CN112944725A - Variable frequency heat pump unit and control method thereof - Google Patents
Variable frequency heat pump unit and control method thereof Download PDFInfo
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- CN112944725A CN112944725A CN202110215548.8A CN202110215548A CN112944725A CN 112944725 A CN112944725 A CN 112944725A CN 202110215548 A CN202110215548 A CN 202110215548A CN 112944725 A CN112944725 A CN 112944725A
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- 238000000034 method Methods 0.000 title claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 12
- 230000007246 mechanism Effects 0.000 claims abstract description 7
- 239000003507 refrigerant Substances 0.000 claims description 13
- 238000005299 abrasion Methods 0.000 claims description 2
- 230000009467 reduction Effects 0.000 claims description 2
- 238000010438 heat treatment Methods 0.000 abstract description 10
- 230000000694 effects Effects 0.000 abstract description 5
- 230000004044 response Effects 0.000 abstract description 3
- 239000003921 oil Substances 0.000 description 104
- 238000010586 diagram Methods 0.000 description 6
- 239000010687 lubricating oil Substances 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 4
- 230000035559 beat frequency Effects 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 238000010977 unit operation Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000000306 component Substances 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000001050 lubricating effect Effects 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F26—DRYING
- F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
- F26B5/00—Drying solid materials or objects by processes not involving the application of heat
- F26B5/04—Drying solid materials or objects by processes not involving the application of heat by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B30/00—Heat pumps
- F25B30/02—Heat pumps of the compression type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B31/00—Compressor arrangements
- F25B31/002—Lubrication
- F25B31/004—Lubrication oil recirculating arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
- F25B49/022—Compressor control arrangements
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/021—Inverters therefor
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
Abstract
The invention discloses a variable frequency heat pump unit and a control method thereof, wherein the variable frequency heat pump unit comprises one or more variable frequency compressors connected in parallel, an oil separator, a reversing valve, a condenser, a throttling mechanism, an evaporator, a gas-liquid separator and a variable frequency fan, wherein a normal oil return oil path and a forced oil return oil path which are connected in parallel are arranged between the oil separator and an air return port of the compressor, and a system pressure balance pipeline is arranged between a high pressure side and a low pressure side of the unit; the variable frequency heat pump unit has the advantages of strong refrigerating and heating capabilities, good energy-saving effect, short response time, flexible application and better user experience; the control method of the parallel compressors in the variable frequency heat pump unit ensures the safe, high-efficiency, stable and energy-saving operation of the variable frequency heat pump unit through the steps of starting, stopping, adding and switching, and is flexible and convenient to control; the variable frequency heat pump unit is particularly suitable for industrial and commercial users.
Description
Technical Field
The invention relates to the technical field of heat pump units, in particular to a variable frequency heat pump unit and a control method thereof.
Background
The heat pump is a mechanical device which converts low-temperature heat energy into high-temperature heat energy by utilizing manual technology so as to achieve the refrigerating/heating effect. When the heat pump operates, the heat source absorbs heat energy, and then the heat energy is converted into a higher-temperature heat source to be released into a required space, so that the heat pump can be used as heating equipment and refrigerating equipment, and the purpose of one machine for two purposes is achieved. Because the heat pump has the advantages of environmental protection, energy conservation and high efficiency, the heat pump meets the basic policy of energy source environmental protection in China at present, and the application of the heat pump unit is increasingly wide.
The compressor is whole heat pump set's core component, present heat pump set, and compressor wherein still adopts the mode of deciding frequently mostly, adopts the compressor of deciding frequently to have following not enough at least: once the set temperature is reached, the machine is automatically stopped; if the temperature does not reach the set temperature, the computer is automatically started; when the voltage is unstable and other electric faults occur, the compressor stops rotating; therefore, the heat pump unit is frequently shut down and restarted, a large amount of electric energy is consumed, the service life of the compressor is greatly shortened, and the use flexibility of the heat pump unit is greatly reduced.
At present, although a variable frequency heat pump unit is also provided, the existing variable frequency heat pump unit still has a large improvement space in the aspects of safety, high-efficiency operation, flexible control and the like, and needs to be solved by technical personnel in the field urgently.
Disclosure of Invention
In view of the above, the first technical problem to be solved by the present invention is: the variable frequency heat pump unit is safe and efficient to operate and flexible and convenient to use.
Based on a general inventive concept, the second technical problem to be solved by the present invention is: the control method of the variable frequency heat pump unit is provided, so that the safe and efficient operation of the variable frequency heat pump unit is ensured, and the control is convenient and flexible.
In order to solve the first technical problem, the technical scheme of the invention is as follows: variable frequency heat pump set, variable frequency heat pump set includes: a refrigerant circulating loop formed by connecting a compressor, an oil separator, a reversing valve, a condenser, a throttling mechanism and an evaporator in series through a refrigerant pipeline,
a normal oil return oil path and a forced oil return oil path are arranged between the oil separator and an air return port of the compressor, the forced oil return oil path is connected with the normal oil return oil path in parallel, and only a forced oil return electromagnetic valve is arranged in the forced oil return oil path;
a system pressure balance pipeline is arranged between the high-pressure side and the low-pressure side of the unit;
the compressor is provided with one compressor; or the compressors are connected in parallel with two or more compressors, and the compressors are all variable frequency compressors.
The normal oil return oil way comprises a normal oil return main oil way connected with the oil separator and a normal oil return branch oil way connected with an air return port of the compressor, one normal oil return main oil way is arranged, and the number of the normal oil return branch oil ways is the same as that of the compressors.
And a throttling capillary tube and a normal oil return electromagnetic valve are arranged in the normal oil return branch oil way.
The forced oil return oil path comprises a forced oil return main oil path connected with the oil separator and a forced oil return branch oil path connected with an air return port of the compressor, one forced oil return main oil path is arranged, the number of the forced oil return branch oil paths is the same as that of the compressors, and only one forced oil return electromagnetic valve is arranged on the forced oil return main oil path.
Wherein, a high-low pressure balance valve is arranged in the system pressure balance pipeline.
The compressor is characterized in that a compressor heavy-load starting protection pipeline is arranged between an exhaust port and an air return port of each compressor, and a heavy-load starting protection electromagnetic valve is arranged in each compressor heavy-load starting protection pipeline.
Wherein, the gas outlet of each compressor is provided with a temperature sensor.
Wherein, a gas-liquid separator is arranged between the evaporator and the return air port of the compressor.
Wherein, the evaporimeter, the condenser all is provided with the frequency conversion fan.
In order to solve the second technical problem, the technical solution of the present invention is: the control method of the compressors arranged in parallel in the variable frequency heat pump unit comprises the following steps:
s100, starting: when the unit starts to operate, the parallel compressors are sequentially started, the starting interval is T1, and resonance caused by simultaneous starting is avoided; after the unit stably runs, the running frequency of the compressor is close, but the compressor always keeps running staggered by n1, so that beat frequency is avoided;
s200, shutdown: when the unit needs to be shut down, the compressors connected in parallel need to be simultaneously reduced in frequency and then shut down; firstly reducing the frequency and then stopping the machine to ensure that the stable machine is stopped;
s300, adding: when one or more compressors are in operation and another compressor needs to be started again, the frequency of the compressor in operation needs to be reduced first to release pressure; when the other compressor is started, the system pressure balance pipeline is opened to ensure balanced starting; reducing the starting load of the compressor;
s400, switching: when one or more compressors run for a period of time and need to be switched to another compressor to run for balancing abrasion, the compressor in running needs to be firstly subjected to frequency reduction and pressure relief, and when the other compressor is started stably, the compressor is stopped.
After the technical scheme is adopted, the invention has the following beneficial effects:
because the variable frequency heat pump unit is provided with the normal oil return oil way and the forced oil return oil way which are connected in parallel between the oil separator and the air return port of the compressor, the forced oil return oil way is only provided with the forced oil return electromagnetic valve, and when the unit normally operates, lubricating oil in the oil separator flows back to the compressor through the normal oil return oil way to complete an oil return task; when the oil return task cannot be completed through a normal oil return oil way under the severe working condition, the forced oil return electromagnetic valve is opened, and forced oil return is performed through the forced oil return oil way, so that lubricating oil is ensured to flow back to the compressor, the compressor can be ensured to be lubricated fully and reliably all the time, and the compressor can run safely and reliably;
because a system pressure balance pipeline is arranged between the high-pressure side and the low-pressure side of the unit, the system pressure balance pipeline is closed when the unit normally operates; when the pressure between the high pressure side and the low pressure side needs to be balanced, a system pressure balancing pipeline is connected, the high-low pressure differential pressure of the system is prevented from being overlarge, the compressor is prevented from running under high load, and the compressor and all parts of the system are protected;
the compressor is a variable frequency compressor, so that the variable frequency compressor can adjust the running speed of the compressor at any time and cannot be frequently started, the electric energy loss caused by frequent shutdown and restart is greatly reduced, the variable frequency compressor can run in a wide voltage range, the requirement on voltage is low, and the applicability is strong; the variable frequency compressor is provided with two or more than two in parallel, so that the refrigerating and heating capacity of the unit is improved, the variable frequency compressor is particularly suitable for industrial and commercial users, the user can flexibly select the unit operation mode according to the load condition required by the site, the refrigerating/heating effect is quickly achieved, the response time is short, the user experience is good, the energy is saved, and the unit can adapt to a wider operation range.
The control method of the parallel compressors in the variable frequency heat pump unit ensures the safe, high-efficiency, stable and energy-saving operation of the unit through the steps of starting, stopping, adding and switching control, and is flexible and convenient to control.
Drawings
FIG. 1 is a schematic diagram of a variable frequency heat pump unit according to a first embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating the starting steps of the control method for two compressors of the variable frequency heat pump unit in FIG. 1;
FIG. 3 is a schematic diagram illustrating the shutdown steps of the control method for two compressors of the variable frequency heat pump unit in FIG. 1;
FIG. 4 is a schematic diagram illustrating additional steps of a method for controlling two compressors of the variable frequency heat pump unit of FIG. 1;
FIG. 5 is a schematic diagram showing the switching steps of the control method for two compressors of the variable frequency heat pump unit in FIG. 1;
FIG. 6 is a schematic view showing the starting steps of the control method for three compressors of the variable frequency heat pump unit according to the second embodiment of the present invention;
FIG. 7 is a schematic view showing the shutdown steps of the control method for three compressors of the variable frequency heat pump unit according to the second embodiment of the present invention;
FIG. 8 is a schematic view of the additional steps of the control method for three compressors of the variable frequency heat pump unit according to the second embodiment of the present invention;
FIG. 9 is a schematic diagram showing the switching steps of the control method for three compressors of the variable frequency heat pump unit according to the second embodiment of the present invention;
in the figure: 1-1# compressor; 2-2# compressor; 3-a temperature sensor; 4-a one-way valve; 5-an oil separator; 6-a condenser; 7-a throttling mechanism; 8-an evaporator; 9-a reversing valve; 10 a-a throttling capillary; 10 b-normal oil return electromagnetic valve; 11-heavy load starting protection electromagnetic valve; 12-a gas-liquid separator; 13-a variable frequency fan; a-normal oil return path; b, forced oil return oil way; b1-forced oil return electromagnetic valve; c-a pressure balancing line; c1-high and low pressure balancing valve.
Detailed Description
The embodiments described below in connection with the drawings are illustrative only and should not be construed as limiting the invention.
It should be noted that in the description of the present invention, unless otherwise specified or limited, the terms "connected," "connecting," and the like are to be construed broadly, and may be, for example, mechanical or electrical or hydraulic connections; the two elements may be directly connected or indirectly connected through an intermediate medium, and specific meanings of the above terms may be understood by those skilled in the art according to specific situations.
Example one
As shown in fig. 1, the variable frequency heat pump unit according to the first embodiment of the present invention includes: a refrigerant circulation loop formed by connecting a compressor, an oil separator 5, a reversing valve 9, a condenser 6, a throttling mechanism 7 and an evaporator 8 in series through refrigerant pipelines; a normal oil return path A and a forced oil return path B which are connected in parallel are arranged between the oil separator 5 and an air return port of the compressor; and a system pressure balance pipeline C is arranged between the high-pressure side and the low-pressure side of the unit.
Wherein, the compressor is provided with two in parallel, namely 1# compressor 1 and 2# compressor 2 to all be inverter compressor. The variable frequency compressor can adjust the running speed of the compressor at any time, is not frequently started, greatly reduces the electric energy loss caused by frequent shutdown and restart, can run in a wide voltage range, has lower requirement on voltage and stronger applicability; the two variable frequency compressors are arranged in parallel, so that the refrigerating and heating capacity of the unit is improved, the unit is particularly suitable for industrial and commercial users, the user can flexibly select the unit operation mode according to the load condition required by the site, the refrigerating/heating effect is quickly achieved, and the response time is short.
Wherein, all be provided with the compressor heavy load and start the protection pipeline between the gas vent of every compressor and the return-air inlet, be provided with heavy load start protection solenoid valve 11 in the compressor heavy load starts the protection pipeline. When the compressor is started under the heavy load condition, the heavy load starting protection electromagnetic valve 11 is opened to balance the pressure between the high pressure side and the low pressure side of the compressor, and the compressor is started under the heavy load condition to form reliable protection.
Wherein, a one-way valve 4 is arranged in the exhaust pipeline of each compressor; the exhaust port of each compressor is provided with a temperature sensor 3, the temperature sensors 3 are used for detecting the exhaust temperature of the compressor, if the exhaust temperature is too high, protective measures are taken for the compressor, and the phenomenon that the lubricating oil becomes thin even charred and coked due to too high exhaust temperature, so that the lubricating condition of the compressor is deteriorated and the operation of the compressor is unfavorable is prevented.
The normal oil return oil path A comprises a normal oil return main oil path connected with the oil separator 5 and normal oil return branch oil paths connected with the air return ports of the compressors, one normal oil return main oil path is arranged, and the number of the normal oil return branch oil paths is the same as that of the compressors. And a throttling capillary tube 10a and a normal oil return electromagnetic valve 10b are arranged in the normal oil return branch oil way. When the unit normally operates, the lubricating oil in the oil separator 5 flows back to the compressor through the normal oil return way A to complete the oil return task.
The forced oil return passage B is provided with only a forced oil return solenoid valve B1. The forced oil return path B includes a main forced oil return path connected to the oil separator 5 and a branch forced oil return path connected to the return port of the compressor, the main forced oil return path is provided with one branch forced oil return path, the number of the branch forced oil return paths is the same as that of the compressors, and only the main forced oil return path is provided with one solenoid valve B1. When the oil return task cannot be completed through the normal oil return path A under the severe working condition, the forced oil return electromagnetic valve B1 is opened, and forced oil return is performed through the forced oil return path B, so that the lubricating oil can flow back to the compressor, the compressor can be ensured to be lubricated fully and reliably all the time, and the compressor can be operated safely and reliably.
Wherein, a high-low pressure balance valve C1 is arranged in the system pressure balance pipeline C, and the high-low pressure balance valve C1 is preferably a solenoid valve. When the unit normally operates, the system pressure balance pipeline C is closed; when the pressure between the high pressure side and the low pressure side needs to be balanced, the system pressure balance pipeline C is communicated, the high-low pressure differential pressure of the system is prevented from being overlarge, the compressor is prevented from running under high load, and the compressor and all parts of the system are protected.
A gas-liquid separator 12 is also provided between the evaporator 8 and the return air port of the compressor. The liquid refrigerant is prevented from entering the compressor to cause liquid impact on the compressor, and meanwhile, the dilution of the lubricating oil of the compressor by excessive refrigerant is prevented, and the normal operation of the system is guaranteed.
Wherein, the evaporator 8 and the condenser 6 are both provided with a variable frequency fan 13. The fan is arranged to heat at a quick heating speed, and the fan operates in a frequency conversion mode, so that the power consumption is low, the energy-saving effect is obvious, and the field adaptability is good.
The normal operation flow of the variable frequency heat pump unit shown in fig. 1 is as follows: after receiving a starting signal (for example, refrigeration), the 1# compressor 1 and the 2# compressor 2 are started, the refrigerant is compressed from a low-temperature low-pressure gas state to a high-temperature high-pressure gas state, enters the oil separator 5 through the check valve 4, passes through the oil separator 5 and the reversing valve 9 (usually adopting a four-way valve), passes through the reversing valve 9 and then enters the condenser 6, the high-temperature high-pressure gas refrigerant is changed into a high-temperature high-pressure liquid refrigerant after passing through the condenser 6, then passes through the throttling mechanism 7, the refrigerant is changed from the high-temperature high-pressure liquid state to the low-temperature low-pressure liquid state after passing through the throttling mechanism 7, passes through the evaporator 8, the refrigerant is changed from the low-temperature low-pressure liquid state to the low-temperature low-pressure gas state after passing through the reversing valve 9 and then enters the gas-liquid separator 12. When the heating working condition is met, the reversing valve 9 is used for reversing to realize the heating function, and the details are not repeated.
In the variable frequency heat pump unit shown in fig. 1, the control method of two compressors arranged in parallel is as follows:
s100, starting: as shown in fig. 2, when the unit starts to operate, the parallel 1# compressor 1 (comp 1) and 2# compressor 2 (comp 2) start sequentially, the start interval time is T1, so that the resonance phenomenon caused by simultaneous start can be avoided, wherein the value of T1 is preferably about 90 seconds; after the unit stably operates, the operating frequencies of the two compressors are close, but the two compressors always operate in a staggered mode of n1, so that the beat frequency phenomenon is avoided, wherein the value of n1 is preferably within the range of 3-8rps (rps is the revolution per second, and the frequency and the rotating speed are equal in value when the unit of rotating speed takes rps under the condition that each component of the unit is determined).
S200, shutdown: as shown in fig. 3, when the unit needs to be shut down, two compressors connected in parallel need to be shut down at the same time and then shut down; the frequency is reduced first and then the machine is stopped, so that the stable machine is ensured to be stopped.
S300, adding: as shown in fig. 4, when one compressor (for example, the # 1 compressor 1) is in operation and another compressor (for example, the # 2 compressor 2) needs to be started again, the frequency of the operating # 1 compressor 1 needs to be reduced first to perform pressure relief; when the 2# compressor 2 is started, the heavy-load starting protection electromagnetic valve 11 of the 2# compressor is switched on, so that the pressure between the high-pressure side and the low-pressure side of the 2# compressor 2 is rapidly balanced, the compressor is ensured to be started under the condition of pressure balance, the starting load is reduced, and the step loss is avoided.
S400, switching: as shown in fig. 5, when one compressor (for example, the # 1 compressor 1) operates for a period of time and needs to be switched to another compressor (i.e., the # 2 compressor 2) to balance wear, the 1# compressor 1 in operation needs to be frequency-reduced and pressure-relieved first, and when the # 2 compressor 2 is started stably, the # 1 compressor 1 is stopped again to realize smooth switching between compressors.
Example two
As shown in fig. 6 to 9, and with reference to fig. 1: the variable frequency heat pump unit of the second embodiment of the invention has basically the same structure as the variable frequency heat pump unit of the first embodiment shown in fig. 1, and the difference is that: in the second embodiment, three variable-frequency compressors (namely comp1, comp2 and comp3) are arranged in parallel in the variable-frequency heat pump unit, and are not shown in detail here.
In the variable frequency heat pump unit of the second embodiment of the present invention, the control method of the three compressors is basically the same as the control method of the two compressors of the first embodiment, and further description is omitted here.
Obviously, in the variable frequency heat pump unit of the present invention, the number of the variable frequency compressors includes, but is not limited to, the above two or three parallel connection situations, and the number of the variable frequency compressors may be increased or decreased appropriately according to actual requirements, for example, in the case of low user side load, only one variable frequency compressor may be arranged in the unit, and the control of only one variable frequency compressor arranged in the unit is simple, which is known by those skilled in the art and will not be described herein again. Under the condition that the load on the user side is high, the number of the frequency conversion compressors connected in parallel in the unit can exceed three, and the control of the frequency conversion compressors exceeding three can refer to fig. 2 to 9, which is not described again here.
The foregoing is illustrative of the preferred embodiments of the present invention, and details which have not been given in detail are known in the art, and are not to be construed as limitations on the scope of the invention except as set forth in the following claims.
Claims (10)
1. Variable frequency heat pump set, variable frequency heat pump set includes: a refrigerant circulating loop formed by connecting a compressor, an oil separator, a reversing valve, a condenser, a throttling mechanism and an evaporator in series through a refrigerant pipeline, and is characterized in that,
a normal oil return oil path and a forced oil return oil path are arranged between the oil separator and an air return port of the compressor, the forced oil return oil path is connected with the normal oil return oil path in parallel, and only a forced oil return electromagnetic valve is arranged in the forced oil return oil path;
a system pressure balance pipeline is arranged between the high-pressure side and the low-pressure side of the unit;
the compressor is provided with one compressor; or the compressors are connected in parallel with two or more compressors, and the compressors are all variable frequency compressors.
2. The variable-frequency heat pump unit according to claim 1, wherein the normal oil return path includes a normal oil return main path connected to the oil separator and a normal oil return branch path connected to the return port of the compressor, and there is one normal oil return main path, and the number of the normal oil return branch paths is the same as the number of the compressors.
3. The variable frequency heat pump unit according to claim 2, wherein a throttling capillary tube and a normal oil return electromagnetic valve are arranged in the normal oil return branch oil path.
4. The variable-frequency heat pump unit according to claim 1, wherein the forced oil return path includes a main forced oil return path connected to the oil separator and a branch forced oil return path connected to the return port of the compressor, the number of the main forced oil return paths is the same as that of the compressors, and only one solenoid valve is provided in the main forced oil return path.
5. The variable frequency heat pump unit according to claim 1, wherein a high-low pressure balance valve is arranged in the system pressure balance pipeline.
6. The variable frequency heat pump unit according to claim 1, wherein a compressor heavy-duty start-up protection line is disposed between the exhaust port and the return port of each compressor, and a heavy-duty start-up protection solenoid valve is disposed in the compressor heavy-duty start-up protection line.
7. The variable frequency heat pump unit of claim 1, wherein a temperature sensor is provided at the exhaust port of each compressor.
8. The variable frequency heat pump unit of claim 1, wherein a gas-liquid separator is disposed between the evaporator and the return port of the compressor.
9. The variable frequency heat pump unit according to claim 1, wherein the evaporator and the condenser are provided with variable frequency fans.
10. The method for controlling the variable-frequency heat pump unit according to any one of claims 1 to 9, wherein the method for controlling the compressors arranged in parallel comprises the steps of:
s100, starting: when the unit starts to operate, the parallel compressors are sequentially started, and the starting interval is T1; after the unit stably operates, the compressor always keeps operating in a staggered n1 mode;
s200, shutdown: when the unit needs to be shut down, the compressors connected in parallel need to be simultaneously reduced in frequency and then shut down;
s300, adding: when one or more compressors are in operation and another compressor needs to be started again, the frequency of the compressor in operation needs to be reduced first to release pressure; when the other compressor is started, the system pressure balance pipeline is opened to ensure balanced starting;
s400, switching: when one or more compressors run for a period of time and need to be switched to another compressor to run for balancing abrasion, the compressor in running needs to be firstly subjected to frequency reduction and pressure relief, and when the other compressor is started stably, the compressor is stopped.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115451612A (en) * | 2022-08-23 | 2022-12-09 | 青岛海尔空调电子有限公司 | Method and device for drying system oil return, drying system and storage medium |
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| CN115451612B (en) * | 2022-08-23 | 2024-02-23 | 青岛海尔空调电子有限公司 | Method and device for oil return of drying system, drying system and storage medium |
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