is then calculated based on the dew point temperature and the outdoor coil temperature. This difference is then integrated based on the compressor's operating time and the target temperature difference to calculate the frost thickness of the air conditioner 10. This allows for dynamic calculation of the frost thickness based on changes in the outdoor environment, thereby improving the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner 10.

[0065] Furthermore, after calculating the frost thickness, the air conditioner 10 is controlled to enter the corresponding target defrosting mode based on the outdoor ambient temperature, that is, the air conditioner 10 is controlled to enter one of the following modes: micro-frost defrosting mode, hot air defrosting mode, and reverse defrosting mode.

[0066] refer to Figure 6 It is known that even if the microfrost is accurately identified and the outdoor ambient temperature is greater than 0℃, and the microfrost defrosting mode is entered, there may still be problems such as excessively long defrosting time and low defrosting efficiency during the microfrost defrosting process.

[0067] In a specific embodiment, based on the principle of micro-frost defrosting, it is understood that a low-quality heat source with an outdoor ambient temperature greater than 0°C is mainly utilized. Forced airflow generated by the outdoor fan's high-speed operation (especially at increased speed) forces convective heat exchange with the frost layer on the heat exchanger surface. This airflow simultaneously achieves a dual effect: on the one hand, the high-speed airflow above 0°C rapidly melts the micro-frost; on the other hand, using the airflow's kinetic energy, it mechanically peels away water droplets adhering to the fin surface, allowing the melted water to flow down quickly (a small portion will also evaporate), reducing liquid retention. Figure 7 As shown in the diagram, it is clear that the higher the outdoor ambient temperature, the higher the efficiency of micro-frost defrosting. Therefore, when the outdoor ambient temperature is within the low-efficiency temperature range for micro-frost defrosting, the defrosting efficiency will be significantly reduced due to the influence of the outdoor environment. This necessitates increasing the defrosting time to compensate for the insufficient efficiency, resulting in large fluctuations in the indoor ambient temperature. Consequently, the most important advantage of micro-frost defrosting is lost. Since the micro-frost defrosting process requires the use of an outdoor fan to achieve forced convection heat exchange between the outdoor heat source and the frost layer on the heat exchanger surface, and the high-speed operation of the outdoor fan to dry the surface water droplets, when the outdoor ambient temperature is close to 0℃, which is also close to the freezing point of water, incomplete defrosting can easily occur during the micro-frost defrosting process, leading to icing.

[0068] Hot gas defrosting is a defrosting method with higher efficiency than micro-frost defrosting. It relies entirely on the sensible heat of the high-temperature refrigerant for defrosting, eliminating the need for forced convection from an outdoor fan. Therefore, defrosting can still occur even when the outdoor ambient temperature is below 0°C, and it allows for a thin layer of frost to form on the outdoor heat exchanger. However, because the frost is thicker, the defrosting time is longer, and the indoor temperature fluctuations are greater than with micro-frost defrosting. Furthermore, because the compressor needs to operate at high frequency to deliver the high-temperature, high-pressure refrigerant to the outdoor heat exchanger, its energy efficiency is also very low during defrosting.

[0069] Therefore, based on the advantages of hot air defrosting and micro-frost defrosting, and improving upon their disadvantages, the air conditioner 10 can be controlled to execute a micro-frost defrosting strategy corresponding to the target temperature range of the outdoor ambient temperature. Different temperature ranges correspond to different micro-frost defrosting strategies, and the conditions for triggering compressor frequency reduction differ under different micro-frost defrosting strategies. Through this zoned control strategy, the system can dynamically adjust the micro-frost defrosting operation logic according to the outdoor ambient temperature: a high-efficiency strategy is used for rapid defrosting in high-temperature ranges, and a conservative strategy is used to prevent icing in low-temperature ranges. This ensures the efficiency and safety of micro-frost defrosting under various operating conditions, effectively avoiding incomplete defrosting or secondary icing caused by excessively low ambient temperatures. Simultaneously, it minimizes indoor temperature fluctuations, significantly improving the heating reliability and user comfort of the air conditioner 10 in low-temperature and high-humidity environments.

[0070] In one embodiment of the present invention, when determining the frost thickness of the air conditioner based on the compressor's operating time and the target temperature difference, the controller 71 is configured to: determine the frost thickness of the air conditioner 10 according to the compressor's operating time and the target temperature difference, and according to a preset algorithm, wherein the frost thickness is positively correlated with the target temperature difference and the compressor's operating time; the preset algorithm includes: Where H represents the frost thickness, t_js represents the compressor running time, △TL represents the target temperature difference, and k is a preset constant.

[0071] In this embodiment, for example, the frost thickness is denoted as H, the target temperature difference as ΔTL, and the compressor running time as t_js. Referring to Table 1, when the outdoor ambient temperature is 2℃, assuming the outdoor coil temperature is -3℃, and the outdoor relative humidity is 70%, the corresponding dew point temperature is -3.7℃. At this time, the outdoor heat exchanger will definitely not frost. When the outdoor relative humidity is 85%, the corresponding dew point temperature is -0.8℃, and the outdoor heat exchanger will frost. From the principle of frost formation, it can be seen that the greater the difference between the dew point temperature and the outdoor coil temperature (i.e., the target temperature difference), the easier it is for frost to form. Therefore, the frost thickness H is positively correlated with the target temperature difference ΔTL and the compressor running time t_js. The preset algorithm is as follows: k is a preset constant, which is related to the specific product platform; for example, k = 2. The frost thickness here is actually difficult to measure with actual dimensions, representing a degree of frost thickness, and is dimensionless. The compressor's running time is the cumulative running time of the compressor.

[0072] For example, if the compressor runs for 10 minutes and the calculated target temperature difference ΔTL is 2.3℃, then the frost thickness in the first 10 minutes is... When the compressor has been running for 20 minutes, the target temperature difference ΔTL = 2.3℃, so the frost thickness in the first 20 minutes is... Therefore, the frost thickness H can be dynamically calculated based on changes in the outdoor environment, which improves the accuracy of the frost thickness H calculation while reducing the hardware cost of the air conditioner 10.

[0073] In one embodiment of the present invention, the air conditioner 10 is controlled to enter a corresponding target defrosting mode based on the frost thickness, outdoor ambient temperature, and compressor running time. The controller 71 is configured to: acquire the continuous running time of the air conditioner 10 in the micro-frost defrosting mode, the cumulative running time in the hot air defrosting mode, and the cumulative running time in the reverse defrosting mode; when the frost thickness is greater than or equal to a first frost thickness threshold and less than a second frost thickness threshold, and the outdoor ambient temperature is greater than a first outdoor ambient temperature threshold and the first outdoor ambient temperature threshold is greater than a first preset temperature threshold, and the continuous running time of the micro-frost defrosting mode is greater than or equal to the compressor running time, the air conditioner 10 is controlled to enter the micro-frost defrosting mode; when the frost thickness is greater than or equal to a second frost thickness threshold and less than a third frost thickness threshold, and the outdoor ambient temperature is greater than or equal to a second outdoor ambient temperature threshold, and the cumulative running time of the hot air defrosting mode is greater than or equal to the compressor running time, the air conditioner 10 is controlled to enter the hot air defrosting mode; when the frost thickness is greater than or equal to a third frost thickness threshold, the air conditioner 10 is controlled to enter the reverse defrosting mode.

[0074] For example, the first frost thickness threshold is denoted as H1 and H1>0, the second frost thickness threshold is denoted as H2, the third frost thickness threshold is denoted as H3, the outdoor ambient temperature is denoted as Tout, the first outdoor ambient temperature threshold is denoted as T1, the first preset temperature threshold is 0℃, the preset minimum continuous running time is denoted as t_min, and the second outdoor ambient temperature threshold is denoted as T2.

[0075] In this embodiment, the entry conditions for both the micro-frost defrosting mode and the hot gas defrosting mode need to meet the compressor's preset minimum continuous operating time t_min. Taking micro-frost defrosting as an example: Under the same outdoor ambient temperature (e.g., Tout = 2℃ > 0℃) but different outdoor relative humidities (Rh_1 = 100%, Rh_2 = 70%), the rate of frost thickness increase differs significantly (reflected in the target temperature difference △TL_1 (corresponding to dew point temperature TL_1 = 2.1℃) being greater than the target temperature difference △TL_2 (corresponding to dew point temperature TL_2 = 3.7℃)). This means that within the same frost thickness threshold range (H1 ≤ H < H2), the time required to reach the defrosting threshold under high humidity conditions (condition 1) is much shorter than under low humidity conditions (condition 2), which easily leads to frequent defrosting. Frequent micro-frost defrosting operations may result in higher cumulative energy consumption than a single hot gas defrosting operation. Therefore, to avoid excessively frequent micro-frost defrosting, an additional minimum entry time condition for micro-frost defrosting needs to be set. Similarly, for determining whether to initiate hot defrosting for thin frost, a minimum time condition should be introduced to prevent the cumulative energy consumption of multiple hot defrosting operations from exceeding that of a single, more thorough reverse defrosting operation. Reverse defrosting, on the other hand, is designed to handle thicker frost layers and its activation is typically based on a higher frost layer threshold, thus requiring no additional time limit.

[0076] Therefore, in a specific embodiment, when the air conditioner 10 is in heating mode, the compressor starts for the first time and the continuous running time t_run1 of the air conditioner 10 in the micro-frost defrosting mode, the cumulative running time t_run2 of the air conditioner 10 in the hot gas defrosting mode, and the cumulative running time t_run3 of the air conditioner 10 in the reverse defrosting mode are timed respectively.

[0077] After the compressor starts, the outdoor ambient temperature is recorded. When the frost thickness H is greater than or equal to the first frost thickness threshold H1 and less than the second frost thickness threshold H2, and the outdoor ambient temperature Tout is greater than the first outdoor ambient temperature threshold T1, and the first outdoor ambient temperature threshold T1 is greater than the first preset temperature threshold 0℃, and the continuous running time t_run1 of the micro-frost defrosting mode is greater than or equal to the compressor's preset minimum continuous running time t_min, that is, H1≤H0℃, t_run1≥t_min, the air conditioner 10 is controlled to enter the micro-frost defrosting mode.

[0078] When the frost thickness H is greater than or equal to the second frost thickness threshold H2 and less than the third frost thickness threshold H3, and the outdoor ambient temperature Tout is greater than or equal to the second outdoor ambient temperature threshold T2, and the cumulative running time t_run2 of the hot air defrost mode is greater than or equal to the compressor's preset minimum continuous running time t_min (i.e., H2≤H<H3, T2≤Tout, t_run2≥t_min), the air conditioner 10 is controlled to enter the hot air defrost mode. Furthermore, when the frost thickness H is between 0 and the first frost thickness threshold H1 (i.e., 0≤H

[0079] When the frost thickness H is greater than or equal to the third frost thickness threshold H3, i.e., H≥H3, the air conditioner 10 is controlled to enter the reverse defrost mode. Thus, by classifying the frost thickness H and the outdoor ambient temperature Tout, and combining this with the corresponding defrost mode's operating time constraints, precise defrost mode matching is achieved for different frost levels and environmental conditions: a light frost defrosting mode is used to avoid over-defrosting during the light frost stage; a hot air defrosting mode is used to balance defrosting efficiency and heating continuity during the medium frost stage; and a reverse defrost mode is used to ensure thorough defrosting during the heavy frost stage. This improves the targeting and energy efficiency of the defrosting process, reduces unnecessary mode switching, and ensures the heating stability and operational reliability of the air conditioner 10.

[0080] In one embodiment of the present invention, when acquiring outdoor relative humidity, the controller 71 is configured to: when the air conditioner 10 includes an outdoor humidity sensor and the outdoor humidity sensor is working properly, use the humidity value detected by the outdoor humidity sensor as the outdoor relative humidity; or, when the air conditioner 10 does not include an outdoor humidity sensor or the air conditioner 10 includes an outdoor humidity sensor but the outdoor humidity sensor is not working properly, use the humidity value predicted based on the outdoor ambient temperature, the operating parameters of the air conditioner 10 and the pre-trained humidity prediction model as the outdoor relative humidity.

[0081] In this embodiment, when the air conditioner 10 is equipped with an outdoor humidity sensor and the outdoor humidity sensor is functioning normally, the humidity value detected by the outdoor humidity sensor is directly used as the outdoor relative humidity. For example, if the outdoor humidity sensor detects a current humidity value of 70%, the outdoor relative humidity is directly determined to be 70%. By directly using the measured data from a high-precision humidity sensor as the control basis, the accuracy and real-time nature of humidity acquisition can be ensured, providing reliable data support for the subsequent start / stop determination of the micro-frost defrosting mode, thereby improving the adaptability of the air conditioner 10 in different environments and the accuracy of defrosting control.

[0082] ​When the air conditioner 10 is not equipped with an outdoor humidity sensor, or when the air conditioner 10 is equipped with an outdoor humidity sensor but the outdoor humidity sensor is faulty and cannot work properly, the outdoor relative humidity cannot be directly obtained. In this case, virtual humidity sensor technology is used to predict the outdoor relative humidity.

[0083] Specifically, the virtual humidity sensor technology can use data-driven neural network prediction to realize outdoor relative humidity, solving the problem that the air conditioner 10 cannot obtain weather parameters because it is not equipped with an outdoor humidity sensor or is not connected to the network (in fact, even if it is connected to the network, the relative humidity in the weather forecast is very different from the relative humidity around the air conditioner 10 currently in operation, resulting in a large prediction deviation in the degree of frost), or cannot accurately obtain the humidity near the outdoor unit. By detecting the outdoor ambient temperature and combining it with the predicted outdoor relative humidity, the outdoor ambient dew point temperature can be calculated, thereby realizing accurate prediction of the defrosting mode and precise control of the timing of defrosting entry and exit.

[0084] Compared to physical humidity sensors, virtual humidity sensors offer lower cost, stronger environmental resistance, faster response to different temperatures, and higher stability even after long-term exposure to indoor and outdoor environments, while maintaining comparable accuracy. Therefore, in enthalpy difference testing laboratories, the wet-bulb method is typically used, employing wet-bulb temperature to indirectly detect humidity, replacing the use of an outdoor humidity sensor. The feasibility of using wet-bulb temperature to indirectly test humidity demonstrates a strong coupling relationship between humidity and temperature. Specifically, refer to... Figure 8 This diagram illustrates the heat and mass transfer process that occurs when humid air passes over the surface of a heat exchanger. When humid air passes through the evaporator (or outdoor heat exchanger during heating operation) and is cooled and dehumidified, heat and mass transfer occur simultaneously on the evaporator surface, exhibiting a high degree of coupling. By calculating the heat and mass transfer occurring at the evaporator surface, the change in air humidity as the air passes through the evaporator can be assessed. This means that the inlet air humidity, i.e., the outdoor relative humidity, can be determined by the conservation of mass, moisture, and energy during the heat exchange process between the humid air and the evaporator.

[0085] Table 2 is a table analyzing the key influencing parameters related to the conservation of mass and energy.

[0086]

[0087] Table 2 Where m represents air mass flow rate; m w The q represents the mass flow rate of the condensed water; d represents the moisture content; h represents the enthalpy of the air; 1 represents the inlet state, 2 represents the outlet state; t Indicates heat exchange; m a1 Indicates inlet air mass flow rate; m a2The table shows the mass flow rate of the air at the outlet; d1 represents the moisture content at the inlet; d2 represents the moisture content at the outlet; h1 represents the enthalpy of the air at the inlet; and h2 represents the enthalpy of the air at the outlet.

[0088] During heating operation, the outdoor side undergoes a process of cooling and dehumidifying the air, resulting in near-saturation of the outlet air (outdoor relative humidity approximately 95%). If frost has formed, uneven airflow and frost blockage may cause localized unsaturation (outdoor relative humidity approximately 85-90%), but the overall air still meets the "near-saturation" characteristic. Since this technology primarily predicts the outdoor relative humidity before frost formation, the dry-bulb temperature at the outlet is approximately equal to the wet-bulb temperature. To simplify and accelerate the complex derivation process, this technology employs a data-driven artificial neural network to construct a humidity prediction model, effectively learning the coupling relationships between various parameters through multi-layer nonlinear transformations. Figure 9 As shown, by using the outdoor ambient temperature and air conditioner operating parameters as inputs to the humidity prediction model, the outdoor relative humidity can be output. These operating parameters include, but are not limited to, the inlet dry-bulb temperature (i.e., the outdoor ambient temperature), the outlet dry-bulb temperature (which can be replaced by the outdoor evaporation temperature), the outdoor fan speed, and the compressor operating frequency, thereby achieving accurate prediction of ambient humidity (i.e., outdoor relative humidity).

[0089] In one embodiment of the present invention, when the humidity value predicted based on the outdoor ambient temperature, the operating parameters of the air conditioner 10, and a pre-trained humidity prediction model is used as the outdoor relative humidity, the controller 71 is configured to update the outdoor relative humidity according to preset update conditions; wherein, the preset update conditions include: when the compressor's operating time is greater than or equal to a first preset operating time, acquiring the compressor operating frequency change value and the indoor heat exchange temperature difference every second preset operating time, wherein the indoor heat exchange temperature difference is determined based on the difference between the outdoor ambient temperature and the outdoor coil temperature; when the compressor operating frequency change value is less than or equal to a preset frequency change value, and the indoor heat exchange temperature difference is less than a preset heat exchange temperature difference threshold, acquiring the compressor operating frequency change value and the indoor heat exchange temperature difference every second preset operating time. The outdoor relative humidity is updated once; or, the heating operation time of the air conditioner 10 in heating operation mode is obtained, and the outdoor relative humidity is updated every fourth preset operation time when the heating operation time is greater than or equal to the third preset operation time; or, when the air conditioner 10 is in a stopped state or enters the corresponding target defrost mode, the update of the outdoor relative humidity is paused; when updating the outdoor relative humidity according to the preset update conditions, the controller 71 is also configured to: when the air conditioner 10 is in an operation state that does not meet the preset update conditions, maintain the outdoor relative humidity at the humidity value determined when the preset update conditions were met last time, until the operation state of the air conditioner 10 meets the preset update conditions again, and then redetermine and update the outdoor relative humidity.

[0090] In this embodiment, the outdoor unit of the air conditioner is typically not equipped with a humidity sensor. However, a virtual humidity sensor can be constructed using digital twin technology, based on the existing temperature sensor on the outdoor unit and combined with heat exchange data between the air conditioner 10 and the outdoor environment during operation, to detect the outdoor relative humidity. Compared to the indoor cooling and dehumidification process, the outdoor relative humidity is usually relatively stable, meaning that the outdoor ambient temperature and humidity remain essentially unchanged or fluctuate very little over a longer period. Therefore, when the air conditioner 10 is operating in a steady state, the virtual humidity prediction value is relatively accurate, with a deviation controllable within 3%.

[0091] However, when the air conditioner 10 is in a non-steady-state operation phase, such as when the compressor starts and restarts, or when a sudden change in operating frequency causes refrigerant migration, the calculated virtual humidity value will fluctuate. This fluctuation reflects changes in the system's own state, rather than changes in the actual ambient humidity. Therefore, the reliability of the predicted outdoor relative humidity decreases and the deviation increases significantly. In addition, frost formation also affects prediction accuracy: the effect of light frost on wind resistance is negligible, but thin and thick frost will increase wind resistance and reduce airflow, thereby undermining the basic assumptions of the calculation model and further increasing the prediction deviation.

[0092] Therefore, to ensure the reliability of outdoor relative humidity, the outdoor relative humidity will be updated according to preset update conditions.

[0093] For example, the compressor start-up time is denoted as t1, the first preset running time as t_Vrun1, the second preset running time as t_V1, the compressor operating frequency change value as ΔF, the outdoor heat exchange temperature difference as ΔTout(n), the preset frequency change value as ΔF1 (e.g., 5Hz), the preset heat exchange temperature difference threshold as ΔTout_st, the heating running time as t2, the third preset running time as t_Vrun2 (e.g., 20min), and the fourth preset running time as t_V2. The third preset running time t_Vrun2 is greater than the first preset running time t_Vrun1.

[0094] Specifically, the first preset update condition is as follows: Obtain the compressor's start-up time. When the compressor's start-up time t1 is greater than or equal to the first preset running time t_Vrun1 (e.g., 5 minutes), and every second preset running time t_V1 (e.g., 5 minutes), obtain the compressor's operating frequency change value ΔF and the outdoor heat exchange temperature difference ΔTout(n). If the compressor's operating frequency change value ΔF1 obtained every 5 minutes is less than or equal to the preset frequency change value ΔF1, and the outdoor heat exchange temperature difference ΔTout(n) is less than the preset heat exchange temperature difference threshold ΔTout_st, i.e., t1 ≥ t_Vrun1, ΔF ≤ ΔF1, and ΔTout(n) < ΔTout_st, then update the outdoor relative humidity every second preset running time t_V1 (i.e., 5 minutes). Here, the preset heat exchange temperature difference threshold ΔTout_st is the standard heat exchange temperature difference, i.e., the outdoor heat exchange temperature difference in the frost-free or slightly frost-free zone. The outdoor heat exchange temperature difference is the difference between the outdoor ambient temperature and the outdoor coil temperature.

[0095] For example, refer to Figure 10 and Figure 11 During hot gas defrosting, micro-frost defrosting, or reverse defrosting, when the compressor start-up time t1 is greater than or equal to the first preset running time t_Vrun1, if the compressor operating frequency change value ΔF1 obtained every 5 minutes is less than or equal to the preset frequency change value ΔF1, and the outdoor heat exchange temperature difference ΔTout(n) obtained every 5 minutes is less than the preset heat exchange temperature difference threshold ΔTout_st, the system enters a stable operating state and updates the outdoor relative humidity (denoted as Rh_V) every t_V1 (i.e., every 5 minutes). 1(n)); During the defrosting period and the defrosting exit time t_v, the Rh_V1(n) updated at the previous moment remains unchanged, and then enters a stable operating state. Similarly, the outdoor relative humidity is updated every t_V1 (i.e., 5 min) (denoted as Rh_V2(n)); Similarly, during the defrosting period and the defrosting exit time t_v, the Rh_V2(n) updated at the previous moment remains unchanged, and then enters a stable operating state. Similarly, the outdoor relative humidity is updated every t_V1 (i.e., 5 min) (denoted as Rh_V3(n)).

[0096] Alternatively, a second preset update condition can be used: When the air conditioner 10 is in normal heating operation, the heating operation time t2 of the air conditioner 10 is obtained. If the heating operation time t2 is greater than or equal to the third preset operation time t_Vrun2 (i.e., t2 ≥ t_Vrun2), the controller 71 does not need to verify condition one again and directly updates the outdoor relative humidity with the fourth preset operation time t_V2 (e.g., 5 minutes) as the cycle. Furthermore, if the air conditioner 10 enters defrost mode before the heating operation time t2 reaches the third preset operation time t_Vrun2, the third preset operation time t_Vrun2 is recalculated after the air conditioner 10 exits defrost mode to ensure the accuracy of the outdoor relative humidity update.

[0097] Alternatively, a third preset update condition can be implemented: when the air conditioner 10 is in a stopped state or enters the corresponding target defrost mode, the update of outdoor relative humidity is paused. Through the collaborative judgment mechanism of the first and second preset update conditions, the system stability can be rigorously verified during the initial operation of the air conditioner (within t_Vrun1 after startup) and when the operating frequency fluctuates significantly, avoiding excessive deviations in the predicted outdoor relative humidity under unsteady conditions. After the system has been running stably for a long time (reaching t_Vrun2), the verification process is simplified, and the outdoor relative humidity is updated directly at a fixed cycle, ensuring both prediction accuracy and computational efficiency. Simultaneously, pausing updates during non-heating conditions such as shutdown or defrost further avoids the generation of invalid or erroneous data, thereby ensuring the reliability and accuracy of the outdoor relative humidity data and providing precise environmental parameter support for subsequent frost prediction and defrost control.

[0098] Furthermore, during the process of updating the outdoor relative humidity according to the preset update conditions, the controller 71 will also execute an outdoor relative humidity holding strategy: when the air conditioner 10 is in an operating state that does not meet the aforementioned preset update conditions, the controller 71 will not recalculate the outdoor relative humidity, but will hold the outdoor relative humidity at the humidity value determined when the preset update conditions were met last time; this holding state will continue until the operating state of the air conditioner 10 meets any of the preset update conditions again, at which point the controller 71 will restart the calculation program to determine and update the outdoor relative humidity, thereby avoiding erroneous humidity data caused by the failure of the humidity prediction model during the non-steady-state operation of the air conditioner 10, preventing control deviations such as false defrosting and frequent defrosting caused by abnormal fluctuations in humidity data, ensuring the continuity and reliability of outdoor relative humidity data, and providing stable environmental parameter support for the precise defrosting control and efficient heating operation of the air conditioner 10.

[0099] In an embodiment of the present invention, the controller 71 is further configured to: if the compressor is started for the first time and the first startup running time of the compressor is less than the fifth preset running time, and / or when the air conditioner 10 enters the corresponding target defrosting mode, pause predicting the outdoor relative humidity, and determine the dew point temperature based on the outdoor relative humidity obtained from the last prediction before the pause; when the compressor restarts after meeting the shutdown condition and the shutdown time of the compressor is less than the sixth preset running time, and the running time after the compressor restarts is less than the fifth preset running time, determine the dew point temperature based on the outdoor relative humidity before the compressor shuts down, where the shutdown condition includes compressor failure or the compressor reaching the set temperature; if the shutdown time of the compressor is greater than or equal to the sixth preset running time, the current startup of the compressor is regarded as the first startup running, and the steps for the compressor to be started for the first time are executed.

[0100] In the embodiment, for example, the first startup running time is denoted as t3, the fifth preset running time is denoted as t_Vrun3 (such as 5 min), and the sixth preset running time is denoted as t_Vrun4.

[0101] To ensure the reliability of the outdoor relative humidity in the non-steady state stage, it is also necessary to process it according to the virtual humidity value-taking principle.

[0102] Specifically, the first virtual humidity value-taking principle: Determine whether the compressor is started for the first time. If the compressor is started for the first time and the first startup running time t3 of the compressor is less than the fifth preset running time t_Vrun3, that is, t3 < t_Vrun3, and / or the air conditioner 10 enters one of the micro-frost melting defrosting mode, hot gas defrosting mode or reverse defrosting mode, that is, the air conditioner 10 is in the defrosting period, the prediction of the outdoor relative humidity will be paused. During this pause period and the subsequent calculation of the frost thickness H, the controller 71 will determine the dew point temperature based on the outdoor relative humidity obtained from the last valid prediction before the pause prediction (for the first startup stage, it is the virtual humidity value calculated for the first time), and then calculate the frost thickness H according to the dew point temperature. Thus, the continuity and accuracy of the frost thickness calculation in the non-steady state operation stage of the system are ensured.

[0103] Among them, the outdoor relative humidity obtained from the last prediction before the pause prediction refers to the numerical value of the outdoor relative humidity that was successfully calculated and confirmed to be valid when meeting the update condition and was retained in the system memory at the moment when the air conditioner 10 triggers the "pause prediction" logic due to the instability in the initial stage of the first startup, entering the defrosting mode or other non-steady state working conditions; this numerical value is used as the reference environmental parameter of the system in the non-steady state stage, and is locked during the pause period and used to replace the real-time humidity value for the calculation of the dew point temperature and the frost thickness, so as to ensure that the air conditioner control logic can still make continuous and stable operation judgments based on reliable historical data during the transition stage when the virtual sensor cannot work accurately.

[0104] Virtual humidity value taking principle two: When the compressor restarts after stopping due to a fault or reaching the set temperature, and the compressor's shutdown time is less than the sixth preset running time t_Vrun4 (e.g., 60 minutes), the outdoor relative humidity before the compressor stopped will be used to calculate the dew point temperature within the period when the compressor restarts and runs for less than the fifth preset running time t_Vrun3, so as to ensure the accuracy and continuity of the dew point temperature calculation in the non-steady-state operation phase at the beginning of the compressor restart.

[0105] Virtual humidity value taking principle three: If the compressor downtime is greater than or equal to the sixth preset running time t_Vrun4 (e.g., 60min), it indicates that the compressor downtime is relatively long and the outdoor relative humidity may have changed significantly. At this time, the controller 71 will execute the processing logic of the compressor's first start, that is, suspend the prediction update of the outdoor relative humidity, and use the virtual humidity value obtained from the first calculation or the last valid value before the suspension in subsequent calculations to ensure the reliability of the humidity data.

[0106] Following the aforementioned principles for virtual humidity measurement, the dew point temperature is determined to perform defrosting judgment. When defrosting ends or the compressor stops, the timer will automatically reset to zero and restart from the next compressor start time. It is worth noting that the humidity prediction deviation of the air conditioner 10 during stable operation is approximately 2%, while the deviation can reach 5% and fluctuate during non-steady-state operation. Taking a predicted relative humidity of 85% as an example, the actual value range during stable operation is 83.3% to 86.7%, while the actual value range during non-steady-state operation expands to 80% to 89%. Given the volatility and large error of non-steady-state data, selecting the predicted humidity value during the stable phase as the calculation benchmark can significantly improve the accuracy of defrosting judgment.

[0107] In one embodiment of the present invention, the air conditioner 10 further includes: an indoor coil temperature sensor (not shown in the figure), an indoor fan (not shown in the figure), an outdoor fan (not shown in the figure), and a four-way valve 18, for detecting the indoor coil temperature; the indoor fan is used to drive indoor air through an indoor heat exchanger by rotation, so that the indoor heat exchanger exchanges heat with the indoor air; the outdoor fan is used to drive outdoor air through an outdoor heat exchanger by rotation, so that the outdoor air exchanges heat with the outdoor heat exchanger through the temperature of the air, and defrosts the outdoor heat exchanger; the four-way valve 18 is used to switch the flow direction of the refrigerant discharged from the compressor.

[0108] When controlling the air conditioner 10 to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the controller 71 is configured to: control the air conditioner 10 to execute a first micro-frost defrosting strategy when the outdoor ambient temperature is greater than a second preset temperature threshold and less than or equal to a third preset temperature threshold; when controlling the air conditioner 10 to execute the first micro-frost defrosting strategy, the controller 71 is configured to: control the air conditioner 10 to enter a first defrosting stage, and during the first defrosting stage, control the indoor fan to reduce its speed from the current speed to the target speed corresponding to the current micro-frost defrosting strategy, control the four-way valve to maintain its current reversing state, control the compressor to maintain its current operating frequency, control the expansion valve to adjust its opening to a preset maximum opening, and control the outdoor fan to stop operating; acquire the first operating time, the first indoor coil temperature, and the first outdoor coil temperature of the air conditioner executing the first defrosting stage; and based on the first indoor coil temperature, the first outdoor coil temperature, and the first operating time... The system determines whether the air conditioner meets the first preset condition. If so, it controls the air conditioner 10 to exit the first defrosting stage and enter the second defrosting stage. The first preset condition includes one of the following: the first running time reaches the first preset maximum running time; the first indoor coil temperature is less than or equal to the preset minimum indoor coil temperature threshold, and the first outdoor coil temperature is greater than or equal to the first preset outdoor coil temperature threshold, and the first outdoor coil temperature is less than or equal to the second preset outdoor coil temperature threshold. After entering the second defrosting stage, the controller 71 is configured to: control the compressor to reduce its frequency to the first target operating frequency according to the first preset frequency reduction rate; control the indoor fan to maintain the target speed corresponding to the current micro-frost defrosting strategy; control the opening of the expansion valve to maintain the preset maximum opening; control the four-way valve to maintain the current reversing state; and control the outdoor fan to operate at the heating operating speed or increase the first preset speed above the heating operating speed. The first target operating frequency is greater than or equal to the preset minimum operating frequency.

[0109] In the embodiment, for example, the outdoor ambient temperature is denoted as Tout, the second preset temperature threshold is denoted as T1, and the third preset temperature threshold is denoted as Tout_m, and the second preset temperature threshold T1 is, for example, 0°C, and the third preset temperature threshold Tout_m does not exceed 7°C.

[0110] In an embodiment, for example, the 0~7℃ temperature range where frosting is likely to occur can be divided into a low-efficiency temperature range for micro-frost melting and a high-efficiency temperature range for micro-frost melting, namely T1~Tout_m and Tout_m~7℃.

[0111] Specifically, when the outdoor ambient temperature Tout is between 0 and Tout_m, it falls within the low-efficiency temperature range for defrosting under slight frost. Within this range (0 < Tout ≤ Tout_m), the outdoor ambient temperature is relatively low. Although the outdoor ambient temperature is still higher than the frost temperature, and the outdoor fan can directly defrost the refrigerant, the operation of the outdoor fan also intensifies the heat exchange between the high-temperature refrigerant inside the heat exchanger and the outdoor environment, resulting in heat loss from the high-temperature refrigerant.

[0112] Further, for example, the first indoor coil temperature is denoted as Ti1, the preset minimum indoor coil temperature threshold is denoted as Ti_min, the first outdoor coil temperature is denoted as Te1, the first preset outdoor coil temperature threshold is, for example, -0.5℃, and the second preset outdoor coil temperature threshold is, for example, 0℃.

[0113] like Figure 12 As shown, the first defrosting stage is hot gas defrosting. The indoor fan speed is reduced from the current speed to the target speed corresponding to the current micro-frost defrosting strategy, that is, the indoor fan speed is reduced from the set speed to low speed to increase the refrigerant temperature; the four-way valve 18 is controlled to maintain the current reversing state, the compressor is controlled to maintain the current operating frequency, that is, to maintain the free frequency (e.g., to maintain 65Hz); the opening of the expansion valve is controlled to adjust to the preset maximum opening (e.g., 500 steps), that is, to adjust from the free opening to 500 steps; and the outdoor fan is controlled to stop running, thereby reducing the heat exchange between the refrigerant and the outdoor environment, so that the sensible heat of the high-temperature refrigerant can be used more to melt the frost layer on the surface of the heat exchanger.

[0114] Using the moment when the indoor fan speed decreases from the current speed to the target speed corresponding to the current micro-frost defrosting strategy as a benchmark, the first running time, the first indoor coil temperature, and the first outdoor coil temperature of the air conditioner 10 during the first defrosting stage are obtained. When the first indoor coil temperature Tin1 is less than or equal to the preset minimum indoor coil temperature threshold Ti_min, and the first outdoor coil temperature Te1 is greater than or equal to the first preset outdoor coil temperature threshold, and the first outdoor coil temperature Te1 is less than or equal to the second preset outdoor coil temperature threshold, i.e., when Ti1≤Ti_min and -0.5℃≤Te1≤0℃, it is determined that the air conditioner 10 meets the first preset condition, and the air conditioner 10 is controlled to exit the first defrosting stage and enter the second defrosting stage.

[0115] Alternatively, when the first running time reaches the first preset maximum running time, regardless of whether Ti1≤Ti_min and -0.5℃≤Te1≤0℃ are satisfied, it is determined that the current air conditioner 10 meets the first preset condition, and the air conditioner 10 is controlled to exit the first defrosting stage and enter the second defrosting stage. Since the system can accurately identify micro-frost, the frost thickness on the outdoor heat exchanger is necessarily less than the thickness required for normal hot air defrosting. Therefore, from the perspective of energy conservation, the sensible heat of the refrigerant required to melt micro-frost is lower than the heat required to melt thick frost. In addition, there is a second defrosting stage to continue the defrosting operation. Therefore, in the first defrosting stage, it is not necessary to increase the compressor frequency. It is only necessary to maintain the frequency of normal heating operation at the previous moment to meet the refrigerant temperature required for defrosting. Thus, while ensuring the defrosting effect, energy consumption is effectively reduced and the stability of system operation is improved.

[0116] Furthermore, after the high-temperature refrigerant exchanges heat with the frost layer in the first stage, some of the frost has melted into water. Since the compressor frequency has not increased during the defrosting process, the refrigerant temperature has significantly decreased. If defrosting continues solely based on this, the efficiency will be very low. Therefore, at this point, a defrosting method that relies on refrigerant sensible heat as a supplement and outdoor fan operating at high speed to generate forced convection (i.e., the second defrosting stage method) must be adopted.

[0117] Specifically, such as Figure 12 As shown, after the air conditioner 10 enters the second defrosting stage, the compressor is controlled to reduce its frequency to the first target operating frequency according to the first preset frequency reduction rate. For example, it reduces the frequency from 65Hz to 20Hz at a rate of 2Hz / s, and the first target operating frequency is greater than or equal to the preset minimum operating frequency (such as 20Hz). That is, if the compressor reduces its frequency by 50Hz from the current operating frequency of 65Hz at a frequency reduction rate of 2Hz, the calculated final operating frequency is 15Hz. Since 15Hz is less than the preset minimum operating frequency of 20Hz, the first target operating frequency is controlled to be 20Hz, that is, the compressor is actually controlled to operate at 20Hz. By limiting the minimum operating frequency, both stable compressor operation and the necessary refrigerant circulation volume of the system can be maintained.

[0118] Simultaneously, the indoor fan is controlled to maintain the target speed corresponding to the current micro-frost defrosting strategy, i.e., maintaining low fan speed operation during the first defrosting stage; the expansion valve opening is controlled to maintain the preset maximum opening (e.g., 500 steps), and the four-way valve is controlled to maintain its current reversing state; the outdoor fan is controlled according to either Scheme 1 or Scheme 2: Scheme 1 controls the outdoor fan to operate at the heating speed, i.e., at free speed; Scheme 2 increases the first preset speed above the heating speed. This enhances the forced convection heat transfer effect. Furthermore, during this period, the indoor electric heater is not allowed to automatically turn on to avoid interference with the system's accurate judgment of the micro-frost defrosting state.

[0119] In one embodiment of the present invention, when the air conditioner 10 is controlled to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the controller 71 is further configured to: when the outdoor ambient temperature is greater than a third preset temperature threshold, control the air conditioner to execute a second micro-frost defrosting strategy; when the air conditioner 10 is controlled to execute the second micro-frost defrosting strategy, the controller 71 is configured to: control the indoor fan to reduce its current speed to the target speed corresponding to the current micro-frost defrosting strategy, control the four-way valve to maintain its current reversing state, control the compressor to maintain its current operating frequency, control the expansion valve to maintain its current opening, and control the outdoor fan to maintain its current speed. The system obtains the second operating time and the second indoor coil temperature of the air conditioner 10 when executing the second micro-frost defrosting strategy; when the second indoor coil temperature is greater than or equal to the preset maximum indoor coil temperature threshold, or when the second operating time reaches the second preset maximum operating time, the system controls the compressor to reduce its frequency from the current operating frequency to the second target operating frequency according to the second preset frequency reduction rate, controls the outdoor fan to maintain its current speed or controls the outdoor fan to increase its speed by the second preset speed, controls the expansion valve to adjust its opening from the current opening to the preset maximum opening, and controls the indoor fan to maintain its target speed corresponding to the current micro-frost defrosting strategy, wherein the second preset target frequency is greater than or equal to the preset minimum operating frequency.

[0120] In this embodiment, the high-efficiency temperature range for micro-frost defrosting is defined as the outdoor ambient temperature Tout being between Tout_m and Tout ≤ 7°C. Within this high-efficiency temperature range, a defrosting method primarily employs forced convection defrosting, supplemented by refrigerant sensible heat defrosting and utilizing high-speed operation of the outdoor fan. Because the outdoor ambient temperature is relatively high within this high-efficiency temperature range, the temperature of the air blown out by the outdoor fan is also high. Maintaining high fan speed during defrosting accelerates the process and utilizes airflow energy to mechanically peel away water droplets adhering to the fin surface, allowing the melted water to flow down quickly. Therefore, different micro-frost defrosting strategies are implemented in different target temperature ranges. Specifically, a first micro-frost defrosting strategy is implemented in the low-efficiency temperature range, incorporating hot air defrosting characteristics to improve efficiency. A second micro-frost defrosting strategy is implemented in the high-efficiency temperature range, effectively improving defrosting efficiency in the low-efficiency temperature range and significantly expanding the applicable temperature range for micro-frost defrosting. For example, traditional microfrost defrosting requires an outdoor ambient temperature above 3°C to achieve high defrosting efficiency. Below 3°C, the defrosting time needs to be increased to compensate for this inefficiency. This increased defrosting time means significant fluctuations in indoor temperature, thus traditional microfrost defrosting does not offer a clear advantage in low-temperature ranges. However, this application, by implementing different microfrost defrosting strategies based on different target temperature ranges, maintains high defrosting efficiency even below 3°C, and completely melts the microfrost without requiring additional defrosting time.

[0121] refer to Figure 13 When the air conditioner 10 is executed with the second micro-frost defrosting strategy, the indoor fan is controlled to reduce its current speed to the target speed corresponding to the current micro-frost defrosting strategy, that is, the indoor fan is controlled to reduce its set speed to a lower level and run at a low speed; the four-way valve is controlled to maintain its current reversing state, the compressor is controlled to maintain its current operating frequency, the expansion valve is controlled to maintain its current opening degree, and the outdoor fan is controlled to maintain its current speed.

[0122] Subsequently, based on the moment when the indoor fan reduces to a low speed, the second running time and the second indoor coil temperature of the air conditioner 10 executing the second micro-frost defrosting strategy are obtained. When the second indoor coil temperature is greater than or equal to the preset maximum indoor coil temperature threshold, or the second running time reaches the second preset maximum running time, it is determined that the defrosting intensity needs to be further strengthened. At this time, the compressor is controlled to reduce its frequency from the current operating frequency to the second target operating frequency according to the second preset frequency reduction rate, that is, the compressor is controlled to reduce its frequency from the free frequency to the second target operating frequency according to the second preset frequency reduction rate.

[0123] During this process, the outdoor fan speed can be controlled according to Scheme 1 and Scheme 2: Scheme 1 controls the outdoor fan to maintain its current speed, i.e., controls the outdoor fan to operate at its free speed; Scheme 2 controls the outdoor fan to increase its speed by a second preset speed from its current speed, i.e., controls the outdoor fan to increase its speed by a second preset speed based on its free speed. For example, if the free speed is 800 rpm and the second preset speed is 100 rpm, then the increased outdoor fan speed will be 800 + 100 = 900 rpm. Simultaneously, the expansion valve is adjusted from its current opening to a preset maximum opening, i.e., the expansion valve is increased from its free opening to a preset maximum opening (e.g., 500 steps), and the indoor fan is kept at the target speed corresponding to the current micro-frost defrosting strategy. Therefore, by reducing the compressor frequency and opening the expansion valve wider, the refrigerant subcooling can be effectively reduced. Combined with the high-speed operation of the outdoor fan, forced convection heat transfer is used to quickly remove moisture from the fin surface and assist defrosting, thus ensuring defrosting efficiency while avoiding the impact of drastic fluctuations in system parameters on indoor comfort. In addition, the indoor electric heating should not be turned on automatically during this period to prevent interference with the system's accurate judgment of the defrosting status.

[0124] Among them, the set wind speed refers to the target wind speed at which the indoor fan operates according to the mode set by the user (such as high wind, medium wind, low wind or automatic wind); the free frequency refers to the operating frequency of the compressor that is autonomously adjusted according to the current heating demand before defrosting, without being subject to the forced intervention of the defrosting control strategy; and the free opening degree refers to the opening degree of the expansion valve that is autonomously adjusted according to the refrigerant flow demand of the system before defrosting, without being subject to the forced intervention of the defrosting control strategy.

[0125] In one embodiment of the present invention, the controller 71 is further configured to: acquire a second outdoor coil temperature and a third operating time for executing the first micro-frost defrosting strategy during the execution of the first micro-frost defrosting strategy; determine a first temperature difference threshold based on outdoor relative humidity and outdoor ambient temperature; determine a second temperature difference threshold between a third preset temperature threshold and the first temperature difference threshold; when it is determined that the air conditioner meets the first micro-frost defrosting exit condition based on the third operating time, the second outdoor coil temperature, and the second temperature difference threshold, control the air conditioner 10 to exit the micro-frost defrosting mode; and acquire a third outdoor coil temperature and a third operating time for executing the second micro-frost defrosting strategy during the execution of the second micro-frost defrosting strategy. The fourth running time for the second micro-frost defrosting mode; when the air conditioner meets the second micro-frost defrosting exit condition based on the third outdoor coil temperature and the fourth running time, the air conditioner is controlled to exit the micro-frost defrosting mode; the first micro-frost defrosting exit condition includes one of the following: the third running time reaches the third preset maximum running time; the second outdoor coil temperature is greater than or equal to the second temperature difference threshold, and the third running time reaches the first preset running time; the second micro-frost defrosting exit condition includes one of the following: the fourth running time reaches the fourth preset maximum running time; the third outdoor coil temperature is greater than or equal to the third preset temperature threshold, and the fourth running time reaches the second preset running time.

[0126] Specifically, after the air conditioner 10 exits the defrosting mode, the controller 71 is configured to: control the compressor to increase its speed according to a preset frequency increase rate, and after a first preset time delay, control the expansion valve, indoor fan, and outdoor fan to return to the heating operation state; after the air conditioner 10 exits the defrosting mode, the controller 71 is also configured to: when the time after the air conditioner 10 exits the defrosting mode is less than a preset time, suspend the judgment of entering the reverse defrosting mode.

[0127] In this embodiment, the outdoor relative humidity, the second outdoor coil temperature, and the third operating time of the air conditioner 10 during the execution of the first micro-frost defrosting strategy are obtained. Based on the outdoor relative humidity and outdoor ambient temperature, and combined with measured data obtained during the experiment, a first temperature difference threshold is determined. A second temperature difference threshold is calculated between a third preset temperature threshold and the first temperature difference threshold. If the second outdoor coil temperature is greater than or equal to the second temperature difference threshold, and the third operating time reaches the first preset operating time, the first micro-frost defrosting exit condition is determined to be met, and the air conditioner 10 is controlled to exit the micro-frost defrosting mode. Alternatively, if the third operating time reaches the third preset maximum operating time, regardless of whether the above temperature and duration conditions are met, the first micro-frost defrosting exit condition is forcibly determined to be met, and the air conditioner 10 is controlled to exit the micro-frost defrosting mode. By introducing a relative humidity-corrected temperature difference threshold, the frosting characteristics under different humidity environments can be matched more accurately, ensuring timely exit after the frost layer has completely melted, avoiding ineffective operation.

[0128] Furthermore, during the execution of the second micro-frost defrosting strategy, the air conditioner 10 acquires the third outdoor coil temperature and the fourth operating time of the second micro-frost defrosting. When the third outdoor coil temperature is greater than or equal to the third preset temperature threshold, and the fourth operating time reaches the second preset operating time, it is determined that the air conditioner 10 meets the second micro-frost defrosting exit condition. Alternatively, regardless of whether the above temperature and duration conditions are met, as long as the fourth operating time reaches the fourth preset maximum operating time, it is determined that the air conditioner 10 meets the second micro-frost defrosting exit condition, and the air conditioner 10 is controlled to exit the micro-frost defrosting mode. This dual exit mechanism combines temperature determination and time protection, which can ensure rapid recovery of heating when the frost layer is completely melted, improving comfort, and prevent defrosting dead loops caused by sensor failure or extreme operating conditions, thereby ensuring the reliability and safety of the air conditioner operation.

[0129] Furthermore, after the defrosting process is complete, the compressor, expansion valve, indoor fan, and outdoor fan resume normal operation. For example... Figure 6 As shown, when the compressor frequency increases, the outdoor heat exchanger tube temperature (i.e., the outdoor coil temperature) experiences a brief, rapid drop followed by a rise. Because the reverse defrosting timer is not reset at this time, the outdoor heat exchanger temperature difference is likely to be greater than or equal to the reverse defrosting entry threshold (i.e., the first preset temperature difference threshold), leading to erroneous entry into reverse defrosting. Therefore, after the micro-frost defrosting ends, reverse defrosting is not performed for a preset time (e.g., tx seconds). By setting this protective delay mechanism, the controller 71 can effectively avoid the unstable phase of drastic fluctuations in the outdoor heat exchanger tube temperature during the initial stage of compressor frequency increase, preventing misjudgment of the outdoor heat exchanger temperature difference due to transient temperature changes. This avoids the system erroneously triggering the reverse defrosting mode immediately after the micro-frost defrosting ends, ensuring the accuracy of the defrosting logic and reducing the impact of unnecessary mode switching on system stability and user comfort.

[0130] In one embodiment of the present invention, when determining the target temperature difference based on the dew point temperature and the outdoor coil temperature, the controller 71 is configured to: determine the difference between the dew point temperature and the outdoor coil temperature; when the difference is greater than a fourth preset temperature threshold and the outdoor coil temperature is less than the fourth preset temperature threshold, use the difference as the target temperature difference; when the difference is less than or equal to the fourth preset temperature threshold, or when the outdoor coil temperature is greater than or equal to the fourth preset temperature threshold, correct the target temperature difference to the fourth preset temperature threshold.

[0131] The fourth preset temperature threshold is, for example, 0℃.

[0132] In this embodiment, when determining the target temperature difference based on the dew point temperature and the outdoor coil temperature, the difference between the dew point temperature and the outdoor coil temperature is first calculated, and it is determined whether the difference is greater than 0°C and whether the outdoor coil temperature is less than 0°C. If the difference is greater than 0°C and the outdoor coil temperature is less than 0°C, it indicates that the current environment meets the temperature and humidity conditions for frost formation, and the difference is directly used as the target temperature difference. If the difference is less than or equal to 0°C, or the outdoor coil temperature is greater than or equal to 0°C, it indicates that the current environment is in a state where frost formation is unlikely or there is no risk of frost formation, and the target temperature difference is corrected to 0°C. By limiting the lower limit of the target temperature difference, it is ensured that the effective calculation of frost thickness is only performed under operating conditions with actual frost risk, avoiding invalid calculations and improving the accuracy of defrosting control.

[0133] The air conditioner 10 of the above embodiments of the present invention will be further described below with reference to specific examples: In this specific embodiment, Example 1: An outdoor coil temperature sensor with an accuracy of 1℃ is used, equipped with an outdoor humidity sensor. The relevant parameters are set as follows: k=2, preset minimum continuous running time t_min=20min, first frost thickness threshold H1=60, second frost thickness threshold H2=80, third frost thickness threshold H3=120, third preset temperature threshold Tout_m=3℃, preset maximum indoor coil temperature threshold Ti_max=45℃, preset minimum indoor coil temperature threshold Ti_min=25℃, first temperature difference threshold ΔT_ws=2℃. The first preset time t_ws5=60s, the preset duration tx=300s, the defrosting frequency increase / decrease rate X=2Hz / s, the normal heating frequency increase / decrease rate X=0.5Hz / s, the compressor operating frequency change value △F=50Hz, the preset minimum operating frequency Fmin=20Hz, the outdoor fan current speed R=800rpm, the first preset speed or the second preset speed △R=100rpm, and the preset maximum opening EEVmax=500 steps.

[0134] In heating mode, the compressor starts running and begins timing the continuous running time t_run1 of the compressor entering micro-frost defrosting, the cumulative running time t_run2 of the compressor entering hot gas defrosting, and the continuous running time t_run3 of the compressor entering reverse defrosting. The target temperature difference ΔTL between the dew point temperature and the outdoor coil temperature is recorded and calculated in real time, and its integral is continuously calculated. Data is recorded starting from time 0: outdoor ambient temperature Tout(0) = 2℃, outdoor relative humidity Rh(0) = 80%, outdoor coil temperature Te(0) = 2℃ > 0℃, the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(0) = -1.7℃ - 2℃ = -3.7℃ < 0, therefore ΔTL(0) = 0℃; at the 10th minute, outdoor ambient temperature Tout(10) = 2℃, outdoor relative humidity Rh(10) = 80%, outdoor coil temperature Te(10) = -4℃, the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(10) = -1.7℃ - (-4℃) = 2.3℃, so the frost thickness in the first 10 minutes is... Approximately equal to 23 (the example calculation assumes the frost layer increases linearly for ease of calculation; in practice, it is calculated based on the actual integration at each moment); continuing the integration, at the 20th minute, the outdoor ambient temperature Tout(20) = 2℃, the outdoor relative humidity Rh(20) = 80%, the outdoor coil temperature Te(20) = -4℃, and the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(20) = -1.7℃ - (-4℃) = 2.3℃. Therefore, the frost thickness in the first 20 minutes is... H is approximately equal to 23 + 46 = 69 > H1, and the compressor's continuous running time t_run1 = 20 min = t_min, which meets the conditions for entering the micro-frost defrosting process. Therefore, micro-frost defrosting control is initiated (this moment serves as the timing reference point for the defrosting process). The outdoor coil temperature Te_ws0 = -4℃ is recorded at this moment. The already timed t_run1 is reset to zero, while t_run3 continues timing.

[0135] The outdoor ambient temperature Tout(20) at the moment of entering the micro-frost defrosting is 2°C, which is within the range of 0°C < Tout(20) < Tout_m. Therefore, the first defrosting stage is executed first. The current compressor frequency remains unchanged at 65 Hz, the indoor fan speed is reduced to low speed to increase the refrigerant temperature, the outdoor fan stops to weaken the heat exchange between the refrigerant and the outdoor environment side, and at the same time, the expansion valve opening is opened to the maximum step of 500 steps. Taking the moment when the indoor unit speed is reduced to low speed as the timing reference point, continuously detect the first indoor heat exchanger tube temperature Ti1 and the first outdoor heat exchanger tube temperature Te1. At the 50th second, Ti1 = 24°C < Ti_min = 25°C, Te1 = 0°C (theoretically, it should be between -0.5°C and 0°C. Due to the sensor accuracy of 1°C, it can only be taken as 0°C), which meets the conditions, and enters the second defrosting stage. The time is cleared, and taking the moment when the compressor frequency is reduced as the timing reference point, the compressor frequency is reduced at a speed of 2 Hz / s to 20 Hz (65 - 50 = 15 Hz < Fmin = 20 Hz, and actually finally drops to 20 Hz). At the same time, the indoor fan remains at low speed unchanged, the expansion valve opening remains at 500 steps unchanged, and the outdoor fan changes to 900 rpm (normal speed R + △R). At the 203rd second, the outdoor ambient temperature Tout = 2°C, and the third outdoor coil temperature Te3 = 1°C ≥ Tout_m - △T_ws = 3 - 2 = 1°C. At the 213th second, the outdoor ambient temperature Tout = 2°C, and the third outdoor coil temperature Te3 = 1°C ≥ Tout_m - △T_ws = 3 - 2 = 1°C (that is, Te3 ≥ Tout_m - △T_ws and the third running duration reaches the first preset running duration of 10 s), and the micro-frost defrosting control is exited. Taking the exit moment as the timing reference point, keep the expansion valve opening at 500 steps for the first preset time t_ws5 = 60 s, and do not judge reverse defrosting within the preset duration tx = 300 s. Tout_m - △T_ws is the second temperature difference threshold.

[0136] Switch to normal heating. At this time, the indoor fan resumes its original speed, the compressor resumes free control and increases its frequency at a speed of 2 Hz / s, and the expansion valve opening and the outdoor fan resume free control. Restart the timing of the continuous micro-frost defrosting running time t_run1, the cumulative hot gas defrosting running time t_run2, and the cumulative reverse defrosting running time t_run3.

[0137] After a certain period of time, due to the outdoor temperature dropping due to rain, it is detected that Tout = -2°C and Rh = 100%. The outdoor frosting speed increases significantly. Before the compressor runs continuously for 20 minutes, H has already been greater than 120, meeting the conditions for reverse defrosting, and enters reverse defrosting, and the already timed t_run1, t_run2, and t_run3 are all cleared. After defrosting and frosting, heating is restarted, and t_run1, t_run2, and t_run3 start timing again.

[0138] Example 2: Using an outdoor coil temperature sensor with an accuracy of 1℃, and equipped with an outdoor humidity sensor, the relevant parameters are set as follows: k=2, preset minimum continuous running time t_min=20min, first frost thickness threshold H1=60, second frost thickness threshold H2=80, third frost thickness threshold H3=120, third preset temperature threshold Tout_m=3℃, preset maximum indoor coil temperature threshold Ti_max=45℃, preset minimum indoor coil temperature threshold Ti_min=25℃, first temperature difference threshold ΔT_ws=2℃ The second preset running time t_ws4=60s, the first preset time t_ws5=60s, the preset duration tx=300s, the defrosting frequency increase / decrease rate X=2Hz / s, the normal heating frequency increase / decrease rate X=0.5Hz / s, ΔF=50Hz, Fmin=20Hz, the current outdoor fan speed R=800rpm, the first preset speed or the second preset speed ΔR=100rpm, and the preset maximum opening EEVmax=500 steps.

[0139] In heating mode, the compressor starts running and begins timing the continuous running time t_run1 of the compressor entering micro-frost defrosting, the cumulative running time t_run2 of the compressor entering hot gas defrosting, and the continuous running time t_run3 of the compressor entering reverse defrosting. The target temperature difference ΔTL between the dew point temperature and the outdoor coil temperature is recorded and calculated in real time, and its integral is continuously calculated. Data is recorded starting from time 0: outdoor ambient temperature Tout(0) = 6℃, outdoor relative humidity Rh(0) = 80%, outdoor coil temperature Te(0) = 6℃ > 0℃, the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(0) = 2.2℃ - 6℃ = -3.8℃ < 0, therefore ΔTL(0) = 0℃; at the 10th minute, outdoor ambient temperature Tout(10) = 6℃, outdoor relative humidity Rh(10) = 80%, outdoor coil temperature Te(10) = 4℃, the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(10) = 2.2℃ - 4℃ = -1.8℃ < 0, therefore ΔTL(10) = 0℃; at the 15th minute, Outdoor ambient temperature Tout(15) = 6℃, outdoor relative humidity Rh(15) = 80%, outdoor coil temperature Te(15) = 3℃, the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(15) = 2.2℃ - 3℃ = -0.8℃ < 0, therefore ΔTL(15) = 0℃; at the 20th minute, outdoor ambient temperature Tout(20) = 6℃, outdoor relative humidity Rh(20) = 80%, outdoor coil temperature Te(20) = 2℃, the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(20) = 2.2℃ - 2℃ = 0.2℃, so the actual frost thickness in the first 20 minutes is from the 15th minute to the 20th minute. Approximately equal to 1 (for example, the calculation is based on the linear increase of the frost layer for ease of calculation; in practice, it is calculated based on the actual integration at each moment); continuing the integration, at the 30th minute, the outdoor ambient temperature Tout(30) = 6℃, the outdoor relative humidity Rh(30) = 80%, the outdoor coil temperature Te(30) = 0℃, and the target temperature difference between the dew point temperature and the outdoor coil temperature ΔTL(30) = 2.2℃ - 0℃ = 2.2℃. Therefore, the frost thickness in the first 30 minutes is... H is approximately equal to 1+24=25H1, and the compressor continuous running time t_run1=38min>t_min, which meets the conditions for entering the micro-frost defrosting, and enters the micro-frost defrosting control (the timing reference point of the defrosting process at this moment). Record the outdoor heat exchanger tube temperature Te_ws0=0℃ at this moment. The already timed t_run1 is reset to zero, while t_run3 continues to be timed.<h1>

[0140] When the outdoor ambient temperature Tout(38) at the time of entering the micro-frost defrosting moment is 6℃, it is within the range of Tout(38)=6℃≥Tout_m=3℃. The second micro-frost defrosting strategy is executed. The indoor fan speed is reduced to low wind, the refrigerant temperature is increased, and the second indoor heat exchanger tube temperature Ti2 is continuously monitored. The timing reference point is the moment when the indoor unit speed is reduced to low wind. At 60s, Ti2=44℃<Ti_max=45℃. However, the second running time t≥ the second preset running time t_ws4=60s. Therefore, the next step is started. The time is reset to zero, and the timing reference point is the moment when the compressor frequency decreases. The compressor frequency is reduced from 65Hz to 20Hz at a speed of 2Hz / s (65-50=15Hz<Fmin=20Hz, and it is actually reduced to 20Hz in the end). At the same time, the expansion valve opening is opened to the maximum number of steps 500, and the outdoor fan is increased from 800rpm to 900rpm by ΔR. At 200s, Tout=6℃, the third outdoor coil temperature Te=3℃ ≥ the third preset temperature threshold Tout_m=3℃. At 210s, Tout=6℃, the third outdoor coil temperature Te=3℃ ≥ the third preset temperature threshold Tout_m=3℃ (i.e., Te≥Tout_m and the fourth running time reaches the second preset running time of 10s), and the micro-frost defrosting control is exited. Taking the exit time as the timing reference point, the expansion valve opening is maintained at 500 steps for the first preset time t_ws5=60s, and reverse defrosting is not judged within the preset time tx=300s.

[0141] Switching to normal heating mode, the indoor fan resumes its original speed, the compressor regains free control and increases its frequency at 2Hz / s, and the expansion valve opening and outdoor fan regain free control. The micro-frost defrosting continuous operation time t_run1, the hot gas defrosting cumulative operation time t_run2, and the reverse defrosting cumulative operation time t_run3 are restarted.

[0142] Example 3: The air conditioner 10 is not equipped with an outdoor humidity sensor. The outdoor relative humidity is predicted by virtual humidity sensing technology. An outdoor coil temperature sensor with an accuracy of 1℃ is used. The relevant parameters are set as follows: k=2, preset minimum continuous running time t_min=20min, first preset running time t_Vrun1=5min, first frost thickness threshold H1=60, second frost thickness threshold H2=80, third frost thickness threshold H3=120. First temperature difference threshold △T_ws=2℃, third preset temperature threshold Tout_m=3℃, preset maximum indoor coil temperature threshold Ti_max=45℃, preset minimum indoor coil temperature threshold Ti_min=25℃, preset heat exchange temperature difference threshold △Tout_st=6℃, first preset time t_ws5=60s, preset duration tx=300s, defrosting frequency increase / decrease rate X=2Hz / s, normal heating frequency increase / decrease rate X=0.5Hz / s, compressor operating frequency change value △F=50Hz, preset minimum operating frequency Fmin=20Hz, preset frequency change value △F1=5Hz, outdoor fan current speed R=800rpm, first preset speed or second preset speed △R=100rpm, preset maximum opening EEVmax=500 steps.

[0143] In heating mode, the compressor starts running and begins timing the continuous running time t_run1 of the compressor entering micro-frost defrosting, the cumulative running time t_run2 of the compressor entering hot gas defrosting, and the continuous running time t_run3 of the compressor entering reverse defrosting. From t_Vrun1 = 5 min, F(5) - F(4) = 4 Hz < ΔF, meaning the frequency change between the compressor's continuous 5-minute running frequency and its 4-minute running frequency is 4 Hz, which is less than the preset frequency change value. Furthermore, the outdoor heat exchange temperature difference ΔTout(n) = 2℃ < ΔTout_st. Data recording begins, and the target temperature difference ΔTL between the dew point temperature and the outdoor coil temperature is calculated. The integral is continuously calculated: outdoor ambient temperature Tout(0) = 2℃, virtual humidity Rh_V(0) (i.e., the outdoor relative humidity predicted by the humidity prediction model) = 80%, outdoor coil temperature Te(0) = 2℃. =2.0℃>0℃, the difference between the dew point temperature and the outdoor heat exchanger temperature △TL(0)=-1.7℃-2℃=-3.7℃<0, then △TL(0)=0℃; at the 10th minute, the outdoor ambient temperature Tout(10)=2℃, the virtual humidity Rh_v(10)=80%, the outdoor heat exchanger tube temperature Te(10)=-4℃, the target temperature difference between the dew point temperature and the outdoor coil temperature △TL(10)=-1.7℃-(-4℃)=2.3℃, so the frost thickness in the first 10 minutes is Approximately equal to 23 (for example, the calculation is based on the linear increase of the frost layer for ease of calculation; in practice, it is calculated based on the actual integration at each moment); continuing the integration, at the 20th minute, the outdoor ambient temperature Tout(20) = 2℃, the virtual humidity Rh_v(20) = 80%, the outdoor coil temperature Te(20) = -4℃, and the target temperature difference between the dew point temperature and the outdoor coil temperature △TL(20) = -1.7℃ - (-4℃) = 2.3℃. Therefore, the frost thickness in the first 20 minutes is... H is approximately equal to 23 + 46 = 69 > H1, and the compressor's continuous running time t_run1 = 20 min = t_min, which meets the conditions for entering the micro-frost defrosting process. Therefore, micro-frost defrosting control is initiated (this moment serves as the timing reference point for the defrosting process). The outdoor coil temperature Te_ws0 = -4℃ is recorded at this moment. The already timed t_run1 is reset to zero, while t_run3 continues timing.

[0144] The outdoor ambient temperature Tout(20) at the time of entering the micro-frost defrosting moment is 2℃, which is in the range of 0℃<Tout(20)<Tout_m. Therefore, the first defrosting stage of the first micro-frost defrosting strategy is executed first. The current compressor frequency is 65hz and remains unchanged. The indoor fan speed is reduced to low wind to increase the refrigerant temperature. The outdoor fan stops to weaken the heat exchange between the refrigerant and the outdoor environment. At the same time, the expansion valve opening is opened to the maximum number of steps, 500 steps. Taking the moment when the indoor unit speed is reduced to low wind as the timing reference point, the first indoor heat exchanger tube temperature Ti1 and the first outdoor coil temperature Te1 are continuously detected. At 50s, Ti1=24℃≤Ti_min=25℃, Te1=0℃ (theoretically it should be between -0.5℃ and 0℃, but since the sensor accuracy is 1℃, it can only take the value of 0℃). If the conditions are met, the system enters the second defrosting stage. The time is reset to zero, and the compressor frequency is reduced to 20Hz at a rate of 2Hz / s (65-50=15Hz<Fmin=20Hz, and the actual final frequency is 20Hz). At the same time, the indoor fan maintains a low speed, the expansion valve opening remains unchanged at 500 steps, and the outdoor fan switches to 900rpm (normal speed R+△R). At 203s, the outdoor ambient temperature Tout=2℃, and the second outdoor coil temperature Te=1℃≥Tout_m-△T_ws=3-2=1℃. At 213s, the outdoor ambient temperature Tout=2℃, and the second outdoor coil temperature Te=1℃≥Tout_m-△T_ws=3-2=1℃ (i.e., the second outdoor coil temperature Te≥Tout_m -△T_ws and the third running time reaches the first preset running time of 10s). The micro-frost defrosting control is then exited. Using the exit time as the timing reference point, the expansion valve opening is maintained at 500 steps for a first preset time t_ws5=60s, and reverse defrosting is not judged within a preset time tx=300s. Tout_m-△T_ws is the second temperature difference threshold.

[0145] Switching to normal heating mode, the indoor fan resumes its original speed, the compressor regains free control and increases its frequency at 2Hz / s, and the expansion valve opening and outdoor fan regain free control. The micro-frost defrosting continuous operation time t_run1, the hot gas defrosting cumulative operation time t_run2, and the reverse defrosting cumulative operation time t_run3 are restarted.

[0146] After some time, due to rain and temperature drop outdoors, the measured Tout = -2℃ and virtual humidity Rh_v(n) = 100%. The outdoor frost formation rate increased significantly. Within less than 20 minutes of continuous compressor operation, H already exceeded 120, meeting the conditions for reverse defrosting. Reverse defrosting was initiated, and the timers t_run1, t_run2, and t_run3 were reset to zero. After defrosting and frost formation, heating restarted, and the timers for t_run1, t_run2, and t_run3 restarted.

[0147] According to an embodiment of the present invention, an air conditioner 10 with multiple defrosting modes acquires the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity after the air conditioner is turned on for heating and the compressor starts. The dew point temperature is determined based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship. Then, the target temperature difference is calculated based on the dew point temperature and the outdoor coil temperature, and integrated based on the compressor running time and the target temperature difference to calculate the frost thickness. This allows for dynamic calculation of the frost thickness based on changes in the outdoor environment, improving the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner. After calculating the frost thickness, the air conditioner is controlled to enter one of three modes: a micro-frost defrosting mode, a hot gas defrosting mode, or a reverse defrosting mode, thereby improving the accuracy of defrosting intervention and the reliability of the air conditioner. After the air conditioner enters the micro-frost defrosting mode, it executes a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature. This strategy employs a high-efficiency approach for rapid defrosting in high-temperature ranges and a conservative approach to prevent icing in low-temperature ranges. This ensures the efficiency and safety of micro-frost defrosting under various operating conditions, effectively avoiding incomplete defrosting or secondary icing caused by excessively low ambient temperatures. At the same time, it minimizes indoor temperature fluctuations, thereby improving the heating reliability and user comfort of the air conditioner in low-temperature and high-humidity environments.

[0148] The following is for reference. Figure 14 This invention describes a defrosting control method for an air conditioner according to an embodiment of the present invention.

[0149] like Figure 14 As shown, the defrosting control method for an air conditioner according to an embodiment of the present invention includes at least steps S1-S5.

[0150] Step S1: After the air conditioner is turned on for heating and the compressor starts, obtain the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity.

[0151] Step S2: Determine the dew point temperature based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship. The preset mapping relationship includes multiple sets of correspondences between outdoor ambient temperature, outdoor relative humidity, and dew point temperature.

[0152] Step S3: Determine the target temperature difference based on the dew point temperature and the outdoor coil temperature.

[0153] Step S4: Determine the frost thickness of the air conditioner based on the compressor's running time and the difference between the target temperature and the frost thickness.

[0154] Step S5: Based on the frost thickness, outdoor ambient temperature, and compressor running time, control the air conditioner to enter the corresponding target defrosting mode. The target defrosting modes include micro-frost defrosting mode, hot air defrosting mode, and reverse defrosting mode. After controlling the air conditioner to enter the micro-frost defrosting mode, the controller is configured to: control the air conditioner to execute the micro-frost defrosting strategy corresponding to the target temperature range based on the target temperature range of the outdoor ambient temperature. Different temperature ranges correspond to different micro-frost defrosting strategies, and the conditions for triggering compressor frequency reduction are different under different micro-frost defrosting strategies.

[0155] In one embodiment of the present invention, determining the frost thickness of the air conditioner based on the compressor's operating time and the target temperature difference includes: determining the frost thickness of the air conditioner according to the compressor's operating time and the target temperature difference, and according to a preset algorithm, wherein the frost thickness is positively correlated with the target temperature difference and the compressor's operating time; the preset algorithm includes: Where H represents the frost thickness, t_js represents the compressor running time, △TL represents the target temperature difference, and k is a preset constant.

[0156] In one embodiment of the present invention, the air conditioner is controlled to enter a corresponding target defrosting mode based on the frost thickness, outdoor ambient temperature, and compressor operating time. This includes: acquiring the continuous operating time of the air conditioner in the micro-frost defrosting mode, the cumulative operating time in the hot air defrosting mode, and the cumulative operating time in the reverse defrosting mode; when the frost thickness is greater than or equal to a first frost thickness threshold and less than a second frost thickness threshold, and the outdoor ambient temperature is greater than a first outdoor ambient temperature threshold, and the first outdoor ambient temperature threshold is greater than a first preset temperature threshold, and the continuous operating time of the micro-frost defrosting mode is greater than or equal to the compressor operating time, the air conditioner is controlled to enter the micro-frost defrosting mode; when the frost thickness is greater than or equal to a second frost thickness threshold and less than a third frost thickness threshold, and the outdoor ambient temperature is greater than or equal to a second outdoor ambient temperature threshold, and the cumulative operating time of the hot air defrosting mode is greater than or equal to the compressor operating time, the air conditioner is controlled to enter the hot air defrosting mode; when the frost thickness is greater than or equal to a third frost thickness threshold, the air conditioner is controlled to enter the reverse defrosting mode.

[0157] In one embodiment of the present invention, when obtaining outdoor relative humidity, the method includes: when the air conditioner includes an outdoor humidity sensor and the outdoor humidity sensor is working properly, the humidity value detected by the outdoor humidity sensor is taken as the outdoor relative humidity; or, when the air conditioner does not include an outdoor humidity sensor or the air conditioner includes an outdoor humidity sensor but the outdoor humidity sensor is not working properly, the humidity value predicted based on the outdoor ambient temperature, the operating parameters of the air conditioner and the pre-trained humidity prediction model is taken as the outdoor relative humidity.

[0158] In one embodiment of the present invention, when using the humidity value predicted based on the outdoor ambient temperature, the air conditioner's operating parameters, and a pre-trained humidity prediction model as the outdoor relative humidity, the method includes: updating the outdoor relative humidity according to preset update conditions; wherein the preset update conditions include: when the compressor's operating time is greater than or equal to a first preset operating time, acquiring the compressor's operating frequency change value and the indoor heat exchange temperature difference every second preset operating time, wherein the indoor heat exchange temperature difference is determined based on the difference between the outdoor ambient temperature and the outdoor coil temperature; when the compressor's operating frequency change value is less than or equal to a preset frequency change value, and the indoor heat exchange temperature difference is less than a preset heat exchange temperature difference threshold, acquiring the compressor's operating frequency change value and the indoor heat exchange temperature difference every second preset operating time. The outdoor relative humidity is updated once every four preset operating times; or, the heating operating time of the air conditioner in heating mode is obtained, and when the heating operating time is greater than or equal to a third preset operating time, the outdoor relative humidity is updated once every four preset operating times; or, when the air conditioner is in a stopped state or enters the corresponding target defrost mode, the update of the outdoor relative humidity is paused; when updating the outdoor relative humidity according to the preset update conditions, it also includes: when the air conditioner is in an operating state that does not meet the preset update conditions, the outdoor relative humidity is maintained at the humidity value determined when the preset update conditions were met last time, until the operating state of the air conditioner meets the preset update conditions again, and then the outdoor relative humidity is re-determined and updated.

[0159] In one embodiment of the present invention, the defrosting control method of the air conditioner further includes: if the compressor is starting up for the first time and the first start-up time of the compressor is less than a fifth preset running time, and / or, when the air conditioner enters the corresponding target defrosting mode, pausing the prediction of outdoor relative humidity, and determining the dew point temperature based on the outdoor relative humidity obtained from the last prediction before pausing the prediction; when the compressor stops and restarts after meeting the shutdown conditions, and the compressor shutdown time is less than a sixth preset running time, and the running time after the compressor restarts is less than the fifth preset running time, determining the dew point temperature based on the outdoor relative humidity before the compressor stops, wherein the shutdown conditions include compressor failure or the compressor reaching a set temperature; if the compressor shutdown time is greater than or equal to the sixth preset running time, then the current start of the compressor is taken as the first start-up, and the step of the compressor being the first start-up is executed.

[0160] In one embodiment of the present invention, when controlling the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the method includes: when the outdoor ambient temperature is greater than a second preset temperature threshold and the outdoor ambient temperature is less than or equal to a third preset temperature threshold, controlling the air conditioner to execute a first micro-frost defrosting strategy; when controlling the air conditioner to execute the first micro-frost defrosting strategy, the method includes: controlling the air conditioner to enter a first defrosting stage, and during the first defrosting stage, controlling the indoor fan to reduce its speed from the current speed to the target speed corresponding to the current micro-frost defrosting strategy, controlling the four-way valve to maintain its current reversing state, controlling the compressor to maintain its current operating frequency, controlling the opening of the expansion valve to adjust to a preset maximum opening, and controlling the outdoor fan to stop operating; acquiring the first operating time, the first indoor coil temperature, and the first outdoor coil temperature of the air conditioner executing the first defrosting stage; and based on the first indoor coil temperature, the first outdoor coil temperature, and the first operating time... The system determines whether the air conditioner meets the first preset condition based on the duration of operation. If so, it controls the air conditioner to exit the first defrosting stage and enter the second defrosting stage. The first preset condition includes one of the following: the first operating time reaches the first preset maximum operating time; the first indoor coil temperature is less than or equal to the preset minimum indoor coil temperature threshold, and the first outdoor coil temperature is greater than or equal to the first preset outdoor coil temperature threshold, and the first outdoor coil temperature is less than or equal to the second preset outdoor coil temperature threshold. After entering the second defrosting stage, the system controls the compressor to reduce its frequency to the first target operating frequency according to the first preset frequency reduction rate, controls the indoor fan to maintain the target speed corresponding to the current micro-frost defrosting strategy, controls the expansion valve to maintain the preset maximum opening, controls the four-way valve to maintain its current reversing state, and controls the outdoor fan to operate at the heating operating speed or increase the first preset speed above the heating operating speed. The first target operating frequency is greater than or equal to the preset minimum operating frequency.

[0161] In one embodiment of the present invention, when controlling the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the method further includes: when the outdoor ambient temperature is greater than a third preset temperature threshold, controlling the air conditioner to execute a second micro-frost defrosting strategy; when controlling the air conditioner to execute the second micro-frost defrosting strategy, the method includes: controlling the indoor fan to reduce its current speed to the target speed corresponding to the current micro-frost defrosting strategy, controlling the four-way valve to maintain its current reversing state, controlling the compressor to maintain its current operating frequency, controlling the expansion valve to maintain its current opening, and controlling the outdoor fan to maintain its current speed; obtaining the air conditioner's execution of the second micro-frost defrosting strategy. The second operating time and the second indoor coil temperature of the two micro-frost defrosting strategy; when the second indoor coil temperature is greater than or equal to the preset maximum indoor coil temperature threshold, or when the second operating time reaches the second preset maximum operating time, the compressor is controlled to reduce its frequency from the current operating frequency to the second target operating frequency according to the second preset frequency reduction rate, the outdoor fan is controlled to maintain its current speed or the outdoor fan is controlled to increase its speed by the second preset speed, the expansion valve is controlled to adjust its opening from the current opening to the preset maximum opening, and the indoor fan is controlled to maintain its target speed corresponding to the current micro-frost defrosting strategy. The second preset target frequency is greater than or equal to the preset minimum operating frequency.

[0162] In one embodiment of the present invention, the defrosting control method for an air conditioner further includes: during the execution of a first micro-frost defrosting strategy, acquiring a second outdoor coil temperature and a third operating time for executing the first micro-frost defrosting strategy; determining a first temperature difference threshold based on outdoor relative humidity and outdoor ambient temperature; determining a second temperature difference threshold between a third preset temperature threshold and the first temperature difference threshold; when it is determined that the air conditioner meets the first micro-frost defrosting exit condition based on the third operating time, the second outdoor coil temperature, and the second temperature difference threshold, controlling the air conditioner to exit the micro-frost defrosting mode; and during the execution of a second micro-frost defrosting strategy, acquiring a third outdoor coil temperature and a fourth operating time for executing the second micro-frost defrosting; when it is determined that the air conditioner meets the second micro-frost defrosting exit condition based on the third outdoor coil temperature and the fourth operating time, controlling the air conditioner to exit the micro-frost defrosting mode; the first micro-frost defrosting strategy... The defrost-to-defrost exit conditions include one of the following: the third running time reaches the third preset maximum running time; the second outdoor coil temperature is greater than or equal to the second temperature difference threshold, and the third running time reaches the first preset running time; the second micro-frost-to-defrost exit conditions include one of the following: the fourth running time reaches the fourth preset maximum running time; the third outdoor coil temperature is greater than or equal to the third preset temperature threshold, and the fourth running time reaches the second preset running time; wherein, after controlling the air conditioner to exit the micro-frost-to-defrost mode, the process includes: controlling the compressor to increase its speed according to a preset frequency increase rate, and after a first preset time delay, controlling the expansion valve, indoor fan, and outdoor fan to return to the heating operation state; after controlling the air conditioner to exit the micro-frost-to-defrost mode, the process also includes: when the time after the air conditioner exits the micro-frost-to-defrost mode is less than a preset time, suspending the judgment of entering the reverse defrost mode.

[0163] In one embodiment of the present invention, when determining the target temperature difference based on the dew point temperature and the outdoor coil temperature, the method includes: determining the difference between the dew point temperature and the outdoor coil temperature; when the difference is greater than a fourth preset temperature threshold and the outdoor coil temperature is less than the fourth preset temperature threshold, using the difference as the target temperature difference; when the difference is less than or equal to the fourth preset temperature threshold, or when the outdoor coil temperature is greater than or equal to the fourth preset temperature threshold, correcting the target temperature difference to the fourth preset temperature threshold.

[0164] According to the defrosting control method of an air conditioner according to an embodiment of the present invention, after the air conditioner is turned on for heating and the compressor starts, the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity are acquired. The dew point temperature is determined based on the outdoor ambient temperature, outdoor relative humidity, and a preset mapping relationship. Then, the target temperature difference is calculated based on the dew point temperature and the outdoor coil temperature, and integrated based on the compressor running time and the target temperature difference to calculate the frost thickness of the air conditioner. This allows for dynamic calculation of the frost thickness based on changes in the outdoor environment, improving the accuracy of frost thickness calculation while reducing the hardware cost of the air conditioner. After calculating the frost thickness, the air conditioner is controlled to enter one of three modes: micro-frost defrosting mode, hot gas defrosting mode, and reverse defrosting mode, thereby improving the accuracy of defrosting intervention and the reliability of the air conditioner. After the air conditioner enters the micro-frost defrosting mode, it executes a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature. This strategy employs a high-efficiency approach for rapid defrosting in high-temperature ranges and a conservative approach to prevent icing in low-temperature ranges. This ensures the efficiency and safety of micro-frost defrosting under various operating conditions, effectively avoiding incomplete defrosting or secondary icing caused by excessively low ambient temperatures. At the same time, it minimizes indoor temperature fluctuations, thereby improving the heating reliability and user comfort of the air conditioner in low-temperature and high-humidity environments.

[0165] In the description of this specification, references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example.

[0166] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. An air conditioner with multiple defrosting modes, characterized in that, include: The refrigerant circulation loop allows the refrigerant to circulate in a loop consisting of a compressor, condenser, expansion valve, and evaporator. One of the condensers and the other of the evaporator is an outdoor heat exchanger and the other is an indoor heat exchanger. Outdoor ambient temperature sensor, used to detect outdoor ambient temperature; Outdoor coil temperature sensor, used to detect the temperature of outdoor coil; The controller is configured to: After the air conditioner is turned on for heating and the compressor is started, the outdoor ambient temperature, the outdoor coil temperature, the compressor running time, and the outdoor relative humidity are obtained. The dew point temperature is determined based on the outdoor ambient temperature, the outdoor relative humidity, and a preset mapping relationship, wherein the preset mapping relationship includes multiple sets of correspondences between outdoor ambient temperature, outdoor relative humidity, and dew point temperature. The target temperature difference is determined based on the dew point temperature and the outdoor coil temperature. The frost thickness of the air conditioner is determined based on the compressor's operating time and the target temperature difference. Based on the frost thickness, the outdoor ambient temperature, and the compressor's operating time, the air conditioner is controlled to enter the corresponding target defrosting mode, wherein the target defrosting mode includes a micro-frost defrosting mode, a hot air defrosting mode, and a reverse defrosting mode. Wherein, after controlling the air conditioner to enter the micro-frost defrosting mode, the controller is configured to: Based on the target temperature range of the outdoor ambient temperature, the air conditioner is controlled to execute a micro-frost defrosting strategy corresponding to the target temperature range. Different temperature ranges correspond to different micro-frost defrosting strategies, and the conditions for triggering the compressor to reduce its frequency are different under different micro-frost defrosting strategies.

2. The air conditioner with multiple defrosting modes according to claim 1, characterized in that, When determining the frost thickness of the air conditioner based on the compressor's operating time and the target temperature difference, the controller is configured to: The frost thickness of the air conditioner is determined according to the compressor's operating time and the target temperature difference, and according to a preset algorithm, wherein the frost thickness is positively correlated with the target temperature difference and the compressor's operating time. The preset algorithms include: ; Where H represents the frost thickness, t_js represents the compressor running time, △TL represents the target temperature difference, and k is a preset constant.

3. The air conditioner with multiple defrosting modes according to claim 1, characterized in that, Based on the frost thickness, the outdoor ambient temperature, and the compressor's operating time, the controller controls the air conditioner to enter the corresponding target defrosting mode, and the controller is configured to: The continuous operating time of the air conditioner in the micro-frost defrosting mode, the cumulative operating time in the hot air defrosting mode, and the cumulative operating time in the reverse defrosting mode are obtained. When the frost thickness is greater than or equal to the first frost thickness threshold and less than the second frost thickness threshold, and the outdoor ambient temperature is greater than the first outdoor ambient temperature threshold, and the first outdoor ambient temperature threshold is greater than the first preset temperature threshold, and the continuous running time of the micro-frost defrosting mode is greater than or equal to the running time of the compressor, the air conditioner is controlled to enter the micro-frost defrosting mode. When the frost thickness is greater than or equal to the second frost thickness threshold and less than the third frost thickness threshold, and the outdoor ambient temperature is greater than or equal to the second outdoor ambient temperature threshold, and the cumulative running time of the hot air defrosting mode is greater than or equal to the running time of the compressor, the air conditioner is controlled to enter the hot air defrosting mode. When the frost thickness is greater than or equal to the third frost thickness threshold, the air conditioner is controlled to enter the reverse defrosting mode.

4. The air conditioner with multiple defrosting modes according to claim 1, characterized in that, When acquiring the outdoor relative humidity, the controller is configured to: When the air conditioner includes an outdoor humidity sensor and the outdoor humidity sensor is functioning normally, the humidity value detected by the outdoor humidity sensor is taken as the outdoor relative humidity; or... When the air conditioner does not include the outdoor humidity sensor or the air conditioner includes the outdoor humidity sensor but the outdoor humidity sensor is not working properly, the humidity value predicted based on the outdoor ambient temperature, the operating parameters of the air conditioner and the pre-trained humidity prediction model will be used as the outdoor relative humidity.

5. The air conditioner with multiple defrosting modes according to claim 1, characterized in that, When the outdoor relative humidity is determined by using the humidity value predicted based on the outdoor ambient temperature, the air conditioner's operating parameters, and a pre-trained humidity prediction model, the controller is configured as follows: The outdoor relative humidity is updated according to preset update conditions; The preset update conditions include: When the compressor's running time is greater than or equal to the first preset running time, the compressor's running frequency change value and indoor heat exchange temperature difference are acquired every second preset running time, wherein the indoor heat exchange temperature difference is determined based on the difference between the outdoor ambient temperature and the outdoor coil temperature. When the compressor operating frequency change is less than or equal to a preset frequency change value, and the indoor heat exchange temperature difference is less than a preset heat exchange temperature difference threshold, the outdoor relative humidity is updated every second preset operating time; or, The system obtains the heating operation time of the air conditioner in heating mode. When the heating operation time is greater than or equal to a third preset operation time, the outdoor relative humidity is updated every fourth preset operation time; or... When the air conditioner is in a stopped state or enters the corresponding target defrost mode, the update of the outdoor relative humidity is paused; When updating the outdoor relative humidity according to the preset update conditions, the controller is also configured to: When the air conditioner is in an operating state that does not meet the preset update conditions, the outdoor relative humidity is maintained at the humidity value determined when the preset update conditions were met last time, until the operating state of the air conditioner meets the preset update conditions again, at which point the outdoor relative humidity is re-determined and updated.

6. The air conditioner with multiple defrosting modes according to claim 1, characterized in that, The controller is also configured to: If the compressor is starting up for the first time and the compressor’s first start-up time is less than the fifth preset running time, and / or, when the air conditioner enters the corresponding target defrost mode, the prediction of the outdoor relative humidity is paused, and the dew point temperature is determined based on the outdoor relative humidity obtained from the last prediction before the prediction is paused. When the compressor stops and restarts after meeting the shutdown conditions, and the shutdown time of the compressor is less than the sixth preset running time, and the running time after the compressor restarts is less than the fifth preset running time, the dew point temperature is determined based on the outdoor relative humidity before the compressor stops. The shutdown conditions include compressor failure or the compressor reaching the set temperature. If the compressor's downtime is greater than or equal to the sixth preset running time, then the compressor's current start is taken as the first start-up, and the step of taking the compressor as the first start-up is executed.

7. The air conditioner with multiple defrosting modes according to claim 1, characterized in that, Also includes: Indoor coil temperature sensor, used to detect indoor coil temperature; An indoor fan is used to drive indoor air through the indoor heat exchanger by rotation, so that the indoor heat exchanger exchanges heat with the indoor air; An outdoor fan is used to drive outdoor air through the outdoor heat exchanger by rotation, so as to exchange heat with the outdoor heat exchanger by the temperature of the air and defrost the outdoor heat exchanger. A four-way valve is used to switch the flow direction of the refrigerant discharged from the compressor; When controlling the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the controller is configured to: When the outdoor ambient temperature is greater than the second preset temperature threshold and the outdoor ambient temperature is less than or equal to the third preset temperature threshold, the air conditioner is controlled to execute the first micro-frost defrosting strategy. When controlling the air conditioner to execute the first micro-frost defrosting strategy, the controller is configured to: The air conditioner is controlled to enter the first defrosting stage. During the first defrosting stage, the indoor fan is controlled to reduce its speed from the current speed to the target speed corresponding to the current micro-frost defrosting strategy, the four-way valve is controlled to maintain its current reversing state, the compressor is controlled to maintain its current operating frequency, the opening of the expansion valve is controlled to be adjusted to the preset maximum opening, and the outdoor fan is controlled to stop running. The first operating time, the first indoor coil temperature, and the first outdoor coil temperature of the air conditioner during the first defrosting stage are obtained. Based on the first indoor coil temperature, the first outdoor coil temperature, and the first operating time, determine whether the air conditioner meets the first preset condition. If so, control the air conditioner to exit the first defrosting stage and enter the second defrosting stage. The first preset condition includes one of the following: The first runtime reaches the first preset maximum runtime; The temperature of the first indoor coil is less than or equal to a preset minimum indoor coil temperature threshold, and the temperature of the first outdoor coil is greater than or equal to a first preset outdoor coil temperature threshold, and the temperature of the first outdoor coil is less than or equal to a second preset outdoor coil temperature threshold. Upon entering the second defrosting stage, the controller is configured to: The compressor is controlled to reduce its frequency to a first target operating frequency according to a first preset frequency reduction rate. The indoor fan is controlled to maintain a target speed corresponding to the current micro-frost defrosting strategy. The opening of the expansion valve is controlled to maintain the preset maximum opening. The four-way valve is controlled to maintain its current reversing state. The outdoor fan is controlled to operate at a heating operating speed or increase the first preset speed above the heating operating speed. The first target operating frequency is greater than or equal to the preset minimum operating frequency.

8. The air conditioner with multiple defrosting modes according to claim 7, characterized in that, When controlling the air conditioner to execute a micro-frost defrosting strategy corresponding to the target temperature range based on the outdoor ambient temperature, the controller is further configured to: When the outdoor ambient temperature is greater than the third preset temperature threshold, the air conditioner is controlled to execute the second micro-frost defrosting strategy. When controlling the air conditioner to execute the second micro-frost defrosting strategy, the controller is configured to: Control the indoor fan to reduce its current speed to the target speed corresponding to the current micro-frost defrosting strategy, control the four-way valve to maintain its current reversing state, control the compressor to maintain its current operating frequency, control the expansion valve to maintain its current opening degree, and control the outdoor fan to maintain its current speed. The second operating time and the second indoor coil temperature of the air conditioner executing the second micro-frost defrosting strategy are obtained. When the second indoor coil temperature is greater than or equal to the preset maximum indoor coil temperature threshold, or when the second running time reaches the second preset maximum running time, the compressor is controlled to reduce its frequency from the current running frequency to the second target running frequency according to the second preset frequency reduction rate. The outdoor fan is controlled to maintain its current speed or to increase its speed by the second preset speed. The expansion valve is controlled to adjust its opening from the current opening to the preset maximum opening. The indoor fan is controlled to maintain its target speed corresponding to the current micro-frost defrosting strategy. The second preset target frequency is greater than or equal to the preset minimum running frequency.

9. The air conditioner with multiple defrosting modes according to claim 8, characterized in that, The controller is also configured to: During the execution of the first micro-frost defrosting strategy, the second outdoor coil temperature and the third running time of the first micro-frost defrosting strategy are obtained; A first temperature difference threshold is determined based on the outdoor relative humidity and the outdoor ambient temperature; Determine a second temperature difference threshold between the third preset temperature threshold and the first temperature difference threshold; When the air conditioner is determined to meet the first micro-frost defrosting exit condition based on the third running time, the second outdoor coil temperature and the second temperature difference threshold, the air conditioner is controlled to exit the micro-frost defrosting mode. as well as, During the execution of the second micro-frost defrosting strategy, the third outdoor coil temperature and the fourth running time of the second micro-frost defrosting are obtained; When the air conditioner is determined to meet the second defrost exit condition based on the third outdoor coil temperature and the fourth operating time, the air conditioner is controlled to exit the defrost mode. The first micro-frost defrost exit condition includes one of the following: The third runtime reaches the third preset maximum runtime; The temperature of the second outdoor coil is greater than or equal to the second temperature difference threshold, and the third running time reaches the first preset running time; The second micro-cream defrost exit condition includes one of the following: The fourth runtime reaches the fourth preset maximum runtime; The temperature of the third outdoor coil is greater than or equal to the third preset temperature threshold, and the fourth running time reaches the second preset running time. Wherein, after the air conditioner exits the defrosting mode, the controller is configured to: control the compressor to increase its speed according to a preset frequency increase rate, and after a first preset time delay, control the expansion valve, the indoor fan and the outdoor fan to return to the heating operation state; After controlling the air conditioner to exit the defrosting mode, the controller is further configured to: If the time elapsed after the air conditioner exits the micro-frost defrosting mode is less than a preset time, the judgment on entering the reverse defrosting mode is suspended.

10. The air conditioner with multiple defrosting modes according to claim 1, characterized in that, When determining the target temperature difference based on the dew point temperature and the outdoor coil temperature, the controller is configured to: Determine the difference between the dew point temperature and the outdoor coil temperature; When the difference is greater than the fourth preset temperature threshold and the outdoor coil temperature is less than the fourth preset temperature threshold, the difference is taken as the target temperature difference. When the difference is less than or equal to the fourth preset temperature threshold, or when the outdoor coil temperature is greater than or equal to the fourth preset temperature threshold, the target temperature difference is corrected to the fourth preset temperature threshold.

11. A defrosting control method for an air conditioner as described in any one of claims 1-10, characterized in that, include: After the air conditioner is turned on for heating and the compressor starts, the outdoor ambient temperature, outdoor coil temperature, compressor running time, and outdoor relative humidity are obtained. The dew point temperature is determined based on the outdoor ambient temperature, the outdoor relative humidity, and a preset mapping relationship, wherein the preset mapping relationship includes multiple sets of correspondences between outdoor ambient temperature, outdoor relative humidity, and dew point temperature. The target temperature difference is determined based on the dew point temperature and the outdoor coil temperature. The frost thickness of the air conditioner is determined based on the compressor's operating time and the target temperature difference. Based on the frost thickness, the outdoor ambient temperature, and the compressor's operating time, the air conditioner is controlled to enter the corresponding target defrosting mode, wherein the target defrosting mode includes a micro-frost defrosting mode, a hot air defrosting mode, and a reverse defrosting mode. The process of controlling the air conditioner to enter the defrosting mode includes: Based on the target temperature range of the outdoor ambient temperature, the air conditioner is controlled to execute a micro-frost defrosting strategy corresponding to the target temperature range. Different temperature ranges correspond to different micro-frost defrosting strategies, and the conditions for triggering the compressor to reduce its frequency are different under different micro-frost defrosting strategies.

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