Inverter air conditioner

Abstract

The present invention discloses a variable frequency air conditioner, comprising: an outdoor unit, which at least has a compressor, an outdoor fan and a first heat exchanger; an indoor unit, which at least has a second heat exchanger; an expansion valve, and a controller, which is configured to judge whether to enter or exit a low-temperature refrigeration mode or an ultra-low-temperature heating mode according to temperature data and an operation mode, and is also configured to control the compressor, the outdoor fan and the expansion valve to execute a low-temperature refrigeration command or an ultra-low-temperature heating command. The present invention can simultaneously overcome the problem of poor reliability during the startup of the refrigeration mode and the ultra-low-temperature heating mode under a low-temperature environment, and can prevent the poor startup reliability of the air conditioner caused by the slow establishment of low pressure in the low-temperature refrigeration mode, and can also avoid the occurrence of factors that affect the reliability of the air conditioner, such as liquid hammer and oil-free operation in the ultra-low-temperature heating mode, so that the variable frequency air conditioner can achieve stable startup and operation under extreme working conditions.

Description

Technical Field

[0001] The present invention relates to the field of refrigeration technology, and in particular to a variable frequency air conditioner. Background Art

[0002] Cooling in summer and heating in winter are the most basic requirements for variable frequency air conditioners, while more and more differentiated demands such as cooling in winter and ultra-low temperature heating are being proposed. When the air conditioner is operating under extreme conditions, it must not only maintain the cooling and heating effects, but also meet the requirements of long-term stable startup and operation. In ultra-high temperature environments, the air conditioner mainly operates for cooling, and in ultra-low temperature environments, it mainly operates for heating. In the transition season, it may operate for cooling or heating. The air conditioner will face different problems when operating in these three environmental states, which not only poses severe challenges to the performance of the air conditioner, but also its reliability is a technical problem that needs to be solved urgently, and startup reliability is the most important part of reliable operation.

[0003] The existing patent CN106705362A discloses a low-temperature refrigeration control method, a controller and an air conditioner, and specifically discloses that in the low-temperature refrigeration method, by obtaining the indoor and outdoor temperatures and the set temperature of the air conditioner, the compressor operating frequency and the external fan speed in the low-temperature refrigeration control mode are determined, thereby controlling the compressor and the external fan. Multiple compressor preset operating frequency ranges and multiple external fan speed ranges are disclosed, wherein a higher frequency range corresponds to a higher fan speed; the opening of the expansion valve is also disclosed, wherein a higher frequency range corresponds to a larger opening range. However, its control quantity is relatively single and cannot overcome the problem of startup reliability.

[0004] In summary, there is an urgent need to design a variable frequency air conditioner that can ensure the stability of the air conditioner during the startup phase under extreme working conditions. Summary of the invention

[0005] The present invention provides a variable frequency air conditioner, which can solve the problems of poor reliability and high energy consumption of air conditioners in the prior art under extreme working conditions. The specific scheme is as follows:

[0006] Inverter air conditioner, comprising:

[0007] An outdoor unit having at least a compressor, an outdoor fan and a first heat exchanger;

[0008] an indoor unit having at least a second heat exchanger;

[0009] expansion valve, and

[0010] A controller configured to determine whether to enter or exit a low-temperature cooling mode or an ultra-low-temperature heating mode according to temperature data and an operation mode,

[0011] The system is further configured to control the compressor, the outdoor fan and the expansion valve to execute a low-temperature cooling command or an ultra-low-temperature heating command;

[0012] The temperature data includes the outdoor ambient temperature To, the indoor ambient temperature Ti, the outdoor coil temperature Toc, the indoor coil temperature Tic, and the discharge temperature Tdis.

[0013] In some embodiments of the present invention, the entry determination conditions for the low-temperature refrigeration mode include that the variable-frequency air conditioner is in the refrigeration mode or the dehumidification mode, the outdoor ambient temperature To < T1, and the outdoor coil temperature Toc < T2. When the above determination conditions are all satisfied and the maintenance time is greater than t1, the controller is configured to adjust the variable-frequency air conditioner to enter the low-temperature refrigeration mode; wherein, both T1 and T2 are thresholds of the temperature data built in the controller.

[0014] In some embodiments of the present invention, the low-temperature refrigeration command includes: narrowing the operating range of the expansion valve, increasing the minimum operating frequency of the compressor, and controlling the rotational speed of the outdoor fan according to the outdoor coil temperature Toc. The rotational speed range of the outdoor fan is (FANl, FANm); the target value range of the outdoor coil temperature Toc is (TocG, TocH).

[0015] In some embodiments of the present invention, the controller is configured to:

[0016] When the outdoor coil temperature Toc is less than the target value, the controller adjusts the outdoor fan to reduce the rotational speed; when the outdoor coil temperature Toc is greater than the target value, the controller adjusts the outdoor fan to increase the rotational speed; when the outdoor coil temperature Toc < 0°C, the controller adjusts the rotational speed of the outdoor fan to FANl; when the outdoor coil temperature Toc < -10°C, the controller adjusts the outdoor fan to shut down.

[0017] In some embodiments of the present invention, the exit determination conditions for the low-temperature refrigeration mode include: the variable-frequency air conditioner is switched to the shutdown state, the variable-frequency air conditioner is in a non-refrigeration mode or a non-dehumidification mode, the outdoor ambient temperature To > T3, and the outdoor coil temperature Toc > T4. When any of the above determination conditions is satisfied and the maintenance time is greater than t2, the controller is configured to adjust the variable-frequency air conditioner to exit the low-temperature refrigeration mode; wherein, both T3 and T4 are thresholds of the temperature data built in the controller.

[0018] In some embodiments of the present invention, the entry determination conditions for the ultra-low-temperature heating mode include:

[0019] When the variable frequency air conditioner is powered on for the first time or the compressor stops for more than 1 hour after power-on and the outdoor ambient temperature To≤T5, if the outdoor ambient temperature To>0℃ and Tdis-To≤∆T1, the controller is configured to adjust the variable frequency air conditioner to enter an ultra-low temperature heating mode; if the outdoor ambient temperature To≤0℃ and Tdis≤T6, the controller is configured to adjust the variable frequency air conditioner to enter an ultra-low temperature heating mode; wherein T5 and T6 are both thresholds of the temperature data built into the controller.

[0020] In some embodiments of the present invention, the ultra-low temperature heating instruction includes refrigerant migration, mode transition, and heating mode in sequence; the controller is configured to: adjust the variable frequency air conditioner to perform mode transition according to the judgment condition of the completion of refrigerant migration, and adjust the variable frequency air conditioner to enter the heating mode when the maintenance time of the mode transition is greater than t.

[0021] In some embodiments of the present invention, the refrigerant migration instruction includes:

[0022] The controller is configured to adjust the expansion valve to operate at an opening degree [X], where [X] is the middle value of the expansion valve opening range, adjust the outdoor fan to operate at a speed FANl, and adjust the compressor to operate at a frequency [FREQ], where [FREQ] is the middle value of the compressor operating frequency range.

[0023] In some embodiments of the present invention, the mode transition instruction includes:

[0024] The controller is configured to adjust the compressor to reduce the operating frequency, power on the four-way valve when the operating frequency is less than 40 Hz, adjust the expansion valve to maintain the opening degree [Xfix] for time t4, and adjust the outdoor fan to operate at a speed of [FANh] for time t5, where [FANh] is the maximum value of the speed range of the outdoor fan.

[0025] In some embodiments of the present invention, the heating mode instruction includes:

[0026] The controller is configured to adjust the compressor to continue to increase or decrease the frequency according to the target frequency, adjust the speed of the outdoor fan to perform PID control according to the outdoor coil temperature Toc, and adjust the expansion valve to perform fuzzy control according to the exhaust superheat.

[0027] In some embodiments of the present invention, the determination conditions for completion of refrigerant migration include:

[0028] The difference between the outdoor coil temperature Toc and the indoor coil temperature Tic is not less than ∆T2, the outdoor coil temperature Toc≥T7, and the compressor operation time>t3. When any of the above judgment conditions is met, the controller is configured to send a mode transition instruction, wherein T7 is the threshold value of the temperature data built into the controller.

[0029] In some embodiments of the present invention, several temperature sensors are also included, including a first temperature sensor and a second temperature sensor arranged on the first heat exchanger for collecting the outdoor ambient temperature To and the outdoor coil temperature Toc, a third temperature sensor arranged on the compressor for collecting the exhaust temperature Tdis, and a fourth temperature sensor and a fifth temperature sensor arranged on the second heat exchanger for collecting the indoor ambient temperature Ti and the indoor coil temperature Tic.

[0030] The present invention has the following beneficial effects:

[0031] The present invention can simultaneously overcome the problem of poor reliability during the startup of the cooling mode and the ultra-low temperature heating mode under low temperature environment, and can prevent the poor startup reliability of the air conditioner caused by the slow low pressure build-up in the low temperature cooling mode, and can also avoid the occurrence of factors that affect the reliability of the air conditioner such as liquid hammer and oil-free operation in the ultra-low temperature heating mode. This enables the variable frequency air conditioner to achieve stable startup and operation under extreme working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the circulation of a refrigerant in a low-temperature refrigeration mode according to some embodiments is shown;

[0033] Figure 2 A schematic diagram of the circulation of refrigerant in an ultra-low temperature heating mode according to some embodiments is shown;

[0034] Figure 3 The relationship between the outdoor fan speed and the outdoor coil temperature according to some embodiments is shown Figure 1 ;

[0035] Figure 4 The relationship between the outdoor fan speed and the outdoor coil temperature according to some embodiments is shown Figure 2 ;

[0036] Figure 5 shows a control timing diagram of the compressor frequency in the ultra-low temperature heating mode according to some embodiments;

[0037] Figure 6 shows a control timing diagram of the four-way valve state in the ultra-low temperature heating mode according to some embodiments;

[0038] Figure 7shows a control timing diagram of the expansion valve opening in the ultra-low temperature heating mode according to some embodiments;

[0039] Figure 8 shows a control timing diagram of the outdoor fan speed in the ultra-low temperature heating mode according to some embodiments;

[0040] Fig. 9 A control timing relationship diagram of the compressor frequency and the four-way valve state in the ultra-low temperature heating mode according to some embodiments is shown.

[0041] Figure numerals: 100 - compressor; 200 - first heat exchanger; 300 - second heat exchanger; 400 - electronic expansion valve; 500 - four-way valve; 600 - stop valve; 710 - first temperature sensor; 720 - second temperature sensor; 730 - third temperature sensor; 740 - fourth temperature sensor; 750 - fifth temperature sensor. DETAILED DESCRIPTION

[0042] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0044] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0045] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0046] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0047] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0048] The air conditioner of the present invention performs a refrigeration cycle of the air conditioner by using a compressor, a condenser, an expansion valve and an evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion and evaporation to cool or heat the indoor space.

[0049] The low-temperature and low-pressure refrigerant enters the compressor, which compresses it into high-temperature and high-pressure refrigerant gas and discharges the compressed refrigerant gas. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.

[0050] The expansion valve expands the high-temperature and high-pressure liquid refrigerant condensed in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the low-temperature and low-pressure refrigerant gas to the compressor. The evaporator can achieve a cooling effect by utilizing the latent heat of evaporation of the refrigerant to exchange heat with the material to be cooled. In the entire cycle, the air conditioner can adjust the temperature of the indoor space.

[0051] The outdoor unit of the air conditioner refers to a portion of a refrigeration cycle including a compressor and an outdoor heat exchanger, the indoor unit of the air conditioner includes an indoor heat exchanger, and an expansion valve may be provided in the indoor unit or the outdoor unit.

[0052] The indoor heat exchanger and the outdoor heat exchanger function as a condenser or an evaporator. When the indoor heat exchanger functions as a condenser, the air conditioner functions as a heater in a heating mode, and when the indoor heat exchanger functions as an evaporator, the air conditioner functions as a cooler in a cooling mode.

[0053] Example 1

[0054] Reference Figure 1 As shown, this embodiment relates to a variable frequency air conditioner, comprising:

[0055] The outdoor unit at least comprises a compressor 100, an outdoor fan and a first heat exchanger 200, i.e., an outdoor heat exchanger;

[0056] The indoor unit has at least a second heat exchanger 300, i.e., an indoor heat exchanger;

[0057] The expansion valve is an electronic expansion valve 400, and

[0058] A controller configured to determine whether to enter or exit a low-temperature cooling mode or an ultra-low-temperature heating mode according to temperature data and an operation mode,

[0059] It is also configured to control the compressor 100, the outdoor fan and the electronic expansion valve 400 to execute a low-temperature cooling command or an ultra-low-temperature heating command;

[0060] The temperature data includes the outdoor ambient temperature To, the indoor ambient temperature Ti, the outdoor coil temperature Toc, the indoor coil temperature Tic and the exhaust temperature Tdis.

[0061] In some embodiments of the present invention, the temperature data is acquired by collecting data from various temperature sensors. Specifically, continue to refer to Figure 1 and Figure 2As described above, a first temperature sensor 710 and a second temperature sensor 720 are provided on the first heat exchanger 200. The first temperature sensor 710 is used to collect the outdoor ambient temperature To, and the second temperature sensor 720 is used to collect the outdoor coil temperature Toc. A third temperature sensor 730 and a fourth temperature sensor 740 are provided on the second heat exchanger 300. The third temperature sensor 730 is used to collect the indoor ambient temperature Ti, and the fourth temperature sensor 740 is used to collect the indoor coil temperature Tic. A fifth temperature sensor 750 is provided on the exhaust pipe of the compressor 100, and this fifth temperature sensor 750 is used to collect the exhaust temperature Tdis.

[0062] This embodiment can simultaneously overcome the problem of poor reliability during the startup process of the refrigeration mode and the ultra-low temperature heating mode in a low-temperature environment. It can not only prevent the poor startup reliability of the air conditioner caused by the slow establishment of the low-pressure pressure in the low-temperature refrigeration mode, but also avoid the occurrence of factors that affect the reliability of the air conditioner, such as liquid hammer and oil starvation operation, in the ultra-low temperature heating mode. This enables the variable-frequency air conditioner to achieve stable startup and operation under extreme working conditions. The low temperature or ultra-low temperature involved in this embodiment refers to an outdoor environment below 10°C.

[0063] Low temperature cooling mode

[0064] In some embodiments of the present invention, for the low-temperature refrigeration mode, the refrigerant flow path refers to Figure 1 As shown, after the refrigerant exchanges heat in the second heat exchanger 300, it returns to the compressor 100 through the four-way valve 500, is compressed and condensed by the compressor 100, then enters the first heat exchanger 200 through the four-way valve 500, and finally reaches the second heat exchanger 300 through the electronic expansion valve 400 and the stop valve 600 for heat exchange again.

[0065] In some embodiments of the present invention, for the low-temperature refrigeration mode, after meeting some determination conditions, the controller can switch the variable-frequency air conditioner to the low-temperature refrigeration mode. The specific determination conditions include:

[0066] First, the current operating mode of the variable-frequency air conditioner is the refrigeration mode or the dehumidification mode;

[0067] Second, the outdoor ambient temperature To < T1, where T1 is the threshold value stored in the controller for judging the outdoor ambient temperature To;

[0068] Third, the outdoor coil temperature Toc < T2, where T2 is the threshold value stored in the controller for judging the outdoor coil temperature Toc;

[0069] When the variable frequency air conditioner satisfies the above three judgment conditions at the same time and each judgment condition is maintained for a time greater than t1, that is, the variable frequency air conditioner is in cooling mode or dehumidification mode for a time greater than t1 and the outdoor ambient temperature To has exceeded t1 for a time less than T1 and the outdoor coil temperature Toc has exceeded t1 for a time less than T2, at this time, the controller immediately switches the operating mode of the variable frequency air conditioner to the low-temperature cooling mode, that is, the variable frequency air conditioner operates in the low-temperature cooling mode.

[0070] In some embodiments of the present invention, regarding the control principle of the low-temperature refrigeration mode: when the variable frequency air conditioner operates in a low-temperature environment, the main problem is low low pressure, which affects the reliability of the compressor 100, and further affects the startup stability of the variable frequency air conditioner. Therefore, it can be adjusted from the following three aspects:

[0071] For the control of the compressor 100, by increasing the minimum operating frequency of the compressor 100, the high pressure and the refrigerant temperature can be increased, that is, preparing for increasing the low pressure from the source;

[0072] For the control of the outdoor fan, the speed of the outdoor fan can be reduced to reduce heat exchange, reduce the drop in refrigerant temperature and reduce the drop in refrigerant pressure;

[0073] For the control of the electronic expansion valve 400, the opening of the electronic expansion valve 400 can be appropriately reduced to reduce the flow rate of the refrigerant entering the second heat exchanger 300, thereby reducing heat exchange to increase the temperature and pressure of the refrigerant when it returns to the compressor 100.

[0074] In summary, when the variable frequency air conditioner enters the low temperature cooling mode, the controller sends low temperature cooling instructions to the electronic expansion valve 400, the compressor 100 and the outdoor fan respectively.

[0075] In some embodiments of the present invention, the low temperature refrigeration command includes:

[0076] (1) Narrowing the operating range of the electronic expansion valve 400, that is, the opening range: the maximum opening of the electronic expansion valve 400 is Xmax, and the minimum opening is Xmin. The specific opening is fuzzy controlled according to the exhaust gas superheat DSH, wherein the maximum opening Xmax and the minimum opening Xmin are both within the limit of the opening range of the electronic expansion valve 400 in the normal operating mode of the variable frequency air conditioner, that is, they do not exceed the opening range of the electronic expansion valve 400 in the normal operating mode.

[0077] (2) Increasing the minimum operating frequency of the compressor 100: the minimum operating frequency is Fmin.

[0078] (3) Controlling the speed of the outdoor fan according to the outdoor coil temperature Toc: Specifically, the speed of the outdoor fan is PID controlled according to the outdoor coil temperature Toc. The speed range of the outdoor fan is (FANl, FANm), where FANl is the minimum speed allowed for the outdoor fan, and FANm is the middle value between the minimum speed and the maximum speed allowed for the outdoor fan; the target value range of the outdoor coil temperature Toc is (TocG, TocH).

[0079] In some embodiments of the present invention, the specific control process of the outdoor fan is as follows:

[0080] When the outdoor coil temperature Toc is less than the target value range (TocG, TocH), the controller adjusts the outdoor fan to reduce the speed;

[0081] When the outdoor coil temperature Toc is greater than the target value range (TocG, TocH), the controller adjusts the outdoor fan to increase the speed;

[0082] Specifically, refer to Figure 3 As shown in the figure, when the outdoor coil temperature Toc is in the range of (0, TocG), as the outdoor coil temperature Toc gradually increases, the speed of the outdoor fan gradually increases from FANl; when the outdoor coil temperature Toc is in the range of (TocG, TocH), as the outdoor coil temperature Toc gradually increases, the speed of the outdoor fan remains unchanged; when the outdoor coil temperature Toc is in the range higher than TocH, as the outdoor coil temperature Toc gradually increases, the speed of the outdoor fan gradually increases to FANm.

[0083] Reference Figure 4 As shown in the figure, when the outdoor coil temperature Toc is in a range higher than TocH, as the outdoor coil temperature Toc gradually decreases, the speed of the outdoor fan gradually decreases from FANm; when the outdoor coil temperature Toc is in the range of (TocG, TocH), as the outdoor coil temperature Toc gradually decreases, the speed of the outdoor fan remains unchanged; when the outdoor coil temperature Toc is in the range of (0, TocG), as the outdoor coil temperature Toc gradually decreases, the speed of the outdoor fan gradually decreases to FANl.

[0084] When the outdoor coil temperature Toc<0°C, the controller adjusts the speed of the outdoor fan to FAN1, that is, the outdoor fan is forced to run at the lowest speed;

[0085] When the outdoor coil temperature Toc<-10°C, the controller adjusts the outdoor fan to shut down, that is, the outdoor fan is forced to stop running.

[0086] In some embodiments of the present invention, the variable frequency air conditioner also needs to meet certain determination conditions before the controller can adjust the variable frequency air conditioner to exit the low temperature cooling mode. Specific determination conditions include:

[0087] 1. The variable frequency air conditioner is switched to a shutdown state;

[0088] 2. The current state of the variable frequency air conditioner is a non-cooling mode or a non-dehumidification mode;

[0089] 3. The outdoor ambient temperature To>T3; T3 is a threshold value stored in the controller for determining the outdoor ambient temperature To;

[0090] 4. The outdoor coil temperature Toc>T4; T4 is a threshold value stored in the controller for determining the outdoor coil temperature Toc;

[0091] When the variable frequency air conditioner meets any of the above judgment conditions, the controller is configured to adjust the variable frequency air conditioner to exit the low-temperature refrigeration mode; wherein, the first two judgment conditions do not meet the time limit requirement, and the controller can only adjust the variable frequency air conditioner to exit the low-temperature refrigeration mode after the last two judgment conditions are met for the corresponding time, that is, when the outdoor ambient temperature To has exceeded t2 for a time greater than T3 or the outdoor coil temperature Toc has exceeded t2 for a time greater than T4, at this time, the controller will immediately switch the operating mode of the variable frequency air conditioner to exit the low-temperature refrigeration mode.

[0092] Ultra-low temperature heating mode

[0093] In some embodiments of the present invention, for the ultra-low temperature heating mode, the refrigerant flow path is referred to Figure 2 As shown,

[0094] After the refrigerant has been heat exchanged in the second heat exchanger 300, it enters the first heat exchanger 200 through the electronic expansion valve 400, and then returns to the compressor 100 through the four-way valve 500. After being compressed and condensed by the compressor 100, it reaches the second heat exchanger 300 again through the four-way valve 500 and the stop valve 600 for heat exchange.

[0095] In some embodiments of the present invention, the controller may switch the variable frequency air conditioner to the ultra-low temperature heating mode after the ultra-low temperature heating mode meets certain determination conditions. The specific determination conditions include:

[0096] 1. The outdoor ambient temperature To≤T5, wherein T5 is a threshold value stored in the controller for determining the outdoor ambient temperature To;

[0097] 2. When the outdoor ambient temperature To>0°C, the difference between the exhaust temperature Tdis and the outdoor ambient temperature To is not greater than ∆T1;

[0098] 3. When the outdoor ambient temperature To≤0°C, the exhaust temperature Tdis is not greater than T6, wherein T6 is a threshold value stored in the controller for determining the exhaust temperature Tdis;

[0099] When the variable frequency air conditioner is powered on for the first time, if the first and second judgment conditions are met at the same time, the controller will immediately switch the operation mode of the variable frequency air conditioner to the ultra-low temperature heating mode, or if the first and third judgment conditions are met at the same time, the controller will also immediately switch the operation mode of the variable frequency air conditioner to the ultra-low temperature heating mode. That is, when the outdoor ambient temperature To≤T5, if the outdoor ambient temperature To>0℃ and Tdis-To≤∆T1, the controller is configured to adjust the variable frequency air conditioner to enter the ultra-low temperature heating mode; if the outdoor ambient temperature To≤0℃ and Tdis≤T6, the controller is configured to adjust the variable frequency air conditioner to enter the ultra-low temperature heating mode.

[0100] In some embodiments of the present invention, when the variable frequency air conditioner is powered but the compressor 100 stops for more than 1 hour, if the first and second judgment conditions are met at the same time, the controller immediately switches the operation mode of the variable frequency air conditioner to the ultra-low temperature heating mode, or if the first and third judgment conditions are met at the same time, the controller also immediately switches the operation mode of the variable frequency air conditioner to the ultra-low temperature heating mode. That is, when the outdoor ambient temperature To≤T5, if the outdoor ambient temperature To>0℃ and Tdis-To≤∆T1, the controller is configured to adjust the variable frequency air conditioner to enter the ultra-low temperature heating mode; if the outdoor ambient temperature To≤0℃ and Tdis≤T6, the controller is configured to adjust the variable frequency air conditioner to enter the ultra-low temperature heating mode.

[0101] In some embodiments of the present invention, the ultra-low temperature heating instruction includes:

[0102] (1) Refrigerant migration;

[0103] (2) Mode transition;

[0104] (3) Heating mode;

[0105] In an ultra-low temperature environment, that is, the outdoor ambient temperature is very low and the indoor ambient temperature is relatively high, the refrigerant in the variable frequency air conditioner will gather on the outdoor unit side, and there will be basically no refrigerant on the indoor unit side. If the heating command is executed directly, very little refrigerant will return to the compressor 100 within a certain period of time, causing the suction pressure of the compressor 100 to drop to a very low level (possibly 0 or a negative value), thereby affecting the reliability of the compressor 100 (the suction pressure of the compressor 100 must be greater than 0). The principle of refrigerant migration in this embodiment is to migrate the refrigerant on the outdoor unit side to the indoor unit side, turn off the indoor fan, and do not perform heat exchange indoors, so that the refrigerant on the indoor side will gradually increase; when the refrigerant on the indoor side reaches a certain amount, the heating will be turned on, and a certain amount of refrigerant will be kept back in the compressor 100, thereby preventing the suction pressure of the compressor 100 from being too low.

[0106] Specifically, after the controller issues a refrigerant migration instruction, the completion status of the refrigerant migration instruction will be determined. When the variable frequency air conditioner meets the determination conditions, the controller continues to issue a mode transition instruction; and after the mode transition instruction is executed for time t, the controller continues to issue a heating mode instruction. At this point, the variable frequency air conditioner completes the startup of the ultra-low temperature heating mode, which greatly improves the reliability of the variable frequency air conditioner during startup, and can effectively prevent the occurrence of reliability problems such as liquid shock, oil shortage, or high and low pressure out of range in the compressor 100.

[0107] In some embodiments of the present invention, the instructions for refrigerant migration refer to Figure 5-Figure 8 As shown, including:

[0108] (1) The compressor 100 is adjusted to operate at a frequency [FREQ], where [FREQ] is the middle value of the operating frequency range of the compressor 100, referring to Figure 5 As shown, in the refrigerant migration instruction, the compressor 100 is powered on and the operating frequency increases from 0 Hz to [FREQ] Hz and is maintained at this frequency. Figure 6 As shown, the four-way valve 500 is in the disconnected state, according to the circulation path of the refrigerant in the cooling mode.

[0109] (2) Control the electronic expansion valve 400 to operate according to the opening degree [X], where [X] is the middle value of the opening range of the electronic expansion valve 400, refer to Figure 7 As shown, in the instruction of refrigerant migration, the electronic expansion valve 400 always operates according to the opening degree of [X] step.

[0110] (3) Adjust the outdoor fan to run at a speed FAN1, where FAN1 is the minimum speed of the outdoor fan, refer to Figure 8 As shown, in the refrigerant migration instruction, the outdoor fan always runs at the speed FAN1.

[0111] In some embodiments of the present invention, after the controller issues a refrigerant migration instruction, the completion status of the instruction is determined to determine whether to proceed with the next instruction.

[0112] The determination conditions for completion of the refrigerant migration include:

[0113] (1) The difference between the outdoor coil temperature Toc and the indoor coil temperature Tic is not less than ∆T2;

[0114] (2) The outdoor coil temperature Toc ≥ T7, where T7 is a threshold value stored in the controller for determining the outdoor ambient temperature To;

[0115] (3) The compressor 100 operates for a time period greater than t3;

[0116] When the variable frequency air conditioner meets any of the above judgment conditions, the controller sends a mode transition instruction to the variable frequency air conditioner, that is, when the difference between the outdoor coil temperature and the indoor coil temperature Toc-Tic≥∆T2 or when the outdoor coil temperature Toc≥T7 or when the running time of the compressor 100>t3, the controller determines that the refrigerant migration instruction in the cooling mode has been completed, and then sends a mode transition instruction to the variable frequency air conditioner.

[0117] In some embodiments of the present invention, the mode transition instruction includes:

[0118] (1) Reduce the operating frequency of the compressor 100, referring to Fig. 9 As shown, the compressor 100 operates at a frequency of 40 Hz for a period of time, and when the operating frequency is less than 40 Hz, the four-way valve 500 is powered on, that is, the four-way valve 500 is in an open state;

[0119] (2) The electronic expansion valve 400 is adjusted to operate according to the opening degree [Xfix], and the electronic expansion valve 400 is maintained at the opening degree for a time t4; Figure 7 As shown, the opening [Xfix] is greater than the opening [X], and the adjustment process of the electronic expansion valve 400 from the opening [X] to the opening [Xfix] is a linear adjustment;

[0120] (3) Adjust the outdoor fan to run at a speed of [FANh] for a time t5, where [FANh] is the maximum value of the speed range of the outdoor fan, refer to Figure 8 As shown, the process of the outdoor fan speed increasing from [FANl] to [FANh] is linear regulation.

[0121] In some embodiments of the present invention, in the mode transition instruction, when the running time maintains max{t4, t5}, the controller starts to send a heating mode instruction to the variable frequency air conditioner, that is, when the execution time of the mode transition instruction is the larger value of the running time t4 of the control instruction of the electronic expansion valve 400 and the running time t5 of the control instruction of the outdoor fan, the controller will control the next process, that is, adjust the variable frequency air conditioner to the heating mode.

[0122] In some embodiments of the present invention, the heating mode instruction includes:

[0123] (1) The compressor 100 continues to increase or decrease the frequency according to the target frequency; Figure 5 As shown, the operating frequency of the compressor 100 fluctuates around the target frequency; Figure 6 As shown, the four-way valve 500 is always in the open state.

[0124] (2) adjusting the electronic expansion valve 400 to perform fuzzy control according to the exhaust gas superheat DSH;

[0125] (3) Adjusting the speed of the outdoor fan by PID control according to the outdoor coil temperature Toc.

[0126] This embodiment can simultaneously overcome the problem of poor reliability during the startup of the cooling mode and the ultra-low temperature heating mode under low temperature environment, and can prevent the poor startup reliability of the air conditioner caused by the slow low pressure build-up in the low temperature cooling mode, and can also avoid the occurrence of factors that affect the reliability of the air conditioner, such as liquid hammer and oil-free operation in the ultra-low temperature heating mode, so that the variable frequency air conditioner can achieve stable startup and operation under extreme working conditions.

[0127] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0128] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. Inverter air conditioner, characterized in that: Comprising: An outdoor unit, which at least has a compressor, an outdoor fan, and a first heat exchanger; An indoor unit, which at least has a second heat exchanger; An expansion valve, and A controller, which is configured to judge whether to enter or exit a low-temperature refrigeration mode or an ultra-low-temperature heating mode according to temperature data and an operating mode, And is further configured to control the compressor, the outdoor fan, and the expansion valve to execute a low-temperature refrigeration instruction or an ultra-low-temperature heating instruction; The temperature data includes an outdoor ambient temperature To, an indoor ambient temperature Ti, an outdoor coil temperature Toc, an indoor coil temperature Tic, and a discharge temperature Tdis; The ultra-low-temperature heating instruction sequentially includes a refrigerant migration instruction, a mode transition instruction, and a heating mode instruction; the controller is configured to: adjust the variable-frequency air conditioner to execute the mode transition instruction according to the determination condition of the completion of the refrigerant migration, and when the maintenance time of the mode transition instruction is greater than t, adjust the variable-frequency air conditioner to enter the heating mode instruction; The refrigerant migration instruction includes: The controller is configured to adjust the expansion valve to operate at an opening degree [X], [X] being the middle value of the opening degree range of the expansion valve, adjust the outdoor fan to operate at a speed FANl, and adjust the compressor to operate at a frequency [FREQ], [FREQ] being the middle value of the operating frequency range of the compressor.

2. The variable frequency air conditioner according to claim 1, characterized in that: The entry determination condition of the low-temperature refrigeration mode includes that the variable-frequency air conditioner is in a refrigeration mode or a dehumidification mode, the outdoor ambient temperature To < T1, and the outdoor coil temperature Toc < T2. When the above determination conditions are all satisfied and the maintenance time is greater than t1, the controller is configured to adjust the variable-frequency air conditioner to enter the low-temperature refrigeration mode; where T1 and T2 are both thresholds of the temperature data built in the controller.

3. The variable frequency air conditioner according to claim 1, characterized in that: The low-temperature refrigeration instruction includes: narrowing the operating range of the expansion valve, increasing the minimum operating frequency of the compressor, and controlling the speed of the outdoor fan according to the outdoor coil temperature Toc, the speed range of the outdoor fan being (FANl, FANm); the target value range of the outdoor coil temperature Toc being (TocG, TocH).

4. The variable frequency air conditioner according to claim 3, characterized in that: The controller is configured to: When the outdoor coil temperature Toc is less than the target value, the controller adjusts the outdoor fan to reduce the speed; when the outdoor coil temperature Toc is greater than the target value, the controller adjusts the outdoor fan to increase the speed; when the outdoor coil temperature Toc < 0°C, the controller adjusts the speed of the outdoor fan to FANl; when the outdoor coil temperature Toc < -10°C, the controller adjusts the outdoor fan to shut down.

5. The variable frequency air conditioner according to claim 1, characterized in that: The exit determination condition of the low-temperature refrigeration mode includes: the variable-frequency air conditioner switches to the shutdown state, the variable-frequency air conditioner is in a non-refrigeration mode or a non-dehumidification mode, the outdoor ambient temperature To > T3, and the outdoor coil temperature Toc > T4. When any of the above determination conditions is satisfied and the maintenance time is greater than t2, the controller is configured to adjust the variable-frequency air conditioner to exit the low-temperature refrigeration mode; where T3 and T4 are both thresholds of the temperature data built in the controller.

6. The variable frequency air conditioner according to claim 1, characterized in that: The entry determination conditions of the ultra-low temperature heating mode include: When the variable frequency air conditioner is powered on for the first time or the compressor stops for more than 1 hour after power-on and the outdoor ambient temperature To≤T5, if the outdoor ambient temperature To>0℃ and Tdis-To≤∆T1, the controller is configured to adjust the variable frequency air conditioner to enter an ultra-low temperature heating mode; if the outdoor ambient temperature To≤0℃ and Tdis≤T6, the controller is configured to adjust the variable frequency air conditioner to enter an ultra-low temperature heating mode; wherein T5 and T6 are both thresholds of the temperature data built into the controller.

7. The variable frequency air conditioner according to claim 1, characterized in that: The mode transition instruction includes: The controller is configured to adjust the compressor to reduce the operating frequency. When the operating frequency is less than 40 Hz, the four-way valve is powered on, the expansion valve is adjusted to maintain the opening [Xfix] for time t4, the opening [Xfix] is greater than the opening [X], and the outdoor fan is adjusted to run at a speed [FANh] for time t5, where [FANh] is the maximum value of the speed range of the outdoor fan.

8. The variable frequency air conditioner according to claim 1, characterized in that: The heating mode instruction includes: The controller is configured to adjust the compressor to continue to increase or decrease the frequency according to the target frequency, adjust the speed of the outdoor fan to perform PID control according to the outdoor coil temperature Toc, and adjust the expansion valve to perform fuzzy control according to the exhaust superheat.

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