Control method, centrifugal compressor, refrigerating unit, control device and medium

Abstract

The invention discloses a control method, a centrifugal compressor, a refrigerating unit, a control device and a medium. The centrifugal refrigerating unit comprises a centrifugal compressor and a heat exchanger, the centrifugal compressor comprises guide vanes, and the control method comprises the steps that the target output power of the centrifugal compressor is determined according to water outlet temperature information of the heat exchanger under the current working condition; according to the performance parameters of the centrifugal compressor and the operation parameters of the heat exchanger under the current working condition, the current output power of the centrifugal compressor is determined; and under the condition that the difference value between the current output power and the target output power is smaller than or equal to a preset threshold value, operation of the centrifugal compressor is controlled according to the performance parameters, corresponding to the current output power, of the centrifugal compressor. The surge frequency, the overshoot of the outlet water temperature and the adjusting time can be reduced, the working interval of the centrifugal compressor is widened, and frequent start and stop of a refrigerating system are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and more specifically, to a control method, a centrifugal compressor, a centrifugal refrigeration unit, a control device and a computer-readable storage medium. Background Art

[0002] In the related art, the control logic used by the centrifugal compressor in the existing centrifugal water-cooling unit results in a small adjustable range of the surge frequency curve and the blocking frequency curve, which makes it easy for the centrifugal compressor to reach the surge frequency or blocking frequency boundary and be unable to effectively perform load addition and reduction, resulting in a large overshoot of the outlet water temperature of the centrifugal compressor, a long adjustment time, frequent start and stop, and low energy efficiency in the partial load area. Summary of the invention

[0003] A control method, a centrifugal compressor, a centrifugal refrigeration unit, a control device and a computer-readable storage medium provided in an embodiment of the present invention can solve the problems of large overshoot of outlet water temperature of the centrifugal compressor, long adjustment time, frequent start and stop and low energy efficiency in the partial load area.

[0004] The control method of the embodiment of the present invention is used for a centrifugal refrigeration unit. The centrifugal refrigeration unit includes a centrifugal compressor and a heat exchanger, the centrifugal compressor includes a guide vane, and the control method includes:

[0005] Determining the target output power of the centrifugal compressor according to the outlet water temperature information of the heat exchanger under the current working condition;

[0006] Determining the current output power of the centrifugal compressor according to the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under the current working conditions, wherein the performance parameters of the centrifugal compressor include the frequency of the centrifugal compressor, the high-low pressure ratio of the centrifugal compressor and the opening of the guide vane, and the operating parameters of the heat exchanger include the pressure of the heat exchanger and the enthalpy difference of the heat exchanger;

[0007] When the difference between the current output power and the target output power is less than or equal to a preset threshold, the operation of the centrifugal compressor is controlled according to the performance parameters of the centrifugal compressor corresponding to the current output power.

[0008] In this way, by determining the target output power of the compressor according to the outlet water temperature of the heat exchanger, and determining the optimal combination of compressor frequency and guide vane opening according to the target output power, the energy-adjustable response speed of the centrifugal compressor can be improved, the surge frequency, the overshoot of the outlet water temperature and the adjustment convergence time can be reduced, the working range of the centrifugal compressor can be effectively widened, and the frequent start and stop of the refrigeration system caused by insufficient unloading capacity due to excessive surge frequency protection can be reduced.

[0009] In some embodiments, determining the target output power of the centrifugal compressor according to the outlet water temperature information of the heat exchanger under the current working condition includes:

[0010] Determine, based on the outlet water temperature information, an actual error between the actual outlet water temperature of the heat exchanger and the target outlet water temperature under the current working condition, and an actual error change rate within a preset sampling time;

[0011] Determining the standard error and the standard error change rate according to the actual error, the actual error change rate and a preset standard domain;

[0012] Determining a non-zero membership according to the standard error, the standard error change rate and a preset membership function;

[0013] The membership value is determined according to the standard error, the standard error change rate and a preset fuzzy rule table.

[0014] In this way, by obtaining the error and error change rate between the actual outlet water temperature of the heat exchanger under the previous working condition and the target outlet water temperature, the non-zero membership degree and membership value can be calculated, which can pave the way for calculating the absolute power of the centrifugal compressor under the current working condition.

[0015] In some embodiments, the centrifugal compressor includes a capacity scheduler, the capacity scheduler is provided with an initial energy adjustment parameter, an initial domain and a membership function, and the target output power of the centrifugal compressor is determined according to the outlet water temperature of the heat exchanger under the current working condition, including:

[0016] Determining a standard gain corresponding to the initial adjustable parameter according to the non-zero membership degree and the membership value;

[0017] Determining an actual gain corresponding to the initial adjustable parameter according to the initial domain and the standard gain;

[0018] Update the initial energy-adjustable parameter according to the actual gain to obtain the current energy-adjustable parameter under the current working condition;

[0019] The target output power of the centrifugal compressor is determined according to the current adjustable parameters.

[0020] In this way, according to the non-zero membership degree, the membership value and the initial domain, the actual gain corresponding to the initial adjustable parameter can be determined, so that according to the actual gain, the output power of the centrifugal compressor adapted to the current working condition can be obtained.

[0021] In some embodiments, determining the current output power of the centrifugal compressor according to the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under the current working conditions includes:

[0022] Obtaining the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under current working conditions;

[0023] Determining the mass flow rate at the inlet of the centrifugal compressor according to the performance parameters of the centrifugal compressor and a preset centrifugal compressor performance model;

[0024] The current output power of the centrifugal compressor is determined according to the mass flow rate at the inlet of the centrifugal compressor, the evaporation pressure of the heat exchanger and the refrigerant enthalpy difference between the inlet and outlet of the heat exchanger.

[0025] In this way, by obtaining the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger, and inputting the parameters into a preset centrifugal compressor performance model, the maximum output power of the centrifugal compressor under the current working conditions can be determined.

[0026] In some embodiments, the centrifugal compressor includes a solver, the solver is provided with a preset threshold, and the control method includes:

[0027] When the difference between the current output power and the target output power is greater than the preset threshold, the centrifugal compressor is controlled to update the performance parameters of the centrifugal compressor.

[0028] In this way, when it is determined that the difference between the current output power and the target output power of the centrifugal compressor under the current operating conditions is greater than the preset threshold, it indicates that the performance of the current centrifugal compressor cannot meet the target requirements, so that the performance parameters of the centrifugal compressor can be adjusted in time to correct and widen the working range.

[0029] In some embodiments, the solver is provided with a surge frequency of the centrifugal compressor, a blocking frequency of the centrifugal compressor, and an opening range value of the guide vane, and determines the performance parameter of the centrifugal compressor corresponding to the current output power, including:

[0030] controlling the frequency of the centrifugal compressor to be greater than a current surge frequency of the centrifugal compressor;

[0031] Controlling the frequency of the centrifugal compressor to be less than or equal to the blocking frequency of the centrifugal compressor;

[0032] Controlling the frequency change rate of the centrifugal compressor to be within a preset frequency change rate range;

[0033] The opening of the guide vane is controlled to be within a preset opening range of the guide vane, and the opening change rate of the guide vane is controlled to be within a preset change rate range.

[0034] In this way, while meeting the target power output, by setting the frequency of the centrifugal compressor between the surge frequency of the centrifugal compressor and the blocking frequency of the centrifugal compressor and setting the opening of the guide vane within a preset opening range, the centrifugal compressor can be operated with the optimal combination of centrifugal compressor frequency and guide vane opening, thereby avoiding frequent starting and stopping of the centrifugal compressor and improving the energy efficiency of the centrifugal compressor.

[0035] In some implementations, the surge frequency of the centrifugal compressor includes an original value of the surge frequency of the centrifugal compressor and a correction value of the surge frequency of the centrifugal compressor, and determining the performance parameter of the centrifugal compressor corresponding to the current output power includes:

[0036] Collecting the operating parameters of the centrifugal compressor at a preset frequency within a preset period of time, wherein the operating parameters include the current, suction and exhaust pressure, and suction and exhaust temperature of the centrifugal compressor;

[0037] Calculating a surge risk index of the centrifugal compressor according to the operating parameters of the centrifugal compressor;

[0038] When the surge risk index of the centrifugal compressor is greater than a preset index, the frequency, pressure ratio and opening of the guide vane of the centrifugal compressor are recorded, and the frequency of the centrifugal compressor is gradually increased according to a preset frequency segment, so that when the surge risk index of the centrifugal compressor is less than the preset index, the increased frequency value of the centrifugal compressor is obtained to determine the surge frequency correction value of the centrifugal compressor;

[0039] The current surge frequency of the centrifugal compressor is determined according to the surge frequency correction value of the centrifugal compressor and the surge frequency original value of the centrifugal compressor.

[0040] In this way, the operating parameters of the centrifugal compressor are collected to calculate the surge risk index of the centrifugal compressor, and the surge risk index of the centrifugal compressor is compared with a preset index to determine the surge frequency correction value, thereby improving the range between the surge frequency of the centrifugal compressor and the blocking frequency of the centrifugal compressor.

[0041] The control device of the embodiment of the present invention includes a processor and a memory; the memory stores a computer program, the computer program is executed by the processor, and the computer program includes instructions for executing the control method described in any one of the above embodiments.

[0042] The centrifugal compressor according to the embodiment of the present invention comprises the control device and the guide vane described in any one of the above embodiments, and the control device is electrically connected to the guide vane.

[0043] The centrifugal refrigeration unit according to the embodiment of the present invention comprises the centrifugal compressor described in any one of the above embodiments.

[0044] The non-volatile computer-readable storage medium containing a computer program according to an embodiment of the present invention includes a computer program. When the computer program is executed by a processor, the processor executes the control method described in any one of the above embodiments.

[0045] Additional aspects and advantages of embodiments of the present invention will be given in part in the following description and in part will be obvious from the following description or learned through practice of embodiments of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0047] Figure 1 is a flow chart of a control method of certain embodiments of the present invention;

[0048] Figure 2 is a schematic diagram of a module of a centrifugal refrigeration unit according to certain embodiments of the present invention;

[0049] Figure 3 is a schematic diagram of a module of a control device in some embodiments of the present invention;

[0050] Figure 4 is a flow chart of a control method of certain embodiments of the present invention;

[0051] Figure 5 is a flow chart of a control method of certain embodiments of the present invention;

[0052] Figure 6 is a schematic diagram of a module of a centrifugal compressor according to certain embodiments of the present invention;

[0053] Figure 7 is a flow chart of a control method of certain embodiments of the present invention;

[0054] Figure 8 is a flow chart of a control method of certain embodiments of the present invention;

[0055] Fig. 9 is a flow chart of a control method of certain embodiments of the present invention;

[0056] Fig.10is a flow chart of a control method of certain embodiments of the present invention;

[0057] Fig.11 It is a schematic diagram of the connection status of a computer-readable storage medium and a processor according to some embodiments of the present invention.

[0058] Description of Figure Numbers:

[0059] 100. Centrifugal refrigeration unit; 10. Centrifugal compressor; 11. Guide vane; 12. Capacity scheduler; 13. Solver; 14. Control device; 141. Processor; 142. Memory; 143. Computer program; 20. Heat exchanger; 200. Computer-readable storage medium. DETAILED DESCRIPTION

[0060] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions from beginning to end. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the embodiments of the present invention, and cannot be understood as limiting the embodiments of the present invention.

[0061] See also Figure 1 , Figure 2 and Figure 3 The control method of the embodiment of the present invention is used for a centrifugal refrigeration unit 100. The centrifugal refrigeration unit 100 includes a centrifugal compressor 10 and a heat exchanger 20, the centrifugal compressor 10 includes a guide vane 11, and the control method includes:

[0062] Step 011: determining the target output power of the centrifugal compressor 10 according to the outlet water temperature information of the heat exchanger 20 under the current working condition, where the outlet water temperature information includes the actual outlet water temperature and the target outlet water temperature;

[0063] Step 012: determining the current output power of the centrifugal compressor 10 according to the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current working condition, wherein the performance parameters of the centrifugal compressor 10 include the frequency of the centrifugal compressor 10, the high and low pressure ratio of the centrifugal compressor 10 and the opening of the guide vane 11, and the operating parameters of the heat exchanger 20 include the pressure of the heat exchanger 20 and the enthalpy difference of the heat exchanger 20;

[0064] Step 013: When the difference between the current output power and the target output power is less than or equal to a preset threshold, the operation of the centrifugal compressor 10 is controlled according to the performance parameters of the centrifugal compressor 10 corresponding to the current output power.

[0065] In this way, by determining the target output power of the compressor according to the outlet water temperature of the heat exchanger 20, and determining the optimal combination of the compressor frequency and the opening of the guide vane 11 according to the target output power, the energy-adjustable response speed of the centrifugal compressor 10 is improved, the surge frequency, the overshoot of the outlet water temperature and the adjustment convergence time can be reduced, the working range of the centrifugal compressor 10 is effectively widened, and the frequent start and stop of the refrigeration system caused by insufficient unloading capacity due to excessive surge frequency protection is reduced.

[0066] The centrifugal refrigeration unit 100 may be a first-stage centrifugal refrigeration unit 100 or a second-stage centrifugal refrigeration unit 100 with a flash tank or a plate economizer, and can provide low-temperature chilled water through a refrigeration cycle to meet various refrigeration needs. The second-stage centrifugal refrigeration unit 100 of the present application is used as an example for explanation. The centrifugal refrigeration unit 100 includes a centrifugal compressor 10 and a heat exchanger 20. The centrifugal compressor 10 can provide power for the refrigerant gas to move through centrifugal force, and perform heat exchange when the refrigerant gas passes through the heat exchanger 20, thereby realizing a refrigeration cycle. The heat exchanger 20 may be an evaporator or a condenser. The heat exchanger 20 of the present application is exemplified as an evaporator.

[0067] The centrifugal compressor 10 includes a control device and a guide vane 11, and the control device 14 includes a processor 141, a memory 142 and a computer program 143. The computer program 143 is stored in the memory 142 and executed by the processor 141, and the computer program 143 includes instructions for executing the control method. The guide vane 11 is arranged between the heat exchanger 20 and the centrifugal compressor 10, and the guide vane 11 can drive the refrigerant gas to rotate at a high speed, so that the refrigerant gas generates centrifugal force, thereby compressing the refrigerant gas and increasing its pressure and flow rate, and assisting in regulating the refrigerant flow.

[0068] Specifically, the processor 141 can obtain the outlet water temperature information of the heat exchanger 20 under the current working condition, and can determine the target output power of the centrifugal compressor 10 according to the outlet water temperature information of the heat exchanger 20 under the current working condition. For example, the current operating condition may be that the centrifugal refrigeration unit 100 is in a refrigeration cycle, and the heat exchanger 20 may be an evaporator. A temperature sensor is provided at the water outlet of the evaporator, so that the temperature sensor can detect the actual water outlet temperature of the refrigerant flowing out after heat exchange in the evaporator and upload the actual water outlet temperature to the processor 141. After receiving the actual water outlet temperature of the evaporator, the processor 141 compares the target water outlet temperature required by the user pre-stored in the memory 142 with the actual water outlet temperature of the current evaporator, and can obtain the temperature difference between the actual water outlet temperature and the preset target water outlet temperature under the current operating condition. According to the size of the temperature difference, it can be determined whether the refrigeration effect of the centrifugal refrigeration unit 100 is insufficient. If it is insufficient, the power of the centrifugal compressor 10 needs to be increased. Therefore, according to the water outlet temperature of the evaporator under the current operating condition, the target output power of the centrifugal compressor 10 can be determined, so that the actual water outlet temperature of the evaporator is close to the target water outlet temperature.

[0069] The processor 141 can determine the current output power of the centrifugal compressor 10 according to the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current working conditions. Among them, the performance parameters of the centrifugal compressor 10 include the frequency of the centrifugal compressor 10, the high-low pressure ratio of the centrifugal compressor 10 and the opening of the guide vane 11, and the operating parameters of the heat exchanger 20 include the pressure of the heat exchanger 20 and the enthalpy difference of the heat exchanger 20. It should be noted that the frequency of the centrifugal compressor 10 can be the rotation frequency of the rotating shaft in the centrifugal compressor 10; the high-low pressure ratio of the centrifugal compressor 10 can be the ratio of the outlet pressure to the inlet pressure of the centrifugal compressor 10; the opening of the guide vane 11 can be the difference between the angle of the guide vane 11 on the air inlet side of the centrifugal compressor 10 and the angle of the guide vane 11 on the exhaust side; the pressure of the heat exchanger 20 can be the pressure of the refrigerant when it vaporizes in the evaporator; the enthalpy difference of the heat exchanger 20 can be the difference between the enthalpy value of the refrigerant at the inlet of the evaporator and the enthalpy value of the refrigerant at the outlet of the evaporator. For example, after obtaining the performance parameters of the centrifugal compressor 10, the processor 141 can calculate the refrigerant mass flow rate of the centrifugal compressor 10 based on the performance parameters and the preset performance model of the centrifugal compressor 10, and by calculating the refrigerant mass flow rate in combination with the operating parameters of the heat exchanger 20, the current output power of the centrifugal compressor 10 under the current operating conditions can be obtained.

[0070] The processor 141 compares the target output power of the centrifugal compressor 10 with the current output power of the centrifugal compressor 10 under the current working condition, and can control the operation of the centrifugal compressor 10 according to the performance parameters of the centrifugal compressor 10 corresponding to the current output power when the difference between the current output power and the target output power is less than or equal to the preset threshold. The preset threshold is pre-stored in the memory 142, and the preset threshold can measure whether the output power of the current centrifugal compressor 10 can meet the refrigeration demand of the centrifugal refrigeration unit 100, and the preset threshold can be 1%, 2%, 5%, etc. of the rated power. For example, when the preset threshold is 5%, the processor 141 can calculate that the target output power of the centrifugal compressor 10 needs to be 80% of the rated power by obtaining the outlet water temperature of the heat exchanger 20 under the current operating conditions, and the processor 141 can calculate that the current output power is 81% of the rated power based on the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current operating conditions, so that the difference between the target output power and the current output power is less than the preset threshold of 5%. Therefore, the processor 141 can control the operation of the centrifugal compressor 10 according to the performance parameters of the centrifugal compressor 10 corresponding to the current output power.

[0071] See also Figure 4 In some embodiments, step 011: determining the target output power of the centrifugal compressor 10 according to the outlet water temperature information of the heat exchanger 20 under the current working condition, comprises:

[0072] Step 0111: determining the actual error between the actual outlet water temperature of the heat exchanger 20 and the target outlet water temperature under the current working condition, and the actual error change rate within a preset sampling time according to the outlet water temperature information;

[0073] Step 0112: Determine the standard error and the standard error change rate according to the actual error, the actual error change rate and the preset standard domain;

[0074] Step 0113: determining a non-zero membership according to the standard error, the standard error change rate and a preset membership function;

[0075] Step 0114: Determine the membership value according to the standard error, the standard error change rate and the preset fuzzy rule table.

[0076] In this way, by obtaining the error and error change rate between the actual outlet water temperature and the target outlet water temperature of the heat exchanger 20 under the previous working condition, the non-zero membership degree and membership value can be calculated, which can pave the way for calculating the absolute power of the centrifugal compressor 10 under the current working condition.

[0077] Specifically, after acquiring the outlet water temperature information of the heat exchanger 20, the processor 141 can determine the error between the actual outlet water temperature of the heat exchanger 20 and the target outlet water temperature under the current working condition, as well as the error change rate within the preset sampling time. For example, when the sampling time is 5 seconds, the processor 141 can collect the outlet water temperature of the heat exchanger 20 every 5 seconds, and compare the outlet water temperature collected each time with the target outlet water temperature preset in the memory 142, so that the processor 141 can obtain the error between the actual outlet water temperature of the heat exchanger 20 under the current working condition and the target outlet water temperature, and compare the errors obtained at each sampling time, and can determine the error change rate.

[0078] The processor 141 can determine the standard error and the standard error change rate based on the actual error, the actual error change rate and the preset standard domain. Among them, in the fuzzy control system, the process of mapping the actual error and the actual error change rate to the standard domain (also called the basic domain or the fuzzy set domain) is called quantization or scaling. The standard domain can be set in the memory 142, and the standard domain can be a fixed range. For example, the standard domain can be [-3, 3]. The processor 141 can obtain the standard error and the standard error change rate by mapping the actual error and the actual error change rate between the actual outlet water temperature of the heat exchanger 20 and the target outlet water temperature under the current operating conditions to the standard domain. For example, the formula for mapping the actual error e to the standard domain e′ is:

[0079] e , =6 / (e max -e min) *(ee min )-3

[0080] The formula for mapping the actual error change rate ec to the standard domain ec′ is:

[0081] ec , =6 / (ec max -ec min) *(ec-ec min )-3

[0082] Among them, the ranges of actual error e and error change rate ec are [e min , e max ] and [ec min ,ec max ], the standard domain is [-6, 6], and the standard error is e , , the standard error rate of change is ec , .

[0083] The processor 141 can determine the non-zero membership corresponding to the standard error and the standard error change rate according to the obtained standard error, the standard error change rate and the membership function preset in the memory 142. The membership function can define the degree of membership of each fuzzy set, and the membership function can be a triangular membership function, a Gaussian membership function or a trapezoidal membership function. For example, in the case where the membership function is a triangular membership function, by substituting the standard error and the standard error change rate into the triangular membership function respectively, the non-zero membership corresponding to the standard error and the non-zero membership corresponding to the standard error change rate can be obtained.

[0084] The processor 141 can determine the membership value corresponding to the standard error and the standard error change rate according to the obtained standard error, the standard error change rate and the fuzzy rule table preset in the memory 142. Among them, in the fuzzy proportional, integral and differential control system, the fuzzy rule table can determine the adjustment amount of the proportional gain, integral gain and differential gain of the proportional, integral and differential controller according to the error and the error change rate, that is, the fuzzy rule contains the adjustment strategy of the proportional gain, integral gain and differential gain corresponding to the combination of different standard errors and standard error change rates, and the adjustment strategy can be increase, decrease or remain unchanged. The processor 141 can obtain the corresponding membership value for each combination of standard error and standard error change rate by searching the fuzzy rule table.

[0085] See also Figure 5 and Figure 6 In some embodiments, the centrifugal compressor 10 includes a capacity scheduler 12, and the capacity scheduler 12 is provided with an initial energy adjustment parameter, an initial domain, and a membership function. Step 011: determining the target output power of the centrifugal compressor 10 according to the outlet water temperature of the heat exchanger 20 under the current working condition, including:

[0086] Step 0115: Determine the standard gain corresponding to the initial adjustable parameter according to the non-zero membership degree and membership value;

[0087] Step 0116: Determine the actual gain corresponding to the initial adjustable parameter according to the initial domain and the standard gain;

[0088] Step 0117: Update the initial energy-adjustable parameters according to the actual gain to obtain the current energy-adjustable parameters under the current working condition;

[0089] Step 0118: Determine the target output power of the centrifugal compressor 10 based on the current adjustable parameters.

[0090] In this way, according to the non-zero membership degree, the membership value and the initial domain, the actual gain corresponding to the initial adjustable parameter can be determined, so that according to the actual gain, the output power of the centrifugal compressor 10 adapted to the current working condition can be obtained.

[0091] Specifically, the centrifugal compressor 10 includes a capacity scheduler 12, which can be set in the control device 14. The capacity scheduler 12 is provided with initial adjustable parameters, initial domain and membership function, and the initial adjustable parameters can be initial proportional, integral and differential parameters; for example, the initial adjustable parameters can be expressed as kp, ki and kd. In a fuzzy control system, the initial domain can define the entire range of values ​​that the input or output variable can take; the membership function can define the degree of membership of each fuzzy set.

[0092] After the processor 141 obtains the non-zero membership and membership value, the standard gain corresponding to the initial adjustable parameter can be obtained by weighted summing the membership function. The weight of the weighted summation of the membership function is the specific value of the gain given in the fuzzy rule table. For example, the standard gain corresponding to kp, ki and kd can be δkp', δki' and δkd'.

[0093] Then, the processor 141 maps the standard gain to the initial domain, and can determine the actual gain corresponding to the initial adjustable parameter; for example, the processor 141 maps the standard gain to the initial domain by using an appropriate scaling factor, so that the standard gain can be converted into the actual gain. For example, the actual gain corresponding to the standard gain δkp', δki' and δkd' may be δkp, δki and δkd.

[0094] Then, the processor 141 can update the initial adjustable parameter according to the actual gain amount obtained, so as to obtain the current adjustable parameter under the current working condition. The current adjustable parameter can be obtained by adding the initial adjustable parameter to the actual gain amount. For example, the updated adjustable parameter kp1 can be kp+δkp, the current adjustable parameter ki1 can be ki+δki, and the current adjustable parameter kd1 can be kd+δkd.

[0095] The processor 141 can determine the target output power of the centrifugal compressor 10 according to the current adjustable parameters. For example, the processor 141 can determine the target output power of the centrifugal compressor 10 according to the temperature difference between the current outlet water temperature of the heat exchanger 20 and the target outlet water temperature, and calculate the proportion, integral and differential value of the temperature difference.

[0096] See also Figure 7 In some embodiments, step 012: determining the current output power of the centrifugal compressor 10 according to the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current working conditions, comprises:

[0097] Step 0121: Obtaining the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current working conditions;

[0098] Step 0122: Determine the mass flow rate at the inlet of the centrifugal compressor 10 according to the performance parameters of the centrifugal compressor 10 and a preset performance model of the centrifugal compressor 10;

[0099] Step 0123: Determine the current output power of the centrifugal compressor 10 according to the mass flow rate at the inlet of the centrifugal compressor 10, the evaporation pressure of the heat exchanger 20, and the refrigerant enthalpy difference between the inlet and outlet of the heat exchanger 20.

[0100] In this way, by acquiring the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 and inputting the parameters into a preset performance model of the centrifugal compressor 10, the maximum output power of the centrifugal compressor 10 under the current operating conditions can be determined.

[0101] Specifically, the processor 141 can obtain the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current working conditions. Among them, the performance parameters of the centrifugal compressor 10 include the frequency of the centrifugal compressor 10, the high and low pressure ratio of the centrifugal compressor 10 and the opening of the guide vane 11, and the operating parameters of the heat exchanger 20 include the pressure of the heat exchanger 20 and the enthalpy difference of the heat exchanger 20. It should be noted that the frequency of the centrifugal compressor 10 can be the rotation frequency of the rotating shaft in the centrifugal compressor 10; the high and low pressure ratio of the centrifugal compressor 10 can be the ratio of the outlet pressure of the centrifugal compressor 10 to the inlet pressure; the opening of the guide vane 11 can be the difference between the angle of the guide vane 11 on the air inlet side of the centrifugal compressor 10 and the angle of the guide vane 11 on the exhaust side; the pressure of the heat exchanger 20 can be the pressure of the refrigerant when it vaporizes in the evaporator; the enthalpy difference of the heat exchanger 20 can be the difference between the enthalpy value of the refrigerant at the inlet of the evaporator and the enthalpy value of the refrigerant at the outlet of the evaporator. After the processor 141 obtains the performance parameters of the centrifugal compressor 10 , it can calculate the refrigerant mass flow rate of the centrifugal compressor 10 according to the performance parameters and the performance model of the centrifugal compressor 10 preset in the memory 142 .

[0102] For example, the performance model of the centrifugal compressor 10 may be a neural network model having three neural network layers. The input vector of the performance model of the centrifugal compressor 10 is x=[P e ,ε,ω,D1], the expression can be expressed as:

[0103] Demand=f(x)=σ(W2·tanh(W1·x+b1)+b2)

[0104] Wherein, Demand represents the current output power of the centrifugal compressor 10; P erepresents the pressure of the heat exchanger 20; ε represents the high and low pressure ratio of the centrifugal compressor; ω represents the frequency of the centrifugal compressor; D1 represents the opening of the guide vane; W1 is the first layer weight coefficient matrix with a shape of i×4, b1 is the first layer bias coefficient matrix with a shape of i×1, W2 is the second layer weight coefficient matrix with a shape of j×i, b2 is the second layer bias coefficient matrix with a shape of j×1, and the first layer activation function The second layer activation function The network parameter matrix vectors W1, W2, b1, b2 can be fitted by the directional propagation BP method according to the data of the actual four-dimensional mapping table. According to the motor energy consumption test data, the energy consumption characteristic function g(ε, ω) of the compressor inverter can be fitted by a polynomial empirical formula.

[0105] The processor 141 can obtain the current output power of the centrifugal compressor 10 under the current working condition by calculating the refrigerant mass flow rate in combination with the operating parameters of the heat exchanger 20.

[0106] See also Figure 6 and Figure 8 In some embodiments, the centrifugal compressor 10 includes a solver 13, the solver 13 is provided with a preset threshold, and the control method includes:

[0107] Step 014 : When the difference between the current output power and the target output power is greater than a preset threshold, the centrifugal compressor 10 is controlled to update the performance parameters of the centrifugal compressor 10 .

[0108] In this way, when it is determined that the difference between the current output power and the target output power of the centrifugal compressor 10 under the current operating conditions is greater than the preset threshold, it indicates that the current performance of the centrifugal compressor 10 cannot meet the target requirements, so that the performance parameters of the centrifugal compressor 10 can be adjusted in time to reduce the occurrence of compressor surge.

[0109] Specifically, the centrifugal compressor 10 includes a solver 13, which can solve the optimal solution of the performance parameters of the centrifugal compressor 10 when the current output power of the centrifugal compressor 10 is known. The solver 13 is provided with a preset threshold value, which can be an adjustable dead zone value in the solver 13. In the control system, the adjustable dead zone value refers to the input signal range corresponding to the zero output in the transfer function of the control system. Within this range, even if the input signal changes, there will be no perceptible change in the output of the control system. Therefore, the adjustable dead zone value can reduce the response of the centrifugal compressor 10 to tiny signal fluctuations, thereby reducing the frequency of frequency adjustment and energy consumption of the centrifugal compressor 10, that is, avoiding small-range and high-frequency fluctuations of the current output power of the centrifugal compressor 10, so as to improve the stability of the centrifugal compressor 10.

[0110] When the difference between the current output power and the target output power is greater than a preset threshold, the processor 141 can control the centrifugal compressor 10 to update the performance parameters of the centrifugal compressor 10. For example, the target output power is represented by Demandi, the current output power is represented by Demando, and the preset threshold is Δ. When |Demandi-Demando|≤Δ, the current frequency of the centrifugal compressor 10 and the opening of the guide vane 11 are kept unchanged; when |Demandi-Demando|>Δ, it means that the current output power of the centrifugal compressor 10 cannot meet the target output power, and the new frequency of the centrifugal compressor 10 and the opening of the guide vane 11 need to be recalculated.

[0111] See also Fig. 9 In some embodiments, the solver 13 is provided with a surge frequency of the centrifugal compressor 10, a blocking frequency of the centrifugal compressor 10, and an opening range value of the guide vane 11. Step 013: determining the performance parameters of the centrifugal compressor 10 corresponding to the current output power includes:

[0112] Step 0131: Control the frequency of the centrifugal compressor 10 to be greater than the current surge frequency of the centrifugal compressor 10;

[0113] Step 0132: Control the frequency of the centrifugal compressor 10 to be less than or equal to the blocking frequency of the centrifugal compressor 10;

[0114] Step 0133: Control the frequency change rate of the centrifugal compressor 10 to be within a preset frequency change rate range;

[0115] Step 0134: Control the opening of the guide vane 11 to be within a preset opening range of the guide vane 11 and control the opening change rate of the guide vane 11 to be within a preset change rate range.

[0116] In this way, under the condition of meeting the target power output, by setting the frequency of the centrifugal compressor 10 between the surge frequency of the centrifugal compressor 10 and the blocking frequency of the centrifugal compressor 10, and setting the opening of the guide vane 11 within the preset opening range, the centrifugal compressor 10 can be operated with the optimal combination of the frequency of the centrifugal compressor 10 and the opening of the guide vane 11, thereby avoiding frequent starting and stopping of the centrifugal compressor 10 and improving the energy efficiency of the centrifugal compressor 10. It should be noted that the optimal combination of the frequency of the centrifugal compressor 10 and the opening of the guide vane 11 refers to a combination that enables the centrifugal compressor to operate at optimal efficiency.

[0117] Specifically, the solver 13 is provided with the surge frequency of the centrifugal compressor 10, the blocking frequency of the centrifugal compressor 10 and the opening range value of the guide vane 11. Among them, the surge frequency of the centrifugal compressor 10 refers to the frequency of the vibration or pressure pulsation of the centrifugal compressor 10 under the surge condition. The blocking frequency of the centrifugal compressor 10 can be the frequency of the centrifugal compressor 10 when the flow rate of the centrifugal compressor 10 reaches the upper limit. At this time, the centrifugal compressor 10 cannot continue to increase the flow rate, thereby showing a blocking phenomenon. The opening range value of the guide vane 11 can be the maximum value and the minimum value that the opening of the guide vane 11 can reach.

[0118] When the solver 13 solves the optimal performance parameter combination of the centrifugal compressor 10 according to the current output power, it is necessary to control the solved frequency of the centrifugal compressor 10 to be greater than the surge frequency of the centrifugal compressor 10 under the current operating condition, so as to avoid the surge phenomenon of the centrifugal compressor 10.

[0119] The solved frequency of the centrifugal compressor 10 needs to be controlled to be less than or equal to the blocking frequency of the centrifugal compressor 10 , so as to avoid the blocking phenomenon of the centrifugal compressor 10 .

[0120] It should be noted that the frequency change rate of the centrifugal compressor needs to be controlled within a preset frequency change rate range. For example, the preset frequency change rate range is 0-15 Hz / s, so the frequency change rate of the centrifugal compressor can be 1 Hz / s, 2 Hz / s, 3 Hz / s, 4 Hz / s, 5 Hz / s or any value between 0-15 Hz / s.

[0121] The opening of the guide vane 11 obtained by the solution needs to be controlled to be within the preset opening range of the guide vane 11, so as to avoid the opening of the guide vane 11 failing to reach the target opening. And the solver 13 needs to consider the limitation of the maximum change rate of the guide vane 11. For example, the maximum change rate of the guide vane 11 is 5% per second. Among the solutions of the target opening of the guide vane 11 obtained by the solver 13, the solution that makes the current opening of the guide vane 11 reach the target opening as quickly as possible through the maximum change rate of the guide vane 11 with the least time is the optimal solution.

[0122] See also Fig.10 In some embodiments, the surge frequency of the centrifugal compressor 10 includes an original value of the surge frequency of the centrifugal compressor 10 and a correction value of the surge frequency of the centrifugal compressor 10. Step 0131: controlling the frequency of the centrifugal compressor 10 to be greater than the current surge frequency of the centrifugal compressor 10 includes:

[0123] Step 01311: collecting operating parameters of the centrifugal compressor 10 at a preset frequency within a preset period of time, the operating parameters including the current, suction and exhaust pressure, and suction and exhaust temperature of the centrifugal compressor 10;

[0124] Step 01312: Calculate the surge risk index of the centrifugal compressor 10 according to the operating parameters of the centrifugal compressor 10;

[0125] Step 01313: when the surge risk index of the centrifugal compressor 10 is greater than a preset index, the frequency, pressure ratio and opening of the guide vane 11 of the centrifugal compressor 10 are recorded, and the frequency of the centrifugal compressor 10 is gradually increased according to the preset frequency segment, so that when the surge risk index of the centrifugal compressor 10 is less than the preset index, the increased frequency value of the centrifugal compressor 10 is obtained to determine the surge frequency correction value of the centrifugal compressor 10;

[0126] Step 01314: Determine the current surge frequency of the centrifugal compressor 10 according to the surge frequency correction value of the centrifugal compressor 10 and the original value of the surge frequency of the centrifugal compressor 10;

[0127] In this way, by collecting the operating parameters of the centrifugal compressor 10 to calculate the surge risk index of the centrifugal compressor 10, and comparing the surge risk index of the centrifugal compressor 10 with a preset index to determine the surge frequency correction value, the range between the surge frequency of the centrifugal compressor 10 and the blocking frequency of the centrifugal compressor 10 can be increased.

[0128] Specifically, the surge frequency of the centrifugal compressor 10 includes the original value of the surge frequency of the centrifugal compressor 10 and the correction value of the surge frequency of the centrifugal compressor 10. Among them, the original value of the surge frequency of the centrifugal compressor 10 can be expressed as the frequency of the surge phenomenon that occurs naturally in the centrifugal compressor 10 without any external interference or control measures, and the original value is the empirical fitting curve obtained by the prototype in the laboratory. However, each machine will be different, and the actual surge frequency corresponding to each operating condition will also be different. Therefore, the purpose of this algorithm is to perform differentiated corrections for each device. The correction value of the surge frequency of the centrifugal compressor 10 can be the change in the surge frequency of the centrifugal compressor 10 or the adjusted value after taking certain anti-surge control measures.

[0129] Since the occurrence of surge is affected by many factors, such as the structural characteristics of the centrifugal compressor 10, flow changes, pipe network resistance, rotation speed, etc., the surge frequency is not a fixed value, but changes with the change of operating conditions. Therefore, in order to avoid the occurrence of surge in the centrifugal compressor 10, it is necessary to consider both the original value of the surge frequency of the centrifugal compressor 10 and the surge frequency correction value of the centrifugal compressor 10.

[0130] The processor 141 obtains the surge frequency correction value of the centrifugal compressor 10 by collecting operating parameters of the centrifugal compressor 10 at a preset frequency within a preset period of time. For example, the operating parameters may be the current, intake and exhaust pressure, and intake and exhaust temperature of the centrifugal compressor 10.

[0131] The processor 141 calculates the surge risk index of the centrifugal compressor 10 according to the operating parameters of the centrifugal compressor 10. The processor 141 can continuously calculate the signal fluctuation indexes within the preset time period, and can calculate the surge risk index after weighting the signal fluctuation indexes. For example, after the processor 141 obtains the collected operating parameters of the centrifugal compressor 10, it can screen and standardize the operating parameters, and then perform a differential calculation. When it is determined that the first-order derivative has not changed its sign, a secondary differential is performed. It should be noted that the purpose of the secondary differential is to determine the fluctuation number and thus calculate the surge risk index. Then, it is determined whether the surge risk index of the centrifugal compressor 10 is greater than the preset index; if it is determined that it exceeds the preset index, the operating parameters of the centrifugal compressor 10 collected within the next preset time period are re-acquired, and the surge factor of the current characteristic sensor parameter is calculated according to the signal fluctuation index within the preset time period, and after weighting the surge factor, it is determined whether the surge risk index of the centrifugal compressor 10 is greater than the preset index; if the surge risk index of the centrifugal compressor 10 is greater than the preset index, the surge judgment is performed again.

[0132] And when the surge risk index of the centrifugal compressor 10 is greater than the preset index, it can be determined that the centrifugal compressor 10 enters the surge zone, and the processor 141 can control the memory 142 to record the frequency, pressure ratio and opening of the guide vane 11 of the centrifugal compressor 10 at this time, and gradually increase the frequency of the centrifugal compressor 10 according to the frequency segment pre-set in the memory 142, and repeatedly calculate the surge risk index of the centrifugal compressor 10 during the increase process.

[0133] When the frequency of the centrifugal compressor 10 is increased so that the surge risk index of the centrifugal compressor 10 is less than a preset index, the increased frequency value of the centrifugal compressor 10 is obtained, so that the increased frequency value can be determined as the surge frequency correction value of the centrifugal compressor 10.

[0134] The processor 141 can update the current surge frequency of the centrifugal compressor 10 according to the surge frequency correction value of the centrifugal compressor 10 and the original value of the surge frequency of the centrifugal compressor 10. Finally, the processor 141 determines the performance parameters of the centrifugal compressor 10 according to the updated current surge frequency of the centrifugal compressor 10, and can avoid the occurrence of surge phenomenon when the frequency of the centrifugal compressor 10 is greater than the updated current surge frequency of the centrifugal compressor 10.

[0135] See also Fig.11 The embodiment of the present invention further provides a computer-readable storage medium 200 on which a computer program 143 is stored. When the computer program 143 is executed by the processor 141, the steps of the control method of any of the above-mentioned embodiments are implemented. For the sake of brevity, they are not repeated here.

[0136] In the description of this specification, the descriptions with reference to the terms "certain embodiments", "in an example", "exemplarily", etc., mean that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0137] Any process or method description in a flowchart or otherwise described herein may be understood to represent a module, segment or portion of code that includes one or more executable instructions for implementing the steps of a specific logical function or process, and the scope of the preferred embodiments of the present invention includes alternative implementations in which functions may not be performed in the order shown or discussed, including performing functions in a substantially simultaneous manner or in the reverse order depending on the functions involved, which should be understood by those skilled in the art to which the embodiments of the present invention belong.

[0138] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A control method for a centrifugal refrigeration unit, characterized in that: The centrifugal refrigeration unit includes a centrifugal compressor and a heat exchanger, the centrifugal compressor includes a guide vane, and the control method includes: Determine the target output power of the centrifugal compressor according to the outlet water temperature information of the heat exchanger under the current working condition, wherein the outlet water temperature information includes the actual outlet water temperature and the target outlet water temperature; Determining the current output power of the centrifugal compressor according to the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under the current working conditions, wherein the performance parameters of the centrifugal compressor include the frequency of the centrifugal compressor, the high-low pressure ratio of the centrifugal compressor and the opening of the guide vane, and the operating parameters of the heat exchanger include the pressure of the heat exchanger and the enthalpy difference of the heat exchanger; When the difference between the current output power and the target output power is less than or equal to a preset threshold, the operation of the centrifugal compressor is controlled according to the performance parameters of the centrifugal compressor corresponding to the current output power.

2. The control method according to claim 1, characterized in that: Determining the target output power of the centrifugal compressor according to the outlet water temperature information of the heat exchanger under the current working condition includes: Determine, based on the outlet water temperature information, an actual error between the actual outlet water temperature of the heat exchanger and the target outlet water temperature under the current working condition, and an actual error change rate within a preset sampling time; Determining the standard error and the standard error change rate according to the actual error, the actual error change rate and a preset standard domain; Determining a non-zero membership according to the standard error, the standard error change rate and a preset membership function; The membership value is determined according to the standard error, the standard error change rate and a preset fuzzy rule table.

3. The control method according to claim 2, characterized in that: The centrifugal compressor includes a capacity scheduler, which is provided with an initial energy adjustment parameter, an initial domain and a membership function. The target output power of the centrifugal compressor is determined according to the outlet water temperature of the heat exchanger under the current working condition, including: Determining a standard gain amount corresponding to the initial adjustable parameter according to the non-zero membership degree and the membership value; Determining an actual gain corresponding to the initial adjustable parameter according to the initial domain and the standard gain; Update the initial energy-adjustable parameter according to the actual gain to obtain the current energy-adjustable parameter under the current working condition; The target output power of the centrifugal compressor is determined according to the current adjustable parameters.

4. The control method according to claim 1, characterized in that: Determining the current output power of the centrifugal compressor according to the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under the current working conditions includes: Obtaining the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under current working conditions; Determining the mass flow rate at the inlet of the centrifugal compressor according to the performance parameters of the centrifugal compressor and a preset centrifugal compressor performance model; The current output power of the centrifugal compressor is determined according to the mass flow rate at the inlet of the centrifugal compressor, the evaporation pressure of the heat exchanger and the refrigerant enthalpy difference between the inlet and outlet of the heat exchanger.

5. The control method according to claim 1, characterized in that: The centrifugal compressor includes a solver, the solver is provided with a preset threshold, and the control method includes: When the difference between the current output power and the target output power is greater than the preset threshold, the centrifugal compressor is controlled to update the performance parameters of the centrifugal compressor.

6. The control method according to claim 5, characterized in that: The solver is provided with the surge frequency of the centrifugal compressor, the blocking frequency of the centrifugal compressor and the opening range value of the guide vane, and determines the performance parameter of the centrifugal compressor corresponding to the current output power, including: controlling the frequency of the centrifugal compressor to be greater than a current surge frequency of the centrifugal compressor; Controlling the frequency of the centrifugal compressor to be less than or equal to the blocking frequency of the centrifugal compressor; Controlling the frequency change rate of the centrifugal compressor to be within a preset frequency change rate range; The opening of the guide vane is controlled to be within a preset opening range of the guide vane, and the opening change rate of the guide vane is controlled to be within a preset change rate range.

7. The control method according to claim 6, characterized in that: The surge frequency of the centrifugal compressor includes an original value of the surge frequency of the centrifugal compressor and a correction value of the surge frequency of the centrifugal compressor, and the frequency of controlling the centrifugal compressor is greater than the current surge frequency of the centrifugal compressor, including: Collecting the operating parameters of the centrifugal compressor at a preset frequency within a preset period of time, wherein the operating parameters include the current, suction and exhaust pressure, and suction and exhaust temperature of the centrifugal compressor; Calculating a surge risk index of the centrifugal compressor according to operating parameters of the centrifugal compressor; When the surge risk index of the centrifugal compressor is greater than a preset index, the frequency, pressure ratio and opening of the guide vane of the centrifugal compressor are recorded, and the frequency of the centrifugal compressor is gradually increased according to a preset frequency segment, so that when the surge risk index of the centrifugal compressor is less than the preset index, the increased frequency value of the centrifugal compressor is obtained to determine the surge frequency correction value of the centrifugal compressor; The current surge frequency of the centrifugal compressor is determined according to the surge frequency correction value of the centrifugal compressor and the surge frequency original value of the centrifugal compressor.

8. A control device, characterized in that: include: A processor, and a memory, wherein the memory stores a computer program, and when the computer program is executed by the processor, the steps of the control method according to any one of claims 1 to 7 are implemented.

9. A centrifugal compressor, characterized in that: It comprises the control device and guide vane as claimed in claim 8, wherein the control device is electrically connected to the guide vane.

10. A centrifugal refrigeration unit, characterized in that: Includes the centrifugal compressor as described in claim 9.

11. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the control method according to any one of claims 1 to 7 are implemented.

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