CN117469163A - Control method and control unit of variable-frequency screw compressor with adjustable pressure ratio - Google Patents
Control method and control unit of variable-frequency screw compressor with adjustable pressure ratio Download PDFInfo
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- CN117469163A CN117469163A CN202311400226.6A CN202311400226A CN117469163A CN 117469163 A CN117469163 A CN 117469163A CN 202311400226 A CN202311400226 A CN 202311400226A CN 117469163 A CN117469163 A CN 117469163A
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- 238000000034 method Methods 0.000 title claims abstract description 30
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 58
- 238000007906 compression Methods 0.000 claims abstract description 57
- 230000006835 compression Effects 0.000 claims abstract description 56
- 238000011217 control strategy Methods 0.000 claims abstract description 13
- 238000012545 processing Methods 0.000 claims abstract description 10
- 230000005611 electricity Effects 0.000 claims description 4
- 230000001276 controlling effect Effects 0.000 description 11
- 230000005494 condensation Effects 0.000 description 4
- 238000009833 condensation Methods 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 230000000630 rising effect Effects 0.000 description 4
- 230000008859 change Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000004378 air conditioning Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 210000003781 tooth socket Anatomy 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
- F04C28/10—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber
- F04C28/12—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber using sliding valves
- F04C28/125—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by changing the positions of the inlet or outlet openings with respect to the working chamber using sliding valves with sliding valves controlled by the use of fluid other than the working fluid
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
- F04C28/06—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids specially adapted for stopping, starting, idling or no-load operation
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
- F04C28/08—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by varying the rotational speed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
- F04C28/18—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by varying the volume of the working chamber
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
- F04C28/28—Safety arrangements; Monitoring
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/04—Heating; Cooling; Heat insulation
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/70—Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
Abstract
The invention discloses a control method and a control unit of a variable-frequency screw compressor with adjustable pressure ratio, wherein the method comprises the following steps: acquiring compression end pressure of the screw compressor and exhaust pressure of the screw compressor; performing pressure regulation control treatment according to the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor to obtain the operating frequency of the screw compressor; and the screw compressor performs water temperature adjustment control according to the operating frequency to obtain an optimal control strategy. The invention can improve the compression efficiency of the compressor and reduce the compression power consumption of the compressor by carrying out the pressure ratio control and capacity adjustment processing on the compressor. The control method and the control unit of the variable-frequency screw compressor with the adjustable pressure ratio can be widely applied to the technical field of compressor control.
Description
Technical Field
The invention relates to the technical field of compressor control, in particular to a control method and a control unit of a variable-frequency screw compressor with adjustable pressure ratio.
Background
The screw compressor is applied to the field of air conditioners, the actual compressor is subjected to actual load transformation in the use process of a water chilling unit, the capacity of the compressor is adjusted, the air conditioning load is changed due to external condition change, the traditional compressor with the two load changes is realized by adjusting slide valves in the compressor, when the external condition is unchanged, only the load of the compressor is changed, the slide valve of the compressor moves, the length of a screw rod participating in a compression part is reduced, and the external pressure of the compressor is unchanged, so that the compressor is in the process of under-compressing, namely the compression final pressure is smaller than the condensation pressure, gas cannot be discharged out of the compressor after entering an exhaust port, the gas exhausted by the next tooth socket is continuously compressed, the exhaust port is discharged until the pressure reaches the condensation pressure, the efficiency of the existing compressor control method is reduced, and the power consumption is increased.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a control method and a control unit for a variable frequency screw compressor with adjustable pressure ratio, which can improve the compression efficiency of the compressor and reduce the compression power consumption of the compressor by performing pressure ratio control and capacity adjustment processing on the compressor.
The first technical scheme adopted by the invention is as follows: a control method of a variable frequency screw compressor with adjustable pressure ratio comprises the following steps:
acquiring compression end pressure of the screw compressor and exhaust pressure of the screw compressor;
performing pressure regulation control treatment according to the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor to obtain the operating frequency of the screw compressor;
and the screw compressor performs water temperature adjustment control according to the operating frequency to obtain an optimal control strategy.
Further, the screw compressor includes compressor group, first solenoid valve, second solenoid valve and converter, wherein:
the compressor unit is used for performing compression control work according to a given operating frequency;
the first electromagnetic valve and the second electromagnetic valve are used for adjusting the output pressure of the compressor unit;
the frequency converter is used for adjusting the compression control work of the compressor unit.
Further, the first electromagnetic valve is a pressure-reducing ratio electromagnetic valve, and is installed in an oil supply loop of the screw compressor, and the second electromagnetic valve is a pressure-increasing ratio electromagnetic valve, and is installed in an oil discharge loop of the screw compressor.
Further, the step of obtaining the compression end pressure of the screw compressor and the discharge pressure of the screw compressor specifically includes:
initializing the operating frequency of the screw compressor and obtaining the initial operating frequency;
and the compressor unit operates according to the initial operating frequency until a preset time requirement is met, and compression end pressure of the screw compressor and exhaust pressure of the screw compressor are obtained.
Further, the step of performing pressure adjustment control processing according to the compression end pressure of the screw compressor and the discharge pressure of the screw compressor to obtain the operating frequency of the screw compressor specifically includes:
constructing a boost pressure threshold and a buck pressure threshold;
subtracting the exhaust pressure of the screw compressor from the boost pressure threshold and the buck pressure threshold respectively to obtain a boost starting threshold and a buck starting threshold;
judging the compression end pressure of the screw compressor with the boosting start threshold and the depressurization start threshold respectively to obtain a judging result;
and performing pressure regulation control processing on the screw compressor according to the judging result to obtain the operating frequency of the screw compressor.
Further, the step of determining the compression end pressure of the screw compressor with the boost start threshold and the buck start threshold, respectively, to obtain a determination result specifically includes:
if the compression end pressure of the screw compressor is smaller than or equal to the boosting start threshold value and the duration time is larger than a preset time threshold value, controlling the screw compressor to enter a boosting working stage;
if the compression end pressure of the screw compressor is larger than or equal to the depressurization starting threshold value and the duration time is larger than a preset time threshold value, controlling the screw compressor to enter a depressurization working stage;
if the compression end pressure of the screw compressor is smaller than the depressurization start threshold and larger than the pressurization start threshold, and the duration time is larger than a preset time threshold, controlling the screw compressor to enter a normal working stage;
integrating the step-up working stage of the screw compressor, the step-down working stage of the screw compressor and the normal working stage of the screw compressor to obtain a judging result.
Further, the controlling the screw compressor to enter a boost operating phase and the controlling the screw compressor to enter a buck operating phase include:
the second electromagnetic valve is electrified and the first electromagnetic valve is powered off, so that the screw compressor enters a boosting working stage;
the screw compressor enters a step-down working stage by conducting electricity on the first electromagnetic valve and conducting electricity off on the second electromagnetic valve.
Further, the step of performing water temperature adjustment control by the screw compressor according to the operating frequency to obtain an optimal control strategy specifically includes:
setting a water temperature requirement range threshold;
the screw compressor works according to the operating frequency, and the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor are collected;
outputting an optimal control strategy if the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor meet the water temperature requirement range threshold;
and if the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor do not meet the water temperature requirement range threshold, adjusting the capacity of the screw compressor until the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor meet the water temperature requirement range threshold, and outputting an optimal control strategy.
Further, the outlet water temperature of the screw compressor and the inlet water temperature of the screw compressor are collected through a thermistor.
The second technical scheme adopted by the invention is as follows: a control unit of a variable frequency screw compressor of adjustable pressure ratio comprising:
the starting module is used for acquiring compression end pressure of the screw compressor and exhaust pressure of the screw compressor;
the pressure ratio adjusting module is used for performing pressure adjustment control processing according to the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor to obtain the operating frequency of the screw compressor;
and the capacity adjusting module is used for adjusting and controlling the water temperature of the screw compressor according to the operating frequency to obtain an optimal control strategy.
The control method and the control unit have the beneficial effects that: according to the invention, the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor are obtained for pressure regulation treatment, the movement of a regulating slide valve is not needed, the compressor is prevented from being in the process of under-compressing, the operation frequency of the compressor is further obtained for compressor capacity regulation treatment after the control of the pressure ratio, the operation frequency of the compressor is fixedly maintained, the exhaust pressure of the compressor is slightly higher than the condensation pressure, the gas is exhausted from the exhaust port, and a space is reserved for exhausting gas from the next tooth slot, so that the gas transmission of the compressor is continuous and stable, the compression efficiency of the compressor is improved, and the compression power consumption of the compressor is reduced.
Drawings
FIG. 1 is a flow chart of the steps of a control method of a variable frequency screw compressor with adjustable pressure ratio according to an embodiment of the present invention;
FIG. 2 is a block diagram of a control unit of a variable frequency screw compressor with adjustable pressure ratio according to an embodiment of the present invention;
FIG. 3 is a schematic view of an apparatus of a screw compressor according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of the result of controlling the water temperature of a subject to be adjusted according to an embodiment of the present invention;
fig. 5 is a schematic flow chart of frequency calculation according to water temperature in an embodiment of the invention.
Reference numerals: a1, a first electromagnetic valve; a2, a second electromagnetic valve.
Detailed Description
The invention will now be described in further detail with reference to the drawings and to specific examples. The step numbers in the following embodiments are set for convenience of illustration only, and the order between the steps is not limited in any way, and the execution order of the steps in the embodiments may be adaptively adjusted according to the understanding of those skilled in the art.
Explanation of technical terms of the present invention:
screw compressor: a screw compressor is a gas compression apparatus that uses rotation of a screw to increase the pressure and volume of gas. Compared with the traditional large piston compressor, the screw compressor has the advantages of higher reliability and efficiency, lower noise and vibration, less maintenance, longer service life and the like.
Discharge pressure of the compressor: the discharge pressure refers to the maximum pressure of the gas in the compressor during compression of the gas, and generally refers to the pressure at the compressor discharge, which occurs during compression.
End pressure of compressor: the final pressure is the final pressure of the gas in the compressor after the compressor has completed a complete compression cycle, and is typically the pressure at the final pressure port of the compressor, which occurs after the compression process has ended.
When the screw compressor is in use in a water chilling unit, the optimal state of the compressor is that the internal pressure ratio is equal to the external pressure ratio, the volumetric efficiency and the full-section thermal efficiency of the compressor are the highest, and the state is also a design point of the compressor, and when the load of the unit where the screw compressor is positioned changes, the situation is divided into 2 situations;
the first condition is that the external environment condition is not changed, namely the condensing pressure and the evaporating pressure of the unit are not changed, the demand load of the unit is changed, the unit is detected according to the outlet water temperature, the capacity of the unit is required to be adjusted, when the condition is that the screw compressor detects that the exhaust pressure at the slide valve is compared with the pressure in the condenser, the slide valve is not moved, and the unit performs capacity control by adjusting the frequency of the frequency converter;
the second condition is that when the external environment condition changes, the condensing pressure of the unit is often reduced along with the reduction of the load of the unit, the external pressure ratio of the compressor is reduced, the screw compressor detects that the pressure at the slide valve is larger than the pressure of the condenser, the slide valve moves, the slide valve stops moving when the internal pressure is equivalent to the condensing pressure, the internal pressure ratio of the compressor is equivalent to the external pressure ratio, the capacity of the screw compressor is reduced, and if the capacity is still larger than the required capacity, the unit is subjected to frequency reduction unloading.
Referring to fig. 1, the present invention provides a control method of a variable frequency screw compressor with an adjustable pressure ratio, the method comprising the steps of:
s1, acquiring compression end pressure of a screw compressor and exhaust pressure of the screw compressor;
specifically, as shown in fig. 3, the screw compressor comprises a compressor unit, a first electromagnetic valve A1, a second electromagnetic valve A2 and a frequency converter, wherein the compressor unit is used for performing compression control work according to a given operating frequency, the first electromagnetic valve and the second electromagnetic valve are used for adjusting the output pressure of the compressor unit, and the frequency converter is used for adjusting the compression control work of the compressor unit;
the first electromagnetic valve is a pressure-reducing ratio electromagnetic valve and is arranged in an oil supply loop of the screw compressor, and the second electromagnetic valve is a pressure-increasing ratio electromagnetic valve and is arranged in an oil discharge loop of the screw compressor;
further initializing the operating frequency of the screw compressor, obtaining an initial operating frequency, and operating the compressor unit according to the initial operating frequency until a preset time requirement is met, so as to obtain the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor;
in this embodiment, when the compressor starts to start, the start-up and drop-ratio (oil supply) solenoid valves of the compressor, i.e., the first solenoid valve, are all turned ON, and after the start of the operation of the compressor, the state of the operation frequency > 0Hz continues for 60 seconds or more, and the compression end pressure P is detected in real time i And exhaust pressure P d 。
S2, performing pressure regulation control treatment according to the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor to obtain the operating frequency of the screw compressor;
specifically, a pressure increasing threshold value and a pressure decreasing threshold value are constructed, wherein in the invention, the pressure increasing threshold value is defined as 80kPa, and the pressure decreasing threshold value is defined as 20kPa;
subtracting the exhaust pressure of the screw compressor from a boost pressure threshold and a buck pressure threshold respectively to obtain a boost starting threshold and a buck starting threshold, judging the compression end pressure of the screw compressor with the boost starting threshold and the buck starting threshold respectively, and obtaining a judgment result;
further, if the compression end pressure of the screw compressor is smaller than or equal to the boost starting threshold value and the duration time is larger than a preset time threshold value, controlling the screw compressor to enter a boost working stage;
in the present embodiment, when P i ≤P d 80kPa for 30 seconds, entering a step-up ratio stage, and powering on a step-up ratio electromagnetic valve A2 and powering off a step-down ratio electromagnetic valve A1;
if the compression end pressure of the screw compressor is larger than or equal to the depressurization starting threshold value and the duration time is larger than a preset time threshold value, controlling the screw compressor to enter a depressurization working stage;
in the present embodiment, when P i ≥P d 20kPa for 30 seconds, entering a step-down ratio stage, and powering on a step-down ratio electromagnetic valve A1 and powering off a step-up ratio electromagnetic valve A2;
if the compression end pressure of the screw compressor is smaller than the depressurization start threshold and larger than the pressurization start threshold, and the duration time is larger than a preset time threshold, controlling the screw compressor to enter a normal working stage;
in the present embodiment, P d -80kPa<P i <P d -20kPa for 30 seconds, and entering a normal state in which the operating frequency of the screw compressor is controlled based on the PI control calculation result so as to achieve that the temperature of the water to be controlled is close to the set temperature, and the pressure adjustment control processing is performed on the screw compressor based on the determination result, thereby obtaining the operating frequency of the screw compressor.
And S3, performing water temperature adjustment control on the screw compressor according to the operating frequency to obtain an optimal control strategy.
Specifically, when the water temperature of the control object is within the range of + -0.2 ℃ of the set water temperature, the operation frequency of the compressor is fixedly maintained.
When the compressor is started, a starting frequency is first outputted. After 1 minute from the start of the frequency output, the frequency PI control is started.
The water temperature detected by the outlet water temperature detecting thermistor is compared with the set cold water temperature, and the capacity and stop control of the compressor are performed through the frequency of the frequency converter.
And (3) performing restarting control after the temperature controller is OFF according to the temperature change amplitude of the inlet water temperature detected by the inlet water temperature detecting thermistor. In addition, according to the external input signal of the load rising and the load falling, the control of forced load rising, load falling, capacity holding and the like can be performed.
Under the control, the internal pressure ratio of the compressor is matched with the external pressure ratio, and after the compression is finished, the exhaust pressure of the compressor is slightly higher than the condensation pressure, and the gas is discharged out of the exhaust port. And a space is reserved for the gas discharged from the next tooth slot, so that the gas transmission of the compressor is continuous and stable. The volumetric efficiency of the compressor and the full-section thermal efficiency are all optimal. And the load state of the unit where the compressor is located is matched by adjusting the frequency of the compressor. Therefore, the unit is operated in a proper load state, and the energy is saved and the efficiency is high.
Compressor downtime: the compressor start and the reduction ratio battery valve are set to be ON, the output indicates 0Hz frequency operation, a stop command is output to the frequency converter for 30 seconds, and the compressor start and the reduction ratio battery valve are set to be OFF after 10 seconds.
According to the experimental control method, the compressor motor is required to perform frequency conversion, the unit is a frequency conversion unit, a pressure sensor orifice is developed on the compressor at the section of the slide valve near the exhaust port, pressure detection is performed, and the pressure detection is required to be continuously compared with the pressure of the condenser of the unit in the control process, so that the control is performed.
Further, as shown in fig. 4, the water temperature detected by the outlet water temperature detection thermistor is compared with the set cold water temperature, and the capacity and stop control of the compressor are performed by the inverter frequency and the slide valve control for compressor capacity. And (3) performing restarting control after the temperature controller is OFF according to the temperature change range of the inlet water temperature detected by the inlet water temperature detection thermistor. In addition, according to the external input signal of load rising and load falling, the control of forced load rising, load falling and capacity holding can be performed, when starting the compressor, firstly, the starting frequency is outputted. After 1 minute from the start of the frequency output, the frequency PI control starts, as shown in fig. 5, where the expression of the frequency calculation is:
Hz n ＝Hz n-1 +ΔHz
ΔHz＝K p ×(Tw n -Tw n-1 )+K i ×(Tw n -Tw set )×Ts
in the above, hz n Representing the calculated indication frequency, hz, of the compressor inverter n-1 Representing the last calculated compressorFrequency conversion indicating frequency Tw n Indicating the current control target water temperature, tw n-1 Indicating the water temperature Tw as the control target at the time of the previous calculation set Represents the set water temperature, ts represents the sampling period, K p Representing the proportionality coefficient, K i Representing the integral coefficient.
Referring to fig. 2, a control unit of a variable frequency screw compressor with adjustable pressure ratio, comprising:
the starting module is used for acquiring compression end pressure of the screw compressor and exhaust pressure of the screw compressor;
the pressure ratio adjusting module is used for performing pressure adjustment control processing according to the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor to obtain the operating frequency of the screw compressor;
and the capacity adjusting module is used for adjusting and controlling the water temperature of the screw compressor according to the operating frequency to obtain an optimal control strategy.
The content in the method embodiment is applicable to the system embodiment, the functions specifically realized by the system embodiment are the same as those of the method embodiment, and the achieved beneficial effects are the same as those of the method embodiment.
While the preferred embodiment of the present invention has been described in detail, the invention is not limited to the embodiment, and various equivalent modifications and substitutions can be made by those skilled in the art without departing from the spirit of the invention, and these modifications and substitutions are intended to be included in the scope of the present invention as defined in the appended claims.
Claims (10)
1. The control method of the variable frequency screw compressor with the adjustable pressure ratio is characterized by comprising the following steps of:
acquiring compression end pressure of the screw compressor and exhaust pressure of the screw compressor;
performing pressure regulation control treatment according to the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor to obtain the operating frequency of the screw compressor;
and the screw compressor performs water temperature adjustment control according to the operating frequency to obtain an optimal control strategy.
2. The control method of a variable frequency screw compressor with adjustable pressure ratio according to claim 1, wherein the screw compressor comprises a compressor block, a first solenoid valve, a second solenoid valve, and a frequency converter, wherein:
the compressor unit is used for performing compression control work according to a given operating frequency;
the first electromagnetic valve and the second electromagnetic valve are used for adjusting the output pressure of the compressor unit;
the frequency converter is used for adjusting the compression control work of the compressor unit.
3. The control method of variable frequency screw compressor with adjustable pressure ratio according to claim 2, wherein the first electromagnetic valve is a pressure-reducing ratio electromagnetic valve, installed in an oil supply circuit of the screw compressor, and the second electromagnetic valve is a pressure-increasing ratio electromagnetic valve, installed in an oil discharge circuit of the screw compressor.
4. A control method of a variable frequency screw compressor with adjustable pressure ratio according to claim 3, wherein the step of obtaining the compression end pressure of the screw compressor and the discharge pressure of the screw compressor comprises the steps of:
initializing the operating frequency of the screw compressor and obtaining the initial operating frequency;
and the compressor unit operates according to the initial operating frequency until a preset time requirement is met, and compression end pressure of the screw compressor and exhaust pressure of the screw compressor are obtained.
5. The control method of variable frequency screw compressor with adjustable pressure ratio according to claim 4, wherein said step of performing pressure adjustment control processing according to compression end pressure of said screw compressor and discharge pressure of said screw compressor to obtain an operation frequency of the screw compressor comprises:
constructing a boost pressure threshold and a buck pressure threshold;
subtracting the exhaust pressure of the screw compressor from the boost pressure threshold and the buck pressure threshold respectively to obtain a boost starting threshold and a buck starting threshold;
judging the compression end pressure of the screw compressor with the boosting start threshold and the depressurization start threshold respectively to obtain a judging result;
and performing pressure regulation control processing on the screw compressor according to the judging result to obtain the operating frequency of the screw compressor.
6. The method for controlling a variable frequency screw compressor with adjustable pressure ratio according to claim 5, wherein the step of determining the compression end pressure of the screw compressor with the start-up threshold and the start-down threshold, respectively, to obtain a determination result comprises the steps of:
if the compression end pressure of the screw compressor is smaller than or equal to the boosting start threshold value and the duration time is larger than a preset time threshold value, controlling the screw compressor to enter a boosting working stage;
if the compression end pressure of the screw compressor is larger than or equal to the depressurization starting threshold value and the duration time is larger than a preset time threshold value, controlling the screw compressor to enter a depressurization working stage;
if the compression end pressure of the screw compressor is smaller than the depressurization start threshold and larger than the pressurization start threshold, and the duration time is larger than a preset time threshold, controlling the screw compressor to enter a normal working stage;
integrating the step-up working stage of the screw compressor, the step-down working stage of the screw compressor and the normal working stage of the screw compressor to obtain a judging result.
7. The method of controlling a variable frequency screw compressor with adjustable pressure ratio according to claim 6, wherein said controlling said screw compressor to enter a boost operation phase and said controlling said screw compressor to enter a buck operation phase comprises:
the second electromagnetic valve is electrified and the first electromagnetic valve is powered off, so that the screw compressor enters a boosting working stage;
the screw compressor enters a step-down working stage by conducting electricity on the first electromagnetic valve and conducting electricity off on the second electromagnetic valve.
8. The control method of variable frequency screw compressor with adjustable pressure ratio according to claim 7, wherein the screw compressor performs water temperature adjustment control according to the operation frequency to obtain an optimal control strategy, which specifically comprises the steps of:
setting a water temperature requirement range threshold;
the screw compressor works according to the operating frequency, and the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor are collected;
outputting an optimal control strategy if the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor meet the water temperature requirement range threshold;
and if the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor do not meet the water temperature requirement range threshold, adjusting the capacity of the screw compressor until the water outlet temperature of the screw compressor and the water inlet temperature of the screw compressor meet the water temperature requirement range threshold, and outputting an optimal control strategy.
9. The control method of variable frequency screw compressor with adjustable pressure ratio according to claim 8, wherein the outlet water temperature of the screw compressor and the inlet water temperature of the screw compressor are collected through a thermistor.
10. The control unit of the variable-frequency screw compressor with the adjustable pressure ratio is characterized by comprising the following modules:
the starting module is used for acquiring compression end pressure of the screw compressor and exhaust pressure of the screw compressor;
the pressure ratio adjusting module is used for performing pressure adjustment control processing according to the compression end pressure of the screw compressor and the exhaust pressure of the screw compressor to obtain the operating frequency of the screw compressor;
and the capacity adjusting module is used for adjusting and controlling the water temperature of the screw compressor according to the operating frequency to obtain an optimal control strategy.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311400226.6A CN117469163A (en) | 2023-10-25 | 2023-10-25 | Control method and control unit of variable-frequency screw compressor with adjustable pressure ratio |
Applications Claiming Priority (1)
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| CN110566461A (en) * | 2019-09-11 | 2019-12-13 | 珠海格力电器股份有限公司 | two-stage compressor, control method of two-stage compressor and air conditioning unit |
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| CN101354165A (en) * | 2008-08-13 | 2009-01-28 | 泰豪科技股份有限公司 | Adjustable energy-saving type constant temperature and humidity machine unit |
| CN102748299A (en) * | 2012-04-11 | 2012-10-24 | 无锡市制冷设备厂有限责任公司 | Air exhaust end base of screw compressor |
| CN102840882A (en) * | 2012-09-04 | 2012-12-26 | 中国海洋石油总公司 | State monitoring and fault diagnosis system of gas turbine generating unit and use method of state monitoring and fault diagnosis system |
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