Air conditioner defrosting control method and air conditioning system

Abstract

The application relates to an air conditioner defrosting control method and an air conditioner system. The air conditioner system comprises an air conditioner unit. A first outdoor coil temperature is obtained in a heating mode by the air conditioner unit. Whether a defrosting condition is met is judged based on the first outdoor coil temperature. In the case that the defrosting condition is met, whether the air conditioner unit is defrosted is determined according to a continuous defrosting number and an interval time between this time to be defrosted and the previous time to be defrosted. The air conditioner defrosting control method is beneficial to improving the defrosting effect.

Description

Technical Field

[0001] This application relates to the field of rail transit air conditioning technology, and in particular to an air conditioning defrosting control method and air conditioning system. Background Technology

[0002] In winter, when rail transit air conditioning systems are operating for heating, the evaporator surface temperature may drop below 0 degrees Celsius due to the low temperature and high humidity, causing moisture in the air to frost on the air side of the evaporator. This frost can clog the evaporator, reducing airflow and heat exchange efficiency, thus lowering the heating capacity and overall operating efficiency of the air conditioning system. Therefore, defrosting based on the frost buildup on the evaporator is necessary. However, defrosting requires changing the operating mode of the heat pump air conditioner from heating to cooling, which can significantly affect the temperature inside the subway car. To avoid the impact of frequent defrosting on the interior temperature, the inventors have known to minimize the frequency of reverse circulation defrosting or utilize the ventilation mode of the air conditioning unit for defrosting. However, ventilation mode relies solely on natural ventilation for defrosting, which is less effective than reverse circulation defrosting (changing from heating to cooling). This can lead to incomplete frost removal or the frost layer continuously thickening, and even low-pressure faults. Summary of the Invention

[0003] This embodiment provides an air conditioning defrosting control method and air conditioning system, which helps to improve the defrosting effect.

[0004] Firstly, this embodiment provides an air conditioning defrosting control method applied to an air conditioning system of rail transit. The air conditioning system includes an air conditioning unit used to regulate the interior temperature of the rail transit vehicle. The method includes:

[0005] When the air conditioning unit is in heating mode, the first outdoor coil temperature of the air conditioning unit is obtained;

[0006] Determine whether the air conditioning unit meets the defrosting conditions based on the temperature of the first outdoor coil.

[0007] If the defrosting conditions are met, determine whether to defrost the air conditioning unit and modify the number of consecutive defrost cycles based on the interval between the defrosting time and the previous defrosting time.

[0008] When the number of consecutive defrost cycles reaches a first preset number, the air conditioning unit is defrosted, and the number of consecutive defrost cycles is reset to zero.

[0009] In some embodiments, after defrosting the air conditioning unit, the method further includes:

[0010] The temperature of the second outdoor coil of the air conditioning unit during the defrosting process is obtained;

[0011] The temperature of the second outdoor coil is compared with the first preset temperature to determine whether the air conditioning unit meets the conditions for exiting defrosting.

[0012] If the defrosting exit conditions are met, the air conditioning unit is controlled to switch to heating mode.

[0013] In some embodiments, determining whether to defrost the air conditioning unit and modifying the number of consecutive defrost cycles based on the interval between the defrosting time and the previous defrosting includes:

[0014] Obtain the time interval between the defrosting time and the previous defrosting time;

[0015] Determine whether the interval time is less than the continuous running time; if so, do not defrost the air conditioning unit and increment the continuous defrosting count by 1; if not, defrost the air conditioning unit and reset the continuous defrosting count to zero.

[0016] In some embodiments, determining whether to defrost the air conditioning unit and modifying the number of consecutive defrost cycles based on the interval between the defrosting time and the previous defrosting time further includes:

[0017] If the defrosting time corresponds to the first defrosting, the air conditioning unit is defrosted, and the number of consecutive defrostings is incremented by 1.

[0018] In some embodiments, determining whether the air conditioning unit meets the defrosting conditions based on the temperature of the first outdoor coil includes:

[0019] Determine whether the temperature of the first outdoor coil is lower than the second preset temperature;

[0020] If the temperature of the first outdoor coil is lower than the second preset temperature, and the duration of the first outdoor coil temperature being lower than the second preset temperature is greater than the first preset time, the air conditioning unit is determined to meet the defrosting conditions.

[0021] In some embodiments, determining whether the air conditioning unit meets the defrosting exit conditions includes:

[0022] Determine whether the temperature of the second outdoor coil is higher than the first preset temperature;

[0023] If the temperature of the second outdoor coil is higher than the first preset temperature, and the duration of the second outdoor coil temperature being higher than the first preset temperature is greater than the second preset time, the air conditioning unit is determined to meet the defrosting exit condition.

[0024] In some embodiments, the air conditioning unit is used to receive a stop signal from the rail transit system, and the method further includes:

[0025] Determine whether the received stop signal is valid;

[0026] If the stop signal is valid, determine whether the number of consecutive defrost cycles has reached the second preset number;

[0027] When the number of consecutive defrost cycles reaches the second preset number, the third outdoor coil temperature of the air conditioning unit is obtained;

[0028] When the temperature of the third outdoor coil is lower than the third preset temperature, the air conditioning unit is defrosted until the temperature of the third outdoor coil is higher than or equal to the fourth preset temperature, at which point the defrosting process is stopped.

[0029] In some embodiments, determining whether the received stop signal is valid includes:

[0030] Obtain the duration of the stop signal;

[0031] If the duration of the stop signal is greater than a third preset time, the stop signal is determined to be valid.

[0032] In some embodiments, the second preset number of times is less than or equal to the first preset number of times, the third preset temperature is higher than or equal to the second preset temperature, and the fourth preset temperature is higher than or equal to the first preset temperature.

[0033] Secondly, this embodiment provides an air conditioning system for rail transit, the air conditioning system including an air conditioning unit and a control device for defrosting the air conditioning unit using the air conditioning defrosting control method described in the first aspect.

[0034] This embodiment provides an air conditioning defrosting control method and an air conditioning system. The air conditioning system includes an air conditioning unit. When the air conditioning unit is in heating mode, the first outdoor coil temperature is obtained, and based on this temperature, it is determined whether the air conditioning unit meets the defrosting conditions, thus determining whether the air conditioning unit needs to perform reverse-cycle defrosting. If the defrosting conditions are met, the interval between the defrosting time and the previous defrosting time is used to determine whether the air conditioning unit should be defrosted; that is, the interval time is used to determine whether the air conditioning unit enters defrosting mode. When the number of consecutive defrosting cycles reaches a first preset number, the air conditioning unit is defrosted to control the timing of the defrosting cycle, ensuring the heating effect of the air conditioning unit. This air conditioning defrosting control method performs reverse-cycle defrosting while ensuring the heating effect of the air conditioning unit, which helps to improve the defrosting effect. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments of this application and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0036] Figure 1 This is a hardware structure block diagram of two air conditioning units in an air conditioning system according to an embodiment of this application;

[0037] Figure 2 This is a flowchart of an air conditioning defrosting control method according to an embodiment of this application;

[0038] Figure 3 This is a flowchart of an air conditioning defrosting control method for receiving a stop operation signal according to an embodiment of this application;

[0039] Figure 4 This is a flowchart of the air conditioning defrosting control method for subways during normal operation, according to an embodiment of this application. Detailed Implementation

[0040] To better understand the purpose, technical solution, and advantages of this application, the application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0041] Unless otherwise defined, the technical or scientific terms used in this application shall have the general meaning as understood by one of ordinary skill in the art to which this application pertains. Words such as “a,” “an,” “an,” “the,” “the,” and “these,” used in this application, do not indicate quantitative limitation and may be singular or plural. The terms “comprising,” “including,” “having,” and any variations thereof used in this application are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or device that comprises a series of steps or modules (units) is not limited to the listed steps or modules (units) but may include steps or modules (units) not listed, or may include other steps or modules (units) inherent to such processes, methods, products, or devices. The terms “connected,” “linked,” and “coupled,” used in this application, are not limited to physical or mechanical connections but may include electrical connections, whether direct or indirect. The term “multiple” used in this application refers to two or more. The "and / or" operator describes the relationship between related objects, indicating that three relationships can exist. For example, "A and / or B" can represent three cases: A alone, A and B simultaneously, and B alone. Typically, the character " / " indicates that the objects before and after it are in an "or" relationship. The terms "first," "second," and "third," etc., used in this application are merely for distinguishing similar objects and do not represent a specific ordering of the objects.

[0042] The method embodiment provided in this example is applied to the air conditioning system of rail transit, specifically to a subway air conditioning system. A subway consists of multiple carriages, each typically equipped with an independent air conditioning system. Each carriage may have two air conditioning systems; however, as other implementations, the number of air conditioning systems per carriage can also be different, and this is not limited here. In this example, each air conditioning system includes an air conditioning unit and an air conditioning controller or control terminal, computer, or similar computing device for controlling the operating mode of the air conditioning unit. The method embodiment provided in this example can be executed in the air conditioning controller, control terminal, computer, or similar computing device of the rail transit air conditioning system, for example, in the air conditioning controller in this example. The air conditioning controller, or other terminal, computer, etc., running this method embodiment may include one or more processors (processors may include, but are not limited to, microprocessors such as MCUs or programmable logic devices such as FPGAs), a memory for storing data, and a transmission device for communication functions. Optionally, it may also include input / output devices. The memory can be used to store computer programs, such as application software programs and modules, like the computer program corresponding to the air conditioner defrosting control method in this embodiment of the invention. The processor executes various functional applications and data processing by running the computer program stored in the memory, thereby realizing the above-mentioned air conditioner defrosting control method.

[0043] The memory may include high-speed random access memory (RAM) and non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some instances, the memory may further include memory remotely located relative to the processor, which can be connected via a network to an air conditioning controller, or other terminals, computers, etc. Examples of such networks include, but are not limited to, the Internet, intranets, local area networks (LANs), mobile communication networks, and combinations thereof.

[0044] The transmission device is used to receive or send data via a network. Specific examples of the network mentioned above may include an air conditioner controller, or a wireless network provided by a communication provider for other terminals or computers. In one example, the transmission device includes a Network Interface Controller (NIC), which can connect to other network devices via a base station to communicate with the Internet. In another example, the transmission device may be a Radio Frequency (RF) module, used for wireless communication with the Internet.

[0045] The subway air conditioning system is a crucial piece of equipment in subway transportation, providing cooling in summer and heating in winter to maintain a comfortable temperature in the carriages. A typical air conditioning system includes two air conditioning units, whose operating modes can be independently controlled. Understandably, the number of air conditioning units can be adjusted depending on the number of subway trains and the cooling / heating requirements. This embodiment does not impose a limit on the number of air conditioning units.

[0046] Figure 1 This is a hardware structure block diagram of two air conditioning units in an air conditioning system according to this embodiment. (See diagram below.) Figure 1 As shown, each air conditioning unit mainly includes components such as a gas-liquid separator 11, a compressor 12, a four-way valve 13, an evaporator 14, an evaporator fan 15, an electronic expansion valve 16, a condenser 17, and a condenser fan 18. Those skilled in the art will understand that... Figure 1 The connections shown are for illustrative purposes only and do not limit the configuration of the air conditioning unit. For example, other components may be included in the connection pathways of the air conditioning unit. Figure 1 The air conditioning unit and its components shown may also include more than Figure 1 The number shown is more or less, or each component has the same Figure 1 The different configurations shown are illustrated.

[0047] Each air conditioning unit can be started, stopped, and its operating mode can be changed independently. Depending on actual needs, each air conditioning unit can operate in cooling, heating, or ventilation modes. In ventilation mode, the refrigerant circulation of the air conditioning unit stops. When the subway train is not running, the air conditioning unit can be in a stopped state.

[0048] In heating mode, the refrigerant in the gas-liquid separator 11 is compressed into high-pressure vapor by the compressor 12 and discharged. It then flows into the evaporator 14 (which acts as a condenser in heating mode) via the four-way valve 13. The heat released during the condensation of the refrigerant vapor heats the indoor air, achieving indoor heating. The condensed liquid refrigerant, after being throttled by the electronic expansion valve 16, becomes a low-temperature, low-pressure refrigerant and enters the condenser 17 (which acts as an evaporator in heating mode), absorbing heat from the outside and evaporating. The evaporated refrigerant vapor then enters the gas-liquid separator 11 via the four-way valve 13, completing the heating cycle. In cooling mode, the refrigerant flow in the air conditioning unit is reversed compared to the heating cycle. The high-pressure vapor discharged from the compressor 12 flows into the condenser 17 via the four-way valve 13, releasing heat. The condensed liquid refrigerant, after being throttled by the electronic expansion valve 16, enters the evaporator 14, absorbing heat from the indoor air and lowering the indoor temperature. The evaporated refrigerant vapor then enters the gas-liquid separator 11 via the four-way valve 13, completing the cooling cycle.

[0049] This embodiment provides an air conditioning defrosting control method that can be applied to the air conditioning system of rail transit. The air conditioning system includes an air conditioning unit used to regulate the interior temperature of the rail transit train. Figure 2 This is a flowchart of the air conditioner defrosting control method in this embodiment, as shown below. Figure 2 As shown, the process includes the following steps:

[0050] Step S201: When the air conditioning unit is in heating mode, obtain the first outdoor coil temperature of the air conditioning unit.

[0051] The air conditioning defrosting control method of this embodiment can operate when the air conditioning unit is in heating mode. After determining that the air conditioning unit is in heating mode, the temperature of the first outdoor coil of the air conditioning unit is obtained. The first outdoor coil temperature is defined as the temperature of the refrigerant in the coil when the air conditioning is in heating mode. Each air conditioning unit includes at least one outdoor coil, which can be connected to the inlet of the condenser 17. The outdoor coil is the flow channel for the refrigerant, and its temperature reflects the temperature at which the refrigerant enters the condenser 17. During winter heating, when the temperature of the refrigerant entering the condenser 17 (which then acts as an evaporator) is too low, it may cause moisture in the outdoor air to frost on the condenser. The severity of frost formation is related to the refrigerant temperature and the ambient temperature and humidity. A temperature sensor can be installed on the outdoor coil, and the frost condition on the surface of the condenser 17 can be determined based on the refrigerant temperature in the outdoor coil obtained by the temperature sensor.

[0052] Step S202: Determine whether the air conditioning unit meets the defrosting conditions based on the temperature of the first outdoor coil.

[0053] If the temperature of the first outdoor coil of the air conditioning unit meets the preset defrosting temperature threshold, then the air conditioning unit is determined to meet the defrosting conditions.

[0054] Step S203: If the defrosting conditions are met, determine whether to defrost the air conditioning unit and modify the number of consecutive defrost cycles based on the time to defrost and the interval between the defrosting time and the previous defrosting time.

[0055] When the air conditioning unit meets the defrosting conditions based on the temperature of the first outdoor coil, the defrosting time for this defrost and the defrosting time of the previous defrost are obtained, and the interval is obtained by subtracting the two. The number of consecutive defrost cycles can be set and modified according to the execution status of the air conditioning unit's reverse cycle defrosting. If the interval meets the requirements, the air conditioning unit is directly subjected to reverse cycle defrosting. During reverse cycle defrosting, the air conditioning unit is in cooling mode, the condenser releases heat, and the temperature of the condenser and outdoor coil rises, promoting the frost layer to absorb heat from the contact surface with the condenser and melt quickly. Its defrosting effect is better than ventilation defrosting.

[0056] In this embodiment, there are three conditions for performing reverse circulation defrosting on the air conditioning unit, and reverse circulation defrosting can be performed as long as any one of them is met. First, the defrosting to be performed is the first defrosting, therefore the air conditioning unit does not have the problem of frequent defrosting affecting heating performance, and reverse circulation defrosting can be performed immediately. Second, the interval between the current defrosting time and the previous defrosting time meets the continuous operation time requirement, indicating that the air conditioning unit has been heating for a long time, and the impact of reverse circulation defrosting on indoor temperature is small. Third, although the interval does not meet the continuous operation time requirement, the number of consecutive defrostings reaches the first preset number, indicating that the air conditioning unit needs to perform reverse circulation defrosting, and the accumulated number of consecutive defrostings corresponds to a long heating time, so the impact of reverse circulation defrosting on indoor temperature is also small in this case. In these three cases, the impact of reverse circulation defrosting on indoor temperature is small, so execution is allowed, and the number of consecutive defrostings is modified simultaneously.

[0057] Step S204: When the number of consecutive defrosts reaches the first preset number, defrost the air conditioning unit and reset the number of consecutive defrosts to zero.

[0058] When the number of consecutive defrost cycles reaches the first preset number, which is the third situation in step S203 where reverse cycle defrosting is allowed, it indicates that the air conditioning unit needs to perform reverse cycle defrosting. At this time, the air conditioning unit is forced to defrost, the number of consecutive defrost cycles is reset to zero, and the defrosting time can be recorded. The defrosting prompt information and related data indicating that the number of consecutive defrost cycles has reached the first preset number are displayed on the interactive terminal to remind the control personnel whether the defrosting strategy needs to be adjusted.

[0059] Through the above steps S201 to S204, the temperature of the first outdoor coil is obtained when the air conditioning unit is in heating mode, and it is determined whether the air conditioning unit meets the defrosting conditions based on the first outdoor coil temperature, so as to determine whether the air conditioning unit needs to perform reverse circulation defrosting; if the defrosting conditions are met, it is determined whether to defrost the air conditioning unit based on the interval between the defrosting time and the previous defrosting, that is, the interval time is used to determine whether the air conditioning unit enters defrosting; if the number of consecutive defrosting reaches the first preset number, the air conditioning unit is forced to defrost and the number of consecutive defrosting is reset to zero, the timing of the air conditioning unit entering defrosting is controlled to ensure the heating effect of the air conditioning unit, and the defrosting effect is enhanced by forced reverse circulation defrosting.

[0060] In some embodiments, after defrosting the air conditioning unit, a process is also involved to determine whether the conditions for exiting defrosting are met. This process includes the following steps:

[0061] Step S11: Obtain the temperature of the second outdoor coil of the air conditioning unit during the defrosting process.

[0062] During reverse-cycle defrosting, the condenser and outdoor coil temperatures rise. Therefore, it's necessary to obtain the temperature of the second outdoor coil during the defrosting process to assess the defrosting effectiveness. The second outdoor coil temperature refers to the temperature of the same outdoor coil read again. This second outdoor coil temperature is typically higher than the first outdoor coil temperature before defrosting.

[0063] Step S12: Compare the temperature of the second outdoor coil with the first preset temperature to determine whether the air conditioning unit meets the conditions for exiting defrosting.

[0064] Exiting defrost means the air conditioning unit stops reverse-cycle cooling and returns to heating mode. The condition for exiting defrost is that the temperature of the second outdoor coil is higher than a preset first temperature. The first preset temperature is the exit defrost temperature threshold, which should be higher than the entry defrost temperature threshold in the defrost conditions. If the second outdoor coil temperature is higher than the first preset temperature, it indicates that defrosting has achieved the expected effect, and the frost layer is basically completely removed, so the reverse-cycle defrost mode can be ended. If the second outdoor coil temperature is lower than or equal to the first preset temperature, it indicates that the frost layer has not been completely removed, and continuous defrosting is required. The second outdoor coil temperature should be monitored at intervals or in real-time to determine whether to exit defrost.

[0065] Step S13: If the defrosting exit conditions are met, control the air conditioning unit to switch to heating mode.

[0066] If the temperature of the second outdoor coil is higher than the defrost exit temperature, meaning the air conditioning unit meets the defrost exit conditions, the air conditioning unit will resume normal heating mode.

[0067] Through the above steps S11 to S13, by setting the defrost exit conditions, the frost situation during the defrost process of the air conditioning unit is determined. If the temperature of the second outdoor coil during the defrost process meets the defrost exit conditions, the reverse cycle defrost mode ends and heating resumes.

[0068] In some embodiments, a process is involved in determining whether to defrost the air conditioning unit and modifying the number of consecutive defrost cycles based on the interval between the defrost time and the previous defrost. This process includes the following steps:

[0069] Step S21: Obtain the time to defrost and the interval between the previous defrost.

[0070] Record the start or end time of each defrost. The defrosting time refers to the time to perform this defrost, which is the time to subtract the end time of the previous defrost as the interval.

[0071] Step S22: Determine whether the interval time is less than the continuous running time; if so, do not defrost the air conditioning unit and increment the continuous defrosting count by 1; if not, defrost the air conditioning unit and reset the continuous defrosting count to zero.

[0072] Continuous operating time refers to the duration during which the air conditioning unit is in heating mode. Without a set continuous operating time, the air conditioning unit may repeatedly switch between heating and cooling modes in a short period, affecting not only the heating effect and passenger comfort in the subway car but also the operating condition and lifespan of the air conditioning unit's compressor. Therefore, a minimum permissible heating time for the air conditioning unit can be set as the continuous operating time.

[0073] The interval time is compared with the continuous operating time. If the interval time is less than the continuous operating time, it indicates that the air conditioning unit's continuous heating time is short. Performing reverse circulation defrosting would affect the heating effect, so defrosting is not performed. However, the continuous defrosting count needs to be incremented by 1 to accumulate the defrosting demand. In this embodiment, the continuous operating time can be set to 20 minutes, or it can be set according to the actual situation. If the interval time is greater than or equal to the continuous operating time, it indicates that the air conditioning unit's continuous heating time has met the continuous operating time condition. Performing reverse circulation defrosting now has little impact on the indoor temperature, so the air conditioning unit can be defrosted, and the continuous defrosting count is reset to zero to indicate that the defrosting demand has been responded to.

[0074] Through the above steps S21 to S22, by judging whether the interval time is less than the continuous running time, it is determined whether the air conditioning unit should be defrosted. If the interval time is less than the continuous running time, the air conditioning unit is not defrosted, and the continuous defrosting count is incremented by 1; if the interval time is greater than or equal to the continuous running time, the air conditioning unit is defrosted, and the continuous defrosting count is reset to zero. This establishes the counting method for the continuous defrosting count and the relationship between the continuous defrosting count and the interval time. The continuous defrosting count is used to measure whether the timing of defrosting the air conditioning unit is reasonable, providing a basis for judgment to ensure the normal working state of the air conditioning unit compressor.

[0075] In some embodiments, a method is involved in determining whether to defrost the air conditioning unit and modifying the number of consecutive defrost cycles based on the interval between the defrosting time and the previous defrost cycle. The method includes: defrosting the air conditioning unit if the defrosting time corresponds to the first defrost cycle, and incrementing the number of consecutive defrost cycles by 1.

[0076] The defrosting time of each air conditioning unit can be recorded through system information. The recorded defrosting time can determine whether this is the first defrosting cycle. If this is the first defrosting cycle for the air conditioning unit, the continuous heating time cannot be determined based on the interval between previous defrost cycles. However, it can be determined that the air conditioning unit does not have a problem where frequent defrosting affects heating performance. Therefore, reverse cycle defrosting can be performed this time, but the continuous defrosting count needs to be incremented by 1 to accumulate the defrosting count.

[0077] In some embodiments, a process is involved in determining whether an air conditioning unit meets defrosting conditions based on a first outdoor coil temperature. This process includes the following steps:

[0078] Step S31: Determine whether the temperature of the first outdoor coil is lower than the second preset temperature.

[0079] When the temperature of the first outdoor coil of the air conditioning unit is lower than a certain temperature, it indicates that the temperature of the air conditioner condenser corresponding to that outdoor coil is low and there is frost buildup, requiring defrosting. This can be determined by a preset defrosting temperature threshold, i.e., the second preset temperature, which serves as a prerequisite for initiating reverse-cycle defrosting. This fourth preset temperature can be adjusted according to actual operating conditions, mainly depending on the local winter temperature and humidity environment. Generally, it can be set to -15℃ to -18℃.

[0080] Step S32: If the temperature of the first outdoor coil is lower than the second preset temperature, and the duration of the first outdoor coil temperature being lower than the second preset temperature is greater than the first preset time, it is determined that the air conditioning unit meets the defrosting conditions.

[0081] To avoid incorrect readings of the first outdoor coil temperature, or readings that fall within the threshold of the second preset temperature, causing the air conditioning unit to repeatedly enter and exit reverse-cycle defrosting mode, it is necessary to confirm the first outdoor coil temperature. This can typically be done by repeatedly reading the sensor temperature to avoid sensor reading errors; alternatively, the duration for which the first outdoor coil temperature remains below the second preset temperature can be used to determine if defrosting is possible. In this embodiment, the defrosting condition is determined by reading the first outdoor coil temperature and checking if the duration of this temperature being below the second preset temperature exceeds a first preset time. The first preset time can be set to 60s–120s and can be adjusted according to actual needs.

[0082] Through the above steps S31 to S32, by using whether the temperature of the first outdoor coil is lower than the fourth preset temperature as the criterion for meeting the defrosting conditions, the specific conditions and judgment methods for starting reverse cycle defrosting are given; by using the duration for which the temperature of the first outdoor coil is lower than the fourth preset temperature as a supplementary criterion for meeting the defrosting conditions, the situation of incorrect outdoor coil temperature reading or the reading temperature not being stably maintained below the fourth preset temperature is avoided, thereby avoiding the air conditioning unit repeatedly switching between entering and exiting the reverse cycle defrosting state, which affects the heating and defrosting effects of the air conditioning unit, as well as the working status and service life of the compressor.

[0083] In some embodiments, a process is involved in determining whether an air conditioning unit meets the conditions for exiting defrosting. This process includes the following steps:

[0084] Step S41: Determine whether the temperature of the second outdoor coil is higher than the first preset temperature.

[0085] Step S42: If the temperature of the second outdoor coil is higher than the first preset temperature, and the duration of the second outdoor coil temperature being higher than the first preset temperature is greater than the second preset time, it is determined that the air conditioning unit meets the conditions for exiting defrosting.

[0086] To avoid erroneous readings of the second outdoor coil temperature, or readings that fall within the critical value of the first preset temperature, causing the air conditioning unit to repeatedly enter and exit reverse defrost mode, it is necessary to confirm the second outdoor coil temperature. This can typically be done by repeatedly reading the sensor temperature to avoid sensor reading errors; alternatively, the duration for which the second outdoor coil temperature remains above the first preset temperature can be used to determine whether defrosting can be discontinued. In this embodiment, the discontinuation of defrost is determined by reading the second outdoor coil temperature and checking whether the duration for which this temperature remains below the first preset temperature exceeds a second preset time. The second preset time can be adjusted according to actual needs.

[0087] Through the above steps S41 to S42, the defrosting exit conditions are set by the first preset temperature and the second preset time. When the defrosting exit conditions are met, the defrosting ends and heating resumes, further ensuring the heating effect of the air conditioning unit.

[0088] In some of these embodiments, the air conditioning unit is used to receive a stop signal from a rail transit train. Figure 3 This is a flowchart of the air conditioning defrosting control method for receiving a stop signal in this embodiment, as shown below. Figure 3 As shown, upon receiving a stop signal, the process includes the following steps:

[0089] Step S301: Determine whether the received stop signal is valid.

[0090] After a subway train reaches its final stop, there are no passengers in the carriages. Therefore, performing reverse-circulation defrosting on the air conditioning units will not affect passenger comfort. Thus, a more thorough defrosting can be performed after the train has stopped running. After the subway train stops, the driver removes the key from the cab, sends a stop signal, and transmits this signal to the air conditioning units via the network. This stop signal can be a switching signal. To avoid misinterpretation, the air conditioning units should first verify the validity of the stop signal upon receiving it.

[0091] Step S302: If the stop signal is valid, determine whether the number of consecutive defrost cycles has reached the second preset number.

[0092] Before the subway stops operating, the air conditioning units may have defrosted several times, and the number of consecutive defrost cycles is recorded. If the number of consecutive defrost cycles is zero, it means that the air conditioning units did not defrost before the subway stopped operating, or defrosting had just ended, indicating that there is no frost buildup or the frost layer is thin, and therefore reverse circulation defrosting is not required. If the number of consecutive defrost cycles reaches a second preset number, which can be less than or equal to the first preset number, it indicates that the air conditioning units have significant frost buildup, and reverse circulation defrosting can be performed even when the subway is stopped. If the second preset number is less than the first preset number, it means that the conditions for performing reverse circulation defrosting while the subway is stopped are more lenient.

[0093] Step S303: When the number of consecutive defrost cycles reaches the second preset number, the third outdoor coil temperature of the air conditioning unit is obtained.

[0094] Step S304: If the temperature of the third outdoor coil is lower than the third preset temperature, defrost the air conditioning unit until the temperature of the third outdoor coil is higher than or equal to the fourth preset temperature and then exit defrosting.

[0095] The third preset temperature can be higher than or equal to the second preset temperature (i.e., the defrosting temperature threshold). A higher third preset temperature allows for more lenient defrosting conditions, enabling defrosting to begin as soon as frost forms, or even preventing frost formation altogether. Since reverse-cycle defrosting does not affect passenger comfort when the unit is parked, the defrosting conditions can be set relatively leniently. Reverse-cycle defrosting is performed when the temperature of the third outdoor coil is lower than the third preset temperature. During defrosting, the temperature of the third outdoor coil is acquired at intervals or in real-time. This temperature represents the temperature of the refrigerant inside the coil during the defrosting process. As the third outdoor coil temperature rises, it is compared to the fourth preset temperature. The fourth preset temperature can be equal to the first preset temperature, i.e., the same as the defrosting exit condition under normal rail transit operation; the fourth preset temperature can also be higher than the first preset temperature. A higher fourth preset temperature results in stricter defrosting exit conditions, achieving a more thorough defrosting effect. When the temperature of the third outdoor coil is higher than or equal to the fourth preset temperature, it indicates that the frost on the air conditioning unit has been completely cleared, and defrosting can be terminated.

[0096] Through the above steps S301 to S304, when the subway is not running, the current frosting status of the air conditioning unit is determined by checking whether the current number of consecutive defrosting cycles has reached the second preset number; the air conditioning unit is defrosted by comparing the third outdoor coil temperature with the third preset temperature; and the defrosting is exited by comparing the third outdoor coil temperature with the fourth preset temperature. Thus, when the rail transit is not running, the air conditioning unit is subjected to enhanced defrosting by setting the entry and exit conditions for defrosting.

[0097] In some embodiments, a process is involved in determining whether a received stop signal is valid. This process includes the following steps:

[0098] Step S51: Obtain the duration of the stop signal.

[0099] To avoid misinterpretation of stop signals leading to incorrect defrosting status switching, the validity of stop signals should be determined. Based on the actual operation of rail transit, the validity of a stop signal can be judged by its duration.

[0100] Step S52: If the duration of the stop signal is greater than the second preset time, the stop signal is determined to be valid.

[0101] The second preset time can usually be set to 30s to 180s, and can be adjusted according to the actual situation.

[0102] By using steps S51 to S52 above, the duration of the stop operation signal is used as the criterion for determining whether the stop operation signal is valid, thus avoiding misjudgment that could lead to incorrect switching of the defrost state, which would affect the heating and defrosting effects of the air conditioning unit, as well as the working status and service life of the compressor.

[0103] The following describes and illustrates this embodiment using an example of rail transit under normal operating conditions.

[0104] Figure 4 This is a flowchart illustrating a method for controlling the defrosting of an air conditioner during normal subway operation, as described in an embodiment of this application. Figure 4 As shown, the air conditioner defrosting control method includes the following steps:

[0105] Step S401: Obtain the temperature of the first outdoor coil of the air conditioning unit;

[0106] Step S402: Determine whether the temperature of the first outdoor coil is lower than the second preset temperature;

[0107] In this embodiment, the second preset temperature can be -15℃ to -18℃.

[0108] Step S403: If the temperature of the first outdoor coil is lower than the second preset temperature, determine whether the duration of the first outdoor coil temperature being lower than the second preset temperature is greater than the first preset time.

[0109] In this embodiment, the first preset time can be 60s to 120s.

[0110] Step S404: If the duration is greater than the first preset time, determine whether the defrosting time is the first defrosting. If so, defrost the air conditioning unit and increment the recorded number of consecutive defrostings by 1.

[0111] Step S405: If it is determined that the defrosting time to be defrosted is not the first defrosting, obtain the interval between the current defrosting time and the previous defrosting time.

[0112] In step S406, if the interval time is less than the preset continuous running time, proceed to step S407; if the interval time is greater than or equal to the continuous running time, proceed to step S409.

[0113] In this embodiment, the continuous running time is set to 20 minutes.

[0114] Step S407: Do not defrost the air conditioning unit this time; increment the recorded number of consecutive defrosts by 1.

[0115] Step S408: Determine whether the number of consecutive defrosting cycles of the air conditioning unit has reached the first preset number; if it has, proceed to step S409; otherwise, end the process.

[0116] In this embodiment, the first preset number of times is 3.

[0117] Step S409: The unit to be defrosted enters the defrosting mode to defrost the air conditioning unit, and at the same time, the number of consecutive defrost counts is reset to 0.

[0118] Step S410: Obtain the temperature of the second outdoor coil of the air conditioning unit during the defrosting process;

[0119] Step S411: Compare the temperature of the second outdoor coil with the first preset temperature to determine whether the temperature of the second outdoor coil is higher than the first preset temperature.

[0120] In this embodiment, the first preset temperature can be -7℃ to -12℃, or it can be adjusted according to the actual situation.

[0121] Step S412: If the temperature of the second outdoor coil is higher than the first preset temperature, exit the defrost mode and control the air conditioning unit to switch to the heating mode.

[0122] Through the above steps S401 to S412, this embodiment determines whether the air conditioning unit meets the defrosting conditions by obtaining the temperature of the first outdoor coil. If the defrosting conditions are met, it determines whether it is the first defrosting. If so, defrosting is performed and the count is reset. If it is not the first defrosting, it determines whether the interval time with the previous one meets the continuous running time condition. If the condition is met, defrosting is performed and the count is reset to zero. If the condition is not met, defrosting is not performed and the count is reset. When the number of consecutive defrostings reaches the first preset number, forced defrosting is performed and the count is reset to zero. That is, when the interval time does not meet the requirements, the defrosting frequency is adjusted by recording the number of consecutive defrostings. After reaching the first preset number, forced defrosting is performed. The second outdoor coil temperature after defrosting is obtained to determine whether the air conditioning unit meets the conditions for exiting defrosting to ensure the defrosting effect. This provides a method for reverse cycle defrosting when the defrosting interval time does not meet the requirements, and can adjust the first preset number in time when defrosting is frequent, avoiding adverse effects on the working state of the air conditioning unit compressor.

[0123] Furthermore, when determining whether to exit the defrost mode in step S411, it is easy to see that, similar to determining whether the defrost conditions are met, the duration for which the temperature of the second outdoor coil is higher than the first preset temperature is greater than the second preset time can be added to improve the accuracy of the determination to exit the defrost mode. Specifically, the second preset time can be set to 60s to 120s, or it can be adjusted according to actual needs.

[0124] It should be noted that the steps shown in the above process or in the flowchart of the accompanying figures can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0125] This embodiment also provides an air conditioning system for rail transit, which includes an air conditioning unit and an air conditioning defrosting control device for defrosting the air conditioning unit using any of the air conditioning defrosting control methods described in the above embodiments.

[0126] The air conditioning system for rail transit provided in this embodiment uses an air conditioning defrosting control device to determine whether each air conditioning unit in heating mode meets the defrosting conditions, thus determining whether the unit needs to undergo reverse-cycle defrosting. If the defrosting conditions are met, the system determines whether to defrost the unit based on the interval between the defrosting time and the previous defrosting, i.e., the interval time is used to determine whether the unit enters defrosting mode. If the number of consecutive defrosting cycles reaches a first preset number, forced defrosting is performed on the unit, and the consecutive defrosting count is reset to zero. This controls the timing of the unit entering defrosting mode, ensuring the heating effect of the air conditioning unit, and enhancing the defrosting effect through forced reverse-cycle defrosting. Furthermore, in conjunction with the air conditioning defrosting control method provided in the above embodiment, this embodiment can also provide a storage medium. This storage medium stores a computer program; when executed by a processor, this computer program implements any of the air conditioning defrosting control methods in the above embodiments.

[0127] It should be understood that the specific embodiments described herein are merely illustrative of the application and not intended to limit it. All other embodiments derived by those skilled in the art based on the embodiments provided in this application without inventive effort are within the scope of protection of this application.

[0128] Obviously, the accompanying drawings are merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar situations based on these drawings without any creative effort. Furthermore, it is understood that although the work done in this development process may be complex and lengthy, for those skilled in the art, certain design, manufacturing, or production modifications made based on the technical content disclosed in this application are merely conventional technical means and should not be considered as insufficient disclosure of this application.

[0129] The term "embodiment" in this application refers to a specific feature, structure, or characteristic described in connection with an embodiment that may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily imply the same embodiment, nor does it imply that it is mutually exclusive with or independent of other embodiments. It will be clearly or implicitly understood by those skilled in the art that the embodiments described in this application may be combined with other embodiments without conflict.

[0130] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of patent protection. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. An air conditioning defrosting control method, applied to an air conditioning system of rail transit, the air conditioning system comprising an air conditioning unit, the air conditioning unit being used to regulate the interior temperature of the rail transit vehicle, characterized in that, The method includes: When the air conditioning unit is in heating mode, the first outdoor coil temperature of the air conditioning unit is obtained; Determine whether the temperature of the first outdoor coil is lower than the second preset temperature; if the temperature of the first outdoor coil is lower than the second preset temperature, and the duration of the first outdoor coil temperature being lower than the second preset temperature is greater than the first preset time, determine that the air conditioning unit meets the defrosting conditions. If the defrosting conditions are met, the interval between the time to be defrosted and the previous defrosting is obtained, and it is determined whether the interval is less than the set continuous operating time; the continuous operating time is the minimum heating time allowed for the air conditioning unit. If the interval time is less than the continuous running time, the air conditioning unit will not be defrosted. The recorded number of consecutive defrosts will be incremented by 1, and it will be determined whether the number of consecutive defrosts has reached the first preset number. If it has, the current defrost will enter the defrost mode and the air conditioning unit will be defrosted. The number of consecutive defrosts is used to accumulate the defrost demand. If the interval time is greater than or equal to the continuous operating time, then the air conditioning unit is defrosted. After performing a defrost operation on the air conditioning unit, the number of consecutive defrost cycles is reset to zero.

2. The method according to claim 1, characterized in that, After defrosting the air conditioning unit, the method further includes: The temperature of the second outdoor coil of the air conditioning unit during the defrosting process is obtained; The temperature of the second outdoor coil is compared with the first preset temperature to determine whether the air conditioning unit meets the conditions for exiting defrosting. If the defrosting exit conditions are met, the air conditioning unit is controlled to switch to heating mode.

3. The method according to claim 1, characterized in that, The method further includes: If the defrosting time corresponds to the first defrosting, the air conditioning unit is defrosted, and the number of consecutive defrostings is incremented by 1.

4. The method according to claim 2, characterized in that, Determining whether the air conditioning unit meets the conditions for exiting defrosting includes: Determine whether the temperature of the second outdoor coil is higher than the first preset temperature; If the temperature of the second outdoor coil is higher than the first preset temperature, and the duration of the second outdoor coil temperature being higher than the first preset temperature is greater than the second preset time, the air conditioning unit is determined to meet the defrosting exit conditions.

5. The method according to claim 4, characterized in that, The air conditioning unit is used to receive the stop signal of the rail transit, and the method further includes: Determine whether the received stop signal is valid; If the stop signal is valid, determine whether the number of consecutive defrost cycles has reached the second preset number; When the number of consecutive defrost cycles reaches the second preset number, the third outdoor coil temperature of the air conditioning unit is obtained; When the temperature of the third outdoor coil is lower than the third preset temperature, the air conditioning unit is defrosted until the temperature of the third outdoor coil is higher than or equal to the fourth preset temperature, at which point the defrosting process is stopped.

6. The method according to claim 5, characterized in that, Determining whether the received stop signal is valid includes: Obtain the duration of the stop signal; If the duration of the stop signal is greater than a third preset time, the stop signal is determined to be valid.

7. The method according to claim 5 or 6, characterized in that, The second preset number of times is less than or equal to the first preset number of times, the third preset temperature is higher than or equal to the second preset temperature, and the fourth preset temperature is higher than or equal to the first preset temperature.

8. An air conditioning system for rail transit, characterized in that, The air conditioning system includes an air conditioning unit and a control device for defrosting the air conditioning unit using the air conditioning defrosting control method according to any one of claims 1-7.

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