CN112303972A - Control method and system of electronic expansion valve and refrigeration system - Google Patents

Control method and system of electronic expansion valve and refrigeration system Download PDF

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Publication number
CN112303972A
CN112303972A CN202011212669.9A CN202011212669A CN112303972A CN 112303972 A CN112303972 A CN 112303972A CN 202011212669 A CN202011212669 A CN 202011212669A CN 112303972 A CN112303972 A CN 112303972A
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evaporator
target
steaming
delta
superheat degree
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CN112303972B (en
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孙庆一鸣
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Gree Electric Appliances Inc of Zhuhai
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Gree Electric Appliances Inc of Zhuhai
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
    • F25B49/00—Arrangement or mounting of control or safety devices
    • F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
    • 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

Abstract

The invention discloses a control method and a control system of an electronic expansion valve and a refrigeration system, wherein the method comprises the following steps: real-time detection evaporator superheat degree delta TSteaming foodAccording to the degree of superheat Δ T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetCarrying out PID adjustment on the opening degree of the electronic expansion valve by using the difference value; when the degree of superheat delta T of the evaporatorSteaming foodThe superheat degree delta T of the protection with liquid is larger than the set superheat degree delta TProtection of liquid in steam zoneAnd setting the adjusting coefficient of the PID adjustment as follows: proportional coefficient Kp, integral time constant Ti and derivative time constant Td, otherwise, setting the PID adjusted adjustment coefficient to: proportional coefficient Kp and integral time constant T of liquidi liquid for preventing leucorrheaAnd a differential time constant Td, and Ti liquid for preventing leucorrhea<And (3) Ti. By adopting the technical scheme of the invention, the reliability of the refrigerating system can be improved.

Description

Control method and system of electronic expansion valve and refrigeration system
Technical Field
The invention relates to the field of refrigeration, in particular to a method and a system for controlling an electronic expansion valve and a refrigeration system adopting the electronic expansion valve control system.
Background
At present, in the refrigeration showcase industry, a self-carrying showcase mostly uses a capillary tube or a thermal expansion valve for throttling, a split-type showcase mostly uses the thermal expansion valve for throttling, and a few customers require to use an electronic expansion valve.
The thermostatic expansion valve is filled with a fixed refrigerant, and the refrigerant is required to be consistent with the refrigerant in the refrigeration system, so that the thermostatic expansion valve can play a normal throttling function. Therefore, after the refrigerant type of the refrigeration system is determined, the refrigerant type of the thermostatic expansion valve is also determined. However, in convenience stores and supermarkets, most of the merchants can select the split display case, and the split display case has the advantages that the unit is arranged outside the room, so that the indoor noise and heat load are reduced, and meanwhile, the goods storage space in the case is enlarged.
In actual engineering, an engineer can independently select and match a split-type display cabinet and a compression condensing unit, and the type of a refrigerant after the unit is selected is determined, so that the type of the refrigerant of the thermostatic expansion valve of the split-type display cabinet is also determined, but if the engineer does not fully communicate with a manufacturer in the selecting and matching process, the type of the refrigerant of the thermostatic expansion valve is different from the type of the refrigerant of the unit, and a refrigerating system cannot normally operate. And if the refrigerant type is changed after the compression condensing unit is replaced, the thermostatic expansion valve also needs to be replaced. The refrigeration system composed of the traditional split display cabinet and the compression condensing unit controls the start and stop of the unit by the change of low pressure, and the unit is started after the low pressure rises to a certain value, but in practice, the low pressure recovery unit can be started by mistake due to heat leakage of a distribution pipe.
The traditional control method of the electronic expansion valve is to use a temperature sensor to detect the temperature of an evaporator outlet, a pressure sensor to detect the pressure of the evaporator outlet so as to detect the superheat degree of the evaporator, and to set a target superheat degree and a real-time superheat degree to carry out PID (proportion integration differentiation) adjustment. When the electronic expansion valve is used for PID adjustment, the electronic expansion valve is easy to operate with liquid when the load change is large. Because the superheat degree controlled by the thermal expansion valve is a fixed value, the unit can be frequently started and stopped under the low heat load state, the oil return of the compressor is difficult, and the reliability of the system is low.
Disclosure of Invention
The invention aims to solve the technical problem of low reliability of an electronic expansion valve control system in the prior art, and provides an electronic expansion valve control method and system and a refrigeration system adopting the electronic expansion valve control system.
In an embodiment of the present invention, a method for controlling an electronic expansion valve is provided, where the method is used to control an electronic expansion valve in a refrigeration system, where the refrigeration system further includes an evaporator, and the method includes:
real-time detection evaporator superheat degree delta TSteaming foodAccording to the degree of superheat Δ T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetCarrying out PID adjustment on the opening degree of the electronic expansion valve by using the difference value;
when the degree of superheat delta T of the evaporatorSteaming foodThe superheat degree delta T of the protection with liquid is larger than the set superheat degree delta TProtection of liquid in steam zoneAnd setting the adjusting coefficient of the PID adjustment as follows: proportional coefficient Kp, integral time constant Ti and derivative time constant Td, otherwise, setting the PID adjusted adjustment coefficient to: proportional coefficient Kp and integral time constant T of liquidi liquid for preventing leucorrheaAnd a differential time constant Td, and Ti liquid for preventing leucorrhea<Ti。
In an embodiment of the present invention, the method for controlling an electronic expansion valve further includes: detecting the refrigerating operation time t of a refrigerating systemrunAccording to the refrigerating operation t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAnd (6) carrying out adjustment.
In the embodiment of the invention, the refrigerating operation time t of the refrigerating system is determinedrunTarget degree of superheat Δ T to evaporatorSteaming targetPerforming an adjustment comprising:
when running time trunNot less than the set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs greater than the minimum value Delta T of the target superheat degree of the evaporatorSteaming target MinThen, the target superheat degree delta T of the evaporator is setSteaming targetReducing the temperature by 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
In the embodiment of the invention, the refrigerating operation time t of the refrigerating system is determinedrunTarget degree of superheat Δ T to evaporatorSteaming targetAdjusting, further comprising:
when running time trunLess than set standard fortuneLine time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs less than the maximum value Delta T of the target superheat degree of the evaporatorMax of steaming objectThen, the target superheat degree delta T of the evaporator is setSteaming targetIncreasing 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
In an embodiment of the present invention, there is also provided an electronic expansion valve control system for controlling an electronic expansion valve in a refrigeration system, the refrigeration system further includes an evaporator, and the electronic expansion valve control system includes
The evaporator superheat degree detection module is used for detecting the superheat degree delta T of the evaporator in real timeSteaming food；
An opening control module of the electronic expansion valve for controlling the opening of the electronic expansion valve according to the superheat degree delta T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetCarrying out PID adjustment on the opening degree of the electronic expansion valve by using the difference value;
when the degree of superheat delta T of the evaporatorSteaming foodThe superheat degree delta T of the protection with liquid is larger than the set superheat degree delta TProtection of liquid in steam zoneAnd setting the adjusting coefficient of the PID adjustment as follows: proportional coefficient Kp, integral time constant Ti and derivative time constant Td, otherwise, setting the PID adjusted adjustment coefficient to: proportional coefficient Kp and integral time constant T of liquidi liquid for preventing leucorrheaAnd a differential time constant Td, and Ti liquid for preventing leucorrhea<Ti。
In an embodiment of the present invention, the electronic expansion valve control system further includes:
a refrigerating time detection module for detecting the refrigerating operation time t of the refrigerating systemrun；
An evaporator target superheat degree adjusting module for adjusting the superheat degree of the refrigerant according to the refrigerating operation time t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAnd (6) carrying out adjustment.
In the embodiment of the invention, the evaporator target superheat degree adjusting module is used for adjusting the superheat degree of the evaporator target superheat degree according to the refrigerating operation time t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAdjust, bagComprises the following steps:
when running time trunNot less than the set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment when the delta T isSteaming targetIs greater than the minimum value Delta T of the target superheat degree of the evaporatorSteaming target MinIn time, the target superheat degree delta T of the evaporator is adjustedSteaming targetReducing the temperature by 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetThe change is not changed;
in the embodiment of the invention, the evaporator target superheat degree adjusting module is used for adjusting the superheat degree of the evaporator target superheat degree according to the refrigerating operation time t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAdjusting, further comprising:
when running time trunLess than a set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment when the delta T isSteaming targetIs less than the maximum value Delta T of the target superheat degree of the evaporatorMax of steaming objectIn time, the target superheat degree delta T of the evaporator is adjustedSteaming targetIncreasing 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
In the embodiment of the invention, the evaporator superheat degree detection module comprises an evaporator inlet temperature sensing bulb and an evaporator outlet temperature sensing bulb which are respectively arranged at the inlet and the outlet of the evaporator, and the evaporator superheat degree delta TSteaming foodNamely the temperature difference detected by the evaporator outlet temperature sensing bulb and the evaporator inlet temperature sensing bulb.
In an embodiment of the present invention, there is also provided a refrigeration system, including: the system comprises a compression condensing unit, a filter, an electromagnetic valve, an electronic expansion valve, an evaporator and the electronic expansion valve control system which are connected in sequence.
Compared with the prior art, in the control method of the electronic expansion valve and the control method thereof, the superheat degree Delta T of the evaporator is usedSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetThe difference value of the time constant Ti is used for carrying out PID adjustment on the opening degree of the electronic expansion valve, and when the trend of liquid-carrying operation is detected, the integral time constant Ti is changed into liquid-carrying-prevention and liquid-carrying-prevention integralTime constant Ti liquid for preventing leucorrheaThe integral term effect is enhanced, the opening degree of the valve is quickly adjusted, and the problem of liquid-carrying operation can be improved; in addition, the target superheat degree of the evaporator is adjusted according to the refrigerating time of the refrigerating system, and the target superheat degree of the evaporator is reduced when the refrigerating time is long, so that the utilization efficiency of the evaporator is increased, the target superheat degree of the evaporator is improved when the refrigerating time is short, the refrigerating time is prolonged, the risk of unsmooth oil return is reduced, and the reliability of the system is improved.
Drawings
Fig. 1 is a schematic configuration diagram of a refrigeration system according to an embodiment of the present invention.
Fig. 2 is a flowchart of an electronic expansion valve opening degree control method according to an embodiment of the present invention.
FIG. 3 is a schematic diagram of the evaporator target superheat adjustment of an embodiment of the invention.
Fig. 4 is a schematic diagram of the configuration of an electronic expansion valve control system of an embodiment of the present invention.
Detailed Description
The invention provides a method and a system for controlling an electronic expansion valve, which are used for controlling the electronic expansion valve in a refrigeration system. The refrigeration system can be used for refrigeration of a split-type showcase and other refrigeration equipment, and the split-type showcase is taken as an example for description below.
As shown in fig. 1, the refrigeration system includes a compression and condensation unit, a filter, a solenoid valve, an electronic expansion valve, and an evaporator, which are connected in sequence. The working process of the refrigeration system is as follows: high-pressure liquid refrigerant provided by the compression condensing unit enters the split type display cabinet, is filtered by the filter and then passes through the electromagnetic valve, flows through the electronic expansion valve and then is throttled to become low-temperature and low-pressure gas-liquid mixture, then enters the evaporator to be evaporated and heat exchanged, and the refrigerant absorbs heat and then becomes gaseous refrigerant to flow out of the split type display cabinet. Wherein, the opening degree of the electronic expansion valve is determined by the change of the superheat degree of the evaporator.
Specifically, as shown in fig. 2, in the embodiment of the present invention, the control method of the electronic expansion valve includes steps S1 to S4. The following description will be made separately.
Step S1: real-time detection evaporator superheat degree delta TSteaming food。
In the embodiment of the present invention, an evaporator inlet temperature sensing bulb and an evaporator outlet temperature sensing bulb are respectively disposed at an inlet and an outlet of an evaporator, and a superheat degree Δ T of the evaporator is obtainedSteaming foodNamely the temperature difference detected by the evaporator outlet temperature sensing bulb and the evaporator inlet temperature sensing bulb.
Step S2: judging the superheat degree Delta T of the evaporatorSteaming foodAnd the set superheat degree delta T of the protection with liquidProtection of liquid in steam zoneThe magnitude relationship of (1).
It should be noted that, in order to prevent the problem of liquid carrying operation caused by the fact that the refrigerating capacity of the electronic expansion valve is larger than the refrigerating capacity required by the system, in the embodiment of the present invention, a liquid carrying protection superheat degree Δ T is providedThe liquid of the steaming band is protected,therefore, whether the electronic expansion valve operates with liquid or not is judged.
Step S3: when the degree of superheat delta T of the evaporatorSteaming foodDelta T greater than the protection degree of superheat with liquidProtection of liquid in steam zoneAccording to the superheat degree Delta T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetDifference e ofkCarrying out PID adjustment on the opening degree delta U of the electronic expansion valve, and setting the PID adjustment coefficient as: a proportionality coefficient Kp, an integration time constant Ti and a differentiation time constant Td.
In the PID control, the change value Δ U of the opening degree of the electronic expansion valve is obtained by adding three parts, namely a proportional term, an integral term and a differential term, and the expressions of the three parts are as follows:
proportional term = Kp × (e)k-ek-1)；
Integral term = Kp × T/Ti × ek；
Derivative term = Kp × Td/T × (e)k-2ek-1+ek-2）；
Where T represents the sampling period, e is a discrete samplekShows the superheat degree Delta T of the evaporator at the kth sampling momentSteaming foodTarget superheat degree delta T of evaporatorSteaming targetThe difference of (a).
Step S4: when the evaporator is overheatedDegree delta TSteaming foodNot more than the set superheat degree delta T with liquid protectionProtection of liquid in steam zoneAccording to the superheat degree Delta T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetDifference e ofkCarrying out PID adjustment on the opening degree delta U of the electronic expansion valve, and setting the PID adjustment coefficient as: proportional coefficient Kp and integral time constant T of liquidi liquid for preventing leucorrheaAnd a differential time constant Td, and Ti liquid for preventing leucorrhea<Ti。
It should be noted that when the evaporator is overheated, degree Δ TSteaming food≤△TProtection of liquid in steam zoneAnd meanwhile, the electronic expansion valve adjusts the valve opening according to a liquid-carrying prevention protection PID control strategy, and the difference of the two formulas is different in the integral time constant of an integral term. When the actual refrigeration operation is carried out, the refrigerant passing through the outlet of the evaporator is in an overheated gas state, if the refrigerant is in a gas-liquid mixed state, the compressor is damaged when the compressor runs seriously with liquid, when the refrigerating capacity of the electronic expansion valve is greater than the refrigerating capacity required by a system, the problem of running with liquid can occur, the temperature detected by the temperature sensing bulb at the inlet of the evaporator and the temperature sensing bulb at the outlet of the evaporator tend to be consistent, the superheat degree of the evaporator is always 0, and therefore the difference value e iskThe proportional term is 0 and the differential term is 0, so that only the integral term participates in the calculation without participating in the calculation. Integral time constant T for preventing liquid from being carried and liquid from being carriedi liquid for preventing leucorrheaSpecific integral time constant TiAnd at the moment, the integral term has stronger action, so that the valve opening can be adjusted more quickly, and the operation with liquid is avoided.
In the embodiment of the present invention, as shown in fig. 3, in the control method of the electronic expansion valve, the refrigerating operation time t of the refrigerating system is detectedrunAccording to the refrigerating operation t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetThe adjustment is carried out in the following specific manner:
when running time trunNot less than the set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs greater than the minimum value Delta T of the target superheat degree of the evaporatorSteaming target MinThen, the target superheat degree delta T of the evaporator is setSteaming targetThe temperature is reduced by 1 ℃ to increase the utilization efficiency of the evaporator; otherwise, maintaining the target superheat degree delta T of the evaporator unchanged, wherein the utilization rate of the evaporator is the maximum;
when running time trunLess than a set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs less than the maximum value Delta T of the target superheat degree of the evaporatorMax of steaming objectThen, the target superheat degree delta T of the evaporator is setSteaming targetIncrease by 1 ℃ and target superheat degree delta T of evaporator at the momentSteaming targetThe non-maximum value indicates that the refrigerating operation time is too short, which indicates that the refrigerating capacity provided by the evaporator is too large and the risk of unsmooth oil return exists, so that the superheat degree of the evaporator is gradually increased to inhibit the refrigerating time from being too short; otherwise, the target superheat degree delta of the evaporator at the momentT steaming targetThe maximum value is the maximum value, and the refrigerating running time is too short, which indicates that the refrigerating capacity provided by the evaporator is too large, and the risk of poor oil return exists, so that the superheat degree of the evaporator is maintained at the maximum superheat degree at the moment.
In the above-described adjustment mode, the maximum evaporator target superheat value Δ TMax of steaming objectAnd target superheat minimum value delta T of evaporatorSteaming target MinIs the endpoint value of a reasonable range of evaporator target superheat that is preset empirically by the technician.
As shown in fig. 4, corresponding to the above-mentioned electronic expansion valve control method, in an embodiment of the present invention, an electronic expansion valve control system is further provided, which includes an evaporator superheat degree detection module, an electronic expansion valve opening degree control module, a refrigeration time detection module, and an evaporator target superheat degree adjustment module. The following description will be made separately.
The evaporator superheat degree detection module is used for detecting the superheat degree delta T of the evaporator in real timeSteaming food。
In this embodiment, the evaporator superheat detection module includes an evaporator inlet thermal bulb and an evaporator outlet thermal bulb respectively disposed at the evaporator inlet and the evaporator outlet, and the evaporator passes throughHeat degree delta TSteaming foodNamely the temperature difference detected by the evaporator outlet temperature sensing bulb and the evaporator inlet temperature sensing bulb.
The electronic expansion valve opening control module is used for controlling the opening of the electronic expansion valve according to the superheat degree delta T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetThe differential value of (2) performs PID adjustment on the opening degree of the electronic expansion valve, and the specific adjustment mode is as follows:
when the degree of superheat delta T of the evaporatorSteaming foodThe superheat degree delta T of the protection with liquid is larger than the set superheat degree delta TProtection of liquid in steam zoneDuring the process, PID adjustment is carried out on the opening degree of the electronic expansion valve by adopting a set proportional coefficient Kp, an integral time constant Ti and a differential time constant Td, otherwise, the integral time constant Ti in the PID adjustment is replaced by a set liquid-carrying-prevention time integral constant Ti liquid for preventing leucorrheaAnd T isi liquid for preventing leucorrhea<Ti。
The refrigeration time detection module is used for detecting the refrigeration running time t of the refrigeration systemrun。
The evaporator target superheat degree adjusting module is used for adjusting the superheat degree of the evaporator target superheat degree according to the refrigerating operation time t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetThe adjustment is carried out in the following specific manner:
when running time trunNot less than the set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs greater than the minimum value Delta T of the target superheat degree of the evaporatorSteaming target MinThen, the target superheat degree delta T of the evaporator is setSteaming targetReducing the temperature by 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetThe change is not changed;
when running time trunLess than a set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs less than the maximum value Delta T of the target superheat degree of the evaporatorMax of steaming objectThen, the target superheat degree delta T of the evaporator is setSteaming targetIncreasing 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
In summary, in the method for controlling an electronic expansion valve and the method for controlling the same according to the present invention, the degree of superheat Δ T of the evaporator is usedSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetThe difference value of the time constant Ti is used for carrying out PID adjustment on the opening degree of the electronic expansion valve, and when the trend of liquid-carrying operation is detected, the integral time constant Ti is changed into a liquid-carrying-prevention and liquid-carrying-prevention integral time constant Ti liquid for preventing leucorrheaThe integral term effect is enhanced, the opening degree of the valve is quickly adjusted, and the problem of liquid-carrying operation can be improved; in addition, the target superheat degree of the evaporator is adjusted according to the refrigerating time of the refrigerating system, and the target superheat degree of the evaporator is reduced when the refrigerating time is long, so that the utilization efficiency of the evaporator is increased, the target superheat degree of the evaporator is improved when the refrigerating time is short, the refrigerating time is prolonged, the risk of unsmooth oil return is reduced, and the reliability of the system is improved.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims (10)

1. An electronic expansion valve control method for controlling an electronic expansion valve in a refrigeration system, the refrigeration system further comprising an evaporator, the method comprising:
real-time detection evaporator superheat degree delta TSteaming foodAccording to the degree of superheat Δ T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetCarrying out PID adjustment on the opening degree of the electronic expansion valve by using the difference value;
when the degree of superheat delta T of the evaporatorSteaming foodThe superheat degree delta T of the protection with liquid is larger than the set superheat degree delta TProtection of liquid in steam zoneAnd setting the adjusting coefficient of the PID adjustment as follows: proportional coefficient Kp, integral time constant Ti and derivative time constant Td, otherwise, setting the PID adjusted adjustment coefficient to: proportional coefficient Kp and integral time constant T of liquidi liquid for preventing leucorrheaAnd a differential time constant Td, and Ti liquid for preventing leucorrhea<Ti。
2. The electronic expansion valve control method of claim 1, further comprising: detecting the refrigerating operation time t of a refrigerating systemrunAccording to the refrigerating operation t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAnd (6) carrying out adjustment.
3. The electronic expansion valve control method of claim 2, wherein the operating time t is based on a refrigeration time of the refrigeration systemrunTarget degree of superheat Δ T to evaporatorSteaming targetPerforming an adjustment comprising:
when running time trunNot less than the set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs greater than the minimum value Delta T of the target superheat degree of the evaporatorSteaming target MinThen, the target superheat degree delta T of the evaporator is setSteaming targetReducing the temperature by 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
4. The electronic expansion valve control method of claim 3, wherein the operating time t is based on a refrigeration time of the refrigeration systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAdjusting, further comprising:
when running time trunLess than a set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs less than the maximum value Delta T of the target superheat degree of the evaporatorMax of steaming objectThen, the target superheat degree delta T of the evaporator is setSteaming targetIncreasing 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
5. An electronic expansion valve control system for controlling an electronic expansion valve in a refrigeration system, the refrigeration system further including an evaporator, the electronic expansion valve control system comprising:
the evaporator superheat degree detection module is used for detecting the superheat degree delta T of the evaporator in real timeSteaming food；
An opening control module of the electronic expansion valve for controlling the opening of the electronic expansion valve according to the superheat degree delta T of the evaporatorSteaming foodWith the set target superheat degree delta T of the evaporatorSteaming targetCarrying out PID adjustment on the opening degree of the electronic expansion valve by using the difference value;
when the degree of superheat delta T of the evaporatorSteaming foodThe superheat degree delta T of the protection with liquid is larger than the set superheat degree delta TProtection of liquid in steam zoneAnd setting the adjusting coefficient of the PID adjustment as follows: proportional coefficient Kp, integral time constant Ti and derivative time constant Td, otherwise, setting the PID adjusted adjustment coefficient to: proportional coefficient Kp and integral time constant T of liquidi liquid for preventing leucorrheaAnd a differential time constant Td, and Ti liquid for preventing leucorrhea<Ti。
6. The electronic expansion valve control system of claim 5, further comprising:
a refrigerating time detection module for detecting the refrigerating operation time t of the refrigerating systemrun；
An evaporator target superheat degree adjusting module for adjusting the superheat degree of the refrigerant according to the refrigerating operation time t of the refrigerating systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAnd (6) carrying out adjustment.
7. The electronic expansion valve control system of claim 6, wherein the evaporator target superheat adjustment module is based on a refrigeration run time t of the refrigeration systemrunTarget degree of superheat Δ T to evaporatorSteaming targetPerforming an adjustment comprising:
when running time trunNot less than the set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs greater than the minimum value Delta T of the target superheat degree of the evaporatorSteaming target MinThen, the target superheat degree delta T of the evaporator is setSteaming targetReducing the temperature by 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
8. The electronic expansion valve control system of claim 7, wherein the evaporator target superheat adjustment module is based on a refrigeration run time t of the refrigeration systemrunTarget degree of superheat Δ T to evaporatorSteaming targetAdjusting, further comprising:
when running time trunLess than a set standard running time trun standardThen, the target superheat degree delta T of the current evaporator is carried outSteaming targetMake a judgment if DeltaTSteaming targetIs less than the maximum value Delta T of the target superheat degree of the evaporatorMax of steaming objectThen, the target superheat degree delta T of the evaporator is setSteaming targetIncreasing 1 ℃, otherwise, maintaining the target superheat degree delta T of the evaporatorSteaming targetAnd is not changed.
9. The electronic expansion valve control system of claim 5, wherein said evaporator superheat detection module comprises an evaporator inlet bulb and an evaporator outlet bulb disposed at said evaporator inlet and outlet, respectively, and an evaporator superheat Δ TSteaming foodNamely the difference value of the temperature detected by the evaporator outlet temperature sensing bulb and the evaporator inlet temperature sensing bulb.
10. A refrigeration system, comprising: a compression condensing unit, a filter, a solenoid valve, an electronic expansion valve, an evaporator and an electronic expansion valve control system according to any one of claims 5 to 9 which are connected in sequence.
CN202011212669.9A 2020-11-03 2020-11-03 Control method and system of electronic expansion valve and refrigeration system Active CN112303972B (en)

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