CN114484715B - Multi-compressor refrigerant circulation system and control method thereof - Google Patents

Multi-compressor refrigerant circulation system and control method thereof Download PDF

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Publication number
CN114484715B
CN114484715B CN202210022941.XA CN202210022941A CN114484715B CN 114484715 B CN114484715 B CN 114484715B CN 202210022941 A CN202210022941 A CN 202210022941A CN 114484715 B CN114484715 B CN 114484715B
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compressor
current
oil
oil temperature
compressors
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CN114484715A (en
Inventor
国德防
毛守博
时斌
禚百田
程绍江
张锐钢
王军
高玉辉
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Qingdao Haier Air Conditioner Gen Corp Ltd
Qingdao Haier Air Conditioning Electric Co Ltd
Haier Smart Home Co Ltd
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Qingdao Haier Air Conditioner Gen Corp Ltd
Qingdao Haier Air Conditioning Electric Co Ltd
Haier Smart Home Co Ltd
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/30—Control or safety arrangements for purposes related to the operation of the system, e.g. for safety or monitoring
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/50—Control or safety arrangements characterised by user interfaces or communication
    • F24F11/61—Control or safety arrangements characterised by user interfaces or communication using timers
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
    • F24F11/63—Electronic processing
    • F24F11/64—Electronic processing using pre-stored data
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/70—Control systems characterised by their outputs; Constructional details thereof
    • 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
    • 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
    • F25B41/00—Fluid-circulation arrangements
    • F25B41/20—Disposition of valves, e.g. of on-off valves or flow control valves
    • 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
    • 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

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Combustion & Propulsion (AREA)
  • Chemical & Material Sciences (AREA)
  • Thermal Sciences (AREA)
  • Signal Processing (AREA)
  • Fuzzy Systems (AREA)
  • Mathematical Physics (AREA)
  • Human Computer Interaction (AREA)
  • Control Of Positive-Displacement Pumps (AREA)
  • Air Conditioning Control Device (AREA)

Abstract

The invention discloses a multi-compressor refrigerant circulation system and a control method thereof, wherein the method comprises the following steps: when a plurality of compressors in the system are in an operating state, acquiring the current oil temperature of each compressor in the operating state in real time, and comparing the current oil temperature with the corresponding oil temperature threshold of the compressor; when the number of the compressors of which the current oil temperature is not higher than the corresponding oil temperature threshold is not less than two, acquiring the current operating frequency of each compressor of which the current oil temperature is not higher than the corresponding oil temperature threshold; determining a current oil demand of the corresponding compressor based on the current operating frequency and the current oil temperature; sequencing all the obtained current oil demand according to the order of magnitude; and determining the state of the controllable valve connected with each compressor according to the sequencing. By the method, the oil return control precision of the multiple compressors can be improved, and the operation stability of the refrigerant circulation system can be improved.

Description

Multi-compressor refrigerant circulation system and control method thereof
Technical Field
The invention belongs to the technical field of refrigeration, in particular to a refrigerant circulation system, and more particularly relates to a multi-compressor refrigerant circulation system and a control method thereof.
Background
In the multi-split air conditioner system, an outdoor unit is connected with a plurality of indoor units. Because the load difference of the indoor units is relatively large, the indoor units are sometimes operated rarely, and the indoor units are sometimes fully opened. In order to meet different load demands and maximally realize energy conservation, more than two compressors are usually arranged in parallel in the outdoor unit to form a multi-compressor refrigerant system, and one or more compressors can be selected to operate according to the load of the internal unit.
A key problem of a multi-compressor refrigerant circulating system with a plurality of compressors connected in parallel is the oil return problem of the compressors. In the prior art, each compressor in a multi-compressor refrigerant circulation system is correspondingly provided with an oil separator, and the suction end of each compressor is connected with the corresponding oil separator through a capillary tube. When the compressor runs, compressor oil discharged from the exhaust end of the compressor is separated by the oil separator and then flows back to the compressor from the capillary tube, so that the normal lubrication of the compressor is ensured. The oil return mode is simpler, but when in actual operation, even two compressors with the same specification operate at the same operating frequency, the quantity of the compressor oil separated by the oil separator is difficult to be ensured to be consistent under the influence of the actual characteristics of each part, more oil return of one compressor and less oil return of the other compressor can occur, and the compressor is easy to be damaged due to oil shortage. In actual operation, the plurality of compressors are controlled by respective protection parameters, and the operation frequencies are often different. In addition, in order to meet the load requirements of various indoor units, energy conservation is realized to the greatest extent, and a plurality of compressor combinations with different specifications are often adopted to be installed in the same outdoor unit. The compressors with different specifications and different operating frequencies are operated in parallel, so that the oil return balance problem is more outstanding and difficult to solve.
In order to effectively solve the oil return balance problem of compressors, chinese patent application publication No. CN106839330A discloses an oil balance control method, and oil return balance is carried out among a plurality of compressors through an oil balance pipeline. During oil return control, the oil temperature of the compressor is collected to indirectly obtain the oil quantity state of the compressor, when the oil temperature is abnormal, the oil quantity is judged to be abnormal, and oil return is balanced by utilizing an oil balance pipeline; and when the oil temperature is normal, determining that the oil quantity is proper, and maintaining the current working state unchanged. By adopting the method, although the balance of oil return of different compressors can be improved, the method only can roughly estimate the oil quantity of the compressors based on the oil temperature, and the problem of unbalanced oil return can still exist when the oil temperature is normal, so that the oil return balance is inaccurately regulated and controlled, and the operation stability of the multi-compressor refrigerant circulation system is affected.
Disclosure of Invention
The invention aims to provide a control method of a multi-compressor refrigerant circulation system, which improves the accuracy of balanced oil return control of multiple compressors and improves the operation stability of the refrigerant circulation system.
In order to achieve the above object, the present invention provides a control method for a multi-compressor refrigerant cycle system, which is implemented by adopting the following technical scheme:
a method of controlling a multi-compressor refrigerant cycle system, the method comprising:
when a plurality of compressors in the system are in an operating state, acquiring the current oil temperature of each compressor in the operating state in real time, and comparing the current oil temperature of each compressor with an oil temperature threshold corresponding to the compressor;
when the number of compressors meeting the condition that the current oil temperature is not higher than the corresponding oil temperature threshold value is not less than two, executing the following oil return balance control process:
acquiring the current operating frequency of each compressor of which the current oil temperature is not higher than the corresponding oil temperature threshold value;
determining a current oil demand of the corresponding compressor based on the current operating frequency and the current oil temperature;
sequencing all the obtained current oil demand according to the order of magnitude;
determining the state of a controllable valve connected with each compressor of which the current oil temperature is not higher than the corresponding oil temperature threshold according to the sequencing;
the controllable valves are connected in parallel with oil return capillaries connected with the corresponding compressors and the oil separators corresponding to the compressors.
In one preferred embodiment, determining, according to the ranking, a state of a controllable valve connected to each compressor for which the current oil temperature is not higher than the corresponding oil temperature threshold value specifically includes:
acquiring the current minimum oil demand and the current maximum oil demand in the sequencing;
when the ratio of the current maximum oil demand to the current minimum oil demand is larger than a first ratio coefficient, controlling the controllable valve connected with the current maximum oil demand compressor to be in an open state and controlling the controllable valve connected with the current minimum oil demand compressor to be in a closed state; the first scale factor is a positive number greater than 1
And when the ratio of the current maximum oil demand to the current minimum oil demand is not greater than the first ratio coefficient, controlling a controllable valve connected with each compressor with the current oil temperature not higher than the corresponding oil temperature threshold to be in an open state.
In one preferred embodiment, the method further comprises:
when the ratio of the current maximum oil demand to the current minimum oil demand is greater than the first ratio, controlling the controllable valve connected with the current maximum oil demand compressor to be in an open state, and controlling the controllable valve connected with the current minimum oil demand compressor to be in a closed state, and then controlling the states of the controllable valves connected with the current other oil demand compressors in the sequence by adopting the following processes:
when the ratio of each current other oil demand to the current maximum oil demand is smaller than a second proportionality coefficient, controlling the controllable valve connected with the current other oil demand compressor to be in a closed state; otherwise, controlling the controllable valve connected with the compressor with the current other oil demands to be in an open state; the second scaling factor is a positive number less than 1.
In one of the preferred embodiments, determining the current oil demand of the corresponding compressor based on the current operating frequency and the current oil temperature specifically includes:
determining the current oil demand Q of the nth compressor by the following method n ：
Q n = Q nmax *[r n *f n /f nmax +(1-r n )*t n /t nmax ];
Wherein N is the number of compressors, n=1, 2, … …, N, N is the total number of compressors in the refrigerant circulation system, N is more than or equal to 2, Q nmax 、f nmax 、t nmax The maximum oil demand, the maximum operating frequency and the oil temperature threshold of the nth compressor are respectively set; r is (r) n Is a known regulating factor, is a positive number less than 1; f (f) n 、t n The current operating frequency and the current oil temperature are respectively.
In one preferred embodiment, the method further comprises:
and when the current oil temperature of the compressor in the running state is higher than the corresponding oil temperature threshold value, controlling the controllable valve connected with the compressor to be in an open state.
In one preferred embodiment, the method further comprises:
after a plurality of compressors are powered on and started to operate, firstly controlling all controllable valves connected with all operating compressors to be in an open state, and continuing for a first time; then, controlling all the controllable valves connected with all the running compressors to be in a closed state; and then executing the process of acquiring the current oil temperature in real time.
In one preferred embodiment, the method further comprises:
when one compressor is in the system in the running state, controlling the controllable valves connected with all compressors in the stopping state to be in the closing state, and controlling the states of the controllable valves connected with the one compressor in the running state according to the following processes:
acquiring the current oil temperature of the compressor in an operating state in real time, and comparing the current oil temperature with the corresponding oil temperature threshold of the compressor;
when the current oil temperature of the one compressor is higher than the oil temperature threshold corresponding to the one compressor, controlling the controllable valve connected with the one compressor to be in an open state; otherwise, the controllable valve connected with the compressor is controlled to be in a closed state.
The second purpose of the invention is to provide a multi-compressor refrigerant circulation system with high oil return balance control precision and strong operation stability.
In order to achieve the above object, the present invention provides a multi-compressor refrigerant cycle system implemented by adopting the following technical scheme:
a multi-compressor refrigerant cycle system comprising a plurality of compressors and an oil separator connected to each compressor by an oil return capillary tube, the system further comprising:
the number of the controllable valves is more than one, which is matched with the number of the compressors, and each controllable valve is connected with the oil return capillary corresponding to one compressor in parallel;
the system further includes a multi-compressor refrigerant cycle system control device, the device comprising:
the current oil temperature acquisition unit is used for acquiring the current oil temperature of each compressor in an operating state in real time;
the current oil temperature comparison unit is used for comparing the current oil temperature with the corresponding oil temperature threshold value of the compressor and outputting a comparison result;
a current oil demand determining unit, configured to obtain a current operating frequency of the compressor for which the current oil temperature is not higher than the corresponding oil temperature threshold value, and determine a current oil demand of the corresponding compressor based on the current operating frequency and the current oil temperature;
and the control unit is configured to rank the obtained current oil demands of all the compressors with the current oil temperatures not higher than the corresponding oil temperature threshold according to the size sequence when the number of the compressors with the current oil temperatures not higher than the corresponding oil temperature threshold is not less than two, and determine the state of the controllable valve connected with each compressor with the current oil temperatures not higher than the corresponding oil temperature threshold according to the rank.
In one preferred embodiment, the control unit is further configured to:
when the current oil temperature of the compressor in an operating state is higher than the corresponding oil temperature threshold value, controlling the controllable valve connected with the compressor to be in an open state; and
after a plurality of compressors are powered on and started to operate, firstly controlling all controllable valves connected with all operating compressors to be in an open state, and continuing for a first time; then, controlling all the controllable valves connected with all the running compressors to be in a closed state; and then the current oil temperature acquisition unit acquires the current oil temperature of each compressor in the running state in real time.
It is still another object of the present invention to provide an electronic device including a processor, a memory, and a computer program stored on the memory, the processor being configured to execute the computer program to implement the above-mentioned multi-compressor refrigerant cycle system control method.
Compared with the prior art, the invention has the advantages and positive effects that:
according to the multi-compressor refrigerant circulation system and the control method thereof, the controllable valve is arranged in parallel at the oil return capillary tube of the oil separator corresponding to each compressor, the oil temperature of the compressors is detected to serve as a parameter for roughly estimating the oil quantity of the compressors, when the oil temperatures of the compressors are all in a preset normal range, the actual oil quantity of the compressors is determined more accurately by utilizing the operating frequency and the oil temperature of the compressors, the state of the controllable valve is controlled according to the actual oil quantity, the oil return control of the multi-compressor system is realized, the more accurate oil return balance control of the multi-compressors is achieved, the normal and reliable operation of the compressors is ensured, and the operation stability of the refrigerant circulation system is improved.
Other features and advantages of the present invention will become apparent upon review of the detailed description of the invention in conjunction with the drawings.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic view of a portion of one embodiment of a multi-compressor refrigerant cycle system according to the present invention;
FIG. 2 is a flow chart of one embodiment of a method of controlling a multi-compressor refrigerant cycle system in accordance with the present invention;
FIG. 3 is a schematic flow chart of another embodiment of a method for controlling a multi-compressor refrigerant cycle system according to the present invention;
FIG. 4 is a schematic view of an embodiment of a control device in a multi-compressor refrigerant cycle system according to the present invention;
fig. 5 is a schematic structural diagram of an embodiment of the electronic device of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be further described in detail with reference to the accompanying drawings and examples.
It should be noted that, the technical solutions of the embodiments of the present invention may be combined with each other, but it is necessary to be based on the fact that those skilled in the art can implement the technical solutions, and when the technical solutions are contradictory or cannot be implemented, it should be considered that the technical solutions are not combined, and are not within the scope of protection claimed by the present invention.
Fig. 1 is a schematic view showing a partial structure of an embodiment of a multi-compressor refrigerant cycle system according to the present invention. Specifically, the embodiment is a multi-compressor refrigerant cycle system formed by three compressors connected in parallel.
As shown in fig. 1, the multi-compressor refrigerant cycle system of this embodiment includes a first compressor 111, a second compressor 121, and a third compressor 131, which are connected in parallel in the refrigerant cycle system, and the three compressors may be identical in model or specification or different in specification.
The first compressor 111 has a discharge end and a suction end, and the first oil separator 112 has a refrigerant inlet end and an oil discharge end as a structure corresponding to the first compressor 111. The refrigerant inlet end of the first oil separator 112 is connected to the discharge end of the first compressor 111, and the oil discharge end of the first oil separator 112 is connected to the suction end of the first compressor 111 through a first capillary tube 113. The first capillary 113 is also connected in parallel with a first controllable valve 114. The first controllable valve 114 may be a solenoid valve.
The second compressor 121 has a discharge end and a suction end, and the second oil separator 122 has a refrigerant inlet end and an oil discharge end as a structure corresponding to the second compressor 121. The refrigerant inlet end of the second oil separator 122 is connected to the discharge end of the second compressor 121, and the oil discharge end of the second oil separator 122 is connected to the suction end of the second compressor 121 through a second capillary tube 123. The second capillary tube 123 is also connected in parallel with a second controllable valve 124. The second controllable valve 124 may be a solenoid valve.
The third compressor 131 has a discharge end and a suction end, and the third oil separator 132 has a refrigerant inlet end and an oil discharge end as a structure corresponding to the third compressor 131. The refrigerant inlet end of the third oil separator 132 is connected to the discharge end of the third compressor 131, and the oil discharge end of the third oil separator 132 is connected to the suction end of the third compressor 131 through a third capillary tube 133. The third capillary tube 133 is also connected in parallel with a third controllable valve 134. The third controllable valve 134 may be a solenoid valve.
The refrigerant cycle system further includes a first temperature detecting unit 155 provided at the bottom of the first compressor 111, a second temperature detecting unit 125 provided at the bottom of the second compressor 121, and a third temperature detecting unit 135 provided at the bottom of the third compressor 131, with which the temperature of oil in the corresponding compressor can be detected.
In this embodiment, after the compressor oil discharged during the operation of the first compressor 111 is separated by the first oil separator 112, the compressor oil may slowly flow back to the first compressor 101 through the first capillary tube 113, and may also flow back to the first compressor 101 through the first controllable valve 114 at a relatively large flow rate. Similarly, after the compressor oil discharged from the second compressor 121 during operation is separated by the second oil separator 122, the compressor oil may slowly flow back to the second compressor 121 through the second capillary tube 123, and may also flow back to the second compressor 121 at a larger flow rate through the second controllable valve 124. After the compressor oil discharged during the operation of the third compressor 131 is separated by the third oil separator 132, it may slowly flow back to the third compressor 131 through the third capillary tube 133, and may also flow back to the third compressor 131 at a relatively large flow rate through the third controllable valve 134.
In addition, the multi-compressor refrigerant circulation system further comprises a control device, the control device is used for controlling the on-off states of the three controllable valves, and the balance of lubricating oil among the three compressors under different working conditions can be achieved. More specific structure of the control device, and control method, process, etc. for achieving balance of compressor oil are described in the following.
FIG. 2 is a flow chart of an embodiment of a method for controlling a multi-compressor refrigerant cycle system according to the present invention.
As shown in fig. 2, this embodiment adopts the following procedure to achieve balanced oil return control of lubricating oil when a plurality of compressors are simultaneously operated in a refrigerant cycle system.
Step 201: when a plurality of compressors in the system are in an operating state, the current oil temperature of each compressor in the operating state is obtained in real time.
The current oil temperature of the compressor is the temperature of the bottom of the compressor obtained in real time according to the set sampling frequency, and the temperature can reflect the oil quantity in the compressor. Generally, the lower the amount of oil in the compressor, the higher the temperature. Moreover, the oil quantity is determined in a temperature detection mode, a temperature detection device is arranged at the bottom of the compressor, and the detection structure is simple and easy to realize.
Step 202: and executing the oil return balance control process when the number of compressors meeting the condition that the current oil temperature is not higher than the corresponding oil temperature threshold value is not less than two.
Each compressor has an oil temperature threshold value, which is a known value, is an allowable oil temperature limit value for the compressors, and the oil temperature thresholds for different compressors may be the same or different. If the current oil temperature of the compressor is not higher than the corresponding oil temperature threshold value, the oil temperature in the compressor is normal. When the number of compressors in the operation state and the oil temperature is normal is not less than two, the oil return balance control process of step 203 and step 204 is performed on the plurality of compressors.
Step 203: acquiring the current operating frequency of each compressor with the current oil temperature not higher than the corresponding oil temperature threshold value; the current oil demand of the corresponding compressor is determined based on the current operating frequency and the current oil temperature.
And respectively acquiring the current operating frequency of each compressor in an operating state, wherein the current oil temperature is not higher than the corresponding oil temperature threshold value, and then respectively determining the current oil demand of each compressor according to the current operating frequency and the current oil temperature of each compressor.
Step 204: sequencing all the acquired current oil demands according to the order of magnitude; and determining the state of a controllable valve connected with each compressor with the current oil temperature not higher than the corresponding oil temperature threshold according to the sequencing, thereby realizing the oil return balance control of multiple compressors. Wherein, as shown in fig. 1, the controllable valves are connected in parallel with the oil return capillaries connecting the corresponding compressors and their corresponding oil separators.
In the embodiment, the controllable valve is arranged in parallel at the oil return capillary of the oil separator corresponding to each compressor, the oil temperature of the compressors is detected to be used as a parameter for roughly estimating the oil quantity of the compressors, when the oil temperatures of the compressors are all in a preset normal range, the actual oil quantity of the compressors is more accurately determined by using the operating frequency of the compressors and the oil temperature, the state of the controllable valve is controlled according to the actual oil quantity, the oil return control of a multi-compressor system is realized, the more accurate oil return balance control of the multi-compressors is realized, the normal and reliable operation of the compressors is ensured, and the operation stability of a refrigerant circulation system is improved.
In other preferred embodiments, determining, according to the sequencing, the state of the controllable valve connected to each compressor having a current oil temperature not higher than the corresponding oil temperature threshold value specifically includes:
the current minimum oil demand and the current maximum oil demand in the sequencing are obtained.
When the ratio of the current maximum oil demand to the current minimum oil demand is larger than the first ratio coefficient, the controllable valve connected with the compressor with the current maximum oil demand is controlled to be in an open state, and the controllable valve connected with the compressor with the current minimum oil demand is controlled to be in a closed state. Wherein the first scaling factor is a positive number greater than 1. Preferably, the first ratio coefficient is 1.2. When the ratio of the current maximum oil demand to the current minimum oil demand is larger than the first ratio coefficient, the oil demand of the compressor corresponding to the current maximum oil demand is larger, and the oil demand of the compressor corresponding to the current minimum oil demand is smaller. In this state, the controllable valve connected to the compressor controlling the current maximum oil demand is opened, so that the lubricating oil flows back to the compressor rapidly through the opened controllable valve, and the lubricating oil is replenished in time; and simultaneously, closing a controllable valve connected with the compressor with the current minimum oil demand, so that the system can provide as much lubricating oil as possible for the compressor corresponding to the current maximum oil demand.
When the ratio of the current maximum oil demand to the current minimum oil demand is not greater than the first ratio coefficient, the oil demand of each running compressor with the current oil temperature not higher than the corresponding oil temperature threshold is basically balanced, and in the state, the controllable valves connected with the compressors are controlled to be in an open state so as to keep the oil quantity of each compressor relatively stable.
In other preferred embodiments, when the ratio of the current maximum oil demand to the current minimum oil demand is greater than the first ratio, the controllable valve connected to the compressor controlling the current maximum oil demand is in an open state, and after the controllable valve connected to the compressor controlling the current minimum oil demand is in a closed state, the controllable valves connected to the compressors controlling the current other oil demands in the sequence are controlled in the following process. The current other oil demand refers to all current oil demands except the current maximum oil demand and the current minimum oil demand in the sequence.
Comparing each current other oil demand with the current maximum oil demand, and controlling a controllable valve connected with the compressor of the current other oil demand to be in a closed state when the ratio of the current other oil demand to the current maximum oil demand is smaller than a second proportionality coefficient; otherwise, the controllable valve connected with the compressor for controlling the current other oil demand is in an open state. Wherein the second scaling factor is a positive number less than 1. Preferably, the second scaling factor is 0.8. If the ratio of the current other oil demand to the current maximum oil demand is smaller than the second proportionality coefficient, the controllable valve connected with the corresponding compressor is controlled to be closed, so that the system can provide as much lubricating oil as possible to the corresponding compressor with the current maximum oil demand.
In other preferred embodiments, the current oil demand of the compressor is determined using the following method:
let current oil demand Q of nth compressor n ，Q n = Q nmax *[r n *f n /f nmax +(1-r n )*t n /t nmax ]。
Wherein N is the number of compressors, n=1, 2, … …, N is the total number of compressors in the refrigerant cycle system, and N is not less than 2. For example, the multi-compressor refrigerant cycle system of fig. 1 includes three compressors, n=3. Q (Q) nmax 、f nmax 、t nmax The maximum oil demand, the maximum operating frequency, and the oil temperature threshold of the nth compressor are all known values. r is (r) n Is a known adjustment factor, a positive number less than 1. In some embodiments, r n The value is 0.3-0.8.f (f) n 、t n The current operating frequency and the current oil temperature are real-time detection values respectively.
FIG. 3 is a flow chart of an embodiment of a method for controlling a multi-compressor refrigerant cycle system according to the present invention.
As shown in fig. 3, this embodiment employs the following procedure to achieve balanced oil return control of a plurality of compressors in a refrigerant cycle system.
Step 301: after the compressors are powered on and started to operate, the controllable valves connected with all the operating compressors are controlled to be in an open state and last for a first time.
The first time is a predetermined value, such as 10 minutes. After a plurality of compressors in the system are electrified and started to operate, the controllable valves corresponding to all the operating compressors are controlled to be opened at first, so that lubricating oil in the whole refrigerant circulation system is rapidly circulated, and the accuracy of the subsequent oil temperature measurement is improved.
Step 302: and controlling all the controllable valves connected with the compressors to be in a closed state.
After the controllable valve is opened for a set first time, all the opened controllable valves are closed again, and then subsequent regulation and control are performed.
Step 303: the current oil temperature of each compressor in an operating state is obtained in real time.
The specific measuring method is referred to in the corresponding description of the previous embodiments.
Step 304: and for the compressors with the current oil temperatures higher than the corresponding oil temperature thresholds, controlling the controllable valves connected with the compressors to be in an open state.
The current oil temperatures obtained in step 303 are compared with corresponding oil temperature thresholds, respectively. If the current oil temperature of a certain compressor is higher than the oil temperature threshold value, the controller can control the valve to be in an open state, so that lubricating oil is supplemented for the compressor, and unstable system operation and even damage to the compressor caused by oil shortage are reduced.
Step 305: and judging whether a compressor with the current oil temperature not higher than the oil temperature threshold exists or not. If yes, go to step 306; otherwise, go to step 305 to continue the determination of the oil temperature.
Step 306: and judging whether the number of the compressors with the current oil temperature not higher than the oil temperature threshold value is not less than two. If yes, go to step 308; otherwise, step 307 is performed.
Step 307: the state remains.
If the number of compressors whose current oil temperature is not higher than the oil temperature threshold is less than two, that is, if the oil temperature of only one operating compressor is not higher than the oil temperature threshold, the state of the corresponding controllable valve is kept unchanged, and then the determination in step 306 is continued.
Step 308: acquiring the current operating frequency of each compressor with the current oil temperature not higher than the corresponding oil temperature threshold value; the current oil demand of the corresponding compressor is determined based on the current operating frequency and the current oil temperature.
If the number of the compressors with the current oil temperature not higher than the oil temperature threshold is not less than two, the current oil demand of the compressors with the current oil temperature not higher than the corresponding oil temperature threshold is further determined, so that the control of the controllable valve is performed based on the current oil demand. For a specific determination of the current oil demand, reference is made to the corresponding description above.
Step 309: sequencing all the acquired current oil demands according to the order of magnitude; and determining the state of the controllable valve connected with each compressor with the current oil temperature not higher than the corresponding oil temperature threshold according to the sequencing.
The specific control procedure is referred to in the corresponding description of the preceding procedure.
In other preferred embodiments, when one compressor is in operation in the system, all controllable valves connected with the compressors in the stop state are controlled to be in a closed state, and the controllable valves connected with the one compressor in the operation state are regulated and controlled according to the actual oil temperature, and the specific control method is as follows:
acquiring the current oil temperature of one compressor in an operating state in real time, and comparing the current oil temperature with the corresponding oil temperature threshold of the one compressor;
when the current oil temperature of the one compressor is higher than the corresponding oil temperature threshold value of the one compressor, controlling a controllable valve connected with the one compressor to be in an open state so as to timely supplement lubricating oil for the one compressor; otherwise, the controllable valve connected with the compressor is controlled to be in a closed state so as to maintain the stable operation of the whole system.
Fig. 4 is a schematic structural diagram of an embodiment of a control device in a multi-compressor refrigerant cycle system according to the present invention, which is applied to the refrigerant cycle system shown in fig. 1 to implement oil return balance control of multiple compressors. The control device of this embodiment includes the structural units, the functions of the structural units, and the connection relationships therebetween, as described in detail below.
As shown in fig. 4, the control device includes:
a current oil temperature obtaining unit 41 for obtaining the current oil temperature of each compressor in an operating state in real time.
And the current oil temperature comparison unit 42 is configured to compare the current oil temperature with the corresponding oil temperature threshold of the compressor, and output a comparison result.
The current oil demand determining unit 43 is configured to obtain a current operating frequency of the compressor with a current oil temperature not higher than a corresponding oil temperature threshold, and determine a current oil demand of the corresponding compressor based on the current operating frequency and the current oil temperature.
And a control unit 44 configured to, when the number of compressors satisfying the current oil temperature not higher than the corresponding oil temperature threshold is not less than two, rank the obtained current oil demand amounts of all the compressors having the current oil temperature not higher than the corresponding oil temperature threshold in order of magnitude, and determine the state of the controllable valve to which each of the compressors having the current oil temperature not higher than the corresponding oil temperature threshold is connected according to the rank.
In other preferred embodiments, the control unit 44 is further configured to:
when the current oil temperature of the compressor in an operating state is higher than a corresponding oil temperature threshold value, controlling a controllable valve connected with the compressor to be in an open state; and
after a plurality of compressors are powered on and started to operate, firstly controlling controllable valves connected with all operating compressors to be in an open state, and continuing for a first time; then, controlling all controllable valves connected with all running compressors to be in a closed state; then the current oil temperature obtaining unit obtains the current oil temperature of each compressor in the running state in real time.
The control device with the structure is applied to a multi-compressor refrigerant circulation system with a plurality of controllable valves, runs corresponding software programs, executes corresponding functions, and performs multi-compressor oil return control according to the processes of the multi-compressor refrigerant circulation system control method embodiments and other preferred embodiments of fig. 2 and 3, so as to achieve the corresponding technical effects of the method embodiments.
Fig. 5 shows a block diagram of an embodiment of the electronic device of the invention. The electronic device includes a processor 51, a memory 52, and a computer program 521 stored on the memory 52, the processor 51 being configured to execute the computer program 521, implement the multi-compressor refrigerant cycle system control method of the embodiment of fig. 2, the embodiment of fig. 3, and other preferred embodiments, and achieve the technical effects of the corresponding embodiments. The electronic device may be a main control board, a controller, etc. of the refrigerant cycle system.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be apparent to one skilled in the art that modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some of the technical features thereof; such modifications and substitutions do not depart from the spirit and scope of the corresponding technical solutions.

Claims (9)

1. A method of controlling a multi-compressor refrigerant cycle system, the method comprising:
when a plurality of compressors in the system are in an operating state, acquiring the current oil temperature of each compressor in the operating state in real time, and comparing the current oil temperature of each compressor with an oil temperature threshold corresponding to the compressor;
when the number of compressors meeting the condition that the current oil temperature is not higher than the corresponding oil temperature threshold value is not less than two, executing the following oil return balance control process:
acquiring the current operating frequency of each compressor of which the current oil temperature is not higher than the corresponding oil temperature threshold value;
determining a current oil demand of the corresponding compressor based on the current operating frequency and the current oil temperature;
sequencing all the obtained current oil demand according to the order of magnitude;
determining the state of a controllable valve connected with each compressor of which the current oil temperature is not higher than the corresponding oil temperature threshold according to the sequencing;
the controllable valves are connected in parallel with oil return capillaries connected with the corresponding compressors and the oil separators corresponding to the compressors;
determining, according to the ranking, a state of a controllable valve connected to each compressor for which the current oil temperature is not higher than the corresponding oil temperature threshold, specifically including:
acquiring the current minimum oil demand and the current maximum oil demand in the sequencing;
when the ratio of the current maximum oil demand to the current minimum oil demand is larger than a first ratio coefficient, controlling the controllable valve connected with the current maximum oil demand compressor to be in an open state and controlling the controllable valve connected with the current minimum oil demand compressor to be in a closed state; the first scale factor is a positive number greater than 1;
and when the ratio of the current maximum oil demand to the current minimum oil demand is not greater than the first ratio coefficient, controlling a controllable valve connected with each compressor with the current oil temperature not higher than the corresponding oil temperature threshold to be in an open state.
2. The multi-compressor refrigerant cycle system control method of claim 1, further comprising:
when the ratio of the current maximum oil demand to the current minimum oil demand is greater than the first ratio, controlling the controllable valve connected with the current maximum oil demand compressor to be in an open state, and controlling the controllable valve connected with the current minimum oil demand compressor to be in a closed state, and then controlling the states of the controllable valves connected with the current other oil demand compressors in the sequence by adopting the following processes:
when the ratio of each current other oil demand to the current maximum oil demand is smaller than a second proportionality coefficient, controlling the controllable valve connected with the current other oil demand compressor to be in a closed state; otherwise, controlling the controllable valve connected with the compressor with the current other oil demands to be in an open state; the second scaling factor is a positive number less than 1.
3. The multi-compressor refrigerant cycle system control method according to claim 1, wherein determining the current oil demand of the respective compressors based on the current operating frequency and the current oil temperature, specifically comprises:
determining the current oil demand Q of the nth compressor by the following method n ：
Q n = Q nmax *[r n *f n /f nmax +(1-r n )*t n /t nmax ];
Wherein N is the number of compressors, n=1, 2, … …, N, N is the total number of compressors in the refrigerant circulation system, N is more than or equal to 2, Q nmax 、f nmax 、t nmax The maximum oil demand, the maximum operating frequency and the oil temperature threshold of the nth compressor are respectively set; r is (r) n Is a known regulating factor, is a positive number less than 1; f (f) n 、t n The current operating frequency and the current oil temperature are respectively.
4. A multi-compressor refrigerant cycle system control method according to any one of claims 1 to 3, further comprising:
and when the current oil temperature of the compressor in the running state is higher than the corresponding oil temperature threshold value, controlling the controllable valve connected with the compressor to be in an open state.
5. A multi-compressor refrigerant cycle system control method according to any one of claims 1 to 3, further comprising:
after a plurality of compressors are powered on and started to operate, firstly controlling all controllable valves connected with all operating compressors to be in an open state, and continuing for a first time; then, controlling all the controllable valves connected with all the running compressors to be in a closed state; and then executing the process of acquiring the current oil temperature in real time.
6. A multi-compressor refrigerant cycle system control method according to any one of claims 1 to 3, further comprising:
when one compressor is in the system in the running state, controlling the controllable valves connected with all compressors in the stopping state to be in the closing state, and controlling the states of the controllable valves connected with the one compressor in the running state according to the following processes:
acquiring the current oil temperature of the compressor in an operating state in real time, and comparing the current oil temperature with the corresponding oil temperature threshold of the compressor;
when the current oil temperature of the one compressor is higher than the oil temperature threshold corresponding to the one compressor, controlling the controllable valve connected with the one compressor to be in an open state; otherwise, the controllable valve connected with the compressor is controlled to be in a closed state.
7. A multi-compressor refrigerant cycle system comprising a plurality of compressors and an oil separator connected to each compressor by an oil return capillary tube, the system further comprising:
the number of the controllable valves is more than one, which is matched with the number of the compressors, and each controllable valve is connected with the oil return capillary corresponding to one compressor in parallel;
the system further includes a multi-compressor refrigerant cycle system control device, the device comprising:
the current oil temperature acquisition unit is used for acquiring the current oil temperature of each compressor in an operating state in real time;
the current oil temperature comparison unit is used for comparing the current oil temperature with the corresponding oil temperature threshold value of the compressor and outputting a comparison result;
a current oil demand determining unit, configured to obtain a current operating frequency of the compressor for which the current oil temperature is not higher than the corresponding oil temperature threshold value, and determine a current oil demand of the corresponding compressor based on the current operating frequency and the current oil temperature;
a control unit configured to rank, in order of magnitude, the obtained current oil amounts of all the compressors whose current oil temperatures are not higher than the respective oil temperature thresholds when the number of compressors satisfying the current oil temperatures is not higher than the respective oil temperature thresholds is not less than two, and determine, according to the rank, a state of a controllable valve to which each of the compressors whose current oil temperatures are not higher than the respective oil temperature thresholds is connected;
determining, according to the ranking, a state of a controllable valve connected to each compressor for which the current oil temperature is not higher than the corresponding oil temperature threshold, specifically including:
acquiring the current minimum oil demand and the current maximum oil demand in the sequencing;
when the ratio of the current maximum oil demand to the current minimum oil demand is larger than a first ratio coefficient, controlling the controllable valve connected with the current maximum oil demand compressor to be in an open state and controlling the controllable valve connected with the current minimum oil demand compressor to be in a closed state; the first scale factor is a positive number greater than 1;
and when the ratio of the current maximum oil demand to the current minimum oil demand is not greater than the first ratio coefficient, controlling a controllable valve connected with each compressor with the current oil temperature not higher than the corresponding oil temperature threshold to be in an open state.
8. The multi-compressor refrigerant cycle system of claim 7, wherein the control unit is further configured to:
when the current oil temperature of the compressor in an operating state is higher than the corresponding oil temperature threshold value, controlling the controllable valve connected with the compressor to be in an open state; and
after a plurality of compressors are powered on and started to operate, firstly controlling all controllable valves connected with all operating compressors to be in an open state, and continuing for a first time; then, controlling all the controllable valves connected with all the running compressors to be in a closed state; and then the current oil temperature acquisition unit acquires the current oil temperature of each compressor in the running state in real time.
9. An electronic device comprising a processor, a memory and a computer program stored on the memory, characterized in that the processor is configured to execute the computer program to implement the multi-compressor refrigerant cycle system control method of any one of the preceding claims 1 to 6.
CN202210022941.XA 2022-01-10 2022-01-10 Multi-compressor refrigerant circulation system and control method thereof Active CN114484715B (en)

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