Control methods, centrifugal compressors, refrigeration units, control devices and media

Abstract

This invention discloses a control method, a centrifugal compressor, a refrigeration unit, a control device, and a medium. The centrifugal refrigeration unit includes a centrifugal compressor and a heat exchanger. The centrifugal compressor includes guide vanes. The control method includes determining the target output power of the centrifugal compressor based on the outlet water temperature information of the heat exchanger under current operating conditions; determining the current output power of the centrifugal compressor based on the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under current operating conditions; and controlling the operation of the centrifugal compressor based on the performance parameters of the centrifugal compressor 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 a preset threshold. This reduces surge frequency, outlet water temperature overshoot and settling time, and widens the operating range of the centrifugal compressor, thus reducing frequent start-stop cycles of the refrigeration system.

Description

Technical Field

[0001] This invention relates to the field of compressor technology, and more specifically, to a control method, a centrifugal compressor, a centrifugal refrigeration unit, a control device, and a computer-readable storage medium. Background Technology

[0002] In related technologies, the control logic used in the centrifugal compressor of existing centrifugal water-cooled units results in a small adjustable range of surge frequency curve and blocking frequency curve. This makes it easy for the centrifugal compressor to reach the surge frequency or blocking frequency boundary and fail to effectively perform load increase or decrease. This leads to a large overshoot of the centrifugal compressor's outlet water temperature, a long adjustment time, frequent start-stop, and low energy efficiency in some load areas. Summary of the Invention

[0003] The control method, centrifugal compressor, centrifugal refrigeration unit, control device, and computer-readable storage medium provided by the embodiments of the present invention can solve the problems of large outlet water temperature overshoot, long adjustment time, frequent start-stop, and low energy efficiency in some load areas of centrifugal compressors.

[0004] The control method of this invention is used in a centrifugal refrigeration unit. The centrifugal refrigeration unit includes a centrifugal compressor and a heat exchanger, the centrifugal compressor includes guide vanes, and the control method includes:

[0005] Based on the outlet water temperature information of the heat exchanger under the current operating conditions, determine the target output power of the centrifugal compressor;

[0006] Based on the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under the current operating conditions, the current output power of the centrifugal compressor is determined. 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 degree of the guide vanes. The operating parameters of the heat exchanger include the pressure of the heat exchanger and the enthalpy difference of the heat exchanger.

[0007] If 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 based on the outlet water temperature of the heat exchanger, and determining the optimal combination of compressor frequency and guide vane opening based on the target output power, the 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-stop of the refrigeration system caused by insufficient unloading capacity due to excessively high surge frequency protection can be reduced.

[0009] In some embodiments, determining the target output power of the centrifugal compressor based on the outlet water temperature information of the heat exchanger under current operating conditions includes:

[0010] Based on the outlet water temperature information, determine the actual error between the actual outlet water temperature and the target outlet water temperature of the heat exchanger under the current operating conditions, as well as the actual error change rate within the preset sampling time.

[0011] Based on the actual error, the rate of change of the actual error, and the preset standard universe of discourse, the standard error and the rate of change of the standard error are determined.

[0012] The non-zero membership degree is determined based on the standard error, the rate of change of the standard error, and the preset membership function;

[0013] The membership value is determined based on the standard error, the rate of change of the standard error, and the preset fuzzy rule table.

[0014] Thus, by obtaining the error and rate of change between the actual outlet water temperature and the target outlet water temperature of the heat exchanger under the previous operating conditions, the non-zero membership degree and membership value can be calculated, which can lay the groundwork for calculating the absolute power of the centrifugal compressor under the current operating conditions.

[0015] In some embodiments, the centrifugal compressor includes a capacity scheduler, which has initial capacity adjustment parameters, an initial universe of discourse, and a membership function. Determining the target output power of the centrifugal compressor based on the outlet water temperature of the heat exchanger under current operating conditions includes:

[0016] Based on the non-zero membership degree and the membership value, determine the standard gain corresponding to the initial tunable parameter;

[0017] Based on the initial universe of discourse and the standard gain, determine the actual gain corresponding to the initial tunable parameter;

[0018] The initial adjustable parameters are updated based on the actual gain to obtain the current adjustable parameters under the current operating conditions.

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

[0020] Thus, based on the non-zero membership degree, membership value, and initial universe of discourse, the actual gain corresponding to the initial adjustable parameters can be determined, and the output power of the adapted centrifugal compressor under the current operating conditions can be obtained based on the actual gain.

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

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

[0023] Based on the performance parameters of the centrifugal compressor and the preset centrifugal compressor performance model, determine the mass flow rate at the inlet of the centrifugal compressor;

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

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

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

[0027] If 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 its performance parameters.

[0028] Thus, if 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 current performance of the centrifugal compressor cannot meet the target requirements, thereby enabling timely adjustment of the centrifugal compressor's performance parameters to correct and broaden the operating range.

[0029] In some embodiments, the solver includes the surge frequency of the centrifugal compressor, the blocking frequency of the centrifugal compressor, and the opening range of the guide vanes to determine the performance parameters of the centrifugal compressor corresponding to the current output power, including:

[0030] The frequency of the centrifugal compressor is controlled to be greater than the current surge frequency of the centrifugal compressor;

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

[0032] The frequency change rate of the centrifugal compressor is controlled within a preset frequency change rate range;

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

[0034] Thus, while meeting the target power output, by setting the frequency of the centrifugal compressor between its surge frequency and its blocking frequency, and setting the guide vane opening within a preset range, the centrifugal compressor can operate with the optimal combination of frequency and guide vane opening. This avoids frequent start-stop cycles and improves the energy efficiency of the centrifugal compressor.

[0035] In some embodiments, the surge frequency of the centrifugal compressor includes the original value of the surge frequency of the centrifugal compressor and the corrected value of the surge frequency of the centrifugal compressor. Determining the performance parameters of the centrifugal compressor corresponding to the current output power includes:

[0036] The operating parameters of the centrifugal compressor are collected at a preset frequency within a preset time period. The operating parameters include the current, suction and discharge pressure, and suction and discharge temperature of the centrifugal compressor.

[0037] Calculate the surge risk index of the centrifugal compressor based on its operating parameters;

[0038] When the surge risk index of the centrifugal compressor is greater than the preset index, the frequency, pressure ratio and guide vane opening of the centrifugal compressor are recorded. The frequency of the centrifugal compressor is gradually increased according to the preset frequency range until the surge risk index of the centrifugal compressor is less than the preset index. The increased frequency value of the centrifugal compressor is then obtained to determine the surge frequency correction value of the centrifugal compressor.

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

[0040] In this way, by collecting the operating parameters of the centrifugal compressor, the surge risk index of the centrifugal compressor can be calculated, and the surge risk index of the centrifugal compressor can be compared with the preset index to determine the surge frequency correction value, thereby improving the range between the surge frequency and the blocking frequency of the centrifugal compressor.

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

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

[0043] The centrifugal refrigeration unit of the present invention includes the centrifugal compressor described in any of the above embodiments.

[0044] The non-volatile computer-readable storage medium containing a computer program according to embodiments of the present invention includes a computer program that, when executed by a processor, causes the processor to perform the control method described in any of the above embodiments.

[0045] Additional aspects and advantages of embodiments of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of embodiments of the invention. Attached Figure Description

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

[0047] Figure 1 This is a flowchart illustrating the control method of some embodiments of the present invention;

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

[0049] Figure 3 This is a schematic diagram of the control device according to certain embodiments of the present invention;

[0050] Figure 4 This is a flowchart illustrating the control method of some embodiments of the present invention;

[0051] Figure 5 This is a flowchart illustrating the control method of some embodiments of the present invention;

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

[0053] Figure 7 This is a flowchart illustrating the control method of some embodiments of the present invention;

[0054] Figure 8 This is a flowchart illustrating the control method of some embodiments of the present invention;

[0055] Figure 9 This is a flowchart illustrating the control method of some embodiments of the present invention;

[0056] Figure 10This is a flowchart illustrating the control method of some embodiments of the present invention;

[0057] Figure 11 This is a schematic diagram illustrating the connection state of a computer-readable storage medium and a processor according to certain embodiments of the present invention.

[0058] Explanation of icon 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 Implementation

[0060] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. 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 should not be construed as limiting the embodiments of the present invention.

[0061] Please see Figure 1 , Figure 2 and Figure 3 The control method of this invention is used in 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 guide vanes 11. The control method includes:

[0062] Step 011: Based on the outlet water temperature information of the heat exchanger 20 under the current operating conditions, determine the target output power of the centrifugal compressor 10. The outlet water temperature information includes the actual outlet water temperature and the target outlet water temperature.

[0063] Step 012: Based on the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current operating conditions, determine the current output power of the centrifugal compressor 10. 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 degree of the guide vane 11. 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, control the operation of the centrifugal compressor 10 according to the performance parameters of the centrifugal compressor 10 corresponding to the current output power.

[0065] Thus, by determining the target output power of the compressor based on the outlet water temperature of the heat exchanger 20, and determining the optimal combination of compressor frequency and guide vane 11 opening based on the target output power, the adjustable response speed of the centrifugal compressor 10 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 10 can be effectively widened, and the frequent start-stop of the refrigeration system caused by insufficient unloading capacity due to excessively high surge frequency protection can be reduced.

[0066] The centrifugal chiller unit 100 can be a single-stage or two-stage centrifugal chiller unit 100 equipped with a flash tank or plate heat exchanger, capable of providing low-temperature chilled water through a refrigeration cycle to meet various refrigeration needs. This application uses a two-stage centrifugal chiller unit 100 as an example. The centrifugal chiller unit 100 includes a centrifugal compressor 10 and a heat exchanger 20. The centrifugal compressor 10 provides the power to move the refrigerant gas through centrifugal force, and the refrigerant gas exchanges heat as it passes through the heat exchanger 20, thereby realizing a refrigeration cycle. The heat exchanger 20 can be an evaporator or a condenser; in this application, an evaporator is used as an example.

[0067] The centrifugal compressor 10 includes a control device and guide vanes 11. 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. The computer program 143 includes instructions for executing control methods. The guide vanes 11 are disposed between the heat exchanger 20 and the centrifugal compressor 10. The guide vanes 11 can drive the refrigerant gas to rotate at high speed, generating centrifugal force in the refrigerant gas, thereby compressing the refrigerant gas and increasing its pressure and flow rate, as well as assisting in regulating the refrigerant flow rate.

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

[0069] The processor 141 can determine the current output power of the centrifugal compressor 10 based on the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current operating conditions. The performance parameters of the centrifugal compressor 10 include its frequency, high-low pressure ratio, and guide vane 11 opening. The operating parameters of the heat exchanger 20 include its pressure and enthalpy difference. It should be noted that the frequency of the centrifugal compressor 10 can be the rotational frequency of the rotating shaft; the high-low pressure ratio can be the ratio of the outlet pressure to the inlet pressure; the guide vane 11 opening can be the difference between the rotation angle of the guide vane 11 on the inlet side and the rotation angle of the guide vane 11 on the exhaust side; the pressure of the heat exchanger 20 can be the pressure at which the refrigerant vaporizes in the evaporator; and the enthalpy difference of the heat exchanger 20 can be the difference between the enthalpy of the refrigerant at the evaporator inlet and the enthalpy of the refrigerant at the evaporator outlet. 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. By combining the refrigerant mass flow rate with the operating parameters of the heat exchanger 20, the processor 141 can obtain the current output power of the centrifugal compressor 10 under the current operating conditions.

[0070] The processor 141 compares the target output power of the centrifugal compressor 10 with its current output power under current operating conditions. If the difference between the current output power and the target output power is less than or equal to a preset threshold, the processor 141 controls the operation of the centrifugal compressor 10 based on its performance parameters corresponding to the current output power. The memory 142 stores a preset threshold value, which measures whether the current output power of the centrifugal compressor 10 meets the cooling requirements of the centrifugal refrigeration unit 100. This preset threshold value can be 1%, 2%, 5%, etc., of the rated power. For example, with a preset threshold of 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. Furthermore, based on the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current operating conditions, the processor 141 can calculate that the current output power is 81% of the rated power. Thus, 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] Please see Figure 4 In some implementations, step 011: determining the target output power of the centrifugal compressor 10 based on the outlet water temperature information of the heat exchanger 20 under the current operating conditions, including:

[0072] Step 0111: Based on the outlet water temperature information, determine the actual error between the actual outlet water temperature of the heat exchanger 20 and the target outlet water temperature under the current operating conditions, as well as the actual error change rate within the preset sampling time.

[0073] Step 0112: Determine the standard error and the standard error rate of change based on the actual error, the actual error rate of change, and the preset standard universe of discourse;

[0074] Step 0113: Determine the non-zero membership degree based on the standard error, the rate of change of standard error, and the preset membership function;

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

[0076] Thus, by obtaining the error and error rate of change between the actual outlet water temperature and the target outlet water temperature of the heat exchanger 20 under the previous operating conditions, the non-zero membership degree and membership value can be calculated, which can lay the groundwork for calculating the absolute power of the centrifugal compressor 10 under the current operating conditions.

[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 and the target outlet water temperature of the heat exchanger 20 under the current operating conditions, as well as the rate of change of the error within a 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 collected outlet water temperature with the target outlet water temperature preset in the memory 142. This allows the processor 141 to obtain the error between the actual outlet water temperature and the target outlet water temperature of the heat exchanger 20 under the current operating conditions, and to determine the rate of change of the error by comparing the error obtained from each sampling time.

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

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

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

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

[0082] Wherein, the ranges of the actual error e and the rate of change of error ec are respectively [e min e max ] and [ec min , ec max The standard universe of discourse is [-6, 6], and the standard error is e. , The standard error change rate is ec , .

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

[0084] The processor 141, based on the acquired standard error, standard error rate of change, and a fuzzy rule table preset in the memory 142, can determine the membership values ​​corresponding to the standard error and standard error rate of change. In the fuzzy proportional-integral-derivative (PID) control system, the fuzzy rule table can determine the adjustment amounts of the proportional, integral, and derivative gains of the PID controller based on the error and the rate of change of the error. That is, the fuzzy rules include adjustment strategies for the proportional, integral, and derivative gains corresponding to different combinations of standard errors and standard error rates of change, and these adjustment strategies can be increasing, decreasing, or remaining unchanged. The processor 141 can obtain the corresponding membership value for each combination of standard error and standard error rate of change by searching the fuzzy rule table.

[0085] Please see Figure 5 and Figure 6 In some embodiments, the centrifugal compressor 10 includes a capacity scheduler 12, which has initial capacity adjustment parameters, an initial universe of discourse, and a membership function. Step 011: Determine the target output power of the centrifugal compressor 10 based on the outlet water temperature of the heat exchanger 20 under the current operating conditions, including:

[0086] Step 0115: Determine the standard gain corresponding to the initial tunable parameters based on the non-zero membership degree and membership value;

[0087] Step 0116: Determine the actual gain corresponding to the initial tunable parameters based on the initial universe of discourse and the standard gain.

[0088] Step 0117: Update the initial adjustable parameters according to the actual gain to obtain the current adjustable parameters under the current operating conditions;

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

[0090] Thus, based on the non-zero membership degree, membership value, and initial universe of discourse, the actual gain corresponding to the initial adjustable parameters can be determined, and the output power of the adapted centrifugal compressor 10 under the current operating conditions can be obtained based on the actual gain.

[0091] Specifically, the centrifugal compressor 10 includes a capacity scheduler 12, which can be installed in the control device 14. The capacity scheduler 12 includes initial adjustable parameters, an initial universe of discourse, and a membership function. The initial adjustable parameters can be initial proportional, integral, and derivative parameters; for example, they can be represented as kp, ki, and kd. In a fuzzy control system, the initial universe of discourse can define the entire range of values ​​that the input or output variables can take; the membership function defines the degree of membership of each fuzzy set.

[0092] After obtaining the non-zero membership degrees and membership values, processor 141 can obtain the standard gain corresponding to the initial tunable parameters by performing a weighted summation of the membership function. The weights for the weighted summation of the membership function are the specific values ​​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, processor 141 maps the standard gain quantities to the initial universe of discourse, thereby determining the actual gain quantities corresponding to the initial tunable parameters; for example, processor 141 can convert the standard gain quantities into actual gain quantities by using an appropriate scaling factor to map the standard gain quantities to the initial universe of discourse. For example, the actual gain quantities corresponding to the standard gain quantities δkp', δki', and δkd' can be δkp, δki, and δkd.

[0094] Next, the processor 141 can update the initial adjustable parameters based on the acquired actual gain, thereby obtaining the current adjustable parameters under the current operating condition. The current adjustable parameters can be obtained by adding the actual gain to the initial adjustable parameters. For example, the updated adjustment 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 based on the current adjustable parameters. For example, the processor 141 can determine the target output power of the centrifugal compressor 10 based on the temperature difference between the current outlet water temperature of the heat exchanger 20 and the target outlet water temperature, and calculate the proportional, integral, and derivative values ​​of the temperature difference.

[0096] Please see Figure 7 In some embodiments, step 012: determining the current output power of the centrifugal compressor 10 based on the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current operating conditions, including:

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

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

[0099] Step 0123: Determine the current output power of the centrifugal compressor 10 based on 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 at the inlet and outlet of the heat exchanger 20.

[0100] Thus, by acquiring the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20, and inputting the parameters into the 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 acquire the performance parameters of the centrifugal compressor 10 and the operating parameters of the heat exchanger 20 under the current operating conditions. The performance parameters of the centrifugal compressor 10 include its frequency, high-low pressure ratio, and guide vane 11 opening. The operating parameters of the heat exchanger 20 include its pressure and enthalpy difference. It should be noted that the frequency of the centrifugal compressor 10 can be the rotational frequency of the rotating shaft; the high-low pressure ratio can be the ratio of the outlet pressure to the inlet pressure; the guide vane 11 opening can be the difference between the angle of the guide vane 11 on the inlet side 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; and the enthalpy difference of the heat exchanger 20 can be the difference between the enthalpy of the refrigerant at the evaporator inlet and the enthalpy of the refrigerant at the evaporator outlet. 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 based on the performance parameters and the performance model of the centrifugal compressor 10 preset in the memory 142.

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

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

[0104] Where Demand represents the current output power of centrifugal compressor 10; P eε represents the pressure of heat exchanger 20; ε represents the high-low pressure ratio of the centrifugal compressor; ω represents the frequency of the centrifugal compressor; D1 represents the opening degree of the guide vanes; W1 is the first-layer weight coefficient matrix of shape i×4, b1 is the first-layer bias coefficient matrix of shape i×1, W2 is the second-layer weight coefficient matrix of shape j×i, b2 is the second-layer bias coefficient matrix of shape j×1, and the first-layer activation function... Second-level activation function The network parameter matrix vectors W1, W2, b1, b2 can be obtained by fitting the data from the actual four-dimensional mapping table using the backpropagation (BP) method. Based on the motor energy consumption test data, the energy consumption characteristic function g(ε,ω) of the compressor inverter can be obtained by fitting a polynomial empirical formula.

[0105] The processor 141 calculates the current output power of the centrifugal compressor 10 under the current operating conditions by combining the refrigerant mass flow rate with the operating parameters of the heat exchanger 20.

[0106] Please see Figure 6 and Figure 8 In some embodiments, the centrifugal compressor 10 includes a solver 13, which has a preset threshold, and the control method includes:

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

[0108] Thus, if 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 a preset threshold, it indicates that the current performance of the centrifugal compressor 10 cannot meet the target requirements, thereby enabling timely adjustment of the performance parameters of the centrifugal compressor 10 to reduce the occurrence of compressor surge.

[0109] Specifically, the centrifugal compressor 10 includes a solver 13, which can solve for the optimal performance parameters of the centrifugal compressor 10 given its current output power. The solver 13 has a preset threshold, which can be an adjustable dead zone value. In a control system, the adjustable dead zone value refers to the range of input signals within which the output is zero in the transfer function of the control system. Within this range, even if the input signal changes, the output of the control system will not change noticeably. Therefore, the adjustable dead zone value can reduce the response of the centrifugal compressor 10 to small signal fluctuations, thereby reducing the frequency of frequency adjustments and energy consumption of the centrifugal compressor 10, i.e., avoiding small-range and high-frequency fluctuations in the current output power of the centrifugal compressor 10, thus improving the stability of the centrifugal compressor 10.

[0110] If 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 its performance parameters. For example, if the target output power is denoted as Demandi and the current output power is denoted as 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 remain unchanged; when |Demandi-Demando|>Δ, it indicates that the current output power of the centrifugal compressor 10 cannot meet the target output power, and the frequency of the centrifugal compressor 10 and the opening of the guide vane 11 need to be recalculated.

[0111] Please see Figure 9 In some embodiments, the solver 13 includes 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. Step 013: Determine the performance parameters of the centrifugal compressor 10 corresponding to the current output power, including:

[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 within the preset frequency change rate range;

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

[0116] Thus, while meeting the target power output, by setting the frequency of the centrifugal compressor 10 between the surge frequency and the blocking frequency of the centrifugal compressor 10, and setting the opening of the guide vane 11 within a preset opening range, the centrifugal compressor 10 can operate with the optimal combination of frequency and opening of the guide vane 11. This avoids frequent start-stop of the centrifugal compressor 10 and improves its energy efficiency. It should be noted that the optimal combination of frequency and opening of the guide vane 11 refers to the combination that enables the centrifugal compressor to operate at its best efficiency.

[0117] Specifically, the solver 13 includes the surge frequency of the centrifugal compressor 10, the blocking frequency of the centrifugal compressor 10, and the opening range of the guide vane 11. The surge frequency of the centrifugal compressor 10 refers to the frequency of vibration or pressure pulsation of the centrifugal compressor 10 under surge conditions. The blocking frequency of the centrifugal compressor 10 can be the frequency at which the centrifugal compressor 10 reaches its maximum flow rate, at which point the centrifugal compressor 10 cannot further increase the flow rate, thus exhibiting a blocking phenomenon. The opening range of the guide vane 11 can be the maximum and minimum values ​​that the guide vane 11 can achieve.

[0118] When the solver 13 solves for the optimal combination of performance parameters of the centrifugal compressor 10 based on the current output power, it needs to control the frequency of the centrifugal compressor 10 obtained from the solution to be greater than the surge frequency of the centrifugal compressor 10 under the current operating conditions, so as to avoid the centrifugal compressor 10 from experiencing surge.

[0119] The frequency of the centrifugal compressor 10, which has been solved, 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 0-15Hz / s, so the frequency change rate of the centrifugal compressor can be any value between 1Hz / s, 2Hz / s, 3Hz / s, 4Hz / s, 5Hz / s, or 0-15Hz / s.

[0121] The solved opening of guide vane 11 needs to be controlled within a preset opening range to prevent the opening of guide vane 11 from failing to reach the target opening. Furthermore, the solver 13 needs to consider the limitation of the maximum rate of change of guide vane 11. For example, if the maximum rate of change of guide vane 11 is 5% per second, the optimal solution among the solutions for the target opening of guide vane 11 obtained by the solver 13 is the one that minimizes the time required for the current opening of guide vane 11 to reach the target opening using the maximum rate of change of guide vane 11.

[0122] Please see Figure 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: Collect the operating parameters of the centrifugal compressor 10 at a preset frequency within a preset time period. The operating parameters include the current, suction and discharge pressure, and suction and discharge temperature of the centrifugal compressor 10.

[0124] Step 01312: Calculate the surge risk index of the centrifugal compressor 10 based on its operating parameters;

[0125] Step 01313: When the surge risk index of the centrifugal compressor 10 is greater than the preset index, record the frequency, pressure ratio and guide vane 11 opening of the centrifugal compressor 10, and gradually increase the frequency of the centrifugal compressor 10 according to the preset frequency range until the surge risk index of the centrifugal compressor 10 is less than the preset index. Then obtain the increased frequency value of the centrifugal compressor 10 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 based on the surge frequency correction value and the original surge frequency value of the centrifugal compressor 10;

[0127] In this way, by collecting the operating parameters of the centrifugal compressor 10, the surge risk index of the centrifugal compressor 10 is calculated, and the surge risk index of the centrifugal compressor 10 is compared with the preset index to determine the surge frequency correction value, thereby improving the range between the surge frequency and the blockage frequency of the centrifugal compressor 10.

[0128] Specifically, the surge frequency of the centrifugal compressor 10 includes the original surge frequency value and the corrected surge frequency value. The original surge frequency value can be represented as the frequency of natural surge phenomena occurring in the centrifugal compressor 10 under no external interference or control measures. This original value is derived from an empirically fitted curve obtained from a prototype in the laboratory. However, each machine will differ, and the actual surge frequency for each operating condition will also vary. Therefore, this algorithm aims to perform differentiated corrections for each device. The corrected surge frequency value can be the change or adjusted value of the surge frequency after implementing certain anti-surge control measures.

[0129] Since surge is affected by a variety of factors, such as the structural characteristics of the centrifugal compressor 10, flow rate changes, pipeline resistance, and speed, the surge frequency is not a fixed value but changes with the operating conditions. Therefore, to avoid surge, the centrifugal compressor 10 needs to consider both the original surge frequency value and the corrected surge frequency value.

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

[0131] The processor 141 calculates the surge risk index of the centrifugal compressor 10 based on its operating parameters. Specifically, the processor 141 continuously calculates the fluctuation indices of various signals within a preset time period, and weights these indices to calculate the surge risk index. For example, after acquiring the collected operating parameters of the centrifugal compressor 10, the processor 141 performs data filtering and standardization, then performs a difference calculation. If the first derivative does not change sign, a second difference calculation is performed. It should be noted that the purpose of the second difference calculation is to determine the number of fluctuations to calculate the surge risk index. Then, it determines whether the surge risk index of the centrifugal compressor 10 is greater than a preset index. If it is determined to exceed the preset index, the processor acquires the operating parameters of the centrifugal compressor 10 again within the next preset time period, calculates the surge factor of the current characteristic sensing parameter based on the signal fluctuation indices within the preset time period, and weights the surge factor to determine 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, a surge determination is performed again.

[0132] Furthermore, if the surge risk index of the centrifugal compressor 10 is greater than the preset index, it can be determined that the centrifugal compressor 10 has entered the surge zone. The processor 141 can control the memory 142 to record the frequency, pressure ratio and guide vane 11 opening of the centrifugal compressor 10 at this time, and gradually increase the frequency of the centrifugal compressor 10 according to the frequency range preset in the memory 142, and repeatedly calculate the surge risk index of the centrifugal compressor 10 during the increase.

[0133] When the frequency of the centrifugal compressor 10 is increased to make the surge risk index of the centrifugal compressor 10 less than the preset index, the increased frequency value of the centrifugal compressor 10 at this time 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 updates the current surge frequency of the centrifugal compressor 10 based on the surge frequency correction value and the original surge frequency value of the centrifugal compressor 10. Finally, the processor 141 determines the performance parameters of the centrifugal compressor 10 based on the updated current surge frequency, thus preventing surge from occurring even when the frequency of the centrifugal compressor 10 is higher than the updated current surge frequency.

[0135] Please see Figure 11 The present invention also provides a computer-readable storage medium 200 storing a computer program 143. When the computer program 143 is executed by the processor 141, the steps of the control method of any of the above embodiments are implemented. For the sake of brevity, they will not be described in detail here.

[0136] In the description of this specification, the references to terms such as "some embodiments," "in one example," and "exemplarily" indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0137] Any process or method description in the flowchart or otherwise herein can be understood as representing a module, segment, or portion of code comprising one or more executable instructions for implementing a particular logical function or process, and the scope of the preferred embodiments of the invention includes additional implementations in which functions may be performed not in the order shown or discussed, including substantially simultaneously or in reverse order depending on the functions involved, as will be understood by those skilled in the art to which embodiments of the invention pertain.

[0138] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to 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 guide vanes, and the control method includes: Based on the outlet water temperature information of the heat exchanger under the current operating conditions, the target output power of the centrifugal compressor is determined. The outlet water temperature information includes the actual outlet water temperature and the target outlet water temperature. Based on the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under the current operating conditions, the current output power of the centrifugal compressor is determined. 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 degree of the guide vanes. The operating parameters of the heat exchanger include the pressure of the heat exchanger and the enthalpy difference of the heat exchanger. If 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. The step of determining the target output power of the centrifugal compressor based on the outlet water temperature information of the heat exchanger under the current operating conditions includes: Based on the outlet water temperature information, determine the actual error between the actual outlet water temperature and the target outlet water temperature of the heat exchanger under the current operating conditions, as well as the actual error change rate within the preset sampling time. Based on the actual error, the rate of change of the actual error, and the preset standard universe of discourse, the standard error and the rate of change of the standard error are determined. The non-zero membership degree is determined based on the standard error, the rate of change of the standard error, and the preset membership function; The membership value is determined based on the standard error, the rate of change of the standard error, and the preset fuzzy rule table.

2. The control method according to claim 1, characterized in that, The centrifugal compressor includes a capacity scheduler, which has initial adjustable parameters, an initial universe of discourse, and a membership function. Determining the target output power of the centrifugal compressor based on the outlet water temperature of the heat exchanger under current operating conditions includes: Based on the non-zero membership degree and the membership value, determine the standard gain corresponding to the initial tunable parameter; Based on the initial universe of discourse and the standard gain, determine the actual gain corresponding to the initial tunable parameter; The initial adjustable parameters are updated based on the actual gain to obtain the current adjustable parameters under the current operating conditions. The target output power of the centrifugal compressor is determined based on the current adjustable parameters.

3. The control method according to claim 1, characterized in that, Determining the current output power of the centrifugal compressor based on its performance parameters and the operating parameters of the heat exchanger under current operating conditions includes: Obtain the performance parameters of the centrifugal compressor and the operating parameters of the heat exchanger under the current operating conditions; Based on the performance parameters of the centrifugal compressor and the preset centrifugal compressor performance model, determine the mass flow rate at the inlet of the centrifugal compressor; The current output power of the centrifugal compressor is determined based on the mass flow rate at the inlet of the centrifugal compressor, the evaporation pressure of the heat exchanger, and the refrigerant enthalpy difference at the inlet and outlet of the heat exchanger.

4. The control method according to claim 1, characterized in that, The centrifugal compressor includes a solver, the solver has a preset threshold, and the control method includes: If 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 its performance parameters.

5. The control method according to claim 4, characterized in that, The solver, equipped with the surge frequency, blocking frequency, and guide vane opening range of the centrifugal compressor, determines the performance parameters of the centrifugal compressor corresponding to the current output power, including: The frequency of the centrifugal compressor is controlled to be greater than the current surge frequency of the centrifugal compressor; The frequency of the centrifugal compressor is controlled to be less than or equal to the blocking frequency of the centrifugal compressor; The frequency change rate of the centrifugal compressor is controlled within a preset frequency change rate range; The opening degree of the guide vane is controlled to be within a preset opening degree range, and the rate of change of the opening degree of the guide vane is controlled to be within a preset rate of change range.

6. The control method according to claim 5, characterized in that, The surge frequency of the centrifugal compressor includes the original surge frequency value and the corrected surge frequency value of the centrifugal compressor. Controlling the frequency of the centrifugal compressor to be greater than the current surge frequency of the centrifugal compressor includes: The operating parameters of the centrifugal compressor are collected at a preset frequency within a preset time period. The operating parameters include the current, suction and discharge pressure, and suction and discharge temperature of the centrifugal compressor. Calculate the surge risk index of the centrifugal compressor based on its operating parameters; When the surge risk index of the centrifugal compressor is greater than the preset index, the frequency, pressure ratio and guide vane opening of the centrifugal compressor are recorded. The frequency of the centrifugal compressor is gradually increased according to the preset frequency range until the surge risk index of the centrifugal compressor is less than the preset index. The increased frequency value of the centrifugal compressor is then obtained to determine the surge frequency correction value of the centrifugal compressor. The current surge frequency of the centrifugal compressor is determined based on the surge frequency correction value and the original surge frequency value of the centrifugal compressor.

7. A control device, characterized in that, include: A processor and a memory, wherein the memory stores a computer program that, when executed by the processor, implements the steps of the control method according to any one of claims 1 to 6.

8. A centrifugal compressor, characterized in that, It includes the control device and guide vane as described in claim 7, wherein the control device is electrically connected to the guide vane.

9. A centrifugal refrigeration unit, characterized in that, Includes the centrifugal compressor as described in claim 8.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by a processor, it implements the steps of the control method according to any one of claims 1-6.

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