Air conditioner unit and its control method

Abstract

The present invention discloses an air conditioning unit and a control method thereof, wherein the air conditioning unit includes: a first plate heat exchanger, a first port connected to a second refrigerant outlet of a condenser; a frequency converter heat exchange pipeline for heat exchange with a frequency converter module of the frequency converter, a first end of the frequency converter heat exchange pipeline connected to the second port of the first plate heat exchanger, and a second end of the frequency converter heat exchange pipeline connected to the second refrigerant inlet of an evaporator; a subcooling pipeline comprising a first subcooling section, a second subcooling section, and a third subcooling section; a second throttling device disposed on the first subcooling section, for providing subcooled refrigerant to the second subcooling section, and subcooling the refrigerant in the refrigerant pipeline passing between the first port and the second port of the first plate heat exchanger to reduce the refrigerant temperature in the frequency converter heat exchange pipeline. The present invention solves the problem of the frequency converter of a chiller in the prior art being overheated when the unit pressure ratio is large, rationally utilizes the cooling capacity in the unit, and ensures efficient and reliable operation of the unit.

Description

Technical Field

[0001] The present invention relates to the technical field of air conditioning, and in particular to an air conditioning unit and a control method thereof. Background Art

[0002] In existing chillers, the inverter plays a vital role. It can change the frequency of the compressor in the unit, thereby achieving efficient operation of the unit under various working conditions. Therefore, ensuring the reliable operation of the inverter has become an important part of improving the reliability of the chiller.

[0003] For large-capacity units, especially ultra-high-temperature heat pump units operating under conditions with a large pressure ratio (the abbreviation of compression ratio, which is the ratio of condensing pressure to evaporating pressure), the power of the unit is large, and the operating temperature of the inverter module is naturally higher. When the ultra-high-temperature heat pump unit is operating under extreme high-pressure ratio conditions with large temperature rise and high outlet water temperature, if conventional cooling methods are still used for cooling, that is, liquid refrigerant is taken from the bottom of the condenser and filtered through a filter, and directly throttled and reduced in pressure through a single throttling device, its cooling capacity can no longer meet the cooling capacity required for cooling the inverter module, and the inverter module will inevitably fail and shut down due to overheating, because the lowest evaporating temperature in the unit itself is already very high and can no longer meet the cooling needs of the inverter module. When the unit is operating under low pressure difference conditions, that is, when the unit's pressure ratio is small, the inverter module will also have a high temperature. Even if the electronic expansion valve used for cooling is fully open, the inverter module temperature is still very high. After analysis, it was found that this is because the pressure before and after the throttling device of the cooling inverter is exactly the condensing pressure and evaporating pressure of the unit. When the unit's pressure ratio is low, the pressure before and after the throttling device of the cooling inverter is difficult to establish a pressure difference. The refrigerant flow rate used to cool the inverter module through the electronic expansion valve is relatively low, resulting in a high inverter module temperature.

[0004] Therefore, whether it is insufficient refrigerant cooling temperature under relatively large pressure conditions or insufficient refrigerant cooling flow under low pressure difference conditions, it will cause the inverter module to overheat.

[0005] With regard to the problem in the related art that the inverter of the chiller has an excessively high temperature when the unit pressure is relatively large, no effective solution has been proposed so far. Summary of the Invention

[0006] The present invention provides an air conditioning unit and a control method thereof, which at least solve the problem in the prior art that the inverter of a chiller has an excessively high temperature when the unit pressure is relatively large.

[0007] To solve the above technical problems, according to one aspect of an embodiment of the present invention, an air conditioning unit is provided, comprising:

[0008] A compressor, a condenser, a first throttling device, and an evaporator are connected in sequence; wherein the exhaust port of the compressor is connected to the refrigerant inlet of the condenser, the first refrigerant outlet of the condenser is connected to the first end of the first throttling device, the second end of the first throttling device is connected to the first refrigerant inlet of the evaporator, and the refrigerant outlet of the evaporator is connected to the air intake of the compressor;

[0009] A first plate heat exchanger includes a first port, a second port, a third port, and a fourth port, wherein the first port of the first plate heat exchanger is connected to the second port of the first plate heat exchanger, the third port of the first plate heat exchanger is connected to the fourth port of the first plate heat exchanger, and the first port of the first plate heat exchanger is connected to the second refrigerant outlet of the condenser;

[0010] A frequency converter heat exchange pipeline is provided in the frequency converter and exchanges heat with the frequency converter module of the frequency converter. A first end of the frequency converter heat exchange pipeline is connected to the second port of the first plate heat exchanger, and a second end of the frequency converter heat exchange pipeline is connected to the second refrigerant inlet of the evaporator.

[0011] The subcooling pipeline includes a first subcooling section, a second subcooling section, and a third subcooling section; wherein one end of the first subcooling section is connected to the second refrigerant outlet of the condenser, and the other end is connected to the third port of the first plate heat exchanger; the second subcooling section is a refrigerant pipeline between the third port and the fourth port of the first plate heat exchanger; one end of the third subcooling section is connected to the fourth port of the first plate heat exchanger, and the other end is connected to the third refrigerant inlet of the evaporator;

[0012] The second throttling device is arranged on the first supercooling section and is used to provide supercooled refrigerant for the second supercooling section, supercooling the refrigerant in the refrigerant pipeline between the first port and the second port of the first plate heat exchanger to reduce the refrigerant temperature in the inverter heat exchange pipeline.

[0013] Further, it also includes: a second plate heat exchanger, including a first port, a second port, a third port and a fourth port, the first port of the second plate heat exchanger is connected to the second port of the second plate heat exchanger, the third port of the second plate heat exchanger is connected to the fourth port of the second plate heat exchanger, the first port of the second plate heat exchanger is connected to the second port of the first plate heat exchanger, and the second port of the second plate heat exchanger is connected to the first end of the inverter heat exchange pipeline;

[0014] The chilled water heat exchange pipeline includes a first chilled water heat exchange section and a second chilled water heat exchange section; wherein, one end of the first chilled water heat exchange section is connected to the chilled water inlet of the evaporator, and the other end is connected to the fourth port of the second plate heat exchanger; one end of the second chilled water heat exchange section is connected to the third port of the second plate heat exchanger, and the other end is connected to the chilled water outlet of the evaporator.

[0015] Furthermore, it also includes: a solenoid valve located on the first chilled water heat exchange section; and a manual regulating valve located on the first chilled water heat exchange section.

[0016] Furthermore, it also includes: a third throttling device, which is arranged on the pipeline between the second port of the first plate heat exchanger and the first port of the second plate heat exchanger.

[0017] Furthermore, it also includes: a flasher, which is arranged on the pipeline between the first throttling device and the evaporator; wherein the liquid inlet of the flasher is connected to the first throttling device, the liquid outlet of the flasher is connected to the first refrigerant inlet of the evaporator, and the exhaust port of the flasher is connected to the air supply port of the compressor; a fourth throttling device is located on the pipeline between the liquid outlet of the flasher and the first refrigerant inlet of the evaporator.

[0018] Furthermore, the frequency converter further includes: a fan, which is arranged in the frequency converter.

[0019] Furthermore, it also includes:

[0020] The condensing pressure sensor is installed on the condenser and is used to detect the condensing pressure;

[0021] The cooling water outlet temperature sensor is installed on the cooling water outlet pipe of the condenser to detect the cooling water outlet temperature;

[0022] The evaporation pressure sensor is installed on the evaporator to detect the evaporation pressure;

[0023] The suction temperature sensor is installed at the suction port of the compressor to detect the suction temperature of the compressor;

[0024] A plate heat exchanger inlet liquid temperature sensor is provided at the first port of the first plate heat exchanger and is used to detect the plate heat exchanger inlet liquid temperature;

[0025] A plate heat exchanger outlet liquid temperature sensor is provided at the second port of the first plate heat exchanger and is used to detect the plate heat exchanger outlet liquid temperature;

[0026] The module temperature sensor is arranged on the inverter module of the inverter and is used to detect the temperature of the inverter module.

[0027] According to another aspect of an embodiment of the present invention, a method for controlling an air conditioning unit is provided, which is applied to the air conditioning unit as described above, and the method includes:

[0028] Detect the pressure ratio of the air conditioning unit; the pressure ratio is the ratio of the condensing pressure to the evaporating pressure;

[0029] Determine the cooling mode of the inverter based on the pressure ratio;

[0030] Controls the operation of the air conditioning unit according to the cooling mode.

[0031] Furthermore, the cooling mode of the inverter is determined according to the pressure ratio, including: when the pressure ratio is greater than the first preset pressure ratio and less than the second preset pressure ratio, determining that the cooling mode of the inverter is the inverter heat exchange pipeline cooling mode; wherein, the second preset pressure ratio is greater than the first preset pressure ratio; when the pressure ratio is greater than or equal to the second preset pressure ratio, determining that the cooling mode of the inverter is the supercooling pipeline cooling mode; when the pressure ratio is less than or equal to the first preset pressure ratio, determining that the cooling mode of the inverter is the chilled water heat exchange pipeline cooling mode.

[0032] Furthermore, when the cooling mode of the inverter is the inverter heat exchange pipeline cooling mode, the operation of the air-conditioning unit is controlled according to the cooling mode, including: controlling the first throttling device to open, the second throttling device and the solenoid valve to close, and controlling the third throttling device to open to the first preset opening after the inverter fan is turned on for a first preset time; after the third throttling device maintains the first preset opening for a second preset time, adjusting the opening of the third throttling device according to the temperature of the inverter module of the inverter.

[0033] Furthermore, when the cooling mode of the inverter is the subcooling pipe cooling mode, the operation of the air-conditioning unit is controlled according to the cooling mode, including: controlling the first throttling device to open, the second throttling device to open, the third throttling device to open, and the solenoid valve to close; after the second throttling device is opened, controlling the second throttling device to open to a second preset opening; after the second throttling device maintains the second preset opening for a third preset time, adjusting the opening of the second throttling device according to the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp and the condenser end temperature difference ΔTc; wherein, the plate exchange subcooling degree ΔT1 = plate exchange outlet liquid temperature - plate exchange inlet liquid temperature, the compressor suction superheat degree ΔTp = compressor suction temperature - evaporation temperature, and the condenser end temperature difference ΔTc = condensation temperature - cooling water outlet water temperature.

[0034] Furthermore, the opening of the second throttling device is adjusted according to the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp and the condenser end temperature difference ΔTc, including: calculating the opening D1 of the throttling device corresponding to the plate exchange subcooling degree ΔT1, the opening D2 of the throttling device corresponding to the compressor suction superheat degree ΔTp and the opening D3 of the throttling device corresponding to the condenser end temperature difference ΔTc, the opening D of the second throttling device = D1 + D2 + D3; when D> the first preset value, controlling the second throttling device to increase the third preset opening; when D< the second preset value, controlling the second throttling device to reduce the fourth preset opening; when the second preset value < D < the first preset value, keeping the opening of the second throttling device unchanged; wherein, the first preset value > the second preset value.

[0035] Furthermore, when ΔT1 ≥ 5°C, D1 = 0;

[0036] When ΔT1<5°C, D1=1*(5-ΔT1);

[0037] When ΔTp≤2℃, D3=0.5*(ΔTd-2);

[0038] When ΔTp>2°C, D3=0.3*(2-ΔTd);

[0039] When ΔTc≤1.5℃, D2=0;

[0040] When ΔTc>1.5°C, D2=0.7*(ΔTc-1.5).

[0041] Furthermore, when the cooling mode of the inverter is the chilled water heat exchange pipeline cooling mode, the operation of the air-conditioning unit is controlled according to the cooling mode, including: controlling the first throttling device to open, the second throttling device to open, the third throttling device to open, and the solenoid valve to open; and using a manual regulating valve to control the refrigerant flow of the chilled water heat exchange pipeline.

[0042] According to another aspect of the embodiments of the present invention, a storage medium containing computer-executable instructions is provided. When the computer-executable instructions are executed by a computer processor, the computer-executable instructions are used to perform the above-mentioned air-conditioning unit control method.

[0043] In the present invention, a cooling scheme for the inverter in an ultra-high temperature heat pump chiller is proposed. By setting a subcooling pipeline and a second throttling device, the refrigerant temperature in the heat exchange pipeline of the inverter is lowered by the subcooled refrigerant in the subcooling pipeline, thereby solving the problem that when the chiller operates at a large pressure ratio, the cooling capacity provided by the refrigerant is insufficient due to the large power of the unit and the large heat generation of the inverter, which ultimately causes the inverter to over-temperature and shut down. The scheme can also reasonably utilize the cooling capacity in the unit to ensure the efficient and reliable operation of the unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic diagram of an optional structure of an air-conditioning unit according to an embodiment of the present invention;

[0045] Figure 2 This is an optional flow chart of the air conditioning unit control method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0046] Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent like or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present invention, as detailed in the appended claims.

[0047] Example 1

[0048] In a preferred embodiment 1 of the present invention, an air conditioning unit is provided. Specifically, Figure 1 An optional structural diagram of the unit is shown as follows: Figure 1 As shown, the unit includes:

[0049] The compressor 1, condenser 2, first throttling device 12 and evaporator 9 are connected in sequence; wherein the exhaust port of the compressor 1 is connected to the refrigerant inlet of the condenser 2, the first refrigerant outlet of the condenser 2 is connected to the first end of the first throttling device 12, the second end of the first throttling device 12 is connected to the first refrigerant inlet of the evaporator 9, and the refrigerant outlet of the evaporator 9 is connected to the air intake of the compressor 1;

[0050] The first plate heat exchanger 4 includes a first port, a second port, a third port, and a fourth port. The first port of the first plate heat exchanger 4 is connected to the second port of the first plate heat exchanger 4, the third port of the first plate heat exchanger 4 is connected to the fourth port of the first plate heat exchanger 4, and the first port of the first plate heat exchanger 4 is connected to the second refrigerant outlet of the condenser 2;

[0051] The inverter heat exchange pipeline 8 is provided in the inverter 7 and exchanges heat with the inverter module of the inverter 7. The first end of the inverter heat exchange pipeline 8 is connected to the second port of the first plate heat exchanger 4, and the second end of the inverter heat exchange pipeline 8 is connected to the second refrigerant inlet of the evaporator 9;

[0052] The subcooling pipeline includes a first subcooling section, a second subcooling section, and a third subcooling section; wherein one end of the first subcooling section is connected to the second refrigerant outlet of the condenser 2, and the other end is connected to the third port of the first plate heat exchanger 4; the second subcooling section is the refrigerant pipeline between the third port and the fourth port of the first plate heat exchanger 4; one end of the third subcooling section is connected to the fourth port of the first plate heat exchanger 4, and the other end is connected to the third refrigerant inlet of the evaporator 9;

[0053] The second throttling device 3 is arranged on the first subcooling section, and is used to provide subcooled refrigerant for the second subcooling section, and subcool the refrigerant in the refrigerant pipeline between the first port and the second port of the first plate heat exchanger 4 to reduce the refrigerant temperature in the inverter heat exchange pipeline 8.

[0054] In the above embodiment, a cooling scheme for the inverter in an ultra-high temperature heat pump chiller is proposed. By setting a subcooling pipeline and a second throttling device, the refrigerant temperature in the heat exchange pipeline of the inverter is reduced by the subcooled refrigerant in the subcooling pipeline, thereby solving the problem that when the chiller is operating under a large pressure ratio, the cooling capacity provided by the refrigerant is insufficient due to the large power of the unit and the large heat generation of the inverter, which ultimately causes the inverter to overheat and shut down. The scheme can also reasonably utilize the cooling capacity in the unit to ensure the efficient and reliable operation of the unit.

[0055] The above-mentioned supercooling pipeline and the second throttling device 3 constitute a first cooling scheme, specifically: open the second throttling device 3, and the low-temperature and low-pressure refrigerant after throttling and reducing the pressure by the second throttling device 3 can pass through the refrigerant pipeline between the first port and the second port of the first plate heat exchanger 4 to supercool the high-temperature liquid refrigerant in the refrigerant pipeline between the third port and the fourth port of the second plate heat exchanger 6, which can greatly reduce the refrigerant temperature. After that, the supercooled refrigerant is throttled and reduced in pressure by the third throttling device 5. As the pressure decreases, the temperature is further reduced, and then heat exchange with the inverter module is completed for cooling; at the same time, the refrigerant in this path passes through the second throttling device 3 into the plate heat exchanger and absorbs heat, so it can also increase the suction superheat when entering the evaporator 9, thereby preventing the unit from sucking liquid.

[0056] In order to solve the problem of insufficient refrigerant cooling flow under low pressure difference conditions in the prior art, which leads to overheating of the inverter module, the present solution also includes a second cooling solution, including: a second plate heat exchanger 6, including a first port, a second port, a third port and a fourth port, the first port of the second plate heat exchanger 6 is connected to the second port of the second plate heat exchanger 6, the third port of the second plate heat exchanger 6 is connected to the fourth port of the second plate heat exchanger 6, the first port of the second plate heat exchanger 6 is connected to the second port of the first plate heat exchanger 4, and the second port of the second plate heat exchanger 6 is connected to the first end of the inverter heat exchange pipeline 8; and a chilled water heat exchange pipeline, including a first chilled water heat exchange section and a second chilled water heat exchange section; wherein, one end of the first chilled water heat exchange section is connected to the chilled water inlet of the evaporator 9, and the other end is connected to the fourth port of the second plate heat exchanger 6; one end of the second chilled water heat exchange section is connected to the third port of the second plate heat exchanger 6, and the other end is connected to the chilled water outlet of the evaporator 9. As shown in the figure, it also includes: a solenoid valve 10, located on the first chilled water heat exchange section; and a manual regulating valve 11, located on the first chilled water heat exchange section.

[0057] On the basis of opening the valve in the first cooling scheme circuit, the solenoid valve 10 is opened, and the circulation of the cooling circuit can be completed by utilizing the pressure difference between the inlet and outlet of the chilled water. The cooling capacity of the chilled water is used again through the second plate heat exchanger 6 to supercool the refrigerant entering the inverter heat exchange pipeline 8. The amount of cooling capacity required for supercooling is adjusted by the manual regulating valve.

[0058] In addition, it also includes: a third throttling device 5, which is arranged on the pipeline between the second port of the first plate heat exchanger 4 and the first port of the second plate heat exchanger 6. The high-temperature and high-pressure gaseous refrigerant coming out of the compressor 1 enters the condenser 2 for condensation and cooling, and then directly enters the first plate heat exchanger 4. At this time, the second throttling device 3 on the other side of the first plate heat exchanger 4 is closed, that is, the refrigerant does not exchange heat through the first plate heat exchanger 4. After that, it enters the second plate heat exchanger 6 after throttling and reducing the pressure through the third throttling device 5. At the same time, the solenoid valve 10 and the manual regulating valve on the other side of the second plate heat exchanger 6 are closed. After passing through the second plate heat exchanger 6, there is also no heat exchange. After that, the refrigerant directly exchanges heat with the inverter heat exchange coil and the inverter module before entering the evaporator 9. This is the third cooling circuit. The plate heat exchangers passed by this path have no cooling and heat exchange effect. This is the third cooling scheme.

[0059] The unit also includes a flash condenser 13, located in the pipeline between the first throttling device 12 and the evaporator 9. The liquid inlet of the flash condenser 13 is connected to the first throttling device 12, the liquid outlet of the flash condenser 13 is connected to the first refrigerant inlet of the evaporator 9, and the exhaust port of the flash condenser 13 is connected to the air supply port of the compressor 1. A fourth throttling device 14 is located in the pipeline between the liquid outlet of the flash condenser 13 and the first refrigerant inlet of the evaporator 9. The compressor 1, condenser 2, flash condenser 13, fourth throttling device 14, and evaporator 9 form a conventional cooling and heating circuit and operate continuously after the air conditioning unit is turned on.

[0060] Meanwhile, the frequency converter 7 further includes a fan 22, which is provided inside the frequency converter 7. The fan 22 inside the frequency converter 7 is always on to perform convection heat exchange on the frequency converter module.

[0061] The system is equipped with temperature and pressure sensors, which work in conjunction with control logic to switch and control the cooling circuit, including:

[0062] The condensing pressure sensor 15 is provided on the condenser 2 and is used to detect the condensing pressure; the corresponding condensing temperature can be calculated by the controller;

[0063] The cooling water outlet temperature sensor 16 is provided on the cooling water outlet pipe of the condenser 2 and is used to detect the cooling water outlet temperature;

[0064] The evaporation pressure sensor 17 is provided on the evaporator 9 and is used to detect the evaporation pressure; the corresponding evaporation temperature can be calculated by the controller;

[0065] The suction temperature sensor 18 is provided at the suction port of the compressor 1 and is used to detect the suction temperature of the compressor 1;

[0066] The plate heat exchanger inlet liquid temperature sensor 19 is provided at the first port of the first plate heat exchanger 4 and is used to detect the plate heat exchanger inlet liquid temperature. Since the condenser 2 is a horizontal shell and tube condenser 2, there is a subcooling area at its lower part. Therefore, a plate heat exchanger inlet liquid temperature sensor 19 is also installed thereon to measure the outlet liquid temperature of the condenser 2, that is, the temperature of the liquid refrigerant before entering the first plate heat exchanger 4.

[0067] The plate exchanged liquid temperature sensor 20 is provided at the second port of the first plate heat exchanger 4 and is used to detect the plate exchanged liquid temperature;

[0068] The module temperature sensor 21 is provided on the inverter module of the inverter 7 and is used to detect the temperature of the inverter module of the inverter 7 .

[0069] This solution provides a cooling scheme for the inverter in an ultra-high-temperature heat pump chiller. Three cooling schemes are available. In all three cooling schemes, the fan in the inverter is always on, enabling convective heat transfer for the inverter module. Using only the unit's refrigerant or chilled water for cooling presents an overheating risk. In the first cooling scheme, while the fan is always on, the electronic expansion valve (i.e., the second throttling device 3) in the subcooling line is opened under conditions with a high pressure ratio. This subcools the liquid refrigerant flowing out of the condenser and then throttles it through the third throttling device 5 to complete the cooling of the inverter module. The second cooling scheme is suitable for low-pressure differential conditions with a very low pressure ratio. Due to the small pressure differential between the refrigerant and the refrigerant, the refrigerant flow rate is small. The refrigerant can be further cooled through the second plate heat exchanger by utilizing the inlet and outlet pressure differential of the chilled water. The chilled water only exchanges heat with the refrigerant, not mass. Even with a low flow rate, sufficient cooling capacity is provided to complete the cooling of the inverter module. The third cooling solution is to use electronic expansion valve cooling under working conditions with moderate pressure ratio. The inverter module can be cooled by closing the throttling electronic expansion valve or solenoid valve in the subcooling pipeline and the chilled water heat exchange pipeline.

[0070] The control methods corresponding to the three cooling schemes are to measure the evaporation pressure and condensing pressure in the unit through pressure sensors, and to measure the temperature before and after the plate heat exchanger, the temperature of the inverter module and other parameters through temperature sensors, and respectively control the on and off of the solenoid valves or the opening of the electronic expansion valves in the three cooling circuits with the corresponding control logic, so as to realize the cooling method of the inverter module under different working conditions.

[0071] Example 2

[0072] In a preferred embodiment 2 of the present invention, a method for controlling an air-conditioning unit is provided, which is applied to the air-conditioning unit in the above embodiment 1. Specifically, Figure 2 An optional flow chart of the method is shown as follows: Figure 2 As shown, the method includes the following steps S202-S206:

[0073] S202: Detecting the pressure ratio of the air conditioning unit; wherein the pressure ratio is the ratio of the condensing pressure to the evaporating pressure;

[0074] S204: Determine a cooling mode for the inverter according to the pressure ratio;

[0075] S206: Control the operation of the air conditioning unit according to the cooling mode.

[0076] In the above embodiment, a cooling scheme for the inverter in an ultra-high temperature heat pump chiller is proposed. By setting a subcooling pipeline and a second throttling device, the refrigerant temperature in the heat exchange pipeline of the inverter is reduced by the subcooled refrigerant in the subcooling pipeline, thereby solving the problem that when the chiller is operating under a large pressure ratio, the cooling capacity provided by the refrigerant is insufficient due to the large power of the unit and the large heat generation of the inverter, which ultimately causes the inverter to overheat and shut down. The scheme can also reasonably utilize the cooling capacity in the unit to ensure the efficient and reliable operation of the unit.

[0077] The inverter cooling mode is determined based on the pressure ratio, including: when the pressure ratio is greater than a first preset pressure ratio and less than a second preset pressure ratio, the inverter cooling mode is determined to be the inverter heat exchange pipeline cooling mode; wherein the second preset pressure ratio is greater than the first preset pressure ratio; when the pressure ratio is greater than or equal to the second preset pressure ratio, the inverter cooling mode is determined to be the subcooling pipeline cooling mode; when the pressure ratio is less than or equal to the first preset pressure ratio, the inverter cooling mode is determined to be the chilled water heat exchange pipeline cooling mode. Regardless of the pressure ratio, the fan in the inverter of the system is always on.

[0078] When the cooling mode of the inverter is the inverter heat exchange pipeline cooling mode, the operation of the air-conditioning unit is controlled according to the cooling mode, including: controlling the first throttling device to open, the second throttling device and the solenoid valve to close, and after the fan of the inverter is turned on for a first preset time, controlling the third throttling device to open to a first preset opening; after the third throttling device maintains the first preset opening for a second preset time, adjusting the opening of the third throttling device according to the temperature of the inverter module of the inverter. For example, when the pressure ratio ε is less than 1.8 and less than 2.5, meaning the pressure ratio is moderate, the solenoid valve closes and the second throttling device is closed to 0%. The system uses the first cooling circuit to cool the inverter module, while the third throttling device adjusts its opening to control the inverter module temperature. When the unit is shut down, the target opening of the third throttling device is 0%. When the unit receives the power-on command, the inverter fan starts after 1 minute, and the target opening of the third throttling device increases from 0% to 50%. After 2 minutes, the opening automatically adjusts to the minimum target opening of 0%. Because the third throttling device must be open regardless of the cooling circuit, providing the primary cooling capacity, its maximum target opening is 100%. Based on the module temperature detected by the module temperature sensor, the third throttling device's opening is automatically increased or decreased to prevent overheating and condensation in the module.

[0079] When the cooling mode of the inverter is the subcooling pipe cooling mode, the operation of the air-conditioning unit is controlled according to the cooling mode, including: controlling the first throttling device to open, the second throttling device to open, the third throttling device to open, and the solenoid valve to close; after the second throttling device is opened, controlling the second throttling device to open to a second preset opening; after the second throttling device maintains the second preset opening for a third preset time, adjusting the opening of the second throttling device according to the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp and the condenser end temperature difference ΔTc; wherein, the plate exchange subcooling degree ΔT1 = plate exchange outlet liquid temperature - plate exchange inlet liquid temperature, the compressor suction superheat degree ΔTp = compressor suction temperature - evaporation temperature, and the condenser end temperature difference ΔTc = condensing temperature - cooling water outlet water temperature.

[0080] For example, when the system pressure ratio ε≥2.5, the fan in the inverter of the system continues to remain normally open, the solenoid valve remains closed, and the second throttling device is opened. That is, at this time, the system pressure ratio is relatively large and the module heats up more. The system adopts the second cooling circuit, and uses the first plate heat exchanger to supercool the refrigerant in the first cooling circuit. Then, the temperature is further reduced by throttling and cooling through the third throttling device. At the same time, under the large pressure ratio working condition, the pressure difference before and after the cooling circuit in the system is sufficient, and the flow rate of the refrigerant is sufficient. At this time, the second cooling circuit can complete the cooling of the module; when the second throttling device is opened, its opening D increases from 0% to 30%, and after 2 minutes, its opening is automatically adjusted, and the target maximum opening is 50%. After 2 minutes, the second throttling device enters the automatic adjustment mode. The parameters used in the automatic adjustment mode include plate heat exchanger subcooling ΔT1, compressor suction superheat ΔTp and condenser end temperature difference ΔTc to adjust the opening of the second throttling device. Furthermore, the opening of the second throttling device is adjusted according to the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp and the condenser end temperature difference ΔTc, including: calculating the sum D of the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp and the condenser end temperature difference ΔTc; when D>first preset value, controlling the second throttling device to increase the third preset opening; when D<second preset value, controlling the second throttling device to reduce the fourth preset opening; when the second preset value<D<first preset value, keeping the opening of the second throttling device unchanged; wherein, the first preset value>second preset value.

[0081] The second throttling device is controlled by the subcooling degree ΔT1 of the first plate heat exchanger, the suction superheat degree ΔTp of the compressor and the temperature difference ΔTc at the condenser end. The second throttling device performs an action every 5 seconds, and the amplitude of each action does not exceed 5%. The calculation formula of the action amplitude is:

[0082] D=D1+D2+D3; D1, D2, and D3 are the opening degrees of the throttling device corresponding to the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp, and the condenser end temperature difference ΔTc, respectively. Preferably, D1 is the value of the plate exchange subcooling degree ΔT1, D2 is the value of the compressor suction superheat degree ΔTp, and D3 is the value of the condenser end temperature difference ΔTc. The opening degree of the second throttling device is adjusted according to D.

[0083] When D>0.5, the target opening of the second throttling device increases by D%, when 0.5≥D≥-0.5, the target opening of the second throttling device remains unchanged, and when D<-0.5, the target opening of the second throttling device decreases by D%.

[0084] Among them, when the subcooling degree ΔT1 of the first plate heat exchanger is ≥5°C, D1=0;

[0085] When the subcooling degree of the first plate heat exchanger ΔT1 is less than 5°C, D1 = 1*(5-ΔT1);

[0086] When the temperature difference at the condenser end ΔTc≤1.5℃, D2=0;

[0087] When the temperature difference at the condenser end ΔTc>1.5℃, D2=0.7*(ΔTc-1.5);

[0088] When the compressor suction superheat ΔTp ≤ 2°C, D3 = 0.5*(ΔTd-2);

[0089] When the compressor suction superheat ΔTp>2°C, D3=0.3*(2-ΔTd).

[0090] When the cooling mode of the inverter is the chilled water heat exchange pipeline cooling mode, the operation of the air-conditioning unit is controlled according to the cooling mode, including: controlling the first throttling device to open, the second throttling device to open, the third throttling device to open, and the solenoid valve to open; and using a manual regulating valve to control the refrigerant flow in the chilled water heat exchange pipeline.

[0091] For example, when the system pressure ratio ε≤1.8, the overall pressure ratio in the system is small, resulting in a small pressure difference before and after the module is cooled, which makes the refrigerant flow in the cooling circuit small. Therefore, the pressure difference between the inlet and outlet of the chilled water is used to cool the refrigerant again through the second plate heat exchanger. The chilled water only exchanges heat with the refrigerant but not mass. Even if the flow rate is low, sufficient cooling capacity can be provided to complete the cooling of the module. At the same time, the fan in the inverter of the system continues to remain normally open, that is, the third cooling circuit is used at this time, that is, the third throttling device is turned on, and the control method is the same as that described in the first cooling circuit; the second throttling device is turned on, and the control method is the same as that described in the second cooling circuit; the solenoid valve is turned on, and the manual regulating valve can be used to manually adjust the cooling capacity required by the module under the low pressure difference working condition of the system.

[0092] When the unit receives the shutdown command, the fan in the inverter is shut down after 1 minute, the solenoid valve 3 is closed, and the target opening of the second throttling device and the third throttling device is changed from the current opening to 0%.

[0093] Example 3

[0094] Based on the air conditioning unit control method provided in the above embodiment 2, a storage medium containing computer executable instructions is further provided in a preferred embodiment 3 of the present invention. When the computer executable instructions are executed by a computer processor, they are used to execute the air conditioning unit control method as described above.

[0095] In the above embodiment, a cooling scheme for the inverter in an ultra-high temperature heat pump chiller is proposed. By setting a subcooling pipeline and a second throttling device, the refrigerant temperature in the heat exchange pipeline of the inverter is reduced by the subcooled refrigerant in the subcooling pipeline, thereby solving the problem that when the chiller is operating under a large pressure ratio, the cooling capacity provided by the refrigerant is insufficient due to the large power of the unit and the large heat generation of the inverter, which ultimately causes the inverter to overheat and shut down. The scheme can also reasonably utilize the cooling capacity in the unit to ensure the efficient and reliable operation of the unit.

[0096] Other embodiments of the present invention will readily occur to those skilled in the art after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not invented herein. The description and examples are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the following claims.

[0097] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for controlling an air conditioning unit, characterized in that: The air-conditioning unit includes: a first plate heat exchanger, including a first port, a second port, a third port and a fourth port, the first port of the first plate heat exchanger is connected to the second port of the first plate heat exchanger, the third port of the first plate heat exchanger is connected to the fourth port of the first plate heat exchanger, and the first port of the first plate heat exchanger is connected to the second refrigerant outlet of the condenser; an inverter heat exchange pipeline is arranged in the inverter and exchanges heat with the inverter module of the inverter, the first end of the inverter heat exchange pipeline is connected to the second port of the first plate heat exchanger, and the second end of the inverter heat exchange pipeline is connected to the second refrigerant inlet of the evaporator; a subcooling pipeline includes a first subcooling section, a second subcooling section and a third subcooling section; wherein, one end of the first subcooling section is connected to the second refrigerant outlet of the condenser, and the other end is connected to the third port of the first plate heat exchanger; the second subcooling section is between the third port and the fourth port of the first plate heat exchanger 14. The refrigerant pipeline of claim 13, wherein the first refrigerant pipe is connected to the first plate heat exchanger and the second refrigerant pipe is connected to the first plate heat exchanger. The refrigerant pipe is connected to the first refrigerant pipe of the evaporator. The refrigerant pipe is connected to the first refrigerant pipe of the evaporator. The refrigerant pipe is connected to the first refrigerant pipe of the evaporator. The refrigerant pipe is connected to the first refrigerant pipe of the evaporator. The refrigerant pipe is connected to the first refrigerant pipe of the evaporator. The method comprises: Detecting the pressure ratio of the air conditioning unit; wherein the pressure ratio is the ratio of the condensing pressure to the evaporating pressure; Determine a cooling mode of the inverter according to the pressure ratio; wherein the cooling modes include at least: an inverter heat exchange pipe cooling mode in which the inverter is cooled by the inverter heat exchange pipe, a subcooling pipe cooling mode in which the inverter is cooled by the subcooling pipe, and a chilled water heat exchange pipe cooling mode in which the inverter is cooled by the chilled water heat exchange pipe; controlling the operation of the air conditioning unit according to the cooling mode; Determining a cooling mode of the inverter according to the pressure ratio includes: When the pressure ratio is greater than a first preset pressure ratio and less than a second preset pressure ratio, determining that the cooling mode of the inverter is an inverter heat exchange pipeline cooling mode; wherein the second preset pressure ratio is greater than the first preset pressure ratio; When the pressure ratio is greater than or equal to the second preset pressure ratio, determining that the cooling mode of the inverter is a supercooling pipeline cooling mode; When the pressure ratio is less than or equal to the first preset pressure ratio, the cooling mode of the inverter is determined to be a chilled water heat exchange pipeline cooling mode.

2. The method according to claim 1, characterized in that The air-conditioning unit further includes: a compressor, the condenser, a first throttling device and an evaporator connected in sequence; wherein the exhaust port of the compressor is connected to the refrigerant inlet of the condenser, the first refrigerant outlet of the condenser is connected to the first end of the first throttling device, the second end of the first throttling device is connected to the first refrigerant inlet of the evaporator, and the refrigerant outlet of the evaporator is connected to the suction port of the compressor; a second throttling device is provided on the first supercooling section, for providing supercooled refrigerant to the second supercooling section, supercooling the refrigerant in the refrigerant pipeline between the first port and the second port of the first plate heat exchanger, so as to reduce the refrigerant temperature in the inverter heat exchange pipeline; a solenoid valve is located on the first chilled water heat exchange section; a third throttling device is provided on the pipeline between the second port of the first plate heat exchanger and the first port of the second plate heat exchanger; When the cooling mode of the inverter is the inverter heat exchange pipe cooling mode, controlling the operation of the air conditioning unit according to the cooling mode includes: Controlling the first throttling device to open, the second throttling device and the solenoid valve to close, and controlling the third throttling device to open to a first preset opening degree after the fan of the inverter is turned on for a first preset time; After the third throttling device maintains the first preset opening for a second preset time, the opening of the third throttling device is adjusted according to the temperature of the inverter module of the inverter.

3. The method according to claim 2, characterized in that When the cooling mode of the inverter is the supercooling pipe cooling mode, controlling the operation of the air-conditioning unit according to the cooling mode includes: Controlling the first throttling device to open, the second throttling device to open, the third throttling device to open, and the solenoid valve to close; After the second throttling device is opened, controlling the second throttling device to open to a second preset opening; After the second throttling device maintains the second preset opening for a third preset time, the opening of the second throttling device is adjusted according to the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp and the condenser end temperature difference ΔTc; wherein, the plate exchange subcooling degree ΔT1 = plate exchange outlet liquid temperature - plate exchange inlet liquid temperature, the compressor suction superheat degree ΔTp = compressor suction temperature - evaporation temperature, and the condenser end temperature difference ΔTc = condensing temperature - cooling water outlet temperature.

4. The method according to claim 3, characterized in that Adjusting the opening of the second throttling device according to the plate exchange subcooling degree ΔT1, the compressor suction superheat degree ΔTp and the condenser end temperature difference ΔTc includes: Calculate the throttling device opening D1 corresponding to the plate exchange subcooling degree ΔT1, the throttling device opening D2 corresponding to the compressor suction superheat ΔTp, and the throttling device opening D3 corresponding to the condenser end temperature difference ΔTc, where the second throttling device opening D = D1 + D2 + D3; When D>the first preset value, controlling the second throttling device to increase the third preset opening; When D is less than a second preset value, controlling the second throttling device to reduce a fourth preset opening; When the second preset value < D < the first preset value, the opening of the second throttling device is kept unchanged; wherein, the first preset value > the second preset value.

5. The method according to claim 4, characterized in that When ΔT1≥5℃, D1=0; When ΔT1<5°C, D1=1*(5-ΔT1); When ΔTp≤2℃, D3=0.5*(ΔTd-2); When ΔTp>2°C, D3=0.3*(2-ΔTd); When ΔTc≤1.5℃, D2=0; When ΔTc>1.5°C, D2=0.7*(ΔTc-1.5).

6. The method according to claim 2, characterized in that When the cooling mode of the inverter is a chilled water heat exchange pipe cooling mode, controlling the operation of the air conditioning unit according to the cooling mode includes: Controlling the first throttling device to open, the second throttling device to open, the third throttling device to open, and the solenoid valve to open; A manual regulating valve is used to control the refrigerant flow in the chilled water heat exchange pipeline; wherein the manual regulating valve is located on the first chilled water heat exchange section.

7. A storage medium containing computer-executable instructions, characterized in that: When the computer executable instructions are executed by a computer processor, they are used to perform the air conditioning unit control method according to any one of claims 1 to 6.

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