CN115143657B - Control method and control device for variable frequency compressor system - Google Patents

Control method and control device for variable frequency compressor system Download PDF

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Publication number
CN115143657B
CN115143657B CN202210672557.4A CN202210672557A CN115143657B CN 115143657 B CN115143657 B CN 115143657B CN 202210672557 A CN202210672557 A CN 202210672557A CN 115143657 B CN115143657 B CN 115143657B
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China
Prior art keywords
variable frequency
compressor
flow
compressor system
lag
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CN115143657A (en
Inventor
赵龙生
王侃
何浩
唐文
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Trane Air Conditioning Systems China Co Ltd
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Trane Air Conditioning Systems China Co Ltd
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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
    • F25B1/00—Compression machines, plants or systems with non-reversible cycle
    • F25B1/10—Compression machines, plants or systems with non-reversible cycle with multi-stage compression
    • 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
    • F25B41/30—Expansion means; Dispositions thereof
    • F25B41/31—Expansion valves
    • F25B41/34—Expansion valves with the valve member being actuated by electric means, e.g. by piezoelectric actuators
    • 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
    • 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
    • F25B2500/00—Problems to be solved
    • F25B2500/24—Low amount of refrigerant in the system
    • 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
    • F25B2600/25—Control of valves
    • F25B2600/2513—Expansion valves

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • General Engineering & Computer Science (AREA)
  • Control Of Positive-Displacement Pumps (AREA)

Abstract

The embodiment of the invention provides a control method and a control device for a variable frequency compressor system. The variable frequency compressor system comprises a variable frequency compressor, an evaporator, an electronic expansion valve and a condenser, wherein the variable frequency compressor comprises a lead compressor and one or more lag compressors connected in parallel with the lead compressor. The control method comprises the following steps: in the running process of the variable frequency compressor system, calculating the mass flow of the compressor which is currently running; judging whether a lag compressor is started or not; when the lag compressor is started, the required mass flow of the lag compressor to be started is obtained based on the mass flow of the currently operated compressor; obtaining a feed-forward flow command for the variable frequency compressor system based on the mass flow of the currently operated compressor and the mass flow required by the lag compressor to be started; obtaining a feedback flow instruction of the variable frequency compressor system; and controlling the opening of the electronic expansion valve based on the feedforward flow command and the feedback flow command of the variable frequency compressor system.

Description

Control method and control device for variable frequency compressor system
Technical Field
The embodiment of the invention relates to the technical field of air conditioner control, in particular to a control method and a control device for a variable frequency compressor system.
Background
Fig. 1 discloses a simplified schematic diagram of an air conditioning system 1. As shown in fig. 1, the air conditioning system 1 generally includes four main functional components, respectively: a compressor 10, a condenser 15, a throttle device 14 and an evaporator 13. In the refrigerating process of the air conditioning system 1, the process of circulating the refrigerant in four components is as follows: the compressor 10 sucks in the low-temperature low-pressure gaseous refrigerant, and discharges the high-temperature high-pressure gaseous refrigerant after compression; after the refrigerant reaches the condenser 15, heat is released into the air to become a medium-temperature high-pressure liquid refrigerant; after the refrigerant reaches the throttling device 14, the refrigerant is throttled by depressurization to become a low-temperature low-pressure liquid refrigerant; the refrigerant reaches the evaporator 13, absorbs heat in the air, becomes a low-temperature low-pressure gaseous refrigerant, and finally returns to the compressor 10. The throttle device 14 is typically a TXV (Thermal Expansion Valve ) or an EXV (Electronic Expansion Valve, electronic expansion valve). The working principle of the thermostatic expansion valve is that a temperature sensing bag arranged at the outlet of the evaporator 13 is utilized to sense the superheat degree of the refrigerant vapor (the superheat degree refers to the value that the actual temperature of the vapor is higher than the evaporation temperature), so that the opening degree of the thermostatic expansion valve is adjusted, the flow rate of the liquid refrigerant entering the evaporator 13 is controlled, the control is simple, but the control precision is not high. The electronic expansion valve is controlled by the main controller, so that the control is more accurate and the effect is better, and the system requiring more accurate control generally adopts EXV.
Air conditioning refrigeration systems typically consist of multiple compressors in parallel, with the first compressor started being commonly referred to as the Lead (Lead) compressor and the later compressor started being referred to as the Lag (Lag) compressor. However, during a lag compressor start-up, for example by controlling the evaporator 13 level (condenser 15 level is opposite), the level is already low when the lag compressor starts. When a compressor is now reloaded, more refrigerant flow will actually be required, i.e. a higher liquid level. Because the response speed of the EXV control algorithm cannot be kept up, insufficient liquid supply of the evaporator 13 can be caused, the pressure of the evaporator 13 is too low due to lack of liquid, and the operation pressure ratio of the compressor is further too high.
Disclosure of Invention
An object of an embodiment of the present invention is to provide a control method for a variable frequency compressor system and a control device thereof, which can effectively solve the risk of shutdown caused by too low liquid level during the start-up of a lag compressor.
One aspect of an embodiment of the present invention provides a control method for a variable frequency compressor system. The variable frequency compressor system comprises a variable frequency compressor, an evaporator, an electronic expansion valve and a condenser which are connected through pipelines, wherein the variable frequency compressor comprises a leading compressor started before and one or more lagging compressors started after, and one or more lagging compressors are connected with the leading compressor in parallel. The control method comprises the following steps: calculating the mass flow of a compressor currently operated in the variable frequency compressor system in the operation process of the variable frequency compressor system; judging whether a lag compressor is started or not; when the lag compressor is started, obtaining the required mass flow of the lag compressor to be started based on the mass flow of the currently operated compressor; obtaining a feed-forward flow command for the variable frequency compressor system based on a mass flow of a currently operated compressor and a mass flow required by the lag compressor to be started; obtaining a feedback flow instruction of the variable frequency compressor system; and controlling an opening degree of the electronic expansion valve based on the feedforward flow rate command and the feedback flow rate command of the variable frequency compressor system.
Further, the obtaining a required mass flow rate of the lag compressor to be started based on the mass flow rate of the currently operated compressor includes: the mass flow of the compressor that is currently running and that is the same as the lag compressor to be started is taken as the mass flow required by the lag compressor to be started.
Further, the obtaining a feed forward flow command for the variable frequency compressor system based on the mass flow of the currently operated compressor and the mass flow required for the lag compressor to be started comprises: adding the mass flow of the currently operated compressor to the mass flow required by the started lag compressor to obtain a feed-forward flow of the variable frequency compressor system; and calculating a feedforward flow instruction of the variable frequency compressor system based on the feedforward flow of the variable frequency compressor system and the maximum flow of the electronic expansion valve.
Further, the obtaining the feedback flow command of the variable frequency compressor system includes: calculating a liquid level error of one of the evaporator and the condenser; adopting PI regulation to obtain feedback flow of the variable frequency compressor system based on the calculated liquid level error; and obtaining a feedback flow instruction of the variable frequency compressor system based on the feedback flow of the variable frequency compressor system.
Further, the calculating a liquid level error of one of the evaporator and the condenser includes: a liquid level error of one of the evaporator and the condenser is calculated based on a liquid level setpoint of the one of the evaporator and the condenser, a measured actual liquid level, and a product of a differential component and a liquid level change rate.
Further, the obtaining the feedback flow command of the variable frequency compressor system includes: calculating the accumulated feedback flow of the variable frequency compressor system; determining a settable scaling factor; multiplying the accumulated feedback flow of the variable frequency compressor system by the proportionality coefficient to serve as the current feedback flow of the variable frequency compressor system; and obtaining a feedback flow instruction of the variable frequency compressor system based on the current feedback flow of the variable frequency compressor system.
Further, the control method further includes: calculating a difference value of feedforward flow of the variable frequency compressor system; judging whether the difference value of the feedforward flow is larger than or smaller than a preset threshold value; and correspondingly processing the current feedback flow based on the judging result.
Further, the corresponding processing of the current feedback flow based on the judgment result includes: when the difference value of the feedforward flow is larger than or smaller than the preset threshold value, resetting the current feedback flow or reducing the current feedback flow according to steps; and when the difference value of the feedforward flow is not larger than and not smaller than the preset threshold value, keeping the current feedback flow unchanged.
Further, the control method further includes: calculating the mass flow of the lag compressor in the starting state in the actual running state; when the mass flow rate of the lag compressor in starting is greater than or equal to the mass flow rate of the same compressor which is already running, the lag compressor uses the mass flow rate in the actual running state of the lag compressor, and the variable frequency compressor system enters a stable state.
Another aspect of the embodiments of the present invention also provides a control apparatus for a variable frequency compressor system. The control device comprises one or more processors for implementing the control method for a variable frequency compressor system as described in the various embodiments above.
The control method and the control device for the variable frequency compressor system can solve the problem of response speed of the electronic expansion valve, and can control the liquid level at a reasonable position before the lag compressor is started, so that the risk of shutdown caused by too low liquid level during the start of the lag compressor is solved.
Drawings
FIG. 1 is a simplified schematic diagram of an air conditioning system;
FIG. 2 is a simplified schematic diagram of a variable frequency compressor system according to one embodiment of the present invention;
FIG. 3 is a flow chart of a control method for a variable frequency compressor system according to one embodiment of the present invention;
FIG. 4 is a block diagram illustrating the steps for processing a current feedback flow based on a difference in feed-forward flow of a variable frequency compressor system in accordance with one embodiment of the present invention;
FIG. 5 is a graph of a control method for a variable frequency compressor system that does not employ an embodiment of the present invention;
fig. 6 is a graph of a control method for a variable frequency compressor system employing an embodiment of the present invention.
Detailed Description
Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, the same numbers in different drawings refer to the same or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatus consistent with aspects of the invention as detailed in the accompanying claims.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless defined otherwise, technical or scientific terms used in the embodiments of the present invention should be given the ordinary meaning as understood by one of ordinary skill in the art to which the present invention belongs. The terms "first," "second," and the like in the description and in the claims, are not used for any order, quantity, or importance, but are used for distinguishing between different elements. Likewise, the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. "plurality" or "plurality" means two or more. Unless otherwise indicated, the terms "front," "rear," "lower," and/or "upper" and the like are merely for convenience of description and are not limited to one location or one spatial orientation. The word "comprising" or "comprises", and the like, means that elements or items appearing before "comprising" or "comprising" are encompassed by the element or item recited after "comprising" or "comprising" and equivalents thereof, and that other elements or items are not excluded. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. As used in this specification and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.
Fig. 2 discloses a simplified schematic diagram of a variable frequency compressor system 2 according to one embodiment of the present invention. As shown in fig. 2, the inverter compressor system 2 of one embodiment of the present invention may include an inverter compressor 20, an evaporator 23, an electronic expansion valve (EXV) 24, and a condenser 25 connected by piping. The variable frequency compressor 20 may include a Lead (Lead) compressor 21 that is started before and one or more Lag (Lag) compressors 22 that are started after, wherein the one or more Lag compressors 22 are connected in parallel with the Lead compressor 21, respectively.
In the inverter compressor system 2 of the embodiment of the present invention, the opening degree of the electronic expansion valve 24 may be used for controlling the flow rate of the refrigerant, and the refrigerant is stored in the condenser 25 and the evaporator 23, so that the liquid levels of the evaporator 23 and the condenser 25 need to be controlled, and the liquid level to be controlled may be the liquid level of the evaporator 23 or the liquid level of the condenser 25. The purpose of the liquid level control is to control the liquid level as close as possible to the set liquid level, and to balance the suction flow rate of the compressor 20 and the feed flow rate of the evaporator 23. However, when there is a lag compressor 22 start-up access in the inverter compressor system 2, the inverter compressor system 2 will require more refrigerant flow, i.e., a higher liquid level for the evaporator 23. However, the electronic expansion valve 24 has a slow response speed, which results in insufficient supply of the liquid to the evaporator 23.
In view of this, the embodiment of the invention provides a control method for the inverter compressor system 2. The control method for the variable frequency compressor system 2 of the embodiment of the invention can solve the problem of the response speed of the electronic expansion valve 24, so that the liquid level can be controlled at a reasonable position before the lag compressor 22 is started, thereby solving the risk of shutdown caused by too low liquid level during the start of the lag compressor 22.
A control method for the inverter compressor system 2 according to an embodiment of the present invention will be described in detail with reference to fig. 3.
Fig. 3 discloses a flow chart of a control method for the inverter compressor system 2 according to an embodiment of the invention. As shown in fig. 3, a control method for the inverter compressor system 2 according to an embodiment of the present invention may include steps S1 to S6.
In step S1, during operation of the variable frequency compressor system 2, the mass flow of the compressor currently being operated in the variable frequency compressor system 2 is calculated.
The mass flow of the compressor depends on the operating conditions of the compressor. Thus, the mass flow rate of the currently operated compressor can be calculated from the operating state of the currently operated compressor.
In step S2, it is determined whether or not the lag compressor 22 is started. In the case where the determination result is yes, the process proceeds to step S3.
In step S3, when the lag compressor 22 is started, the required mass flow of the lag compressor 22 to be started can be obtained based on the mass flow of the currently operated compressor obtained in step S2.
In one embodiment, the mass flow rate of the compressor that is currently running and the same as the lag compressor 22 to be started may be used as the mass flow rate required by the lag compressor 22 to be started.
Of course, if there is no compressor in the variable frequency compressor system 2 that is the same as the lag compressor 22 to be started, a corresponding conversion can be made based on the power levels of the currently operated compressor and the lag compressor 22 to be started.
In step S4, a feed-forward flow command of the variable frequency compressor system 2 is obtained based on the mass flow of the currently operated compressor obtained in step S2 and the mass flow required for the lag compressor 22 to be started obtained in step S3.
In some embodiments, step S4 may further include step S41 and step S42.
In step S41, the mass flow of the currently operated compressor and the mass flow required for the lag compressor 22 to be started may be added to obtain the feed forward flow of the variable frequency compressor system 2.
In step S42, a feedforward flow rate command of the inverter compressor system 2 may be calculated based on the feedforward flow rate of the inverter compressor system 2 and the maximum flow rate of the electronic expansion valve 24 obtained in step S41.
In one embodiment, the feed forward flow command of the variable frequency compressor system 2 may be calculated according to the following formula:
feedforward flow instruction = 100 x maximum flow of feedforward flow/EXV
In step S5, a feedback flow command of the inverter compressor system 2 is obtained.
In some embodiments, step S5 may further include steps S51 to S53.
In step S51, a liquid level error of one of the evaporator 23 and the condenser 25 is calculated.
For example, in the embodiment of the present invention, the liquid level error of the evaporator 23 may be calculated by taking the liquid level control of the evaporator 23 as an example.
In step S52, PI adjustment may be employed to obtain a feedback flow rate of the inverter compressor system 2 based on the calculated liquid level error.
In the embodiment of the present invention, in consideration of stability of control, a standard PID (Proportional, integral, derivative, proportional integral derivative) control algorithm is not used, but PI adjustment is adopted to obtain the feedback flow rate of the inverter compressor system 2.
In some embodiments, the calculation of the feedback flow of the variable frequency compressor system 2 is shown, for example, in the following equation:
incremental feedback flow = (kp+ki) ×current liquid level error-kp×previous liquid level error
Where Kp is the proportional gain and Ki is the integral gain.
In the embodiment of the invention, the differential component is embodied on the calculated liquid level error.
In step S51, a liquid level error of one of the evaporator 23 and the condenser 25 may be calculated based on a liquid level set point of one of the evaporator 23 and the condenser 25 (e.g., the evaporator 23), the measured actual liquid level, and a product of the differential component and the liquid level change speed.
A specific calculation formula of the liquid level error of one of the evaporator 23 and the condenser 25 is shown below, for example:
level error = level setpoint-actual level-Kd x rate of change of level
Where Kd is the differential component.
In step S53, a feedback flow command of the inverter compressor system 2 may be obtained based on the feedback flow of the inverter compressor system 2.
The feedback flow command of the inverter compressor system 2 may be similarly obtained based on the feedback flow of the inverter compressor system 2, taking into account the aforementioned calculation formula for obtaining the feedforward flow command of the inverter compressor system 2 based on the feedforward flow of the inverter compressor system 2.
In step S6, the opening degree of the electronic expansion valve 24 may be controlled based on the feedforward flow rate command of the inverter compressor system 2 obtained in step S4 and the feedback flow rate command obtained in step S5.
In some embodiments, the EXV flow command for the variable frequency compressor system 2 may be calculated according to the following formula:
then, the opening of the electronic expansion valve 24 is obtained by converting the obtained EXV flow command, so that the opening of the electronic expansion valve 24 can be controlled, the liquid level can be controlled at a reasonable position, and the risk of shutdown caused by, for example, too low liquid level of the evaporator 23 during the start-up of the lag compressor 22 is avoided.
In addition, two situations may occur, considering that there is a large variation in the feed-forward flow of the inverter compressor system 2 when the lag compressor 22 is loaded into the inverter compressor system 2: firstly, when the feedback flow is larger and the feedforward flow is added, the opening of the electronic expansion valve 24 is too large, and the risk of liquid carrying exists; secondly, the feedback flow is smaller, the feedforward flow and the feedback flow are added together, the obtained flow value of the total electronic expansion valve 24 is still smaller, the opening of the electronic expansion valve 24 is smaller, the liquid level is not as fast as that of pulling up, and the overcurrent alarm of the compressor can be caused.
Thus, in some embodiments of the present invention, obtaining the feedback flow command for the variable frequency compressor system 2 in step S5 may further comprise: calculating the accumulated feedback flow of the variable frequency compressor system 2; determining a settable scaling factor; multiplying the accumulated feedback flow of the variable frequency compressor system 2 by a proportionality coefficient to serve as the current feedback flow of the variable frequency compressor system 2; and obtaining a feedback flow instruction of the variable frequency compressor system 2 based on the current feedback flow of the variable frequency compressor system 2.
Fig. 4 discloses the steps of corresponding processing of the current feedback flow based on the difference in the feed-forward flow of the inverter compressor system 2 in accordance with one embodiment of the present invention. As shown in fig. 4, the control method for the inverter compressor system 2 according to the embodiment of the present invention may further include steps S7 to S9.
In step S7, a difference in the feedforward flow rate of the inverter compressor system 2 is calculated.
The difference between the current feed forward flow of the variable frequency compressor system 2 and the previous feed forward flow may be calculated.
In step S8, it is determined whether the difference in the feedforward flow calculated in step S7 is greater than or less than a predetermined threshold.
In step S9, the current feedback flow may be processed accordingly based on the result of the determination in step S8. In the case where the result of the judgment is yes, the process proceeds to step S91. In the case where the result of the judgment is no, the process proceeds to step S92.
In step S91, in one embodiment, when the difference between the current feedback flows is greater than or less than a predetermined threshold, the current feedback flow may be cleared. In another embodiment, when the difference value of the current feedback flow is greater than or less than the predetermined threshold value, the current feedback flow may be decreased in steps, so that abrupt changes may be prevented.
In step S92, when the difference between the current feedback flows is not greater than or not less than the predetermined threshold, the current feedback flow is kept unchanged.
In the control method for the inverter compressor system 2 according to the embodiment of the present invention, the mass flow rate in the actual operation state of the lag compressor 22 in the start-up can be calculated in real time. When the mass flow rate of the lag compressor 22 in the start-up is greater than or equal to the mass flow rate of the same compressor that has been operated, then the lag compressor 22 will use the mass flow rate in its actual operating state and the variable frequency compressor system 2 will enter a steady state.
It should be noted that the foregoing describes specific embodiments of the present invention. Other embodiments are within the scope of the following claims. In some cases, the actions or steps recited in the claims can be performed in a different order than in the embodiments and still achieve desirable results. In addition, the processes depicted in the accompanying drawings do not necessarily require the particular order shown, or sequential order, to achieve desirable results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.
Fig. 5 discloses a graph of a control method for a variable frequency compressor system without employing an embodiment of the present invention. The solid arrows in fig. 5 show the position of the lag compressor start. As shown in fig. 5, in the case where the control method for the inverter compressor system according to the embodiment of the present invention is not adopted, since the EXV opening degree is not significantly changed when the lag compressor is started, the suction flow rate of the compressor is excessively increased, resulting in the shortage of the evaporator.
Fig. 6 discloses a graph of a control method for a variable frequency compressor system employing an embodiment of the present invention. As shown in fig. 6, after adopting the control method for the variable frequency compressor system according to the embodiment of the present invention, the mass flow rate required for the lag compressor to be started is obtained based on the mass flow rate of the currently operated compressor while the start lag compressor command is issued, and thus the feedforward flow rate command of the variable frequency compressor system is obtained, and the opening degree of EXV is controlled based on the feedforward flow rate command and the feedback flow rate command. And after the current feed-forward flow instruction meets the judging condition, the normal control is restored. It can be observed from fig. 6 that the liquid level fluctuates for a short period of time, but that the liquid level fluctuation amplitude is acceptable, i.e., neither too low nor too high for a long period of time. In the process, the system pressure ratio of the variable frequency compressor is effectively controlled, and the overcurrent phenomenon is not triggered. Thus, the effectiveness of the control method for a variable frequency compressor system of the embodiment of the present invention was verified.
The embodiment of the invention also provides a control device (not shown) for the variable frequency compressor system. The control device for the inverter compressor system may comprise one or more processors (not shown) for implementing the control method for the inverter compressor system as described in the above embodiments.
The control device for the variable frequency compressor system according to the embodiment of the invention has similar technical effects as those of the control method for the variable frequency compressor system described above, and therefore, the description thereof will not be repeated here.
The control method and the control device for the variable frequency compressor system provided by the embodiment of the invention are described in detail. Specific examples are applied herein to illustrate the control method and the control device for the inverter compressor system according to the embodiments of the present invention, and the description of the above embodiments is only for helping to understand the core idea of the present invention, and is not intended to limit the present invention. It should be noted that it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the spirit and principles of the invention, which should also fall within the scope of the appended claims.

Claims (7)

1. A control method for a variable frequency compressor system comprising a variable frequency compressor, an evaporator, an electronic expansion valve, and a condenser connected by piping, the variable frequency compressor comprising a lead compressor that is previously started and one or more lag compressors that are later started, one or more of the lag compressors being connected in parallel with the lead compressor, the control method comprising:
calculating the mass flow of a compressor currently operated in the variable frequency compressor system in the operation process of the variable frequency compressor system;
judging whether a lag compressor is started or not;
when the lag compressor is started, obtaining the required mass flow of the lag compressor to be started based on the mass flow of the currently operated compressor;
a feed-forward flow command for the variable frequency compressor system is obtained based on the mass flow of the currently operated compressor and the mass flow required for the lag compressor to be started, comprising: adding the mass flow of the currently operated compressor to the mass flow required by the started lag compressor to obtain a feed-forward flow of the variable frequency compressor system; and calculating a feedforward flow instruction of the variable frequency compressor system based on the feedforward flow of the variable frequency compressor system and the maximum flow of the electronic expansion valve;
obtaining a feedback flow command for the variable frequency compressor system, comprising: calculating a liquid level error for one of the evaporator and the condenser based on a liquid level setpoint for the one of the evaporator and the condenser, the measured actual liquid level, and a product of a differential component and a liquid level change rate; adopting PI regulation to obtain feedback flow of the variable frequency compressor system based on the calculated liquid level error; and obtaining a feedback flow instruction of the variable frequency compressor system based on the feedback flow of the variable frequency compressor system; and
controlling an opening degree of the electronic expansion valve based on the feedforward flow rate command and the feedback flow rate command of the variable frequency compressor system.
2. The control method according to claim 1, characterized in that: the obtaining a required mass flow rate of the lag compressor to be started based on the mass flow rate of the currently operated compressor includes:
the mass flow of the compressor that is currently running and that is the same as the lag compressor to be started is taken as the mass flow required by the lag compressor to be started.
3. The control method according to claim 1, characterized in that: the obtaining the feedback flow command of the variable frequency compressor system comprises the following steps:
calculating the accumulated feedback flow of the variable frequency compressor system;
determining a settable scaling factor;
multiplying the accumulated feedback flow of the variable frequency compressor system by the proportionality coefficient to serve as the current feedback flow of the variable frequency compressor system; and
And obtaining a feedback flow instruction of the variable frequency compressor system based on the current feedback flow of the variable frequency compressor system.
4. A control method according to claim 3, characterized in that: further comprises:
calculating a difference value of feedforward flow of the variable frequency compressor system;
judging whether the difference value of the feedforward flow is larger than or smaller than a preset threshold value; and
And carrying out corresponding processing on the current feedback flow based on the judging result.
5. The control method according to claim 4, characterized in that: the corresponding processing of the current feedback flow based on the judgment result comprises the following steps:
when the difference value of the feedforward flow is larger than or smaller than the preset threshold value, resetting the current feedback flow or reducing the current feedback flow according to steps; and
And when the difference value of the feedforward flow is not larger than and not smaller than the preset threshold value, the current feedback flow is kept unchanged.
6. The control method according to claim 1, characterized in that: further comprises:
calculating the mass flow of the lag compressor in the starting state in the actual running state;
when the mass flow rate of the lag compressor in starting is greater than or equal to the mass flow rate of the same compressor which is already running, the lag compressor uses the mass flow rate in the actual running state of the lag compressor, and the variable frequency compressor system enters a stable state.
7. A control device for a variable frequency compressor system, characterized by: comprising one or more processors for implementing the control method for a variable frequency compressor system according to any one of claims 1-6.
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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4262493A (en) * 1979-08-02 1981-04-21 Westinghouse Electric Corp. Heat pump
DE69204723D1 (en) * 1991-04-23 1995-10-19 Asahi Breweries Ltd Refrigeration device consisting of a plurality of refrigeration circuits.
CN103946646A (en) * 2011-11-18 2014-07-23 三洋电机株式会社 Refrigeration unit
CN112728798A (en) * 2021-02-05 2021-04-30 青岛海信日立空调系统有限公司 Centrifugal compressor system and machine head adding control method thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4262493A (en) * 1979-08-02 1981-04-21 Westinghouse Electric Corp. Heat pump
DE69204723D1 (en) * 1991-04-23 1995-10-19 Asahi Breweries Ltd Refrigeration device consisting of a plurality of refrigeration circuits.
CN103946646A (en) * 2011-11-18 2014-07-23 三洋电机株式会社 Refrigeration unit
CN112728798A (en) * 2021-02-05 2021-04-30 青岛海信日立空调系统有限公司 Centrifugal compressor system and machine head adding control method thereof

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