CN114413548B - Variable-frequency centrifugal water chilling unit and control method and storage medium thereof - Google Patents
Variable-frequency centrifugal water chilling unit and control method and storage medium thereof Download PDFInfo
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- CN114413548B CN114413548B CN202111573164.XA CN202111573164A CN114413548B CN 114413548 B CN114413548 B CN 114413548B CN 202111573164 A CN202111573164 A CN 202111573164A CN 114413548 B CN114413548 B CN 114413548B
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- 238000006243 chemical reaction Methods 0.000 claims abstract description 10
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- 230000008859 change Effects 0.000 claims description 31
- 230000009471 action Effects 0.000 claims description 18
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- 238000001704 evaporation Methods 0.000 claims description 11
- 238000011946 reduction process Methods 0.000 claims description 8
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- 238000004590 computer program Methods 0.000 claims description 4
- 238000010977 unit operation Methods 0.000 abstract description 7
- 230000005494 condensation Effects 0.000 abstract description 3
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- 230000001133 acceleration Effects 0.000 description 2
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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
- F25D—REFRIGERATORS; COLD ROOMS; ICE-BOXES; COOLING OR FREEZING APPARATUS NOT OTHERWISE PROVIDED FOR
- F25D15/00—Devices not covered by group F25D11/00 or F25D13/00, e.g. non-self-contained movable devices
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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
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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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- 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]
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Abstract
The invention provides a frequency conversion centrifugal water chilling unit, a control method and a storage medium thereof, wherein the unit comprises a throttle valve and a hot gas bypass valve which are connected in parallel between a condensation condenser and an evaporator, an air inlet and an air outlet of a compressor are respectively connected with the evaporator and the condenser, a frequency converter is used for controlling the frequency of the compressor, pressure measuring devices for measuring absolute pressure are arranged on the condenser and the evaporator, a vibration measuring device is arranged on the compressor, and a control unit receives data of the pressure measuring devices, the hot gas bypass valve and the vibration measuring devices for calculation processing and controls the frequency converter and the hot gas bypass valve according to the calculation result. The unit, the control method and the storage medium thereof carry out partition control on the unit operation range, realize the self-judgment of surge of the unit, and self-correct the safe operation range, so that the anti-surge control of the unit is more accurately matched with the actual surge point of the unit, the unit operation range is widened, and the unit operation performance and reliability are improved.
Description
Technical Field
The invention relates to the technical field of control of variable-frequency centrifugal chiller units, in particular to a variable-frequency centrifugal chiller unit, a control method and a storage medium thereof.
Background
Surging is an inherent property of a centrifugal compressor, is closely related to the rotating speed and the flow of the compressor, when the high-low pressure difference of a system exceeds the limit lift of the compressor at the current rotating speed, airflow at an outlet of an impeller cannot be smoothly discharged, high-pressure gas in a condenser flows back to the compressor until the pressure in the condenser is reduced to be lower than the pressure at the outlet of the compressor, at the moment, the backflow is stopped, the airflow flows forward under the action of the impeller, and the periodic oscillation phenomena of the airflow, the current, the pressure and the like occur in the whole system in cycles, and the surging is called. Meanwhile, when the air suction flow of the impeller is too small and deviates from the designed working condition, the air flow direction deviates from the geometric angle of the impeller, and when the flow is reduced to a certain critical value, the separation and diffusion loss are increased sharply, the lift of the compressor is greatly reduced, and the surge phenomenon also occurs.
In order to prevent the compressor from surging, a common method for the frequency converter set at present is to arrange a surge preventing line. A surge line of the compressor is formed by using a pressure ratio (condensing pressure/evaporating pressure) as an abscissa and a surge frequency corresponding to each pressure ratio as an ordinate, and a partial frequency is added to the surge line as a safety margin, thereby forming a surge prevention line of the unit. In the unit operation process, the condensing pressure and the evaporating pressure of the unit are obtained through the pressure sensor, the current compressor operation pressure ratio is calculated, the pressure ratio is substituted into the anti-surge line formula, the minimum frequency of the unit operating under the pressure ratio is calculated, and the actual operation frequency of the unit cannot be smaller than the minimum frequency calculated by the anti-surge line, so that the unit is prevented from surging.
In practice, the load demand on the units varies, and therefore it is often desirable to have a wide operating range for the units. Along with the change of the load and the working condition of the unit, the running pressure ratio of the compressor also changes, and the current anti-surge control method has the following problems: 1. because the surge-proof line is fitted through a single formula, the surge-proof line and the surge line cannot be completely matched, and the precision is poor, so that the running range of the unit is narrowed; 2. the operation range of the unit is narrowed, when the unit needs small load operation, the operation can be realized only by closing guide vanes, opening a bypass and even starting and stopping the unit, and the energy efficiency of the unit is greatly reduced; 3. the suction volume of the compressor is reduced by closing the guide vane, the load of the unit is reduced, the change range of the opening of the guide vane is 0% -100%, the opening of the guide vane and the suction flow are not in a linear change relation, the suction flow is too small, the compressor is easy to surge, and the reliability of the unit cannot be guaranteed.
Disclosure of Invention
The invention aims to solve the technical problems that an anti-surge line and a surge line cannot be completely matched, the precision is poor, the operation range of a unit is narrowed, the energy efficiency of the unit is greatly reduced, a compressor is easy to surge, and the reliability of the unit cannot be guaranteed in the prior art, and provides a variable-frequency centrifugal water chilling unit, a control method and a storage medium thereof.
In order to solve the technical problems, the technical scheme provided by the invention is as follows:
the utility model provides a centrifugal cooling water set of frequency conversion, including the condenser, the evaporimeter, the compressor, converter and the control unit, wherein, be equipped with parallelly connected choke valve and hot gas bypass valve between condenser and the evaporimeter, the air inlet and the gas vent of compressor are connected with evaporimeter and condenser respectively, the converter is used for controlling the frequency (rotational speed) of compressor, all be equipped with the pressure measurement device who is used for measuring absolute pressure on condenser and the evaporimeter, be equipped with vibration measuring device on the compressor, the control unit receives the data of pressure measurement device, hot gas bypass valve and vibration measuring device and carries out calculation processing, and control converter and hot gas bypass valve according to the calculated result.
According to the variable-frequency centrifugal water chilling unit, the operation range of the unit is subjected to partition control by detecting the pressure of the evaporator and the condenser and the vibration of the compressor, so that the unit can automatically judge surge, the safe operation range is automatically corrected, the unit anti-surge control and the actual surge point of the unit are more accurately matched by controlling the operation frequency of the compressor of the unit and coordinately adjusting the hot gas bypass butterfly valve, and compared with the traditional anti-surge control method, the variable-frequency centrifugal water chilling unit not only widens the operation range of the unit, but also improves the operation performance and reliability of the unit.
For the above technical solution, further improvements can be made as described below.
According to the variable-frequency centrifugal water chilling unit, in a preferred embodiment, the vibration measuring device comprises a vibration sensor, and the vibration sensor is arranged on the surface of a shell of the compressor.
The vibration sensor is arranged on the surface of the compressor shell and used for detecting the vibration acceleration of the compressor in the operation of the unit, the arrangement and installation are easy, and the detection result is accurate and reliable.
In particular, in a preferred embodiment, the pressure measuring means comprise a pressure sensor.
The pressure sensors are adopted to measure the absolute pressure in the evaporator and the condenser, the arrangement and installation are easy, and the detection result is accurate and reliable.
Specifically, in a preferred embodiment, the hot gas bypass valve comprises a butterfly valve.
The butterfly valve is used as a bypass control valve, so that the opening adjustment of 0-100% can be realized, and the control process is stable and reliable.
The control method of the frequency conversion centrifugal water chilling unit in the second aspect of the invention is implemented by adopting the frequency conversion centrifugal water chilling unit, and comprises the following steps: s01, when the unit operates in a certain working condition, setting an anti-surge operation frequency line Y1 of the unit according to a relation curve Y0 of the operation frequency of a compressor of the unit and the load of the unit and a surge frequency line Y2 of the unit; and S02, when the actual load requirement of the unit under a certain working condition is in different load intervals realized by frequency adjustment of the unit under the working condition, the unit adjusts the operating frequency of the compressor to be maintained in different intervals, and in the process of reducing the frequency of the compressor, the opening of the hot gas bypass valve is adjusted according to the load change of the unit to meet the actual load requirement of the unit.
Specifically, in a preferred embodiment, step S02 specifically includes the following sub-steps: s021, when the actual load requirement of the unit under a certain working condition is between the minimum operation load Q2 realized by the unit through frequency adjustment under the working condition and the maximum load Q1 of the unit under the working condition, the unit adjusts the operation frequency of the compressor according to the operation frequency action period T1 and the adjustment frequency variable D1 to be between the minimum frequency H2 of the compressor in operation under the working condition and the rated frequency H1 of the compressor in operation under the working condition; s022, when the actual load demand of the unit under a certain working condition is smaller than the minimum operation load Q2 of the unit under the working condition, which is realized through frequency adjustment, when the frequency of the compressor is reduced to the minimum frequency H2 of the compressor under the working condition, the frequency of the compressor is kept unchanged, and a hot gas bypass valve is opened to reduce the load of the unit to the actual demand; s023, after the load of the unit under the certain working condition is reduced, the minimum frequency H2 of the compressor running under the working condition is reduced to H4, after the load of the unit is continuously stabilized for T0 time, the unit continues to reduce the frequency of the compressor to H4 according to the running frequency action period T1 and the frequency adjusting variable D1, and in the process of reducing the frequency of the compressor, the opening of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load requirement of the unit.
According to the control method of the variable-frequency centrifugal water chilling unit, the frequency difference is set between the anti-surge operation frequency line Y1 of the unit and the surge frequency line Y2 of the unit to serve as the anti-surge safety margin, so that the unit is ensured to possibly surge when the unit operates under variable working conditions, the reserved safety margin can ensure that the unit cannot surge in the process of variable working conditions because the pressure is changed firstly and the unit needs a certain time for adjustment according to the pressure change, and meanwhile, the unit load is reduced by controlling the operation frequency of a compressor of the unit, and opening of a hot gas bypass valve and a fine regulator, so that the unit surge is met and avoided, the anti-surge control of the unit is more accurately matched with the actual surge point of the unit.
Further, in a preferred embodiment, the method for controlling a variable frequency centrifugal chiller according to the second aspect of the present invention further includes the steps of: s03, when the opening of the hot gas bypass valve is larger than 0%, the frequency of the compressor is continuously reduced by the unit according to the operation frequency action period T2 and the frequency adjusting variable D2, and in the frequency reduction process of the compressor, the opening of the hot gas bypass valve is reduced according to load change of the unit to meet actual load requirements of the unit.
Furthermore, the load of the unit is reduced through the hot gas bypass valve, the surge of the unit is avoided, but the bypass is not energy-saving when the bypass is opened, and the control is performed in reverse to reduce the bypass and reduce the frequency of the compressor, so that the performance of the unit is improved, and the load requirement can be ensured.
Specifically, in a preferred embodiment, step S03 specifically includes the following sub-steps: s031, calculating the operation pressure ratio of the compressor as the ratio of the condensation pressure to the evaporation pressure according to the condensation pressure and the evaporation pressure obtained by the pressure measuring device, wherein A1 is the minimum operation pressure ratio of the compressor, A2 is the maximum operation pressure ratio of the compressor, and dividing the operation pressure ratio range A1-A2 of the compressor into n pressure ratio intervals B1, B2, B3, 8230and Bn; s032, calculating the vibration change rate to be the ratio of the current vibration value to the average vibration value according to the vibration value of the compressor, setting surge judgment vibration change rate Z0, and judging that the unit has surge when the vibration change rate is not less than Z0; s033, calculating the current operation pressure ratio of the compressor according to the condensing pressure and the evaporating pressure obtained by the pressure measuring device; s034, when the unit is judged to have surge in the step S032, recording the current running pressure ratio and the compressor surge frequency of the compressor during the surge, and adding an anti-surge frequency increment H0 to the compressor surge frequency to serve as the minimum frequency of the compressor running in the current running pressure ratio interval; s035, when the unit is judged to have surge in the step S032, the running frequency of the compressor is increased to the anti-surge running frequency value corresponding to the current running pressure ratio of the compressor, and meanwhile, the hot gas bypass valve is controlled to increase the opening according to the load change of the unit; s036, after the load of the unit is continuously stabilized for T0 time, the compressor performs frequency reduction operation, the unit continues to reduce the frequency of the compressor according to the operation frequency action period T2 and the frequency adjustment variable D2, and in the frequency reduction process of the compressor, the opening degree of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load requirement of the unit until the opening degree of the hot gas bypass butterfly valve is 0%.
By means of the control, the compressor operation and the surge line are more consistent, the unit operation range is widened, the unit operation performance is improved, meanwhile, the unit can automatically judge surge and automatically set the minimum operation frequency for each compressor pressure ratio interval, the unit is prevented from generating surge again, the anti-surge control precision is improved, and the unit reliability is improved.
Further, in a preferred embodiment, the step S03 further includes a step S037, after the load of the unit is continuously stable for T0 time, the compressor performs a frequency reduction operation, the unit continues to reduce the frequency of the compressor according to the operation frequency action period T2 and the frequency adjustment variable D2, and during the frequency reduction process of the compressor, the opening of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load demand of the unit until the operation frequency of the compressor is reduced to the minimum frequency at which the compressor in the current operation pressure ratio interval can operate.
Through the control, the follow-up surge can be avoided again, the anti-surge control precision is improved, and the reliability of the unit is improved.
Further, in a preferred embodiment, the operation frequency operation period T2 is not less than the operation frequency operation period T1, and the frequency adjustment variable D2 is not greater than the frequency adjustment variable D1.
Because surging is easy to occur during the operation of the unit in the step S03, the surging frequency of the unit under the corresponding pressure ratio is measured simultaneously in the control process, and the setting mode can ensure that the unit has small adjustment amount and long period, so that the unit operates more stably, and data in the measurement process is more accurate and reliable.
Specifically, in a preferred embodiment, T0, T1, T2, D1 and D2 are all variable settings, with the unit of T0 being min, the unit of T1 and T2 being s, and the unit of D1 and D2 being Hz. For example, T1 is 10s, D1 is 3Hz, T2 is 20s, D2 is 1Hz, the stable operation of the unit is ensured according to actual use, the unit values of different refrigerating capacities are different, and fixed setting is not carried out.
The load continuous stable time T0 of the unit, the operation frequency action periods T1 and T2 of the unit and the frequency adjusting variables D1 and D2 are set according to the method, so that the stable and reliable frequency reduction adjusting process of the compressor can be ensured to a great extent.
A storage medium according to a third aspect of the present invention stores a computer program that, when executed by a processor, executes the control method described above.
Compared with the prior art, the invention has the advantages that: the method has the advantages that the operation range of the unit is controlled in a partitioning mode by detecting the pressure of the evaporator and the condenser of the unit and the vibration frequency of the compressor, the self-judgment of surge of the unit is realized, the safe operation range is self-corrected, the operation frequency of the compressor of the unit and the coordination and adjustment of the hot gas bypass butterfly valve are controlled, the anti-surge control of the unit is more accurate to the actual surge point of the unit, the operation range of the unit is widened compared with the traditional anti-surge control method, and the operation performance and the reliability of the unit are improved.
Drawings
The invention will be described in more detail hereinafter on the basis of embodiments and with reference to the drawings. Wherein:
FIG. 1 schematically illustrates an overall frame structure of a variable frequency centrifugal chiller according to an embodiment of the present invention;
FIG. 2 schematically illustrates one of the principles of a control method of an embodiment of the invention;
fig. 3 schematically shows another principle of the control method of the embodiment of the present invention.
In the drawings, like parts are given like reference numerals. The figures are not drawn to scale.
Detailed Description
The invention will be described in further detail with reference to the following figures and specific examples, without thereby limiting the scope of protection of the invention.
Fig. 1 schematically shows an overall frame structure of a variable frequency centrifugal chiller 10 according to an embodiment of the present invention. Fig. 2 schematically shows one of the principles of the control method of the embodiment of the present invention. Fig. 3 schematically shows another principle of the control method of the embodiment of the present invention.
Example 1
As shown in fig. 1, a variable frequency centrifugal chiller 10 according to an embodiment of the present invention includes a condenser 1, an evaporator 2, a compressor 3, a frequency converter 4 and a control unit 5, wherein a throttle valve 6 and a hot gas bypass valve 7 are disposed between the condenser 1 and the evaporator 2 in parallel, an air inlet and an air outlet of the compressor 3 are respectively connected to the evaporator 2 and the condenser 1, the frequency converter 4 is configured to control a frequency (a rotation speed) of the compressor 3, pressure measuring devices P2 and P1 are respectively disposed on the condenser 1 and the evaporator 2 for measuring absolute pressure, a vibration measuring device Z is disposed on the compressor 3, and the control unit 5 receives data of the pressure measuring devices P2 and P1, the hot gas bypass valve 7 and the vibration measuring device Z for calculation processing, and controls the frequency converter 4 and the hot gas bypass valve 7 according to a calculation result.
According to the frequency conversion centrifugal water chilling unit provided by the embodiment of the invention, the operation range of the unit is subjected to zone control by detecting the pressure of the evaporator and the condenser and the vibration of the compressor, so that the unit can automatically judge surge, the safe operation range is automatically corrected, the unit anti-surge control and the actual surge point of the unit are more accurately matched by controlling the operation frequency of the compressor of the unit and coordinately adjusting the hot gas bypass butterfly valve, and compared with the traditional anti-surge control method, the frequency conversion centrifugal water chilling unit not only widens the operation range of the unit, but also improves the operation performance and reliability of the unit.
Specifically, in the present embodiment, the vibration measuring device Z includes a vibration sensor disposed on the casing surface of the compressor 3. The vibration sensor is arranged on the surface of the compressor shell and used for detecting the vibration acceleration of the compressor in the operation of the unit, the arrangement and installation are easy, and the detection result is accurate and reliable. Specifically, in the present embodiment, the pressure measurement devices P2, P1 include pressure sensors. The pressure sensors are adopted to measure the absolute pressure in the evaporator and the condenser, the arrangement and installation are easy, and the detection result is accurate and reliable. Specifically, in the present embodiment, the hot gas bypass valve 7 includes a butterfly valve. The butterfly valve is used as a bypass control valve, so that the opening adjustment of 0-100% can be realized, and the control process is stable and reliable.
Example 2
As shown in fig. 2, the control method of the variable frequency centrifugal chiller according to the embodiment of the present invention is implemented by using the variable frequency centrifugal chiller 10, and includes the following steps: s01, when the unit operates in a certain working condition, setting an anti-surge operation frequency line Y1 of the unit according to a relation curve Y0 of the operation frequency of a compressor of the unit and the load of the unit and a surge frequency line Y2 of the unit; when the unit operates at a frequency less than Y2, the unit will have surge, and the frequency difference between Y1 and Y2 is an anti-surge safety margin; h1 is the rated frequency of the compressor, H2 is the minimum frequency of the unit under the working condition, and H3 is the surge frequency of the unit under the working condition; q1 is the maximum load of the unit under the working condition, Q2 is the minimum running load of the unit realized by frequency adjustment under the working condition, and Q3 is the surge point load of the unit under the working condition; and S02, when the actual load requirement of the unit under a certain working condition is in different load intervals realized by frequency adjustment of the unit under the working condition, the unit adjusts the operating frequency of the compressor to be maintained in different intervals, and in the process of reducing the frequency of the compressor, the opening of the hot gas bypass valve is adjusted according to the load change of the unit to meet the actual load requirement of the unit.
As shown in fig. 2, in particular, in the present embodiment, the step S02 includes the following sub-steps: s021, when the actual load requirement of the unit under a certain working condition is between the minimum operation load Q2 realized by the unit through frequency adjustment under the working condition and the maximum load Q1 of the unit under the working condition, the unit adjusts the operation frequency of the compressor according to the operation frequency action period T1 and the adjustment frequency variable D1 to be between the minimum frequency H2 of the compressor in operation under the working condition and the rated frequency H1 of the compressor in operation under the working condition; s022, when the actual load demand of the unit under the certain working condition is smaller than the minimum operation load Q2 of the unit realized by frequency adjustment under the working condition, and when the frequency of the compressor is reduced to the minimum frequency H2 of the compressor operated under the working condition, the frequency of the compressor is kept unchanged, and a hot gas bypass valve is opened to reduce the load of the unit to the actual demand; s023, after the load of the unit under the certain working condition is reduced, the minimum frequency H2 of the compressor running under the working condition is reduced to H4, after the load of the unit is continuously stabilized for T0 time, the unit continues to reduce the frequency of the compressor to H4 according to the running frequency action period T1 and the frequency adjusting variable D1, and in the process of reducing the frequency of the compressor, the opening of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load requirement of the unit.
According to the control method of the variable-frequency centrifugal water chilling unit, the frequency difference is set between the anti-surge operation frequency line Y1 of the unit and the surge frequency line Y2 of the unit to serve as the anti-surge safety margin, so that the unit is ensured to be in surge when the unit operates under variable working conditions, the reserved safety margin can ensure that the unit cannot generate surge in the process of changing the working conditions because the pressure is changed firstly, and the unit needs a certain time for adjusting according to the pressure change, meanwhile, the unit load is reduced by controlling the operation frequency of a compressor of the unit, opening a hot gas bypass valve and the opening degree of a fine regulator, the unit surge is met and avoided, the anti-surge control of the unit is more accurately matched with the actual surge point of the unit, and compared with the traditional anti-surge control method, the operation range of the unit is expanded, and the operation performance and the reliability of the unit are improved.
Further, the control method of the variable-frequency centrifugal chiller unit of the embodiment of the invention further comprises the following steps: and S03, when the opening of the hot gas bypass valve is larger than 0%, the frequency of the compressor is continuously reduced by the unit according to the operating frequency action period T2 and the frequency adjusting variable D2, and the opening of the hot gas bypass valve is reduced according to the load change of the unit in the frequency reduction process of the compressor to meet the actual load requirement of the unit. Furthermore, the load of the unit is reduced by the hot gas bypass valve, so that the surging of the unit is avoided, but the bypass is not energy-saving when the bypass is opened, and the control is performed in reverse, so that the bypass is turned off, the frequency of the compressor is reduced, the performance of the unit is improved, and the load requirement can be ensured.
As shown in fig. 2 and fig. 3, in particular, in the present embodiment, the step S03 includes the following sub-steps: s031, calculating the compressor operation pressure ratio as the ratio between the condensing pressure and the evaporating pressure according to the condensing pressure and the evaporating pressure obtained by the pressure measuring device, wherein A1 is the compressor operation minimum pressure ratio, A2 is the compressor operation maximum pressure ratio, and dividing the compressor operation pressure ratio range A1-A2 into n pressure ratio intervals B1, B2 and B3 \8230andBn; based on the pressure ratio and the control precision requirement of the unit operation range, the operation pressure ratios of different units are different, for example, the pressure ratio of a conventional refrigerating unit is about 2.7, the pressure ratio of ice storage and a heat pump unit can reach 4.5, the more interval division is, the higher the control precision is, but the adjustment is required according to the actual requirement; s032, calculating the vibration change rate to be the ratio of the current vibration value to the average vibration value according to the vibration value of the compressor, setting surge judgment vibration change rate Z0, and judging that the unit has surge when the vibration change rate is not less than Z0; s033, calculating the current operation pressure ratio of the compressor according to the condensing pressure and the evaporating pressure obtained by the pressure measuring device; s034, when the unit is judged to have surge in the step S032, recording the current running pressure ratio and the compressor surge frequency of the compressor during the surge, and adding an anti-surge frequency increment H0 to the compressor surge frequency to serve as the minimum frequency of the compressor running in the current running pressure ratio interval; as shown in fig. 3, when the unit operates in the compressor pressure ratio interval B3, surge occurs, the surge frequency is H4, and the frequency after adding the surge-preventing frequency increment H0 is H5, then when the subsequent unit operates in the compressor pressure ratio interval B3, the compressor operating frequency must be equal to or greater than H5; s035, when the unit is judged to have surge in the step S032, the running frequency of the compressor is increased to the anti-surge running frequency value corresponding to the current running pressure ratio of the compressor, and meanwhile, the hot gas bypass valve is controlled to increase the opening according to the load change of the unit; s036, after the load of the unit is continuously stabilized for T0 time, the compressor performs frequency reduction operation, the unit continues to reduce the frequency of the compressor according to the operation frequency action period T2 and the frequency adjustment variable D2, and in the frequency reduction process of the compressor, the opening degree of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load requirement of the unit until the opening degree of the hot gas bypass butterfly valve is 0%. By the control, the running of the compressor is more consistent with the surge line, the running range of the unit is widened, the running performance of the unit is improved, meanwhile, the unit can automatically judge surge and automatically set the minimum running frequency for the pressure ratio interval of each compressor, the follow-up secondary surge of the unit is avoided, the anti-surge control precision is improved, and the reliability of the unit is improved.
Further, in this embodiment, the step S03 further includes a step S037, after the load of the unit is continuously stabilized for T0 time, the compressor performs frequency reduction operation, the unit continues to reduce the frequency of the compressor according to the operation frequency action period T2 and the frequency adjustment variable D2, and during the frequency reduction process of the compressor, the opening of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load requirement of the unit until the operation frequency of the compressor is reduced to the minimum frequency at which the compressor in the current operation pressure ratio interval can operate. Through the control, the subsequent surge of the unit can be avoided, the anti-surge control precision is improved, and the reliability of the unit is improved.
Further, in the present embodiment, the operation frequency operation period T2 is not less than the operation frequency operation period T1, and the frequency adjustment variable D2 is not greater than the frequency adjustment variable D1. Because surging is easy to occur when the unit operates in the step S03, the surging frequency of the unit under the corresponding pressure ratio is measured simultaneously in the control process, and the setting mode can ensure that the unit has small adjustment amount and long period, so that the unit operates more stably, and data in the measurement process is more accurate and reliable.
Specifically, in the present embodiment, T0, T1, T2, D1, and D2 are all variable setting values, with the unit of T0 being min, the unit of T1 and T2 being s, and the unit of D1 and D2 being Hz. For example, T1 is 10s, D1 is 3Hz, T2 is 20s, D2 is 1Hz, stable operation of the unit is ensured according to actual use, unit values of different refrigerating capacities are different, and fixed setting is not carried out. The load continuous stable time T0 of the unit, the operation frequency action periods T1 and T2 of the unit and the frequency adjusting variables D1 and D2 are set according to the method, so that the stable and reliable frequency reduction adjusting process of the compressor can be ensured to a great extent.
Example 3
The storage medium according to an embodiment of the present invention stores a computer program, and when the computer program is executed by a processor, the control method described above is executed.
According to the embodiment, the frequency conversion centrifugal water chilling unit and the control method thereof provided by the invention have the advantages that the operation range of the unit is controlled in a partitioned manner by detecting the pressure of the evaporator and the condenser of the unit and the vibration frequency of the compressor, the unit can judge surge automatically, the safe operation range can be corrected automatically, the unit surge prevention control and the actual surge point of the unit are more accurately matched by controlling the operation frequency of the compressor of the unit and coordinately adjusting the hot gas bypass butterfly valve, and compared with the traditional surge prevention control method, the operation range of the unit is expanded, and the operation performance and the reliability of the unit are improved.
While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Claims (12)
1. A frequency conversion centrifugal water chilling unit is characterized by comprising a condenser, an evaporator, a compressor, a frequency converter and a control unit; wherein,
a throttle valve and a hot gas bypass valve which are connected in parallel are arranged between the condenser and the evaporator, an air inlet and an air outlet of the compressor are respectively connected with the evaporator and the condenser, and the frequency converter is used for controlling the frequency of the compressor;
the condenser and the evaporator are both provided with pressure measuring devices for measuring absolute pressure, and the compressor is provided with a vibration measuring device;
and the control unit receives the data of the pressure measuring device, the hot gas bypass valve and the vibration measuring device for calculation processing, and controls the frequency converter and the hot gas bypass valve according to the calculation result.
2. The variable frequency centrifugal chiller according to claim 1 wherein said vibration measuring device comprises a vibration sensor disposed on a housing surface of said compressor.
3. The variable frequency centrifugal chiller according to claim 1 or 2 wherein said pressure measuring device comprises a pressure sensor.
4. The variable frequency centrifugal chiller according to claim 1 or 2 wherein said hot gas bypass valve comprises a butterfly valve.
5. A control method of a variable-frequency centrifugal chiller is implemented by the variable-frequency centrifugal chiller according to any one of claims 1 to 4, and is characterized by comprising the following steps:
s01, when the unit operates in a certain working condition, setting an anti-surge operation frequency line Y1 of the unit according to a relation curve Y0 of the operation frequency of a compressor of the unit and the load of the unit and a surge frequency line Y2 of the unit;
and S02, when the actual load requirement of the unit under a certain working condition is in different load intervals realized by frequency adjustment of the unit under the working condition, the unit adjusts the operating frequency of the compressor to be maintained in different intervals, and in the process of reducing the frequency of the compressor, the opening of the hot gas bypass valve is adjusted according to the load change of the unit to meet the actual load requirement of the unit.
6. The control method of the variable-frequency centrifugal chiller according to claim 5, wherein said step S02 comprises the substeps of:
s021, when the actual load requirement of the unit under a certain working condition is between the minimum operation load Q2 realized by the unit through frequency adjustment under the working condition and the maximum load Q1 of the unit under the working condition, the unit adjusts the operation frequency of the compressor according to the operation frequency action period T1 and the adjustment frequency variable D1 to be between the minimum frequency H2 of the compressor in operation under the working condition and the rated frequency H1 of the compressor in operation under the working condition;
s022, when the actual load demand of the unit under the certain working condition is smaller than the minimum operation load Q2 of the unit realized by frequency adjustment under the working condition, and when the frequency of the compressor is reduced to the minimum frequency H2 of the compressor operated under the working condition, the frequency of the compressor is kept unchanged, and a hot gas bypass valve is opened to reduce the load of the unit to the actual demand;
s023, after the load of the unit under the certain working condition is reduced, the minimum frequency H2 of the compressor running under the working condition is reduced to H4, after the load of the unit is continuously stabilized for T0 time, the unit continues to reduce the frequency of the compressor to H4 according to the running frequency action period T1 and the frequency adjusting variable D1, and in the process of reducing the frequency of the compressor, the opening of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load requirement of the unit.
7. The control method of the variable frequency centrifugal chiller according to claim 6 further comprising the steps of:
and S03, when the opening of the hot gas bypass valve is larger than 0%, the frequency of the compressor is continuously reduced by the unit according to the operating frequency action period T2 and the frequency adjusting variable D2, and the opening of the hot gas bypass valve is reduced according to the load change of the unit in the frequency reduction process of the compressor to meet the actual load requirement of the unit.
8. The control method of the variable-frequency centrifugal chiller according to claim 7, wherein step S03 comprises the substeps of:
s031, calculating the operation pressure ratio of the compressor as the ratio between the condensing pressure and the evaporating pressure according to the condensing pressure and the evaporating pressure obtained by the pressure measuring device, wherein A1 is the minimum operation pressure ratio of the compressor, A2 is the maximum operation pressure ratio of the compressor, and dividing the operation pressure ratio range A1-A2 of the compressor into n pressure ratio intervals B1, B2 and B3 \8230andBn;
s032, calculating a vibration change rate according to a vibration value of the compressor to be a ratio of a current vibration value to an average vibration value, setting a surge judgment vibration change rate Z0, and judging that the unit has surge when the vibration change rate is not less than Z0;
s033, calculating the current operation pressure ratio of the compressor according to the condensing pressure and the evaporating pressure obtained by the pressure measuring device;
s034, when the unit is judged to have surge in the step S032, recording the current running pressure ratio and the compressor surge frequency of the compressor during the surge, and adding an anti-surge frequency increment H0 to the compressor surge frequency to serve as the minimum frequency of the compressor running in the current running pressure ratio interval;
s035, when the unit is judged to have surge in the step S032, the running frequency of the compressor is increased to the anti-surge running frequency value corresponding to the current running pressure ratio of the compressor, and meanwhile, the hot gas bypass valve is controlled to increase the opening according to the load change of the unit;
s036, after the load of the unit is continuously stabilized for T0 time, the compressor performs frequency reduction operation, the unit continues to reduce the frequency of the compressor according to the operation frequency action period T2 and the frequency adjustment variable D2, and in the frequency reduction process of the compressor, the opening of the hot gas bypass valve is reduced according to the load change of the unit to meet the actual load requirement of the unit until the opening of the hot gas bypass butterfly valve is 0%.
9. The control method of the variable-frequency centrifugal chiller according to claim 8, further comprising step S037, after the chiller load continues to stabilize for T0, performing down-conversion operation on the compressor, continuing to reduce the frequency of the compressor by the chiller according to the operation frequency action period T2 and the frequency adjustment variable D2, and during the down-conversion process of the compressor, reducing the opening of the hot gas bypass valve according to the variation of the chiller load to meet the actual load demand of the chiller until the operation frequency of the compressor is reduced to the minimum frequency at which the compressor in the current operation pressure ratio range can operate.
10. The control method of the variable-frequency centrifugal chiller according to claim 7, wherein the operating frequency operating period T2 is not less than the operating frequency operating period T1, and the frequency adjustment variable D2 is not greater than the frequency adjustment variable D1.
11. The method of claim 7, wherein T0, T1, T2, D1 and D2 are all variable settings, T0 is in units of min, T1 and T2 are in units of s, and D1 and D2 are in units of Hz.
12. A storage medium, characterized in that it stores a computer program which, when executed by a processor, performs the control method according to any one of claims 5 to 11.
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